Gas Turbine Engine Behavioral Modeling

This paper develops and validates a power flow behavioral model of a gas turbine engine with a gas generator and free power turbine. “Simple” mathematical expressions to describe the engine’s power flow are derived from an understanding of basic thermodynamic and mechanical interactions taking place within the engine. The engine behavioral model presented is suitable for developing a supervisory level controller of an electrical power system that contains the engine connected to a generator and a large interconnection of many components, e.g., a naval ship power system powered by gas turbine engines. First principles engine models do not lend themselves to the preceding control development because of their high granularity. The basis of the behavioral model development is the balance of energy flow across engine components; power flow is obtained by taking the time derivative of the energy flow. The behavioral model of a specific engine utilizes constants and empirical fits of power conversion efficiencies obtained from data collected from a high-fidelity engine simulator. Behavioral models for a GE LM2500 and an engine similar to a GE T700 are constructed; the 2-norm normalized error between the simulator and behavioral model outputs for both engines is 3.5% or less.