Fundamental Measurements of Multicomponent Turbulent Spray Mixing in Transcritical and Supercritical Conditions

Abstract

LOX-GH2 injection and mixing are of major importance for the thermodynamic processes taking place in a rocket engine yet detailed knowledge of high pressure behavior of injectants is still lacking. Accurate modeling of LOX in very high pressure environment is hampered by the limited available information or measurements of the behavior of turbulent mixing and spray formation in transcritical and supercritical regimes, in particular when additional species are present. The study described below is a combined theoretical-experimental program at Georgia Technological Institute (GT) and the University of Florida (UF) to evaluate liquid jet break-up and mixing under conditions ranging from sub- to trans- and supercritical regime. The purpose of this study is to complement and expand the existing database. Due to safety limitations in the laboratory environment the liquid oxygen/gaseous hydrogen (LOX-GH2) system is substituted by other liquid/gas mixing combinations under properly scaled conditions. High pressure devices are implemented at both UF and GT and different diagnostic methods are under development for application to the study jet breakup and fuel-air mixing from subcritical to supercritical conditions. A co-axial single injector setup is used in both facilities for parallel studies. The scale of the devices ensures injection conditions that capture the important physical processes encountered in a rocket engine. A new technique, simultaneous fluorescence and phosphorescence measurements of ketones, is being used at GT to study mixing characteristics of coaxial jet injectors across the range of subcritical to supercritical conditions. The method includes a new approach to characterize critical spray behavior via phosphorescence quenching by oxygen diffusion. Before quantitative measurements can be obtained with this new technique, however, it must be characterized across the range of pressures and temperatures that encompass the subcritical and transcritical regime. In parallel, an exciplex method is developed at UF to simultaneously detect both liquid and mixed phases for suitable mixtures from subcritical to supercritical conditions. The two approaches are used in a complementary fashion and are closely couple with a computational modeling study based on the LES capability developed at GT. This paper describes the status of these experimental studies.