EGR thermal and chemical effects on combustion and emission of diesel/natural gas dual-fuel engine

Abstract In this paper, by coupling a D19 diesel engine three-dimensional and one-dimensional models with a diesel/NG dual-fuel chemical dynamics mechanism, respectively, the thermal and chemical effects of the EGR major components (CO2 and H2O) on in-cylinder combustion and emissions were studied. The results show that the EGR combined effect is the sum of the thermal and chemical effect, and the thermal effect is greater than the chemical effect. In the EGR major components, the CO2 thermal effect is greater than that H2O, and the chemical effect is smaller than that H2O. At the 50% EGR rate, CO2 and H2O thermal and chemical effects accounted for 65.3% and 36.7% of the combined effects in diesel mode, respectively. At the 50% EGR rate, the thermal and chemical effects of CO2 and H2O accounted for 62.2% and 39.2% of the combined effects in dual-fuel mode, respectively. The effects of CO2 and H2O can be superimposed with each other. CO2 and H2O have a greater influence in dual-fuel mode, that is, the dual-fuel is more sensitive to EGR.