Patent Application
20160024947
The disclosure relates to turbofan engines. More particularly, the disclosure relates to fan blade mounting.
An exemplary turbofan engine includes one or more blade stages driven directly or indirectly by a low pressure turbine (LPT) of the engine. In an exemplary blade stage, the circumferential array of blades are mounted to a disk or other hub structure. Exemplary blades include a dovetail attachment root which is received in a dovetail slot in the hub. The exemplary slot and root have a base and have a first side and a second side extending radially outward from the base and generally converging toward the outer diameter (OD) perimeter of the hub. There may a rounded interface between the slot and the hub (OD) surface. The slots may be longitudinal or off-longitudinal at an acute angle and may be straight or have a curvature.
Exemplary blades comprise at least a substrate formed of a titanium alloy, an aluminum alloy, a composite or combination. Exemplary hubs are of titanium alloy or aluminum alloy. Portions of the blades may bear coatings for one or more purposes (e.g., corrosion protection, erosion protection, foreign object damage, or even abrasive coatings at blade tips). To protect the interface between the root and the slot, it is known to use wear pads along the sides of the root. The exemplary wear pads are formed of sheet stock of non-metallic material (e.g., polymeric fabric or other fabric material). Exemplary fabric material is VESPEL ASB polyimide, E. I. du Pont de Nemours and Company, Wilmington, Del.
One aspect of the disclosure involves a blade assembly comprising a blade and one or more wear pads. The blade has an airfoil having a leading edge, a trailing edge, a pressure side, a suction side, and extending from an inboard end to a tip. The blade further includes an attachment root. The one or more wear pads are along the attachment root. The one or more wear pads have a plurality of slits.
In additional or alternative embodiments of any of the foregoing embodiments, the one or more wear pads may comprise a first wear pad along a first side of the attachment root and a second wear pad along a second side of the attachment root opposite the first side.
In additional or alternative embodiments of any of the foregoing embodiments, the blade comprises an aluminum alloy or titanium alloy substrate.
In additional or alternative embodiments of any of the foregoing embodiments, the wear pad comprises a fabric.
In additional or alternative embodiments of any of the foregoing embodiments, the wear pad comprises polyimide fiber.
In additional or alternative embodiments of any of the foregoing embodiments, the wear pads are adhered to the attachment root.
In additional or alternative embodiments of any of the foregoing embodiments, the plurality of slits include a plurality of radially outwardly directed slits opening to an outboard edge of the associated pad.
In additional or alternative embodiments of any of the foregoing embodiments: the slits include a plurality of slits opening along an end portion of the pad along at least one of a leading end or a trailing end of the attachment root.
In additional or alternative embodiments of any of the foregoing embodiments, the attachment root is a dovetail root.
Another aspect of the disclosure involves a gas turbine engine comprising a fan hub having a plurality of slots and a plurality of the blade assemblies of with the attachment roots accommodated in associated said slots.
In additional or alternative embodiments of any of the foregoing embodiments, a method for manufacturing the blade comprises: cutting the pads from pad material, including cutting the slits; and applying the pads to the attachment root, the applying at least one of contracting the slits and expanding the slits.
In additional or alternative embodiments of any of the foregoing embodiments, the applying contracts slits along one side of the root and expands the slits along the other side.
The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
Like reference numbers and designations in the various drawings indicate like elements.
The root 124 has an inboard end or underside 134 and first and second lateral sides 136 and 138. These extend between a forward or leading face 140 and a rear or trailing face 142 (
The slot similarly to the root includes a base 160 and first and second sides 162 and 164. The roots and slots are dimensioned to be closely laterally accommodated with sufficient gap to contain wear pads 170 and 172. Each wear pad extends from an inboard edge 174, 176 to an outboard edge 178, 180 and from a leading end 182, 184 to a trailing end 186, 188. The wear pads are secured in place to the root by an adhesive (e.g., an epoxy such as a paste epoxy).
Each wear pad further includes an inboard face against the root and an outboard face away from the root. A portion of the outboard face contacts the adjacent slot side. End portions of the wear pads may wrap around one or both ends of the root. In the illustrated embodiment, end portions wrap around only the trailing end 142 (
The exemplary pad 170 outboard portion 224 is segmented into three sections; whereas the outboard section 226 of the pad 172 is segmented into four. When the pad 170 is installed, the cuts 228 form slots that open slightly. This opening helps maintain smoothness of the inboard portion 220. Similarly, the cuts 230 form slots that close slightly upon installation, also allowing for smoothness of the inboard portion 222.
Other implementations may alternatively or additionally segment slots along the pad inboard edge (which may fall along or near the root inboard end).
The fore-to-aft arcuate shape of the exemplary dovetail (associated with the corresponding general convexity of the blade suction side and concavity of the blade pressure side) combines with the inboard-to outboard curvature of the dovetail to create a doubly curved surface. The slits help accommodate this curvature as an alternative to possible rumpling of a flat unslitted sheet or the greater expense of molding the double curvature into a sheet-formed product. This allows use of simple flat sheetstock to be directly applied to the blade root.
The trailing edge tabs are also segmented from each other by associated cuts 242 (e.g., straight linear cuts) so that the cuts may form slots that open upon wrapping the tabs around the trailing edge.
In an exemplary sequence of manufacture, the blade is manufactured by conventional techniques (e.g., machining of aluminum or titanium or various composite formation techniques). The pads are cut from larger sheet stock material. Adhesive may be pre-applied to the stock material prior to cutting or may be post-applied. An exemplary cutting involves die cutting. An exemplary adhesive application is a post-cutting application comprising die cutting. The epoxy is then applied (e.g., by brush to an exemplary 0.004 inch (0.1 mm), more broadly 0.025 mm-0.2 mm)). The exemplary material thickness between faces is 0.012 inch (0.3 mm), more broadly 0.1 mm-0.6 mm, more narrowly, 0.2 mm-0.4 mm.
The use of “first”, “second”, and the like in the following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as “first” (or the like) does not preclude such “first” element from identifying an element that is referred to as “second” (or the like) in another claim or in the description.
Where a measure is given in English units followed by a parenthetical containing SI or other units, the parenthetical's units are a conversion and should not imply a degree of precision not found in the English units.
One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing basic blade configuration, details of such configuration or its associated engine may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.
Benefit is claimed of U.S. Patent Application Ser. No. 61/780,293, filed Mar. 13, 2013, and entitled “Blade Wear Pads and Manufacture Methods”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/076772 | 12/20/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61780293 | Mar 2013 | US |
