Atomization and Sprays, Vol.28, No.7, 599-620, 2018
CRITICAL EVALUATION OF MOMENTUM FLUX RATIO RELATIVE TO A LIQUID JET IN CROSSFLOW
Injecting a liquid jet into a gaseous crossflow is a common atomization technique used in propulsion and power generation systems. This has led to a substantial number of fundamental cold flow studies analyzing the atomization characteristics and dynamics of the chosen liquid. A prevalent parameter used in many jet in crossflow works is the momentum flux ratio, q, which is formulated through the calculation of the liquid injection velocity. This work investigates various methods of calculating liquid injection velocity that are utilized in literature, their effect on the formulation of q, and the interpretation of results and conclusions. Velocity calculated through dividing mass flow rate with the geometric orifice area and through Bernoulli's principle are evaluated using an array of injector designs. Injector diameter and length-to-diameter ratio, L/d, are varied to test the generality of the interpretation of results. Basing results on q through mass flow rate divided by geometric orifice area yields discrepancies in conclusion interpretation across the different injector designs. Additionally, this method and through using Bernoulli's principle provide different interpretations which may cause disagreements in conclusions in previous works. A new liquid injection velocity calculation method is presented which provides consistent interpretations across the different injector designs. "Ideal" experimental data are utilized to identify the liquid jet diameter which produces a certain flow condition. This jet diameter yields an effective area to give an effective liquid injection velocity by dividing mass flow rate by the effective area. This method agrees qualitatively with injection velocity determination through the use of computational fluid dynamics.