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扫气过程中新鲜充量的损失是点燃式二冲程汽油机油耗率和未燃 HC 排放量高的主要原因。为了减少这种损失,开发了一种选择性排气再循环(SEGR)的新方案。对排气中新鲜充量损失过程的研究表明,HC 浓度在上止点前后最大。SEGR的基本原理是,使部分排气在 HC 浓度最大时再循环。利用曲轴箱进气时的负压,就可做到这一点。SEGR 系统需要一个再循环排气取样探头,它经一个单向阀与扫气道顶端连接。新鲜充量与普通发动机充量的进气方式相同。本文除介绍方案之外,还详细讨论了空燃比、点火提前角及再循环率对汽油机性能和排放的影响。试验结果表明,与不采用 SEGR 相比,采用 SEGR 可使 HC 降低34%,同时使油耗率降低约12%。
The loss of fresh charge during scavenging is the main reason for the high fuel consumption and the unburned HC emissions of two-stroke gasoline engines. In order to reduce this loss, a new scheme of selective exhaust gas recirculation (SEGR) has been developed. Studies on the process of fresh charge loss in exhaust show that HC concentration is greatest before and after TDC. The basic principle of SEGR is to have part of the exhaust gas recirculated at the maximum HC concentration. Use crankcase intake negative pressure, you can do this. The SEGR system requires a recirculated exhaust gas sampling probe that is connected to the top of the scavenging path via a one-way valve. The fresh charge is the same as the intake mode of normal engine charge. In addition to the introduction of the program in this paper, but also discussed in detail air-fuel ratio, ignition timing and recirculation rate of gasoline engine performance and emissions. Test results show that using SEGR reduces HC by 34% and fuel consumption by about 12%, compared to not using SEGR.