Electrically driven, Compact, Transonic Mixed-Flow Compressor for Active High-Lift Systems in Future Aircraft

This paper gives an overview of the interdisciplinary design process of an electrically-powered high-lift system for future commercial aircraft, with a focus on the mixed-flow compressor performance. Based on the requirements of the high-lift system, a multi-objective optimization is used for the aero-mechanical design of the compressor stage. The demand for high pressure ratio and efficiency, together with the constrained installation space yields an unconventional mixed-flow compressor design with a transonic flow regime. To supply the required pressurized air for the high-lift system, rotational speeds of up to 60,000 rpm are necessary according to CFD analysis. A very compact integrated prototype of the compressor system is designed, including electrical machine and power electronics with high power-to-mass ratios. Performance predictions are validated at part load. To integrate the compressor stage into the prototype, some adjustments to the geometry become necessary. Additional CFD simulations reveal a big impact of the new inlet duct on the compressor performance due to inlet flow distortion. It is assumed that a fully-integrated design process, which includes all relevant interdependencies of the different components, would yield a better overall system design. INTRODUCTION New technologies are required in order to cope with both increasing passenger numbers in aviation, and stronger regulations regarding noise and greenhouse gases. Due to its beneficial impact on both aircraft performance and noise generation, the high-lift system has great potential to contribute to a solution to these otherwise often conflicting targets. Together with a novel flexible leading-edge device, a combination of boundary layer suction and blowing over a Coanda-surface at the flap is utilized to generate high-lift in an efficient manner during take-off, approach and landing of the aircraft (Radespiel and Heinze, 2014). Figure 1 EPHLS Concept (Kauth et al., 2017b) Instead of burdening the aircraft engine with ancillary functions, the required air for the active high-lift system can be provided by compact, electrically-driven compressor systems (Teichel et al., 2015; Kauth et al., 2017a). By utilizing a boundary layer suction slot on the suction side of the airfoil as intake for the compressor, the efficiency of the active highlift system can be improved significantly (Burnazzi and Radespiel, 2015; Radespiel et al., 2016). A sketch of this