内/外交叉孔喷嘴内部和近场流动特性的试验

为认识内/外交叉孔喷嘴的内部空穴流动和近场喷雾特性,采用常规圆孔、外交叉孔和内交叉孔三种孔型的喷嘴在不同喷射压力、子喷孔交叉角度及出口中心距下进行了比例放大的喷嘴内部流动与喷雾近场可视化试验。试验结果表明:不同于圆形喷孔的近轴对称射流,内/外交叉孔喷嘴由于燃油的内/外部碰撞冲击作用,射流主要在与两个子喷孔中心线所处平面正交的平面(扩散面)上径向扩散,形成扇形射流。外交叉孔喷嘴喷雾扩散最为显著,其在扩散面上的液滴分散到喷嘴以下180°范围内,内交叉孔喷嘴扩散次之,两者扩散效果均远强于常规圆孔。此外,随喷射压力的提高,常规圆孔喷嘴在0.30MPa左右产生空穴,并迅速发展为水力柱塞流状态;外交叉孔喷嘴也在0.30MPa左右产生空穴,并逐渐发展至喷孔出口附近,但至1.0MPa也未出现水力柱塞流状态;内交叉孔喷嘴内始终无空穴产生。

An Experimental Study on the Internal and Near Field Flow Characteristics of Internal/External Intersecting Hole Nozzles

In order to understand the internal cavitation flow and near field spray characteristics of injector nozzles with internal/external intersecting holes, three types of nozzles, including two different intersecting hole nozzles and one conventional cylindrical hole nozzle were visualized by using high speed photography at different injections pressures, sub-hole impact angle and sub-hole center to center distance. Results show that, unlike the paraxial symmetric spray from the conventional cylindrical hole nozzle, the internal/external intersecting hole nozzle can create a fan shaped spray due to internal/external spray impingements. As observed, the spray from the external intersecting hole nozzle shows a very intensive radial diffusibility followed by that of the internal intersecting hole nozzles and both of which are more diffusible than that of conventional cylindrical hole nozzle. In addition, as the injection pressure increases, the conventional nozzle produces cavitation at 0.3 MPa, which rapidly develops into a hydraulic plunger flow, and the external intersecting hole nozzle also generates cavitation at 0.3 MPa, but no hydraulic plunger flow occurs at 0.1 MPa. While the internal intersecting hole nozzle has no cavitation at all.