Liquid hydrogen storage design trades for a short-range aircraft concept

Abstract

Preliminary design trades for the liquid hydrogen storage system of a short-range aircraft are presented. The hydrogen storage system is integrated in wing pods, which additionally carry the propulsion powertrain composed of a gas turbine, an electric motor, a gear box and a propeller. The shape of the hydrogen storage tank is identified as a main design driver as well as the maximal pressure and insulation type. The variation of these parameters influences the aircraft performance and the insulation efficiency. In this study the main effects driven by the design parameters are addressed using conceptual and preliminary methods: Models are carried out for the storage mass, additional drag, propeller efficiency loss and the dynamical thermodynamic behavior of the liquid hydrogen storage. These effects are coupled making an integrated design method necessary. For the sizing of the liquid hydrogen storage a multidisciplinary workflow is set up calculating the block fuel for a design mission of 1500 nm. Aircraft sensitivities are applied covering the main effects on the block fuel for the design mission. The trade-off study reveals the opposing trend between insulation efficiency and aircraft performance. For the insulation architecture based on rigid foam the penalties implied by the storage tank on aircraft level and the penalties due to vented hydrogen during the design mission can be balanced. An optimal design regarding the minimization of block fuel can be found for a maximal pressure level of 2.5 bar, a wing pod diameter of 2.4 m and a total insulation thickness of about 11 cm. The application of multilayer insulation avoids venting during the design mission, but has an increased penalty on the aircraft performance compared to the insulation architecture based on rigid foam. Besides the criterion of minimal block fuel, the dormancy time is compared, which indicates the thermal efficiency. Applying multilayer insulation the dormancy time can be increased significantly calling for a discussion of operational requirements for hydrogen powered aircraft.