柴油机喷油器喷孔积碳对喷雾影响研究

Research on the Effect of Diesel Injector Nozzle Deposit on Spray Characteristics

在定容弹中进行了柴油机喷油器冷态喷雾特性试验,对比分析了积碳喷油器和新喷油器在不同喷射条件下的喷雾贯穿距和喷雾锥角。试验结果表明:喷油器喷孔积碳后,喷雾贯穿距和喷雾锥角减小,喷射初期差距较大,喷射后期差距缩小;喷射压力越大,喷雾贯穿距和喷雾锥角下降越明显。利用光学显微镜观察喷孔出口积碳发现,喷孔出口积碳分布在喷孔外沿,改变了原有的出口结构。利用流体体积方法,对喷孔内部流动进行数值仿真计算,分析了孔内积碳、出口积碳以及喷孔增长对喷孔内部流动的影响。计算结果表明:孔内积碳、出口积碳、喷孔增长导致喷孔内部空化效应减弱,出口质量流量、速度、湍动能下降,油束雾化质量变差,出口积碳影响作用更大。

The cold spray characteristics experiment of diesel injector is carried out in a constant volume bomb. The spray penetration distances and cone angles of carbon-deposited injector and new injector in the condition of different injections are analyzed. The results show that the spray penetration distance and cone angle of carbon-deposited injector decrease compared to those of new injector. The value gap is great at the initial stage of injection and is reduced at the late stage of injection. If the injection pressure is in- creased, spray penetration distance and cone angle would be decreased. The optical micrograph reveals that nozzle external deposit distributes along the orifice, and the original structure is changed. VOF （vol- ume of fluid） is used to numerically calculate the internal flow, and the effects of internal and external deposits and increase in nozzle length on internal flow are analyzed. The results show that the internal and external deposits and increase in nozzle length could result in weakening the cavitation effect, reducing the mass flow rate, velocity and turbulent kinetic energy, and deteriorating the atomization quality. Com- pared with internal deposit and increase in nozzle length, the external deposit has more impact on internal flOW.