EGR废气组分比例对柴油引燃天然气发动机燃烧与排放特性的影响

Effect of the Proportion of EGR Components on Combustion and Emission Characteristics of Diesel-ignited Natural Gas Engine

为了改善柴油引燃天然气发动机的排放性能,开展废气再循环(EGR)废气组分比例对柴油引燃天然气发动机燃烧过程的影响研究。针对一款直列六缸四冲程柴油引燃天然气发动机进行台架试验,基于试验数据搭建并标定CFD仿真模型,在此基础上研究不同质量比的EGR废气组分(CO_(2)和水蒸气)对柴油引燃天然气发动机燃烧与排放特性的影响。结果表明,引入CO_(2)和水蒸气后缸内压力和温度均出现明显下降,EGR废气组分中水蒸气质量分数越高,缸内压力和温度越低。总体来说,CO_(2)和水蒸气对发动机排放特性的影响明显大于对燃烧特性的影响。当引入EGR废气组分全部为水蒸气时,缸内氮氧化物(NO_(x))排放最低(920×10^(-6))。当CO_(2)和水蒸气质量分数相同时,CO排放相较于初始状态下降11%。

In order to improve the emission performance of diesel-ignited natural gas engines,the effect of exhaust gas recirculation(EGR)component ratios on the combustion process of diesel-ignited natural gas engines was investigated.A bench test was conducted on an inline six-cylinder four-stroke dieselignited natural gas engine.Based on the test data,a CFD simulation model was constructed and calibrated to investigate the effects of different mass ratios of EGR components(CO_(2)and water vapor)on the combustion and emission characteristics of the diesel-ignited natural gas engine.The results show that both the in-cylinder pressure and temperature decrease after the introduction of CO_(2)and water vapor significantly.Especially as the mass ratio of water vapor in the EGR components increases,the incylinder pressure and temperature decrease.Overall,the effect of CO_(2)and water vapor on engine emissions is significantly greater than on combustion characteristics.NOx emissions are lowest(920×10^(-6))when all the introduced EGR components are water vapor.When the mass fractions of CO_(2)and water vapor are the same,carbon monoxide(CO)emissions are reduced by 11%compared to the initial state.