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采用缸内观察和三维数值分析,对一台具有小孔径喷嘴和共轨喷油装置的小型直喷式柴油机在高速高负荷工况下排气烟度的原因及其控制方法进行了研究。结果表明,由于强涡流的作用,燃油喷束很容易被扩散,并由于强反挤流的作用会立刻被卷入到挤流区。因此,凹坑内的空气没有得到有效利用。采用加大活塞凹坑直径或降低气道涡流比来抑制活塞凹坑内的空气运动,避免了过多的燃油一空气混合气进入到挤气区,提高了整个活塞凹坑内的空气利用率,从而降低了柴油机的排气烟度。
By means of in-cylinder observation and three-dimensional numerical analysis, the reason and control method of exhaust smoke of a small direct injection diesel engine with small aperture nozzle and common rail fuel injection device under high speed and high load are studied. The results show that due to the effect of strong vortices, the fuel jet is easily diffused and immediately entrained in the squish flow area due to the strong anti-squish flow. Therefore, the air in the pit is not effectively used. By increasing the diameter of the piston pit or reducing the air passage vortex ratio to inhibit the movement of air within the piston pit to avoid excessive fuel-air mixture into the squish zone to improve the utilization of air throughout the piston pit, and thus Reduced diesel exhaust smoke.