柴油机喷油嘴针阀动态特性的初步研究

Preliminary Study on Dynamic Characteristic of Fuel Injector for Diesel Engine

柴油机油嘴油槽中的压力变化率可达20～40MPa/ms,因此针阀的启闭过程是一个动态过程。本文建立了针阀上升和下降过程的动态运动方程,并与静力平衡方程作了比较。理论与试验研究证明,针阀动态开启压力明显高于静态,而动态关闭压力又明显低于静态,且与发动机工况有关。针阀的动态落座特性使喷射后期油粒直径变大,喷雾质量变差,并可能危及排放指标及油嘴寿命。

The rate of pressure variation in the trough of fuel injector get up to 20～40MPa/ms, thus the process of opening and closing of needle movement and compares it with the static one. Theoretical and experimental study verifies that dynamic opening pressure is obviously higher than the static one, while dynamic closing pressure is obviously lower than the static one. It is also proved that dynamic opening pressure and closing pressure are related to opening condition. The dynamic plunging characteristics of needle result in the fuel particles in the last phase of injection. This worsens the spray quality and probably harms exhaust emission and injector life.