Abstract A mechanism for attenuating sound pressure levels in the fluid passageways of an aircraft jet engine comprising a plurality of pivotally attached vane members each having a pair of oppositely facing acoustically treated surfaces. The vane members are stowed for cruise flight in positions aligned along and parallel to the wall of the passageway, wherein fluid flow occurs over only one of said oppositely facing surfaces. The vanes are pivotable along axes parallel to the flow into operative noise suppression positions perpendicular to said wall in which flow occurs over each of said surfaces, thereby increasing attenuation of sound pressure levels in said passageway. The preferred embodiment involves a turbofan jet engine wherein the vane members are stowed along an outer wall in overlapping fashion and the means for pivotally moving the members comprises a power actuated ring member which pivotally displaces each vane into a radial position wherein adjacent vanes cooperate to form trapezoidal acoustic chambers to reflect and dampen sound pressure wave fronts.
In combination with a jet engine having annular exhaust passageway walls formed by an outer cowling structure and the engine center body structure, a mechanism for attenuating sound pressure levels comprising: a plurality of vane members having oppositely facing exterior surfaces which are acoustically treated; said vane members being pivotally mounted within said passageway on said outer cowling structure on axes aligned parallel to the direction of flow of exhaust gases, and being so sized and spaced apart from one another that they may Be radially deployed to extend substantially across said annular passageway to thereby form a substantially closed trapezoidal chamber between each adjacent vane member to reflect and dampen sound pressure levels within said passageway; and means for pivotally moving said vane members from their radially deployed positions into stowed positions adjacent to the surface of the outer cowling surface and wherein the outer face of each vane member is disposed in overlapping fashion upon the inner face of a next adjacent vane member to thereby prevent stray airflow between vane members and to minimize drag within the passageway for cruise flight.
Claim 2
Dependent Claim
184 words
In combination with a jet engine having annular exhaust passageway walls formed by an outer cowling structure and the engine center body structure, a mechanism for attenuating sound pressure levels comprising: a plurality of vane members having oppositely facing exterior surfaces which are acoustically treated; said vane members being pivotally mounted within said passageway on said outer cowling structure on axes aligned parallel to the direction of flow of exhaust gases, and being so sized and spaced apart from one another that they may Be radially deployed to extend substantially across said annular passageway to thereby form a substantially closed trapezoidal chamber between each adjacent vane member to reflect and dampen sound pressure levels within said passageway; and means for pivotally moving said vane members from their radially deployed positions into stowed positions adjacent to the surface of the outer cowling surface and wherein the outer face of each vane member is disposed in overlapping fashion upon the inner face of a next adjacent vane member to thereby prevent stray airflow between vane members and to minimize drag within the passageway for cruise flight.
Claim 3
Dependent Claim
30 words
The mechanism of claim 1 wherein said means for pivotally moving said vane members comprises a power actuated ring member which is operably connected to each of said vane members.
Claim 4
Dependent Claim
34 words
The mechanism of claim 1 wherein said vane members comprise thin aerodynamically clean airfoil sections having tapered leading and trailing edges which extend substantially across said annular passageway when disposed in said operative positions.
Claim 5
Dependent Claim
86 words
The mechanism of claim 3 wherein each of said vane members comprises: perforated sheet exterior skin members, honeycomb core attached to said skin members, a hinge fitting connected to said honeycomb core having a lug member disposed for attachment to said means for pivotally moving said members, wherein said skin members, honeycomb core and hinge fittings are integrally constructed and connected to form a rigid vane member, and wherein said hinge fitting further comprises means for centering said ring member with respect to said vane member.