Fixed geometry controlled entrainment ventilated convergent nozzle and method

Abstract

A combination convergent jet engine aircraft nozzle (86, 142, 146) and a ventilation tube (88, 136, 144) are fixed in place and have no moving parts. Ambient air is entrained through duct inlets (96, 140, 154, 160), through the nozzle walls, through hollow struts (90, 138), the struts supporting and being connected to a hollow central tube (102, 144) or a plurality of tubes (136), to adjacent the downstream end of the nozzle to mix at takeoff with the jet forming gas exhaust. The ducts (102, 136, 144) are positioned with respect to the nozzle exhaust so that entrained ambient air flows into the gas exhaust during takeoff and so that the ambient air flow is substantially restricted or shut off during cruise flight. Ambient air inlet openings (160) are formed as a porous surface, the holes through the surface being generally in the shape of louvers (166) of which downstream end portions (174) are depressed inwardly of the outer wall surface of the nozzle to provide a minimum drag along the outer nozzle periphery during cruise flight and at takeoff. A method of positioning and fixing the outlet end of a noise suppressor within a convergent nozzle so that entrained ambient air flows into the gas exhaust during takeoff to substantially reduce the engine noise and so that ambient air is substantially restricted or is shut off entirely during cruise flight. The method in which ambient air is entrained in a noise suppressor within a convergent nozzle and is exited downstream adjacent the nozzle downstream end to mix with the gas exhaust during takeoff to suppress the engine noise, and at cruise flight substantially restricting or shutting off the ambient air through the noise suppressor by turning engine exhaust gas toward the noise suppressor axis downstream of the ambient air exit.