A kW-level integrated propulsion system for UAV powered by PEMFC with inclined cathode flow structure design

•A 1 kW-level PEMFC powered propulsion system with an inclined cathode flow structure is developed.•The inclined cathode flow structure is designed to replace the axial fan in the PEMFC system for power density enhancement.•Design analysis of different powers for integrated propulsion system with inclined cathode flow structure is conducted.•The cathode flow field of PEMFC under different air intake conditions are measured.•Output performance test of the integrated propulsion system with designed parameters is conducted. Open-cathode air-cooling polymer electrolyte membrane fuel cells (PEMFCs) with the lightweight and simple structure are widely used in state-of-the-art UAVs. In this work, a 1 kW-level PEMFC powered propulsion system with an inclined cathode flow structure is developed. The inclined cathode flow structure uses the airflow behind the blade root of the propeller to meet the reaction and cooling requirements of the PEMFC cathode. Such design discards the cathode axial fan in the current commercial PEMFC system and reduces the parasitic power, weight and volume caused by the axial fan. Compared with the current commercial PEMFC powered propulsion system, the specific power of the 1 kW PEMFC system, power-to-weight ratio and thrust-to-weight ratio of the 1 kW integrated propulsion system are increased by 33.0 %, 23.8 %, and 18.3 %, respectively. Besides, the space in the fuselage for the fuel cells and the weight of distribution wiring, as well as the wire loss, is also significantly saved by replacing the axial fan with proposed inclined cathode flow structure.