Effect of Cup Length on Film Profiles in Gas-Centered Swirl-Coaxial Injectors

Abstract

Recent interest in LOX-hydrocarbon rocket engines has resulted in the need for design criteria and scaling laws for injectors which work well in such an environment. One injector type that has been shown to work well in LOX-hydrocarbon engines is a Gas-Centered Swirl-Coaxial (GCSC) Injector. While earlier work has focused on a number of the important parameters, one that has been left unexplored is the injector cup length. In this study the effect of the injector cup length on the atomizing film in GCSC injectors is explored. The length of the atomizing film is used as reference parameter for the overall spray quality. Using lasersheet illuminations along with water and nitrogen as the working fluid, film lengths were determined in six unique injector geometries and over a number of flow conditions. Each injector geometry and flow condition was tested with two injector cup lengths. Results will show that the injector cup length has little effect on the films for test conditions with momentum flux ratios greater than 400 as long as the film is completely broken up within the cup.