Sensitivity analysis of the air compression system for a fuel cell-powered regional aircraft

Abstract

One promising concept for a hydrogen-powered regional aircraft is to convert the hydrogen’s chemical energy into electricity using fuel cells, which in turn drive propellers with electric motors. Proton exchange membrane (PEM) fuel cells are considered the most mature type of fuel cells. They convert pure gaseous hydrogen and ambient air to electricity, waste heat and water. Because their efficiency depends on the oxygen partial pressure, these fuel cells are typically operated at increased pressures of 1 to 3 bar (absolute). To achieve these internal air pressures at the fuel cell inlet at increased flight altitudes, an air compression subsystem is required, which typically includes an air inlet, compressor and air cooler. This contribution investigates the effects of the air compression subsystem on the performance of the overall fuel cell system in a hydrogen powered regional aircraft concept developed by DLR. By extending a detailed system simulation model [1], the compression subsystem’s mass and auxiliary power consumption is assessed for different flight phases. The shift of the compressor map for different states of the supplied air is investigated experimentally in order to validate the scaling approach that is used in the system simulation model. The outcome of this analysis are detailed sensitivity studies on the effect of the individual components on the overall system performance, which in turn allows to identify the most promising metrics and approaches for further improvements to the operation and design of such systems. [1] M. Schröder, F. Becker, J. Kallo, and C. Gentner, Optimal operating conditions of PEM fuel cells in commercial aircraft, International Journal of Hydrogen Energy, vol. 46, no. 66, pp. 33218-33240, 2021, doi: https://doi.org/10.1016/j.ijhydene.2021.07.099.