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Dynamic Simulation of Gas Turbine Engines. Aircraft- 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: - PowerPoint PPT Presentation
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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.