US2628065A - Turbine disk - Google Patents

Description

1953 A. A. LOMBARD ETAL 2,628,065

TURBINE DISK Original Filed 001' 2, 1947 2 SHEETSSHEET 1 2 29 "'hw m. M

Ill."

A. A. 404154 EN. n. M02167 0. A. 04 ms,

Feb. 10, 1953 A. A. LOMBARD ,ET AL 2,628,065

TURBINE DISK Original Filed Oct. 2, 1947 2 SHEETS-SHEET 2 4. 4. 100M460, 19M N. 4402465 Patented Feb. 10, 1953 TURBINE DISK Adrian Albert Lombard, Allestree, Frederick William Walton Morley, Aston-on-Trent, Christopher Ainsworth Davis, Barrow-on-Soak, near Loughborough, and Stanley Clarke Wilkinson, Colne, England, assignors to Rolls-Royce Limited, Derby, England, a British company Original application October 2, 1947, Serial No.

777,506. Divided and this application December 19, 1950, Serial No. 201,644. In Great Britain October 2, 1946 3 Claims.

This application is divided out of our copending application serial No. 777,506 filed October 2,

This invention relates to gas-turbines and more particularly to turbine-disc-assemblies of the kind in which the turbine-disc comprises two complementary parts spaced axially and supporting peripherally the turbine-blading therebetween. In such constructions it has been proposed to provide a space between two parts of the disc forming a passag for air cooling the disc and blades and/or their fixing.

In gas-turbine engines for aircraft-propulsion, to which the invention is particularly though not exclusively applicable, it has been the practice to manufacture turbine-discs from solid forgings, which in order to accommodate for high centrifugal loading and to avoid vibration or whip,

.have been of relatively thick section. In addition, owing to the elevated temperature at the blade-root cooling efliciency.

The nature of the invention will be appreciated by reference to the following description of a preferred embodiment illustrated in the accompanying drawings, in which:

Figure 1 is a local radial section through a I turbine disc,

Figure 2 is a partial end view of Figure 1 with parts broken away.

Referring to Figures 1 and 2, there is illustrated an axial flow turbine assembly comprising two slightly dished disc parts with the turbine blading mounted in a blade-supporting ring received between the peripheral portions of the discs.

The two disc parts II), II are generally similar to one another, decrease in thickness from their centres towards their peripheries to economise in material and are assembled with the concave faces together. The disc material may be a high tensile steel, such as that known under the trademark Hykro, having the desired properties at the moderate temperature at which it runs.

The disc part is provided with a mounting flange l2 at its outer side by means of which the disc can be secured to a turbine-rotor shaft.

Each disc is formed with an internal axial flange It at about the same radius as the mounting flange l2, and the flanges l3 abut one another to space the two disc parts In, I l the correct distance apart at their centres. One of the flanges is arranged to fit, in the manner of a spigot, within the other so as to resist centrifugal and gyroscopic forces, and thermal loading tending to cause relative radial displacement between the disc-parts.

Each disc part is formed with a central hole to receive a sleeve [4 and the two disc parts are clamped together at their centres between a flange IE on the sleeve I4 and a nut 16 on the sleeve. The sleeve I4 is open at one end to the shaft and is closed at the other so that cooling air can pass from the shaft into the sleeve and then through openings ll in the sleeve l4 and flanges l3 into the turbine disc.

Each disc part I0, H is formed with an internal shoulder l8 near its periphery and these shoulders face radially inwards so as to form sockets of large diameter. Immediately outside the shoulder I8 the disc parts are formed with two sets of annular facings I9 between which the blade supporting ring 20 is located. The material of this ring may be that known as G.18.b (manufacturer's specification or trade-mark), having the desired properties at the elevated temperature to which the ring is subjected. The ring 20 is formed with-two outwardly facing shoulders 2| which constitute large diameter spigots fitting in the sockets formed by the shoulders IS. The disc parts are secured towards their peripheries against moving apart axially by counter-sunk bolts which are arranged in a circle along the centre-line of the facings l9 and are thus in a portion of the disc which is subject to a considerably reduced centrifugal loading, the centrifugal loading due to the blades 23 and blade supporting ring 20 being applied to the disc through the engaging shoulders I8, 2 I.

The peripheral portions of the disc parts 10, II beyond the facings [Bf-are shaped to provide between them a wide trough 24 and the blade-supporting ring 20 extends radially outwards beyond the trough, the part of the ring 20 beyond the trough 24 being widened to close the trough. There is, however, a space inside the trough on either side of the blade-supporting ring 20.

The facings l9 are formed with a plurality of radial slots 25 extending across them and also with arcuate slots 26 joining pairs of slots 25. The shoulders 2| on the ring 20 are also formed with radial slots 21 to register with the slots 25.

The cooling air can thus pass into the trough 24 through the passages provided by these slots and will adequately cool the periphery of the disc parts III, II and the in'n'er'part of the blade-supporting ring 20.

The peripheral part of the ring is formed with shaped recesses 29 to receive and retain the roots 28 of the blades 23, the roots being conveniently provided with peripherally extending shoulders so that they are of the fir-tree type which are mounted in the blade-carrying ring by being slid into itin an axial direction. Slots 30 are cut across the bottom of the recesses 29 so that cooling air can escape from one side of the trough 24 underneath the roots 28 of the blades. In certain cases the blades 23 may be hollow and part of the air will then pass up through the blades to cool them. Passages 31 are formed in the portions of the ring 2 3 between the blade roots 28 to permit the escape .ofcooling air from the trough 24 and to assist in cooling the blade roots.

Each of the disc parts Hi, It is provided with .an axial flange 32 on its inner surface at a short distance inwards from the blade supporting ring 20 and these flanges abut one another when the discs are assembled. Slots 33 are formed in the flanges 32 to register and form passages for the outward flow of cooling air. The flanges 32 interabut to determine the spacing of the discs l6 flanges 35 provide inwardly facing shoulders a forming sockets to receive a ring 35 which acts as a spigot in each of them. The ring 35 is preferably formed from a material, having a high coefllcient of expansion, such as aluminium, so that it will tend to tighten in the sockets as the temperature rises. The ring 35 is formed with slot 38 on each of its side faces to provide passages through which cooling air can pass outwards and each slot 35 is made deeper at its outer end in order to clear the flanges 34. This arrangement has the result that the air will tend to flow outwardly along the inner faces of the discs W, H to the slots 36 and will escape from these slots towards the central plane of the turbine-disc-assembly so that the two streams of air flowing on the opposite sides ofv the ring 35 will be directed towards the central plane of the turbinedisc and towards one another to produce turbulence. This turbulence reduces the tendency for a Stratified air flow in which the air flowing over the parts of the disc will be hotter than that flowing up the central plane of the disc.

' The spigot-like couplings between the bladesupporting ring 29 and each of the disc parts iii, ll, between the ring 35 and the disc parts it,

H, and between the axial flanges l3 serve to resist centrifugahgyroscopic or thermal loading which tend to make the disc parts move relatively to one another in a radial direction.

The clamp device at the centre of the turbine disc assembly provided by sleeve i i, flanges i5 and nut 15, avoids the use of a series of bolts passing through the disc parts, and localizes the bore through the centre of the disc, thereby avoiding undue reduction in structural strength. Likewise, it will be appreciated that the provision of the flange l2 avoids the passage of bolts through the disc-parts in their attachment to the turbine shaft.

The disc parts l0, vll being coned will tend to separate under centrifugal force at full speed. The-bolts 22 are tightened up so that the axial load between the flanges on the disc parts and between the disc parts and the ring 35 are greater than the maximum force tending to separate the disc parts when running at maximum speed.

It will be appreciated that the construction of turbine disc above described is light in weight and yet is capable of withstanding the high stresses experienced when in use, is relatively simple to manufacture, and, by virtue of the method of blade-root fixing, has an improved cooling efiiciency as regards the blade-root cool- Moreover, by locating the screws, bolts or rivets for securing the disc together outside the region of the part of their peripheries subjected to high centrifugal stresses, the discs are not unduly weakened by the provision of the holes to receive the bolts, screws or rivets.

Furthermore, the construction of turbine disc of this invention enables the various parts of the disc to be manufactured from a material having the desired strength properties at the temperature at which it will operate. Thus the dished discs may be formed from a material having desired strength properties at a temperature which is moderate as compared with that at which the biading or the blade-supporting ring will operate and the blading or blade-supporting ring will be made from a material having desired strength properties at a more elevated temperature.

We claim:

1. An axial flow turbine assembly, comprising in combination a first disc part having means for securing it to a hollow rotor shaft; a second disc part mounted coaxially with the first and axially spaced therefrom to provide a hollow space therebetween; a duct leading to said space for the supply of coolinggas; shoulder means on said disc parts adjacent the peripheries thereof and extending axially towards one another; an annular blade supporting ring mounted in said space and provided with axially extending circumferential spigot means abutting the radially inward faces of said axially extending shoulder means on said disc parts; axial flow turbine blading supported by said blade supporting ring; securing members to secure said disc parts against axial separation extending through the disc parts, and through said ring and located at a radius outside said spigot means; and passages in said axially extending shoulder means and said axially extending circumferential spigot means communicating between said space and the exterior of the disc assembly to permit the flow of cooling gas from said space, such flow cooling the ring and peripheral portions of the discs by direct contact therewith.

2. An axial flow turbine assembly, comprising in combination two complementary disc parts secured to each other and axially spaced to provide a hollow space therebetween means for supplying cooling gas to said space; axial abutment means on said disc parts defining said axial spacing at an inner radius; shoulder means on said disc parts at a radius outside said abutment means and extending axially towards one another; an annular blade supporting ring provided with axially extending circumferential spigot means abutting the radial inward faces or" said axially extending shoulder means; axial flow turbine blading supported by said blade supporting ring; securing members to secure said discs against axial separation extending through said disc parts an through said ring and located at a radius outside said spigot means; circumferential shoulder means on said disc parts extending axially towards each other into said space and located at radius between said first mentioned shoulder means and said abutment means defining the axial spacing of the disc parts at inner radius; a spacer ring in said space engaged in axial abutment by said disc parts and dimensioned to engage in radial outward abutment with said circumferential shoulders; passages formed in said ring to permit passage of cooling gas radially outward through said ring; and passages in said first mentioned shoulder means and said axially extending circumferential spigot means communicating between said space and the exterior of the assembly to permit the flow of cooling gas from said space, such flow cooling the ring and peripheral portions of the discs by direct contact therewith.

3. An axial flow turbine disc assembly, comprising in combination a first disc part; a second disc part mounted coaxially with said first disc part, said first and second disc parts having coaxial bores; a hollow bolt member extending through said bores; a nut member engaged on said bolt member; spacing means axially nipped between said discs by said bolt and nut members and holding said discs apart to provide a hollow space therebetween radially outside said spacing means; a communicating duct from said coaxial bores to said space, said communicating duct passing through said bolt; shoulder mean on said disc parts adjacent the peripheries thereof and extending axially towards one another; an annular blade supporting ring provided with axially extending circumferential spigot means abutting radially inward faces of said axially extending shoulder means on said disc parts; axial flow turbine blading supported by said blade supporting ring; securing members to secure said disc parts against axial separation extending through said disc parts and through said ring and located at a radius outside said spigot means; and passages in said axially extending shoulder means and said axially extending circumferential spigot means communicating between said space and the exterior of the disc assembly to permit the how of cooling gas from said space, such flow cooling the ring and peripheral portions of the discs by direct contact therewith.

ADRIAN ALBERT LOMBARD.

FREDERICK WILLIAM WALTON MORLEY.

CHRISTOPHER AINSWORTH DAVIS.

STANLEY CLARKE WILKINSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 841,503 Gelpke Jan. 15, 1907 1,959,220 Robinson May 15, 1934 2,401,826 Halford June 11, 1946 FOREIGN PATENTS Number Country Date 452,412 Great Britain 1936

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