Method and apparatus for suppressing the noise of a fan-jet engine

Claim 1

In a jet propulsion plane having a fan-jet engine, the combination comprising: a tubular housing disposed in spaced relation around the aft portion of the casing of said engine and projecting beyond the aft edge thereof, fan air of said engine flowing through the space between said housing and said casing; a convoluted ring the forward edge of which is fixedly joined to the aft edge of said casing, said ring being formed with lobes which extend axially thereof and gradually increase the radial dimension in the downstream direction so that their aft ends project both radially inwardly and radially outwardly from the aft edge of said casing, said lobes abutting the wall of said housing at the aft end of the latter; and a thrust nozzle the forward edge of which is fixedly joined to the aft edge of said housing, fan air of said engine flowing from the space between said housing and said casing into the spaces between the lobes of said ring and thence dividing therein for flow into said nozzle, the aft ends of the lobes of said ring being fixedly joined together so that exhaust gas of said engine flowing through the radially projecting passages bounded by the inner surfaces of said lobes and thence dividing therein for flow into said nozzle, whereby alternately disposed streams of fan air and exhaust gas enter the forward end of said nozzle.