ENHANCED MIXING OF SUPERSONIC JETS

An experimental study of supersonic mixer nozzles in a coflowing stream has been conducted in the United Technologies Research Center open jet acoustic wind tunnel. Enhanced supersonic jet mixing is important in a number of applications including jet exhaust noise reduction and improved flow distribution within engine combustors. Recently discovered novel concepts promoting enhanced mixing via the introduction of axial vorticity into the exhaust have resulted in studies of the mixing process for nozzles operating at low, subsonic Mach number conditions and low temperatures. The goal of the present experimental study was to evaluate these approaches to jet mixing in the high-temperature, supersonic primary flow regime typical of turbofan/turbojet engine operation. Jet total temperature, total pressure, static pressure, and velocity distributions were measured to characterize the mixing process for baseline slot and circular nozzles, and for several mixer nozzles. The measurements were made at a jet exit Mach number of 1.5, a wind-tunnel forward flight Mach number of 0.5, and a jet total temperature of 1000-degrees-F. A principal conclusion of this study is that the axial vorticity mixing mechanism previously shown to be responsible for rapid mixing in low-speed, subsonic flows is also effective in a supersonic flow environment. Reductions in nozzle potential core length of approximately a factor of two relative to the slot nozzle configuration were observed for one of the mixer nozzles studied.