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

本研究旨在明确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解体机理，并探讨其在高性能喷雾形成中的应用。第一年采用接触针探针法测量平壁液膜厚度。通过测量，液膜厚度在包括射流轴和垂直于壁面的平面上具有最大值。随着测点远离上述平面，膜厚先减小后增大。其次，对平壁面液膜流动进行了理论分析。通过比较，理论分析与实测结果吻合较好。第二年，测量了液体射流撞击曲面壁面形成的液膜厚度，并与液体撞击平面壁面的测量结果进行了比较。实验结果表明，膜厚分布与平壁情况下的膜厚分布在性质上是相似的。然而，薄膜厚度是平壁情况下的两倍。这似乎是由于泰勒-戈特勒涡的产生。通过对膜流的理论分析，本实验条件下的戈特勒数落在Taylor-Gortler涡发生的范围内。一旦泰勒-戈特勒漩涡发生，壁面附近的液体就会失去动量并减速。这导致液膜厚度增加。从而阐明了弯壁撞击时的喷雾特性比平壁撞击时更差。

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.