Numerical simulations of turbulent flows in aeroramp injector/gas-pilot flame scramjet

To uncover the internal flow characteristics in an ethylene-fueled aeroramp injector/gaspilot (ARI/G-P) flame scramjet,a Reynolds-averaged Navier-Stokes (RANS) solver is constructed under a hybrid polyhedral cell finite volume frame.The shear stress transport (SST) k-o model is used to predict the turbulence,while the Overmann's compressibility corrected laminar flamelet model is adopted to simulate the turbulent combustion.Nonreactive computations for Case 1 (G-P jet on),Case 2 (ARI jets on),and Case 3 (both ARI and G-P jets on) were conducted to analyze the mixing mechanism,while reactive Cases 4-7 at equivalent ratios of 0.380,0.278,0.199 and 0.167 respectively were calculated to investigate the flame structure and combustion modes.The numerical results are compared well to those of the experiments.It is shown that the G-P jet plays significant role in both the fuel/air mixing and flame holding processes;the combustion for the four reactive cases takes place intensively in the regions downstream of the ARI/G-P unit;Cases 4 and 5 are under subsonic combustion mode,whereas Cases 6 and 7 are mode transition critical and supersonic combustion cases,respectively;the mode transition equivalent ratio is approximately 0.20.