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

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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.