Patent GB-1170592-A (GB)
Title: Aerofoil-Shaped Blades and Blade Assemblies, for use in a Fluid Flow Machine
Inventor: PALFREYMAN JACK
IPC: F01D5/28
Filed: 1967-08-03
Abstract: 1,170,592. Making bladed rotors. ROLLS-ROYCE Ltd. 20 Nov., 1967 [29 Nov., 1966; 12 April, 1967; 3 Aug., 1967], Nos. 53459/66, 16669/67 and 35593/67. Heading B3A. [Also in Divisions B5 and F1] A fibre-reinforced aerofoil-shaped blade for a fluid flow machine such as a turbine or compressor has a root portion with slots therein separated by tangs. The blade 20, Fig. 1, may be a rotor or stator blade for a gas turbine engine and may be made, together with its supporting structure for compressor applications, from synthetic resin material reinforced with carbon fibres or silica fibres coated with aluminium or with an epoxy resin. For turbine applications, a blade and supporting structure may be made from fibre-reinforced metals such as titanium or nickel based alloys. The fibres in this case may be carbon, boron, or silica coated with nickel, chromium, niobium, tantalum or a nickelchromium alloy. Carbon fibres may be coated with carbon. The blade 20 is formed by compacting together a series of fibre-reinforced synthetic resin sheets 21 to 26, tangs 31 in the root 30 being provided by appropriately preshaping the sheets or by machining slots 32 after the root has been formed. Alternatively, the blade may be formed by placing sheets of fibres, corresponding to sheets 21 to 26, under tension in a blade shaped mould and injecting the resin material. The fibres may be at an angle to the blade length for added strength. Blades 20 are mounted on a compressor stator or rotor, Fig. 2, formed by annular members 33 axially spaced apart by gaps 34 which receive the tangs 31 of the blades, the latter being bonded to the members 33. Plates 35, which may also have tangs (36), Fig. 3 (not shown), are bonded between adjacent blades, or alternatively synthetic resin may be injected to fill the gaps 34. The annular members 33 are of the same material as the blades and may be formed by compacting together a number of sheets (37), Fig. 4 (not shown), of the reinforced resin material or by compacting a number of turns (40), Fig. 5 (not shown) of the material in tape form. The members 33 are then cured and bonded to the blades in a mould. The members 33 may alternatively be made by filling annular slots 52 in a mould 50, Fig. 8, with the resin material, tangs 55 on the blade roots 54 being entered into slots 56 in the mould so as to be bonded to the annular members formed in slots 52 during curing. The resin material in slots 52 may instead be foamed. Figs. 6, 7 and 9 to 11 (not shown) illustrate resin blades and rotors with modified arrangements of reinforcing fibres. In a further modified rotor assembly Fig. 12, reinforced resin blades 94 whose roots 95 have tangs 96 with slots 97 therebetween are interconnected by bonding the ends of reinforced resin tapes 100 within the slots 97, the tapes forming a disc 101 after curing in a mould with the addition of further resin material. The mould may include members covered with a releasing agent which can subsequently be removed to provide cavities in the rotor for low density damping material. Fig. 13 (not shown) illustrates a rotor assembly similar to that of Fig. 12 except that the resin tapes (104) follow catenary or similar curved paths such that the centrifugal force on the fibres of each tape is offset by the radially inward load thereon. In a modification, Fig. 14 (not shown), the resin tapes (105) follow straight paths and annular members (106) similar to members 33 of Fig. 2 are provided. In further modifications, Figs. 15, 16 (not shown), the tapes (116) follow curved or straight paths to a central hub member (115). In Fig. 17, a fibre-reinforced blade 118 is brazed, welded or resin bonded, according to material, to a rotor 122 built up from spaced annular members 123. For compressor applications the blade 118 may be solid, but for turbine use cooling passages such as 124 are provided and supplied with air from the rotor interior. In the latter case radial vanes (160), Fig. 21 (not shown), may be provided in the spaces between the members 123 to effect additional compression of the cooling air. Figs. 18 to 20 (not shown) illustrate similar rotors in which for turbine use the blades and rotors are made from a nickel-chromium matrix reinforced with nickel-chromium plated carbon fibres. In Fig. 22, a rotor 162 is produced by winding fibres helically on a tapered former so that the fibres extend in the direction of the principal tensile stresses which would result from torsional loading of the rotor. The fibres are coated during winding with a resin or metal, according to application. The metal may be applied in an electrolytic process, sprayed or vapour deposited. Additional circumferential and axial fibres 164, 170, 171 reinforce the helically wound fibres 166, 167. Releasable pegs (165), Fig. 23 (not shown), are inserted in the former prior to winding the fibres so as to provide mounting holes for the tangs on the roots of the blades 163. Figs. 24 to 26 (not shown) illustrate the arrangement of fibres in further multi-stage rotors.