Experimental investigation of varying composition of HCNG on performance and combustion characteristics of a SI engine

With rapid depletion of petroleum resources, researchers are investigating alternate fuels to meet global transportation energy demand. Gaseous fuels such as compressed natural gas (CNG) and hydrogen are of special interest because of their cleaner combustion characteristics compared to liquid petroleum based fossil fuels. However both these gaseous fuels have some technical issues when they are used as stand-alone alternate fuel in conventional spark ignition (SI) engines. CNG suffers from lower energy density and narrow flammability range whereas backfiring tendency is highly pronounced in hydrogen fueled engines. Hydrogen enriched compressed natural gas (HCNG) mixtures are observed to be good alternative to these individual fuels since these mixtures do not pose the issues experienced by the constituent fuels i.e. CNG and hydrogen. In this study, experiments were conducted in a spark ignited gas engine using various compositions of HCNG mixtures having 0, 10, 20, 30, 50, 70 and 100% (v/v) hydrogen fraction. The performance and combustion characteristics of these test fuels were compared with that of baseline CNG, in order to find an optimum HCNG mixture composition for a single cylinder gas engine. Results obtained showed that 30HCNG mixture delivered superior engine performance compared to other HCNG mixtures and baseline CNG, which is in sharp contrast to 15HCNG being advocated globally.