Effect of the injector flow field on the performance of a model scramjet combustor

Numerical simulations of the supersonic injection of hydrogen through a supersonic, diamond-shaped wall mounted injector as well as an equivalent circular injector, into a Mach 2.4 supersonic crossflow in a model scramjet combustor, have been carried out. Two equivalence ratios, 0.3 and 0.5, corresponding to pure scram mode of operation, are considered. Oil flow images and Schlieren images overlaid with contours of hydrogen mass fraction are used to demonstrate that the fuel penetrates higher with the diamond injector and that the fuel issues out of a part of the injector only on account of the jet being over-expanded. The higher penetration leads to better near-field mixing, but the mixing slows down in the far field. The circular injector exhibits more lateral spreading as a result of flow separation ahead of the injector. Although the penetration and near-field mixing are less, mixing continues farther downstream resulting in almost the same level as that of the diamond injector.