Effect of equivalence ratio on combustion and emissions of a dual-fuel natural gas engine ignited with diesel

Abstract

China is the world largest natural gas engine market, and the natural gas price has a large fluctuation range, Natural gas-diesel dual-fuel engine may be one of the options to cope with gas price fluctuations. Effect of equivalence ratio on combustion and emissions with a low compression ratio of 14.2 in a dual-fuel 6 cylinder engine was experimentally studied. Comparison between dual-fuel and spark ignition engine at stoichiometric combustion and same IMEP was conducted. Results show that the gas consumption rate decreases with the increase of equivalence ratio regardless of the strategy in nozzle parameter, exhaust gas recirculation (EGR) rate, injection parameter. Peak heat release rate and exhaust gas temperature increased, and decrease of combustion duration is obtained due to the high equivalence ratio in dual-fuel ignition mode. The gas consumption rate trend of spark ignition mode is similar to that of dual-fuel engine with the increase of equivalence ratio. Dual-fuel engine with low compression ratio of 14.2 run as spark ignition (SI) gas engine at stoichiometric ratio, but the difference lies in the combustion process. The peak heat release rate of dual-fuel engine presents higher value, while the combsution duration of dual-fuel engine is shorter, and the gas consumption rate of dual fuel engine is lower than that of SI engine.