The thermal hazards from ignited under-expanded cryogenic releases are not yet fully understood and reliable predictive tools are missing. This study aims at validation of a CFD model to simulate flame length and radiative heat flux for cryogenic hydrogen jet fires. The simulation results are compared against the experimental data by Sandia National Laboratories on cryogenic hydrogen fires from storage with pressure up to 5 bar abs and temperature in the range 48-82 K. The release source is modelled using the Ulster's notional nozzle theory. The problem is considered as steady-state. Three turbulence models were applied, and their performance was compared. The realizable k-ε model showed the best agreement with experimental flame length and radiative heat flux. Therefore, it has been employed in the CFD model along with Eddy Dissipation Concept for combustion and Discrete Ordinates (DO) model for radiation. A parametric study has been conducted to assess the effect of selected numerical and physical parameters on the simulations capability to reproduce experimental data. DO model discretization is shown to strongly affect simulations, indicating 10x10 as minimum number of angular divisions to provide a convergence. The simulations have shown sensitivity to experimental parameters such as humidity and exhaust system volumetric flow rate, highlighting the importance of accurate and extended publication of experimental data to conduct precise numerical studies. The simulations correctly reproduced the radiative heat flux from cryogenic hydrogen jet fire at different locations.
Thermal hazards from an under-expanded (900 bar) hydrogen jet fire have been numerically investigated. The simulation results have been compared with the flame length and radiative heat flux measured for the horizontal jet fire experiment conducted at INERIS. The release blowdown characteristics have been modelled using the volumetric source as an expanded implementation of the notional nozzle concept. The CFD study employs the realizable κ-ε model for turbulence and the Eddy Dissipation Concept for combustion. Radiation has been taken into account through the Discrete Ordinates (DO) model. The results demonstrated good agreement with the experimental flame length. Performance of the model shall be improved to reproduce the radiative properties dynamics during the first stage of the release (time < 10 s), whereas, during the remaining blowdown time, the simulated radiative heat flux at five sensors followed the trend observed in the experiment.
The development of computational §uid dynamics (CFD) model to simulate blast wave and ¦reball dynamics after high-pressure hydrogen tank rupture in a ¦re is described. Parametric study is performed to de¦ne the e¨ect of submodels, numerical methods, and parameters on the convergence of the simulations and reproduction of experimental data. Experiments with initial pressure in hydrogen tank of 350 and 700 bar were used to validate the model. The e¨ect of hydrogen combustion and tank opening on the blast wave strength is assessed. The simulated cases include instantaneous tank opening and half tank opening.
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