Active Flow Control of Sprays with Synthetic Jets

Abstract

The effects of active flow control using a single synthetic jet on an air atomized solid cone spray were investigated experimentally for several spray flow rate ratios and momentum coefficients. Particle Image Velocimetry (PIV) was used to assess the effect of the synthetic jet actuation on global spray behavior, while the Shadowgraphy was used at 45 locations throughout the 3-D spray flow field to measure its microscopic characteristics in order to understand the influence of the synthetic jet on droplet size, distribution, and concentration. The synthetic jet was shown to provide vectoring of the spray up to about 18 away from the control jet with increased vectoring, spray width, and RMS for low flow rate ratio spray and high momentum coefficients. Shadowgraphy measurements indicate that for the low flow rates ratio, small droplets are pushed away and are moved across the spray, resulting in increased concentration of small droplets on the side away from the synthetic jet. For high flow rate ratios, the number of large droplets is increased along the centerline of the spray, indicating coalescence of small droplets, as they are vectored by the flow control. The feasibility of using two opposing synthetic jets for flapping motion of the spray was demonstrated, as well, indicating that synthetic jets are a potentially powerful tool for active flow control of sprays.