Study On Atomization Characteristics Of Swirl Nozzle

Swirl nozzle is one of the effective ways to realize the atomization of liquid.Compared with the direct injection nozzle, it has attracted more and more attention because of its simple structure, low power consumption and good low-pressure, and has gradually been applied in the control of mine dust. But due to the complexity of the atomization process, there are no systematic understanding of the atomization properties of swirl nozzle, and spray pressure and the diameter of nozzle does not reasonably matching, which has become the bottleneck of the efficient settlement of dust. In view of the above problems, by using the combined method of theoretical analysis, numerical simulation and experimental test, the atomization characteristics of swirl nozzle has been systematically studied, and the spray pressure and the nozzle diameter were reasonably matched in this paper.Based on the maximum flow principle and momentum equation method,combined with angular momentum conservation equation, Bernoulli equation and continuity equation, the volume flow rate, tangential velocity distribution and pressure distribution of the inner flow field of the swirl nozzle were studied,and the corresponding distribution expressions were derived.Three dimensional modeling and mesh generation of the swirl nozzle were carried out by using FLUENT software. And the inner flow field of the swirl nozzle with different diameters and different spray pressure were simulated based on the RNG model and VOF method.From the simulation results, in the quasi solid rotational region, the tangential velocity of liquid increases linearlyfrom 0 m/s; in the potential flow region, the tangential velocity of liquid decreases inversely, near the inner wall of the nozzle is linearly reduced to 0 m/s.The maximum pressure appears at the inner wall of the nozzle, and the minimum pressure appears at the center of the nozzle. The more closer it approaches the center, the more smaller the pressure was, and amplitude decreases more significantly. Along the nozzle axis, the structure change of the swirl chamber to the tapered section will not cause significant liquid pressure loss, but the tangential velocity will decrease. In tapered section,the tangential velocity of liquid increases gradually, and the pressure decreases gradually. The tangential velocity and pressure of the liquid are significantly reduced due to the sharp change of the structure of the nozzle. When the nozzle aperture is 1.0mm and the spray pressure is 5MPa, the spraying effect is the best.Using HX-6 high speed camera and DP-02 laser particle size analyzer, the spray experiment system was built to study the atomization characteristics of swirl nozzle. The results show that, the Sauter Mean Diameter(SMD) increases firstly and then decreases with the increase of the spray distance, and finally tends to be stable after 100 cm. The SMD is biggest in the center, and it decreases gradually outward along the radial direction. Near the nozzle, the SMD distribution is more concentrated. Not only the increased of spray pressure,distance from the nozzle and distance from the center but also the decrease of nozzle diameter can make the SMD distribution more concentrated and uniform.When the nozzle aperture is 1.0mm and the spray pressure is 5MPa, the spraying effect is the best. And the area outside the nozzle 1m is more finer and uniform,which has better effect of atomization and dust reduction.