Effects of hydrogen enrichment on the combustion and emission characteristics of a turbulent jet ignited medium speed natural gas engine: A numerical study

Abstract

Abstract The combination of hydrogen enrichment and pre-chamber initiated turbulent jet ignition was proposed to improve the combustion and performance of large bore gas engines. In order to clarify the effects of hydrogen enrichment level on the combustion and emission formation processes of a large bore medium-speed natural gas engine ignited by pre-chamber initiated turbulent jets, a computational fluid dynamics simulation was carried out to calculate the in-cylinder gas flow and chemical reactions, which were calculated with a detailed oxidation reaction mechanism of methane. In the study, the hydrogen volume fraction was varied from 0% to 30% with a step of 5%, and the excess air ratios of the mixture in the pre-chamber and the main chamber were maintained at 1.0 and 2.0, respectively. The numerical results show that the turbulent jets and the chemical dynamics of the hydrogen enriched fuel played a dominant role in the combustion rates at the former and the latter halves stage of the combustion process, respectively. Moreover, as the increase of hydrogen fraction, the emissions of carbon monoxide, total hydrocarbons and non-methane hydrocarbons and the indicated specific fuel consumption decrease, however, the emissions of nitrogen oxides increase.