Experimental investigation of a supersonic ejector nozzle using forced mixing tabs

Nicholas R Heinz, Purdue University

Abstract

In considering propulsion systems for future supersonic civil transport, it is important to consider all design conditions for a given system. Not only does the design need to accomplish goals for cruise efficiency, but it also needs to perform in off-design conditions. The typical converging-diverging nozzle design for supersonic flight encounters significant performance issues when operating in the low nozzle pressure ratio regime associated with takeoff, landing, and loiter. The massive separation that occurs during this regime leads to unacceptable noise levels and a significant decline in nozzle performance. As a proposed solution to this problem, a converging-diverging nozzle with rotatable clamshells was implemented and tested in previous investigations. The proposed nozzle incorporated added benefits from its ejector design that provided the possibility for increased thrust, and noise benefits due to flow entrainment and enhanced mixing. As demonstrated in the previous investigations, the ejector nozzle suffered from lower than expected performance. It was determined that reversed flow and separation caused by the failure of the free-mixing layer to attach to the ejector shroud was the root cause of the performance issues. In combating these issues, this investigation explores the addition of forced mixing techniques in order to improve the nozzle performance. Triangular mixing tabs were added to the nozzle throat in order to generate enhanced mixing by means of streamwise vortices formed from the tab geometry. A series of plume velocity surveys were performed in order to determine the effectiveness of the forced mixing mechanisms, and along with flow visualizations, a determination on the mixing tab performance was formed. Results indicated that the shear layer is now attached to the clamshell surface and the separation inside the ejector has primarily disappeared.

Degree

M.S.A.A.

Advisors

Sullivan, Purdue University.

Subject Area

Aerospace engineering

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