对置活塞二冲程柴油机换气子阶段完成比例研究

Research on Completion Ratios of Scavenging in Scavenging Sub-phases of Opposed-piston Two-stroke Diesel Engine

针对对置活塞二冲程柴油机自由排气、扫气和后充气3个换气子阶段,开展不同换气子阶段对换气过程影响研究,了解不同换气子阶段在整个换气过程中的完成比例。以某对置活塞二冲程柴油机为研究对象,在建立一维仿真模型并验证其准确性的基础上,通过缸内二氧化碳质量的变化研究了该柴油机3个换气阶段在整个换气过程中的完成比例。通过改变转速、压差和排气背压研究了这3种影响因素对不同换气阶段的影响。结果表明:该柴油机在发动机转速1 200 r/min、压差0.013 MPa、背压0.18 MPa时,自由排气、扫气和后充气3个阶段在换气过程中的完成比例分别为64.42%、35.57%和0.01%;自由排气完成比例随着转速的增加而逐渐下降,扫气阶段完成比例逐渐增加;进排气压差的影响效果与转速相似;排气背压的改变对不同换气阶段完成比例的影响不明显,只对换气过程中缸内二氧化碳的质量变化影响较大。

The influences of the free exhaust,discharge and additional scavenging phases of opposed-piston two-stroke（ OP2 S） diesel engine on the scavenging process are studied. To understand the completion of different scavenging phases in the whole scavenging process is very significant in investigating the OP2 S＇s scavenging process and the influences of scavenging parameters on scavenging process. A 1-D simulation model is established for an OP2 S diesel engine,and the accuracy of the proposed model is validated. The completed proportions of different scavenging phases in whole scavenging process are studied from the quality change of carbon dioxide in cylinder. The results illustrate that the completed proportions of free exhaust,discharge and additional scavenging phases are 64. 42%,35. 57% and 0. 01%,respectively,under the simulation conditions of 1200 r/min,0. 013 MPa pressure difference and 0. 18 MPa back exhaust pressure. If the engine speed increases,the free exhaust period decreases and the discharge period increases. The influencing effect of scavenging difference is similar with that of engine speed. The influence of exhaust pressure on the completed proportions of different scavenging periods is not significantbut the carbon dioxide mass in cylinder varies significantly when exhaust pressure changes.