燃烧室形状对柴油机燃烧及排放的影响

Effect of Combustion Chamber on Combustion And Emission for Diesel Engines

设计了3种不同的燃烧室,压缩比降低,缩口直径及凹坑深度增加,缸内气流运动增强,有利于形成均匀的缸内混合气。并利用柴油机台架进行了两级增压柴油机燃烧室选型及其与EGR耦合试验开发,实验结果表明:低负荷工况,相对于原机,SF1,SF2,SF3滞燃期较长,但其瞬时放热速率及最高放热速率较大,燃烧持续期相对较短,有利于降低传热损失,改善比油耗。大负荷工况下,二级增压柴油机通过降低燃烧室压缩比(16.8及16.2),缸内燃烧温度降低,最大爆发压力及压力升高率降低,缸内最高压力可以控制在160bar范围内,满足柴油机强度设计要求。低速大负荷及中速小负荷工况下,SF1及SF4都能明显改善NOx与烟度和BFSC之间的trade-off关系。综合几个工况的排放和燃油经济性,SF1综合性能最好。

Three kinds of combustion chamber shapes were optimized and designed to reduce the compression ratio(CR),increase the diameter of the orifice,increase the depth of the pit and enhance the flow in the cylinder,which is conducive to forming a more uniform mixture gas in the cylinder.and the combustion chamber selection testing of two-stage supercharged diesel engine is carried out coupling with EGR.The experimental results show that:Under low load condition,compared with the original engine,SF1,SF2 and SF3 have a longer ignition delay,but their instantaneous heat release rate and maximum heat release rate are higher,and their combustion duration is relatively short,CA50 is closer to TDC,so that heat transfer loss is lower,which can improve brake specific fuel consumption(BSFC).High load conditions,the combustion temperature,maximum explosion pressure and pressure rise rate of the two-stage supercharged diesel engine can be reduced by reducing the combustion chamber compression ratio(16.8 and 16.2),and the maximum pressure in the cylinder can be controlled within the range of 160 bar to meet the diesel engine strength design requirements.Low speed high load and middle speed low-load conditions,SF1 and SF4 can significantly improve the trade-off relationship between NOx,smoke and BFS.Considering the emission and fuel economy of several operating conditions,SF1 has the best overall performance.