Corrugated nozzles for acoustic and thrust benefits

Abstract

This paper presents the theoretical results based on new methods proposed in [1—4] for more efficiently mixing a supersonic jet with ambient air, effecting both jet noise reduction and nozzle thrust augmentation. This was obtained by 3D nozzle design incorporating a corrugated cross section nozzle shape with a sinusoidal lip line nozzle edge. Such a design was denoted in [1] as a Bluebell nozzle. The experimental tests of several Bluebell nozzle designs ([2]) have shown noise reduction relative to a convergent-divergent round nozzle with design exhaust Mach number Me = 1.5. The best design provides an acoustic benefit near 4dB with about 1% thrust augmentation. A Telescope nozzle ([3,4]) contains one or several internal components which are inserted in the divergent conical or planar main design near its exit. These designs provide additional thrust augmentation in the divergent portion of the nozzle of 20-30% compared with the conical or optimum single nozzle. Corrugated surfaces are proposed for two-contour nozzles including the centerbody (plug). Basically, numerical simulations were conducted only for supersonic flows into 3D and 2D Bluebell and Telescope nozzles. Several different shapes of corrugated surfaces for external and internal designs are analyzed and compared with usual round, rectangular and elliptical designs. New shapes of the Chisel and Screwdriver designs of the nozzle or centerbody (plug) allow more effective mixing and less thrust loss in comparison with the elliptic and rectangular shapes of equal cross sectional area. The nozzle thrust calculation was based on a full Navier-Stokes equation solver (NSE) and marching Euler code with and without boundary layer corrections.