Analysis of Pressure Oscillation Characteristics in an Engine with a Submerged Nozzle Based on Clx Motor

As a major component of a solid rocket motor, the nozzle has an important influence on the pressure oscillation in the combustion chamber. This paper takes Clx motor with a typical backward-facing step configuration as the reference, meanwhile a submerged nozzle structure is introduced for the comparison. The large eddy simulation methodology is built to investigate vortex motion laws and pressure oscillation characteristics in the combustion chambers of Clx motor and the engine taking Clx as reference but with a submerged nozzle, respectively. The numerical computation results show that: The maximum error on the frequency of pressure oscillations in the combustion chamber of Clx motor between the computations and experiments is 4.47%, which indicates that the large eddy simulation methodology established in this paper is highly accurate and reliable; the vortex shedding frequency in both engines is close to the main frequency of pressure oscillations in the combustion chamber, which means the acoustic-vortex coupling occurs; the vortex in the cavity of the submerged nozzle interacts with the upstream vortex at the nozzle inlet. This makes both the main frequency and corresponding amplitude of the pressure oscillations at the inlet of the submerged nozzle lower than those of Clx motor with a conventional nozzle.