Simulation and Optimization of Zero Emission Hydrogen-Based Powertrains Using EcosimPro

Kurzfassung

The transportation and especially aviation sectors climate impact could be substantially reduced by switching its fuel to liquid hydrogen. However, due to its low boiling point (~20 K), it is a challenging fuel to handle. One of the most critical aspects is the evaporation of cryogenic liquid due to heat input from the environment, the so-called boil-off. To detect and rate all sources of boil-off losses along the liquid hydrogen power train system, simulations were performed with EcosimPro, a software tool that is widely used to simulate propellant lines in space transportation. The model that is simulated consists of a small liquid hydrogen tank an electrical heater and a fuel cell model. The dimension relates to a small aircraft / air taxi or an APU replacement for a medium sized aircraft. The scope of simulations incorporates the fueling of the lH2 tank and various mission scenarios such as long taxiing and waiting times as well as high power demands. The results show that boil-off losses during fueling are one of the most significant sources of losses along the liquid hydrogen pathway. These boil-off losses can substantially be reduced e.g. by subcooling the liquid hydrogen or by pre-cooling the tank with liquid nitrogen before the filling process. The smaller the tank, the higher are potential benefits, therefore mass savings of up to 50% of total fuel mass are possible. An experimental demonstrator that is suitable to validate the numerical simulations is currently under development. First results with liquid nitrogen as a replacement for liquid hydrogen are expected until end of 2022.