Lower risk approach for low emission passenger aircraft : combined LH2 and kerosene propulsion

Abstract

Research question: Airbus proposed "ZEROe" based on "disruption" and "giant leaps" but failed. Main argument: The hydrogen infrastructure at airports is not ready. What are the lessons learned? --- Idea: Instead, the idea is to use a conventional A320 type aircraft driven by conventional turbofan engines. 20% of the fuel tank's kerosene energy is substituted by LH2. As such, the volume of the additional LH2 tanks needed is minimized and can easily be integrated. The engine only needs a combined kerosene/LH2 combustor. This minimizes new technology needs and risks and stays within established experience with turbofan engines. Reliability, performance, engine life, and maintenance procedures stay the same. Emergency thrust requirements and thrust response times can be fulfilled. For a standard 900-nm-mission, CO2 emissions are reduced by approximately 50%. From airports without LH2 infrastructure, aircraft can operate with kerosene. In contrast to full hydrogen airplanes, this concept has no infrastructure limitations. --- Findings: Fuselage mounted LH2 tanks are possible as well as roof mounted tanks. The latter have the advantage that the LH2 tanks are located outside of the pressure cabin and not too far aft (CG). In case of a fire, hydrogen flames would rise away from cabin and occupants. To replace 20% of the kerosene by LH2 fuel of the same energy, the LH2 tank volume is approximately 20 m³. For each flight, the LH2 tanks are filled completely. For the missing energy for the flight, kerosene is used. Consequently, the shorter the mission, the higher the CO2 reduction. For a standard 900-NM-mission CO2 savings are about 50%. This reduces to about 15% when all tanks are full. Necessary is a dual fuel system and dual fuel combustor arrangements (staged or combined fuel injection). --- Summary: Combined kerosene and LH2 combustion could be a viable step to reduce CO2 emissions for passenger aircraft.