进气道喷射天然气发动机不同燃烧方式下的排放特性

Emission Characteristics of Natural Gas Engine under Different Combustion Modes

以一台加装一套天然气供给系统的DFMA15发动机为研究对象,对比燃用单一汽油和天然气发动机动力性能,研究部分负荷下过量空气系数和点火提前角对NOx和THC的影响。结果表明:在同一节气门开度下,用天然气作燃料时,发动机动力性能比汽油作为燃料时有明显下降,并随着节气门开度的增加,其动力下降指数越来越小,从28%下降至12.5%;在其他影响参数不变的情况下,混合气过浓或者过稀都会对NOx和THC的排放产生明显影响。随着过量空气系数的增大,NOx呈现先增大后减小的趋势,在λ=1.1处达到最大,THC呈现先减小后增大的趋势,在1.2处达到最小;随着点火提前角的增大,NOx呈现增大趋势,而THC呈现减小趋势并且超过25°CA后基本不受影响。

Taking the engine DFMA15 installed a natural gas supply system as the study object, compared the en-gine's dynamic performance of single fueled with gasoline and natural gas, and the effects of excess air ratio and igni-tion advance angle on NOxand THC under partial load were studied. The results showed that, in the same section ofvalve opening, when the engine uses natural gas as fuel, its dynamic performance was significantly lower than that ofgasoline as fuel, and with the increase of the section of valve opening, the power down index was getting smaller andsmaller, from 28% down to 12.5%;Too thick or thin mixture would have a significant impact on the emissions of NOxand THC, in the case of other parameters unchanged, with the increase of excess air ratio, NOxfirst increased andthen decreased, and reached the maximum atλ=1.1, but THC presented the trend of first decreasing and then increas-ing, reaching the minimum at 1.2. With the ignition advance angle increased, NOxshowed an increasing trend, whileTHC showed a decreasing trend and were basically not affected when more than 25°CA.