For a long time, hydrogen has been known as a good alternative fuel due to its unique and highly desirable properties to function as a fuel in an engine (King and Rand, 1955). There are many features that make hydrogen fuel very convenient and attractive such as long-term renewability, less pollution, non-toxicity and the only thing it produces after combustion is water as shown in the equation below ( Fulton et al., 1993).H2 can be produced commercially by water electrolysis and coal gasification, and is only one of many other resources that can be derived from natural resources such as coal, uranium, and oil shale or from renewable resources that depend on solar energy. It can also be produced by several other methods such as solar photoelectrolysis and thermochemical decomposition of water, although these are currently still in the laboratory stage (Saravanan and Nagarajan, 2008). Lately, research has focused on the use of hydrogen as an alternative fuel substance in the internal combustion engines of vehicles with a hybrid system. In (SI) engines, hydrogen can be used alone as the sole fuel by injection or carburization, but in (CI) engines, however, H2 cannot be used as the sole fuel due to its higher auto-ignition temperature, but it can be used in dual power mode. Hydrogen has been used as a fuel in ICEs, fuel cells and as an additive to conventional fuels such as diesel, petrol, methane, etc. Using hydrogen as an additive allows us to improve the blend by taking the advantages of both fuels. The properties of hydrogen together with those of diesel and petrol are listed in the table for comparison (D'Andrea et al., 2004). Hydrogen has a flame speed five times higher than that of any other hydrocarbon fuel.... .. middle of paper ......itions. The coupled effect is that during ultra-lean operation, combustion temperatures remain low enough that NOx formation rates are too slow and engine emissions are almost zero (Das, 1991). The unique combustion characteristics of hydrogen that enable efficient and clean operation at low engine loads shows difficulty at high engine loads. Here, the low ignition energies of hydrogen-air mixtures cause frequent unscheduled combustion events, and the high combustion temperatures of mixtures closer to the stoichiometric composition cause an increased rate of NOx production. Both effects, in practical application, limit the power densities of hydrogen engines. The recent thrust of research and progress on this front is the development of advanced hydrogen engines with improved power densities and reduced NOx emissions at high engine loads (White et al., 2006).