GB2059819A - Manufacture of axial compressor rotor - Google Patents

Abstract

A light weight multi-stage axial compressor rotor is made from a plurality of rotor rings 32 each having a rim 37 with bondable end surfaces 38, 40 thereon and external load application flanges 34, 36. The bondable end surfaces of adjacent rims are aligned against one another and an axial load applied on the flanges to force the bondable end surfaces into intimate contact. The joint surfaces are heated in an inert atmosphere to produce an oxidation-free diffusion-bonded metal joint between the bondable end surfaces. The external load application flanges are subsequently removed to obtain a minimal rim depth throughout the longitudinal dimension of the rotor so as to reduce its inertia and so improve its acceleration response during engine operation. <IMAGE>

Description

SPECIFICATION Method for manufacturing lightweight multistage axial compressor rotors This invention relates to axial flow compressor rotors and more particularly to a method of manufacturing lightweight multi-stage compressor rotors of low inertia.

At present compressor rotor drum rings are electronic beam-welded together so as to form a multi-stage compressor rotor for use in gas turbine engines. Use of such electronic beamwelding methods requires large holes in webs on each of the rotor drum rings for insertion of machine tools to remove roughened surfaces formed internally of the rings during the manufacture of electron beam-welded joints therebetween. Such access holes require reinforcement and, as a result, the rotor drum assembly has weight added thereto that unnecessarily increases its moment of inertia, which can reduce engine acceleration response time.

The present invention is an improved method of manufacturing multistage compressor rotors having a plurality of ring segments therein joined together to form the rotor drum, which method includes the steps of diffusion bonding each of the adjacent rings together to eliminate roughened internal surface configurations requiring finish machining following ring segment connection into an assembled rotor drum.

In a preferred embodiment of the present invention, the method comprises locating bondable end surfaces of each of the drum rings in alignment with one another and clamping the rings to apply a diffusion bond pressure and temperature to the joints, preformed, externally located, peripherally formed, load application flange portions on the rings being utilized to apply the load to the end surfaces for diffusion bonding therebetween; the load application flanges being subsequently removed by machining from outside of the assembled drum to produce a resultant rotor drum having a reduced moment of inertia, thereby to improve its acceleration response time.

In this preferred embodiment of the present invention, the method for producing the joint between a plurality of rotor drum rings at bondable end surfaces thereon includes applying a localized pressure to the end surfaces under a vacuum or inert gas atmosphere at an elevated temperature range for metal diffusion bonding, the localized pressure being generated by applying a load adjacent pairs of externally located load application flanges on each of the rotor drum rings so as to localize the end surface loadings thereon and thus to minimize the amount of creep deformation occurring in the rings during the diffusion bonding operation, thereby to maintain accurate axial spacing of internal web portions of the joined rings.

Preferably each of the compressor rotor drum rings has each external load application flange thereon undercut to define bondable end surfaces on the rim of the rotor drum ring at a point radially inwardly and axially outboard of the load application flange.

The invention and how it may be performed are hereinafter particularly described with reference to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown, in which: Figure 1 is a fragmentaty view, partly in elevation and partly sectioned, of a multistage axial compressor rotor constructed in accordance with the present invention Figure 2 is a cross-sectional view taken along the line 2-2 of Fig. 1 looking in the direction of the arrows; Figure 3 is a flow chart of method steps in accordance with the method of manufacture of the present invention; Figure 4 is a fragmentary sectional view of a segment of a rotor drum including load application flanges and bondable end surfaces thereon;; Figure 5 is a fragmentary sectional view showing bondable end surfaces and load bearing flanges of adjacent ones of the drums as shown in Fig. 4 aligned with one another; Figure 6 is a fragmentary sectional view of fixtures for applying a load and diffusion bond temperature on the loading flanges to press together the bondable end surfaces of the aligned parts of Fig. 5; Figure 7 is a fragmentary sectional view of the rotor drum following diffusion bonding of the end surfaces thereon and external machining of the load applying flanges therefrom; Figure 8 is a fragmentary sectional view of a second form of fixture usable in a load applying step of the present invention; and Figure 9 is a fragmentary sectional view of a third form of fixture usable in a load applying step in accordance with the present invention.

Referring now to Fig. 1, a multi-stage axial compressor rotor drum assembly 10 is illustrated that is manufactured by the method of the present invention.

In the illustrated arrangement, the assembly 10 is part of a compressor 12 having an outer case 14 and a plurality of rows of stator blades 16 associated therewith. Intermediate each of the rows of stator blades 16 are a plurality of rotor blade stages 18 each including a plurality of circumferentially spaced airfoil shaped blades 20 having root segments 22 thereon connected by pins 24 to pairs of connector flanges 26 on each of a plurality of individual rotor drum rings 28 that are connected together in accordance with the present invention to form rotor drum assembly 10 with reduced inertia so as to improve the acceleration response of the compressor rotor drum assembly 10 during engine operation.

In the illustrated arrangement the means of connection of each of the airfoil shaped blades 20 to the rotor drum assembly 10 are merely representative of one of many forms of connection of blades to rotor drums found in multi-stage axial compressor assemblies. For example, the blades can have dovetailed roots seated in dovetail shape grooves in a rim portion of the rotor drum.

As seen in Figs. 3 and 4, the method of the present invention includes the preformation of a number of flanged, metal rotor drum rings 32, each of which has load application flanges 34, 36 on opposite ends thereof located on its outer peripheral surface 37. Each of the load application flanges 34, 36 extends radially from surface 37 which is undercut to define bondable end load surfaces 38, 40 on opposite ends of each of the rotor drum rings 32. Surfaces 38, 40 thus constitute connection surfaces of continuous annular form for bonding rings together in accordance with the present invention.

The preformed rotor drum rings 32 include the flanges 26 for fastening the rotor drum ring 32 to associated blade components of a rotor blade stage of the type shown in Figs. 1 and 2.

The next step in practicing the method of the present invention is to stack and align preformed rotor drum rings 32 together as shown in Fig. 5 so as to locate outer peripheral edges 42, 44 on oppositely aligned load application flanges 34, 36 thereof. Bondable end surfaces 38, 40 of the aligned rotor drum rings 32 are thereby located in juxtaposed relationship as best shown in Fig. 6.

The load application flanges 34, 36 are then mechanically loaded by a suitable mechanical fixture representatively shown in Fig.

6 as including annular load clamps 46, 48 each having dependent legs 5.0, 52 located on side surfaces 54, 56 of the load application flanges 34, 36 which are joined together and aligned as shown in Fig. 5. The dependent legs 50, 52 are held together by means of clamp bolts 58 circumferentially spaced around flanges 46, 48. One such bolt is shown in Fig. 6 directed through aligned bores 60, 62 formed respectively in the load application flanges 34 and 36 and the dependent legs 50, 52. The fixture produces a local loading of the joint so as to hold the bondable end surfaces 38, 40 together under a mechanical load that produces surface bonding pressure in the order of thousands of pounds per square inch for diffusion bonding.The clamped parts are further located in an inert environment such as a vacuum chamber 61 or in an inert gas environment such as argon, and raised to a diffusion bonding temperature for the metal surfaces to be joined together.

Heater 63 maintains the diffusion bonding temperature for a time period sufficient to produce a diffusion of metal between surfaces 38, 40. An annular metal bond joint 64 is formed continuously around the outer periphery of the aligned rotor drum rings 32 as shown in Fig. 6.

Following local bonding and diffusion migration of the metal at the bondable end surfaces 38, 40 the load applying fixture load clamps 46, 48 are removed and then the load application flanges 34, 36 are machined from the joined parts to produce a resultant thin section rim 66 formed continuously between adjacent ones of the rotor drum rings 32 as shown in Fig. 7. There are no reinforced holes in rotor web members 68 as shown in Fig. 7 and as a result the rotor manufactured by the present invention has a reduced moment of inertia and improved acceleration response characteristics.

In the bolt fixture system shown in Fig. 6, the bolts 58 are torqued to apply the pressure on the bondable end surfaces 38, 40. The tooling and bolt material selections are based on the coefficient of expansion values of the material being bonded together so as to maintain high unit loads during maintenance of the parts at the diffusion bonding temperature.

In the embodiment shown in Fig. 8, the clamping bolts 58 are replaced by stainless steel air bags 70 interposed between a Ushaped clamp member 72 and the load application flanges 34, 36 to maintain a pressure on the bondable end surfaces 38, 40 during the bonding process. The load can also be applied by use of an external press. The above methods maintain an application of load that is localized to the end surfaces 38, 40 so as to minimize creep deformation in the parts that are pressure loaded during the diffusion bonding cycle.Such localized loading thus helps to maintain an accurate spacing of the disc shaped webs 68 so that they can be preformed to substantially their final shape thereby only requiring minor reductions in their final configuration which can be accomplished by chemical milling or other methods to remove contaminated surface layers therefrom.

Localization of the bonding pressure can also be obtained by use of a fixture configured as shown in Fig. 9 which loads intermediate load application flanges 74 to hold bonding end surfaces 76, 78 together on adjacent rotor drum rings 80, 82. In this arrangement a loading clamp 84 bridges the two parts to be joined and includes an end plate 86 bolted to an elongated L-shaped bridging plate 88 connected together by means of a load applying bolt system 89. Such an arrangement enables a localized heater 90 to be arranged immediately the adjacent end surfaces 78, 76 thereby to maintain the total tool environment at lower temperatures while maintaining the joint to be bonded at an elevated temperature suitable for diffusion bonding.The rotor drums and tools thus can be held closer to predetermined temperatures and the material of the tooling components can be of a material less susceptible to excessive process temperatures.

The use of the bonding technique with rotor drum rings made of high temperature cast alloys, such as the nickel-chromium-cobalttungsten alloy sold under the trade name of Mar-M247, can be accomplished under an inert environment such as vacuum or argon gas at elevated temperature levels of 2225 F (1219 C) and diffusion bonding pressures of 15,000 psi (103,421 kPa) for time periods in the order of three hours with the rings being maintained under pressure to produce a diffusion bonded joint.Another example of rotor drum rings joined by the method of the present invention is rotor drum rings made of the titanium-aluminium-vanadium alloy sold under the trade name of Ti-6-4 titanium, bonded together under vacuum or at an argon atmosphere of approximately 1 6OO'F to 1 700'F (871 C-927~C) at a pressure loading of 15,000 psi (103,421 kPa) for one to two hours.

By use of the present invention the need for subsequent clean-up and removal of interiorly located rough back-side weld splatter from the completed multi-stage compressor rotor is eliminated. Thus, access for machine tooling into the interior of web-shaped discs such as discs 68 in the illustrated arrangement can be eliminated. The preformed load applying flanges of the present method are easily removed from the exterior of the rotor to produce a desired thin-sectioned rim in the rotor assembly having the desired acceleration response characteristics.

Claims (6)

1. A method for manufacturing a light weight multi-stage axial compressor rotor drum assembly for a gas turbine engine comprising the steps of: preforming a plurality of rotor drum rings each having a rim with bondable end surfaces thereon, stacking said rotor dum rings together so that said bondable end surfaces of adjacent rotor drum rings are aligned in contact with one another, applying an axial load on said stacked rings to force the respective end surfaces into intimate pressure loaded contact with one another while simultaneously maintaining an inert environment on the pressure loaded end surfaces, and applying sufficient heat energy to the loaded end surfaces to maintain them at temperatures sufficient to produce metal diffusion between the loaded end surfaces so as to produce a metal diffusion bonded joint therebetween, thereby to maintain a minimal rim weight throughout said axial compressor rotor drum assembly at connector joints formed between the rings therebetween so as to reduce inertia in said assembly to improve acceleration response of the assembly, when subsequently mounted in a gas turbine engine, during engine operation.

2. A method for manufacturing a light weight multi-stage axial compressor rotor for a gas turbine engine according to claim 1, in which each rotor drum ring has radially outwardly extending load application flanges on the exterior thereof, the axial load on said stacked rings is applied across adjacent pairs of the load application flanges to force the respective end surfaces into intimate pressure loaded contact with one another and, after production of said metal diffusion bonded joint, the load application flanges are removed from the exteriors of the rotor drum rings.

3. A method for manufacturing a light weight multi-stage axial compressor rotor for a gas turbine engine according to claim 2, in which the axial load on said stacked rings is applied by clamping fixtures secured across said adjacent pairs of load application flanges, said clamping fixtures being removed prior to the removal of the load application flanges.

4. A method for manufacturing a light weight multi-stage axial compressor rotor for a gas turbine engine substantially as hereinbefore particularly described and as shown in Figs. 1 to 7 of the accompanying drawings.

5. A method for manufacturing a light weight multi-stage axial compressor rotor for a gas turbine engine substantially as hereinbefore particularly described and as shown in Figs. 1 to 5, 7 and 8.

6. A method for manufacturing a light weight multi-stage axial compressor rotor for a gas turbine engine substantially as hereinbefore particularly described and as shown in Figs. 1 to 5, 7 and 9.