Self-Ignition of Hydrogen Released under High Pressure through Two Slits

In this paper the investigation of hydrogen release through two slits into air by means of numerical modelling in two-dimensional setup is carried out. Initial hydrogen pressure is varied in the range from 350 to 700 atm that corresponds to the conditions of hydrogen storage in high-pressure vessels. Besides, two main parameters that describe geometric configuration, the width of slits and the distance between them, are varied. Two modes of hydrogen release are possible at different values of the listed parameters: with and without hydrogen self-ignition. It is shown that the gas heating in the region of interference of two shock waves plays the key role in the process of self-ignition during hydrogen release through two slits. The types of ignition kernels formed with the variation in the main parameters are presented. The diagrams of hydrogen release modes are obtained in a wide range of the width of slits and the distance between slits. The regions of parameters are found in those diagrams in which the self-ignition takes place. In particular, it is shown that hydrogen self-ignites only when the slits are located relatively close to each other. With the increase in the width of slit this criterion weakens and starting from the certain width of slit hydrogen could self-ignite in the absence of the flow through the second slit. The obtained results could be interesting for the development of safe hydrogen storage systems as well as systems in which the combustion initiation takes place without the use of additional ignition devices.