多次喷射下压力波动对喷嘴内流及近场喷雾影响试验研究

Experimental Research on Influence of Pressure Fluctuation on Nozzle Flow and Near Field Spray Under Multiple Injections

为研究多频压力波动与喷嘴内流的因果关系以及对近场喷雾的影响机理,采用高速显微成像技术,开展了不同共轨压力下多次喷射过程真实尺寸锥形孔喷嘴可视化试验研究。同时通过高压传感器测量,得到喷嘴入口压力波动数据。研究结果表明:主喷过程喷雾锥角呈靴型趋势,由发展期、转化期、稳定期和衰减期组成,其整体趋势受喷射压力的影响,过程中存在空化形式的转变。预喷和后喷等小油量喷射过程中,存在针阀升程波动导致的不一致性。喷嘴处压力降与循环喷油量水平呈正相关,空化形式的转变影响了压力波动频率和传播速度。其中几何诱导空化形成时,压力呈低频波动,而线空化形成时,产生高频压力波动趋势。

To study the causal relationship between the multi-frequency pressure fluctuations and the characteristics of the internal flow of nozzle,as well as the influence mechanism on the near-field spray,the high-speed microscopic imaging technology is used to carry out visualization experimental study on the real-size tapered hole nozzles during the multiple injection process under different common rail pressures.At the same time,the high-pressure sensor is used to measure the pressure fluctuation data of the nozzle inlet.The research results show that the spray cone angle shows a boot-shaped trend in the main injection process,which consists of the development period,the transformation period,the stable period and the decay period.The overall trend is affected by the injection pressure,and there is a change of cavitation form in the process.In the process of small fuel injection such as pre-injection and post-injection,there are obvious inconsistencies caused by the fluctuation of the needle valve lift.The pressure drop at the nozzle is positively correlated with the level of cycle fuel injection quantity,and the cavitation characteristics affect the frequency characteristics and propagation speed of the pressure fluctuation.When the geometrically induced cavitation forms,the pressure fluctuates at a low frequency.Whenline cavitation forms,a high frequency pressure fluctuation trend occurs.