Reaction Engines and the Science and Technology Facilities Council of Great Britain (STFC) completed a concept study on the usefulness of using ammonia as an aviation fuel.

By combining the heat exchange technology of reaction engines with advanced catalysts from STFC, they hope to produce a a sustainable, low-emission powertrain for the aircraft of the future.

Modern jet engines use a variety of kerosene-based fuels that have very high energy density that can propel planes far beyond the speed of sound and carry passengers and cargo around the world.

Unfortunately, these fuels are also derived from fossil fuels and produce significant emissions of carbon dioxide, which the aviation industry and many governments have pledged to drastically reduce by 2050.

One way to achieve these reductions is to seek alternatives to conventional aircraft fuels. The problem is that most of these alternatives have a much lower energy density than standard aviation fuels, in addition to other drawbacks.

For example, current battery technology would require future aircraft to be very small, short range, and with low payload capacity.

While liquid hydrogen could be a viable alternative, but such a quantity would have to be transported that planes would have to be completely redesigned and new infrastructure would have to be built.

The idea of ​​using ammonia as an aviation fuel is not new. Although it is only a third of the energy density of diesel, it is relatively easy to liquefy and store, and was already in use in the famous X-15 rocket plane, propelling it into space during a series of suborbital missions in the 1950s and 1960s. Plus, it’s carbon free.

The hard part is finding an economically viable way to use it in aviation. To solve this problem, Reaction Engines produced a new propulsion system based on the heat exchange technology it developed for its SABER hypersonic engine, which was evaluated by STFC’s Rutherford Appleton laboratory near Didcot in the ‘Oxfordshire.

In this new system, ammonia is stored as a refrigerated liquid under pressure in the wings of the aircraft, as kerosene-based fuel does today. The heat collected from the engine by the heat exchanger would heat the ammonia as it is pumped and introduced into a chemical reactor where a catalyst breaks down some of the ammonia into hydrogen. The mixture of ammonia and hydrogen is fed into the jet engine, where it burns like conventional fuel, although emissions mainly consist of nitrogen and water vapor.

According to Reaction Engines, the energy density of ammonia is high enough that the aircraft does not require major modifications and the engine can be overhauled in a relatively short time. A ground test is underway with a first flight in a few years.

The combination of reaction engine heat exchange technology and STFC’s innovative catalysts will enable the development of a rule-changing class of environmentally friendly ammonia-based aircraft propulsion systems. Our study showed that an ammonia-fueled jet engine could be retrofitted from currently available engines, and ammonia as a fuel does not require a complete rethinking of civilian aircraft design as we know it today. ‘hui. This means that a rapid transition to a sustainable, low-cost aviation future is possible; Ammonia planes could be available for short-haul routes well before 2050.

Dr James Barth, Engineering Manager at Reaction Engines.

More information: www.reactionengines.co.uk