Interest in green technology to reduce CO2 and NOx emissions in aviation is increasing rapidly.  To address these environmental issues, novel fuels such as cryogenic liquid hydrogen are being explored.  However, there are some concerns around the safety of liquid hydrogen, and, as with any new technology, particularly in a safety-critical industry like aviation, a significant amount of work is needed to integrate it safely into the existing industry and infrastructure. 

A switch to a cryogenic fuel, such as liquid hydrogen or methane, has significant implications for the aviation industry: for aircraft manufacturers, fuel producers and suppliers and the supporting infrastructure at airports. Therefore, work has been carried out to examination of the impact that hazards associated with liquid hydrogen will have on the civil aviation industry have as part of the ENABLEH2 project.

The gaps in technology and knowledge, which currently serve to act as a barrier to hydrogen adoption for the industry-at-large, have been identified, and work has begun to start to address these areas of need. A serious knowledge gap identified by the initial literature survey is the definition of ignition and flammability characteristics for hydrogen under various aviation operating conditions.  Its behaviour in the low pressure, low temperature environments aircraft appears to be poorly defined. An experimental pressure vessel test rig has therefore been designed and built at LSBU, to measure the effect of low temperature and pressures on the burning velocity, flammability and MIE of hydrogen. This information is needed to inform ignition prediction, and explosion prevention and mitigation, assessment and strategies.

A Preliminary Hazard Analysis (PHA) method has been used as a tool to identify the potential hazards associated with using liquid hydrogen and assess their likelihood and severity and explore potential prevention and mitigation measures.  The PHA process has then been used to specifically identify the hazards associated with aircraft design choices and to explore potential mitigation measures that might be required for aircraft using liquid hydrogen. Preliminary hazard analysis work has also been carried out to explore the use of liquid hydrogen at airports, and the alterations and mitigations that might be needed to enable this cryogenic and flammable fuel in this complex and fast-moving environment.  

It also necessary to improve understanding of the large-scale hazards that could be posed by liquid hydrogen in aviation accident scenarios such as leaks from airport fuel storage tanks. The FLACS CFD code has therefore been applied to model large-scale liquid hydrogen spills and associated flammable gas cloud behaviour (e.g. the effect of wind speed and ground substrate type on the extent of the flammable cloud generated).


Combined Hazard Analyses to Explore the Impact of Liquid Hydrogen Fuel on the Civil Aviation Industry

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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