Design of Fuel Cell Systems in Aviation

The use of polymer electrolyte membrane fuel cells (PEMFC) to generate propulsion power for future aircraft represents a promising approach to reducing carbon emissions caused by the aviation sector. The design of a PEMFC system requires a detailed consideration of the individual subsystems, such as the air supply and thermal management system (TMS). These subsystems have a significant impact on performance, parasitic power requirements, and system mass. For this reason, a comprehensive system analysis is required to evaluate the effects on aircraft performance for the entire flight mission. The first objective of this part, Part II, is the integration of the components designed previously into the overall system calculation to cover interdependencies. For this purpose, the off-design performance of the air supply compressor, turbine, and thermal management is considered for a flight mission analysis on a standard and hot day scenario. Thereby, the effects on the propulsion power demand of the aircraft due to component masses, parasitic powers, and additional drag caused by the ram air heat exchanger are taken into account. The overall design process is iterative, as updated aircraft power demand affects the boundary conditions for the component design. The second objective is to evaluate the influences and sensitivities of different operating strategies, power densities, as well as heat exchanger pressure losses on key system parameters such as fuel consumption, waste heat, and system mass. In addition, a weighted mission-specific efficiency is defined in order to facilitate a fast, yet application-oriented assessment of turbo component designs.