This dissertation describes the patterns and drop size distributions of twin sprays ejected from two swirl spray nozzles. In addition, image sensing/processing technique combined with the conventional immersion sampling method was developed for drop size measurements. The results of the present study are summarized as follows :
(1) The image sensing/processing technique for sizing an counting of spray drops reduced subjective human errors and improved efficiency in measurements. Determination of the threshold brightness level to convert original images to binary ones was the most important process in using this technique. Also introduced was a graphical presentation of the appropriate non-dimensionalized threshold brightness level as a function of the distribution parameters and the pixel length.
(2) In an individual spray, the breakup length decreased and the initial spray angle increased with the injection pressure. Thus the spray remained in a hollow shape at further downstream at the high injection pressure but the hollow space eventually disappeared due to entrainment of the ambient gas. Those agree with the general trends of swirl sprays.
(3) Interactions between the two swirl sprays were studied by examining the drop size distribution and the volumetric flux of the drops. The general flow pattern of the twin spray was identified experimentally. Main different features between the twin spray and the simply superposed result of each individual spray were the entrainment behavior of the gas and its impact on the change of drop trajectories. Collisions between drops were not significant in most cases. The location of the maximum of volumetric flux difference between the twin spray and the simply superposed result moved inwards in x-y plane and outwards in x-z plane as the spray developed in downward direction. This behavior was eminent with higher injection pressure of with narrower space between the nozzles. Area-averaged SMD's increased along the axial direction in twin sprays, similar to the cases of the single sprays (or the simply superposed result), and the overall drop size distributions were mostly unaffected by the spray interactions. Thus the informations on the drop sizes of each individual spray are directly applicable to the design of the twin spray systems.
