Atomization improvement of high-speed liquid jet with wall impingement and its utilization

本研究的目的是阐明液体雾化的高速液体射流的壁面碰撞的可能的改善效果。结果表明，在高速液体射流中形成液膜对提高液体雾化效果有显著作用。与逃逸射流相比，在这种壁面撞击雾化中，甚至喷嘴直径也可以是控制平均液滴直径的参数，因为随着喷嘴直径的增加，平均直径稍微变小。在液体射流的壁撞击技术中获得的最小平均直径为17 μ m。随着喷射压力的降低，利用壁面碰撞的效益增加。在本研究中测试的最低值0.5Mpa的液体喷射压力下，平均直径达到45 μ m，而自由射流的平均直径为700 μ m。这意味着对于壁冲击液体射流，雾化改善效果可以是1/16。在 ...更多信息 在本研究的初始阶段，预期微喷嘴阵列和压电元件的应用的组合效果。在喷气发动机燃油雾化器的应用中，采用大流量液体泵，建立了更接近于真实的喷气发动机的实验结果。激光光散射技术也被应用到评估的空间喷雾分布与横截面喷雾成像。结果表明，平均直径不依赖于空气速度，但几乎线性地减少与液体注射速度的增加。获得的最小平均直径达到17 μ m。喷雾的平均浓度随空气和液体的质量流量几乎呈线性变化。从而成功地评价了喷雾的空间分布，并为进入燃烧阶段提供了雾化行为和有用的建议。此外，由于需要测量更小的液滴尺寸，开发了利用专门设计的探针和数字显微镜的液氮冷冻方法。少

The purpose of the present study is to clarify the possible improvement effect of liquid atomization of wall impingement of a high-speed liquid jet. It was revealed that farming a liquid film with wall impingement has a great effect of improvement of liquid atomization in a high-speed liquid jet. In contrast to a flee jet, in such wall impingement atomization, even the nozzle diameter can be a parameter to control the mean droplet diameter, since with the increase in the nozzle diameter the mean diameter is slightly deed. The minimum mean diameter obtained in the technique of wall impingement of a liquid jet was 17 um. The benefit to utilize the wall impingement was increased with the decrease of the injection pressure. At the liquid injection pressure of 0.5 Mpa which was the lowest value tested in the present study, the mean diameter goes to 45 um while that for free jet was 700 um. This means that the atomization improvement effect can be 1/16 for the wall impingement liquid jet. In … More the initial stage of the present study, a combined effect with the application of a micro-nozzle array and a piezo-electric element were expected. However it was shown that they do not have any favorable effect of the improvement of liquid atomization.In the application to a fuel atomizer in jet engines, more realistic experimental rendition close to a real jet engine was established by applying a large capacity of liquid pump. A laser light scattering technique was also applied to evaluate the spatial spray distribution with the cross-sectional spray imaging. Results showed that the mean diameter does not depend on the air velocity but decreases almost linearly with the increase in the liquid injection velocity. The minimum mean diameter obtained goes to 17 um. The average concentration of spray varies almost linearly with the mass flow rates of air and the liquid. Thus the spatial distribution of the spray was also successfully evaluated as well as the atomization behavior and useful suggestion could be obtained in proceeding to the stage of combustion. Furthermore due to the needs to measure smaller droplet size a liquid nitrogen freezing method was developed utilizing a specially designed probe and a digital microscope. Less