过量空气系数对柴油引燃高压直喷式天然气发动机的影响

Effect of Excess Air Coefficient on Diesel Ignition of High Pressure Direct Injection Natural Gas Engine

为了探究过量空气系数对天然气发动机燃烧和排放的影响,基于Cummins ISX天然气发动机建立了柴油引燃天然气的发动机模型,利用CONVERGE软件对燃烧过程和排放进行分析。结果表明:在转速为1 200 r/m时,随着过量空气系数从1.5增加到3.5,燃烧的缸内平均压力峰值增加,缸内平均温度明显下降,天然气燃烧逐渐趋于稳定,主要燃烧区域逐渐减小,soot排放下降了74%;NO_x排放随过量空气系数的增加呈现出先增加后下降的趋势;当过量系数空气为3.5时,NO_x排放最低;通过增加过量空气系数可以改善直喷式天然气发动机的燃烧和排放。

In order to explore the influence of excess air coefficient on the combustion and emission of natural gas engine,a diesel-ignited natural gas engine model was established based on Cummins ISX natural gas engine,and the combustion process and emission were analyzed by CONVERGE software. The results show that with the increase of excess air coefficient from 1.5 to 3.5 at 1 200 r/m,the peak value of average pressure in cylinder increases,the average temperature in cylinder decreases obviously,the combustion of natural gas tends to stabilize gradually,the main combustion area decreases gradually,the soot emission decreases by 74% and the NOx emission increases first and then decreases with the increase of excess air coefficient. When the excess coefficient air is 3.5,the emission of NOx is the lowest,and the combustion and emission of direct injection natural gas engine can be improved by increasing the excess coefficient of air.