| Abstract:For a natural gas engine operating in a stoichiometric combustion mode, the effect of exhaust gas recirculation (EGR) and ignition timing on combustion process and exhaust temperature was studied using a combination of three-dimensional combustion analysis and one-dimensional thermodynamic calculation. Results show that increasing the EGR retards combustion phase, prolongs combustion duration, decreases peak heat release rate, and reduces maximum combustion pressure increase rate, resulting in a decrease in maximum combustion pressure and highest average combustion temperature in the cylinder , and finally the dilution and heat capacity effects of EGR inhibit the increase of the combustion rate of the mixture. In contrast to this, advancing the ignition timing leads to advanced angle of 50% mass fraction burned (CA50), shortened combustion duration, and an increase in the maximum pressure increase rate, maximum combustion pressure and peak heat release rate. Moreover, the exhaust temperature decreases with increased EGR and advanced ignition timing. During the engine test, under the condition of keeping the intake of air and gas unchanged, increasing the EGR to 23%, and advancing the ignition timing to -18° in crank angle can increase the rated power of the original engine by 7.4kW, and reduce the fuel consumption by 4g/(kW·h). But If the intake of air and gas is increased by 11.6%, when the EGR is greater than 19%, and the ignition timing is earlier than -10.5°in crank angle, the rated power can be increased by 36kW, while the exhaust temperature is still below 760℃. |