Thrust characteristics of a supersonic mixer ejector

Abstract

This article describes recent findings relative to the thrust performance of supersonic mixer ejectors. Mixer ejectors are a candidate means to mix out the high-velocity engine exhaust on the High Speed Civil Transport (HSCT) aircraft, thereby reducing jet noise at takeoff and landing. In the present work, data and analyses are presented that demonstrate that mixer ejectors can provide rapid mixing of a supersonic jet for acoustic benefits, all while increasing aircraft system static thrust. Jet engine thrust data is presented that demonstrates that a properly designed choked mixer nozzle has essentially no thrust loss when compared to conventional axisymmetric nozzles and mixer ejector thrust gains are invariant over a range of pressure ratios that choke the lobed nozzle. Model data of higher pressure-ratio mixer ejectors (i.e., consistent with HSCT applications) are analyzed to provide relevant thrust parameters. Comparisons are made with a conventional slot-nozzle ejector. A principal finding of this study is that the mixer ejector thrust performance is particularly sensitive to secondary inlet flowfield conditions and geometry. With proper inlet geometries, mixer ejector thrust performance was found to substantially exceed that of the slot-nozzle ejector.