Experimental Study on the Effect of Hydrogen Addition to Compressed Natural Gas (CNG) on Engine Operation and Emission Reduction

In this study, effects on a spark ignition engine of pure compressed natural gas (CNG) and mixtures of CNG and hydrogen (Hythane) have been experimentally considered. In this study, three types of fuel including pure CNG, Hythane with 15% hydrogen and Hythane with 30% hydrogen in volume are used. Tests were performed in both of full load and part load conditions. Full load tests contain engine speeds from 1500 rpmup to 6000 rpm with step of 500 rpm. Part load tests were performed in engine speed of 2000 rpm and 3000 rpm. In each test, spark timing was set to reach the maximum indicated mean effective pressure. The results showed that volumetric efficiency, power and torque decreased with increase of Hydrogen fraction at full loads but thermal efficiency increased. Increase of Hydrogen Fraction in Hythane mixture cause CO and HCdecrease but NOx increases.