In the design of a jet engine exhaust nozzle for civilian supersonic cruise vehicles, it is necessary to consider both the supersonic cruise efficiency and the noise generated during terminal area operations. The convergent-divergent geometry necessary for cruise efficiency, will separate when operated at the lower nozzle pressure ratios associated with take-off and initial climb, causing unacceptable noise levels. One proposed solution is to comprise the divergent geometry of two rotatable clamshell bodies. These clamshell components would be rotated open during low nozzle pressure ratio operation, to effectively eliminate the divergent geometry and effect a subsonic ejector nozzle. These clamshells have the added benefit of functioning as thrust reversers and eliminating the need for a separate such system. This work, in general, investigates the effectiveness of a preliminary clamshell ejector design. Specifically, a seven-hole probe mounted on an automated, 2-axis traverse is used to collect wake survey data in the exhaust plume of the test nozzle in several configurations. This survey data is used to create velocity profiles of the jet plume and calculate thrust coefficients. In addition, several flow visualization techniques are utilized to further explore the flow structure near the geometry surface. Results indicate that the mixing layer between the primary and secondary streams is failing to attach to the ejector shroud, leading to separation and recirculation near the internal ejector shroud surfaces. Separation in these areas is causing streamwise vortices to be shed from the ejector surfaces. Thrust calculations indicate that the ejector configuration provides significant performance benefits reletive to the convergent-divergent cruise geometry, but is causing negative thrust augmentation.
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