The effect of ignition diesel injection conditions on the combustion process of natural gas engine

Abstract

As transportation is a major contributor to carbon emissions, the significance of researching dual-fuel engines lies in their potential to substantially reduce such emissions. Based on the experimental engine of diesel micro-ignition and air intake channel injection natural gas engine, the effects of pilot diesel quality, diesel injection timing and excess air coefficient on combustion process were studied. The test was performed on a single-cylinder engine modified with the WP12 natural gas engine at 1000 rpm under medium load condition. The results revealed that there is a critical pilot energy proportion that affects the combustion stability and that increasing the pilot diesel mass below the critical value improves the combustion stability. The critical diesel energy share increases as the diesel injection moment is delayed and the λ is increased. From the combustion process analysis early ignition diesel injection time is beneficial to improve the thermal efficiency, reduce THC and CO emissions, but sometimes worsen the NOx emissions. Reasonably improving the quality of pilot diesel can accelerate the combustion process and improve thermal efficiency by up to 47.7%.