2008-10-20 - Thermal Management Concept Investigations of ...1 Daimler Trucks Thermal Management Concept Investigations of the new Heavy Duty Engine Platform using GT-Cool/GT-Power

1

Daimler Trucks

Thermal Management Concept Investigations of the new

Heavy Duty Engine Platform using GT-Cool/GT-Power

GT-Suite-Conference

Frankfurt/M., 20.10.2008

Matthias Schmid

20.10.2008 - Frankfurt/M. - GT-Suite-Conference 2Daimler Trucks

Agenda

• Overview Heavy Duty Engine Platform

• Overview thermal management investigations

• Model setup

• GT-Power model

• GT-Cool model

• Results

• Conclusion


First version of the new Heavy Duty Engine Platform:Detroit Diesel DD15 (EPA07)

• Configuration: 6 cylinder in-line

• Displacement: 14.8l

• Bore: 139mm

• Stroke: 163mm

• Max. Power: 418kW (560hp)

• Max. Torque: 2509Nm (1850 lb-ft)

• Thermostat & fan: inlet controlled

• Following displacements: 10.6l, 12.8l, 15.6l

• The new platform will replace the successful BR500 & OM457 (Mercedes-Benz), S60 (Detroit

Diesel) and 6M70 (Mitsubishi Fuso).


Goal of the thermal management investigations:“How to save fuel?”

• Reduce “real” engine friction with higher oil temperature between the friction surfaces

• Reduced coolant flow (pump clutch)

• Higher coolant temperature (heated thermostat)

• Higher (overall) oil temperature (oil thermostat)

• Reduce coolant pump power consumption due to lower coolant flow

• 2-stage clutch (magnetic)

• Stage less clutch (viscous)

• Reduce oil pump power due to lower pressure rise (with oil thermostat)

• Higher oil temperature (lower oil viscosity)

• Eliminate pressure loss of oil cooler at low oil temperatures

• Optimize the fan controller for inlet controlled system

• Implement set point dependency of engine speed and load

• The maximum capability of the cooling system must not be reduced; transient behavior of the

modified system must be acceptable to avoid temperature peaks. Change of emissions must be

considered.


Indirect coupled GT-Power/GT-Cool model setup

Engine State

•Speed

•Load

•Fuel cons. map

Vehicle*

•Speed

•Gear

•road grade

Cooling system

•Temperature

•Pump power

•Fan power

GT-Power result file

•Gas side boundary

conditions

Oil circuit

•Temperature

•Pump power

Control system

•Coolant pump

•Fan

•Thermostat

Friction power

calculation

*Results from LDYN (Daimler Trucks software for longitudinal dynamics simulation)

Fuel consumption

•total

•specific

„Output“

„Input“


GT-Power model

• GT-Power model calculates stationary in-cylinder gas side boundary conditions:

• Engine fired mode

• Engine brake mode

• Results are adjusted with

steady-state measurement results

(heat release rate).

• Indirect coupling provides sufficient accuracy;

calculation speed of GT-Cool model is

real time or faster.

• Direct coupling is not recommended:

• Solver too slow for long distance simulations.

• Heat release rate (transient mode) ≠ Heat release rate (steady-state mode)

►complex burn rate model necessary


GT-Cool model – Coolant circuit (main window)

Vehicle

Accessory

cooling

Cooling

air path

Coolant

distributor

Coolant

collector

Coolant

thermostat

EGR-Cooler

Engine state part

Cylinder 1-6

Surge tank

Friction

• Layout similar to real engine

• Includes

• coolant system with 3D-cylinders

• Interfaces to all sub-models

• Interface to GT-Power result file

• Cooling air path

• Vehicle

• Engine state part

• Accessory heat input via map

interpolation.

• Accurate calibration of water jacket parts

(material, thickness, surface roughness)

necessary for adequate liner

temperatures.


Oil circuit

Friction

bearings

Main gallery

Piston heat

Liner heat

Friction

valvetrain

Turbocharger

Turbocompound

Oil panPump

Oil cooler

Oil thermostat

Bypass

Air

compressor

Heat release

Heat input

• The oil circuit must be calibrated with attention to achieve correct heat input:

• Heat transfer coefficient (piston & liner)

• Volume flow (component pressure drop)


Clutch controllerCoolant pump / Fan

• Clutches are gear parts with varying ratio and efficiency

• Necessary clutch ratio is calculated similar to ECU algorithm

• Clutch efficiency is interpolated from measurement results

• Example: Coolant pump clutch

Stage less clutch

2-stage clutchClutch ratio / efficiency

Coolant pump

Engine state

Pulley ratio

Controller window

Main window

Selector (case setup):

• Standard (no clutch)

• 2-stage clutch

• Stage less clutch

Coolant pump clutch

characteristics

pulley speed [rpm]

pum

p im

pelle

r sp

eed

[rpm

]

2-stage clutch high2-stage clutch low

stageless clutchoperation range

identical tostandard pump


Modeling coolant thermostat

• Flexible setup needed for different specifications:

• Standard wax thermostat

• Heated wax thermostat

• Electric valve

• Thermostat build-up consists of 3 parts:

• manual valve (actuated)

• Transfer function for wax behavior (by B. Luptowski / GTI)

• Control function for heating power (optional)

Controller for

heating power

Manual valve

Transfer function


Friction power calculation

• Schwarzmeier‘s formula for calculating the mean friction pressure:

( ) ( ) ( )me

oiloilCW

me

CW

me

CW

m

CW

m

frictionfriction

pnfT

nd

T

ndC

T

p

T

pC

T

c

T

cC

pp

,66,1*

2*

66,1

2

366,1*

*

66,1266,1*

*

66,11

*

+

⋅−⋅⋅+

−⋅+

−⋅+

+=

•C1, C2, C3 : engine specific constants•TCW : Cylinder wall temperature („relevant to friction“)•cm : mean piston speed•pme : mean effective pressure

Source: Schwarzmeier, M.: Reibmitteldruck – Der Einfluß des Arbeitsprozessverlaufs auf den Reibmitteldruck; FVV Vorhaben Nr. 421 Abschlussbericht; FVV-Heft 503; 1992

piston

crankshaft,connecting rod,

valve train

accessory

• Crankshaft / Connecting rod / valve train friction depends on oil temperature & engine speed• Piston friction depends on cylinder wall temperature & engine speed / load

•d : mean bearing diameter (crankshaft, connecting rod)•n : engine speed•Toil : mean oil temperature•* : reference value (from measurement)

How to get cylinder wall temperature?


Cylinder wall temperature calculation

( ) ( ) ( )**** 8,05,16,1 coolantcoolantmememmCWCW TTppccTT −⋅+−⋅+−⋅+=• Schwarzmeier‘s formula (for steady-state engine operation / raw data):

• Wall temperature of 3D-cylinder model (GT-Cool)

Raw data

Similar behavior

►Cylinder wall temperature TCW can be taken from the GT-Cool 3D-cylinder model

Load step

(Results must be smoothed for transient engine mode)


Comparison cylinder liner temperatures: Simulation vs. Measurement results

• Surface temperatures (0mm depth) are approx. 10°C higher than measured values (1mm depth).

• Behavior of calculated cylinder liner temperatures similar to measurement results.

• Limited accuracy of absolute values due to restricted potential of the 1D-model.

n=1240 1/minTCoolant =90°C

0

20

40

60

80

100

120

140

160

180

200

90 100 110 120 130 140 150 160 170 180

T [°C]

h [m

m]

p_me=21,2bar

p_me=5,3bar

Temperature values:Measurement: 1mm below liner surfaceSimulation: on liner surface(General reference value for temperature gradient in liner wall: approx. 10°C/mm)Measurement result range

pme=21,2barpme=5,3bar

Simulation results:


Example: Comparison fan control system

• Standard system

with 1 fixed value

for desired

coolant outlet

temperature.

• Modified system

with dependency

of coolant inlet

temperature and

engine

speed/load leads

to faster

reaction. Smaller temperature peaks

Faster reaction

Less engagement


Conclusion

Advantages of a coupled GT-Power/GT-Cool model:

• delivers sufficient accuracy for concept investigations

• allows predictions (fuel consumption) before hardware parts are available

• gives the possibility to create first validation of ECU-calibration

• allows fast valuation of new concepts without prototype hardware

• supports the experimental (vehicle & engine test bench) development


Thank you for your attention!

Documents

2008-10-20 - Thermal Management Concept Investigations of ...1 Daimler Trucks Thermal Management Concept Investigations of the new Heavy Duty Engine Platform using GT-Cool/GT-Power