HELICOPTER ENGINE OPTIMIZATION FOR MINIMUM MISSION FUEL BURN

摘要

The paper presents an approach for optimizing the design point inlet mass flow rate and overall pressure ratio of a turboshaft engine in order to minimize fuel burn over a specific mission of a medium transport-utility helicopter engine. The method employs performance models of the helicopter and associated turboshaft engines and is suitable for the preliminary design of a new engine or the re-design of an existing one. It uses empirical correlations to account for changes in turbomachinery component efficiencies and engine/helicopter weight due to the change of inlet corrected mass flow from a reference value. The turbine cooling flows are adjusted according to the specified upper limit of turbine rotor inlet temperature. The surge margin must be within a specified value while pressure ratio changes must allow the re-introduction of cooling/sealing air flows back into the main flow. Regarding the mission, the cruise altitude and total distance travelled are fixed while the velocity of best range during cruise and the velocity of best endurance and maximum rate of climb are recalculated based on the new helicopter weight due to changes in engine size and required mission fuel. The total reduction in mission fuel burn depends on the limits set by the designer.