Numerical Simulation of the Flow Characteristics Within a Pressure-Swirling Atomizer

Abstract

The internal flow within a pressure swirl atomizer was numerically simulated and evaluated in the present investigation. To validate the numerical method, a large-scale atomizer with an orifice diameter 21mm has been simulated and compared with former experimental results in the literature. Then a production-scale atomizer with an orifice diameter 1mm was simulated and compared to the results of large-scale atomizer. The internal flow characteristics of the swirl chamber were evaluated mainly in terms of the film thickness at the exit of the orifice, the cone angle of the spray and the discharge coefficient of the nozzle. It was found that the numerical results of the large-scale atomizer with turbulent Reynolds Stress model yield more accurate solutions than the results with laminar flow model, which indicated that a turbulence flow has been formed within the large scale atomizer. Nevertheless, when the turbulent model was applied to a production-scale atomizer tested by Lacava (2004), its numerical results did not fit well with the experimental data any more. It was found that the Reynolds number of the flow in production-scale atomizer is about 2000, which is one order of magnitude lower than the Reynold’s number in the large-scale atomizer. As such a laminar flow model was successfully applied to its internal flow simulation and it is shown that the numerical results of the production-scale atomizer with laminar model yield more accurate solutions than the results with turbulent flow model. Finally, the effects of orifice contraction angle and mass flow rate were investigated in the production-scale pressure swirl atomizer using the laminar model. The numerical results showed that the discharge coefficient keeps almost constant with increasing orifice contraction angle, and the discharge coefficient, the film thickness at exit and the spray cone angle also almost keep constant with increasing the mass flow rate.