Parametric Geometry for Propulsion-Airframe Integration

NASA NRA NNX11AI70A Topic 2.2

Russell K. Denney Jimmy C. Tai

Dimitri N. Mavris

Georgia Institute of Technology Atlanta, GA 30332

2

Outline

• Objective and Background

• Approach

• Current Progress

– “Inside” Track

– “Outside” Track

– Model Problems

• Observations from Year 1

• Year 2 Work Plan

3

Background

• Our typical design process starts with the engine cycle and a vehicle representation, which is used for drag prediction.

• Thrust , fuel flow, and drag data are used for the mission analysis and analyses for other system metrics, such as noise and emissions.

Parametric Aircraft (VSP) Cycle Modeling (NPSS)

Aero Generation Mission Analysis (FLOPS)

Other System Metrics

4

Background

• In recent years we have begun adding engine flowpath design to the process, to ensure our engines are “buildable” and to provide better data for weight, noise, and emissions predictions

Parametric Aircraft (VSP) Cycle Modeling (NPSS)

Aero Generation Mission Analysis (FLOPS)

Other System Metrics

Flowpath Design (WATE++)

5

Background

• New tools such as OpenVSP and OTAC for the engine flowpath will make it possible to bring more physics into the conceptual design process

Parametric Aircraft (VSP) Cycle Modeling (NPSS)

Aero Generation Mission Analysis (FLOPS)

Other System Metrics

Flowpath Design (WATE++)

OpenVSP Engine Flowpath

Higher Fidelity Design/Analysis Tools

6

Motivation

• Traditionally most resources have been committed during the last half of the development process

– Late design changes are difficult and expensive

• However the fate of the program is often decided by the decisions made early on

• Development risk and cost may be reduced by improving the capability of the conceptual phase

Panchenko et al, Preliminary Multi-Disciplinary Optimization in Turbomachinery Design, RTO AVT Symposium on “Reduction of Military Vehicle Acquisition Time and Cost through Advanced Modelling and Virtual Simulation”, Paris, France, 22-25 April 2002, RTO-MP-089

7

The Big Picture

Conceptual Design Tools

Intended to run quickly Use simplifying assumptions Solve simplified equations Usually 1-D or 2-D geometry

Model more detailed physics Usually require 3-D geometry

Aero

Structure

Noise

etc

Analysis Tools Iterative “Design by Analysis” Process

How to “connect” the design and analysis tools to ensure a consistent geometry is analyzed by each discipline?

8

The Big Picture

Conceptual Design Tools

Aero

Structure

Noise

etc

Analysis Tools

OpenVSP

OpenVSP provides: 3-D Design DOF Visualization Geometry Standard

o Ensures consistent geometry is analyzed by all disciplines o Geometry is updated with each iteration

9

Program Plan

The research is divided into two main tracks:

• Parametric Variation of Inlet and Nozzle Geometry – Improved estimation of installation effects, throttle-dependent drags,

and engine-airframe interactions

– Address unique problems related to parameterization of advanced inlets and nozzles, which may be square or round, straight or serpentine, and may have special geometric features such as chevrons

• Parametric Variation of the Entire Engine Flowpath – Produce a 3D representation of the complete engine flowpath

geometry, which will permit more detailed analyses of unconventional engine cycles

– Identify specific requirements for engine fan and turbine parameterization for successful interfacing with higher-order, physics-based tools for noise and performance analyses

10

Current Progress – “Inside” Track

• 3-D Engine Flowpath Design

11

OpenVSP in the Engine Flowpath Design Process

Cycle and Flow-path Design NPSS/WATE++

Vehicle Sketch Pad

Higher Order Analyses

Meta-Geometry

Higher Order Analyses

3-D Geometry Tool Adds Design DOF

2-D Flow Path Defines Basic Shapes (Areas, Radii, Lengths, etc.)

Aero Codes, Structural Analysis

Codes, etc

Rhino3D

12

NPSS/WATE++

NPSS is an object-oriented programming environment for modeling aircraft turbine engines • Traditional 0-D thermodynamic cycle

modeling • “Zooming” capability to link with

higher fidelity design and analysis codes

WATE++ is a collection of NPSS objects for predicting the engine flowpath dimensions and weights • Uses thermodynamic cycle data as input • Simplified stress analyses & empirical

relationships to size the components

13

OpenVSP “Sockets”

• Each WATE++ component has been modified to include a socket or subelement to generate the XML code for OpenVSP

• Simply include the socket when the element is instantiated in the WATE++ config file

• Defines additional OpenVSP parameters for 3-D geometry that WATE++ doesn’t care about

WATE++ run file

NPSS run file Runs NPSS cycle model

Config File

Base Element

WATEvspSubelement.int

14

150Pax HPC

Drawing WATE++ Compressors in OpenVSP

• Component Parameters – Inport location and Radii

– Outport Radii

– Total compressor length

– IGV length

– Front frame length

• Stage Parameters – Blade axial length (each stage)

– Stator axial length (each stage)

– Spacing length (or % of stage length)

– Num blades (each stage)

– Tip Radius

– Hub radius (or HtoT ratio)

• Blade Parameters – Twist distribution

– Airfoil shape

– Taper

– Etc.

• OpenVSP Socket for HPC and LPC – PROPELLER element for blades

– FUSELAGE2 element for hub and casing

150Pax Booster

15

Issues with the Compressor Elements

• Issue of how to properly contour the casing

– Currently placing a FUSELAGE2 cross section at every blade trailing edge

– Interpolating between the rotor casing radius to get the stator blade tip radius (stators are flush with casing)

– May want more complex case contouring

• Tip clearance

– Added a single variable to the WATE socket which is applied at each stage

– Could specify tip clearance on a per-stage basis

Casing-stator overlap

16

Turbofan Engine Demo

• A “complete” separate flow high bypass engine was modeled using OpenVSP sockets added to the required WATE++ elements

• This OpenVSP model consists of 62 components, either PROPELLER or FUSELAGE2 components, representing the engine components

• Still to be developed are the combustor, shafts and disks, and true airfoil representations

17

Current Progress – “Outside” Track

• Propulsion Airframe Integration

18

OpenVSP in the PAI Design Process

Inlet, Nozzle, Nacelle Design Codes

Vehicle Sketch Pad

Higher Order Analyses CART-3D

Meta-Geometry

Higher Order Analyses

3-D Geometry Tool Adds Design DOF

Lower Fidelity Design Codes Define Initial Geometry

Higher Fidelity Aero Codes, Structural

Analysis Codes, etc

19

Cowl/Nozzle/Engine Parameters

Cowl/Nozzle Parms Eng/Nozzle Shape

Rmax/Rfan* Boattail*

Lmax/Rmax Fore Cowl Tan Str1*

Rexit Fore Cowl Tan St2*

Area Ratio Aft Tan Str1*

Aft Length Aft Tan Str2*

Top/Bot Sym Top/Bot Sym

Left/Right Sym Left/Right Sym

Lmax

Fore cowl Tan Str1 and 2 Aft Tan Str1 and 2

Rexit

Aft Length

Rmax

20

Inlet Parameters

Inlet Parms Inlet Shape

Rfan Number of Interp Xsecs**

Rhl/Rfan* Diffuser Tan Str1*

Rth/Rhl* Diffuser Tan Str2*

Lip Fineness Lip Tan Str1*

L/Rfan Lip Tan Str2*

scarf*** Top/Bot Sym

Top/Bot Sym Left/Right Sym

Left/Right Sym

Rfan Rhl

L

Rth

Lip Fineness x (Rhl-Rth)

Lip Tan Str1 and 2 Diffuser Tan Str1 and 2

21

Nozzle Parameters • Axisymmetric Converging Nozzles:

– Two types: Bypass nozzle, Core nozzle

• Bypass Nozzle: – Cowl connecting nozzles

– 3 (outer) or 4 (inner) FUSELAGE2 cross sections

• Core Nozzle: – Plug

– 3 (outer) or 4 (inner) FUSELAGE2 cross sections

Area Ratio Inner Tan Str 3

L/D Inner Tan Str 4

Inport Axial Loc Outer Tan Str 1

Inport Inner R Outer Tan Str 2

Inport Outer R Outer Tan Str 3

Inner Tan Str 1 Outer Tan Str 4

Inner Tan Str 2 By-pass Boattail

Bypass Nozzle Parms

0

5

10

15

20

25

30

35

50 70 90 110 130 150

Bypass Nozzle

Core Nozzle

Plug

Area Ratio Inner Tan Str 1

L/D Inner Tan Str 2

Inport Axial Loc IOuter Tan Str 1

Inport Inner R Outer Tan Str 2

Inport Outer R Core Boattail

Plug Length

Core Nozzle Parms

22

Example: WATE++ Nacelle

Point x-Geometry Relation y-Geometry Relation

Wal

l Po

ints

1 0 Rfan

2 Fan Out Location - Fan stage length Rfan

3 -(L/D ratio * Fan Radius) Rth

4 x3 - 2*(Rhi-Rth)/5

Quadratic fit using distance from throat to Inlet lip leading edge

5 x3 - 2*(Rhi-Rth)*2/5

6 x3 - 2*(Rhi-Rth)*3/5

7 x3 - 2*(Rhi-Rth)*4/5

8 x3 - 2*(Rhi-Rth) Rhi (=1.2*Rth)

Nac

elle

Po

ints

9 x3 - 2*(Rhi-Rth) Rhi (=1.2*Rth)

10

Percentage of Point 15 based on lip Airfoil Shape

{ 0.01, 0.02,0.03,0.06, 0.10,1.0}

Fixed Percentage of Point 15 based on lip Airfoil Shape

{ .1302,.1839,.225,.317,.4071,1.0}

11

12

13

14

15 (-1.92*(1.0/(Rmax/Rhi)+2.088)*2.0*Rmax Max Nacelle Radius

16 FanfaceToMaxNacelleArea Max Nacelle Radius

17 Byp Nozz Outport Location Byp Nozz Outer Radius

1 2 3-8

9-14

15 16

17

Variable Description

diameter fan diameter

Ath Throat Area (Corrected

Mass flow)

Ahit Highlight area of the top

Ahib Highlight area of the

bottom

Ldratio Length of diffuser/Dfan

At Distance from HL to

Throat top

Ab Distance from HL to

Throat bottom

twall Thickness of the wall at

max area

x Distance from Highlight to

max area

AbypNozz Bypass nozzle area

Lnozzle Distance from fan face to

bypass nozzle area

23

Nacelle Meshing Issue

• OpenVSP has the capability to combine two open components into a single mesh using CompGeom or CFD Mesh – Components must have

coincident beginning and ending cross-sections

– Multiple open components (>2) cannot currently be combined into a single mesh

• Either change the way WATE++ draws a fueslage or modify the OpenVSP meshing logic

24

Model Problem Investigation

• Illustrate utility and flexibility of parameterized components

• Demonstrate capability to geometrically model novel and unique advanced concepts

• Test the limits of OpenVSP and its components – Are the provided components sufficient?

– If not should they be reworked/modified or should new components be added?

• Test the component parameterizations and the integration relationships

• Use Cart3D to validate applicability of parameterizations in an analysis environment

25

Model Problem Progress

• Constructing baseline and advanced concept models in OpenVSP using parameterized components

• Setting up flow-through analysis on meshed nacelle in Cart3D

• Using “pucks” to define boundary conditions at inlet and exit of through-flow nacelle

26

Observations from Year 1

• OpenVSP Graphics Display Update Speed

– Currently, the display update speed of OpenVSP with the 62-component engine model is unacceptable

– This may be partially due to the number and/or complexity of the components that must be modeled, but consensus is that it has more to do with the internal OpenVSP graphics procedures

27

Observations from Year 1 (cont’d)

• Need for Improved Component Parameterizations

– The most significant finding from last year’s work is the need for improved component parameterizations within OpenVSP

– It was decided early on to use the same parameterizations as in WATE++

– However, once in OpenVSP, the parts have the parameterization of the OpenVSP components (i.e., of the PROPELLER and FUSELAGE2 elements), and the WATE++ parameterization is lost

– Solution: create new OpenVSP elements to support the WATE++ parameterization

28

“Tube” Element – Notional Views

• Currently requires two FUSELAGE2 elements

• Will be useful for embedded inlets, scarfed inlets, non-axisymmetric ducts, etc.

29

“Ginsu” Element – OpenVSP Depiction

• The basic element has three components:

– Casing (outer diameter) ring

– Rim (inner diameter) disc

– Strut or blade sections

Ring

Blade

Disc

30

“Ginsu” Element (cont’d)

Basic element used as a frame component

Omit rim piece to represent a vane row

Omit casing piece and format rim piece to represent a bladed disk

• One basic element can model most engine flowpath components

31

Year 2 Work Plan

• “Inside” Track — Create new “tube” and “Ginsu” OpenVSP elements

— Update OpenVSP sockets to use the new elements

— Develop combustor, shafts and disks, and true airfoil representations

• “Outside” Track — Continue work on model problems

— Investigate meshing issues

— Introduce additional design and analysis codes

SUPIN

Calculix