Supercritical combustion instabilities of oxygen/kerosene mixture in a swirl coaxial injector

This study focuses on the fundamental combustion instability issues in staged combustion for liquid oxygen/kerosene rocket engines. A comprehensive and high-fidelity numerical simulation is conducted based on the Peng-Robinson real gas model. This involves combining the large eddy simulation (LES) method with the eddy-dissipation-concept (EDC) model. This study focuses on both the mixing and combustion processes within the gas-centered liquid-swirl coaxial injector and the influence of the swirl number. The results show that the numerical method can accurately predict the change of thermodynamic properties at transcritical conditions. For the injector under investigation, the dominant frequencies of near-field pressure, axial velocity, and radial velocity all coincide at 1,066 Hz. This indicates that these three parameters are coupled, but no periodic fluctuation processes are evident for tangential velocity and temperature. The time-domain pressure characteristics at monitoring points in various directions are compared and analyzed. These comparisons reveal a robust coupling relationship between pressure and axial velocity. Additionally, the numerical simulation results show that the change of the swirl number conditions at the fuel inlet has negligible effect on the evolutionary characteristics of the injector. It is confirmed that tangential velocity is not the cause of pressure fluctuations.