Abstract
Particle image velocimetry measurements were made along the center plane of a scramjet cavity flameholder to analyze simulated inlet flow distortion in the direct-connect test environment. Mach 3 nonreacting tests examined an oblique shock impinging upon locations in- and upstream of the cavity, including cases with wall-normal air injection upstream of the cavity to simulate fuel injection. Addition of flow distortion altered the size and shape of the primary recirculation region within the cavity by deflecting the bounding shear layer: the recirculation region was compressed by shock impingement upstream of the cavity, and shock impingement on the cavity itself expanded it. Air injection upstream of the cavity thickened the shear layer and produced a stronger effect on velocity direction than magnitude, preventing the formation of a large-scale recirculation region in two of the three shock locations studied. Flow distortion and upstream air injection both increased flow unsteadiness, with the greatest increases occurring in the shear layer and above the cavity closeout ramp. Additionally, results suggest the formation of spanwise secondary flow patterns that may account for flow nonuniformities observed in prior studies. This work presents the first velocimetry characterization of a scramjet cavity flameholder under distorted-flow conditions.
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