Basic Research on Wall Impinging Jet and Its Application to High Performance Spray Formation

本研究旨在弄清壁面撞击式雾化液膜的形成机理、液膜在壁面上的流动以及液膜的破碎机理，并探讨其在高性能喷雾形成中的应用。第一年采用接触式探针法测量了平板壁面上的液膜厚度。通过测量，液膜厚度在包含液体射流轴线且垂直于壁面的平面内具有最大值。随着测量点离开上平面，膜厚先减小后增大。其次，对平壁面上的液膜流动进行了理论分析。通过比较，理论分析与测量结果吻合较好。第二年，壁面上的液体膜的厚度，这是由弯曲的壁面上的液体射流的冲击形成的测量，并进行比较的情况下，在平坦的壁面上的液体冲击的测量。由实验结果可以看出，膜厚分布与平壁情况下的膜厚分布定性相似。然而，膜厚度是平壁情况下的膜厚度的两倍。这似乎是由于泰勒-戈特勒涡的产生。通过对薄膜流动的理论分析，得出本实验条件下的Gortler数福尔斯落在发生Taylor-Gortler涡的范围内。一旦发生泰勒-戈特勒涡，靠近壁面的液体失去其动量并减速。这导致液膜厚度的增加。因此，澄清了与平壁冲击的情况相比，弯曲壁冲击的情况下的喷雾特性变差。

This study aims to make clear the mechanism of the liquid film formation, liquid film flow on the wall and disintegration mechanism of a liquid film for the wall impingement type of atomization, and to investigate its application to the high performance spray formation. The fist year, the liquid film thickness on the flat wall was measured by the contact needle probe method. By the measurements, the liquid film thickness has the maximum value in the plane that includes the liquid jet axis and is perpendicular to the wall. As the measurement point departs from above plane, the film thickness decreases, and then increases. Next, the liquid film flow on the flat wall was analyzed theoretically. By the comparisons, the theoretical analysis agrees well with the measurements. The second year, the thickness of a liquid film on the wall, which was formed by the impingement of a liquid jet on the curved wall was measured, and the measurements were compared to those in the case of liquid impingement on the flat wall. By the experimental results, it was clarified that the film thickness distribution are similar qualitatively to those in the case of a flat wall. However, the film thickness was two times larger than those in the case of a flat wall. This seems to be due to Taylor-Gortler vortex generation. By theoretical analysis of the film flow, the Gortler number under the present experimental condition falls within the range that the Taylor-Gortler vortex takes place. Once the Taylor-Gortler vortex takes place, the liquid near the wall surface looses its momentum and is decelerated. This causes the increase of the liquid film thickness. Thus, it was clarified that the spray characteristics in the case of curved wall impingement get worse compared to the case of flat wall impingement.