Ceiling temperature assessment of a reduced scale tunnel in the event of two hydrogen jet fires

It is critical to comprehend the safety aspects of hydrogen fuel cell vehicles (FCVs) in semi-confined and confined environments. The hydrogen jet fire is a key hazard resulting from coincidental hydrogen release from onboard storage followed by ignition. The rise in temperature and depletion of oxygen inside the tunnel may cause calamitous debacles. In this study, comprehensive computational fluid dynamics (CFD) simulations were designed to understand the interactions of multiple hydrogen fires in a confined environment. CFD simulations for hydrogen and liquefied petroleum gas (LPG) jet fires were conducted inside a reduced scale model tunnel. The model is initially validated against the experimental data for a single LPG fire scenario. A parametric study was then made to understand the impact of the fire location in the tunnel and the ventilation velocity. The results show an increasing-decreasing trend in the temperature over the two fire sources before the temperature reaches a quasi-steady state for the cases without ventilation speed. However, in the presence of ventilation velocity, the temperature rises are seen until a quasi-steady-state is reached. The vicinity of the two flames in the tunnel influences ignition proficiency, dependent on the heat feedback enhancement and air supply restriction instruments. A temperature drop was seen at the ceiling as we move along the passage length. The ventilation velocity influences the proportion of fuel and oxygen, driving the burning proficiency to either increase or decrease. The overall ceiling temperatures were seen to reduce in the presence of higher ventilation velocity. In conclusion, for hydrogen and LPG fire interaction, a distinction in the ceiling temperature pattern was seen between the two because of the disparity in the emissivity of the two fuels.