Mitigating Impact of Bleed and Power Extraction with More Electric Architectures 2016-01-1991
Aircraft subsystems essential for flight safety and airworthiness, including flight controls, environmental control system (ECS), anti-icing, electricity generation, and starting, require engine bleed and power extraction. Predictions of the resulting impacts on maximum altitude net thrust(>8%), range, and fuel burn, and quantification of turbofan performance sensitivities with compressor bleed, and with both high pressure(HP) rotor power extraction and low pressure(LP) rotor power extraction were obtained from simulation. These sensitivities indicated the judicious extraction options which would result in the least impact. The “No Bleed” system in Boeing 787 was a major step forward toward More Electric Aircraft (MEA) and analysis in this paper substantiates the claimed benefits. Also presented is the potential for future mitigation of impacts, including use of LP rotor power extraction for conserving both performance and compressor stall margin, increasing engine efficiency with on-line control effector perturbations, use of batteries for electric actuation of systems and taxiing, and identification of opportune engine operating conditions for charging batteries. Comparison is made between traditional architecture, Boeing’s “No Bleed” MEA and an envisioned future MEA. Discussion includes potential for further improvement in fuel burn, maintainability, and reliability with advanced MEA concepts which would reduce secondary power requirements. An additional objective was literature survey to learn from the excellent works of others. The nominal levels of both pneumatic and mechanical extractions for both traditional aircraft and MEA were derived from published literature. In future designs an integrated effort between engine and aircraft companies will be necessary to perform the required trade studies to determine improved architectures.