甲醇替代率对双燃料发动机燃烧及其循环变动的影响

Research on the Influence of Methanol Substitution Rates on the Combustion and Cycle Fluctuations of Dual-Fuel Engines

为研究甲醇/柴油双燃料发动机甲醇替代率对燃烧及其循环变动的影响,通过在单缸柴油机上加装进气道甲醇喷射系统,进行了不同甲醇替代率的试验研究。研究表明,随着甲醇替代率增加,缸内着火时刻推迟,放热率双峰现象逐渐消失,放热率峰值、最高燃烧压力和最大压力升高率均增加。甲醇替代率对不同工况下指示热效率的影响不同,低速工况指示热效率随甲醇替代率的增加而降低,高速高负荷工况指示热效率随甲醇替代率的增加而略有增加。不同工况下的排放影响也存在明显差异,随甲醇替代率的增加,低速低负荷工况排放变化较小,而在高速高负荷下排放变化大。甲醇替代率对燃烧循环变动影响表明,低速低负荷循环变动随甲醇替代率增加而明显增加,当替代率增加至28.7%时,峰值压力的循环变动率增加2.5%,峰值压力对应曲轴转角分布也更加分散。

In order to study the effects of different blending ratios of methanol/diesel dual-fuel engines on combustion and cycle fluctuations,experiments with different methanol substitution rates were conducted on a single-cylinder engine modified with a methanol injection system.The results show that with the increase of methanol substation rate,the ignition time in the cylinder is delayed,and the bimodal phenomenon of heat release rate gradually disappears.The peak heat release rate,the maximum explosion pressure,and the maximum pressure rise rate increase.The methanol substitution rate has different effects on the indicated thermal efficiency under different working conditions.The indicated thermal efficiency decreases with the increase of methanol substation rate under low speed while slightly increases under high speed and high load conditions.There are also obvious differences in the impact on emissions under different working conditions.The emission changes are small under low speed and low load conditions,while large under high speed and high load conditions.The research on the influence of methanol substitution rate on the variation of combustion cycle shows that the cyclic variation increases significantly with the increase of methanol substitution rate under low speed and low load.When the methanol substitution rate increases to 28.7%,the cycle fluctuation rate increases by 2.5%,and the distribution of the peak pressure corresponding to the crank angle tends to be dispersed.