Abstract: More electric aircraft impose increasing requirements on the power capacity and regulation capability of onboard electrical power systems. A dual-channel power generation system based on the high-pressure and low-pressure spools of a turbofan engine has become an important approach to enhancing onboard power supply capability. However, electrical power offtake from the two spools changes the shaft power balance and component matching points of the engine, thereby affecting thrust output, fuel economy, and stability margins. To address this issue, an off-design steady-state model of a CFM56-7B high-bypass twin-spool turbofan engine considering electrical power offtake from both the high-pressure and low-pressure spools is established. The model is combined with the droop-control-based power-sharing relationship of a dual-channel power generation system. The effects of dual-spool power offtake on engine performance and stability margins are investigated under takeoff, rotation, climb, cruise, and approach conditions. The results show that the dominant constraints on electrical power offtake vary significantly across flight conditions. Takeoff and rotation are mainly constrained by thrust retention, climb requires consideration of both thrust and high-pressure compressor surge margin, cruise is more sensitive to thrust specific fuel consumption, and approach is mainly constrained by the physical feasibility of core nozzle discharge. Accordingly, the dual-spool power-offtake scheme should be matched to the flight condition and its dominant constraints, providing a reference for the integrated matching of dual-channel power generation systems and turbofan engines in more electric aircraft.

Key words: More electric aircraft, dual-channel power generation system, power offtake, turbofan engine, off-design performance analysis, stability margin