燃烧参数对汽油/柴油双燃料HPCC性能和排放影响的试验

在一台改造的单缸柴油机上,转速为1,500,r/min、平均指标压力为0.9,MPa工况进行了不同参数对汽油/柴油双燃料高比例预混合低温燃烧(HPCC)方式燃烧和排放性能影响的试验研究.结果表明,调整EGR率和汽油比例可实现HPCC燃烧过程优化,在保持发动机高燃油经济性的前提下使NOx和碳烟(Soot)排放大幅降低;进气压力对Soot的影响不明显,但进气压力过低将限制汽油比例的提高,NOx排放偏高,进气压力过高使燃烧效率和热效率降低;提高柴油喷油压力,滞燃期延长,最大压升率及最大爆发压力降低;提高喷油压力可同时降低NOx和Soot排放,但喷油压力对燃烧效率、指示油耗、HC和CO排放影响不大.在HPCC燃烧中,通过优化EGR率、汽油比例、进气压力和柴油喷油压力,在不使用后处理器的前提下可使NOx和Soot排放分别低于0.4,g/(kW.h)和0.003,g/(kW.h),并保持较高的热效率,但HC和CO排放偏高,需要采用有较高转换效率的氧化后处理器加以解决.

An Experimental on the Effects of Combustion Parameters on HPCC Combustion Fuelled with Gasoline/Diesel Dual Fuel

The effects of variable parameters on HPCC(high premixed charge combustion)combustion fuelled with gasoline/diesel dual fuel are conducted in a modified single-cylinder diesel operating at engine speed 1,500,r/min and IMEP(indicated mean effective pressure)of 0.9,MPa.Results show that the HPCC combustion can be optimized by modifying the EGR ratio and gasoline ratio,resulting in ultra-low NOx and soot emissions while maintaining low fuel consumption.The boost has little effect on soot emission.However,the maximum gasoline ratio depends on boost,which limits the lowest NOxemission.With the increase of boost,combustion efficiency and thermal efficiency are decreased.With the increase of injection pressure,ignition delay is increased,while maximum rate of pressure rise and peak pressure are decreased.Injection pressure has little effects on combustion efficiency,ISFC,HC and CO emissions.However,it has strong effects on NOx and soot emissions.With the increase of injection pressure,NOx and soot emissions decrease simultaneously.NOx and soot emissions decrease by 0.4,g/(kW.h)and 0.003,g/(kW.h)respectively,while maintaining high efficiency for HPCC by optimizing the EGR ratio,gasoline ratio,boost and injection pressure in the absence of after-treatment.HC and CO emissions are still high level which can be decreased by using oxidation after-treatment with high efficiency.