Stability Characterization of a High Pressure Transverse Combustor with Discretely Variable Oxidizer Post Lengths

Abstract

A two-dimensional chamber containing seven ox-centered shear coaxial injector elements was designed to generate and modulate an unsteady transverse flowfield. A single Study element was placed in the middle of this unsteady flowfield so its response can be measured using pressure measurement and high speed imagery. The initial characterization of this combustor entailed the effect of post length configurations on pressure amplitude. With all other conditions held constant, a long oxidizer post configuration was stable, and a short oxidizer post configuration was unstable. These post lengths were scaled from a comparable longitudinal combustor and have consistent stability behavior for the individual scaled post lengths. Phase lag behavior between the high frequency measurements in the oxidizer posts and the combustion chamber indicated that consistent phase lags near half of the chamber acoustic mode period between posts and local chamber regions were necessary to sustain a high amplitude unsteady flowfield, suggesting a coupling of post resonance with the chamber unsteady flowfield. a