Development Of A Planar Two-Phase Countercurrent Shear Layer Facility

Abstract

Efficient atomization of viscous liquids has widespread applications in industry. Numerous research articles have focused on trying to make the atomization process more efficient and less energy consuming. While conventional atomizers have struggled with the efficiency of the atomization of highly viscous liquids, a counterflowing nozzle recently developed at the University of Minnesota have shown remarkable results in spraying liquids ranging in viscosity from 54 cP to over 1000 cP and producing sauter mean diameters of less than 50 microns at Air to Liquid Ratios ranging from 0.1 to 0.5. Upon closer investigation, it is assumed that extremely thin shear layers might be formed on liquid and air streams leading to interfacial instabilities of very short wavelength. The work here aimed at designing and building an experimental facility to test the dynamics and spatiotemporal evolution of interfacial instabilities a planar two-phase countercurrent mixing layer. The facility has the unique features of facilitating both fully closed and partially open channel experiments. The movement of the secondary jet allows to study the spatial development of the shear layer. As initial tests in this new facility, water-water single phase countercurrent shear layers were set up. High speed back illuminated camera and a mobile camera array recorded the interactions between the primary and the dye-injected secondary stream. Three different flow rates were observed which provided different flow characteristics. The secondary flow rate was varied between 3 to 12 gpm keeping the primary stream velocity constant. Qualitative analysis was performed by comparing the streamwise and spanwise flow structure development for all cases.