Combustion Safety (Part 2)

Date: 30th of June 2021, 4pm

Professor Jennifer Wen (University of Warwick): Hydrogen combustion in the context of fire and explosion safety: overview of previous work, some knowledge gaps and new development

With hydrogen recognised as having an important role in reducing greenhouse gases, its safety as a highly flammable gas has attracted considerable international efforts. The presentation will give an overview of previous work of my team and others on spontaneous ignition in pressurised hydrogen release, hydrogen jet flames and explosions including flame acceleration and deflagration to detonation transition. References will be made to some knowledge gaps in general and in relation to hydrogen energy applications in the UK. The second part of the presentation will outline some more recent development in relation to cryogenic liquid hydrogen. The high density of hydrogen in its cryogenic liquid phase (CryoLH2) makes its storage and transport in such state a viable option. However, there are safety concerns related to accidental releases of CryoLH2 which is typically −252.87 °C and evaporates with a volume expansion of 1:848. As CryoLH2 is typically stored in pressures from 10 to around 35 bar, ignition of accidentally released CryoLH2 would result in jet flames or even turbulent deflagrations in the case of delayed ignition. As part of the PRESLHY (Pre-normative REsearch for Safe use of Liquide Hydrogen) project funded by the EU’s Fuel Cell and Hydrogen Joint Undertaking, my team is conducting large eddy simulations of ignited cryogenic hydrogen jets using open-source computational fluid dynamics code OpenFOAM. A range of release scenarios with different ignition locations have been considered. The predicted evolution from ignition, initial development of the flame kernel to fully developed jet flames or turbulent deflagrations will be presented and compared with some experimental observations. Finally, from our current numerical study of pulsating flame spread over liquid fuels, I will provide an outlook of its potential extension to address flame spread on liquid hydrogen pools.