Researchers in Switzerland have been exploring how to make jet engines that can cope with hydrogen as a fuel.
Hydrogen burns faster than kerosene which leads to more compact flames. This is troublesome as when fuel combusts in a jet engine, sound waves get generated, these then get reflected back from the walls of the combustion chamber, leading to a feedback action on the flames. With more compact flames, it can lead to vibrations, inducing a heavy load on the engine combustion chamber, risking cracks and damage as the material gets fatigued, making this an increasing area of interest for developers.
A research team at the ETH Zurich have been making use of an in-house test and measurement facility that allows them to measure the acoustics of hydrogen flames and predict potential vibrations. It forms part of the EU project, HYDEA, with Nicolas Noiray, Professor in the Department of Mechanical and Process Engineering carrying out tests to help GE aerospace optimise its injection nozzles, paving the way for a high-performance hydrogen engine.
Marking the first study of its kind to measure the acoustic behaviour of hydrogen flames under real flight conditions, the researchers have used a single nozzle – there are 20 in a jet engine – before modelling the acoustic behaviour of the collection of nozzles as it would be arranged in a future hydrogen engine. It is expected that “in a few years” the engine will be ready for initial tests on the ground, ahead of potential hydrogen fuelled aircrafts.
Noiray highlighted that it is not just developing hydrogen plans, however, with putting the entire infrastructure in place for hydrogen aviation a challenge. This includes producing climate-neutral hydrogen in sufficient quantities and then transporting it to airports. To achieve all of this in a sufficient timeframe means a concerted effort is needed now.
With batteries too heavy for high-performance aircraft, Noiray pointed out storing the energy to fly 200 passengers long distance with hydrogen in cryogenic tanks works out around thirty times less heavy. Noiray added: “In the coming decades, only small aircrafts with very low payload capacity will be battery-powered. For passenger and cargo aircraft, synthetic fuels are the only alternative to today’s kerosene, and hydrogen is the most economical to produce sustainably.”
