Numerical analysis of release, dispersion and combustion of liquid hydrogen in a mock-up hydrogen refuelling station

Computational Fluid Dynamics (CFD) simulations of hydrogen dispersion and combustion in accident scenarios in a mock-up liquid hydrogen (LH2) refuelling station have been performed with the codes ADREA-HF and REACFLOW. The assumed accident scenarios are caused by a hose break during LH2 car refuelling. Two main configurations have been taken into account: a mitigated case and a non-mitigated case. For each configuration, 5 different ambient conditions are assumed: a case with no wind at all and four cases with a 5 m/s wind speed, coming from the south, north, east and west direction. The numerical simulations show the effect of the wind on the dispersion and explosion of the hydrogen flammable cloud. The effect of ignition position has also been investigated.The expectation that the wind plays a positive role in increasing the dispersion of the flammable cloud and therefore in reducing the overpressures in case of explosions does not hold true for all wind directions. Depending on the wind direction and on the station layout, the wind can have the effect of trapping the flammable cloud with more reactive concentrations and higher level of turbulence within the station, generating a similar level of overpressure as in the stagnant case although the amount of flammable mixture is much smaller than in the stagnant case.