Sound and flame

Researchers make planes fit for hydrogen

Aircraft are to fly around the world on hydrogen in the future. Engineers are developing jet engines for this purpose.

(Bild: stock.adobe.com/Mario Hagen)

Climate-neutral air travel with hydrogen is set to reduce the burden on the environment in the future. Researchers at ETH Zurich have now provided the basis for the development of sustainable hydrogen aircraft engines. They tested the acoustic behavior of hydrogen injection nozzles in the laboratory under conditions similar to those that prevail at cruising altitude.

"Hydrogen burns faster than kerosene. For this reason, it produces smaller and more compact flames," Nicolas Noiray, Professor at the Department of Mechanical and Process Engineering at the Swiss Federal Institute of Technology in Zurich, was quoted as saying in a press release on Friday. This must be taken into account when designing hydrogen engines. Experiments carried out by Noiray's team are now providing an important basis for this. The team has just published its measurements in the scientific journal "Combustion and Flame".

One problem is vibrations, which engineers are trying to contain. They are caused by the mutual interaction of sound waves and flames and place a heavy load on the engine, even in today's kerosene engines. They succeeded in doing this by optimizing the shape of the flames and the geometry and acoustics of the combustion chamber.

Simulating conditions at cruising altitude
The type of fuel has a major influence on the interaction of sound and flame. Engineers and researchers must therefore also ensure that vibrations do not occur in a new hydrogen engine.

An elaborate test and measurement facility at ETH Zurich enables Noiray to measure the acoustics of hydrogen flames and predict these vibrations. As part of the EU project Hydea, in which he is involved together with the company GE Aerospace, he is testing hydrogen injection nozzles from this company. It is the first study to measure the acoustic behavior of hydrogen flames under real flight conditions.

Still many challenges
In a few years, a functioning hydrogen engine should be ready for initial tests on the ground. Later, the first aircraft will be able to take off with it. Another major challenge is to build the entire infrastructure around hydrogen aviation, for example to produce sufficient quantities of climate-neutral hydrogen and transport it to the airports.