Numerical Investigation of Transcritical Mixing Dynamics of Bi-shear Injectors

A numerical study has been performed to evaluate the cryogenic injection and mixing characteristics of a real transcritical bi-shear injector. With this aim, a dynamic one-equation eddy-viscosity subgrid-scale model (for large eddy simulation), the Peng-Robinson equation of state (for calculating the thermodynamic properties), the NIST database (for estimating the transport properties) and the PISO algorithm (for velocity-pressure coupling) have been used to analyze various features of the transcritical turbulent bi-shear flow. Observations indicate that there is a good agreement between the results of the present work and previous experimental and numerical studies. Simulations show that due to the remarkable effects of pseudo-boiling and density stratification phenomena in preventing the sustained growth of the transcritical mixing layer, the potential core of the inner dense jet is much longer than that of the outer jet. However, due to the high sensitivity of isobaric specific heat to temperature, especially around the pseudo-boiling temperature, small temperature fluctuations drastically reduce the isobaric specific heat and in turn result in local distortion and weakening of the thermal shield. Subsequently, the vorticity generating mechanisms, including the baroclinic torque and volume dilatation, catch up and efficiently enhance the mixing quality.
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