Aerodynamic performance of augmented supersonic nozzles

The objective of this study is to understand how internal engine corrugated seals affect the aerodynamic performance of a convergent/divergent supersonic nozzle all the while promoting mixing. These corrugated seals are designed to protrude into the flow to alter the design pressure ratio of the nozzle through changes in area ratio. Measurements comprise axial thrust for nozzle pressure ratios ranging continuously from overexpanded to underexpanded nozzle flow states. Optical flow measurements using a z-type schlieren system are also used to qualitatively visualize the affect of protrusion depth on shock strength and boundary layer thickness at the nozzle exit. Findings reveal the effect of the corrugated seals on the double-shock pattern that forms from the imperfect expansion of the gas through this sharp throat nozzle. As much as a 2% increase in thrust coefficient is observed with one of the corrugated seal concepts and over a broad operating envelop corresponding to both overexpanded and underexpanded nozzle states.