Numerical modelling of release of subsonic and sonic hydrogen jets

Abstract

For the general public to use hydrogen as a vehicle fuel, they must be able to handle hydrogen with the same degree of confidence as conventional liquid and gaseous fuels. For refuelling hydrogen cars, hydrogen is stored at high pressures up to 700 bar. The hazards associated with jet releases from accidental leaks of such highly pressurized storage must be considered since a jet release and dispersion can result in a fire or explosion. Therefore, it is essential to understand the dispersion characteristics of hydrogen to determine the extent of the flammable cloud when released from a high-pressure source. These parameters are very important in the establishment of the safety distances and sizes of hazardous zones. This paper describes the work done by us in modelling of dispersion of accidental releases of hydrogen, using the FRED (Fire Explosion Release Dispersion) software. The dispersion module in FRED is validated against experimental data available in the open literature for steady release and dispersion of cold and ambient hydrogen gas. The validation is performed for a wide range of hole sizes (0.5–4 mm), pressure (1.7–400 bar) and temperature (50–298 K).The model predictions of hydrogen gas jet velocity, concentration decay as a function of distance as well as radial concentration distribution are in good agreement with experiments. Overall, it is concluded that FRED can accurately model accidental release and dispersion of hydrogen in unconfined and open configurations.