Air Cooling of a Two-Seater Fuel Cells Powered Aircraft: Dynamic Modelling and Comparisons with Experiemtal Data

The application of fuel cell (FC) technology to aircraft propulsion and/or energy supply is becoming of great interest for undoubted advantages in terms of pollution emissions and noise reduction. A better understanding of problems related to fuel cells applied to aeronautics is sought by the European Commission (EC) funded project Environmentally Friendly Inter-City Aircraft Powered by Fuel Cells (ENFICA-FC). The main objective of the ENFICA-FC project was to develop and validate the use of a fuel cell–based power system for the propulsion of more-electric/all-electric aircraft. The fuel cell system was installed in the light sport aircraft Rapid 200, which was flight and performance tested. One of the key items under investigation is the simulation of the cooling system and the evaluation of fuel cell temperature. The polymer electrolyte membrane fuel cell (PEMFC) is considered to be the best candidate for the fuel cell vehicle because it has high power density, solid membrane electrolyte, and as it operates at low temperatures, it has a fast start-up. However, to generate a reliable and efficient power response and to prevent membrane degradation or damage with hydrogen and oxygen depletion, a sophisticated control technique becomes vitally important. In particular, as the ionic conduction of the polymeric membrane is a function of its degree of humidification, the stack temperature has to be carefully controlled to avoid phenomena of water evaporation, causing an increase of ohmic drop and a decrease of stack performances. The output voltage and hence the power of the fuel cell system is affected considerably by the change of the stack temperature. A simplified fluid-dynamic model has been developed and validated by computational fluid dynamics (CFD) analysis and it is used to compute the air flow to the fuel cell heat-exchanger inlet. Propeller effects are included referring to an optimal propeller specifically designed for the ENFICA-FC project. A mathematical model of the fuel cell system dynamics coupled with the fluid-dynamic model was studied in detail and experimentally validated during two flight tests of the Rapid 200-FC.