Hybrid Rocket Engine Performance Assessment Using Plume Luminosity Oscillations

Abstract

Spectral analyses were performed on high-speed video of three nitrous-oxide/paraffin-based hybrid rocket launches and one static test fire of a nitrous/paraffin-based hybrid rocket motor. The imagery was taken to assess the combustion stability and identify any dominant instability modes. A spectral analysis of the image luminosity signals has shown distinct oscillatory modes in the plume flowfield. The plume oscillations have been compared and linked to existing hybrid combustion instabilities reported in the literature and theoretical predictions. The use of high-speed imagery has proven useful as a nonintrusive method of gathering high-frequency data in the analysis of hybrid combustion during launch. Analysis of high-speed imagery from a static test has revealed the time-varying aspect of the dominant oscillatory modes. The first longitudinal acoustic mode, identified in all data sets, has been used in a novel way to determine the characteristic velocity of the operating motor.