Experimental and numerical investigation of pressure swirl atomizers

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2014
Sümer, Bülent
In this study, unsteady flows inside a pressure swirl atomizer are investigated using experimental and numerical techniques. High Speed Shadowgraphy Technique is used in order to visualize the flow structures inside the atomizer and the resulting spray at high temporal and spatial resolutions. The images of the air core inside the pressure swirl atomizer and the resulting spray formations are captured at four di erent water flow rates. Then, the time variation of the air core diameter at di erent axial locations of the atomizer is found using the image processing tool developed. The corresponding mean spray cone angles are similarly obtained. The analysis reveals the unsteady features of the air core and the macroscopic properties of the spray. Microscopic properties of the spray are determined using a two component Phase Doppler Particle Analyzer. Sauter mean diameter distributions of the resulting water droplets and the velocity distributions for two di erent droplet size classes are obtained as a function of flow rate through the atomizer. Unsteady, two-phase flow fields within the pressure swirl atomizer are computed using a computational fluid dynamics tool based on the volume of fluid method. Two dimensional axisymmetric swirl and three dimensional numerical simulations are performed to analyze the unsteady flows inside the atomizer. The vortex structures inside the pressure swirl atomizer and the axial variation of core diameter are investigated. As a result of the experimental and numerical studies, it is found that the air core diameter and spray cone angle are not much sensitive to the flow rate. The experimental and numerical studies show that, the low frequency oscillations observed in the velocity field are associated with the dynamics of the vortical structures within the water region, while the high frequency oscillations are associated with the dynamics of the vortical structures at the head end of the air core.

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Citation Formats
B. Sümer, “Experimental and numerical investigation of pressure swirl atomizers,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.