二甲醚发动机掺烧LPG燃烧和排放特性的试验研究

在一台直喷二甲醚发动机上进行了掺烧LPG的台架试验,研究混合燃料中LPG的含量对二甲醚发动机燃烧和排放的影响。研究表明,随着混合燃料中LPG含量的增加,滞燃期延长,着火始点延后,燃烧持续期缩短,低负荷时变化更大。燃油消耗率随LPG含量增大先降低后增加,LPG含量过高或过低都会导致油耗率升高,在二甲醚中掺混30%LPG时油耗率最低,发动机经济性最佳。LPG对NO_X排放影响较为复杂,低负荷时,随LPG含量的增大,NO_X排放上升。中高负荷时,随LPG含量增大,NO_X排放先增大后减小。随着LPG含量增大,发动机HC排放略有升高,CO排放迅速增加,高负荷时CO排放增幅更大。该研究结果为LPG燃料在压燃式发动机上的应用及改善二甲醚发动机的燃油经济性提供了试验指导。

Experimental Study of Combustion and Emission characteristics of Mixed LPG on Dimethyl Ether Engine

Based on engine bench test, influences of LPG contents in blends on combustion and emission characteristics of DME engine had been investigated. The results indicated that with the increase of the LPG content in the mixed fuel, the ignition delay is prolonged, the ignition point is delayed, and the combustion duration is shortened. The change under the low load is much larger. The fuel consumption rate is increased with the LPG content. Both the excessively high and low LPG contents will lead to the increase of fuel consumption. The fuel consumption rate is lowest and the engine economy is the best when the dimethyl ether is mixed with 30%LPG. The effect of LPG on NO_X emissions is relatively complex. Under the low load, the NO_X emission is increased with the LPG content. However, as for the medium and high load, with the increase of LPG content, the NO_X emission is firstly increased and then decreased. With the increase of LPG content, the engine HC emission is increased slightly, CO emission is rapidly increased. Furthermore, the CO emission increase range is greater under high load. The research results can provide practical references for LPG application in CI engine and improving the economy of DME engine.