Analysis of Acoustic Energy Dissipation in a Rectangular Combustion Chamber with Injection of Cryogenic Propellants

Abstract

The acoustic energy dissipation in a hydrogen-oxygen combustion chamber at sub-and supercritical conditions for oxygen was investigated. The investigation was undertaken using the sub-scale combustion chamber designated ‘BKH’. The first two eigenmodes of BKH, the first longitudinal, and first tangential, were investigated. Two independent methods were applied to measure acoustic dissipation in the combustion chamber. First, a time domain measurement of the acoustic dissipation rate was made by periodically forcing combustion chamber acoustics. Secondly, the frequency response of the system to a constant amplitude forcing was used. The acoustic dissipation measurements from both methods were found to compare well. It was found that the frequency response was not always symmetric, so applicability of the asymmetric Lorentzian and Fano profiles were also investigated. It was found that the asymmetric profiles were able to accurately capture the dissipation behaviour of the damped signal. The acoustic dissipation was found to be larger for the first longitudinal mode than for the first tangential mode, in particular for operating conditions without combustion. With combustion the longitudinal dissipation remained around 700 (1/s) whereas an increase from 300 (1/s) to around 500 (1/s) was observed for the first tangential mode.