Mixing Enhancement of Liquid Rocket Engine Injector Flow

Abstract

An investigation of the mixing enhancement behavior of N2 shear coaxial jets between two injector geometries is presented. A total of 20 cases with one injector geometry and 15 with the other, corresponding to different momentum flux ratios (J values) at subcritical, nearcritical and supercritical pressures are analyzed and compared. The measurements are extracted from 998 backlit images for each data point. Acoustic excitation is used to analyze the response of the system to velocity and pressure perturbations. The frequency of the system varied from 2.90 to 3.11 kHz and the maximum peak-to-peak pressure perturbation as a percentage of the mean chamber pressure was 4%. It was found that the geometry differences between the two injectors had a large impact on their behavior. The qualitative response of one of the injectors to acoustics at low J values in the subcritical regime was completely different to the other. In contrast, when comparing cases with very similar J values for different pressures, it was found that the normalized dark core length between these cases remains close regardless of phase angle for the two injectors despite the fact that the relative acoustic excitation intensities for subcritical pressures were up to eight times stronger than those at near and supercritical chamber pressures.