RACHEL (Robustly Achievable Combustion of Hydrogen Engine Layout

The RACHEL project builds on previous technology development in terms of both practices and the partnership, bringing a mix of large OEM's (Spirit Europe and ITP UK), SME's (Causeway and Reaction), research and Academia (NCC and various universities) plus subtiers of UK suppliers, all bringing novelty and agile working. The aim is to develop technologies and architectures that deliver an effective and practical hydrogen combustion gas turbine powerplant able to operate safely, practically and reliably with Liquid H2 fuel across the full operating range, and to deliver a commercially viable product. The UK government 10 Point Plan for a Green Industrial Revolution, and Jet Zero pushes forward the goal of sustainable air travel. Similarly, the Aerospace Technology Institute has called on the UK aviation industry to prioritise sustainability and lead action on environmental imperatives. Transition to alternative energy sources to today's kerosene is regarded as one of the technology priorities, and hydrogen is one fuel that could power aircraft in the coming 10-15 years. Particularly, development of a hydrogen-fuelled gas turbine combustion system has been identified as a key enabler for zero carbon emission flight, as gas turbine powered aircraft currently account for 96% of today's aviation carbon emissions.

This is far from easy. Despite the advantage of being a very clean fuel, producing almost pure water as an exhaust product, hydrogen unfortunately has a very low energy density compared to kerosene, meaning that the fuel will have to be in the form of a cryogenic liquid to enable aircraft to fly any appreciable distance. The extremely low temperature of liquid hydrogen, -253 °C, is an incredibly harsh environment for the engine components, and many technological challenges will have to be overcome to produce a hydrogen-powered gas turbine that has the same exacting requirements of quality, performance, reliability and safety as today's engines.

Combustion of hydrogen brings many challenges, both in terms of the transportation of the hydrogen fuel (cryogenic and gaseous) and also the heat management and secondary and tertiary oil systems. As the system leverages electrical power, the incorporation of electrical systems and the integration into the powerplant is key in this project. Additionally, innovative tank solutions will not only develop solutions capable of gaseous fuel storage but will also solve the issue of purging media storage.

The exciting project is jointly funded through contribution from the project partners and UK government agencies, BEIS, Innovate UK and ATI.