TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

Dynamic Simulation of Gas Turbine EnginesAircraft- and power generation gas turbines have to meet increasingly high efficiency and performance requirements. In addition, in the course of adverse dynamic operations such as start-up, shutdown and load changes the engines are subject to:

Extreme aerodynamic, thermal and mechanical stresses. Design point calculations do not account for additional stresses originating from

dynamic operation

A non-linear dynamic computational tool provides detailed essential information regarding dynamic behavior of gas turbine engines under off-design or any extreme adverse operation condition.

TPFL has developed a powerful computational tool, GETRAN Further enhancement of GETRAN is a Ph.D. topic

TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

Gas Turbine Engines, Generic Components, Modeling

High Efficiency Power Generation Gas Turbine Engine with Sequential

Combustion

Twin-Spool Aircraft Gas Turbine Engine

TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

Components Common to All Gas Turbine Engines

Gas turbine components of different geometric configurations fulfill the same function and are described by the same set of conservation equations.

This common characteristic is utilized for code development and architecture of GETRAN, which is A GEneric modularly structured computer program for Simulating the

TRANsient behavior aircraft and power generation gas turbine engines

Conventional Combustion Chamber

EV-Combustiors

Inlet nozzle Multi-stage compressor

Exit diffuser

Multi-stage turbine

GeneratorInlet nozzle

Multi-stage compressor

TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

Gas Turbine Components, Generic Modules

representation representationTurbine module Turbine stage Velocity diagram Velocity diagram

representationCompressor stage Turbine module

representation

3 = Primary zone4 = Secondary zone

1 = Inlet diffuser2 = Swirl generator

5 = Liner6 = Exit

Combustor component

= Heat flow generated by fuel combustion

= Heat flow generated by flame radiation

= Total secondary air mass flow

= Primary air mass flow

= Fuel mass flow

= Mixing mass flow

mP

Fm

M

m

m

Q

QF

RF

S5 = Secondary flow zone

Combustor module representation

6 = Secondary liner

3 = Combustion zone

2 = Swirl generator

1 = Fuel inlet

4 = Primary liner

7 = Mixing zone8 = Exit

Casing with stator cooling channels

= Secondary air mass flow

m

Example of Components and module representation in GETRAN: Uncooled and cooled turbine stage, compressor, combustion chamberFor more details refer to Text: M.T. Schobeiri Turbomachinery Flow PhysicsAnd Dynamic Performance, Springer-Verlag First Edition (Second Edition inPress)

TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

Non-linear Dynamic Engine Simulation Steps Step 1: Expedite the engine hardware components:

No. of spools No. of shafts, May be different from the no. of spools No. of compressors stages on each spool No. of turbine stages on each spool No. of combustors No. of diffusers, nozzles, recuperators, controllers etc.

Step 2: Generate the schematics of the engine that includes all modules with addressing.

Step 3: Provide a detailed input file that accounts for the geometry of the entire engine and some components characteristics at design point.

Step 3: Based on the geometry given, above GETRAN calculates the behavior at the design and any adverse off-design operation prescribed by the user.

An example shows, how the simulation works.

TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

Non-linear Dynamic Engine Simulation Steps

Example: Simplified engine decomposition showing major components

JT-2SZO

mF

Sm

Pm mS1 Sim Mm

Am Fm

25

63

4

m1m3

7

Inlet

LP-compressor stage

HP-compressor stage

Combustion chamber LP-turbine stage

HP-turbine stageCooled HP-turbine stage

Exit

Am

2m

Fm = Fuel mass flow m = Air mass flow

A

m = Primary air mass flowP

m = Secondary air mass flowS

TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

Non-linear Dynamic Engine Simulation Steps

Example: Simplified engine decomposition showing major componentsSimulation of a twin-spool Core engine

C21

8 9 10 11 12 13

C22 C23 C24 C25

2 3 4 5 6 7

C C12 C13 C14 C15

1

14 15 16 17

23T22T21T

18 19 20 21

13T12TT

22

S

S2

CC1

FT

FVVB

VB 11

Mul

tivar

iabl

e C

ontro

l Sys

tem

Similation Schematic of a Twin-Spool Core Engine, Module Addressing

T

FT = Fuel tank

VF i

S i

NiNS

i j

BV = Bypass valveC = j compressor stage of i spool

D = Diffuser

Fuel valveNozzleSpeed sensorShaftj turbine stage of i spoolth th

====

CC = Combustion Chamber

= Signal flow= Air flow= Gas flow= Fuel flow JT-2S2S1

Note: GETRAN requires the Design point data to simulate any type of adverse off-design Operation conditions

TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

Modeling Technology: Example Combustion Chamber

Each component is modeled by a set of partial differential equations

For the above combustion model, we have system of 7 PDEs: 3 PDE on the air (cold side blue),

3 PDE on hot (gad side red), 1 PDE the metal side

A complete gas turbine engine has several system of PDEs.The type of adverse operation condition determine the boundary conditions

Simulation Schematic of a Jet Engine Combustion Chamber

Physical components of a combustion ChambermF

Sm t

mAPm mS1

1 2 3

SjmMm

Am Fm

4 5 6

Q = Heat generated by flame radiation

Q = Heat generated by fuel combustion

m = Total secondary air mass flow

Q

S

P

1

mF

m

5432

InmPT

Stm m

m = Primary air mass flow

m = Mixing mass flow

m = Fuel mass flowF

M

P

St

RF

jF

j

876

mM

jF

mmP

StmF

j

mOutOUTPOUTT

1 = Inlet diffuser 2= Swirl generator 3= Primary zone (red)4 = Secondary zone (blue) 5 = Liner 6 = Exit

QRFj

mSt

o

In

oIn

1: Fuel inlet 2: Swirl generator 3: Combustion zone 4: Segments5: Secondary air zone 6: Casing 7: Mixing zone

Modular representation

TPFL: The Turbomachinery Performance and Flow Research LaboratoryTexas A&M University

M. T. Schobeiri

One Example of an Adverse Operation

For forcing a gas turbine with split shaft into rotating stall and surge

Time (s)

/

D

0 2.5 5 7.5 10 12.5 150.80

0.85

0.90

0.95

1.00

1.05

1.10

Gas generator shaft

Power shaft

Time (s)

Pow

er(M

W)

0 2.5 5 7.5 10 12.5 15-20

-10

0

10

20

30

40

Gas generator shaft

Gas generator power response

Given power turbine schedule

Power shaft

Time (s)

Com

pres

sorM

ass

Flow

s(k

g/s)

0 5 10 15-40

0

40

80

120

160

LP-Compressor

Time (s)

Com

pres

sorM

ass

Flow

s(k

g/s)

0 5 10 15-40

0

40

80

120

160

IP-Compressor

Note: the high frequency surge with intermittently positive and negative mass flow GETRAN, row-by-row compressor and turbine component calculation.