Abstract

Understanding and predicting the behavior of pressurized hydrogen when released into air is needed for the safe utilization of hydrogen. Analysis based on Computational Fluid Dynamics, can be used to accurately study this flow and anticipate its consequence without performing expensive experimental testing. Simulation of sudden release of highly under-expanded hydrogen jet and detecting auto-ignition is the focus of this work. The present thesis addresses ignition risks associated with the diffusion-expansion of hydrogen into ambient air, through a series of case studies, covering several types of exit geometries: fixed circular, and fixed elliptic openings, as well as expanding circular geometries, under different pressure conditions, to describe the properties that affect ignition and to determine when ignition has occurred. To be more specific this research aims at capturing all the features of the flow required, to examine where and when the probability of ignition exists, and to determine the effect of changing the opening geometry on ignition risks.