Hydrogen is a clean fuel for internal combustion engines as it produces only water vapor and
nitrogen oxides when it burns. In this research, hydrogen is used as a blending fuel with diesel to
reduce pollutants emission and to improve performance. It is inducted in the inlet manifold,
(continuous manifold induction), which is of a single cylinder, four stroke, direct injection, variable
compression ratio water cold diesel engine, type (Kirloskar). This technique of hydrogen blending is
selected because of its simplicity and low cost. Hydrogen blending is built on the basis of energy
replacement. A special electronic unit is designed and fabricated to control hydrogen blending ratio.
The maximum achieved ratio is 30% of input energy and beyond that the engine operation becomes
unsatisfactory. Tests are done with 17.5 compression ratio and 1500 rpm. The brake specific fuel
consumption is reduced by 29% and the engine thermal efficiency increased by 16% at these operating
conditions. The pollutant emissions of carbon oxides, UHC, and smoke opacity are dramatically
decreased by 19.5%, 13%,and 45% respectively while NOx emission increased by 10%.