초록 ▼

A flow control device generates counter-rotating vortices in the boundary layer of the flow in a supersonic inlet diffuser for an aircraft turbine engine. The flow control device comprises a flap attached to the duct wall for selective deployment, wherein it extends into the boundary layer, and retr

A flow control device generates counter-rotating vortices in the boundary layer of the flow in a supersonic inlet diffuser for an aircraft turbine engine. The flow control device comprises a flap attached to the duct wall for selective deployment, wherein it extends into the boundary layer, and retraction, wherein it lies substantially flush with the duct wall. In one embodiment an actuating mechanism comprising one or more shape-memory alloy wires moves the flap between two stable positions. In another embodiment the deployment height of the flap can be controlled as desired, preferably using a shape-memory alloy actuating mechanism. Typically, an array of plural flow control devices is disposed in the inlet duct for selective actuation according to a predetermined schedule.

대표청구항 ▼

1. An inlet diffuser for introducing air flow to a turbine engine, the diffuser comprising: an inlet duct having a portion bounded by mutually facing duct walls for accepting air traveling at a velocity in excess of the speed of sound in the air (M >1) and passing air flow traveling in said duct at

1. An inlet diffuser for introducing air flow to a turbine engine, the diffuser comprising: an inlet duct having a portion bounded by mutually facing duct walls for accepting air traveling at a velocity in excess of the speed of sound in the air (M >1) and passing air flow traveling in said duct at M >1 through a shock front between said facing duct walls at a location in said inlet duct upstream of the turbine engine to decelerate the air flow to a velocity less than the speed of sound in the air (M <1), wherein a boundary layer proximate to at least one duct wall of said facing duct walls interacts with the shock front;an array of a plurality of flow control devices disposed upstream of said location and arranged over an area of said at least one duct wall within said portion of said inlet duct, each of said plurality of flow control devices including a flap having a first portion attached to said at least one duct wall and an active portion movable between (i) a retracted position wherein said active portion is substantially flush with a region of said at least one duct wall adjacent said flap for minimizing disturbance of air flow in a boundary layer trailing each of said flow control devices, and (ii) a deployed position wherein said active portion extends a predetermined height above said region of said at least one duct wall for altering air flow in the boundary layer trailing each of said flow control devices that interacts with the shock front; andan actuating mechanism including a shape-memory alloy actuating member, said actuating mechanism being operatively connected to said flaps for deforming at least one of said flaps to effect movement of said active portion thereof between the retracted position and the deployed position. 2. An inlet diffuser as in claim 1, wherein: said area of said at least one duct wall has a continuous surface, said active portion in the retracted position being disposed on top of said continuous surface substantially flush therewith and in the deployed position being disposed with a space between said active portion and said continuous surface; andsaid array of said plural flow control devices includes at least one said flap in which said active portion can assume only one of the retracted position and the deployed position when said flap is deformed by said actuating mechanism. 3. An inlet diffuser as in claim 2, wherein said active portion is confined in an elastically deformed condition and is movable between one stable position in which said active portion is elastically deformed for holding said active portion in one of the retracted position and the deployed position and another different stable position in which said active portion is elastically deformed for holding said active portion in the other of the retracted position and the deployed position; andsaid shape-memory alloy actuating member includes at least two shape-memory alloy actuating wires operatively attached in tension between said active portion and said at least one duct wall, one said actuating wire being elongated when said active member is in one of its stable positions so that heating said one wire contracts it and moves said active portion to its other stable position and elongates the other said actuating wire. 4. An inlet diffuser as in claim 3, wherein said active portion includes a flat body member and said first portion includes a pair of flat tongues attached to said at least one duct wall, said tongues being integral with said body member and attached thereto an end of said tongues spaced from where they are attached to said at least one duct wall so that said flap is elastically deformed substantially in the plane thereof to elastically buckle said body member out of the plane thereof, said body member being elastically buckled in a first direction in one stable position thereof and being elastically buckled in a second direction in the other stable position thereof. 5. An inlet diffuser as in claim 4, wherein: said flap has a trapezoidal planform with parallel sides of the trapezoid aligned generally with the direction of the air flow, one of the parallel sides having a cutout forming said tongues and one of the nonparallel sides of the trapezoid being perpendicular to the parallel sides and disposed at the downstream end of said flap relative to the general direction of the air flow;said actuating wires are attached to said flap proximate to the other of the parallel sides of the trapezoid; andsaid flap in the retracted position is bent over a protuberance on said at least one duct wall. 6. An inlet diffuser as in claim 1, wherein said array of said plural flow control devices includes a plurality of said flaps, said active portion of each of which can assume the retracted position and any of a plurality of deployed positions at different heights above said region of said at least one duct wall adjacent said flap. 7. An inlet diffuser as in claim 6, wherein: each said flap is elastically deformable and spaced from a flap adjacent thereto; andsaid active portion of each said flap in the retracted position is disposed on top of a continuous surface of said at least one duct wall substantially flush therewith. 8. An inlet diffuser as in claim 7, wherein said active portion includes a flat body member and said first portion includes a first tongue attached to said at least one duct wall and a second tongue operatively attached to said actuating mechanism, said first and second tongues being attached to said body member at an end of said tongues opposite to where they are attached to said at least one duct wall and said actuating mechanism so that movement of said second tongue to a plurality of different positions elastically deforms said flap to move said active portion between said retracted position and a plurality of said deployed positions corresponding to different positions of said second tongue. 9. An inlet diffuser as in claim 8, wherein: said shape-memory alloy actuating member is operatively attached to said second tongue of at least one said flap and held in tension; andsaid actuating mechanism includes a control circuit for introducing electric current to said shape-memory alloy actuating member to cause it to contract and relax in accordance with a desired deployment position. 10. An inlet diffuser as in claim 9, wherein said actuating mechanism includes a closed-loop feedback control system for maintaining said active portion in a desired deployed position in accordance with an input to said control system. 11. An inlet diffuser as in claim 9, wherein said shape-memory alloy actuating member is operatively attached to said second tongue of each of plural said flaps. 12. An inlet diffuser as in claim 9, wherein said body member has a planform comprising an isosceles triangular shape having a base attached to said first and second tongues and straight sides disposed substantially symmetrically with the general direction of the air flow with the apex of the triangle downstream of the base. 13. An inlet diffuser as in claim 8, wherein said actuating mechanism can vary the height said active portion extends above said at least one duct wall to any desired height up to about 0.6 of the height of the boundary layer at the location of said flap. 14. An inlet diffuser as in claim 9, wherein said body member has a planform comprising a curved wishbone shape having a base attached to said first and second tongues and sides that in a direction downstream in the airflow direction curve inwardly and then at an inflection point curve concavely in the reverse direction to form a sharp point, said sides being disposed substantially symmetrically with the general direction of the air flow with the point of the wishbone downstream of the base. 15. An inlet diffuser as in claim 9, wherein said body member has a planform comprising a curved ogive shape having a base attached to said first and second tongues and sides that in a direction downstream in the air flow direction curve inwardly to form a convex, pointed arch planform, said sides being disposed substantially symmetrically with the general direction of the air flow with the point of the arch downstream of the base. 16. A method of controlling shock wave boundary layer interaction in an inlet diffuser according to claim 1, the method comprising moving active portions of selected said flaps between the retracted position and the deployed position. 17. A method of controlling shock wave boundary layer interaction in an inlet diffuser according to claim 6, the method comprising moving said active portions of selected said flaps to one of a plurality of deployed positions at different heights above said at least one duct wall.