Performance Study of an Onboard Power Generation System with Liquid Hydrogen Intercooling and Recuperation Based on Aviation Fuel Cells

Electrification in aviation imposes higher requirements for the power density and operational efficiency of onboard power systems. Conventional auxiliary power units currently face bottlenecks in both efficiency and emissions. Hybrid power systems consisting of proton exchange membrane fuel cells and gas turbines are considered a promising solution because they enable cascaded energy utilization. Integrating such hybrid systems with the main turboshaft engine represents an important technical path for improving performance. However, extracting interstage bleed air from the main engine compressor leads to propulsion power loss, and the performance of the fuel cell is significantly influenced by temperature and pressure. Therefore, quantifying the trade-off between the cost of bleed air and the gain in power generation is essential for verifying the feasibility of this technology. This paper proposes a thermodynamic model coupling a main turboshaft engine with a fuel cell and gas turbine subsystem. In this model, a novel thermal management strategy employs liquid hydrogen to cool interstage bleed air. Prior to entering the cathode, the bleed air undergoes cooling via heat exchange, while the high-temperature turbine exhaust stream concurrently preheats the hydrogen before it reaches the anode. Bleed air losses are quantified through a segmented compression work calculation, and the influence of bleed air pressure ratio, current density, and fuel utilization on overall system performance is systematically examined. System net benefit is defined as the net generated power minus the associated propulsion power penalty. The results indicate that, with suitable parameter coordination, a positive net benefit can be realized. Under typical operating conditions, the system attains a net benefit of thirty-two point two kilowatts. The proposed coupling architecture offers a theoretical reference for the design of hydrogen-based hybrid propulsion systems in aviation.