NASA/TM--2002-211351

Overview of High-Fidelity Modeling

in the Numerical Propulsion System

Simulations (NPSS) Project

Activities

Joseph R Veres

Glenn Research Center, Cleveland, Ohio

June 2002
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NASA/TM--2002-211351

Overview of High-Fidelity Modeling

in the Numerical Propulsion System

Simulations (NPSS) Project

Activities

Joseph R Veres

Glenn Research Center, Cleveland, Ohio

Prepared for the

Aerospace Numerical Simulation Symposium

sponsored by the National Aerospace Laboratory of Japan

Tokyo, Japan, June 20-22, 2001

National Aeronautics and

Space Administration

Glenn Research Center

June 2002
Acknowledgments

I would like to acknowledge the support of NASAAmes Research Center in providing the resources and the

computing time on the NAS computers and the support of Dr. John K. Lytle, head of the Computing and

Interdisciplinary Systems Office at NASA Glenn Research Center. I would also like to thank John Adamczyk,

Nan-Suey Liu, Mark Turner, and Rob Ryder for their technical contributions to the success of this project.

This report contains preliminary

findings, subject to revision as

analysis proceeds.

Trade names or manufacturers' names are used in this report for

identification only. This usage does not constitute an official

endorsement, either expressed or implied, by the National

Aeronautics and Space Administration.

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Available electronically at http: / / gltrs.grc._aasa.gov/GLTRS
Overview of High-Fidelity Modeling Activities in the

Numerical Propulsion System Simulations (NPSS) Project

Joseph P. Veres

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Abstract

A high-fidelity simulation of a commercial

turbofan engine has been created as part of

the Numerical Propulsion System Simulation

project. The high-fidelity computer simulation utilizes computer models that were developed at NASA Glenn Research Center, in

cooperation with turbofan engine manufacturers. The average-passage (APNASA)

Navier-Stokes based viscous flow computer

code is used to simulate the 3D flow in the

compressors and turbines of the advanced

commercial turbofan engine. The 3D National

Combustion Code (NCC) is used to simulate

the flow and chemistry in the advanced aircraft combustor. The APNASA turbomachinery code and the NCC combustor code

exchange boundary conditions at the interface

planes at the combustor inlet and exit. This

computer simulation technique can evaluate

engine performance at steady operating conditions. The 3D flow models provide detailed

knowledge of the airflow within the fan and

compressor, the high and low pressure turbines and the flow and chemistry within the

combustor. The models simulate the performance of the engine at operating conditions that

include sea level takeoff and the altitude

cruise condition.

Introduction

In the design phase of gas turbine engines,

components are designed using computer

models that simulate the aerodynamic, thermal and structural characteristics of the

component. In the early phases of the design

process, the component characteristics within

the thermodynamic cycle system model may

not accurately represent the performance of

the engine components, and may not model

the interactions between the components. The

components are later designed, built and

tested to verify that the design intent performance specifications have been met. As

each component is assembled to form the

core engine and ultimately the complete engine system, further verification tests are usually required. Due to component interaction

effects such as radial profile variations, the

performance of components in an engine system may be different from the performance

obtained from isolated component tests.

These differences can result in a nonoptimum performance match between the engine components. The difference in performance between the isolated component and the

performance of the component within the engine system can be the cause of additional

iterations in the design and development

process. Multiple component and engine

build and tests can add $300 M and 2 years to

the design/development cost and time.

NPSS is a system simulation infrastructure

designed to provide an integrated computing

environment for conducting low and high

fidelity engine simulations on a variety of

computer platforms (Reference 1). NPSS

simulations are characterized by their ability

to introduce low and high fidelity component

simulation codes (References 2, 3) and combine multi-disciplinary analyses all deployed

on heterogeneous computing platforms for

fast turnaround.

NASA/TM 2002-211351 1
The goal of the NPSShigh fidelity engine

simulationsis to provideto aircraft engine

manufacturersthe capabilityto numerically

verify engineperformance,includingthe effects of componentinteractions,prior to

buildingandtestingtheengine.Thiscapability will supportthe developmentof commercial engines,supersonicbusinessjets, and

militaryprograms.NPSShighfidelity simulationscanmodelengineperformanceat operating conditions throughoutthe envelope,

includingsealevel takeoff andcruise.High

fidelity systemsimulationcanalsoreducethe

amountof expensiveenginetestingduring

development,whichtypically costsin excess

of $15,000perhour.

Detailed Flow Simulation of a Modern

Turbofan Engine

The detailed flow simulation of a modem turbofan engine is one of the key tasks in the

NPSS project at NASA Glenn Research

Center (NASA GRC). The objective of this

task is to perform a 3D flow and chemistry

simulation of a modem high-bypass ratio

commercial turbofan engine. The goal of the

turbofan engine flow simulation task is to

perform the high-fidelity computer simulation

of the entire engine, at the design point operating condition, in under 24 hours of wall

clock time on a parallel computer system.

The GE90 turbofan engine was selected

(Fig. 1) and modeled in cooperation with GE

Aircraft Engines (References 4, 5, and 6). The

detailed flow simulation task leverages from

previous efforts at NASA GRC and cooperative efforts with U.S. aerospace industry participants that resulted in the development of

the APNASA turbomachinery flow code

and the National Combustion Code (NCC).

APNASA is NASA's average passage

3-dimensional steady state Navier-Stokes

flow code that has been developed to simulate

the complex flow within the turbomachinery

components of gas turbine engines.

Figure 1. The GE90 high-bypass ratio commercial

turbofan engine.

The components within the GE90 turbofan

engine's primary flow path were simulated

with the 3D Navier-Stokes flow codes. All

secondary flows such as compressor bleeds,

turbine disk cavity purge and cooling flows

have been accounted for to accurately simulate the engine. These secondary flows were

modeled macroscopically as source terms, or

boundary conditions to the APNASA and

NCC codes. The information on these source

terms was obtained from detailed descriptions

of the bleeds and cooling flow and from low

fidelity thermodynamic cycle simulations of

the engine system. These source terms provided boundary condition data to the 3D

simulations. The radial variations of flow

conditions at the exit of the high-pressure

compressor have been utilized as the inlet

boundary condition for the NCC combustor

simulation. The combustor exit conditions, as

modeled with the NCC code, were averaged

in the circumferential direction and utilized as

the inlet boundary conditions for the highpressure turbine simulation. This method was

effective at transferring the combustor exit

radial profiles of pressure and temperature to

the turbine inlet, and therefore, modeled the

steady-state aerodynamic interaction effects

between the compressor, combustor and turbine components of the engine.

NASA/TM 2002-211351 2
Compressor Simulation

The fan, booster compressor and the highpressure compressor (HPC) were successfully

modeled with the APNASA flow code.

Figure 2 shows the simulation of the fan,

booster and HPC with the absolute Mach

numbers at mid-stream.

The simulations were run on parallel workstation clusters at NASA Ames Research

Center.

Figure 2. The APNASA flow simulation of the fan,

booster and high-pressure compressor.

To simulate the engine turbomachinery in 3D

also requires accounting for the multistage

aerodynamic blade interaction effects. The

APNASA code accounts for most of these

effects by calculating the deterministic

stresses in the adjacent blade rows and applying these as a body force. Rotor tip clearance

and stator leakage flows were also modeled.

The inlet total pressure to the APNASA

model of the HPC was adjusted to match the

exit corrected mass flow in the thermodynamic cycle model. The corrected and physical shaft rotational speeds were held constant

at engine cycle values. Figure 3 shows the

21 blade row HPC simulation with the Mach

number superimposed onto the blade surfaces. The APNASA simulation of the highpressure compressor accurately models the

performance as measured on compressor test

rigs and the engine.

Figure 3. The high-pressure compressor of the highbypass ratio turbofan engine.

The computer timings were obtained for the

converged APNASA simulation of the highpressure compressor (HPC) on the SGI Origin

3000 computer at Ames Research Center.

A total of 504 (400 MHz) processors were

used, with 16 to 27 processors per blade row

depending on the grid size. The size of the 3D

grid is 9.9 million grid nodes. The total wall

clock time for 10,000 iterations was 2 hours

and 30 minutes.

Combustor Simulation

Modeling of the full combustor was a key

part of the turbofan engine simulation project.

The aerodynamics and the turbulent combusting flow and chemistry were modeled with

the National Combustion Code (NCC). This

large-scale calculation also used high performance computers at both NASA GRC and

at NASA Ames Research Centers. The NCC

is an integrated system of code modules that

uses unstructured meshes and can be run on

parallel computing platforms for reduced

turnaround time. The current version of the

NCC consists of several major modules such

as baseline flow solver, chemistry, turbulence-chemistry interaction and spray combustion. The code has been used to model the

NASA/TM 2002-211351 3
full combustor from the compressor exit diffuser, to the turbine inlet including all secondary flow regions (Fig. 4).

Figure 4. The combustor of the high-bypass ratio

turbofan engine.

In a typical turbine engine approximately

80% of the air passes through the combustor

and flows through the high-pressure turbine.

The remaining 20% is bled off the combustor

diffuser for cooling and cavity purge of the

turbine blade, vane and disk. The flow path of

the complete combustor was modeled with

the NCC enabling detailed knowledge of the

complex flow field.

The detailed simulation capability provided by

the NCC can enable combustor designers to

minimize losses through the various regions

within the combustor, as well as to optimize

cooling and dilution air requirements. Reduced

cooling requirements can have a large impact

on engine specific fuel consumption. The 3D

model of the GE90 combustor is a 24 degree

sector representation of the full annulus that is

spatially periodic. The NCC combustor model

included the compressor exit diffuser, flow

swirlers, cooling and dilution holes, inner and

outer case and four fuel nozzles. The NCC

model consists of a 3D Navier-Stokes flow

simulation with heat release. The spray and

chemistry models were not utilized in the full

engine simulation, but are currently being

incorporated into the NCC model. The successful NCC simulation increases knowledge

about the flow conditions within the combustor and provides the detailed inlet conditions

into the cooled high-pressure turbine stage.

The NCC simulation enables modeling hot

streaks caused by the pattern factor exiting the

combustor. However, for this project the total

temperature and total enthalpy exiting the

combustor were averaged in the circumferential direction to provide the inlet boundary

conditions into the subsequent steady state turbine simulation with the APNASA flow code.

Turbine Simulation

The flow simulation through the cooled high

and low-pressure turbines and the transition

duct (Fig. 5) was successfully accomplished

using version 5 of the APNASA flow code.

The inlet boundary conditions into the turbine

simulation were the radial profiles of total

temperature and enthalpy obtained from the

exit plane of the combustor. At this plane there

is no flow recirculation in the combustor and

almost all of the combustion has taken place.

The fully coupled APNASA simulation of the

high and low-pressure turbines has provided

designers with improved understanding of the

detailed flow within the turbine stages.

Figure 5. The high and low-pressure turbines of the

high-bypass ratio GE90 turbofan engine.

NASA/TM 2002-211351 4
In addition it successfully simulated the interaction between the high and the low-pressure

turbines which could not otherwise be modeled in separate simulations (see References

4, 5, and 6 for the detailed description of the

turbine simulation). The APNASA combined

HP and LP turbine simulation can now be

done in 2 hours and 16 minutes on the Chapman computer, which is a 512 node machine

with 400 MHz processors at NASA Ames

Research Center (References 7, 8, and 9).

Summary

The 3-D flow was successfully simulated in

all of the major components of the turbofan

engine. The simulation of the complete engine was achieved by utilizing two interface

planes to exchange boundary condition data

at the combustor inlet and exit. At the two

planes of data exchange, the radial profile exit

boundary conditions were transferred to the

downstream components as inlet boundary

conditions. The compressor and turbine were

modeled with the APNASA flow code. The

combustor was modeled with the National

Combustion Code using a gaseous spray

model and a Magnussen heat release model.

References

. "The Numerical Propulsion System Simulation: A Multidisciplinary Design System

for Aerospace Vehicles," John K. Lytle,

NASA/TM--1999-209194.

. "Energy Efficient Engine Low Pressure

Subsystem Aerodynamic Analysis,"

Edward J. Hall, Sean R. Lynn, and

Joseph P. Veres, Joint Propulsion Conference, 1998, AIAA-98-3119.

.

.

.

.

.

.

.

"Energy Efficient Engine Low Pressure

Subsystem Flow Analysis," Edward J.

Hall, Sean R. Lynn, Nathan J. Heidegger,

and Robert A. Delaney, NASA/CR--

1998-206597.

"Multistage Simulations of the GE90

Turbine," Mark G. Turner, Paul H. Vitt,

David A. Topp, Sohrab Saeidi, Scott D.

Hunter, Lyle D. Dailey, and Timothy A.

Beach, NASA/CR--1999-209311.

"Multistage Simulations of the GE90

Turbine," ASME Paper 99-GT-98, Mark

Turner.

Turner, Mark G., "Full Analysis of the

GE90 Turbofan Primary Flowpath,"

NASA/CR--2000-209951.

"Numerical Propulsion System Simulation (NPSS) 1999 Industry Review,"

NASA/TM--2000-209795, Lytle, Follen,

Naiman, Evans, Veres, Owen, and Lopez.

"Numerical Propulsion System Simulation (NPSS) 2000 NPSS Annual Review,,

NASA/CP--2001-210673, Lytle, Follen,

Naiman, Evans, Veres, Owen, and Lopez.

"Numerical Propulsion System Simulation (NPSS) 2001 NPSS Annual Review,"

NASA/TM--2002-211197, Lytle, Follen,

Naiman, Evans, Veres, Owen, and Lopez.

NASA/TM 2002-211351 5
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Overview of High-Fidelity Modeling Activities in the Numerical Propulsion

System Simulations (NPSS) Project

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Joseph P. Veres

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National Aeronautics and Space Administration

John H. Glenn Research Center at Lewis Field

Cleveland, Ohio 44135-3191

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Prepared for the Aerospace Numerical Simulation Symposium sponsored by the National Aerospace Laboratory of Japan,

Tokyo, Japan, June 20-22, 2001. Responsible person, Joseph P. Veres, organization code 2900, 216-433-2436.

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This publication is available from the NASA Center for AeroSpace Information, 301-621-0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

A high-fidelity simulation of a commercial turbofan engine has been created as part of the Numerical Propulsion System

Simulation Project. The high-fidelity computer simulation utilizes computer models that were developed at NASA Glenn

Research Center in cooperation with turbofan engine manufacturers. The average-passage (APNASA) Navier-Stokes

based viscous flow computer code is used to simulate the 3D flow in the compressors and turbines of the advanced

commercial turbofan engine. The 3D National Combustion Code (NCC) is used to simulate the flow and chemistry in the

advanced aircraft combustor. The APNASA turbomachinery code and the NCC combustor code exchange boundary

conditions at the interface planes at the combustor inlet and exit. This computer simulation technique can evaluate engine

performance at steady operating conditions. The 3D flow models provide detailed knowledge of the airflow within the fan

and compressor, the high and low pressure turbines, and the flow and chemistry within the combustor. The models

simulate the performance of the engine at operating conditions that include sea level takeoff and the altitude cruise

condition.

14. SUBJECT TERMS

Gas turbine engines; Computational fluid dynamics; Turbocompressions; Turbines;

Combustion chambers

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