Design and Performance Analysis of a Fuel Cell Propulsion System Driven by a Hydrogen-Fired Micro Gas-Turbine

A novel design for the cathode air supply system of a fuel cell-based aircraft propulsion system is presented in this study. Herein, the state-of-the-art Electrically driven Cathode air Supply system (ECS) is replaced by a H2-fuelled micro gas turbine (GTCS) with the main goals of 1) decreased total fuel cell power demand and, therefore, 2) reduced low temperature waste heat. Therefore, no parasitic power is required to drive the cathode air supply. The proposed system design is simulated for a regional, distributed propulsion aircraft. Adaptation to other aircraft layouts is easily possible. The operating characteristics of both systems are compared and advantages of the novel architecture are quantified. The advantages are, among others, a substantial reduction of the fuel cell waste heat as well as the reduction of the overall component size within the air supply system. For the most demanding operating point take-off, fuel cell waste heat can be reduced by 25% at maximum operating pressure while heat exchanger size is decreased by up to 16% and humidifier size by up to 20%. Further synergies from the novel architecture are the possibility to use up to 45% of hydrogen from the anode exhaust in the combustor instead of recirculating or venting it. This may lead to a substantial size reduction in the anode side recirculation cycle. Considering the overall system weight, the novel system can achieve a 26% lower weight than the state-of-the-art ECS system. The fuel consumption however is up 9.6% above the ECS system due to poor thermal efficiency of the core. However, it remains to be evaluated in the context of overall aircraft design whether the advantages in component size and weight due to reduced waste heat rejection requirements can outweigh the drawbacks in fuel consumption.