EGR率对农用单缸柴油机燃用生物柴油的NOx与PM排放特性影响分析

单缸柴油机作为小型农用机械不可或缺的动力源，在使用过程中会产生大量污染物.其中氮氧化合物（NO_x）和颗粒（PM）是气溶胶的主要组成部分，对大气环境造成了严重污染.为有效改善农用单缸柴油机NO_x和PM排放，本研究通过添加生物柴油对柴油进行改质以及采用机内EGR净化技术两种方案，测量了柴油机分别燃用柴油B0，生物柴油调合燃料B20、B50在不同EGR率下的NO_x和PM排放.结果表明，采用EGR技术能够明显改善柴油机的NO_x排放，但同时会引起碳烟排放的增加.通过在柴油中添加生物柴油能够在一定程度上降低碳烟排放，其中高负荷、大EGR率条件下的改善最为明显.在2000 r·min^-1、75%负荷，EGR率为30%时，燃用B50的碳烟排放与燃用B0相比降低了47.3%.总体上柴油中添加生物柴油与EGR技术共同作用能够有效降低柴油机高负荷工况时的颗粒排放总数量.

Effect of EGR rate on NOx and PM emission characteristics of agricultural single cylinder diesel engine fueled with Biodiesel

Various pollutants are caused by the single cylinder diesel engine which is an indispensable power for small agricultural machinery. Among these pollutants, nitrogen oxides (NO_x) and particulate matters (PM) are the main components of aerosols which have a strong effect on air pollution. In order to make the better NO_x and PM emissions of agricultural single cylinder diesel engine, the emission of NO_x and PM from diesel engine fueled with B0, B20 and B50 at different EGR rates were studied by means of fuel upgrading and internal purification technology. The results show that the utilization of the EGR technology can obviously reduce the NO_x emission of diesel engine, but the soot emission is increased. The soot emission can be reduced by adding biodiesel into the diesel engine, the best case appears under the condition of high load and large EGR rate. The soot emission of B50 is 47.3% lower than that of B0 in the case of 2000 r·min^-1, 75% load and 30% EGR rate. The combined effects of biodiesel and EGR technology can effectively reduce the total number of particles in the high load condition of diesel engine.