深度废气再循环对二甲醚发动机性能及排放的影响

在一台两缸二甲醚发动机上开展了不同废气再循环(EGR)率下发动机的性能和排放特性研究,测量了不同工况下发动机的油耗,HC、CO和NO_x的排放.研究表明:二甲醚发动机可承受的最大EGR率接近60%,但在高负荷时,过大的EGR率会导致发动机燃油消耗率显著升高;EGR率对发动机的NO_x排放量影响很大,随着EGR率的增加,发动机的NO_x排放量大幅度下降,高负荷时下降幅度更大;EGR率增大,HC和CO排放增加,高负荷时增加的幅度更大,特别是当EGR率超过一定范围时,EGR率的增大会引起HC和CO排放的急剧增加;低负荷时,最佳EGR率应保持在30%左右,而高负荷时,应采用较小的EGR率.

Influences of Ultra-High Exhaust Gas Recirculation on Performance and Emission Characteristics of a Dimethyl Ether Engine

To study the influences of the exhaust gas recirculation(EGR)rate on the emissions and performance of dimethyl ether (DME) engines, an experimental investigation was conducted on a 2-cylinder DME engine with EGR. Under the various operating conditions, the fuel consumption and emissions of HC, CO, and NO_x were measured. The results show that the maximum EGR rate of the DME engine can reach 60% approximately, however, under high load conditions, too large EGR rate will result in obvious deterioration in the engine brake specific fuel consumption. EGR has significant effects on NO_x emissions. NO_x emissions decrease clearly with the increase in the EGR rate, especially under high load conditions. HC and CO emissions increase with the in-crease in the EGR rate, particularly under high load conditions. When the EGR rate is over a cer-tain value, the increase of the EGR rate will lead to a quick increase in HC and CO emissions. It is suggested that the optimal EGR rate should be near 30% under low load conditions while the engine should run with low EGR rates under high load conditions.