Evaluation of Air Supply Conditioning Architectures for PEM Fuel Cell Systems in Aviation

Abstract This paper investigates the cathode air supply system of a medium-range fuel cell-powered aircraft. The main focus is on determining a suitable system architecture. Based on the literature, promising humidification and cooling strategies for cathode gas preconditioning are identified and evaluated. System configurations with membrane and spray humidification as well as intercooling between compressor stages and wet compression are calculated using a thermodynamic cycle calculation model. By analysing the design parameter spaces of the cathode air supply systems, the different configurations are compared in terms of their influence on key system parameters such as specific fuel and parasitic power consumption or heat exchanger size to find the most promising architecture. Further, the operating limits of the systems at different operating pressures and temperatures are determined. The second area of focus is the identification of a suitable system design point. It is discussed that the most critical operating points of the individual components are located at different flight conditions. Therefore, off-design performance is taken into account in order to design the entire system. A model based on the constant mass flow method is introduced to calculate steady state operating points for the system using membrane humidification. It can be seen that the turbo components have their design point at top of climb operating point, while the heat exchanger has to be designed for the maximum waste heat at take-off and the humidifier for the most critical operating point in terms of membrane water content at cruise.