Advanced injection and mixing techniques for scramjet combustors

Abstract

Scramjet combustor fuel injection and mixing enhancement techniques are reviewed. The injection techniques include hole injection from the combustor wall, slot injection parallel to the flow, and injection from struts and the rear of ramps. Three new advanced mixing techniques are presented. The first is a combustor, curved so that buoyancy forces will aid in the penetration of the fuel across the combustor. The second is pulsation of the fuel injectors to increase penetration and mixing. A fluidic technique, a modified Hartmann-Sprenger tube, is identified as a strong candidate to generate the pulsations. The third is the injection behind pylons to allow deep penetration into the air stream. This technique is likely to produce high base pressures on the injector structure, particularly if base burning is encouraged. Curved or slanted pylons can be used to increase the recovery of fuel jet momentum. The potential of the new mixing techniques to increase scramjet engine performance is assessed.