柴油机醛类非常规污染物化学动力学机理构建

Construction of Chemical Kinetics Mechanism of Aldehydes Unregulated Pollutants from Diesel Engines

基于5种不同性质燃料燃烧机理,利用反应路径分析法对甲醛和乙醛的生成进行分析,构建包含43种组分、63步反应的醛类非常规污染物化学动力学机理(醛类机理),并对比该机理预测值与试验值.结果表明:该机理能较好地预测柴油机在较宽当量比范围内的着火延迟时间、层流火焰速度和重要组分生成,还能准确预测柴油机的甲醛和乙醛排放;适当增加柴油机的进气温度、提高进气压力、提前喷油时刻和缩短喷油持续期,可有效减少甲醛、乙醛排放,而增大EGR率会导致二者排放显著增加;对甲醛排放影响最大的因素是喷油提前角,EGR率则对乙醛的影响最大.

Based on combustion mechanisms of five fuels with different properties,the reaction path analysis method was used to analyze the generation of formaldehyde and acetaldehyde from a diesel engine.A chemical kinetics mechanism of aldehydes unregulated pollutants(aldehydes mechanism)containing 43 species and 63 reactions was constructed,and the predicted value of this mechanism was compared with the experimental value.The results show that the mechanism can not only predict the ignition delay time,the laminar flame speed and the generation of important species in a wide range of equivalence ratio,but also accurately predict the emissions of formaldehyde and acetaldehyde in the diesel engine.The emissions of formaldehyde and acetaldehyde can be effectively reduced by increasing the intake temperature and pressure,advancing the injection time,and shortening the injection duration.However,increasing exhaust gas recirculation(EGR)rate will lead to a significant increase in both emissions.Among them,the most influential factor on formaldehyde emissions is the injection advance angle,and EGR rate is the most influential factor on acetaldehyde emissions.