The effect of flow structure on the combustion and heat transfer in a scramjet combustor

A combined experimental and computational study of two different swept-ramp injector configurations was conducted in a scramjet combustor. The object of the study was to determine the effect of mixing augmentation, resulting from the streamwise vortices generated by injector ramps, on scramjet engine operation characteristics, combustion, and heat transfer. Hydrogen was injected from the base of swept compression and expansion ramps in direct-connect tests that simulated flight at Mach 6.6.; The experimental effort included combustor wall pressure and heat flux measurements with Gardon gages and surface thermocouples for the two injector configurations. A novel, side-view laser light sheet technique was developed to obtain images of the combustion product distribution at selected planes in the closed combustor duct downstream of the swept-compression ramp injectors. In addition, a miniature refractory probe was developed to determine the pitot pressure at the exit of the combustor. Three-dimensional computations were made for mixing and reacting cases of the swept-compression ramp injector using the SPARK computer code. The flow field calculations were compared to the experimental measurements.; The experimental tests demonstrated combustor performance with parallel injection comparable to that reported using normal injection. This unusually rapid parallel jet mixing and combustion was obtained using swept ramp injectors with near-parallel injection. The experiments and calculations showed that the injectors were effective in promoting lateral spreading of the fuel jets. The incomplete penetration of the fuel jets in the direction normal to the walls was a major limiting factor in the amount of mixing that could occur for both configurations. In addition, the proximity of the burning shear layer to the injector wall led to increased heat transfer on the injector wall. The effect of the flow structure on the heat flux was not principally through a large increase in the film coefficient caused by the vortical flow. Instead, it was due to the proximity of the reacting fuel jet to the wall, which led to high adiabatic wall temperatures near the wall.{dollar}sp*{dollar} ftn{dollar}sp*{dollar}Originally published in DAI vol. 56, no. 10. Reprinted here with corrected text.