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Research Papers: Gas Turbines: Turbomachinery

Gas Turbine Engine Behavioral Modeling

[+] Author and Article Information
Richard T. Meyer

School of Mechanical Engineering,
Purdue University,
West Lafayette, IN 47907
e-mail: rtmeyer@purdue.edu

Raymond A. DeCarlo

School of Electrical and Computer Engineering,
Purdue University,
West Lafayette, IN 47907
e-mail: decarlo@ecn.purdue.edu

Steve Pekarek

School of Electrical and Computer Engineering,
Purdue University,
West Lafayette, IN 47907
e-mail: spekarek@purdue.edu

Chris Doktorcik

School of Electrical and Computer Engineering,
Purdue University,
West Lafayette, IN 47907
e-mail: cdoktorc@purdue.edu

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received April 30, 2015; final manuscript received May 20, 2015; published online July 7, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(12), 122606 (Jul 07, 2015) (11 pages) Paper No: GTP-15-1152; doi: 10.1115/1.4030838 History: Received April 30, 2015

This paper develops and validates a power flow behavioral model of a gas turbine engine (GTE) composed of a gas generator and free power turbine. The behavioral model is suitable for supervisory level (optimal) controller development of the engine itself or of electrical power systems containing gas-turbine-generator pairs as might be found in a naval ship or terrestrial electric utility plant. First principles engine models do not lend themselves to the supervisory level control development because of their high granularity. For the behavioral model, “simple” mathematical expressions that describe the engine's internal power flows are derived from an understanding of the engine's internal thermodynamic and mechanical interactions. These simple mathematical expressions arise from the balance of energy flow across engine components, power flow being the time derivative of energy flow. The parameter fit of the model to a specific engine such as the GE LM2500 detailed in this work utilizes constants and empirical fits of power conversion efficiencies obtained using data collected from a high-fidelity engine simulator such as the Gas Turbine Simulation Program (GSP). Transient response tests show that the two-norm normalized error between the detailed simulator model and behavioral model outputs to be 2.7% or less for a GE LM2500.

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References

Figures

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Fig. 1

GTE diagram with working fluid stations numbered: inputs are ambient air and fuel and output is exhaust gases

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Fig. 2

Energy flow diagram for gas generator: circles indicate energy balance, circles with arrows indicate control valves, and the double-ended arrow to the left of Espool,stored indicates that spool energy can increase and decrease

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Fig. 3

Power flow diagram for gas generator: circles indicate conservation of power constraints and circles with arrows indicate control valves

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Fig. 4

Energy flow diagram for free power turbine where the double-ended arrow to the right of Epts,stored indicates that shaft energy can increase and decrease

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Fig. 5

Power flow diagram for free power turbine

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Fig. 6

Comparison of normalized LM2500 GSP and GTBM simulated power responses at 278 rpm (29.1 rad/s): (—) GTE behavioral model and () GSP

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Fig. 7

Comparison of normalized LM2500 GSP and GTBM simulated power responses at 639 rpm (66.9 rad/s): (—) GTE behavioral model and () GSP

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Fig. 8

Comparison of normalized LM2500 GSP and GTBM simulated power responses at 1000 rpm (104.7 rad/s): (—) GTE behavioral model and () GSP

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Fig. 9

Error between normalized LM2500 GTBM and GSP Pload(t) for Npt of 278 rpm (29.1 rad/s), 639 rpm (66.9 rad/s), and 1000 rpm (104.7 rad/s)

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Fig. 10

Normalized LM2500 GSP model simulation weak-coupling check with normalized shaft speeds (upper) and normalized power turbine absorbed power and station 4 power (lower): (—) N¯PT (upper)/P¯load (lower), () N¯gg (upper)/P¯wf,4 (lower), and (– –) superimposed power turbine load

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