Numerical Analysis of Scramjet Internal Flow by Hybrid Unstructured Grid Method

Computations of internal viscous flow fields of scramjet models were conducted at inflow Mach number of 3.4 and 5.45. An unstructured hybrid grid method was used to compute the scramjet models with and without a short strut. The numerical method to solve the Navier-Stokes equations on the hybrid grid was developed using a finite volume cell vertex scheme and the LU-SGS implicit time integration algorithm. The computational results revealed that a thick subsonic region did not exist in the combustor near the top wall at Mach number 5.45. It was a favorable feature to avoid the engine unstart. With the strut, relatively low velocity regions became larger and the down wash flow toward the cowl behind the step became strong. The overconcentration of the fuel toward the top wall during the weak combustion was found in the experiment. The reason of it was realized that the airflow near the injector was turned to the top wall due to the small influence by the combustion in the experiment.