Experimental investigation of turbojet-engine multiple-loop controls for non-afterburning and afterburning modes of engine operation

Donald B. Kirsch, Leon M. Wenzel, Clint E. Hart
naca-tn-4159
Jan 1958


An experimental investigation of turbojet-engine performance with several configurations of interacting multiple-loop controls was conducted to determine the mode of control required for obtaining optimum rotor speed and turbine-discharge temperature transient response characteristics during (1) thrust increase and (2) afterburner ignition by manipulation of engine fuel flow and exhaust-nozzle area. The engine operating point chosen for examining the control systems was near the rated-thrust level. Effective increases in engine thrust were obtained by rapidly opening the nozzle area while simultaneously increasing engine fuel flow. Following the afterburner ignition, opening the nozzle area rapidly while holding an esentiallly constant engine fuel flow practically eliminated compressor surge tendencies. Good engine transient performance characteristics were obtained with a control system in which engine speed was controlled by manipulation of exhaust-nozzle area and turbine-discharge temperature was controlled by manipulation of engine fuel flow. An alternate control system, which gives acceptable, although more oscillatory, transient responses, was the double-loop configuration in which speed was controlled by manipulation of engine fuel flow, turbine-discharge temperature was controlled by manipulation of exhaust-nozzle area, and a noninteraction gain term was incorporated from the speed to the temperature control loops.

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