柴油高压喷嘴内部的压力波动与不稳定空化现象分析

Analysis on Pressure Fluctuation and Unsteady Cavitation Inside High-Pressure Diesel Injection Nozzles

利用试验测量与三维数值模拟相结合的手段对一单孔柴油高压喷嘴中的压力波动,不稳定空化现象以及二者之间的关联进行了深入地考察。分析结果显示,该喷嘴内部的压力波动会随着喷射压力的提高而变得更为剧烈,其最大频率可达到40kHz。剧烈的压力波动对喷孔空化过程的演变有着重大的影响,压力波动所对应的压力变化率的大小可以作为评价喷孔空化程度强弱的一个重要指标。另外,喷孔空化流场不同空间点上的空化气泡动力特性差异明显,空间点越靠近喷孔出口,其对应的空化气泡动力特性越不稳定,也即对压力波动越敏感。

Pressure fluctuations and unsteady cavitation within a single-hole diesel injection nozzle, together with combination between these two phenomena, were investigated thoroughly through experimental measurements and three-dimensional numerical modeling. Analysis results indicate that pressure in the diesel injection nozzle fluctuates more dramatically as the magnitude of injection pressure increases and maximum frequency of fluctuation even reaches 40 kHz. Sharp pressure fluctuations have a significant impact on the evolution of cavitation process in nozzle hole, and rate of pressure change derived from pressure fluctuation can be regarded as an important index to evaluate the cavitation degree inside diesel injection nozzle holes. Moreover, dynamic behaviors of cavitation bubble at different locations of nozzle hole cavitating flow field are obviously distinct. As location closes to the outlet of nozzle hole, the corresponding dynamic behavior of cavitation bubble is more unstable and accordingly becomes more sensitive to pressure fluctuations.