中文摘要：

在一台直喷压燃发动机上，开展了进气掺混CO2对二甲醚（DME）的燃烧与非常规排放物的影响的试验研究．结果表明，与纯空气进气相比，主燃烧开始时刻随CO2掺混率的增大明显后移，燃烧持续期延长，CO2掺混率为25％时的最大爆发压力降低了约1．0MPa，最大爆发压力出现的位置推迟了5°CA，缸内压力升高率降低了0．15MPa／（°CA），且压力升高率峰值的出现时间随CO2掺混率的增加而滞后．在一定的发动机转速和负荷条件下，甲醛排放随CO2掺混率的增加呈线性递增，甲酸的排放则呈线性下降，甲酸甲酯在掺混率较高或较低时排放较多，而在中等掺混率时排放较少．发动机的转速和负荷对甲醛、甲酸和甲酸甲酯的排放也具有一定的影响．

英文摘要：

An experimental study of the effects of CO2 addition in intake air on combustion and unregulated emissions was carried out with a direct inject compression ignition dimethyl ether fuelled engine. The results indicate that increasing CO2 addition rate will result in a delayed ignition timing and a prolonged main combustion duration. When CO2 addition rate reaches 25% , the peak cylinder pressure decreases by nearly 1.0 MPa and the timing of peak pressure occurrence is postponed by 5° CA. The pressure rise rate at this CO2 addition rate is then 0.15 MPa/（ ° CA） lower than that when there is no CO2 addition, and the timing of the peak rate of pressure rise is postponed as CO2 addition rate increases. For given speed and load, the emission of formaldehyde increases linearly as CO2 addition gets higher. The emission of formic acid decreases with the increase of CO2 addition. The emission of methyl formate is higher at the CO2 addition rates of 0 and 25% and lower at the rates of 10% and 15%. In conclusion, the trade-off of the emissions of three unregulated pollutants can be reached at the best CO2 addition rate of 15%. The effects of engine speed and load on unregulated emissions were also investigated.