Researchers are making jet engines fit for the hydrogen age

Europe is preparing for climate-neutral flight powered by sustainably produced hydrogen. Last 12 months, the EU launched a project to support industry and universities in the event of a hydrogen-powered medium-haul aircraft. Amongst other things, jet engines may have to be adapted to run on the brand new fuel. Today’s engines are optimised for burning kerosene.

“Hydrogen burns much faster than kerosene, leading to more compact flames,” explains Nicolas Noiray, Professor within the Department of Mechanical and Process Engineering at ETH Zurich. This needs to be taken into consideration when designing hydrogen engines. Experiments by Noiray’s team now provide a very important basis for this. The team has just published its ends in the journal Combustion and Flame.

One problem is vibrations, which engineers attempt to minimise. In typical jet engines, about twenty fuel injection nozzles are arranged across the annular combustion chamber of the engine. The turbulent combustion of the fuel there generates sound waves. These waves are reflected back from the partitions of the chamber and have a feedback motion on the flames. This coupling between the sound wave and the flames could give rise to vibrations that will induce a heavy load on the engine combustion chamber. “These vibrations can fatigue the fabric, which within the worst case could lead on to cracks and damage,” says Abel Faure-Beaulieu, a former postdoctoral researcher in Noiray’s group. “That is why, when latest engines are being developed, care is taken to be certain that these vibrations don’t occur under operating conditions.”

Simulating conditions at cruising altitude

When engineers developed today’s kerosene engines, they’d to get these vibrations under control. They achieved this by optimising the form of the flames in addition to the combustion chamber’s geometry and acoustics. Nevertheless, the style of fuel has a serious impact on the interactions between sound and flame. This implies engineers and researchers must now be sure that they are going to not arise in a brand new hydrogen engine. An elaborate test and measurement facility at ETH Zurich allows Noiray to measure the acoustics of hydrogen flames and predict potential vibrations. As a part of the EU project HYDEA, wherein he’s involved along with GE Aerospace, he tests hydrogen injection nozzles produced by the corporate.

“Our facility allows us to duplicate the temperature and pressure conditions of an engine at cruising altitude,” Noiray explains. The ETH researchers may also recreate the acoustics of assorted combustion chambers, enabling a wide selection of measurements. “Our study is the primary of its kind to measure the acoustic behaviour of hydrogen flames under real flight conditions.”

Of their experiments, the researchers used a single nozzle after which modelled the acoustic behaviour of the gathering of nozzles as it might be arranged in a future hydrogen engine. The study helps engineers at GE Aerospace to optimise the injection nozzles and to pave the way in which for a high performance hydrogen engine. In just a few years, the engine ought to be ready for initial tests on the bottom, and in the long run, it could propel the primary hydrogen fuelled aircrafts.

ETH Professor Noiray doesn’t consider the event of the engines or the event of hydrogen tanks for aircraft to be the best challenge in transitioning aviation to the hydrogen age. “Humanity has flown to the moon; engineers will undoubtely give you the option to develop hydrogen planes,” he says. But planes alone aren’t enough. One other major challenge, Noiray says, is to place in place all the infrastructure for hydrogen aviation, including producing climate-neutral hydrogen in sufficient quantities and transporting it to airports. Achieving this inside an inexpensive timeframe requires a concerted effort now.