US3614260A

US3614260A - Blades or vanes for fluid flow machines

Info

Publication number: US3614260A
Application number: US855668A
Authority: US
Inventors: John H Ellinger
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1968-09-12
Filing date: 1969-09-05
Publication date: 1971-10-19
Anticipated expiration: 1988-10-19
Also published as: GB1235545A; DE1946086B2; DE1946086C3; FR2017885A1; DE1946086A1

Abstract

A variable geometry blade or vane particularly for use in a gas turbine engine comprises a rigid spine, a thin flexible sheet shaped to form the aerodynamic surface of the nose or tail of the blade, and actuation means adapted to move the sheet relative to the spine to vary the blade camber.

Description

States Patent John 111. Ellinger Mickleover, Derby, England 855,668

Sept. 5, 1969 Oct. 19, 1971 Rolls Royce Limited Derby, England Sept. 12, 11968 Great Britain Inventor App]. No. Filed Patented Assignee Priority BLADES 0R VANES FOR FLUID FLOW MACHINES 7 Claims, 3 Drawing Figs.

user. 416/23, 4l6/l32,416/158,416/24O m. m F01d 7/00 Field of Search 416/23, 24, 132, 240, 84, 15s

[56] References Cited] UNITED STATES PATENTS 2,616,509 11/1952 Thomas 416/84 2,967,573 1/1961 Johnson 416/84 3,042,371 7/1962 Fanti 416/226 X 3,158,338 11/1964 Cushman 416/84X FOREIGN PATENTS 100,913 9/1925 Austria 416/240 961,742 4/1957 Germany 416/240 Primary Examiner-Everette A. Powell, Jr. Attorney-Cushman, Darby & Cushman ABSTRACT: A variable geometry blade or vane particularly for use in a gas turbine engine comprises a rigid spine, a thin flexible sheet shaped to form the aerodynamic surface of the nose or tail of the blade, and actuation means adapted to move the sheet relative to the spine to vary the blade camber,

PATENTEDUET 19 197i Inventor Joy/v JZE 14/4/655' Attorneys BLADES R VANES FOR FLUID FLOW MACHINES This invention relates to a blade or vane for use in a fluid flow machine such as a gas turbine engine.

Particularly when considering the vanes of gas turbine engines there are considerable advantages to be gained by providing some form of variation of the camber of the blades. However, this is difficult to achieve reliably, and may particularly be so where the vanes are subject to conditions promoting vibrations and are structural members in addition to carrying aerodynamic loads. Such a case, for instance arises where the vanes form a spoked structure which carries a bearing.

The present invention provides a blade or vane which can be used to carry loads other than it aerodynamic loads while being enable to vary its camber in response to variation of flight condition.

According to the present invention a blade or vane for use in a fluid flow machine comprises a rigid spine, a thin flexible sheet shaped to form the aerodynamic surface of either the nose or the tail of the blade, and actuation means whereby the sheet may be moved so as to vary the camber of the blade.

Preferably said sheet is attached to one flank of the blade and extends to the other flank, and said actuation means preferably move that portion of the sheet on said other flank substantially in the direction of the mean chord line of the blade.

Said actuation means preferably comprise a plurality of hydraulic bellows which act on the extremity of the sheet.

Said spine may extend into the hollow of said formed sheet, and additional actuation means may be provided in the form of a plurality of tubular members lodged between the spine and the sheet and adapted to be inflated with foam or the like.

Preferably inextensible ties extend from one flank portion of the formed sheet to the other flank portion.

The present invention will now be particularly described merely by way of example with reference to the accompanying drawings in which:

FIG. 1 is a partly broken away side elevation of a gas turbine engine comprising blades according to the present invention,

FIG. 2 is a perspective and partly broken away view of a single blade from the engine of FIG. 1 and according to the present invention, and

FIG. 3 is a transverse section through the blade of FIG. 2. FIG. 1 shows a gas turbine engine comprising a main gas generator section 11 and a fan 12. The fan comprises a plurality of rotor blades 13 which rotate within a cowling 14, the cowling 14 being attached to fixed structure of an aircraft (not shown). The gas generator section 11 is carried from the cowl 14 by way of a plurality of stator blades 15 which extend between the cowl and the'gas generator in radially extending array and which perform the dual purpose of providing mechanical support for the generator section and acting as outlet guide vanes for the fan 12.

It will be appreciated that should some catastrophic failure occur such for instance as a bird strike destroying some of the blades 13, it would be possible to considerably reduce the otherwise inescapable wind-milling drag of the engine by varying the camber of the stators 15. As explained below with reference to FIGS. 2 and 3 this possibility is carried into effect by the present invention.

FIG. 2 is a perspective view of one of the blades 15. Each blade 15 comprises a spine portion 16 of solid metal which comprises the central portion of the blade and which also forms the rear sections of both flanks of the blade. This spine is designed to be of sufficient mechanical strength to carry out the mechanical requirement of the blade and shaped at the nose end to the profile of one blade surface in each extreme position. Surrounding the nose portion of the spine 16 there is a thin sheet member 17 which comprises a thin sheet of metal bent to form a substantially hairpin section and which forms the forward aerodynamic surfaces of the blade. This member 17 is attached to the convex flank of the blade at 18 and extends from there to form the nose of the blade, doubles back on itself at the nose and extends along the concave flank of the blade to a position approximately halfway along this flank at 19. The attachment at 18 is rigid; the attachment at 19 is made by way of actuation means described below.

To stiffen the member 17 and to constrain its movement into an aerofoil shape under all its working conditions a plurality of

cross ties

20 and 21 are provided. These ties extend between the opposite flanks of the blade formed by the member 17 and pass through slots formed in the spine 16. it will be appreciated that the ties prevent any considerable deformation of the surfaces of the member 16 away from their aerodynamic shape. The ties are attached to the interior of the member 17 by welding or a similar process, but in any case the ties are nicked at their attachment to the interior of the member so that they tend to hinge at these points rather than bending over their complete length and consequently distorting the surface of member 17.

Actuation means are provided to move the member 17 to vary its position and hence to vary the camber of the blade. These actuation means comprise several sets of pistons. The main set of pistons comprises a plurality of bellows 22 which are embedded within the spine 16 and which are designed as compression springs extruded by oil pressure and formed so as to fail-safe with the member 17 in its normal position. The bellows are arranged along the radial extent of the blade and extend in a direction substantially tangential to the blade surface at the position 19, that is substantially parallel to the mean chord line of the blade. The bellows 22 are provided with pressure fluid from a pressure line 23 which extends throughout the length of the blade from a supply of fluid pressure (not shown).

Each of the bellows 22 actuates the member 17 by way of a spring link 24. In this way the free end of the member 17 may be moved over the distance of operation of the bellows 22. It will be appreciated that with the bellows 22 in their fully retracted position the member 17 forms a blade section of relatively high curvature (shown in dotted lines at 2613). In

this position the spine 16 and the member 17 abut precisely so that there is no significant discontinuity at 19.

it is required to reduce the camber of the blades the pistons 22 are actuated, pushing the member 17 into its condition of less curvature (shown at 26A). In this condition there will be a discontinuity at 19, but since this condition is in any case likely to be an emergency position, the small loss produced by this step is not of critical importance.

The bellows 22 form the main actuating means for variation of the shape of the member 17, but in order to preclude vibration and extraneous movement of the member 17 further locking means are provided which take the form of a plurality of bellows 25 extending longitudinally of the blade and inter posed in the space between the forward part of the spine 16 and the internal surface of the member 17. These bellows are connected to a plurality of supply lines 27 extending within the spine 16 to a supply (not shown) of compressed air and plastic foam. In use therefore the set of bellows 25 on one side of the spine 15 is inflated with the air foam mixture for a particular position of the member 17, thus providing a leverage on the flank of the member 17 to retain it in its required position while the plastic foam helps to damp out aerodynamic induced vibrations which might otherwise occur within the be]- lows 25. It will be appreciated that the nearest set of bellows in the diagram is inflated when the member 17 takes up its position at 268 of greatest camber while the distant set of bellows is inflated when the member is in its position 26A.

In operation both types of actuating means would be operated simultaneously, the bellows 22 controlling the rate of movement against the more compressible foam filled bellows 25. The curvatures of the member 17 at the two extremes of movement are defined by one of the two forward sides of the spine 16 and the length of the links 20,. 21. Although the curvature along the radial extent of the blade remains constant, any required twist may be incorporated by sloping of the member 17 if the axial flow permits this.

It will be appreciated that this mechanism is best suited for relatively few and thick blades which require small angular movement, thus giving spines having maximum strength and reducing the cost of the mechanism.

Various modifications to the above embodiment would be quite feasible. Thus although in the above example the leading edge of the blade has been made variable it would be possible to vary the camber of the trailing edge of the blade either along or in conjunction with the variable leading edge. Again certain parts of the actuation mechanism could be removed or replaced by alternative mechanisms. The stiffness and geometry of the attachment of the

ties

20, 21 can be designed to alter the shape of the blade.

I claim:

1. A composite variable camber airfoil-shaped blade or vane for use in a fluid flow machine, said blade or vane having two aerodynamic flank surfaces with at least one of said flank surfaces being convex and said blade or vane comprising:

a rigid spanwise spine member shaped to have at least a portion define two surfaces which respectively form at least a part of said two aerodynamic flank surfaces and one spanwise end portion of the blade or vane;

a thin flexible sheet member shaped to define the other spanwise end portion of the blade or vane and having inner surfaces and outer surfaces with the outer surfaces providing continuations of said two surfaces of said spine member and to define remaining portions of said two aerodynamic flank surfaces, said sheet member having one spanwise edge rigidly attached to one of said two surfaces of said spine member to provide a rigid connection and its other spanwise edge lying substantially flush with the otherof said two surfaces of said spine member for relative movement with respect thereto;

actuation means operatively connected adjacent to said last-mentioned spanwise edge above said sheet member for moving the same relative to said spine member in a direction of a mean chord of the blade or vane to vary camber; and

rigid means extending between said innersurfaces of said sheet member for maintaining shape of said sheet member when said actuation means is operated to vary camber 2. A blade or vane as claimed in claim 1 in which said actuation means includes a plurality of hydraulic bellows.

3. A blade or vane as claimed in claim 1 in which said rigid means includes a plurality of inextensible tie members extend ing between and fixedly attached to said inner surfaces of said sheet member.

4. A blade or vane as claimed in claim 1 in which said rigid connection is on said convex flank surface of the blade or vane.

5. A blade or vane as claimed in claim 2 and in which said hydraulic bellows comprise compression springs adapted to move said sheet member to a predetermined position should the supply of fluid to the bellows fail.

6. A blade or vane as claimed in claim 1 and comprising additional actuation means which comprise a plurality of tubular, inflatable members lodged between the spine member and the sheet member.

7. A blade or vane as claimed in claim 3 and in which said tie member comprise weakened portions adjacent to their attachment to the sheet member so that hinging is allowed at said portions.

Claims

1. A composite variable camber airfoil-shaped blade or vane for use in a fluid flow machine, said blade or vane having two aerodynamic flank surfaces with at least one of said flank surfaces being convex and said blade or vane comprising: a rigid spanwise spine member shaped to have at least a portion define two surfaces which respectively form at least a part of said two aerodynamic flank surfaces and one spanwise end portion of the blade or vane; a thin flexible sheet member shaped to define the other spanwise end portion of the blade or vane and having inner surfaces and outer surfaces with the outer surfaces providing continuations of said two surfaces of said spine member and to define remaining portions of said two aerodynamic flank surfaces, said sheet member having one spanwise edge rigidly attached to one of said two surfaces of said spine member to provide a rigid connection and its other spanwise edge lying substantially flush with the other of said two surfaces of said spine member for relative movement with respect thereto; actuation means operatively connected adjacent to said lastmentioned spanwise edge above said sheet member for moving the same relative to said spine member in a direction of a mean chord of the blade or vane to vary camber; and rigid means extending between said inner surfaces of said sheet member for maintaining shape of said sheet member when said actuation means is operated to vary camber

2. A blade or vane as claimed in claim 1 in which said actuation means includes a plurality of hydraulic bellows.

3. A blade or vane as claimed in claim 1 in which said rigid means includes a plurality of inextensible tie members extending between and fixedly attached to said inner surfaces of said sheet member.