DESIGN AND SIMULATION MODEL OF A DIRECT SUPPLY CRYOGENIC LH2 FUEL AIRCRAFT SYSTEM FOR AIRBORNE APPLICATIONS

The development of efficient and sustainable aircraft engine fuel systems has become one of the primary aspects in achieving the long-term goal of net-zero CO2 emissions from aviation by 2050. This involves not only the choice of the operating fuel but also its storage and processing conditions. Previous studies suggest that using liquid hydrogen (LH2) can offer longer endurance for air vehicles and an effective engine cooling due to its high specific heat value compared to high-pressure systems. This work is part of the LIQORNE (LIQuid hydrogen for airbORNE application) project, which investigates a hydrogen aircraft fuel system with a direct cryogenic LH2 supply. In this regard, a system model has been developed, focusing on continuously feeding LH2 into the engine and recovering redundant fuel and engine heat for gasification and hydrogen expansion improvement. This approach helps to control the risk of icing and boil-off in the system components and allows for a more lightweight and compact system. By implementing continuous fuel circulation and incorporating a flow control valve near the engine injection, it is realistic to verify and achieve shorter full-throttle response times. The potential of this architecture lies in its efficiency and flexibility, as it uses LH2 not only as a combustion fuel but also utilizes the redundant fuel for cooling, tank pressure control, and heating for optimal expansion before injection. To provide initial approximations of the system's behavior, this paper describes a simulation model created with Simscape software for a small twin-engine medium-haul aircraft. This model focuses on component dimensions, including tank, pipes, and pump in terms of their thermodynamic behavior. The fuel properties are based on the thermophysical database CoolProp, enabling accurate calculations of phase proportion, temperature, and pressure based on real gas parameters. Through validation against previous state-of-the-art studies, the model is expected to yield initial dimensions of the system volume. Consequently, a comparison of system weight between liquid and pressure-driven architectures can be conducted, along with an assessment of potential efficiency improvements. It will also verify the feasibility of boil-off regulation by the fuel system alone. Due to the parametric model design, various study cases can be applied to find the optimum operating point and adapt to different applications.