喷射压力对甲醇缸内直喷发动机燃烧和排放特性影响的实验研究

To accurately reveal the influence mechanism of injection Parameters on engine Performance, this paper built an experimental platform for a direct-injection mcthanol engine bascd on a singlc-cylindcr diesel engine. A bench test System was uscd to invcstigate the influence of injection pressure on the power, cconomy, combustion, and emission characteristics of the direct-injection methanol engine under medium-speed and medium-load conditions. The rcsults suggest that the method of augmcnting the injection pressure plays a limited role in enhancing the heat release rate, exerting only a minor influence on the combustion Start point, combustion center of gravity, combustion end point, flamc development period, and combustion cycle. Nevertheless, it can remarkably reduce the in-cylinder Variation coefficients. Simultaneously, an increase in injection pressure can improve the uniformity and charging efficiency of the mixture, thcrcby raising the indicated mean effective pressure (IMEP) and the peak in-cylinder pressure (pm!]x) of the engine. For instance, at an intake pressure of 0. 065 MPa, whcn the mcthanol injection pressure is increased from 6 MPa to 22 MPa, the cocfficicnt of Variation of IMEP and coefficient of Variation of pnmx decreasc by 42. 7% and 37. 3%, respectively, whilc the IMEP increases by 6. 8%. Furthermore, the influence of injection pressure on emissions is intricatc. As the injection pressure rises, CO emissions decline in an approximatcly linear manncr, NO,, emissions increase substantially, the trcnds of hydrocarbon and methanol emissions vary depcnding on the intake pressure, and formaldchydc emissions cxhibit a slight increment. This study can offer a theoretical foundation and data-based guidancc for the development and optimization of practical engine control strategies.