Accessory Load Capability of the Free Turbine Engine with Variable Geometry Power Turbine 640369
Extraction of variable amounts of power from the gas producer shaft of a free power turbine engine with fixed turbine geometry causes over- or under-temperature problems (which mean curtailment of operating range with an associated power penalty). Gas producer shaft power extraction also increases the time required for power response (slower gas producer acceleration). These problems are discussed for a typical vehicular engine and a solution of them using a variable position power turbine nozzle is described. Factors influencing the selection of control parameters, for regulation of the variable nozzle during steady state and transient operation, are discussed and a practical control concept is described.