Fuzzy Logic Control of Compressor Surge in a Turbojet Engine Model

Stable operation of a gas turbine engine's axial compressor is constrained by compressor surge and rotating stall. In order to avoid these flow instabilities, an active fuzzy logic control approach is applied to a turbojet engine model. The actuator surfaces used in the controller are the inlet guide vanes, movable stator blades, and variable spool speed with regards to the compressor; in addition, consideration is given to varying the engine inlet and exit geometries. For design purposes, in the simulation, the rotor blade geometry is also allowed to be variable. This thesis also examines the stability and control of the Moore-Greitzer model, and Gravdahl and Egeland's close coupled valve engine controller. The Moore-Greitzer model is used as a black box to create a surge detection and avoidance fuzzy logic controller that does not require a stall line. The controller responds to the fluctuations in the axial mass flow coefficient and the pressure coefficient across the compressor system, and adjusts the throttle characteristics or the closed coupled valve characteristic.