ID 59

Critical Evaluation of Momentum Flux Ratio Relative to Liquid Jet in Crossflow

 

Abstract:

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 injec-tion velocity. This work investigates various methods of calculating liquid injection velocity that are utilized in literature and their effect on the interpretation of results and conclusions. Velocity calculated through dividing volumetric flow rate with the geometric orifice area and through Bernoulli’s equation 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 volumetric flow rate divided by geometric orifice area yields discrepancies in the conclusion interpretation across the different injector designs. Additionally, this method and through using Bernoulli’s equation provide different interpretations which may cause disagree-ments in conclusions in previous works. A new liquid injection velocity calculation method is presented which provides consistent interpretations across the different injector designs. Injector discharge coefficient is calcu-lated for each injector and is used to approximate the liquid jet diameter at the injector exit. This jet diameter yields an effective area to give an effective liquid injection velocity by dividing volumetric flow rate by the ef-fective area. The method agrees with injection velocity determination through the use of CFD.