A Parametric Study of Counterflow Atomization

University of Minnesota M.S.M.E. thesis.May 2021. Major: Mechanical Engineering. Advisor: Alison Hoxie. 1 computer file (PDF); viii 55 pages.Novel atomizers using counterflow gas injection have shown the potential to produce water sprays comparable to commercial air-assist internal-mixing atomizers at up to 50% energy savings, with even larger savings possible for higher viscosity liquids [22]. Furthermore, counterflow atomization was shown to produce sprays with centerline Sauter mean diameters (SMD or d32) that are weakly sensitive over two magnitudes to liquid viscosity [23]. A preliminary model was posed by Johnson and colleagues [21] relating the observed effects of annulus thickness (tN), gas molar mass, and gas-to-liquid mass ratio (GLR) on the centerline SMD produced by counterflow atomizers. In their study, the effects of injection gas molar mass were determined that, in contrast to effervescent or co-flow atomizers, gasses with lighter molar masses produce sprays of significantly smaller SMD [21] [27]. This study investigates the effects of liquid volumetric flow rate, GLR, and counterflow atomizer exit orifice diameter, D0 and annulus thickness, tN on the atomizer’s performance in terms of the resultant sprays’ centerline SMD and relative span factor (RSF). In doing so, a modified model is proposed relating flow conditions to atomizer performance leading to a further understanding of the physical mechanisms of counterflow atomization