Experimental investigation on emissions of a spark-ignition engine fuelled with hydrogen enriched natural gas

An experimental investigation on the influence of the different percent of hydrogen and excess air ratios on emissions characteristics of a spark-ignition engine fuelled with hydrogen enriched natural gas was conducted. The results show that excess air ratio has a remarkable effect on HC, NO_x, CO, and CO₂ emissions when engine is operated with a given percent of hydrogen. HC emissions decreases as increasing the percent of hydrogen at the same excess air ratio, especially under the lean-burn condition. However, NO_x emission increases and CO₂ concentration decreases as the percent of hydrogen increases. Adding hydrogen into natural gas can extend the lean burn limit of mixture. Engine combustion at lean mixture can get low emissions of HC, CO, CO₂ and NO_x.