Development of a momentum driven planar two-phase countercurrent shear layer facility using PIV

Abstract

Atomization has widespread industrial applications, where small inefficiencies quickly lead to significant energy costs. These elevated costs have led to higher efficiency atomization techniques being explored by several research teams. Focusing on high viscosity liquids, conventional atomizers have struggled to maintain high levels of efficiency until a University of Minnesota team developed a nozzle capable of producing remarkably small Sauter mean diameters of less than 50 microns at air to liquid ratios ranging from 0.1 to 0.5. The team suggests that the formation of small shear layers between the liquid and air streams creates short wavelength interfacial instabilities, the mechanism for breaking up the liquid. The work here aimed to further explore this mechanism by building an experimental facility which tested the dynamics and spatiotemporal evolution of interfacial instabilities of a momentum driven planar two-phase countercurrent mixing layer. Air-water two-phase countercurrent shear layers were set up, where the movement of the primary jet allows the spatial development of the shear layer to be studied. Particle Image Velocimetry (PIV) was employed using a Quantel EverGreen Nd-YAG 532 nm laser to illuminate polyamide particles suspended in the primary stream and a TSI 29 MP PowerView high speed camera to record the interactions between the primary and secondary streams. Three different secondary flow rates were observed to explore different flow characteristics.