NOZZLE THRUST OPTIMIZATION WHILE REDUCING JET NOISE

A Bluebell nozzle design concept is proposed for jet noise reduction w ith minimal thrust loss or even thrust augmentation. A Bluebell nozzle has a sinusoidal lip-line edge (chevrons) and a sinusoidal cross-sect ion shape with linear amplitude increasing downstream in the divergent nozzle part (corrugations). The experimental tests of several Bluebel l nozzle designs have shown noise reduction relative to a convergent-d ivergent round nozzle with design exhaust Mach number M(e) = 1.5. The best design provides an acoustic benefit near 4 dB with about 1% thrus t augmentation. For subsonic flow (M(e) = 0.6), the tests indicated th at the present method of design for Bluebell nozzles produces increase d levels of jet noise. The proposed designs incorporate analytical the ory and two- and three-dimensional numerical simulations. Full Navier- Stokes and Euler solvers were utilized. Boundary layer effects were us ed. Several different designs were accounted for in the Euler applicat ions.