Effects of fluid viscosity on the spray of a swirl atomizer in trigger sprayers

Swirl atomizers are widely used in both industry and daily life. This work focuses on experimental investigations of the effects of fluid viscosity on the spray development during the transient operation of a swirl atomizer in a trigger sprayer. In the experiments, water-glycerol mixtures were used to simulate different fluids with a wide range of viscosities. The transient dispensing piston displacement was measured by using a linear sensor fixed together with the piston. The trigger sprayer was controlled by an actuator with a given dispensing motion curve. A high-speed digital camera was used to visualize the near-nozzle spray structure. The digital images of the sprays were further processed to analyze the spatial and temporal surface waves on the spray cone. From the experimental results, it is seen that the fluid viscosity plays a very important role in controlling the fluid breakup and atomization. The spray cone angle changes with the variation of the fluid viscosity. Different from the results of constant pressure swirl atomizers, the transient operation of a swirl atomizer results in significant variation of spray structure during the liquid dispensing process. Early stage spray develops very rapidly with a fully developed cone angle. During the late stage of the dispensing process the spray cone angle becomes smaller and the wave length of the surface waves on the spray cone surface becomes longer. For fluids with different viscosities, it is found that more viscous fluid leads to a smaller spray cone angle. The surface wave temporal frequency decreases with the increase of fluid viscosity.