Aerodynamic Control and Mixing with Ramp Injection

Abstract

Experiments have been conducted in the GALCIT Supersonic Shear Layer Facility (S3L) to investigate the behaviour of a flow and geometry with many features that are potentially useful for a Supersonic Combustion Ramjet (SCRAMJET) engine - a recirculation zone for flameholding, enhanced mixing between fuel and air, and low total-pressure losses. In a subsonic diffuser configuration with no mass injection, the exit velocity and guidewall static-pressure profiles collapse over a large range of inlet Reynolds numbers. Significant control of exit velocity and guidewall pressure profiles is possible via injection through a perforated ramp into the freestream. The control authority on the overall pressure coefficient increases with increasing inlet Reynolds number. Simple control volume models put bounds on the overall pressure coefficient for the device. In low-supersonic flow, the area ratio calculated from measured pressures agrees well with the visual shear-layer thickness, illustrating the low total-pressure losses present. Further control is possible through variable heat release from a fast-chemical reaction between reactants carried in the two streams. At the highest heat release studied, mass injection requirements are lowered by, roughly, a factor of two. Measurements of mixing inferred from the temperature rise from such a reaction indicate a high level of mixing vs. classical free shear layers. As in free shear layers, however, the level of mixing begins to decrease with increasing heat release.