Exhaust flow mixers and nozzles

Claim 1

A turbofan aeroengine comprising: a core engine; a bypass duct surrounding said core engine and having a single propulsion nozzle, a turbine exhaust stream and a bypass fan air stream being mixed internally of said aeroengine to produce a combined exhaust stream for passage through said propulsion nozzle; said core engine having an exhaust mixing nozzle of the multi-lobed type having a shape in end elevation comprising lobes radiating from a common central area with troughs between said lobes; said lobes and troughs comprising, respectively, outwardly directed flow channels for said turbine exhaust stream and inwardly directed flow channels for said bypass fan air stream to mix a substantial portion of said turbine exhaust stream and said bypass air stream; and means including said exhaust mixing nozzle for providing a Coanda Effect to those portions of said turbine exhaust stream and said bypass air stream flowing past said exhaust mixing nozzle, for generating multiple vortices of a mixed turbine exhaust stream and bypass fan air stream downstream of said exhaust mixing nozzle, and for mixing a substantial portion of said turbine exhaust stream and said bypass fan air stream to produce a combined mixed exhaust stream for passage through said propulsion nozzle, said means including; said exhaust mixing nozzle being formed of a plurality of twisted flow surfaces, said twisted flow surfaces having upstream and downstream ends and having a predetermined and progressive degree of twist between said upstream and said downstream ends, peripherally adjacent ones of said twisted flow surfaces being of mutually complementary and opposite twists to define said outwardly and inwardly directed flow channels of said lobes and said troughs, said peripherally adjacent twisted lobe surfaces being peripherally adjoining at least at their upstream ends and over at least a major portion of said inwardly directed flow channels; said twisted flow surfaces providing a Coanda Effect to those portions of said turbine exhaust stream and said bypass fan air stream flowing over said flow surfaces to deflect said stream portions without said stream portions breaking away from said flow surfaces and generating multiple vortices of a mixed turbine exhaust stream and bypass fan air stream downstream of said downstream end of each of said flow surfaces, adjacent circumferential ones of said vortices being counter-rotating to promote further mixing, said exhaust mixing nozzle thereby producing a mixing action substantially thoughout said combined exhaust stream before passage of said combined exhaust stream through said propulsion nozzle.