Improved Spray Model for Viscous Annular Sheets in a Swirl Injector

摘要

A modified sheet breakup model was applied to a thin, viscous liquid film generated by a swirl injector similar tonthat installed in a liquid propellant rocket engine combustor. The sheet breakup model consists of three steps:ndetermination of the swirl injector characteristics for the prediction of initial sheet conditions at the injector exit asninput, linear stability analysis for primary sheet breakup, and the Taylor analogy breakup model for final dropnformation. Under atmospheric pressure, the liquid sheet breakup occurs under a long-wave regime, sometimesnaccording to simple theoretical analysis. But in high ambient pressure conditions, like a liquid propellant rocketnengine combustor, the sheet breakup regime changes from a long wave to a short-wave regime due to a high gasnWeber number (We2 > 27=16), although the same injector was used. The sheet breakup model was, therefore,nmodified to be applicable to both long- and short-wave regimes and validated by the comparison of breakup lengthnand Sauter mean diameter to experimental results. In both experimental and computational results, the spray conenangle and breakup length decreased as the ambient pressure increased, even though the pressure difference of theninjector was constant. Local Sauter mean diameters, predicted by computation, were smaller at high ambientnpressures. The comparative results show that the computational model is able to accurately predict sheet breakupnlength, spray cone angle, local Sauter mean diameter, and overall spray shape. Therefore, the model can be used as andesign tool, ahead of analyzing spray characteristics of an injector in both atmospheric and high ambient pressurenconditions.