Performance of Two-Fluid Atomization of Gel Propellant

Abstract

Two-fluid atomization of highly viscous and shear thinning non-Newtonian fluids must overcome the viscous resistance. Conventional air-blast atomizers address this requirement by operating at higher gas–liquid mass ratios (GLRs) at the cost of deteriorated efficiency. In this investigation, the atomization efficiency ηatom of a two-fluid atomizer is characterized. Fluidic design of the atomizer reduces the viscosity-induced dampening of disruptive inertia force and speeds up the breakup by providing kinetic energy of strategically positioned microjets of air. Three fluids of different viscosities and surface tensions were tested to examine the effects of properties on atomization efficiency. The presence of droplets and ligaments near the exit plane of the atomizer revealed that the atomizer enables prompt breakup of fluids without appreciable delay by viscosity. Consequently, it could break up complex non-Newtonian Jet A1 gel propellant with efficiency in the range of 0.015–0.1. Moreover, it is also capable of atomizing Newtonian fluids like water (high surface tension) with efficiency of 0.06–0.1 and Jet A1 (low surface tension) with efficiency of 0.02–0.08. Note that ηatom varied as GLRb (b −0.73 to −0.77) for the liquids tested in this work. The results of this investigation show that the deterioration in the performance of internally impinging atomizers at higher air and liquid throughputs is not determined by the viscosity of liquid but is predominantly due to the loss in kinetic energy of the excess air. © 2021 by Manisha B. Padwal. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.