Analysis on Flow-Field Characteristics of a Scramjet Combustor with respect to Equivalence Ratio using IDDES Simulation

Abstract

Present study numerically investigated reactive flow-field characteristics of a direct-connect hydrogen-fueled scramjet combustor depending on a global equivalence ratio. The goal of this study is to analysis on detailed flame structure and combustion dynamics from both local and macroscopic perspectives of view. To this end, a high-resolution numerical simulation with an improved delayed detached eddy simulation (IDDES) and Jachimowski’s hydrogen-oxygen detailed chemical mechanism was conducted. The numerical framework utilized high-resolution numerical schemes, such as an optimized multi-dimensional limiting process (oMLP), with a high-order accuracy to achieve high-resolution and fidelity results. It was confirmed that the numerical framework has high-fidelity by validation using experimental data. Five injection pressures were selected to investigate the change in combustion dynamics depending on a global equivalence ratio. Numerical results show that maximum pressure is anchored at the cavity close-out region along the ramp angle of the rear wall, regardless of the equivalence ratio condition. This maximum pressure is formed by interaction with the combustion process and compressible effect, and it indicates the importance of appropriate treatment of the compressible effect on the simulation of a scramjet combustor. Each numerical result by different injection conditions clearly showed the difference in the formation of counter-rotating vortex pair (CRVP) and mixing characteristics of the fuel stream by injection pressure. An increase in the penetration height induces the exclusion of interaction with the combustor wall and recirculation zone of CRVP. It was confirmed that the penetration length and the flame thickness of the mixing layer on the outermost surface increased as the equivalence ratio increased.