For a long time hydrogen has been known as a good alternative fuel for its unique and highly desirable properties, for performing as a fuel in an engine (King and Rand, 1955). There are many features that make hydrogen fuel very convenient and attractive like long-term renewability, less pollution, non toxic, and the only thing it produces after combustion is water as shown in the equation below (Fulton et al., 1993).
H2 can be commercially produced by electrolyses of water and by coal gasification, and it is only one out of many other resources that can be derived from natural resources such as coal, uranium and oil shale or from renewable resources depending on solar energy. It can also be produced by several other methods such as solar photo-electrolysis and thermo-chemical decomposition of water, although these are currently still in the laboratory stage (Saravanan and Nagarajan, 2008).
Lately researches have been focusing on using hydrogen as an alternative fuel in internal combustion engines in the hybrid system vehicles. In (SI) engines hydrogen can be used on its own as a sole fuel by injection or carburetion, but in (CI) engine, however, H2 cannot be used as a sole fuel due to its higher self ignition temperature, but it can be used in the dual fuel mode.
Hydrogen has been used as a fuel in ICEs, fuel cells and as an additive to conventional fuels such as diesel fuel, gasoline, methane, etc. Using hydrogen as an additive offers us to enhance the mixture by taking the advantages from both fuels. The properties of hydrogen along with those of diesel fuel and gasoline are listed for comparison in the Table (D’Andrea et al., 2004).
Hydrogen has a flame speed that is five times higher than any other hydrocarbon fuel listed here, Also, it has a lean limit (mixture at which flame will not propagate due to excess air) of Φ=0.1 where Φ(equivalence ratio), is defined as the ratio of the actual fuel/air mass ratio to the stoichiometric fuel/air mass ratio, much lower than the theoretical limit of gasoline (Φ=0.6). Theoretically, it is applicable to extend the lean limit of the mixture, by adding a small amount of hydrogen to a gaseous or liquid HC fuel. Operating with abundant excess air ensures to...