针阀运动和油压波动对燃油喷雾特性的影响

Influence of dynamic change of needle and hydraulic pressure in diesel injection nozzle on fuel spray characteristic

针对一多孔喷油器数值模拟研究了喷嘴内针阀运动和油压波动对燃油在孔内流动过程及孔外雾化过程的影响。研究结果表明,引入油压和针阀升程的变化后,喷雾形貌及贯穿距离和锥角等喷雾特征参数均与实验结果更为吻合;而将油压和针阀升程视作恒定时其喷雾贯穿距离在喷射前期明显偏大,喷雾锥角相对较小。故在柴油机模拟计算过程中要充分考虑喷嘴内油压波动和针阀运动等因素对燃油的孔内流动、雾化、混合、燃烧及有害物生成的影响。

The effects of dynamic fluctuations of needle movement and hydraulic pressure on flow characteristics inside the nozzle hole and atomization characteristics outside the nozzle hole for multi-hole injector were investigated by numerical simulation. Results demonstrate that the flow characteristics and atomization characteristics change significantly with respect to the actual fluctuations of hydraulic pressure and needle movement inside the nozzle. The spray morphology and spray characteristic parameters, such as penetration distance and spray angle, are more consistent with the experimental results with the introduction of dynamic fluctuations of hydraulic pressure and needle movement inside the nozzle. The penetration distance is obviously larger and the spray angle is relatively smaller at the early injection stage when the hydraulic pressure and needle movement are taken as constants. Therefore, the influences of dynamic fluctuations of needle movement and hydraulic pressure on fuel flow inside the nozzle, atomization outside the nozzle, as well as on mixing, combustion and emission generation should be fully taken into consideration in diesel engine simulation.