Supercritical mixing and combustion of liquid-oxygen/kerosene Bi-swirl injectors

The mixing and combustion characteristics of liquid-oxygen/kerosene bi-swirl injectors are investigated under the supercritical conditions typical of contemporary rocket engines. The basis of the study is a large-eddy simulation technique combined with a unified treatment of real-fluid thermodynamics. The turbulence/chemistry interaction is treated using a laminar flamelet library approach. Emphasis is placed on the near-field flow and flame development downstream of the inner swirler. The flame is found to be stabilized by two counter-rotating vortices in the wake region of the liquid-oxygen post, which is covered by the kerosene-rich mixture. The width of the kerosene annulus is found to significantly affect the injector behavior. A wider annulus induces a larger spreading angle of the liquidoxygen stream, which intercepts the kerosene stream in a more efficient way. Increasing the annulus width, however, imposes a wake region in a broader zone. The resultant flame becomes relatively unstable if the flame thickness is larger than the liquid-oxygen post thickness. Variation of the kerosene annulus width has a negligible effect on the dominant frequency of the pressure fluctuation, but it changes the amplitude of fluctuation.