Numerical Study of the Transcritical Injection and Mixing Dynamics of the Bi-shear Injectors

A numerical investigation has been conducted to explore the injection and mixing characteristics of a cryogenic coaxial shear injector under transcritical condition. A dynamic one-equation eddy-viscosity subgrid-scale model, used for Large-Eddy-Simulations (LES), along with the Peng-Robinson equation of state and a flow solver using the PISO algorithm for pressure–velocity coupling are used to evaluate various features of the present turbulent bi-shear flow. Moreover, transport properties of the cryogenic fluid under the transcritical condition are determined using the NIST REFPROP program. Experimental data of Davis and Chehroudi are used to validate the numerical results. Results show the capability of the abovementioned numerical framework to predict various characteristics of transcritical shear flows. Numerical simulations reveal that the formation and evolution of the transcritical injector’s mixing layers are controlled by: 1) recirculating bubbles located behind the injector’s inner post, 2) highly stratified shear layer, and 3) the thermal shield due to the pseudo-boiling phenomenon, such that their interactions with the emerged inner and outer shear jets, completely manage the structure of the shear layers.

Keywords:

Cryogenic coaxial injector , Transcritical condition , Injection and mixing , Shear layer structures.