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

Claim 1

In an aircraft housing enclosing a fan jet engine and a tailpipe through which exhaust gas of said engine is discharged, the combination comprising: a conduit operatively associated with said housing and disposed in spaced relation around said tailpipe to provide for flow of secondary air of said engine therebetween, said conduit projecting from the aft end of said tailpipe; a thrust nozzle attached to the aft end of said conduit; a set of first vanes operatively associated with said housing and extending rearwardly from the aft end of said tailpipe to a point adjacent the aft end of said conduit, said vanes being spaced apart circumferentially of said tailpipe and pivoted at their forward ends for rotation about axes disposed transverse to the longitudinal axis of said tailpipe; a set of second vanes operatively associated with said housing and extending rearwardly from the aft end of said tailpipe to a point adjacent the aft end of said conduit, said second vanes being respectively disposed between said first vanes and pivoted at their aft ends for rotation about axes disposed transverse to the longitudinal axis of said tailpipe, said first and second vanes being movable between a first position wherein their longitudinal axes are substantially parallel with the longitudinal axis of said tailpipe and a second position wherein their longitudinal axes are inclined relative to said tailpipe longitudinal axis, whereby when said first and second vanes are in said first position said exhaust gas flows through the channel bounded by the inner surfaces of said vanes and said secondary air flows between the outer surfaces of said vanes and the inner surface of said conduit, and when said first and second vanes are in said second position part of said exhaust gas flows along the outer surfaces of said second vanes toward said conduit and part of said secondary air flows along the outer surfaces of said first vanes toward the longitudinal axis of said tailpipe; and means for moving said first and second vanes between said first and second positions thereof.

Claim 9

A method of operating an aircraft having a fan jet engine, which comprises: in a first operational mode of said aircraft, flowing exhaust gas of said engine to a thrust nozzle in a columnar stream, and flowing secondary air of said engine to said thrust nozzle in a stream disposed around said stream of exhaust gas; and in a second operational mode of said aircraft, flowing part of said exhaust gas outwardly into said stream of secondary air at points spaced around the inner boundary of the latter, and flowing part of said secondary air inwardly into said stream of exhaust gas at points spaced around the perimeter of the latter.

Claim 10

A method of operating an aircraft having a fan jet engine, which comprises: in a first operational mode of said aircraft, flowing exhaust gas of said engine to a thrust nozzle in a columnar stream, and flowing secondary air of said engine to said thrust nozzle in a stream disposed around said stream of exhaust gas; and in a second operational mode of said aircraft, flowing part of said exhaust gas outwardly into said stream of secondary air at points spaced around the inner boundary of the latter, and flowing part of said secondary air inwardly into said stream of exhaust gas at points spaced around the perimeter of the latter.

Claim 11

A method of operating an aircraft having a fan jet engine, which comprises: in a first operational mode of said aircraft, (a) discharging exhaust gas of said engine to a thrust nozzle by flowing it through a tube the wall of which is at least partially formed of a plurality of axially extending vanes, said vanes being alternately hinged at their forward and aft ends for rotation about axes disposed transverse to the longitudinal axis of said wall, the aft end of said tube being substantially coterminous with the forward end of said thrust nozzle and spaced inwardly thereof so that said exhaust gas is discharged into the central portion of the throat of said thrust nozzle, and (b) discharging fan air of said engine to said thrust nozzle by flowing it through the space between said tube and a conduit disposed in spaced relation around the latter, the aft edge of said conduit being joined to the forward edge of said thrust nozzle, fan air thus flowing into the throat of said thrust nozzle in an annular stream which surrounds said exhaust gas; and in a second operational mode of said aircraft, moving the free ends of said vanes toward the longitudinal axis of said tube thereby to deflect part of said exhaust gas outwardly into fan air flowing along the inner surface of said conduit and to permit flow of part of said fan air inwardly into the part of said exhaust not deflected outwardly as aforesaid, said exhaust gas and fan air thus flowing into the throat of said thrust nozzle in an intermixed stream.

Claim 12

A method of operating an aircraft having a fan jet engine, which comprises: in a first operational mode of said aircraft, (a) discharging exhaust gas of said engine to a thrust nozzle by flowing it through a tube the wall of which is at least partially formed of a plurality of axially extending vanes, said vanes being alternately hinged at their forward and aft ends for rotation about axes disposed transverse to the longitudinal axis of said wall, the aft end of said tube being substantially coterminous with the forward end of said thrust nozzle and spaced inwardly thereof so that said exhaust gas is discharged into the central portion of the throat of said thrust nozzle, and (b) discharging fan air of said engine to said thrust nozzle by flowing it through the space between said tube and a conduit disposed in spaced relation around the latter, the aft edge of said conduit being joined to the forward edge of said thrust nozzle, fan air thus flowing into the throat of said thrust nozzle in an annular stream which surrounds said exhaust gas; and in a second operational mode of said aircraft, moving the free ends of said vanes toward the longitudinal axis of said tube thereby to deflect part of said exhaust gas outwardly into fan air flowing along the inner surface of said conduit and to permit flow of part of said fan air inwardly into the part of said exhaust not deflected outwardly as aforesaid, said exhaust gas and fan air thus flowing into the throat of said thrust nozzle in an intermixed stream.