Experimental and computational investigations of hydrogen safety, dispersion and combustion for transportation applications

Hydrogen is an energy carrier that can be produced from a variety of sources, offering one of the viable solutions to the increasing demands for clean and sustainable energy. Compared to the conventional fuels, hydrogen has distinct properties that need to be properly accounted for during its safer storage and delivery as well as more efficient and cleaner utilization. The broader objective of this study is to contribute to the scientific knowledge necessary to overcome key technical barriers to the widespread implementation of hydrogen in transportation applications. Specifically, lower flammability limit of hydrogen is first measured with an enhanced experimental setup and then supported with a theoretical analysis in order to provide safety guidelines for hazardous conditions. Small and large hydrogen releases are computationally investigated under different conditions corresponding to potential accidental release scenarios. This involves quantifying the relative roles of buoyancy, diffusion and momentum during hydrogen transient mixing in air and the associated flammable zones in a simple geometry. The numerical predictions are extended to a practical geometry in which high-pressure unsteady hydrogen leaks occur due to a catastrophic failure of a storage tank in a typical mobile hydrogen unit. Additionally, the combustion, performance and emission characteristics of a hydrogen-powered internal combustion engine are simulated by incorporating fuel-specific sub-models into a quasi-dimensional model, which is subsequently validated against independent data and utilized to quantify the effect of exhaust gas recirculation on emissions of oxides of nitrogen. Such reasonably fast and accurate predictive tools are essential to effectively design and optimize hydrogen engines for higher efficiency and near-zero emissions in the automotive industry.