Emission Analysis of a Small Capacity Producer Gas Engine at Higher Hydrogen Concentration and Compression Ratios

In this paper, the effect of hydrogen concentration (16–22% by volume) in producer gas-air mixtures at several engine compression ratios (11, 15 and 18:1) on emissions was analyzed and reported. The experiments were carried out using bottled producer gas, with fixed gas composition resembling close to the gas quality of an open top re-burn downdraft gasifier of IISc make. Engine was operated close to stoichiometry at a constant speed of 1500 rpm, under naturally aspirated mode. Hydrogen being a highly combustible component in a producer gas-air mixture, the dynamics of in-cylinder combustion process was expected to influence the emissions. The engine was found to operate knock free under all compression ratios and loads. The measured emission data was compared against CPCB-2016 norms in India. The comparative emission analysis reveals an increase in NO emission with increase in hydrogen concentration due to higher peak in-cylinder pressures at higher compression ratios. However, the overall emission trend was found to be in compliance with prescribed emission limits.