Comprehensive analysis of cathode air pressure of fuel cell powertrain system of aircraft: Performance, efficiency, and control

Abstract

Fuel cells are ideal power sources for aircraft. However, fuel cells are highly sensitive to operating pressure, which complicates the operating characteristics of fuel cells at various altitudes. A globally optimal cathode pressure control method of aircraft fuel cell powertrain system is proposed to address the abovementioned problem. Simplified PEM (Polymer Electrolyte Membrane) fuel cell and electric motor driven two stage centrifugal compressor supercharger models are designed and validated, with the fuel cell model focusing on a wide range of variable cathode air pressures and the supercharger model focusing on a wide range of altitudes, to consider both calculation accuracy and amount. Compared with a physical fuel cell model and a CFD supercharger model, the simplified model boosts the calculation speed by approximately 107 times. The performance and efficiency of the fuel cell system at different altitudes, current densities, and charged air pressures are analyzed using the simplified model. With massive 3-dimensional data, an optimal pressure strategy is proposed to ensure that the system operates at the highest efficiency at any flight altitude and system output power. A near-optimal air pressure strategy is also proposed for better system stability and lower stress at an acceptable efficiency loss. The advantage of the two strategies over the commonly used fixed pressure strategy is demonstrated using a simple flight profile, where they reduce system hydrogen consumption during aircraft take-off and climbing by up to 3.4 % and 1.5 %.