| In this thesis an experimental study of the fluid dynamics of a spray created by two impinging jets is presented. Utilizing a novel two-reference-beam double-pulse holographic technique the effect of the impingement angle, liquid jet velocity, orifice diameter, and liquid properties on the atomization process was investigated.; For the low speed impingement process, measurements on the shape and size of the liquid sheet as well as the size and velocity of liquid elements around the sheet periphery were performed and tested against existing theoretical predictions. The predicted shape agreed rather well with the experiments qualitatively as well as quantitatively. The experiments clearly indicated that the liquid elements are largely non-spherical and they exhibit large size variations at the same angular location, which is not predicted by the theories based on the premise that the droplets at each angular position are monodispersed.; For the high speed impingement process, visualization of the overall spray pattern as well as measurements on the size and velocity of the droplets were performed. Theoretical predictions of the mean droplet size and the frequently used droplet size distributions were compared with the experimental results. The overall spray pattern clearly revealed the inherent wave nature in the disintegration process of this type of atomization. The structure of liquid elements near the impingement point is indicative of the mechanisms of the disintegration process. Smaller and faster droplets were generated with larger impingement angle, higher jet velocity, and smaller orifice diameter. Surface tension plays an important role in the droplet size without any noticeable effect on the spray pattern whereas viscosity affects the structure without any significant effect on the droplet size. The droplet velocities were not affected by liquid properties. The theoretical predictions for the mean droplet size provided a reasonable order-of-magnitude estimate. The superiority of the universal root-normal distribution to the Rosin-Rammler distribution was proved in the great majority of cases tested. |
