喷油参数对共轨柴油机排放影响的试验研究

针对某款轻型车用柴油机的燃油系统,进行了油嘴伸出量和柴油机燃烧室的匹配选择。试验研究了在转速为1696r·min^-1,转矩为146N·m的工况下,轨压、主喷正时、预喷射参数以及EGR对NOx、烟度及燃油消耗率的影响。结果表明:在1.4mm的喷油器垫片下的油嘴伸出量,烟度最好。在试验所研究的工况点下,增大轨压可有效改善燃油雾化特性,使得烟度和燃油消耗率降低,但NOx排放增多;推迟主喷正时可有效降低NOx的排放,这两个喷油参数可作为优化柴油机性能的重要指标。通过试验可知,柴油机存在一个最佳的主预喷间隔;随着预喷油量的增加,烟度和燃油消耗率逐渐增加,NOx呈现先减少后增加的趋势;EGR阀开度的增加使NOx明显减少,但EGR阀开度在30%之后,烟度开始明显恶化。

Experimental Study on the Influence of Fuel Injection Parameters on Diesel Engine Emission

A matching between nozzle protrusion and combustion chamber of the engine was performed with a fuel injection system of a light-duty vehicle diesel engine. Series of experiment have been conducted to study the effects of rail pressure,main injection timing,pilot-injection parameters,and EGR on NOx,soot emission and fuel consumption at the operating condition of 146N·m torque and 1696r·min^-1 speed. From the results,it can be found that the smoke is preferably at the nozzle protrusion with 1.4mm injector gasket. The results from these experiments show that with larger rail pressure,the fuel atomization characteristics is improved,making soot and fuel consumption reduced,meanwhile the NOx emission is increased. The amount of NOx emission is reduced significantly with delayed main injection timing. Thus,these two fuel injection parameters can be seen as two important index to optimize the performance of the diesel engine. Additionally,there is an optimum angle between main injection and pilot injection. With the increase of fuel pilot-injection quantity,smoke and fuel consumption is increased gradually,and NOx decreased firstly and then increased. The NOx emission is significantly reduced with the increment of EGR valve opening. However,when the EGR opening is more than 30%,the smoke will deteriorate significantly.