Numerical study of the pseudo-boiling phenomenon in the transcritical liquid oxygen/gaseous hydrogen flame

Abstract

The interactions and effects of turbulent mixing, pseudo-boiling phenomena, and chemical reaction heat release on the combustion of cryogenic liquid oxygen and gaseous hydrogen under supercritical pressure conditions are investigated using RANS simulations. Comparisons of the present numerical simulation results with available experimental data reveal a reasonably good prediction of a supercritical axial shear hydrogen-oxygen flame using the standard k-ε turbulence model and the eddy dissipation concept combustion model with a 23 reaction steps kinetics for H2-O2 reaction. The present simulation qualitatively reproduced oxygen injection and its reaction with the co-flowing hydrogen, which is characterized by rapid flame expansion, downstream flame propagation, and expansion induced flow recirculation. Several turbulence models were used for numerical simulations. It is shown that the selection of an appropriate turbulence model for transcritical reacting flows is crucial and far more important than for subcritical reacting flows. It is indicated that the pseudo-boiling phenomena is the main reason for the considerable differences between the turbulence models in a transcritical flame. Also, it is demonstrated that the liquid oxygen core disappears faster in a non-reacting flow than in a reacting flow. The shear layer in the non-reacting flow is much stronger than reacting case; providing a large transfer of energy from the outer layer to the inner layer. At the supercritical injection conditions, the difference between the turbulence models is much less than the transcritical injection conditions.

Flame Anchoring of an H2/O2 Non-Premixed Flamewith O2 Transcritical Injection

“…In a nutshell, in the non-reacting case the two streams of reactants form a high velocity gradient shear-layer promoting mixing and shortening the penetration depth of the liquid O 2 jet, while in the reacting case the expansion caused by pseudo-boiling and combustion heat release push the H 2 jet away from the centerline, largely reducing the turbulent mixing. These deductions are in agreement with what was reported in [67]. Based on what was said in the introduction, solving the liquid oxygen interface without numerical oscillations requires robust and accurate numerical schemes.…”