Effect of Accessory Power Take-off Variation on a Turbofan Engine Performance.

摘要

Engine fuel efficiency of aerospace vehicles can be reached by different techniques. One way to do that is to reduce aircraft subsystems power supply effects on the engine performance. Previous research work has showed that extracting bleed air from the high pressure compressor exit is more efficient than extracting the equivalent amount of energy from the low pressure spool shaft. A high bypass turbofan engine was modeled using the Numerical Propulsion System Simulation (NPSS). The baseline engine performance was evaluated at different flight conditions of Mach number and altitude. To better understand the effect of air bleed take-off and shaft power extraction, four simulation cases are investigated at constant fuel flow and constant high pressure turbine inlet temperature setting. The first two cases extract bleed air from compressors while the last two cases extract equivalent power from engine shafts. Appropriate model modifications and port connections are made to consider the power extraction method. The effect of a bleed air fraction off- take from 1% to 10% and equivalent shaft power extraction on engine performance of thrust and thrust specific fuel consumption was investigated. Engine compressors operating lines and HPT inlet temperature were also checked. Results proved that shaft power extraction is more efficient for engine performance than bleeding an equivalent air fraction from compressors. Those results were shown to be consistent with a simulation run on the AEDsys simulation tool.