Multifunctional fuel cell system for civil aircraft: Study of the cathode exhaust gas dehumidification

This study presents a novel cathode exhaust gas dehumidification system based on an air cycle machine (compressor, heat exchanger, cyclone, turbine) which supplies liquid water and dry ODA for the aforementioned functions. First, feasibility of the multifunctional approach, quality of the generated water and necessary level of dehumidification are discussed. Next, real fluid property data and the system thermodynamic model are presented. Feasibility of the novel system is demonstrated with a parametric study on the effect of stoichiometry, compressor pressure ratio and turbine outlet pressure. Computed results show that: the target average O2 concentration of 10.5% (vol.) is maintained at stoichiometries below λO2≤1.8; for maximum humidity ratio xmax=0.002kgH2O/kgODA there is not risk of ice formation on condenser when compressor pressure ratio is above π ≥ 2.8. Finally, an estimation of added and potentially removed weight is given, also possible system configurations are derived.