Computational investigation of high pressure combustion mechanism in scram accelerator

A computational study was carried out to model the high-pressure combustion mechanism in scram accelerator. Fluid dynamic modeling was based on RANS equations for reactive flows and it was solved in a fully coupled manner using fully implicit-upwind TVD scheme. For the accurate simulation of high-pressure combustion in ram accelerator, 9-species, 25-step fully detailed reaction mechanism was incorporated with the existing CFD code previously used in the ram accelerator studies. The mechanism is based on GRI-Mech. 2.11 which includes pressure-dependent rate formulation indispensable for the correct prediction of induction time in high-pressure environment. A real gas equation of state was also included to account for molecular interactions and real gas effects of high-pressure gases. The present combustion modeling is compared with previous ones using 8-step or 19-step mechanisms and ideal gas assumption. The result shows that mixture ignition characteristics are very sensitive to the combustion mechanisms, and the different mechanisms result in completely different reactive flow-field characteristics that have a significant relevance to the operation mode and the performance of scram accelerator.