Automotive Stirling Engine Development Program.19800072709_1980072709

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DOE/NASA/0032-79/5

NASA CR-159744

MTI 79ASE101QT6

(HftSA-CR-159744) AUTOMOTIVE STIRLING EHGINE H80-72800DEVELOPMENT PROGRAM Quarterly Technical

Progress Report, 1 Jul. - 30 Sep. 1979(Mechanical Technology, Inc.) 165 p OnclasCSCL 10B 00/85 47U95

AUTOMOTIVE STIRLING ENGINE

DEVELOPMENT PROGRAM

QUARTERLY TECHNICAL PROGRESS REPORT

FOR PERIOD: JULY 1 — SEPTEMBER 30, 1979

Mechanical Technology Incorporated

January 1980

Prepared forNATIONAL AERONAUTICS AND SPACE ADMINISTRATION

Lewis Research CenterUnder Contract DEN 3-32

forU.S. DEPARTMENT OF ENERGYConservation and Solar Applications

Off ice of TransportationPrograms

R E C E I V E DT l F A G I U T Y

A C C E S S D E P T .



NOTICE

This report was prepared to document work sponsored bythe United States Government. Neither the United Statesnor its agent, the United States Department of Energy,nor any Federal em ployees, nor any of their contractors,subcontractors or their employees, makes any warranty,express or implied, or assumes any legal liability or re-sponsibility for the accuracy, completeness, or usefulness

of any information, apparatus, product or process dis-closed, or represents that its use would not infringeprivately owned rights.



DOE/NASA/0032-79/5NASA CR-159744MTI 79ASE101QT6

AUTOMOTIVE STIRLING ENGINE

DEVELOPMENT PROGRAMTECHNICAL PROGRESS REPORTFOR PERIOD: JULY 1 — SEPTEMBER 30, 1979

STIRLING ENGINE SYSTEMS DIVISIONMechanical Technology IncorporatedLatham, New York 12110

January 1980

Prepared forNational Aeronautics and Space AdministrationLewis Research CenterCleveland, OhioUnder Contract DEN 3-32

fo rU.S. DEPARTMENT OF ENERGYConservation and Solar ApplicationsOff ice of Transportation ProgramsWashington, D.C. 20545Under Interagency Agreement EC-77-A-31-1040



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TABLE OF CONTENTS

1.0 SUMMARY 1

2.0 INTRODUCTION 2

3.0 PROGRESS SUMMARIES 7

3.1 Major Task 1 - Reference Engine 8

3.1.1 Task 1.1 Initial Technology Assessment 8

3.1.2 Task 1.2 Reference Engine System Design 8

3.2 Major Task 2 - Component & Subsystem Development 13

3.2.1 Combustion and Heat Transfer Technology Development... 13

3.2.2 Mechanical Component and Drive System Development 48

3.2.3 Auxiliaries Technology Development 50

3.2.4 Controls Technology Development 51

3.2.5 Materials Development 60

3.3 Major Task 3 - Baseline Engine System (P-40) 63

3.3.1 Baseline Engine (P-40) 63

3.3.2 Facilities 70

3.4 Major Task 4 - ASE Mod I System 76

3.4.1 Heat Generating System 76

3.4.2 Preheater 76

3.4.3 Heater Head 78

3.4.4 Gas Cooler 78

3.4.5 Regenerators 78

3.4.6 Cylinder Block 82

3.4.7 Seals 82

3.4.8 Cooling Systems Development 82

3.4.9 Piston/Piston Rod Assembly 84

3.4.10 Engine Drive System 853.4.11 Air/Fuel System 85

3.4.12 Auxiliaries 853.4.13 Flow Distribution Tests 85

3.4.14 Joining Techniques 85

3.4.15 Power Control 85

3.4.16 Air Blower 903.4.17 Atomizer Air Compressor 90

3.4.18 Stirling Engine System 90



TABLE OF CONTENTS (Cont'd.)

Page

3.5 Major Task 5 - ASE Mod II System 101

3.5.1 Endurance Test on P-40 Engine (ASE40-4) 101

3.5.2 Annular Regenerator 106

3.5.3 Seal Development Test Rig No. 1 106

3.6 Major Task 6 - Prototype ASE System Study 115

3.7 Major Task 7 - Computer Program Development 116

3.8 Major Task 8 - Technical Assistance 117

3.9 Major Task 9 - Program Management 118

APPENDIX A., 121



LIST OF FIGURES

Figure Page

FRONTISPIECE Stirling Powered Spirit Baseline Vehicle Under

Test at Michigan International Speedway

2.0-1 Program Milestones 4

2.0-2 Program Task Schedule 5

3.1.2-1 Alternative Piston Rod Seal 10

3.1.2-2 Current Reference Engine Design 11

3.1.2-3 Reference Engine Incorporated Into X-Body Vehicle 12

3.2-1 Preheater Housing 15

3.2-2 Preheater Housing and Adjacent Components 16

3.2-3 Side View of Heater Head Quadrant 17

3.2-4 Top View of Combustor 18

3.2-5 Regenerator 19

3.2-6 Cooler 19

3. 2-7 Combustion Air Blower...., 20

3.2-8 Air Pump 21

3.2-9 Rod Assembly 22

3.2-10 Piston Seal Assembly 23

3.2-11 Gas Seal Housing Cartridges 24

3.2-12 Seal Assemblies 25

3.2-13 Fuel Nozzle 26

3.2-14 Rear View of Engine Exposing Drive Gears 27

3.2-15 Crankcase/Main Shaft 28

3.2-16 Underside of Engine 28

3.2-17 Parallel Crankshaft and Bedplate Assembly - Top View 29

3.2-18 Crankshafts Without Drive Gears 29



LIST OF FIGURES (CONT'D.)

Figure Page

3.2.1.2-1 EGR Schematic.., 31

3.2.1.2-2 CO Levels for EGR Fractions Up to 100% 33

3.2.1.3-1 CGR Schematic 34

3.2.1.3-2 Design Pressure Drop and CGR Pumping at Idle

Conditions 35

3.2.1.3-3 CGR Bypass Valve 37

3.2.1.3-4 NOX vs. Fuel Flow Using CGR 38

3.2.1.4-1 Comparison of EGR and CGR Control Valves 39

3.2.1.4-2 Comparison of NOX Reduction Methods Using

EGR and CGR 40

3.2.1.5-1 Schematic Design of Regenerator Pressure Drop

Test Rig 45

3.2.1.6-1 Heat Flows for P-40 Opel Heating System 47

3.2.2.1-1 Materials Screening Test Rig 49

3.2.3-1 ASE Mod 1 Blower Development Test Rig (Side View) 52

3.2.3-2 Cross Sections of ASE Mod I Blower DevelopmentTest Rig 53

3.2.3-3 Dimensions of Vane Height for the Blower Design 54

3.2.4-1 Electric Actuator 57

3.2.4-2 Electro-Hydraulic Actuator 57

3.2.4-3 Sliding Rod of Hydrogen Power Control Valve 58

3.3.1.1-1 P-40 Stirling Engine No. 8 Installed in the

AMC Spirit Engine 64

3.3.1.1-2 P-40 Spirit 65

3.3.2-1 Skid #1 - Engine Cooling 72

3.3.2-2 Skid #2 - Dynamometer Cooling 72

3.3.2-3 Skid #3 - Engine/Brake Assembly 73

3.3.2-4 Skid #4 - Fuel/Air 73




Figure Page

3.3.2-5 Skid #5 - Operator Control Assembly 75

3.4.1-1 ASE Mod I Combustion Chamber with Varying Heights 77

3.4.3-1 ASE Mod I Regenerator House - Effective Stress

in N/mm2

79

3.4.3-2 ASE Mod I Regenerator House - Effective Stress

in N/mm2

80

3.4.3-3 ASE Mod I Cylinder House - Effective Stress in N/mm2.... 81

3.4.6-1 Initial and Revised Duct Plate 83

3.4.13-1 Air Preheater Flow Distribution Test Rig 86

3.4.13-2 Air Preheater Flow Distribution Test Rig 87

3.4.14-1 Fixture for Brazing the Preheater Matrix 88

3.4.14-2 Brazing Test of Preheater Matrix 89

3.4.16-1 Performance Map of the Flaff Blower 91

3.4.16-2 Performance Map of the Sunflo Blower 92

3.4.16-3 Combustion Air Blower Variator 93

3.4.16-4 Results of Combustion Air Blower Noise Tests 94

3.4.17-1 Atomizer Air Compressor with Servo Oil Pump 95

3.5.1-1 Cracked Manifold 102

3.5.1-2 Enlargement of Cracked Manifold Shown in Previous

Figure 103

3.5.1-3 P-40 Endurance Test Engine 105

3.5.2-1 P-40 with Annular Regenerator-Type Heater,Regenerators Shown 107

3.5.2-2 P-40 with Annular Regenerator-Type Heater,

One Quadrant Removed 108

3.5.2-3 Close-Up View of Annular Regenerator-Type Heater

Mounted on the P-40 Engine 109

3.5.2-4 Annular Regenerator-Type Heater, Underside View of

Quadrant 110




Figure Page

3.5.2-5 Annular Regenerator-Type Heater and P-40 Engine

Mounted on Test Skid Ill

3.5.2-6 Cross Section of Annular Regenerator in the Endurance

Engine (ASE-40-4) as Compared to Cross Section of

Regenerator in a P-40 Engine 112

3.5.3-1 Diaphragm Seal Concept 113

3.5.3-2 Diaphragm Seal Test Rig 114

LIST OF TABLES .

Table Page

3.2.1.4-1 CVS Cycle Comparison 41

3.2.1.4-2 Advantages/Disadvantages of EGR and CGR 42

3.2.1.4-3 Comparison of Mod I Blower Requirements 44

3.2.4-1 Comparison of Selected Alternative Power

Control Sys terns 59

3.3.1.1-1 P-40 Spirit Performance Compared to P-40 Opel

Performance 69

3.4.18-1 Preliminary ASE Mod I Dimensions 96

3.4.18-2 Preliminary Calculated Mod I Values for Power

and Efficiency 97

3.4.18-3 Calculated Net Power and Net Efficiencies of the

Mod I Engine as a Function of Mean Pressure and

Rotational Speed 99

3.4.18-4 Friction and Auxiliary Power Requirements Used to

Perform Net Power Calculations 100



1.0 SUMMARY

The DOE/NASA "Automotive Stirling Engine Development Program" has been

underway for approximately eighteen months.

During this time, the program's first Stirling-powered vehicle was assembled,

tested, delivered, and displayed. This predevelopmental, demonstration vehi-

cle, an Opel sedan with a P-40 Stirling engine, was presented at the October,

1978 DOE Highway Vehicle Systems Contractors' Coordination Meeting. The

program's baseline Stirling-powered vehicle, a 1979 AMC Spirit sedan contain-

ing a P-40 Stirling engine, was displayed for the first time with a mockup

engine at the meeting in April 1979. After the April CCM, the mockup engine

was removed and the "real" engine was installed. The Spirit was then tested

by AMG and changes were made in the installation and the transmission in order

to "optimize" the vehicle/engine system with respect to performance and

emissions. The results of testing the P-40 Spirit are contained in this

report. As of the end of this quarterly period, the engine in the P-40 Spirit

was run for 139.5 hours and the vehicle odometer read 1868 miles.

During the first 18 months of the program, baseline P-40 Stirling engines wereassembled and delivered to NASA, MTI, and AM General Corporation (AMG). The

P-40 engines were tested and assembled, and subsystems and components were

developed and evaluated at United Stirling of Sweden (USS). Component efforts

at MTI are underway and are reported in this rep9rt.

A breakdown of engine and test-rig operating hours is shown:

Component Test-Rig Operating Hours (as of 9/30/79)

Check Valves 2012.0 hours

Seals 441.0 hours

Combustion Development 2899.5 hoursSeal Development Test Rig No. 1 206.0 hours

TOTAL 5558.5 hours

P-40 Engine Operating Hours (as of 9/30/79)

Opel Engine 188.0 hoursNASA Engine 48.0 hours

MTI Engine 35.0 hours

Spirit Engine 139.5 hours

At 820°C 1200.0 hours

Other Testing 102.1 hours

TOTAL 1712.6 hours

-1-



2.0 INTRODUCTION

The Automotive Stirling Engine Development Program is directed at developing

the technology relating to the automotive application of Stirling engines.

Mechanical Technology Incorporated was selected as the prime contractor to

carry out the program, which is funded by the U.S. Department of Energy (DOE)

and administrated by the National Aeronautics and Space Administration at the

Lewis Research Center (NASA-LeRC). NASA Contract No. DEN3-32 was awarded to

MTI on March 23, 1978.

MTI is responsible for overall program management, mechanical component and

systems development, engine and vehicle testing and evaluation, computer code

development, and transfer of Stirling engine technology from Sweden to the

United States. The engine development program is based upon the extensive

technological advancements, capabilities, and background knowledge in Stirling

engines of KB United Stirling (Sweden) AB & Co. (USS), a subcontractor to MTI.

AM General Corporation (AMG), a wholly owned subsidiary of American Motors

Corporation, is the subcontractor responsible for automotive selection, design,

integration, and evaluation of Stirling engines installed in passenger cars.

The Automotive Stirling Engine Development Program consists of engine develop-

ment supported by parallel component development effort. This approach was

made possible by the existence of a baseline Stirling engine (P-40) at USS and

many hours of successful in-vehicle experience (the V4X35 in the Ford Taunus,

the P-75 Mark 1 in the Volvo light-duty truck, and the P-40 in the Opel and

the Spirit sedans).

The selected program logic recognizes the current development status and the

ultimate program goals. To achieve the program's objectives, the following

major development challenges must be met:

• High efficiency (performance) resulting in improved fuel economy.

• Acceptable initial cost and low specific weight.

The current program, as recently modified to coincide with the requirements of

the "Automotive Propulsion Research and Development Act of 1978", will consist

of the development of two generations of Automotive Stirling Engines (ASE).

ASE Mod I will be the selected concept chosen from the reference engine

concept study (Task 1) and will be improved through light-weight construction

(automotive design practice) and through system (engine/vehicle) matching.

ASE Mod II will be an upgraded version of ASE Mod I, adding performance

improvement features to ASE Mod I. Improvements will be obtained throughengine development/testing, through components and subsystems development

carried out in parallel, and from the use of improved auxiliaries and

accessories. Component and subsystem development, refinement of the external

heat system, and high temperature operation will converge upon ASE Mod II.

The final Program Objectives are to develop and demonstrate, by September

1984, an Automotive Stirling Engine System, which when installed in a 1984

vehicle, will meet the following objectives:

-2-



1. At least a 30 percent improvement in combined cycle fuel economy

(mpg), based on EPA test procedures, over that presently predicted

for a comparable 1984 production vehicle. The reference 1984

production vehicle shall be powered by a conventional spark-ignition

engine. Both the automotive Stirling and spark-ignition engine

systems will be installed in identical model vehicles* and will

give substantially the same overall vehicle driveability and per-

formance. The improved fuel economy will be based on fuel of thesame energy content (Btu/gal). The absolute fuel economy goal will

not vary over the life of the contract.

2. Gaseous emissions and particulate levels less than the following:

NOX =0.4, HC = 0.41, CO = 3.4 g/mile and a total particulate level

of 0.2 g/mile using the same fuel economy measurements.

* It is intended that identical model vehicles be used for the

comparison. However, a difference in inertia weight between the

two vehicles is acceptable if the difference results from the

substitution of the automotive Stirling engine system for the

spark-ignition powertrain system.

The following system design objectives will also bemet:

1. Ability to use a variety of alternate fuels.

2. Reliability and life comparable with powertrains currently on the

market.

3. A competitive initial cost and a life-cycle cost no greater than

that of a comparable conventionally-powered automotive vehicle.

4. Acceleration suitable for safety and consumer considerations.

5. Noise and safety characteristics that meet the currently legislated

or projected Federal Standards for 1984.

Because of program redirection and renegotiations currently underway, the mile-

stones and schedule presented below are not approved, but are expected to be

incorporated into the new contract. Until such time, they are presented for

information only.

Program milestones are as follows: (See Figure 2.0-1)

1. ASE Mod I design freeze and assessment prior to March 31, 1980.

2. Complete dynamometer characterization and assessment of first build

of ASE Mod I prior to September 30, 1981.

3. Complete dynamometer characterization and assessment of ASE Mod 1

(updated) prior to September 30, 1982.

-3-



4. Deliver ASE Mod I system (in vehicle) to EPA prior to September 30,

1983.

5. Complete dynamometer characterization and assessment of ASE Mod II

prior to September 30, 1983.

6. Deliver ASE Mod II system (in vehicle) to EPA prior to September

1984.

Fiscal Year

1979 1980 1981 1982 1 9 8 3 1 9 8 4

ASE Mod I Design Freeze

ASE Mod IDyno Test

Dyno Charac ter iza t ion T ASE Mod I Upra ted

I IA S E Mod I EPA Vehic le Test

l - r e

A S E M o d I I Dyno T e s t

A S E M o d I I E P A V e h i c l e T e s t

F i g u r e 2.0-1 Program M i l e s t o n e s

In order to comply with the provisions of Title III of Public Law 95-238, the

"Automotive Propulsion Research and Development Act of 1978", the MTI program

as originally presented in previously issued quarterly reports is being

redirected, rescheduled, and rebudgeted.

The current, modifi ed program consists of nine major program tasks, scheduled

over six and one-half years, as shown in Figure 2.0-2. Task 6.0 of the

original program, pertaining to the third engine generation, was eliminated

and a task titled "Prototype ASE System Study" is being planned.

Task 1; Reference Engine

This task consist of a technology assessment effort (completed) and a

technology assessment report which was written and delivered to NASA. The

development and updating of a Reference Engine System Design (RESD) which

will reflect the latest design in order to meet the final program

objectives, is a continuing effort throughout the program.

-U-



1971 1579 1980 1981 1982 1983 1984

Components ft Subsystem Technology Development

Baseline Engine System

Task 4 ASE Mod I Engine System

5 ASE Mod II Engine System

Taik 7 Computer Program Development

Task 8 TechnicalAssistance

Taw 9 Program Management

Figure 2.0-2 Program Task Schedule

Task 2; Component and Subsystem Development

Work will be initiated in response to joint NASA/USS/MTI/AMG task force

recommendations, covering the heating system, engine mechanical seals,

systems and drives, controls, materials, accessories, and auxiliaries. Workwill be directed at improvements in Stirling engine systems for ASE Mod I

and ASE Mod II.

Task 3: Baseline Engine System (P-40)

The existing P-40 Stirling engine system will be the Program's Baseline

Engine System. Five P-40 engines will be built.

• The first engine is installed in the 1977Opel.

• The second engine has been delivered to NASA for test and evaluation.

• The third engine was delivered to MTI in April for complete engine

disassembly, documentation, reassembly, and testing.

• The fourth engine was delivered to AMG and was installed by AMG into

the 1979AMC Spirit sedan.

• The fifth engine will be delivered to MTI early in FY1980 as a spare.

Facilities are under construction at MTI for engine, vehicle, and component

test ing.

-5-



Task 4; ASE Mod I System

This will be the first "clean sheet of paper" automotive Stirling engine

developed on the program. Design effort has started on this 4-cylinder,

square "U" configuration engine. Plans call for six engines and three

vehicles. Engine deliveries are scheduled to start early in 1981.

Tentative specifications and parameters are as follows:

Power level 58 kW

Fuel Economy 27.5 mpg Heater Tube Temperature 720°C

(AMG Spirit)

Noise < Opel Emissions To meet all

standards

Specific Weight 6-7 Ib/HP Fuel Gasoline or

diesel

Task 5: ASE Mod II System

This engine system will be an upgraded version of ASE Mod I, using newdesign concepts which have been proven prior to the ASE Mod II design

review date. Predesign is planned to start in October 1981. Plans call

for five engines and three vehicles. Engine deliveries are scheduled to

start in mid-1983.

Task 7; Computer Program Development

This task covers only those computer codes necessary for implementation of

the program. These include an engine performance code, heater system

modeling, cooling system modeling, mechanical drive system modeling, a

thermodynamic cycle nodal code, an engine transient response code, and an

engine optimization code.

Task 8: Technical Assistance

Effort will be performed as requested by the Government. This work will

relate to the scope of the total contract, and will involve demonstrations,

training, displays, and other forms of assistance.

Task 9: Program Management

This task consists of program administration, management and control,

reports, product assurance, training, and contract administration.

-6-



3.Q PROGRESS SUMMARIES

The MTI Automotive Stirling Engine Development Program has completed 1-1/2

years of effort.

The following quarterly reports have previously been published:

Quarter Covering Period MTI Report No.

1st March 23-July 1, 1978 78ASE16QT1

2nd July 2-September 30, 1978 78ASE32QT2

3rd October 1-December 31, 1978 79ASE43QT3

4th January 1-March 31, 1979 79ASE67QT4(DOE/NASA/0032-79/2,

NASA CR 159606)

5th April - June 30, 1979 79ASE88QT5(DOE/NASA/0032-79/3,

NASA CR 159610)

This report covers the sixth quarterly period of July 1, 1979 through

September 30, 1979.

The following is a summary of each of the program's major tasks.

-7-



3.1 MAJOR TASK 1 - REFERENCE ENGINE

This task is intended to guide component, subsystem and engine system

development. A reference engine system design will be generated and conti-

nually updated to reflect the best contemplated approaches and the latest

technology to meet the final program objectives. The reference engine system

will be the focal point to guide development, will be based on approved engine

system concepts, and will include anticipated 1985 vehicle power level and

size for equivalent spark ignition, diesel, and stratified charge engines.

A comprehensive technical assessment will be made of the present status and

level of technology of Stirling engines as candidates for automotive power

plants. This assessment will be directed at, but not limited to, the status

of United Stirling of Sweden's engine design and development technology. When

completed, the Initial Technology Assessment will be used as a basis for a

detail study and reevaluation of the overall technical program plan.

3.1.1 Initial Technology Assessment

The final camera-ready copy of the Initial Technology Assessment Report

was delivered to NASA in mid-September. The report will be sent out for

printing and will be available for distribution in mid-December. For

reference purposes, the report numbers are: DOE/NASA/0032-79/4, NASA

CR-159631, MTI 79ASE77RE2.

3.1.2 Reference Engine System Design

The USS modified driving cycle vehicle simulation computer program is

now available for use.

- The engine friction model was updated to include bearing oil-film

temperature rise.

- Correlations against motoring tests were performed.

- Mileage calculations are currently being run for different

optimized engines with alternative maximum values of speed,

pressure, and temperature. The results indicate that further

investigation is needed in order to present firm recommendations.

- Different air preheater alternatives are also being compared.

Preliminary calculations indicate that different alternatives yield

a 3% difference in mileage. Mileage is better for recuperative and

preheater alternatives, mainly due to the power requirement for the

regenerative alternatives.

-8-



Front wheel drive feasibility studies were conducted at AMG and layout

drawings of potential interferences were made. The purpose of these

studies is to evaluate possible interference areas so that their impact

on Mod I and II design activities can be evaluated. The transmission

and drive assembly of a GM "X" body vehicle was obtained for study.

An alternative piston rodseal,

using a flexible membrane between the

cap seal and a modified Leningrader seal, was studied. Seal housings,

including connections for cycle gas (max., min., and supply), were

completed. Figure 3.1.2-1 shows this new, experimental seal system.

The regenerative air preheater for the RESD was studied and drawings

were completed. The size of the preheater has been kept within

reasonable limits by dividing the matrix into two cores placed opposite

each other. By using ceramic low expansion seal supports on the hot

side, the seals were simplified and the flexible membranes were

eliminated.

A c'esign assessment meeting was held at MTI on September 26, 1979 to

firalize the RESD and ASE Mod I vehicle specifications and to review the

current approach for the RESD. The meeting was attended by MTI/USS/-

AMC/NASA. As a direct result of this meeting, new vehicle specifica-

tions are being prepared.

Fig ire 3.1.2-2 shows the current reference engine. It has four

panllel cylinders in a square cluster, with separate regenerator

housings placed outside the cylinders. The drive mechanism consists of

two crankshafts and a main shaft connected together by a synchronizing

mechanism. The cylinder block is, at least partially, made of aluminum

and the crankcase is a light alloy casting. The pressure vessel formed

by the cylinder heads, the cylinder barrels and the piston rod seal

housings are kept together by long bolts close to the circumference;

this way only the net piston forces are transmitted down to the

crankcase. Figure 3.1.2-3 shows the reference engine as it would be

packaged into an X-body vehicle.

-9-



Piston

CylinderPressureMPa

21,5

10,0

Kapseal

10 MPaRodScraperHydrogen

Time

seal element

Filter

Crosshead

Figure 3.1.2-1 Altern ative Piston Rod Seal

-10-



Figure 3.1.2-2 Current Reference Engine Design

mri-19621

-11-



Figure 3.1.2-3 Re ference Engine Incorporated into X-Body Vehicle

MECHANICAL

TEC H NOLOGY

INCORPORATED

-12-

MTI-1945



3.2 MAJOR TASK 2 - COMPONENT AND SUBSYSTEM DEVELOPMENT

This task covers component and subsystem development as guided by the

knowledge already gained from the existing P-40 and P-75 Stirling engines,

from the Initial Technology Assessment effort, and from the Reference Engine

System Design work.

Components and subsystems will be developed in support of ASE Mod I and ASE

Mod II engine developments. The task will include: conceptual and detail

design analyses; hardware design, fabrication and assembly; component and

susbystem testing in laboratory test-rigs and in operating engines.

Only those activities expected to result in improvements within the time frame

of the program will be covered under Major Task 2. Advanced developments

beyond the scheduled design review date for ASE Mod I and ASE Mod II will not

be a part of this task, but may be part of the new Task 6.

The component and subsystem development task will be directed to solving the

problems associated with successful demonstration of the Stirling engine forautomotive propulsion. Experts conclude that the present performance of the

Stirling engine is sufficient to replace current internal combustion engines,

and that the reliability and life requirements can be met. They also conclude

that in order to penetrate the automotive market, engine cost and complexity

must be reduced. Therefore, high engine performance must be maintained while

reducing cost by reducing complexity, substituting easily available materials

for superalloys, reducing weight and improving individual components by

intensive and directed development.

For information/orientation purposes, photographs of some of the components of

the P-40 engine are shown in Figures 3.2-1 to 3.2-18.

3.2.1 Combustion and Heat Transfer Technology Development

The objective is to advance the state of technology of the heating

system and heat exchanger components, in terms of durability, relia-

bility, performance, cost, and fabrication technology, using the exist-

ing P-40 components as a baseline.

Work on Stirling engine combustors has been directed at simple, fixed

geometry designs, with either exhaust gas recirculation (EGR) or

combustor gas recirculation (CGR) to reduce NOX levels. Work on the

combustion system will be aimed at improving the overall life and

reliability of the components without sacrificing performance in termsof efficiency and emissions.

Fuel nozzles and fuel atomization/vaporization techniques will also be

studied to reduce cost and improve performance.

3.2.1.1 Combustion Development

The inherent advantages of the Stirling engine over the internal

combustion engines are:

1. High thermal efficiency and,hence, better fuel mileage.

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Page Intentionally Left Blank



MECHANICAL

TEC H NOLOGY

INCORPORATED

Figure 32-1 Preheater Housing

-15-MTI-19582



Exhaust PortCombustion Air Blower

Turbulator

Exhaust PortInsulation Shield

Igniter Mounting Ai r Blower Inlet

Figure 3.2-2 Preheater Housing and Adjacent Components

MECHANICAL

TECHNOLOGY

INCORPORATED

-16-

MTI-19



Heater Tubes

Upper Half of Block Assembly

Regenerators

Pistons

Figure 3.2-3 Side View of Heater Head Quadrant

MECHANICALTICHNOtOCV

1NCOKPORAT60

-IT-

HTI-19575



Figure 3.2-4 Top View of Com bustor

MECHANICAL

TECHNOLOGY

INCORPORATED

-18-

MTI-195



Figure 3.2-5 Cooler

MECHANICALTECHNOLOGY

INCORPORATED

Figure 3.2-6 Regenerator

-19-

KTI-19572



Figure 3.2-7 Combustion Air Blower

MECHANICAL

TECHNOLOGY

INCORPORATED

-20-

MTI-19



Figure 3.2-8 Air Pump

MECHANICAL

TECHNOLOGYINCORPORATED

-21-

MTI-19577



Piston Rod .

Slipper

Connecting Rod

Figure 3.2-9 R od Assembly

MECHANICAL

TEC H NOLOGY

INCORPORATED

-22-



fillMECHANICALTECHNOLOGY

INCORPORATED

Figure 3.2-10 Piston Seal Assembly

-23-MTI-19585



MECHANICAL

TECHNOLOGY

INCORPORATED

Figure 3.2-11 Gas Seal Housing Cartridges

-2h-

MTI-195



Main Seal Housing

Backers Used in Cap

Seal Assembly

Figure 3.2-12 Seal Assemblies

MECHANICAL

TEC H NOLOGY

INCORPORATED-25-

MTI-19580



Figure 3.2-13 Fuel Nozzle

MECHANICAL

TECHNOLOGY

INC OR P OR ATED

-26-

JfH-1957



Main Shaft

Drive Gears

Figure 3.2-14 Rear View of Engine Exposing Drive Gears

MECHANICAL

TECHNOLOGY

INCORPORATED

-27-

MTI-19584



Figure 3.2-15 Crankcase/Main Shaft

MECHANICALTECHNOLOGY

INCORPORATED

Figure 3.2-16 Underside of Engine

-28-

MTI-195



pressorting Point

I Pump

Figure 3.2-17 Parallel Cr an ks haf t and Bedplate Assembly — Top View

Figure 3.2-18 Cra nk sh afts without Drive Gears

MECHANICALTEC H NOLOGY

INCORPORATED-29 -

KTI-19574



2. Low pollution product.

3. Ability to burn a wide variety of fuels.

Although the Stirling engine combustors do indeed produce low

carbon monoxide (CO) and very low total hydrocarbons (HC), the

nitrogen oxides (NOX) have been higher than that specified by the

EPA 1984 objectives. The reason is simple: A high efficiency

combustor operating at near stoichiometric fuel/air ratios willproduce high gas temperatures; these high temperatures in the

presence of and 02 will produce NOX.

Some of the methods of inhibiting the formation of NOX are:

1. Withdraw heat from the burning gas, thus keeping it cooler.

2. Reduce the oxygen content so that there are fewer 0-atoms

to react with the N-atoms.

3. Burn with a rich or lean mixture to keep the temperature

down.

All three of these methods are used in exhaust gas recirculation

(EGR) and combustion gas recirculation (CGR)methods. The burning

mixture, which contains about 25% excess air, is operating in the

lean stoichiometric region; some heat is withdrawn from the

burning gas by radiators to the heater tubes; and the recirculated

exhaust gas (EGR or CGR) reduces the 0-atom concentration and

flame temperature.

In the "standard" engine, the exhaust gas is discharged after

passing through the preheater. In the EGR system, some fraction

of the exhaust gas is introduced into the combustion air justupstream of the blower. In the CGR system, the blower pressure is

increased to produce a high velocity jet which is then used as a

jet ejector pump to recirculate a portion of the combustion gas

before it passes through the preheater.

The question to be resolved is: Is there a clear-cut advantage to

EGR or CGR?

3.2.1.2 The EGR system

The EGR system is shown in the block diagram of Figure 3.2.1.2-1.

Note that the Burner Air Flow Control also permits recirculation

of flow from the blower if there is more than is needed.

Tests were made to determine the amount of NOX reduction with

specified quantities of EGR. EGR levels up to 90% showed marked

reductions in NOX. A preliminary objective of 50 to 55% recircu-

lated gas was selected as a reasonable value for evaluating EGR

and CGR.

-30-



014-1

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ao

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60

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-31-



The % EGR and CGR may be defined as follows:

Mass of recirculated gas

% EGR and CGR = x 100

Mass of inlet air

Volume of recirculated gas

% EGR and CGR = x 100

Volume of inlet air

The volume of recirculated gas and inlet air can be determined by

exhaust gas and combustor inlet (air plus gas) analysis for either

CC>2 or 02 volume fraction.

Tests were made with the EGR system, using a simple flow

restriction device to control percent of EGR. The test results

showed that this device resulted in a variation of percent EGRwith power level. There was a sharp rise in EGR percent at low

power, which caused combustion to become unstable. This was

remedied by installing an on-off EGR valve, which was actuated

from a power level control, so that EGR was turned off at low

power levels. This was still not satisfactory to reach the

objective of having a control which exhibits a "flat response" of

EGR to power level.

Finally, a proportionally operated valve was used, which produces

a much better response except for the very low power end where

some hysteresis was noted. The EGR percent, however, was low but

an adjustment has been made, and the valve will be tested at 50-55percent EGR.

CO level is not a concern for this combustor design. Measured CO

levels for EGR fractions up to 100% are shown in Figure 3.2.1.2-2.

For a range of fuel flows from 1 to 3 grams/sec, the CO content

did not exceed 100 ppm. Since the EPA maximum allowable level is

about 1200 pp m, CO is not a problem with these engines.

3.2.1.3 The CGR System

The CGR system is shown in in the block diagram of Figure 3.2.1.3-1.

The principal difference between CGR and EGR is that the hot gas

is not required to pass through the preheater, d ucting, or blower.

This, in itself, red uces the loading on the preheater and blower

in addition to reducing the size of the piping needed to carry the

gas. A CGR bypass valve is shown, which reduces the pressure loss

in the system at high power levels by bypassing part of the gas

around the high-pressure loss ejector.

The ejector action is shown for one operating condition (idle) in

Figure 3.2.1.3-2. A high velocity jet is produced by reducing the

air flow area from the blower, which causes increased blower-air

-32-



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Pressure Drop

Required For

Jet Pumping

Figure 3.2.1.3-2 Design Pressure Drop and CGR Pumping at Idle Conditions

MECHANICAL

TECHNOLOGY

INCORPORATED

-35-



pressure. The static pressure at the jet exit drops, creating a

low pressure zone into which the exhaust gas flows. The exhaust

gas is then entrained by momentum exchange in the tube, the static

pressure rises, and the gas mixture is injected into the combus-

tor. The CGR valve is shown in Figure 3.2.1.3-3. The gas bypass

is controlled by rotating the upper portion of the valve, which

regulates the alignment of the flow ports at the lower end. The

control is set to start opening the valve at the maximum CVS cycle

power. At maximum power, the valve cuts pressure drop by more

than half, while the CGR quantity drops from near 50 percent down

to less than 5 percent.

Data showing reduced NOX, using CGR, are shown in Figure 3.2.1.3-4i

The data were from combustor rig tests where three different

ejector sizes were used. The general trend is for lower NOX at

higher fuel flow, or higher power level. While the data is consi-

derably scattered , all of the NOX values at fuel flows higher

than 1 gram/sec lie within the EPA objectives.

3.2.1.4 Comparison of EGR and CGR Performance

Data for Stirling engine number ASE40-1 and ASE40-7 (P-40 Nos. 1

and 7) with the on-off EGR valve, provid e an erratic NOX emissions

trend which does not appear to be satisfactory for the EPA goal;

however, data from ASE40-5 in the Opel, for two tests, show that

the CVS cycle NOX was lower than the EPA goal. The new EGR valve

with proportional control has the potential for better NO X

performance than the on-off valve. Further dev elopment tests of

this valve are being planned.

A comparison of the EGR and CGR control valv es is shown in Figure

3.2.1.4-1, where percent EGR or CGR is plotted versus fuel flow.

The difference in purpose and effect of the EGR and CGR control

valves is clearly shown. NOX prod uction, using these same valves,

is shown in Figure 3.2.1.4-2. Also shown is the anticipated NOX

performance for the new proportionally-controlled EGR valve. This

plot indicates that the new EGR valve may perform better in NO X

reduction than either the on-off EGR valve or the newer CGR valve;

however, this anticipated result must be confirmed in testing.

Table 3.2.1.4-1 contains a comparison of EGR and CGR with the

"standard" (no EGR or CGR) engine. The "hot end" efficiency ( nB)

for the standard engine and CGR engine are about equal; however,

about 2.28 percent of ^3 is lost in the EGR system, mainly inpreheater losses. Heater head losses are about equal for CGR and

EGR. The net effect is approximately a 3 percent loss in the EGR.

compared to CGR, or about 1 mpg.

Table 3.2.1.4-2 shows a comparison of the advantages and

disadvantages of CGR versus EGR. CGR has already been developed

to an operating stage (over 500 hours), but development is not

completed. Aft er completion, CGR is anticipated to improve gas

mileage by 1 mpg. This anticipated improvement is based on engine

system calculations.

-36-



Figure 3.2.1.3-3 CGR Bypass Valve

-37-

MTI-19559



©

0

©

Fuel m,. g/ser

Figure 3.2.1.3-4 NOx Versus Fuel Flow Using CGR

IHHJ


INCORPORATED

-38-



Idle Max Power

100

80

60

o

8w 40

20

Oper. Range

CVS Cycle

EGR (P-40 No. 5 in Opel

USS 78-0068C)

CGR

CGR Bypass

Opens

2 3

Fuel Flow, g/seo

Figure 3.2.1.4-1 Comparison of EGR and CGR Control Valves

MCCHAMCU

TtCHNOLOGV

INCOHPOHATtD-39-



6r

M3

w

EGR With

On-Off

Valve

C C ; R w i t hB y p a s s

Idle CVS Cycle

Max

Power

2 3

Fuel fn, g/sec

Figure 3.2.1.4-2 Comparison of NOx Reduction Methods Using EGR and CGR

MECHANIC*!.

TECHNOLOGY

IMCORPOflATED



n B H E A T E R H E A D & P R E H E A T E P E F F .

A n B P R E H E A T E R P E M A L T Y

A n B H E A T E R H E A D P E N A L T Y

1 C O M B U S T OR

R E L A T I V E HB

M PG C H A N G E - M E T R O

- H I G H W A Y

- M E T R O & H I G H W A Y

NO

E G R / C G R

86.17

-

-

9 9 . 9

1.0

REF

RE F

RE F

EGR

83.77

2.28

.12

9 9 . 9

.97

- .8

-1.1— 9

CGR

86.05

-

.12

9 9 . 9

1.0

-

—

Table 3.2.1.4-1 CVS Cycle Comparison

MECHANICAL

T ECHNO L O G Y

INCORPORATED -111-



ADVANTAGES DISADVANTAGES

EGR

1. An existing system that reduces

NO X

2. Variable EGR valve has potential

for fhrther NOX reduction

_ C G R

1. Does not require gas cooling to

protect blower

2. Smaller air ducting to blower

3. 37 mpg improvement over EGR

( 1

1. NOX value is marginal to meet

EPA limits

2. Reduced blower life from hot

hot gases

3. Variable EGR valve still under

development

1. By-pass valve development not

complete

2. Complex combustor shape for

manufacturing

3. NOX still marginal

4. Engine tests not yet made

Table 3.2.1.4-2 Advantages/Disadvantages of EGR and CGR

MECHANICAL

TECHNOLOGY

INCORPORATED -H2-



A further comparison of EGR versus CGR and the "standard engine

combustor" with respect to blower requirements, is shown in Table

3.2.1.4-3. A high efficiency (72.5%) blower was assumed to be

used. For CGR, a large increase in pressure loss is shown for the

combustor, mainly caused by the ejector pressure needed for jet

pumping.

However, the preheater A P is significantly lower for the CGR

system leading to approximately the same system P as the EGR

system. In addition, there is a decrease in blower air flow

because with a CGR system, the blower does not have to handle the

recirculated gases. The net result is a decrease in blower power

requirement for CGR relative to EGR.

The following conclusions may be drawn relative to EGR and CGR:

1. Present EGR reduces NO by a large amount, yet NOX emission

is still borderline based on EPA requirements.

2. The variable EGR valve may produce lower NO X, but more

testing and development are required.

3. Analysis shows 3 percent or 1 mpg improvement of CGR over

EGR, mostly from preheater performance.

4. Continued development of the CGR bypass valve is needed,

although the present tested valve life is more than 500

hours.

5. EGR and CGR can use the same preheater and the same blower

could be used.

6. NOX reduction by EGR and CGR is about the same, and both are

marginal for EPA requirements.

3.2.1.5 Heat Exchanger Development

During July 1979, the primary emphasis of the heater head/regene-

rator development program was in designing a regenerator pressure

drop test rig. A schematic design for this rig is shown in Figure

3.2.1.5-1.

The system consists of a dry lubricated compressor, heat removal

and surge tank assemblies, a heater, and a test section. The testsection will have pressure taps and thermocouples to measure the

gas properties at the inlet and exhaust of the regenerator. The

test section will also contain a flow straightener, to establish

slug flow conditions at the regenerator inlet.

Using nitrogen, the rig has been sized to give pressure drop

measurements for the engine operating range of Reynolds number

from 10 to 200. The high volumetric flow rates associated with

the higher Reynolds nunbers presents a d ifficult design problem

because of the size of the equipment and its high cost. By using

- u s -



For 1200 Plate Preheater

Combustor AP, Pa

Preheater AP

Heater H e a d A P

A /F Control & Man.

T O T A L

Blower Efficiency

Blower Power, Watts

I D L E

m f =4 g/s

NO

E G R/ CG R

6

134

10

2 2

17 2

2 2 %

25

E G R

13

200

16

29

258

317,

48

CGR

9 7

135

13

2 2

2 6 7

2 2 %

39

M A X . P O W E R

m f = 5.0

N O

EGR/ CGR

580

1680

265

2 9 6 6

5491

7 2 . 5 %

5 7 2

EGR

1255

2870

519

3700

8344

7 2 . 5 %

1510

C G R

3235

1680

265

2966

8146

72 . 5%

848

Table 3.2.1.4-3 Comparison of MOD I Blower Requirements

MECHANICAL

TECHNOLOGY

INCORPORATED-hh-



S

YP

P

D

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P

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nitrogen and designing a closed cycle system operating at 10 to 15

atmospheres, actual operation can be simulated with a moderately

priced system.

Sizing of components for the regenerator pressure drop test rig

was initiated and price quotations were requested from several

manufacturers. To meet requirements, the following specificationswere placed on the compressor:

• Dry lubrication - The compressor must be dry lubricated to

prevent contamination of the regenerators and possible

degradation of the heat transfer surfaces.

• Flow specification - The compressor must continuously deliver

up to 100 standard ft.3 /min. (SCFM) of helium or nitrogen

across a pressure differential of 20 psi.

Formulation of a development program for the heater head has begun.

The initial definition for this effort focused on development of a

mathematical model for the tubular P-40 heater head. This work will

be used to formulate a test program by defining critical test

parameters, test hardware, and instrumentation. The mathematical

model will also provide a basis for validating test results and

projecting improvements for new designs.

3.2.1.6 Heat Flows for P-40 Opel Heating System (Engine ASE40-5)

The heat flows were determined at half load and heater temperatures

of 720°C and 820°C, for the heat flow Qj through Q12, as shown in

Figure 3.2.1.6-1. Fuel flow was 2 g/s, air excess factor was 1.38,

and EGR was 50% of air flow. The results are as follows:

Symbol Heat Flow from: to Watts at Watts at

720°C 820°C

Q! Preheated air: Surroundings 335 387

Q2 Exhaust gas: Surroundings 497 570

Qj Inlet air: Surroundings 121 133

Q^ Preheated air: Exhaust gas 58 68

Q5 Preheater: Exhaust gas 126 148

Qg Combustion gas after heater:

Preheater 289 344

Qy Combustion gas after heater:

Inlet air 113 133

Qg Combustion gas before heater:

Engine block 26 27

-46-



Figure 3.2.1.6-1 Heat Flows for P-40Opel Heating System

- U T -



Symbol Heat Flow from: to Watts at Watts at

_ _ 720°C 820"C

Qo Combustion gas between heater:

Engine block 26 29

Combustion gas after heater:Engine block 33 38

Fuel injector: Surroundings 249 286

Ignitor: Surroundings 71 81

Q2 and Q^ do not affect the efficiency of the heating system. The sum

of Q1 and Q4 - Ql2is 1326 Wattsa

t 720°C and 1541 Watts at 820°C.

3.2.2 Mechanical Technology Development

The objective is to advance the technology of mechanical drives and

mechanical components using the existing P-40 engine as the baseline.

The drive system presents a major development challenge in terms of

establishing design simplicity. It is clear that this area must be

addressed in terms of performance versus cost. It is planned to

emphasize the development of combination drive/control schemes. Basic

mechanical design calculations will also be performed on the existing

drive system to reduce losses and improve performance. Lubrication

techniques will be studied. Bearing design and losses associated with

the applied loads will be critically evaluated. Thermal effects will be

identified. For the improved designs resulting from the work the

relation to life and reliability will be studied.

3.2.2.1 Materials Screening Test Rig

The drive unit motor for the Materials Screening Test Rig was

received; the rig (shown in Figure 3.2.2.1-1) was assembled and it

is ready for testing.

Sample test coupons and seal test samples were prepared. After the

initial checkout operation of the materials screening tester, the

crosshead bearing failed. This bearing is a linear ball bushing.

The shaft was reground and a bearing bronze bushing was substituted

for the linear ball bushing. Initial tests appear to be satisfactory.

3.2.2.2 Workhorse Test Rig

A design review on the workhorse rig was held at MTI. The major

emphasis was on cost reduction. There were three major decisions

made as a result of this meeting:

- Design test heads will be able to evaluate four seal elements

per test head instead of two elements per test head. This

concept, which will double the effectiveness of each test

head, has already been incorporated into the layouts.

-U8-



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0

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- Current thinking is that three engine blocks should befabricated into the workhorse test rig. Each block wouldcarry three test heads and test twelve seal elements.

- The three engine blocks would be used as follows: one for

main seal tests, one for cap seal tests, and one for piston

ring tests. Four test heads would be available for each

block, so that one test head would be readily available incase another test head fails.

These three decisions are expected to reduce equipment cost by a

factor of more than two, and will be compatible with the available

budget.

The design layouts of the test heads for the Workhorse Seal TestRig were completed for piston rings, cap seals, and main seals.

- Procurement of a hydrogen leak detector was approved by

NASA.

- A Chevrolet 6-cylinder, 250 cubic inch engine block wasselected for the drive unit and base of the workhorse test

rigs.

- Preliminary schematics of the hydrogen gas system and of the

nitrogen leak detector gas system were prepared.

- An internal design review on the workhorse rig was held onAugust 14; actions items recommended at the meeting were

completed.

3.2.2.3 Exploratory Test Rig

Design layout activity on the exploratory tester, which is alsothe pumping ring test vehicle, was initiated. Orders were placed

for the crankcase castings and for the crankshaft casting for thedrive units. The design layout of this rig is expected to be

completed in October, and an internal design review will be held.

3.2.2.4 Engine Drive System

A meeting was held at Ricardo Consulting Engineers Ltd., todiscuss the noise generation in the P-40 engine. Results of the

Ricardo work were reported to NASA at a meeting at MTI on ThursdaySeptember 27th, and will be reported at the DOE Contractors

Coordination Meeting (CCM) on October 23, 1979. A copy ofRicardo's CCM paper is included in Appendix A of this report.

3.2.3 Auxiliaries Technology Development

The objective is to advance the existing technology on the baseline P-40auxiliaries towards the specific goals of durability, reliability,

performance, weight and cost, in order to meet the final program

objectives.

-50-



Considerations of the auxiliary equipment required by this engine, and

therefore the parasitic losses associated with this equipment, can

provide a siginificant payback in terms of performance and cost. It will

be necessary to define the engine requirements and to develop an

improved combustion air blower and power control hydrogen compressor for

minimum losses. The remainder of the auxiliaries are common components

to internal combustion engines; however, integration with the engine

must also be provided with minimum losses. A detailed study of the

engine cooling system must be addressed. Improvements in this area couldbe derived from innovative heat transfer system design and development.

The design of the Mod I Blower Development Rig was completed at MTI.

Figure 3.2.3-1 is a schematic drawing of the blower rig, and Figure

3.2.3-2 shows the three cross sections labeled in Figure 3.2.3-1. A

speed of 28,000 rpm was selected, based on the maximum efficiency

attainable with the bearing design. The procurement of parts for the

Mod I Blower Development Rig was initiated and will continue.

The Mod I combustion air blower bearing and rotor dynamics analysis was

completed.

- The analysis indicates that USS bearing design has adequate life if

the temperature of the grease is not more than 150°C. Andox "C" or

Multifax All Purpose grease is recommended. The blower environ-

mental temperature must be measured and logged, in order to verify

the conclusion drawn from the analysis.

- A pressed ribbon-type cage, which is currently used in USS bearing

design, may be adequate; however, a significant improvement in cage

life margin can be acquired. MTI recommended that a Barden

201SSTX1 bearing (with phenolic and aluminum cages) be considered

for this design.

An assessment of the blower design for EGR/CGR options indicates that a

simple modification of vane height can accommodate both options, as

shown in Figure 3.2.3-3. A rotor with a larger vane height will be

obtained so that it will be compatible with either concept.

3.2.4 Controls Technology Development

The objective is to advance the technology level of the current P-40

engine control system in order to meet specific system and program

objective requirements. The effort will also include a study of alter-

native concepts of control.

The drive/power control system components present a major development

challenge in terms of establishing design simplicity. Present engine

technology uses a crank-type drive system with a power control system

separate from the drive mechanism, and is based on reducing and increa-

sing the pressure level within the engine by hydrogen release and addi-

tion. A hydrogen compressor is employed to pump up the engine pressure

levels as required. This system has been perfected, and presently

provides adequate power control and engine response; however, the com-

plexity of the system is of major concern in both reliability and cost.

-51-



& D

£

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-53-



EGR Flow

CGR Flow

177 mm. (7.0") Limit

Figure 3.2.3-3 Dimensions of Vane Height for the Blower Design

30772

MECHANICAL

TECHNOLOGY

INC OR P OR ATED



In conjunction with the drive/power control, it is critical that one

considers the air/fuel control. As the engine power requirements are

varied, this control must adjust to maintain constant heater wall

temperature at variable heat input. Presently, the system air flow is

modulated by a temperature signal to a throttle valve, while fuel flow

is modulated by a fuel/air controller located in the fuel line. The

amounts of both fuel and air must be regulated to maintain temperature,while the mass flow ratio of these fluids must be maintained constant to

provide a proper ratio. This requires a complex electronic system and

precise measurement technology in order to provide adequate control.

It is planned to study these control requirements in detail, in terms of

sensor design and instrumentation miniaturization. New concepts will be

evaluated and,where practical, hardware experimentation will be

conducted.

Simplified computer analysis and modeling of certain control processes,

such as timed supply, dump, and dump short-circuiting, is underway. The

first-order Stirling engine code (ORDER 1) is being reviewed for possibl

modifications and additions so that it may be used in the quasi-steadyengine/control system simulation for the P-40.

Hydrogen solenoid valve design reports have not yet been received from

Valcor Engineering Corporation. These valve designs are intended to be

low cost, modular alternatives to the present compressor short-circuitin

valve, hydrogen bottle shut-off valve, and emergency gas dump valve

presently on the P-40 engine.

The test rig mounting has been completed for preliminary static/dynamic

operation of the piezoceramic actuator for the advanced hydrogen control

valve. The benefits and objectives to be derived in developing an

electrical actuating mechanism for the hydrogen control valve have notbeen fully identified. This information will form the basis for furtherwork on this task. Figure 3.2.4-1 shows an electric actuator. Figure

3.2.4-2 shows an electro-hydraulic actuator, and Figure 3.2.4-3 shows

the rod of the hydrogen power control valve.

To aid in planning, a preliminary comparison of selected alternative

power control systems has been prepared, and is shown in Table 3.2.4-1.

• It is concluded from Table 3.2.4-1 that benefits from a fixed-

charge power control system warrants its development and evaluation

for comparison with the current MPC system.

• Although three fixed-charge systems hold interest, additional

analysis and evaluation will be required before a preference can be

supported.

Preliminary evaluation of the constant stroke, variable displacement,

power control concept continued. Limited engine performance calcula-

tions support the feasibility of specifying both positive and negative

torque by changing one variable: the phase angle. Layout studies

indicate that it is feasible to integrate this method of control into

USS-type engines. Doing this will allow control development to proceed

independently. The constant-stroke variable-displacement system is a

-55-






Figure 3.2.4-1 Electric Ac tua tor

Figure 3.2.4-2 Electro-Hydra ulic Actuator

-57- KII-19550



Figure 3.2.4-3 Sliding Rod of Hydrogen Power Control Valve

i •-58-

MTI-195



Engine Hydrogen Charge

Relative Vehicle Hydrogen Charge

Relative Hydrogen Compression Energy

Vehicle Charging Pressure

Typical Engine Hydrogen Relative

Pressure

Separate Engine Braking Circuit

Hydrogen Valves Required for

Power Control

Hydrogen Valves Required for Engine

Braking

Open-loop Power Control Possible

Emergency H_ Pump to Storage

Compatible with USS Engine Design

Insensitive to Debris in Working

Cycle

Decreased Axial Conduction Loss

Reduced Driveaway Time

Reduced Cold Start Fuel Penalty

Immediate Stoppage of Engine Without

Rundown

Piston Dome (& Dome Volume)

Eliminated

Hybrid (with MFC) Feasibility

MPC

variable

1

1

1

0.25

yes

yes

yes

no

no

yes

no

no

no

no

no

no

-

Variable

Stroke

fixed

+ 0.5

-•0.5

* 0.25

1

yes

no

yes

yes?

yes

no

yes

no

no

no

no

no

-

Diagonal

Phase

Shift

fixed

0.5

./•0.5

0.25

0.8

no

no

no

no

yes

yes

yes

no

no

no

no

no

highest

Bypass

fixed

0.5

-•0.5

•"0.25

1

yes

yes

yes

yes

yes

no

yes

yes

yes

yes

yes

yes

-

Table 3.2.4-1 Comparison of Selected Alternative Power Control Systems

MECHANICAL

TECHNOLOGYINCORPORATED -59-



fixed-charge control system, which eliminates check valves, the hydrogen

compressor, and other control valves.

A Controls Task Force meeting (MTI/USS/NASA) was held at MTI on August

29-30, 1979. The key role of the Task Force in recommending development

strategy and evaluating progress was emphasized. The NASA and USS

members will review and critique MTI's proposed controls developmenteffort, and all members will review the control aspects of the vehicle

and engine specifications and will critique it for completeness and

acceptability.

The estimated costs of candidate transducers from interested vendors

ranges from $5 to $50. The cost of current pressure and position trans-

ducers are $1000 and $200 respectively. At the August, 1979 Control

Task Force meeting, it was recommended that MTI develop environmental

specifications and a testing program prior to formal quotation and

procurement of alternate transducers.

The relative performances of microprocessor products of Texas Instru-ments Inc. and Intel Corp. , which are being considered for use in the

digital electronic conversion, were assessed and were found to be

technically similar, and either system would do an adequate job.

Dynamic and step-response testing of a piezoelectric transducer was

completed at loadings of 0, 200, and 400 pounds. Results indicate that

published data for piezoelectric materials may be used to predict

performance.

An alternate version of a combustion-driven air blower was identified at

MTI. This blower concept has the potential of decreasing fuel

consumption and simplifying combustion control. The combustion driven

air blower conceptual idea has progressed through several cycles. The

current concept appears to be feasible, but has not been sized t,o give

the required flow output or checked for packaging feasibility.

3.2.5 Materials Developm ent

The objective of this task is to advance the technology of materials in

the Stirling engine in terms of durab ility, weight, cost and fabrica-

tion, using P-40 components as a baseline.

The heater head is probably the most important component in terms of

cost, mass production, and performance. It represents the greater

challenge to the designer because of the inherent constraints imposed

by the engine system. The heater head material must exhibit excellent

oxidation resistance, have excellent creep strength at high temperature,

have excellent thermal stress characteristics to preclude fatigue

failure, have desired thermal conductivity properties, and be immune to

hydrogen diffusion and materials embrittlement. In add ition, the heater

head nust be able to be mass-produced at a low cost.i

The potential to reduce weight and cost throughout the engine by

material substitution will also be studied.

-60-



3.2.5.1 Heater Tubes

MTI has ordered seamless tubing of Inconel 625 and Inconel X-750

from Uniform Tubes, Inc. Uniform Tubes, Inc. has expressed a

willingness to produce tubing of these alloys in the required

diameter, provided the drawings and schedules are supplied. Tube

Methods and Handy & Harman Tube Division have also been contacted.

Material can be procured from Carpenter Technology Inc. (Reading,

Pennsylvania) in the desired quantities.

A vendor was found for fabricating 19-9 DL tubing and Incoloy 901

tubing. Tube Methods (Bridgeport, Pa.) agreed to produce the

heater tubing from 0.750" diameter tubing produced by deep drilling

of rod. The deep drilling will be performed by Nassau Tool Co.

(West Babylon, N.Y.) or Clark and Wheeler (Los Angeles, Calif.).

A literature review on fatigue and creep failure in tubing was

initiated. The objective of this review is to relate tube

lifetime to uniaxial creep and fatigue strengths; this may lead to

a more thorough understanding of tube failures.

Work on assessing the creep and fatigue failure mechanisms in

heater tubes was postponed in September in order to accomplish

more pressing problems related to engine component procurement.

Although stress calculations have been provided by USS for the

condition of steady state temperature gradients, additional esti-

mates will be required of stresses associated with transient

conditions such as start up and shutdown. These estimates will be

required for the establishment of stress levels to be used in

fatigue testing of heater tube materials.

In view of the promising results of hydrogen permeation experi-

ments at NASA (which showed a significant reduction of hydrogenpermeation loss rates resulting from 2.5% CO and C02 additions to

the hydrogen), plans to discuss hydrogen barrier coatings for the

inside of tubes with Chemetal, Inc. were postponed until NASA data

are reviewed and the impact of C02 on the system is evaluated.

3.2.5.2 Cylinder Heads and Regenerator Housings

Metallographic studies of the engine-run heater quad rant conti-

nued. The heater head quadrant *as run at USS on the High

Temperature P-40 Engine for 7 hours at 7 MPa, 720° C; 83 hours at

15 MPa, 820°C and 752 hours at 7 MPa, 820° C (total accumulated

time 842 hours). The extent of porosity in the cylinder head andregenerator castings was examined at several critical locations.

Examination to determine the distribution of debris in the

regenerator, and additional metallography of the heater head

castings will be performed during the month of October. The

microstructure of the cast CRM-6D cylinder heads was examined and

was found to be qualitatively similar to that reported by Roy, et.

al. (A. Roy, F.A. Hagen, and J.M. Corwin, "Iron-Base Superalloys

for Turbine Engines", Journal of Metals, Vol. 17, #9, P.934,

[1965]).

-61-



MTI has encountered difficulty in procuring precision castings of

cylinder heads and regenerator housings. Hitchiner Inc. has

refused to produce investment-cast cylinder heads and regenerator

housings. Howmet has been contacted regarding MTI's casting

requirements, but has not yet responded. Presently, both found-

ries are reluctant to devote large development resources without

clear identification of a potentially large market. MTI willpursue this procurement search with additional vendors. Meetings

were scheduled with Turbine Components Co. (Howmet, Mich.) to

discuss the precision investment casting of cylinder heads and

regenerator housings for a P-40 engine. MTI will also meet with

Cannon-Muskegon Foundry (Muskegon, Mich.), to explore their

processes of remelting.

MTI has received one hundred and twenty pounds of an experimental

iron-base casting alloy, XF-818, from Climax Molybdenum. Eighty

pounds has been sent to USS for the fabrication (casting) of

cylinder heads and regenerator housings. A portion was also kept

at MTI for mechanical testing and metallography. Testing of alloyXF-818 revealed that its structure was similar to that described

in a Climax Molybdenum Co. Research Lab Report. The alloy was

characterized by an interdendritic network of a eutectic struc-

ture, and presumably consists of borides, carbides and austenite.

A dispersed phase was also noted within the dendrites. The

phase's composition will be determined by additional testing.

A Material Task Force meeting was held on September 28th at MTI.

Participants from NASA and USS were present. Among the signifi-

cant items discussed were: work at NASA involving the reduction

of hydrogen permeation losses by the addition of CO and COo to the

hydrogen working fluid; MTI's work on heater tube requirements and

analysis, metallography on the engine-tested heater quadrant

received from USS, piston dome failure analysis, and plans for

component fabrication and testing; USS's method for repairing

heater tubes; and the possibility of having MTI's candidate heater

tube materials creep tested at Sandvik.

3.2.5.3 Piston Rod Surface Replication

Carbon film replicas were made from plastic film impressions of

the piston rod, which were taken during the teardown of the

engine. A technique was adopted for preparing carbon film replicas

for examination by electron microscopy, which will improve the

consistency of the results. MTI is now prepared to complete the

examination of piston rod wear patterns with the high degree of

resolution provided by transmission electron microscopy. This

method of piston rod surface examination will not only provide

quantitative information on the depth of microscopic features, but

will indicate the nature of surface topography and will improve

MTI's understanding of the mechanism of piston rod seal deteriora-

tion.

-62-



3.3 MAJOR TASK 3 - BASELINE ENGINE SYSTEM (P-40)

The existing USS P-40 Stirling engine will be used as the baseline engine for

Stirling engine familiarization and as a test bed for component operating

conditions, component characteristics, and to define problems associated with

vehicle installation.

The baseline P-40 engines will be tested in dynamometer test cells as well as

in an automobile. Test facilities are being constructed at MTI to accomodate

this work.

3.3.1 Baseline Engine System (P-40)

USS will manufacture four P-40 engines, including spare parts. Engine/

dynamometer testing will include full and part power operation, tran-

sient and cyclic operation, start-stop cycles, and endurance testing.

Complete engine performance maps of fuel consumption, emissions, power,

and torque versus engine speed over the full range of engine operating

pressure levels will be obtained over the entire anticipated range of

operating heater head temperatures, conibustor flows, inlet temperatures,coolant temperatures, coolant flows, and coolant inlet temperatures.

Tests will be run with the complete Stirling engine system as designed

(with all auxiliaries installed and operating off engine power). Where

appropriate, selected auxiliaries and/or ducting may be simulated, or

compensated for. Tests will also be run with all auxiliaries removed

and their functions provided by test facilities, or compensated for.

AMG will modify an AMC vehicle for the P-40 engine, thereby gaining

experience and knowledge on the integration problems and requirements

associated with the installation of a Stirling engine in a passenger

car. Limited vehicle testing will be conducted by AMG to establishbaseline vehicle-affected engine perform ance, such as: fuel consump-

tion, emissions, and under-hood environment. The vehicle installation

and test is designed to familiarize AMG and other team members with a

Stirling engine-equipped vehicle and its performance and operation. It

will also establish baseline performance for the total program, inclu-

ding durability.

The P-40 is not an automotive designed engine and, consequently, will

primarily be useful for providing Stirling-powered vehicle integration

experience for AMG plus some limited data on vehicle performance in an

AMC passenger car.

3.3.1.1 P-40 Spirit

In the previous Quarterly Technical Progress Report, a summary was

presented of acceptance testing results for Stirling Engine No.

ASE40-8, the P-40 engine installed in the 1979AMC Spirit. Figure

3.3.1.1-1 shows the engine installed in the Spirit and Figure

3.3.1.1-2 shows the vehicle.

-63-



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-65-



As is to be expected in any new engine/vehicle system, numerous

problems were encountered and solved during the initial shake down

testing of the P-40 Spirit. The first half of July was devoted

by MTI to diagnosing these problems, correcting them by rebuilding

the engine, and verifying the corrections by power measurements on

a chassis dynamometer. The following problems were diagnosed and

corrected:

• The CapSeals

These seals were defective in all four cylinders. The

defect allows hydrogen to leak into the seal cartridges,

which in turn could cause an increase in dead volume,

out-of-phase return pressure, and partial short-circuit of

all four cylinders.

• Fuel Nozzle

The core of the atomizer nozzle was loose, which severely

resctricted the atomizing air flow.

• Combustion Air Throttle Valve

The air flow control valve was working erratically. Upon

disassembly it was found to be dirty. This imposed consi-

derable resistance to its movement, and caused the maximum

travel microswitch to lock in the full open position. This

condition results in an engine abort.

• Seals InGeneral

A cracked dome-to-piston 0-ring was found in at least onecylinder, and two cylinders had questionable piston seal

rings. There was a small hydrogen leak from the power

control valve to the atmosphere and a broken 0-ring in the

connection of the power control valve to the engine supply

line.

• Visual Inspection

. Over temperature indications were noted by rod discolora-

tion and deformed cap seals.

. One broken cap screw was found and another was locked in

place.

. Rust was noted on the cylinder walls.

. Dirt and material was found deposited on the underside of

pistons, in the piston grooves, and inside the seal

housings.

. A damaged/scored crank bearing was found in cylinder No. 3.

-66-



The following major parts were replaced:

• The bearing bushing in the connecting rod from cylinder No.3.

• All four piston rods.

• Two pistons; cylinder No. 1 and No. 2.

• All piston seal rings.

• All eight maximum and minimum check valves.

• All four cap seals.

• All four main seals using a new design which requires no

scrapers or cylinder seal oil separators, and which has the

seal space connected to the minimum pressure manifold.

After the repairs at MTI, the vehicle made a round trip from

Albany, N.Y. to Lake George, N.Y., a distance of about 120 miles.

The vehicle was returned to AMG (in Detroit) on July 19, 1979, to

resume vehicle test activities.

Late in July, tests on various fans, fan shrouds, viscous clutches,

and drive ratios were performed at AMG. The optmum fan system

appears to be an 18.5" diameter "flex" fan, no viscous clutch, a

1.1:1 fan ratio and no fan shroud. During these tests, several

problems occurred which were corrected:

• Combustion air blower bearing failure;

• Loss of throttle control (loose electrical connection);

• Loss of ignition (broken thermocouple-actuated guard);

• Fuel nozzle atomizing air holes were blocked;

• Variator drive pulley bushing slipped , causing belt slippage

and low combustion air supply. (Caused by previous

repair/modification to pulley halves.)

While making repairs, it was decided to also nake the following

modifications, to see if vehicle performance could be improved:

• Install a loose 10.75" torque converter (1250 rpm stallspeed);

• Reduce the combustion blower drive ratio (two diameters of

pulleys were made for the blower, for trial purposes);

• Install a new, unmodified, varidrive pulley with the heavier

spring;

-67-



• Incorporate an automatic fan electric clutch cutout, set at

18 mph;

• Install an 18.75" diameter flex fan with no viscous driv e

unit and a 1.2 drive ratio;

• Omit the fan shroud.

Between July 20 and August 24, 1979,AMG ran the Spirit in order

to collect the following operational and performance data:

• The speed relationship between the engine blower drive and

the vehicle crankshaft rpm was measured in order to initiate

effort to obtain a blower driv e with reduced power losses

and to optimize the variator drive system.

• The engine response time-delay was measured, at wide open

throttle (WOT), at frozen idle conditions, and at 50

atmospheres to 150 atmospheres of engine pressure. Cooling

tests were performed with v arious fan types to determine fan

rpm as a function of engine rpm, and fan performance as a

function of vehicle speed. These tests were aimed at

reducing fan power consumption.

• The adequacy of the cooling system was studied under idle

conditions. The cooling system tests scheduled in the Ethyl

Corporation Wind Tunnel will further d efine the adequacy of

the Spirit cooling system. Data were obtained with various

axle ratios and were compared to computer predictions of

vehicle simulation.

• Transmission torque converter comparisons were mad e with low

stall and high stall 10.75 in. units.

On August 24, 1979, piston rings were replaced because of poor

starting time. Rebuild was completed on August 26, and CVS

testing was started on August 27.

During Septe mber, testing and optimization continued and the

Spirit was readied for display at the October DOE Contractor

Coordination Meeting (CCM).

Engine operating time through September 30, 1979 was 139.5 hours,

and the Spirit odom eter read 1868 miles. The performance of theP-40 Spirit at the end of September is summarized in Table

3.3.1.1-1 along with a comparison to the P-40 Opel. These

performance figures are not final figures as the Spirit will

undergo additional optimization, modifications, and testing after

the October CCM.

-68-



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-69-



3.3.1.2 Mil's P-40 Engine

The pre-test documentation work at MTI on Engine No. ASE40-7 was

discontinued on June 29, 1979 in order to respond to the

investigation of the P-40/Spirit (discussed above). Effort was

resumed on July 26. 1979.

In August 1979, the documentation of ASE40-7 teardown was com-

pleted and the reassembly of the engine was started. Reassembly

was completed in September. After disassembly and inspection,

deposits/scale/rust was noted within the engine cooling system.

Surface rust and roughness were removed from the block's cylinder

walls by lapping with a micro-polishing compound. Several unsuc-

cessful attem pts were mad e to chemically remove the metallic

flaking material from the inside surface of the engine block. The

flaking was finally removed by sand blasting.

The original heater head was reinstalled and leak checked with

helium gas at 1000 psig. The helium charge decayed 27.5% in 30minutes, as shown below.

Charge Pressure Time

(psig) Hrs;Min

1000 13:29

920 13:34

900 ' 13:35

725 14:00

This leakage rate was unacceptable for operation. Two heater

tubes, Nos. 9 and 16 in quadrant No. 1, each had a mid-span

section removed and replaced with a new section prior to shipping

from USS. The new tube sections were attached to the existing

structure with furnace brazed sleeves. The leakage occurred at

the inboard sleeve of each tube. A repair replacement heater head

assembly has been shipped from USS for delivery to MTI early in

October.

3.3.2 Facilities

The test facilities and equipm ent necessary to completely evaluate

engines and components will be designed, built and procured at MTI. It

is anticipated that this will include installation at MTI of two engine

test cells with appropriate data acquisition equipment and component

test cells to be used for component development purposes.

The component test facilities will include heater system test rigs to

evaluate heater heads under simulated engine conditions. A cold flow

test rig will support this effort. A combustion facility will be

installed to evaluate new combustion system designs, and a fuel nozzle

test stand is also envisioned. A subsystem test facility will allow

coupling of the heater head/combustor/preheater in order to verify and

-TO-



test the entire subsystem. The heater system facility will be supported

by a high speed data acquisition system and an automotive exhaust

emission sampling and analyzing system.

Facilities, apparatus, and rigs will be constructed to investigate and

develop piston-rod sealing, the hydrogen compressor system, the

combustion blower, power control check valves, and the power control and

air/fuel control systems. In order to start engine testing before

completion of the primary (Phase I) facility, MTI is setting up a

portable, skid-mounted "Work-Around Facility".

Procurement of the Work-Around Facility is complete ex cept for the fuel

flow met er, which is due in October. The Work-Around Facility consists

of portable skid-mounted equipm ent containing engine cooling facilities,

dynamometer cooling, engine mounting and brake assemblies, fuel/air

supply, and the operator control equipment. These five skids are shown

in Figures 3.3.2-1 through 3.3.2-5.

All five skids were placed in their final locations and interconnected.

The three outside skids: No. 1 (Engine Cooling), No. 2 (DynamometerCooling) and No. 4 (Fuel) were covered with weather enclosures. Skid

No. 5 (Operator Control) has been hooked up to the Phase 1 facility

electric power supply. Skid assembly work is complete except for the

fuel flow meter installation and the ASE40-7 engine mounting and

hook-up.

All construction is complete for the Primary (Phase 1) Facility at MTI

except for the volt age regulators for clean-power, which are expected to

be delivered in October. The heat pumps for the control rooms and

passageways were tested, balanced , and are now operational. Prepara-

tions have begun for testing the other subcontractor installed systems.

The General Electric edd y current dynamometer was installed in theengine cell. The dynamometer cooling water tank was also installed.

Assembly of the 2,000 gallon water tank, with its associated pump skid,

was completed in the utility house. Plumbing of the water cooling

system continued as purchased hardware was received.

The programmable control cabinet, to be used for routine sequencing

functions, is 50% complete. Ad dition of the controller mainframe will

complete this assembly.

Planning for the software system generation has begun. This planning

requires hardware configuration information (which is available) and

software d ocumentation (some of which is supplied with the computersystem). Guidelines are being generated for long and short term system

operation. These guidelines will be used to design useful software

support modules for the system. Signal interconnection drawings were

prepared to aid in identifying system signals.

-71-



Figure 3.3.2-1 Skid #1 — Engine Cooling

Figure 3.3.2-2 Skid #2 — Dyno Cooling

MECHANICAL

TECHNOLOGY

INCORPORATED -72-

MTI-19



Figure 3.3.2-3 Skid #3 — Engine/BrakeAssembly

Figure 3.3.2-4 Skid #4 — Fuel/Air

MECHANICAL

TEC H NOLOGY

INCORPORATED -13-M T I- 1 9 2 7 9






Figure 3.3.2-5 Sk id #5 — Operator Control Assembly


INCORPORATEDS

HTI-19331



3.4 MAJOR TASK 4 - ASE MOD I SYSTEM

A first generation Stirling engine system will be designed, fabricated and

developed.

Engine/dynamometer testing will include full and part power operation,

transient and cyclic operation, start-stop cycles, and endurance testing.

Com plete engine performance maps of fuel consumption, emissions, pow er, andtorque, versus engine speed over the full range of engine operating pressure

levels, will be obtained over the entire anticipated range of operating heater

head tem peratures, combustor flow, inlet temperatures, coolant temperatures,

coolant flows, and coolant inlet temperatures.

Tests will be run with the complete Stirling engine system as designed (with

all auxiliaries installed and operating off engine power). Where appropriate,

selected auxiliaries and/or ducting may be simulated, or compensated for.

Tests will also be run with all auxiliaries removed and their functions

provid ed by test facilities, or compensated for. One or more engines will be

installed in a vehicle(s).

3.4.1 Heat Generating System

The heat generating system w as studied with respect to a conventional

system with EGR, and a system using CGR. The system studies have

resulted in the choice of the CGR system in preference to the EGR

system.

The combustion system was studied with respect to the by-pass v alve on

the top of the combustor. Sketches were made of two different

combustion chambers w ith diff erent heights (120 mm, 150 mm) for use in

the ASE Mod 1 to be installed in the Spirit. From the design point of

view, the 150 mm combust ion chamber is preferred, however, some redesignof the vehicle hood will be required. The conbustor is shown in Figure

3.4.1-1.

3.4.2 Preheater

A preliminary design was made of the preheater matrix (CGR system). The

number of preheater plates will be 1,200 and the plate material thickness

will be 0.15 mm. Layouts were made for two diff erent heights of the

matrices after considering combustion chamber heights. The design

allows the preheater matrix to be removed for cleaning without having to

remove the preheater housing from the engine. Tests are being performed

to braze the complete matrix. If the tests are not successful, the

brazing system used in the previous P-40 preheaters will be applied.

Air passages were tested in the USS Fluid Analysis Laboratory to

establish the flow dist ribution of the preheater housing. Effort was

also directed to the form of the insulation material for the by-pass

function of the preheated air. Presently, two different preliminary

layouts are under investigation for the total external heating system.

The air passages may be manufactured from aluminum castings, and the top

cover may be manufactured from pressed aluminum sheet or aluminum

castings.

-76-



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3.4.3 Heater Head

The heater head was studied with respect to the location of the heater

tubes in the manifold s and the vertical location of the tubes. The

heater head will be bolted with M12 (a 12mm bolt with a metric thread)

bolts. Preliminary analyses indicate the following thickness of the

housings:

Thickness Thickness

at Top (mm) Above Flange (mm)

Cylinder housing 7 4

Regenerator housing 12 5.5

The bolt arrangement will be fatigue tested while connected to the

water jacket and the duct plate.

The dimensions, form, and appearance of the air passages in the upper

part of the cylinder and regenerator housings were established. The

cylinder and regenerator center lines were moved 1 mm and 2 m m,

respectively, from the engine center line. Different procedures for

joining the manifolds to the cylinders and regenerator housings are

under investigation. The alternatives are electron beam welding and

brazing. Coordinates were established which define the geometry of the

heater tubes, and bending tools for the tubes were manufactured.

Asymmetric finite element models were set up for stress analysis of the

heater head. Different designs will be analyzed for stress

concentrations. Different cases of loading were consid ered, such as

temperature load (T), internal pressure (P), and combinations of

temperature and pressure. The results are shown in Figures 3.4.3-1,

3.4.3-2 and 3.4.3-3.

3.4.4 Gas Cooler

Gas cooler tube lengths were increased by 5 mm and a preliminary design

was made. The new design allows the 0-ring to be mounted radially. It

will ensure that the 0-ring is retained in the groove in the block while

dismantling the cooler. Two of the tested aluminum gas coolers have

fatigue cracks in the dimpled section of the tubes. New thermal

calculations will be performed with less dimpled tubes, which probably

will result in a different number of tubes per cooler unit. A redesignof the aluminum gas coolers is underway by the manufacturer and a

revised test plan is being prepared.

3.4.5 Regenerators

The regenerators' filling factor was reduced from the present 43% to

40-41%.

-78-



Loadcase I : Temperature Load T

Loadcase III : Pressure Load Pmean value

Loadcase V : T + P .

Loadcase VI : T + Pmean

Loadcase VII : T + Pmax

Figure 3.4.3-1 MOD I Regenerator House — Effective Stress in N/mm2

-19-



J IT £J3s- J?B 232

J27

3 1

I M ZL

J. VT

S39

5/

J \ .2/7-

jr iJ^! .

. £ Z Z

^/£*•

J5?3

J '

?

m _/y/

_ E 2 T

5^5-

^36

7H

W

£_

S*6

£L/&

m.s& l

K ey

Loadcase I : Temperature T

Loadcase III : Mean Pressure P

Loadcase V : T + PminLoadcase VI : T + P


2?-

M J : J Z L Y J i

Figure 3.4.3-2 MOD I Regenerator House — Effect ive Stress in N/mm2

-80-



Key

Loadcase I : Temperature T

Loadcase III : Mean Pressure P

Loadcase V : T + P ,mm

Loadcase VI : T + P


Figure 3.4.3-3 MOD I Cylinder House — Effective Stress in N/mm2

-81-



3.4.6 Cylinder Block

A duct plate proto type for strength testing was manufactured and

statically pressurized for deflection measurements. Strain gauge

measurements indicate a maximum stress of about 160 MPa. A redesign was

started in order to diminish the displacements and a fatigue test is

plannedfor the new

design.In

this test,the

duct plate willbefastened to the one-fourth water jacket.

The cold connecting duct for the cylinder block strength test (cold

engine system) was been statically pressurized for deflection measure-

ment. The central deflection was about 70 y m at a pressure of 20 MPA,

which is acceptable from the functional point of view. However, the

largest deflection at the position of the 0-ring was 34 u m. Such a

deflection is considered excessive and a revised design of the cold

connecting duct plate was manufactured and statically pressurized for

deflection measurements. The central deflection was approximately 40 Wm

at a pressure of 20 MPa. The deflection at the position of the 0-ring

was 21 pm. The new duct plate is approximately 60% stiffer than the

initial d uct plate. Aft er the deflection measurement was performed, the

duct plate was bolted to a section of the water box and sent to the

National Swedish Testing Authority for fatigue testing. Sketches of the

initial and revised duct plate are shown in Figure 3.4.6-1.

Due to the design, the cooling water circuit of the cylinder block is

practically perfect with respect to flow distribution through the two,

almost identical, parallel paths. A later flow test will quantif y total

flow resistance in the system in order to specify pump capacity. Two

pump speed options were built into the drive transmission.

3.4.7 Seals

The duct plate in the cylinder block was mod ified due to initial static

tests. A new sample for fatigue tests has also been cast. Further

minor modifications will be made to match adjacent parts (mainly the

0-rings) and to integrate it with the cylinder liners. The main seal

system d esign was finished.

j.4.8 Cooling System Development

The Cooling System Task Force met in Sweden in September, and they

visited several Swedish automobile radiator manufacturers: Granger

Radiator Division of Svenska Metallverken (Finspang, Sweden) and

Blackstone (Solvesborg, Sweden).

Granges Metallverken is the world's largest prod ucer of copper strip

used for the fabrication of radiator fins (automotive type construc-

tion). They also design and dev elop automated equipment for radiator

fin fabrication. Presently, Granges is competing for some Ford business

and a specific Ford production radiator is targeted. This radiator has

a single row of fins, which results in a lighter design and a more

efficient use of the copper. It is the opinion of the Task Force that a

minimum of two Granges radiators should be evaluated as possible

candid ates for the Mod I cooling system.

-82-



Initial Duct Plate

Revised Duct Plate

Figure 3.4.6-1 Initial and Revised Duct Plate

-83-



Blackstone (Sweden), a licensee of Blackstone USA, produces radiators

for Volvo on a highly autom ated production line. On a lower production

basis, truck and off-highway equipment radiators are produced. They are

also engaged in a limited production activity for aluminum truck

radiators. Blackstone has no prod uct development activity and ,

therefore, is not a potential source for high heat transfer cores.

However, they have a test facility for characterizing radiators and haveagreed to perform tests for us on competit ive equipment. They can

accom mod ate two radiators per day. Radiator characterization data will

also be supplied to USS for computer code refinement.

AMG and MTI attended three major meetings:

• Task Force Meeting (Malmo, Sweden).

• Granges Radiator Division, Svenska Metallverken (Finspang,

Sweden) to review a high heat transfer radiator core.

• Blackstone (Solvesborg, Sweden) for a tour of theirfacilities.

As the result of these meetings, it was agreed that the core offered by

Granges is a viable candid ate for the ASE Mod I cooling system, and that

Blackstone facilities will probably be employed for characterization

curves of candidate cores.

The P-40 mock-up will be installed in the Concord Cooling System Test

Rig Vehicle and air mass flow measurements will be recorded. These

measurements will be across the radiator core at various air speeds and

ambient temperatures. A redesign effort on the front of the Concord

will also start. The objective of this effort is to increase the core

frontal area of the radiator and also increase its unobstructed frontal

area for impact air. An air scoop and dams will be considered.

3.4.9 Piston/Piston Rod Assembly

The type and d imensions of the sliding seal system were determined.

Adjustments will be mad e after further testing. The type of crosshead,

piston/piston rod attachment for the piston rod assembly, and their

dimensions, were d eterm ined. More analysis is needed for the static gas

seals and the piston ring function. These possible revisions might add

some length to the overall engine height. In order to reduce total

engine height, a relatively large cone was made in the lower end of the

piston. The design of the piston is still in progress, and the design

of the piston dome was finished. The piston rod design was finished and

an integral crosshead was chosen.

The gap between the dome and the cylinder was tested and a report is

being prepared. Testing indicated that an increased gap detrimentally

affected the engine power and efficiency as well as the 0-ring seal, due

to high temperatures in the lower region of the cylinder wall.

-8U-



3.4.10 Engine Drive System

The design of the engine drive system was evaluated at a meeting with

Ricardo. Two sets of different gears will be supplied by USS for drive

system No. 1 and 2.

The engine drive system was redesigned to comply with the cylinder and

regenerator housing changes. The design of the bed plate will remain

unchanged. Some minor mod ifications are still incomplete, for instance:

the interface between the bed plate and the cylinder block, the

placement of the oil stick, etc. The external profile of the oil sump

will be defined at a later date with respect to the installation in the

vehicle.

A contract supplement was made with Ricardo, which includes the design

and manufacture of a test rig for the flywheel, starter adap ter, engine

mounting brackets, and clutch arrangement. Delivery of the first drive

unit is expected by June 1,1980.

3.4.11 Air/Fuel System

The burner for the air/fuel system has been mod ified. Mock-up parts

were ordered and full scale installation drawings have begun.

3.4.12 Auxiliaries

The layout of the auxiliaries was studied in detail and are being

modified according to the new design of the components, such as the

preheater and the cylinder block.

3.A.13 Flow Distribution Tests

The design of the test objects was completed. Testing in the Fluid

Dynamic Laboratory was begun in October. Figure 3.4.13-1 shows the air

preheater flow distribution test rig and Figure 3.4.13-2 is a photograph

of the rig.

3.4.14 Joining Techniques

Brazing techniques and electro beam welding techniques will be tested on

regenerator housings. Manufacture of cylinder housings were delayed and

parts are expected to be delivered in October. These joining techniqueswill form the basis for the manufacture of test pieces for endurance

testing. Testing is due to start in October.

Brazing tests will be performed on a complete heater matrix using 0.3 mm

plates instead of the planned 0.4 inn plates. Figures 3.4.14-1 and

3.4.14-2 show the test brazing equipment.

3.4.15 Power Control

The check valve test rig has been operating for a total of 2010 hours.

Tests with the Bauer KB 057909-080 check valve were terminated after

-85-



c0

o

.0

OJ

t s0)

a;

C OI00

C fl

idu

-86-



Figure 3.4.13-2 Air Preheater F low Distribution Test Rig

-87-WII-19558



Figure 3.4.14-1 Fixture fo r Brazing the Preheater Matrix

3 0 7 7 1

-88-



Xk _

4-

re

k _0)•03(L )

JZ0)

o

l/l0)

O J Dc

'N05k _C O

(N

rn

OJ

D00

-89-



operating for 600 hours; the valve functioned well and no valve failure

occurred.

A standard, "off the shelf", SKF-manufactured electrical actuator was

procured. The actuator has the correct force but the response is too

slow. USS is waiting for a reply from SKF on their request to develop aunit with a faster response. The actuator will be used for developing

the control circuitry and for driving the test units of the spool

valve.

MTI and USS personnel visited Valcor, Inc. The problems involved with

solenoid valve operation in the Stirling engine control system were

thoroughly discussed . Valcor showed a positive interest to engage in

development work on solenoid valves for the Stirling engine control

system.

All parts of the hydraulic test rig were delivered and the rig is now

being assembled.

3.4.16 Air Blower

A complete combustion air blower was tested for noise level, capacity,

and efficiency. Figure 3.4.16-1 is a performance map of the belt driven

Flaff blower and Figure 3.4-16-2 is the performance map of the gear

driven Sunflo blower. The differences in efficiency and capacity depend

on the measuring eq uipment used, but it is felt that the results were

satisfactory. The blower has operated for approximately 25 hours with no

problems. A noise level test was made with four different flat belts.

Endurance testing and cold start testing will be performed later.

Figure3.4.16-3

is a phot ograph of the combustion air blower variator,and Figure 3.4.16-4 shows the results of the noise test.

3.4.17 Atomizer Air Compressor

The test with a modified compressor revealed that the layer of Teflon on

the end plates was not enough to avoid failure. A misalignment between

the shaft and the compressor housing was discovered and corrected , but

did not solve the problem. A number of possible solutions will be

tested to try to solve the problem. Figure 3.4.17-1 shows the atomizer

air compressor with the servo oil pump.

3.4.18 Stirling Engine System

Computer predictions were made for the preliminary version of ASE Mod I.

The dimensions are shown in Table 3.4.18-1. Table 3.4.18-2 shows the

preliminary, calculated ASE Mod I values for indicated power and

efficiency. The preliminary computer predicted dimensions, are being

continuously upd ated . Minor revisions are expected to take place before

a final version will be established.

-90-



Figure 3.4.16-1 Performance Map of the Flaff Blower

-91-



Figure 3.4.16-2 Perform ance Map of the Sunflo Blower

-92 -



Figure 3.4.16-3 Co m bustion Air Blower Variator

-93-

MTI-19560



' ' _ C o _ # * P H _ S _ £ J O * at/* A.

r'-''-'irr ^ âr -_29O5_22. ^7_

___.

K"-..":-

=?=F -J^

Figure 3.4.16-4 Results of Combustion Air Blower Noise Tests

-9k-



Figure 3.4.17-1 Atomizer Air Compressor with Servo Oil Pump

-95-KTI-19564



Drive Mechanism and Cylinder!

Piston diameter

Piston rod dlaaeter

Displacer d o m e height

Cap dlsplacer dome-cylinder vail

Crank radius

StrokeConnecting rod length

Swept voluae

Regenerator (Cauxe type)

Units per cycleD l ameter

Top cross section area

Length

Wire diameter

Filling factorWeight per engine

Cooler

Units per cycle

Tubes per cycle

Inside tube diameter

Outside tube diameter

Length of one tube

Effective length of one tube

Heater

Tubes per cycle

Inside tube diameterOutside tube diameter

Length of one tubeEffective length of one tube

Heat flux at full load, inner surface

68

15

120

0.417

34

95

123.5

180

50.27

SO

0.0543

3.5

1451

1

2

87

75

24

34.5

270 .

243

78

anm aon

m aaa

m a

m a

ca3

mcm

3

ran

m m

I

kg

m m

mm

mm

HU B

m am am mm a

W/cn .2

Connecting Duct Cylinder

Cooler

Volume 40 cm3

Cross section area (narrowest passage) 4. 57 cm2

Regenerator

Volume 2.5 cm3

Length 0.5 na

Heater

Volume 24 cm3

Cylinder - Connecting Duct Heater

Volume 11.5 cm3

Cylinder

Clearance volume exp. space 3.6 cm3

Clearance volume comp. space 3.4 cm3

Table 3.4.18-1 Preliminary ASEMOD I Dimensions

HKCHAMCAL

TECHNOiOOT

INCORPOH»T£D



Ind pe—r («)

411 POVI •

111 POVI >

411POVI -

4)1 POVEI •

4)1 P O U E I •

411P4VI •

411P9VEI "

4)1 POVEI -

4)1PBVfl -

411 P

4)2 P O K E ) •

432 POVEI •

432 POVEI -

1)1 POVEI *

4)1 POVCI •

4)1 POVI -

1)2 P9VEI -

412 POVEI •

43 7 Povra •

4)2 POVII •

412 POVEI •

1)2 POi/'l -

4)2 POVEI •

•4)2 POVEI •

132 POUEI •

432 POVEI "

412 POVEI -

412 POVEI -

412 POVEI •

1)2 POVII •

4)2 POVfl .

412 POVEI -

411POVCI -

41POVEI •

412 POVEI •

431 POVEI -

4)2 POVEI •

432 POVEI •

432 POVEI •

432 POVl •

1)2 P O W E I •

431 POVI •

412 POVI •

4)2 POVCI •

411PIVEI •

411POVEI •

41POVI •

1.1074*01

6.1431*0)

..0*44*03

7.72*1>0>

»1147*01

1.0224*04

1.1025*04

11411*04

4.37*1*03

14711*01

1.22*7*0*

1.5717*04

1.1*11*04

2.1417*04

2.1*33*04

2.3245*04

*4713*03

1.2315*04

1.1217*04

2.3474*04

2.3713*04

).2)41*04

3.5754*04

1.1347*04

1.3141*0)

1.4414*04

2.4010*04

).100**04

).7)25*04

4.2140*04

4.74)7*04

5.0*50*04

1.0301*04

2.0)31*04

7. •.34.04

3.1151*04

4..1»3>04

5 1013*04

5.54*3.04

t.1047*04

1.7444*04

1.3212*04

4.5517*04

5.4*40*04

«.2450*04

4.*511*0<

7.4424*04

Moff ci«"CT Newp

452 (Tt

452 IT

152 ETI

452 (1*

451 Ell

451 (T

451 ETI

452 CTI

452 (Tl

45 2 CT t

432 ETI

432 lit

432 ETI

152 CTt

452 ITI

451 (Tl

452 CT I

452 IT!

452 CTI

452 ITI

452 (Tl

452 (Tl

452 CT I

452 (T

452 (Tl

452 ETI

452 ETI

452 ETI

432 ET I

132 ETI

437 ETI

452 ETI

432 (Tl

432 (Tl

451 (Tl

451 (Tl

451 (Tl

451 CTI

451 CTI

451 CTI

451 CTI

151 CTI

151 CTI

431 (Tl

451 CTI

431 CTI

451 CTI

- 2. 004-01

. 3).7137-01

• 4.0)74-01

• 4.15*1-01

• 4.1441-01

• 4.0*11-01

• .«4?*-01

• 1.7775-01

• 1.1115-01

• *.441*-01

- 4.4414-01

• 4.*04*-01

• 4.4512-01

- 4.5411-01

• 4.4212-01

• 4.2542-01

• 4.2420-01

- 4.7251-01

• 4.1174-01

• 41473-01

.47IM01

• 4.1701-01

• 4.5)41-01

• 4.13*2-01

• 1.4077-01

• 4.*.454-ni

• 4.*35»-01

• 4. '060-01

» 4.1224-01

• 4.7013-01

• 4.55)4-01

• 4)7)»-01

• 4.04)1-01

• 4.441*-0!

• 4,»73)-01

» 4.*2)*-01

- 4.I27*-01

• 4.4*73-01

- 4.5407-01

• 4.3541-01

• 4.7477-01

• 4.««03-01

• 4.V17I-01

• 4.1157-01

- 4.47*1-01

• 4.31)1-01

- 1114101

217 Pn

117 •••

117 Pn

117 PI*

117 pin

117 PIP

117 POP

117 Pn

117 Pn

117 PIP

217 PI»

217 PIP

217 pin

217 Pn

217 PIK

117 PI"

217 pin

217 PIP

217 Pn

217 Pn

217 PIP.

217 p«n

717 pin

217 pin

117 pin

217 pin

217 Pn

217 Pn

217 Fn'

117 pin

. 217 Pn

117 FR

117 pin

117 PI*

117 pin

217 Pn

117 PIR

• 217 PI*

217 Fn

117 Pn

117 p«n

117 PIP

117 F»n

117 Pin

117 Fin

117 Fin

117 Fin

rvMr* IP*)

- 1.5000*0*

• I.500O*0*

• t.5MO*0*

• 1.5000*0*

• 2.5000-06

* 1.5000*04

• 1.5000*0*

- 1.5040*0*

- 5.0C00.04

• 5.0000*0*

• 1.0000*0*

• 3.0000*0*

• 3.0040*0*

• 3.0040*0*

> 5.0000*0*

• 3.0000*0*

• 7.5000*0*

• 7.5000*0*

• 7.5000*0*

• 7.3000*0*

• 7.5000*0*

• 7.5000*0*

• 75000*04

• 7.3000*04

• 1.0000*07

• 1.0000*07

• 1.0000*07

• 1.0000*07

* 1.0000*07

• 10000*07

• 1.0000*07

• 1.0000*07

• 1.25CO*07

• 1.2500*07

• 1.1300*07

• 11300*07

• 1.2500*07

• 1.7500*07

- 113CO*07

> 1.J5CO-0?

- 1.3000*07

* 1.3000*07

• 1.5000*07

> 1.5000*07

• . ).5000*07

• 1.5000*07

• 15000*07

- 1.3000*07

HMV

H IIV

HICV

111 111

111 ICV

211 OEV

HIEV

HIEV

111 IEV

211 I(V

211 ICV

IIIIIV

211 IEV

211 IEV

211 IEV

211 MY

211 ICV

211 IEV

211 ICV

HI IEY

211 IEV

HIEV

111If*

111 IEV

HMY

HIEV

211 IEV

211 IEV

211 KV

HICV

IIIKV

111 ICV

211 IEV

H KV

111KV

H KV

H KV

111 1C*

H 1C*

H1C*

111 KV

H ICV

H KV

H KV

H 1C*

H KV

H 1C*

H KV

n-

• 1.0000*01

• l .OCOC-03

• 1.3000*03

• 1.004C*0)

> 2.3000*03

• 3.001C-03

• 1.5000*0)

• 4.000C*0)

* 3.0000-02

• 1.0000*0)

> 1.1000*0)

• z . c e o o - 0 3

' 1.300C*03

• 3.0040*0)

• 3.5000*0)

• 4.0COC-01

> 3.0000*02

• 1.0000*01

• 1.3000*0)

• 1.0040*0)

- i.3eoe*o)

> 3.0000-03

• ).3000*03

• 4.0000*0)

• 5.0000*01

• l .OCOC-03

- 1.5000*0)

» 2.0000*0)

• 2.5000*03

• ).0000*03

- 3.5000-03

• 4.BOOO-03

• 3.0COO*07

• 1.0000-0!

'13000-01

• 2.COOO-01

• 11000*01

• 3.0100-0!

• 1.3000*0)

• *.«onc*oi

• 3.0000*02

* 1.0000-0]

• 1.3000*0)

- 1.0000*0)

• 1.5COO*03

• I.OCOO-OI

• 3.3000*0)

• 4.0001*03

Table 3.4.18-2 Preliminary Calculated MOD I Values for Power and Efficiency

-97-



Table 3.4.18-3 contains the calculated net power (in Watts) and the net

efficiencies as a function of mean pressure and rotational speed. The

calculations used hydrogen as the working gas,a heater tube temperature

of 720°C, and cooling water temperature of 50°C. The friction and

auxiliary power requirement used to perform the net power calculations

are shown in Table 3.4.18-4 at two operating points: full load,

P = 15 MPa,and 4000 rpm; and part load, P = 5 MPa,and 2000 rpm. The

radiator fan power was not included in this calculation.

-98-



*L po.«r (V)

Il

111

(4.0 rtrr • ?.*:|3t*0<

44 > f . f f - 3.?20«*D(

Tab le 3.4.18-3 Ca lculate d Net Power and Net Efficiencies of the MOD I Engine as a Function o

Mean Pressure andRotational

Speed

-99-



FULL LOAD

INDICATED POWER

FRICTION

AUXILIARIES

NET POWER

EXT, HEATING EFFICIENCY

NET EFFICIENCY 29.1 I

PART LOAD

INDICATED POWER

FRICTION

AUXILIARIES

NE T P01VER

EXT. HEATING EFFICIENCY

NET EFFICIENCY 29.1 \

Table 3.4.18-4 Friction and Auxiliary Power Requirements Used to Perform Net Power Calculati

-100-



3.5 MAJOR TASK 5 - ASE MOD II SYSTEM

The second generation engine will be designed, fabricated and tested as an

"experimental" engine system. It will be power rated according to the

reference engine system studies, using the first generation engine system as

the basis for improvement. The prime objective will be to upgrade the first

generation engine system to improve efficiency, and to improve durability and

reliability.

Only high confidence level component and subsystem developments will be used.

The design will reflect the use of automotive engineering design and

fabrication techniques to the max imum extent possible. Emphasis will be on

performance and durability/reliability.

Engine/dynamometer testing will include full and part power operation,

transient and cyclic operation, start-stop cycles, and endurance testing.

Complete engine performance maps of fuel consumption, emissions, power, and

torque, versus engine speed over the full range of engine operating pressure

levels, will be obtained over the entire anticipated range of operation,

heater head temperatures, combustor flows, inlet temperatures, coolanttemperatures, coolant flows, and coolant inlet.

Tests will be run with the complete Stirling engine system as designed, with

all auxiliaries installed and operating off engine power. Where appropriate,

selected auxiliaries and/or ducting may be simulated, or compensated for.

Tests will also be run with all auxiliaries removed and their functions

provided by test facilities, or compensated for.

Automobile/engine testing will be performed in order to establish

engine/vehicle interaction and engine-related driveability, fuel economy,

noise, emissions, and durability/d riveability.

3.5.1 Endurance Test on P-40 Engine (ASE40-4)

At the end of the last quarter (as stated in the previous Quarterly

Technical Progress Report), after 1093 hours of testing at 820°C, the

engine ex perienced a heater tube failure in the third quadrant. The

failed tube was replaced and engine testing was resumed in early August.

After nine hours of operation, the engine was stopped due to hydrogen

leakage in the heater. The leak was located at the manifold on cylinder

No. 3 and at the brazed joint between the tubes and the manifolds.

Figures 3.5.1-1 and 3.5.1-2 show the failure (crack). After the engine

was again repaired, testing resumed. An hour and a half later, a new

leak developed at the same location, and testing was again stopped. TheP-40 endurance engine is shown in Figure 3.5.1-3.

A new Multim et N-155 heater, which contains a metallic flame shield made

of Kanthal (a special high temperature material), and a new preheater,

were fitted to the endurance test engine. After running the engine for

approximately 33 hours, a cyclic high temperature test was initiated on

the Multimet N-155 heater head. After approximately 63 hours of

operation, two bolts in the regenerator housing failed. The bolt

failure is under investigation.

-101-



cro

-DO J

_*urei_U

tn

ro

S!D00

-102-



Q J

•5DO

ECu

c

c

o

LO

"oM—

"E

2-ov

u

u>-(—

o4->

cc u

EO J00

JSc

I

iri

< U

00

-103-






Fig ure 3.5.1-3 P-40 End uran ce Test Engine

-105- [-19563



The total operating time of the endurance engine reached 1200 hours.

3.5.2 Annular Regenerator

Design work for the annual regenerator for the endurance engine

(ASE40-4) is completed and manufacturing of parts has begun. The

assembly of the engine is in progress. Figure 3.5.2-1 shows the annularregenerators which surround each cylinder. The heater for the annular

regenerator concept is shown in Figure 3.5.2-2 and Figure 3.5.2-3. The

bottom of a heater quadrant is shown in Figure 3.5.2-4. Figure 3.5.2-5

shows the engine mounted on the test rig. The regenerators and coolers

are not yet available.

The annular regenerator concept provides identifiable benefits relative

to the external regenerator design currently utilized in the existing

engines. This design, as its name implies, wraps the regenerator, in

annular fashion, around the cylinder head instead of placing this

component in a separate chamber outside the block outline of the

cylinders. Figure 3.5.2-6 illustrates this concept and compares it to

regenerators in the P-49 engine. This provides the potential for both a

decrease in engine size and weight due to reduction of the engine

envelope. The envelope reduction allows the heater head to decrease in

size, since the discharge side into the regenerator can be reduced in

diameter. This in turn provides the potential for reducing the diameter

of the combustion chamber/preheater components.

3.5.3 Seal Development Test Rig No. 1

After the Seal Development Test Rig No. 1 ran for 226 hours, the gas

compressor wrist pin bearings wore out and were replaced. Oil was found

on the top side of the diaphragms which are shown in the diaphragm seal

drawing, Figure 3.5.3-1. An excess amount of oil was also found in the

Deltech 115E filter, which indicated that the oil-drain capacity of the

seal system was too small. The drainage capacity was improved by

drilling bigger drain holes and by minor plumbing changes. The whole

test rig was then cleaned and the filter was replaced. In spite of the

problems with the test rig itself, no diaphragms have ruptured due to

fatigue. Figures 3.5.3-2 shows two views of the test rig.

The compressor check valve spring had to be replaced twice, and the

Vespel back-up ring in the compressor piston ring set was also replaced.

The compressor piston ring failure was probably due to foreign particles

emanating from pieces of a broken check valve spring. Excessive gas

leakage was noted for a period of time. The sliding rod seal was

replaced, but the leakage rate continued to be excessively high.

Further investigation showed a leak in the plumbing, which was then

repaired. Total test rig accumulated running time reached 441 hours on

September 30th.

-106-



Figu re 3.5.2-1 P-40 with Annular Regenerator-Type Heater — Regenerators Shown

-107-MTI-19561



Figure 3.5.2-2 P-40with Annular Regenerator-Type Heater, One Quadrant Removed

-108-

MTI-195



Figure 3.5.2-3 Close-up View of Annular Regenerator-Type Heater Mounted

on the P-40 Engine

MECHANICAL

TECHNOLOGY

INCORPORATED

-109-KTI-19387



Figure 3.5.2-4 Annular Regenerator-Type Heater, Underside View of Quadrant

MECHANICAL

TEC H NOLOGY

INCORPORATED-110-

MTI-19



Figure 3.5.2-5 Annular Regenerator-Type Heater and P-40 Engine Mounted on Test Skid

-111-

MTI-19388



Endurance Engine

Figure 3.5.2-6 Cross Section of Annular Regenerator in the Endurance Engine (ASE-40-4) asCompared to Cross Section of Regenerator in a P-40 Engine

-112-



Piston

Kapseal

Rod

Rubber Diaphragm

Oil Scraper

Hydrogen Seal

7 9 2 7 5 7

F i g u r e 3.5.3-1 Dia ph r a g m Seal Concept

-113-



Figure 3.5.3-2 Diaphragm Seal Test Rig

-llU-

MII-199



3.6 MAJOR TASK 6 - PROTOTYPE ASE SYSTEM STUDY

This task will commence in the 1982-83 time period, and will consist of

studies concerned with bringing the ASE from its expected state of development

in September, 1984, to the start of production engineering.

-115-





3.8 MAJOR TASK 8 - TECHNICAL ASSISTANCE

Technical assistance to the Government, as requested, will be provided

pursuant to the Technical Direction Clause of the contract. This effort will

include: Stirling engine and/or vehicle systems for DOE/NASA demonstration

purposes; models and displays for use at Government and professional society

technical meetings; computer program assistance to evaluate various NASAspecified engine modifications, parametric engine variations and engine

operating modes; training of personnel in the operation, assembly and

maintenance of Stirling engine systems and vehicles delivered to NASA;

appropriate communication media including brochures, audio-visual materials,

other literature, etc.

MTI has ordered and received a permanent display unit for use at technical

meetings and expositions. Plans are currently underway to use this display

for the October CCM in Dearborn, Michigan. The theme of this meeting will be

"Component Development". The P-40 Spirit and P-40 Opel will be on display and

available for demonstration rides. Technical papers will be presented by

MTI, USS, AMG and Ricardo.

Other effort under this task included:

• Photography, display materials and brochures for handout at the October

CCM.

• Repair of minor electronic damage to the P-40 Opel caused by a wiring

short circuit which occurred on September 18th.

• Renting a booth for the SAE mppfing in February 1980 in Detroit.

• Providing DOE with a versatile and portable display for use in theWashington, D.C. area.

• Design of an interlock system for the hood of the P-40 Opel and P-40

Spirit, and order of all hardware.

• Technical support to NASA for the disassembly and reassembly of the NASA

P-40 engine (ASE40-1).

-117-



3.9 MAJOR TASK 9 - PROGRAM MANAGEMENT

This task defines the total program control, administration and management,

including reports, schedules, financial activities, test plans, meetings,

reviews, seminars, training, and technology transfer.

Task elements include:

• Program management.

• Technical direction.

• Monitoring of technical and financial progress.

• Report preparation, publication and distribution.

• Preparation of test plans, work plans, design reviews, etc.

• Coordination of monthly m eetings, review meetings, etc.

• Transfer of technology to the United States.

• Training of personnel.

• Seminars and technical society presentations.

• Government meeting coordinations and presentations.

• Engineering drawings and installation, operation and maintenance

manuals.

• Product assurance.

• Other items related to overall program management and control.

Effort continued at MTI on the cost proposal and work plan for the modified

program. Several meetings were held with NASA to further define the program

against projected funding guidelines. A new Statement of Work (SOW) was

received from NASA and will go into effect through a unilateral change order.

MTI is preparing the cost proposal to correspond to this SOW.

Agreement was reached with NASA regarding the rapid reporting of discrepancies

,-jnd failures of components, parts, assemblies, subassemblies, and engines. A

Discrepancy Notice will be completed and submitted to the Manager of Product

Assurance (at MTI) whenever an integral part of the system does not comply

with the intended configuration, fit, or function.

A Failure Notice and Analysis Report will be completed and submitted to the

llanager of Prod uct Assurance (MTI) whenever a system, subsystem, component, or

part fails to perform its intended function during testing, operations, or end

use.

-118-



A program quarterly review,which was held at USS (Malrao, Sweden) on August

21-23, was attended by MTI/AMG/USS/NASA.

On September 12 and 13, an in-depth review of USS Product Assurance status was

conducted by MTI. Final preparation of the program Product Assurance Plan

will resume after the October CCM. The ASE Product Assurance Manager is now

committed to devote more time to complete the required product assurance

plans, direct their implementation by the subcontractors, and to perform

subsequent audits.

-119-






RKMD

A P P E N D I X A

S T I R L I N G E N G I N E

D R I V E SYSTEMS TEST RIG

PROGRESS REPORT

H I G H W A Y V E H I C L E SYSTEMS

CONTRACTORS CO-ORDINATION M E E T I N G

23 - 25 OCTOBER 1979

HYATT REGENCY DEARBORN HOTEL, D E A R B O R N , M I C H I G A N

AUTHORS A.R.CROUCH/V.C.H.POPE

R I C A R D O CONSULTING E N G I N E E R S LTD.

B R I D G E WORKS

SHOREHAM-BY-SEA

SUSSEX

This presentation is sponsored by the U.S. Department of Energy

-121-•






A C K N O W L E D G E M E N T

T h e work reported i n t h i s presentation w a s performed b y Ricardo

C o n s u l t i n g Engineers Ltd., a s sub-contractor t o K B U n i t e d S t i r l i n g

(Sweden) & Co., who themselves are sub-contractors to M e c h a n i c a l Technology

I n c o r p o r a t e d , 368 Albany-Shaker Road, Latham, New York 1 2 1 1 0 . Mechanical

Technology Incorporated i s t h e Automotive S t i r l i n g Engine Development

Program p r i m e contractor t o t h e National Aeronautics a n d Space

A d m i n i s t r a t i o n ' s Lewis Research Center, Cleveland, Ohio M135. under p r i m e

c o n t r a c t No. DEN3-32. The program is part of the U.S. Department of Energy,

D i v i s i o n o f Transportation Energy Conservation, Heat E n g i n e Highway V e h i c l e

Systems Program.

p a s t \






raoiuONSII HN(. tN..INI I »

A B S T R A C T

T h i s is a review of'the work in progress to achieve a quieter

c o u p l i n g arrangement between the two crankshafts and the main d r i v e shaft

i n the 'U' form S t i r l i n g powered engine. Knowledge gained from t h i s

i n v e s t i g a t i o n w i l l b e incorporated into t h e design o f M O D 1 a n d M O D 2

engines which are part of the overall program.

An e x i s t i n g P40 U n i t e d S t i r l i n g engine has been adapted as a test

u n i t t o accept a l t e r n a t i v e gear forms, w i t h p l a i n a n d r o l l i n g contact

bearings, a twin l i n k driv e, a d elta plate drive and a chain drive.

The engine conversion, the test rig i n s t a l l a t i o n and noise

m e a s u r i n g equipment a r e described.

T h e t e s t program started i n J u l y 1979, i s progressing a s p l a n n e d

a n d w i l l be completed by March 1980. To date the noise l e v e l s of ^

d i f f e r e n t gear forms have been measured, mounted i n both p l a i n a n d r o l l i n g

contact bearings. Gears w i t h very s m a l l teeth (0.8 module) gi ve the

lowest noise l e v e l at speeds below 30 rev/sec, and there is l i t t l e - noisel e v e l dif ference between the p l a i n and b a l l bearings for these gears. The

results obtained are for comparative purposes only and cannot be related

t o v e h i c l e d r i v e - b y levels.



REASONS FOR TEST RIG

T e c h n i c a l Support f o r M O D 1 Design

M O O 1 i s t h e f i r s t S t i r l i n g engine t o b e designed w i t h i n t h e

Automotive S t i r l i n g engine program. I t i s s p e c i f i c a l l y designed f o r

automotive use and the f i r s t engine is scheduled to be ready for test in

e a r l y 1981.

The short tim escale allowed for the design of MOD 1 necessitates

the use l a r g e l y of e x i s t i n g technology. Hence the design of MOD 1 was

based i n concept o n t h e successful P b Q engine produced b y United S t i r l i n g ,

Sweden.

T h e P ^ t O engine h a s four pistons i n a square configuration which

actuate t w o p a r a l l e l crankshafts. Each crankshaft i s f i t t e d w i t h a gear

w h i c h d r i v e s a c e n t r a l common output shaft. The t w i n crankshaft systemi s sometimes referred to as a 'U' configuration.

The PÔ engine however was designed for use m a i n l y as a research

and stationary engine. When t h i s design concept is used for automotive

a p p l i c a t i o n , t h e r o t a t i o n a l speed i s increased w h i c h tends t o increase

t h e drive t r a i n noise. Although t h e engine when i n s t a l l e d i n a c a r c a n

be completely satisfactory from the passengers' point of view, the gear

noise may be apparent outside the vehicle.

D r i v e System Noise Red uction

The geared system which couples the t w i n crankshafts to the output

c r d r i v e n shaft tends to be (subjectively) the predominant noise, as thecontinuous combustion system and S t i r l i n g cycle gives a smoother rate of

change of pressure than the i n t e r n a l combustion engine and therefore the

S t i r l i n g engine generally i s comparatively q u i e t .

The gear noise may be l a r g e l y caused by the c y c l i c nature of the

i n p u t load. Each crankshaft has two crankpins at 90° to each other, and

t h e crankshafts a r e phased t o give equal o v e r a l l f i r i n g i n t e r v a l s . Thereforeeach crankshaft and gear has a d r i v i n g and d r i v e n period d u r i n g one revolution.

When f i t t e d w i t h h e l i c a l gears t h e crankshafts a n d d r i v e shaft tend

t o move a x i a l l y w i t h respect to each other d u r i n g a cycle. There is also a

separating force between mating gears.

The drive system is then a unique combination of the geometrical

r e l a t i o n s h i p of the gears and p e c u l i a r c y c l i c torque i n p u t .

D r i v e Systems Test Rig Proposal

A test rig was therefore proposed to be representative of the MOD 1

e n g i n e and on which a l t e r n a t i v e crankshaft c o u p l i n g systems could be f i t t e d

and their noise l e v e l s measured.

A P * » 0 engine was used, to which a l t e r n a t i v e gear forms, l i n k s , a

p l a t e and a chain d r i v e could be fitted. For c y c l i c speed r e g u l a r i t y and

expediency for t e s t i n g , the engine was motored and was fitted w i t h dummyhaads pressurised with h e l i u m to s i m u l a t e the c y c l i c torque from an actual engin

-126- •



• N S l l l »M Nl.lh. I H-.

BENEFITS AND LIMITATIONS

BENEFITS FRCM TEST RI G

S u b j e c t i v e l y lower noise l e v e l s w i l l b e obtained f o r t h e d r i v e

system i n t h e a l r e a d y q u i e t S t i r l i n g engine.

M e a s u r e d noise l e v e l s w i l l b e obtained f o r a l t e r n a t i v e gear

tooth forms.

Measured noise l e v e l s w i l l b e obtained f o r alternative p l a i n a n d

r o l l i n g contact b e a r i n g s .

Measured n c s e l e v e l s w i l l b e obtained f o r a l t e r n a t i v e l i n k , c h a i n o r

p l a t e d r i v e s .

L I M I T A T I O N S OF TEST RlG

I t must be noted however that all the noise level are for

comparison w i t h each other only

- they are not absolute

- they are not measured on a powered engine

- they are not measured in a vehicle and cannot be compared

with current vehicle drive-by noise levels in any way.

-127-



RI^RDCCOMSUI UNO > NGIN' I 1 •

ADVANTAGES OF THE U CONFIGURATION

T h e S t i r l i n g c y c l e , a s d e v e l o p e d b y U n i t e d S t i r l i n g , r e q u i r e s e a c h

of the f ou r p i s t o n s to be p h a s e d at 90° w i t h r e f e r e n c e to the a d j a c e n t

p i s t o n . B y h a v i n g t h e c y l i n d e r s p a r a l l e l t o e a c h o t h e r w i t h a t w i n

c r a n k s h a f t s y s t e m , t h e h e a t e r h e ad d e s i g n i s s i g n i f i c a n t l y s i m p l i f i e d

c o m p a r e d w i t h a Vee c o n f i g u r a t i o n , and becomes m o r e a m e n a b l e to m a s s

p r o d u c t i o n t e c h n i q u e s .

-128-



U FORM ENGINE

Courtesy KB U n i t e d S t i r l i n g (Sweden) AB £ Co

-129-



R K 3 R D OCONSULTING CNOWUM

T E S T U N I T

The test u n i t is based on a PkQ crankcase, m o d i f i e d to accept new

crankshafts, m a i n d r i v e shafts, front and r e a r spacer p l a t e s and a sump

adaptor p l a t e .

A l t e r n a t i v e gears and a c h a i n d r i v e may be f i t t e d at the d r i v e e n d .

A t w i n l i n k d r i v e a n d d e l t a p l a t e d r i v e m a y b e f i t t e d a t t h e free

e n d .

The d r i v e end space p l a t e a l l o w s b a l l b e a r i n g s or a n g u l a r contact

b e a r i n g s (to control end float) to be t e s t e d w i t h the m i n i m u m of r e b u i l d

a s a l t e r n a t i v e s t o t h e o r i g i n a l p l a i n b e a r i n g s .

O i l jets spaced a t s t r a t e g i c p o s i t i o n s a l l o w o i l t o b e d i r e c t e d

i n t o the gear mesh or the e x i t face, by e x t e r n a l l y mounted control t a p s .

T h e crankcase assembly i s f i t t e d w i t h ' d u m m y1

heads p r e s s u r i s e d

w i t h h e l i u m , t o s i m u l a t e t h e c y c l i c pressures i n t h e powered S t i r l i n g

cycle.

The e n g i n e was not used as a powered S t i r l i n g c y c l e u n i t in o r d e r

t o m i n i m i s e c y c l e t o cycle pressure v a r i a t i o n s , a n d i n order t o a v o i d t h e

l a r g e heat rejection i n t h e test c e l l .



DRIVE SYSTEMS TEST UNIT

MODIFIED P40

-131-



RI0PDQCONSULTING tNGUftCftf

TORQUE CURVE COMPARISON

The two curves show the torque v a r i a t i o n between a complete d r i v i n g

e n g i n e u s i n g its own h e a t i n g source, and a motorised engine(using h e l i u m as

a working medium)driven by an electric dynamometer.

The curves show that on a motorised engine there is more negative

work, therefore more torque reversals, hence crankshaft r e v e r s a l s and gear

tooth clash. However t h i s test u n i t is only a means of p r o v i d i n g a constant

load and torque cycle, to allow various d r i v e arrangements to be f i t t e d

and compared.

-132-



CYCLIC TORQUE AG A I N ST C R AN K ANG LE

Torque Curve Variation

0

Stirling Powered Engine

Meany torque

,0utput shaf t ro

Onecrankshaft

oo

us

CO

0)-a0)

to

aic

0

Motored Test R ig

'\ I

Onec ranksha f t

•Output" shaft

X)(U

cr>

CD

in0)

4->u3O



RlflRDOCOMMUTING CHOHiEEMS

T E S T C E L L

The test c e l l contains the test u n i t , with an acoustic hood

which can be lowered over the u n i t during noise measurements.

T h e test u n i t i s motored b y a s w i n g i n g a r m e l e c t r i c dynamometer

T h e heat generated d u r i n g testing i s l a r g e l y d i s s i p a t e d through heat

exchangers in the coolant and l u b r i c a t i o n system.

The h e l i u m required to pressurise the 'dummy' heads is stored

outside t h e test c e l l i n g a s bottles.

The test c e l l also contains sound recording equipment and a

control console.

Microphones are located at the free end of the test u n i t , the

d r i v e end and the r i g h t side (looking on the d r i v e end). As a further

check, accelerometers are mounted on the front and rear covers.

-134-



TEST CELL - SCHEMATIC

Microphone 3

Microphone 1

Microphone 2

Plan view

Accelerometerpositions

.Acoust ic hood

Speed and syncron is ingpulse

Side view

-135-



C O N S U L ! I N C INMNIIRS

EFFECT OF MEAN CYCLE GAS PRESSURE ON NOISE .

A test was made at AO rev/s to investigate noise v a r i a t i o n at

mean cycle pressures from 30 to 100 bar. As the graph shows there is

no apparent fluctuation fn noise levels, only a g r a d u a l increase in noise.

I t v a s therefore decided t o l i m i t t h e cycle pressure t o 6 0 b a r t o a l l o wgreater use of h e l i u m content in the pressure bottles, and to m i n i m i s e

t h e l o a d i n g on the pistons and piston rod seals, in the absence of

d i r e c t cooling i n t h i s area.

-136-



EFFECT OF MEAN CYCLE GAS PRESSURE ON NOISE

Speed at 40 rev/s.

C D

i

o >

CO00

Microphone 2

Microphone 1 —

60 80Mean Cycle Pressure - bar

100

-137- -



RMkL < L •COMSUIIlNf. t NI, •• • t H

1

EFFECT OF MEAN CYCLE GAS PRESSURE ON NOISE. .2

A s a f u r t h e r v e r i f i c a t i o n o f b e i n g a b l e t o r u n a t l o w e r m e a n

c y c l e g a s p r e s s u r e s , a f r e q u e n c y a n a l y s i s w a s t a k e n a t b l o a d C o n d i t i o n s .

E a c h s p e c t r u m i n d i c a t e d peaks a t s i m i l a r f r e q u e n c i e s . Therefore i n

c o n j u n c t i o n w i t h t h e p r e v i o u s m e a s u r e m e n t s , i t w a s a c c e p t e d t h a t i t

w o u l d be s a t i s * a c t o r y to run at a mean c y c l e p r e s s u r e of 60 b a r .

-1 38-



EFFECT OF MEAN CYCLE GAS PRESSURE ON NOISE

Microphone Position 2

Speed - 40 rev/s

2 Module - 15°Helix Gears

100 bar 60 bar

80 bar AO bar

C D"D

70

60

50100 1k 10k

1/3 Octave Band Frequency - Hz

-139-



CONSULTING ENGtMFER S

TESTING P R O C E D U R E

T h e engine i s started a n d r u n a t 2 0 rev/sec u n t i l a n o i l

temperature of 50°C and water temperature of2*0°C are reached. The

a u t o m a t i c water and oil control systems are then operativ e.

A q u a s i steady state r e c o r d i n g is made of the e n g i n e noise by

g r a d u a l l y i n c r e a s i n g the engine speed from 5 to 50 rev/sec over a

2 m i n u t e t i m e d u r a t i o n .

Tests are continued w i t h the e n g i n e r u n n i n g at 5 rev/sec for

a p p r o x i m a t e l y 5 m i n u t e s a l l o w i n g noise and v i b r a t i o n r e c o r d i n g s to be

taken. Tests are repeated at increments of 5 rev/sec, up to a speed of

50 rev/sec (i.e. 10 tests are recorded).

A t each of these test p o s i t i o n s , the m e c h a n i c a l losses are

checked and logged.

The acoustic hood is lowered over the u n i t for the d u r a t i o n of

the test.

-140-



TEST CELL

•W9 9 9 9 9 9 0

Acoustic Hood in Position

During Tests.

9 9 9 9 9 Q Q

Acoustic Hood Removed

-141-

MTI-19338



R f c W T O. OMSUIllN . IN.lNIMS

SEQUENCE OF E N G I N E TEST B U I L D S

The sequence of test b u i l d s is shown opposite.

Currently the program is on schedule.

Following the b a s e l i n e tests, noise l e v e l s have been measured on

4 different gear forms, and w i t h a l t e r n a t i v e p l a i n b e a r i n g s and b a l l

b e a r i n g s on each gear tooth form. The results are shown l a t e r in t h i s

report.

The r e s u l t s are under constant review and the schedule may be

adjusted s l i g h t l y w i t h i n t h e contractual l i m i t a t i o n s .

O n e a d d i t i o n a l test i n t r o d u c e d w i l l b e t o f i t inductance

p r o x i m i t y gauges mounted on the front cover at the end of each shaft.

These gauges sense r e l a t i v e movement, and tests w i l l be made on the

shafts w i t h h e l i c a l and s t r a i g h t spur gears to measure and compare a x i a l

shaft movements.



CO N SU M I N G E N G I N E E R S

SEQUENCE OF ENGINE TEST BUILDS

JULY 1979 BASELINE TESTS

2 MODULE - 15° HELIX

| 2 MOP STRAIGHT SPUR - 0.8 MOD 15° ELIX - 2 MOD 25°HELIX j

FIT BALL BEARING

2 MODULE - 15° HELIX

[ 2 MODSTRAIGHT SPUR - 0.8 OD 15° H E L I X - 2 MOD 25°H E L I X|

OCTOBER 1979 [ L I N K D R I V E |

2 MOD 25° HELIX - 2 MOD STRAIGHT SPUR^

|REMOVE L I N K S|

2 MOD 15 H E L I X SHAVED, DIN 6, CAST IRON

1 MOD 15° H E L I X AX I CON (ROLLING CONTACT)

I|FIT TAPER BEAR ING S|

[ 2 MOD 15° HELIX - BEST HELICAL - 2 MODSTRAIGHT SPUR |

FIT PLAIN BEARINGS

I[ D R I V E P L A T E|

MARCH 1980 j CHAIN DRIVE|

[ W R I T E R E P O R T )

-143-



M'U )

A L L G E A R D R I V E

To couple together the three shafts of a square four u n i t , and to

accommodate the c y l i n d e r f i r i n g sequence, a gear d r i v e arrangement offers

t h e s i m p l e s t solution. T h e ma in advantage i s that i t allows t h e m a i n drive

shaft to act as a contra-rotating balancer shaft, by counteracting the

i n h e r e n t p i t c h i n g couple caused b y t h e d i s p o s i t i o n o f t h e crankshaft

b a l a n c e weights, a n d thus g i v i n g 100$ dynam ic engine balance.

Together w i t h t h e smooth cyclic torque output from t h e d r i v e shaft,

t h i s gives a power p l a n t almost free from v i b r a t i o n .

-144-



ALL GEAR DRIVE

Gear Train

Viewed from Drive End of Engine

-145- -MII-19336



G E A R F O R M S

Gears t e s t e d to d a t e were chosen to g i v e a w i d e b a n d of n u m b e r s

o f t e e t h a n d h e l i x a n g l e s .

The gears are:-

-O1 5 h e l i x .

_ o

46 t e e t h - 2 m o d u l e (12.7 DP)

1 1 5 t e e t h - 0.8 module(32 DP) 15" h e l i x .

48 t e e t h - 2 m o d u l e (12.7 DP) S t r a i g h t s p u r .

43 t e e t h - 2 m o d u l e (12.7 DP) 25° h e l i x .

Reference G e a r .

-146-



GEAR FORMS

08 Module - 15 Helix 2 Module - 25 Helix

2 Module - 15 Helix

Reference Gears

2 Module - Straight Spur

-147- WTI-19339



CONSULTING CNGiNCCHS

N O I S E AND VIB RATI ON TESTING - RECORDING

M I C R O P H O N E S

The microphones were all p o s i t i o n e d approx. 0.75m above floor

h e i g h t , w i t h microphone 1 approximately 1 m t o t h e sid e, microphone 2

a p p r o x i m a t e l y O.^m away from the d r i v e - e n d and microphone 3 a p p r o x i m a t e l y

0.5m away from the opposite end of the engine (all dimensions are taken

from the v e r t i c a l centre l i n e of the engine). S i g n a l s from the microphones

were monitored d u r i n g t h e tests u s i n g a sound l e v e l meter ( g i v i n g o v e r a l l

A - w e i g h t e d levels). After s u i t a b l e a m p l i c a t i o n , t h e s i g n a l s were

recorded on 3 channels of a 7 channel FM machine.

ACCELEROHETERS

The accelerometers were mounted on the d r i v e - e n d gear housing, and

on the front cover. S i g n a l s from these accelerometers were a m p l i f i e d and

i n t e g r a t e d t o g i v e v i b r a t i o n v e l o c i t y information, hich w a s recorded o n

a further 2 channels of the tape recorder.

The r e m a i n i n g 2 channels were used for speed and synchronisat ion

s i g n a l s .



NOISE AND VIBRATION TESTING

1 Recording

Dynamometern

Speed & sync,signals

Vibrat ionsignal

amplif ier £integrator.

Soundlevelmeter.

Noisesignal

ampl i f ier

-149-



CONSUITIHI. CMCNi t "

N O I S E AND V I B R A T I O N T E S T I N G - A N A L Y S I S

A n a l y s i s of the r e c o r d e d d a t a was p e r f o r m e d in one of 3 d i f f e r e n t

ways, d e p e n d e n t o n t h e t y p e o f t e s t p e r f o r m e d . N o i s e a n d v i b r a t i o n r e s u l t s

from the s t e a d y - s t a t e t e s t s ( r e c o r d i n g s m a d e at c o n s t a n t e n g i n e s p e e d and

m e a n gas p r e s s u r e ) were u s e d to o b t a i n 1/3 octave f r e q u e n c y s p e c t r a and

t o i n v e s t i g a t e t h e r e l a t i o n s h i p b e t w e e n t h e n o i s e o r v i b r a t i o n s i g n a l s

a n d t h e c r a n k s h a f t a n g u l a r p o s i t i o n a n d r o t a t i o n a l speed. F r e q u e n c y

a n a l y s i s was c a r r i e d out on a B 6 K 2 1 3 1 d i g i t a l a n a l y s e r . I n v e s t i g a t i o n

o f t h e r e l a t i o n s h i p s b e t w e e n t h e n o i s e a n d v i b r a t i o n s i g n a l s a n d t h e

c r a n k s ' s p e e d a n d p o s i t i o n w a s m a d e b y d i s p l a y i n g t h e n o i s e ( o r v i b r a t i o n )

s i g n a l , w h i c h m a y h a v e b e e n p r e v i o u s l y p a s s e d t h r o u g h a 1 / 3 r d o c t a v e

f i l t e r set, o n a n o s c i l l o s c o p e , t o g e t h e r w i t h a t r a c e s h o w i n g t h e c r a n k s '

a n g u l a r p o s i t i o n ( u s i n g t h e s y n c h o n i s a t i o n p u l s e ) . I n t h i s m a n n e r i t w a s

p o s s i b l e t o i d e n t i f y r e l a t i o n s h i p s between c r a n k s p e e d a n d f o r c i n g f u n c t i o n

f r e q u e n c i e s , a n d ( t o a l i m i t e d extent) t o i d e n t i f y t h e p h a s i n g o f t h e

l o w - f r e q u e n c y f o r c i n g f u n c t i o n s compared w i t h t h e c r a n k p o s i t i o n .

T h e r e c o r d i n g s m a d e d u r i n g q u a s i - s t e a d y s t a t e t e s t s ( i n w h i c h t h e

e n g i n e was g r a d u a l l y a c c e l e r a t e d over the s p e e d range) were u s e d to

p r o d u c e p l o t s of the o v e r a l l A - w e i g h t e d l e v e l s a g a i n s t the e n g i n e speed.

These p l o t s may be u s e d to o b t a i n comparisons between noise and v i b r a t i o n

l e v e l s for d i f f e r e n t b u i l d s over the w h o l e speed range.

-1 5 0-



NOISE AND VIBRATION TESTING

2, Analysis

Speed

Svnc

Dig i t a l f requency analys isarid subsequent data storageon computer f i l e .

Quasi-steady state plots ofOvera l l level v Speed.

Osc i l l oscope display o f f i l t e redsignal and crank pos i t ion (From

sync, pulse.)

-151-



RI0RLG

P R E L I M I N A R Y RESULTS - GEAR TESTS LEVELS

Result* of th* quasi steady-state tests for the b u i l d s w i t h

d i f f e r e n t gear d r i v e arrangements are shown. The plots are shown fort h e noise as measured at microphone p o s i t i o n 2, t h i s b e i n g the p o s i t i o n

closest to the gear housing. Results from the other microphone p o s i t i o n s

showed the same trends as those presented, but to a lesser degree.

B u i l d No 1, u s i n g the 2 module, 15° h e l i x 'reference' gears,

showed a steady increase in noise l e v e l w it h speed, the slope of the

curve when p l o t t e d on log scales b e i n g approximately 50 dBA/decade. T h i s

steady increase was m a i n t a i n e d up to a speed of 40 rev/s, above which speed

there was a s i g n i f i c a n t (- 2dBA) decrease in l e v e l to a m i n i m u m at

45 rev/s. W i t h further speed increase, the noise l e v e l increased w i t h

speed at a p p r o x i m a t e l y 60 dBA/decade.

The fine-toothed gears of 0.8 and 15° h e l i x angle r e s u l t e d in a

decrease i n t h e noise l e v e l compared w i t h b u i l d 1 o f a p p r o x i m a t e l y 2 £ d B A

over the whole of the measured speed range. The same trend of noise l e v e l

decrease and r i s e was demonstrated as for the reference gear b u i l d at

h i g h speeds (40 to 50 rev/s).

Use of the 2 module s t r a i g h t - c u t spur gears ( b u i l d k) gave noise

l e v e l s very s i m i l a r t o those o f t h e reference gear b u i l d a t speeds o f u p

t o 25 rev/s. Above t h i s speed however, there was a d i s t i n c t ' f l a t t e n i n g1

o f t h e noise a s speed p l o t , w i t h further increase i n speed causing l i t t l e

increase in noise l e v e l . The increase in l e v e l from 25 to 45 rev/s was

a 1.5 dB A, whereas for the reference gear b u i l d the corresponding

i n c r e a s e was 4 dBA.

O v e r most of the speed range (20 to *»5 rev/s) , use of the

2 module, 2 5 ° h e l i x angle gears r e s u l t e d i n noise l e v e l s a p p r o x i m a t e l y

l j d B A h i g h e r t h a n l e v e l s measured f o r t h e reference gear b u i l d .

-152-



GEAR NOISE LEVELS

Q ua si- Steady State

Mean Pressure - 60 bar

Build 1 : Reference gearsBuild 2 : Fleron gears

2 module -15 o Helix0-8 m od ule-1 5° Hel ix

Build 4 S t ra ig ht -c ut spur gea rs— 2 moduleBuild 525°Helical gears.- 2module

Microphone Posi t ion 2

C DTD

U 100

a;

inina*

cDo

8020 30 40

Engine Speed - rev /s .

50

-153-



RI0RDOCONSULTING IN..INFCHS

P R E L I M I N A R Y RESULTS - BALL VERSUS P L A I N B E A R I N G S

I n an attempt to reduce possible noise sources caused by

crankshaft and d r i v e shaft movement, the o r i g i n a l p l a i n bearings on the

r e a r crankshaft journals and d r i v e shaft were replaced by b a l l bearings

mounted in the rear spacer plate.

When the engine is running, the m a t i n g gears have a separating

force and the two shafts tend to move through t h e i r r a d i a l b e a r i n g

clearance. Each crankshaft is also subjected to a d r i v e n and d r i v i n g

p e r i o d d u r i n g one revolution. When f i t t e d w i t h h e l i c a l gears, the

crankshafts and driveshaft therefore also tend to move a x i a l l y . B a l l

b e a r i n g s w i l l l i m i t t h e r a d i a l movement a n d tend t o damp t h e a x i a l shaftmovement.

A l l four gear sets were tested with b a l l bearings over a

q u a s i - s t e a d y state test. Comparable noise l e v e l s w i t h the 0.8 module 15°

h e l i x gears a t a l l microphone positions a n d accelerometer position 1 a r e

shown w i t h p l a i n a n d b a l l bearings.

I t can be seen that although noise l e v e l v a r i a t i o n s were achieved ,

no s i g n i f i c a n t advantage with the b a l l bearing arrangement was apparent.

-154-



GEAR NOISE LEVELS

Quasi - Steady State

Gears Tested - 08 Module - 15 Helix

Build 2:Plain bearing

Build 8 = Ball bearing

<CD-D

< U

o >

o >

înl/>0>

•Dc

I

'Mic. po s i t ion 1

'Acc el , pos i t ion 1

20 30 40

Engine Speed - rev/s

-155-



F U T U R E T E S T S 1

L I N K S A N D GEAR D R I V E

The crankpin layout throughout the engine is such that there

i s a 90° crankpin displacement on each crankshaft and a 90° displacement

between each crankshaft, making four power strokes (every 90°) for each

e n g i n e revolution. Due to the f i r i n g order sequence required by t h i s

system, a crankshaft is powered twice in succession (90° apart), and

then d w e l l s for 180° which gives an uneven cyclic torque in each

crankshaft. This i r r e g u l a r torque is transmitted by the gears (on an

a l l gear d r i v e arrangement), through the teeth, to the main d r i v e shaft.

W i t h the J i n k d r i v e the two crankshafts are coupled together

w i t h t w i n l i n k s , spaced at 90°. Theoretically t h i s w i l l allow the torque

f l u c t u a t i o n s l a r g e l y to be cancelled, g i v i n g a smoother torque d r i v e from

t h e geared crankshaft to the m a i n d r i v e shaft.

- -156-



LINK AN D G E AR D R I V E

Link and Gear Drive

Viewed from Front of Engine

-157-MT-19337



J l


D E L TA PLATE

The d e l t a p l a t e d r i v e , a l t h o u g h l i t t l e known and u s e d , c o u l d offer

a smooth and a s s u m e d q u i e t d r i v e s o l u t i o n . The p l a t e can accommodate other

a u x i l i a r y d r i v e p o s i t i o n s , such a s o i l p u m p , h y d r a u l i c p u m p , a n d water

p u m p , p r o v i d i n g t h a t e n g i n e speed i s acceptable.

T h e m a i n d i s a d v a n t a g e i s t h a t a l l s h a f t s w i l l r o t a t e i n t h e s a m e

d i r e c t i o n , l e a v i n g t h e e n g i n e w i t h a n u n b a l a n c e d p i t c h i n g moment. T o

r e g a i n f u l l o v e r a l l b a l a n c e t h e f i t m e n t o f a c o n t r a - r o t a t i n g s h a f t w i l l b e

necessary.



DELTA PLATE DR IVE

Delta Plate Drive

Viewed f rom Front of Enaine

-159- MTI-19321



ONMII I IN.. I Mt.lNII


C H A I N D R I V E

T h e c h a i n d r i v e w i l l b e f i t t e d t o t h e r e a r o f t h e u n i t , a n d i s a

3/8" t r i p l e c h a i n f i t t e d w i t h a double a c t i n g adjuster.

The t h r e e c h a i n sprockets are m a c h i n e d to g i v e a s t a g g e r e d t o o t h

p r o f i l e , and t h i s is a c h i e v e d by s p a c i n g each c h a i n s p r o c k e t 1/3 of a

t o o t h b e h i n d the a d j o i n i n g sprocket.

A g a i n t h e m a i n d i s a d v a n t a g e i s a s t h e d e l t a p l a t e d r i v e , f o r a l l

t h r e e s h a f t s r o t a t e i n t h e same d i r e c t i o n a n d a c o n t r a - r o t a t i n g b a l a n c e

s h a f t w i l l b e necessary.



CHAIN DRIVE

Chain Drive

Viewed from Front of Engine

-161-





R K a R D OCOHMILTHa C N Q M E E K S

C O N C L U S I O N S

Conclusions to be drawn from the results so far obtained may be

summarised as:-

1 . The operating condition of 60 bar mean gas pressure is representative

of all operating conditions. Operation at higher gas pressures

affects the overall level of noise and vibration measured, but doesnot s i g n i f i c a n t l y alter the 1/3 octave frequency spectrum shape.

2. At engine speeds up to approx. 30 rev/s, the use of fine-toothed

h e l i c a l gears results i n radiated noise levels t y p i c a l l y 2 i d B A

lower than those produced by any other tested gear system.

3. For speeds between 30 and ^5 rev/s, the use of straight cut spur

gears gives noise levels approximately 1i dBA lower than those of

the fine-toothed gears which were in turn approx. 2i dBA lower

than the reference b u i l d levels.

k. Inspection of the 1/3 octave noise frequency spectra shows a peak,

most l i k e l y due to a structural resonance of some form, at a

frequency of 630 to 800 Hz. This peak is the controlling factor

i n the subjective assessment (and the A-weighted overall level) of

the radiated noise.

5. Inspection of the noise and v i b r a t i o n signals from the

accelerometers have not yet been completely analysed.

6. Use of b a l l bearings at the d r i v e end of the 'shafts gave no

s i g n i f i c a n t overall red uction of either the noise or the v i b r a t i o n

l e v e l s , although there were l o c a l variationsof up to ± 3 dBA

depending on engine speed and measuring positions.



1. R e p o r t N o .

NA SA CR-159744

2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtit le

AUTOMOTIVE STIRLING ENGINE DEVELOPMENT PROGRAM - QUARTERLY

TECHNICAL REPORT FOR PERIOD: JULY 1 - SEPTEMBER 30, 1979

5 . Report Date

March 1980

6. Perform ing Organization Code

7. Author(s)

Therese A. Derikart

Merton Allen

8. Performing Organization Report No .

MTI 79ASE101QT6

10. W o rk Unit No.

9 . P e r f o r m i n g O r g a n i z a t i o n N a m e a n d Address

Stirling Engine S y s t e m s Division

Mechanical Technology Inc.

968 Albany-Shaker Road

Latham, New York 12110

11. Contract or Grant No .

DE N 3-32

. Sponsoring Agency N a m e and A d d r e s s

U . S . D e p a r t m e n t o f E n e r g yO f f i c e of Transportation P r o g r a m sW a s h i n g t o n D.C.

1 3 . Type o f R e p o r t a n d P e r i o d C o v e r e dQuarterly Contractor R e p o r tJuly 1 - S e p t e m b e r 30, 1979

1 4 . S p o n s o r i n g A g e n c y Code

D O E/N A S A /0 0 3 2 - 7 9 /5

Notes

Quarterly Report. Prepared under Interagency Agreement EC-77-A-31

William K. Tabata, Transportation Propulsion Division. NASA Lewis

Ohio 44135

-10040. Project Manager,

Research Center, Cleveland,

This Quarterly Technical Progress Report covers the sixth quarter of activity after award of

Documents

Automotive Stirling Engine Development Program.19800072709_1980072709