Safety assessment of hydrogen jet fire scenarios within semi-confined spaces

Hydrogen fuel cell vehicle (HFCV) technology poses great promise as an alternative to significantly reduce the environmental impact of the transport sector’s emissions. However, hydrogen fuel cell technology is relatively new, therefore, confirmation of the reliability and safety analysis is still required, particularly for fire scenarios within confined spaces such as tunnels. This study applied the computational fluid dynamics (CFD) simulations in conjunction with probabilistic calculation methods to determine the associated thermal risk of a hydrogen jet fire in a tunnel and its dependency on scenarios with different tunnel slopes, longitudinal and transverse ventilation velocities, and fire positions. A large-scale model of 102 m in which the effects of outlined parameter variations on the severity of the fire incident were analysed. It is found that both tunnel ventilation techniques and slope were critical for the effective ejection of accumulated heat. With ventilation playing a primary role in the ejection of heat and gas and slope ensuring the stability of the ejected heat, probabilities of thermal burns were found to be reduced by up to approximately 35% with a strong suggestion of critical combinations to further reduce the dangers of hydrogen tunnel fires.