Dispersion and Atmospheric Diffusion of High Pressurized Hydrogen Gas

Abstract

Experiments of the dispersion for the hydrogen gas from high pressure storage tank have been conducted to investigate the safety of the hydrogen station. For the small amount dispersion from pin-hole smaller than 2mm diam., hydrogen concentration could be arranged by the simple expression in which the non-dimensional distance is defined by the nozzle diameter and hydrogen density. For the large amount dispersion from the nozzle larger than 5mm diam., the unsteady numerical simulation was conducted, because the discharged hydrogen from high-pressure tank makes the supersonic jet. The numerical calculation method which requires not so long time could be proposed, and evaluated the validity of the method by comparing the calculation results with experimental data. Furthermore, the experimentally measured dispersion rate was different from the theoretical value calculated with the assumption that the hydrogen was ideal gas and expanded isentropically. From the one-dimensional analysis including the real gas effect and numerical simulation that reproduced the shape of the nozzle, it was concluded that the real gas effect doesn’t have much effect on the decrease of the mass flow rate and it is mainly due to the pressure loss by the shape of the nozzle.