The impending worldwide energy crisis, most importantly the potential crisis of fossil fuels, and the ever increasing environmental impacts caused by automobiles have made it a great necessity to find a clean, regenerative energy form for the future. Hydrogen, the most abundant element in the universe, is being regarded as the most appropriate and promising energy carrier. Hydrogen engine, based on the well-developed IC engine industries, is accepted to be a practical mean to use hydrogen fuel. Focusing on the hydrogen direct injection engine, the whole process, including hydrogen injection, mixture formation, ignition and combustion, is studied and an optimized control strategy is put forward to minimize the NOx emission. Instead of the routine laboratory work, most of the work is carried out with the help of well-known CFD Code AVL FIRE. In order to ensure the simulation results to be reliable, great effort has been put on verification and validation of the Code.