Mixing Augmentation with Cooled Pylon Injection in a Scramjet Combustor

The improvements of mixing characteristics with a pylon fuel-injection system in a Mach 8 scramjet engine are investigated in this paper. Also, an efficient film-cooling method to protect the pylon injector from aerodynamic heating is explored. Three-dimensional Navier-Stokes equations, including the k-omega shear stress transport turbulence model, are solved with the finite-volume method, adopting the upwind method of Edwards' low diffusion flux splitting scheme. Pylon injection yields remarkable improvements in fuel penetration and fuel-air mixing rate, but the temperature on the pylon surface becomes too high for the pylon injector to stand in the scramjet combustor. The film-cooling methods proposed in the present study are found to be reliable cooling methods for the pylon injectors. Of the cases tested, when compared with the upward coolant injection, the downward coolant injection gives the same cooling effects with about 60% less mass flow.