NUMERICAL INVESTIGATION OF MULTIPHASE FLOW INSIDE A PRESSURE SWIRL ATOMIZER AT THE INITIAL STAGE OF INJECTION

Pulse-mode operating atomizers are widely used in industry. This paper presents the fluid flow details and characteristics inside a pulse-mode operating pressure swirl atomizer (PSA). Transient flow simulations are performed inside a PSA for different Reynolds numbers. Generation of thin liquid film is shown as a function of time. Minimum required time to establish a full hollow cone liquid sheet is shown to decrease with the Reynolds number. However, when it is nondimensionalized by the ratio of atomizer volume over volume flow rate, it has been found that the nondimensional time for flow establishment is almost constant over the range of Reynolds numbers studied. Additionally, the time evolution of liquid film, axial velocity, tangential velocity, and pressure field inside a pressure swirl atomizer are given. It is observed that liquid film thickness decreases with Reynolds numbers while cone angle increases. Additionally, the pressure drop and discharge coefficient variation with Reynolods number are illustrated and it has been shown that the discharge coefficient is almost constant as a function of Reynolds number while pressure drop increases considerably. Furthermore, dissipation function distribution inside a pressure swirl atomizer at two locations (middle of swirl chamber and orifice section) are given. Finally, liquid sheet circumferential distribution along threedimensional flow structures and variation of angular momentum and swirl number versus time at various locations are illustrated. It has been shown that the swirl number decreases in the orifice section, monotonically; however, angular momentum variation is not monotonic and first decreases in the orifice section and then increases.