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Venting of deflagrations remains the most cost effective method to reduce the possible adverse effects of accidental combustion that may occur in equipment and structures housing hydrogen. The HySAFER Centre at the University of Ulster (UU) is working towards understanding the underlying physical phenomena and predicting various hydrogen combustion scenarios through a Large Eddy Simulation (LES) modelling approach. The research undertaken focused on further testing and validating the UU turbulent burning velocity (TBV) model, against different types of experimental scenarios that it had not yet been tested against. The experiments selected for analysis were performed at the FM Global 63.7m3 1arge scale explosion test chamber. These experiments consisted of the ignition of flammable hydrogen-air mixtures, initially contained within the chamber. Differing ignition locations and vent sizes were considered. Numerical simulations were conducted using the UU-TBV model. This model describes the interplay between different physical mechanisms affecting the turbulent burning rate. These mechanisms are the influence of pressure, temperature and density on the laminar burning velocity, flow turbulence, turbulence generated by the ftame front itself, preferential diffusion in stretched flames and the fractal growth of turbulent flame surface area. The initial application of this model did not reproduce all details of the experimental pressure transients described by the FM Global experiments. Following appropriate investigations it was concluded that the most likely missing contribution to the enhancement of combustion in the UU-TBV model compared to the experiments was the Rayleigh Taylor (RT) instability. Therefore the UU-TBV has been extended to include RT instability. A heat transfer model and an updated method to calculate the turbulent burning velocity was also added. Comparison of simulation results against experimental data was then undertaken showing how the inclusion of RT instability and these additions improved the UU-TBV model. Finally appropriate recommendations for future areas of researched have also been suggested.

The hydrolysis of sodium borohydride (NaBH4) over efficient metal catalysts is a promising approach to hydrogen storage. An alkali such as NaOH is often added to stabilise the system in practical applications. The concentration of the NaBH4 solution should be as high as possible to improve energy density of the system. However, the byproduct sodium metaborate (NaB02) would become saturated and precipitate from the solution when the concentration of sodium borohydride is over a limit, resulting in piping blockage and the decrease of the catalyst efficiency. The theme of this thesis was to investigate the maximum NaB~ concentration. Below the maximum concentration, the precipitation of the by-product will not occur, and above the maximum concentration, the by-product tends to precipitate from the solution. Hydrogen generation rate was then investigated up to high concentration. The maximum concentration was studied using a thermodynamic approach. The relationship between the solubility and the temperature was derived based on the equality of the chemical potential of the solute in solution and in its solid state. The solubility data of NaBH4 and NaB02 were obtained by analysing the phase diagrams of NaBH4-NaOHH20 and NaB02-NaOH-H20 respectively. The model parameters were then determined by regression of the solubility data and the temperature. Activity coefficients of NaBH4 and NaB02 were needed during the regression and these were achieved by hydration analysis of the phase diagrams. The maximum concentration of NaBH4 was obtained by taking the maximum between the water in saturated NaBH4 solution and the sum of the water in saturated NaB02 solution and the water consumed for hydrolysis. The maximum concentration ofNaBH4 is mainly determined by the solubility of NaB02. The modelling of the maximum concentration was then validated experimentally. The rate of hydrogen generation from NaBH4 hydrolysis was then investigated over carbon supported ruthenium catalyst over a wide range of concentrations. The intrinsic hydrolysis rate is zero-order to NaBH4 concentration, and has a linear relationship with the basicity of the solution (-ln[OH]). The overall kinetics was modelled by building diffusion and heat effect into the intrinsic rate expression. Experimental results agree well with model prediction.

The objective of this research was to investigate the applicability of hydrogen as a fuel for compression ignition engines. The research indicates that hydrogen is a suitable fuel for “compression ignition” (CI) engines, “fumigated diesel” (FD), “homogeneous charge compression ignition” (HCCI) and “direct injection of hydrogen” (DIH2). Peculiarities of the various modes of operation with hydrogen were investigated using a high speed commercial direct injection diesel engine, Deutz 1FL 511 with a compression ratio of 17:1, as well as a simulation model to assist with on the understanding of certain phenomena that were impossible to reproduce due to the engine and transducers physical limitations. Instrumentation with high-speed data acquisition was designed and installed to measure crankshaft speed and position, airflow rate, inlet air pressure and temperature, fuel consumption, brake power, cylinder combustion pressure, and exhaust gas temperature. The design, construction and characterization of a pulse controlled hydrogen injection system for HCCI and DIH2 was carried out and discussed. In this research, special attention was paid to characterize and identify the operating parameters that control the hydrogen combustion in a CI engine. High rates of engine cylinder pressure rise were found when using hydrogen and some form of control solution is required. Simulation and engine tests were carried out to characterize and identify new design approaches to control such high rates of pressure rise, culminating in the proposal of a pulsed injection methodology, and also the use of the Miller cycle to mitigate the observed high rates of pressure rise. A number of possible iv innovative solutions and measures, making the hydrogen engine operation reliable and safe are also presented.

Transition metal oxides have been proposed for hydrogen storage. Samples were prepared by a post template method and hydrothermal treatment. TIk morphology of the samples was investigated by BET method and by Scanning filcclron Microscopy .The composition and crystal structure was examined by X-ray Powder Diffraction and Energy Disperse X-ray analysis. In order to obtain comparable results, commercial powders were tested by the same manner. By comparing results obtained for metal oxides before and after deposition it was found that presence of Pt and Pt increased amount of gas stored by -60% (the results were corrected by amount of hydrogen chemisorbed by Pt or Pd). It was concluded thai spillover effect is responsible for additional hydrogen adsorption.

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