Real-fluid flamelet modeling for gaseous hydrogen/cryogenic liquid oxygen jet flames at supercritical pressure

The primary goal of this study is to numerically model the transcritical mixing and reacting flow processes encountered in liquid propellant rocket engines. In order to realistically represent turbulence-chemistry interactions, detailed chemical kinetics, and non-ideal thermodynamic behaviors related to the liquid rocket combustion at supercritical pressures, the flamelet approach is coupled with real-fluid modeling based on the Soave-Redlich-Kwong (SRK) equation of state. To validate the real-fluid flamelet model, a gaseous hydrogen/cryogenic liquid oxygen coaxial jet flame at supercritical pressure has been chosen as a benchmark case. Numerical results are compared with experimental data obtained for the OH radical and the temperature distribution. It was found that weak flow recirculation is induced by the sudden expansion of cold core cryogenic oxygen associated with the pseudo-boiling process. This weak recirculation zone substantially influences the fundamental characteristics of liquid propellant reacting flows at supercritical pressures in terms of the spreading and the flame length. For the flame conditions employed in this study, the predicted contours of the OH radical are in good agreement with the experimental Abel transformed emission image in terms of the flame spreading angle and the flame location. Numerical results suggest that the real-fluid based flamelet model is capable of realistically predicting the overall characteristics of a turbulent non-premixed GH₂/LOx flame at supercritical pressures.