Conceptual Design of a Hydrogen-Hybrid Dual-Fuel Regional Aircraft Retrofit

A wide range of aircraft propulsion technologies is being investigated in current research to reduce the environmental impact of commercial aviation. As the implementation of purely hydrogenpowered aircraft may encounter various challenges on the airport and vehicle side, combined hydrogen and kerosene energy sources may act as an enabler for the first operations with liquid hydrogen propulsion technologies. The presented studies describe the conceptual design of such a dual-fuel regional aircraft featuring a retrofit derived from the D328eco under development by Deutsche Aircraft. By electrically assisting the sustainable aviation fuel (SAF) burning conventional turboprop engines with the power of high-temperature polymer-electrolyte fuel cells, the powertrain architecture enables a reduction of SAF consumption. All aircraft were modeled and investigated using the Bauhaus Luftfahrt Aircraft Design Environment. A description of this design platform and the incorporated methods to model the hydrogen-hybrid powertrain is given. Special emphasis was laid on the implications of the hydrogen and SAF dual-fuel system design to be able to assess the potential benefits and drawbacks of various configurations with the required level of detail. Retrofit assumptions were applied, particularly retaining the maximum takeoff mass while reducing payload to account for the propulsion system mass increase. A fuel cell power allocation of 20% led to a substantial 12.9% SAF consumption decrease. Nonetheless, this enhancement necessitated an 18.1% payload reduction, accompanied by a 34.5% increment in propulsion system mass. Various additional studies were performed to assess the influence of the power split. Under the given assumptions, the design of such a retrofit was deemed viable.