Pre-normative research on vented deflagrations in containers and enclosures for hydrogen energy applications

Topic description

Scope:

Specific challenge: Many hydrogen-energy systems such as electrolysers, fuel cell backup systems, refuelling stations, etc. are commonly designed and integrated into containers and/or small enclosures. Such hydrogen products usually comprise high-pressure piping, fittings and components that, in case of failure in such confined and obstructed enclosures, may lead to the rapid formation of a turbulent flammable hydrogen-air mixture. If ignited, such cloud would trigger a deflagration or even a more devastating detonation. This event requires a specific attention where best to apply safety barriers to mitigate the risk from a hydrogen explosion in order to ensure the highest level of safety for hydrogen energy applications.

Explosion venting technique is commonly used in the industry to both mitigate explosion overpressure effects in the surroundings and prevent complete facility destruction and missile effects. Being able to correctly design an effective vent is an essential safety feature for fast-deploying containerized hydrogen-energy products.

Nonetheless, the European standard EN 14994 “Gas explosion venting protective systems” has a very limited range of applicability and can hardly be used for vent sizing of hydrogen-air deflagrations. Despite more recent hydrogen-air vented deflagration experiments available in the safety community, only few data are representative of real-life conditions that can be encountered in hydrogen-energy containers or enclosures. Recent work related to engineering correlations for vent sizing was carried out but still need further development to be straightforwardly applicable to hydrogen-energy enclosures.

Performing experiments in real-life industrial enclosures is thus necessary to improve vent sizing techniques for hydrogen-energy products and further develop analytic and CFD modelling tools. The experiments will have to be representative of different possible scenario/ potential hazards identified in enclosures. This includes in particular the characterisation of venting systems (e.g. doors, natural vent openings, etc.) for combustion of homogeneous hydrogen-air mixtures at different concentrations, formation and combustion of gradient mixtures, delayed ignition of turbulent hydrogen jet inside containers and enclosures, etc…

Another knowledge gap is the structural response of containers exposed to a vented explosion. The overpressure – impulse (P-I) diagram has to be modelled theoretically. Mechanical response experiments should also be performed to check the model and its assumptions.

Scope:  Conduct pre-normative research on hydrogen-air vented deflagrations in real-scale containers to prepare an International Standard on “hydrogen explosion venting mitigation systems”

Expected impact:

•             Coordinated input to an International Standard on “hydrogen explosion venting mitigation systems”

•             Safe and successful introduction of hydrogen-energy systems into the market by definition of harmonised and standardised hydrogen vent sizing requirements for installations in enclosures

•             Prediction of hydrogen explosion effects for certification and planning purposes by developing, verifying and validating analytical and CFD predictive models

Verification of models by performance of real-life hydrogen-air vented deflagrations in industry-representative hydrogen-energy enclosures and containers

International cooperation