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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。
Diesel engine oil tank pressure change rate of up to 20 ~ 40MPa / ms, so the valve opening and closing process is a dynamic process. In this paper, the dynamic equation of motion of needle valve rising and falling process is established and compared with the static balance equation. Theoretical and experimental studies have shown that the dynamic opening pressure of the needle valve is obviously higher than that of the static state, while the dynamic closing pressure is obviously lower than the static state, which is also related to the working condition of the engine. The dynamic seating characteristics of the needle valve increase the diameter of the late-stage pellets, deteriorate the quality of the spray, and may jeopardize emission targets and nozzle life.