US2613058A - Cooled bladed rotor - Google Patents

Description

Oct. 7, 1952 J. ATKINSON 2,613,053

COOLED BLADED ROTOR Filed Nov. 19, 1946 4 Sheets-$heetjjl Fig.l

Fig.2!) Fig.3 Fig.4 Fig.5

Invenfor Oct. 7, 1952 J. ATKINSON COOLED BLADED ROTOR Filed Nov. 19, 1946 4 Sheets-$heet 4 0 O Q N .9

LL- (0 v N D 2 Inventor Patented Oct. 7, 19 52 oooLsp BLADED Boron Joseph Atkinson, London, England 1 H Application Novemberis, 1946, Serial No, 710,764 L j In Great Britain November .30, "1945 f H This invention relates to the construction and manufacture of bladed elements of turbines and compressors. Whilst, as will be appreciated from the description which follows, the inventlon is capable of application both to the rotors and stators of such machines, and the expression bladed element is accordingly intended to in clude both rotors and stators, the invention offers probably its maximum utility and advantage when used'in relation to turbine rotors, and more particularly rotors of combustion turbines,

the requirements ofwhich it was, in fact, de

signed to meet. i i

It is'usual practice for the rotor of a combus tion or other turbine to be made from one or more substantial one-piece forgings or similar,

bodies, but this method of manufacture has a number of disadvantages, including the fact that a one-piece rotor element is expensive in first cost and that a local flaw may involve total scrapping of the element, possibly only after considerable expense has been incurred in preliminary machining operations. one-piece element is liable to certain mechanical limitations, including non-uniformity of structure and directional sensitivity to operating stresses, whilst its material may be of relatively low" tensile strength and subject to loss of elasticity under the high duty conditions of temperature and stress involved, resulting in a tendency of the rotor to growth during use. Onepiece rotor elements of the conventional type also involve expensive machining processe since every finished part has to be machined from the solid, and thus do notlend themselves to mass production. Similarly, due to machining difficulties, they do not lend themselves readily to the provision of internal cooling passages.

It is an objectof the present invention to eliminate or mitigate some or all of these disadvantages. 1

The invention is based on the conception of employing a laminar construction in the manufacture of thebladed elements of turbines and compressors, especially the rotors of combustion turbines, and in one of its aspectsprovides such an element which comprises a multiplicity of metal laminae held together as a pack having separately fabricated blading mounted thereon.

According further to the invention a blade carrier element for use in the construction of a bladed element as just defined comprises a multiplicity of metal laminae held together asa pack a 2 Claims. (01. 253 39.15)

used herein is intended to indicatemetal which is suflicientlythin to be'susceptible of localshaping bypressing, stamping or similar operations.

According to a further important practical feature 'of the invention, the sheet material used forthe rotor of a combustion turbine is of a kind which has had its mechanical properties improved by a cold rolling or other pressure working process; thus, for example, the sheets may be made of an austenitic heat-resisting alloy, a characteristic of which is that after cold rolling itless readily loses its elasticity at high temperatures and that its tensile strength is improved.

The technique of using thin sheet materia lends itself well to the cheap formationof blade seatings by, in accordance with another feature of the invention, suitably stamping out portions In addition a and having formations which aremutually complementary so as to provideseatings for blades to be mounted thereon.

In order to obtain the maximum advantage from the invention, particularly ineliminating orminimising the effect of local flaws in the blade carrier element and in facilitating mass production, the laminae are made of thin sheet metal which, ifthe element is a rotor for, a,

combustion turbine, is preferably of a heatresisting alloy. The expression sheet metal mitted from the blades.

of the peripheries of the individual laminae according to the form of seat desired, but if necessary these seatings may be finished by machining operations after the laminae have been assembled to form a carrier element. Various examples of seating forms will be given below preferably, however, the anchorages provided for the blades are such as to distributeamong the laminae the centrifugal stresses trans- For a similar purpose the laminae may be held together by bolts or the like passing completely therethrough so as to ensure reasonable stress distribution as between the individual laminae.

In another aspect of the invention a bladed (or a blade carrier) element of a turbine or compressor comprises a multiplicity of metal laminae held together as a pack, and a space is afiorded between adjacent laminae to provide a passage for the circulation of a cooling medium, which will normally be air. passage is afforded by the co-operation of complementary formations of adjacent laminae, the' latter, for example, having apertures arranged in overlapping register so as to form a continuous passage following a desired path without unduly weakening any one lamina.

is required may be obtained by ribbing or otherwise deforming one or more laminae.

.In order that the invention may be clearly understood and readily carried into efiect it will now be more fully described with reference to the examples of construction illustrated in the accompanying drawings, from which further features will appear, and in which:

\ Figure l is a partly sectional side elevation of a simple form of rotor formed by a laminated pack in accordance with the invention;

Figure 2a is a fragmentary face view of the rotor illustrated in Figure 1, illustrating one,

form of root seating;

Figure 2b is a fragmentary face view of the,

rotor of Figure 1, illustrating another form, of rotorseating; l Figure 8 is a fragmentary sectional side ele- Preferably this cooling Alternatively, the spacing of laminae between which the passage Figures 4 and 5 are respectively a fragmentary sectional side view and face view of a rotor having a blade mounted in an axially extending seat but having an alternative arrangement for preventing axial displacement of the blades;

Figure 6 is another fragmentary sectional side L view illustrating an alternative form of blade,

root mounting;

Figure '7 is a detail view illustrating a possible method of attaching a. balance weight to a rotor;'

Figures 8(a), (b) and (c) are views illustrating in plan, rear elevation, and transverse section on line CC on Figure 8b a form of hollow. sheet metal blade suitable for use with a rotor according to the invention, whilst Figures 8(d) and (e) Figure 12 is a face view of a rotor indicating three alternative ways of arranging the cooling passages by the methods illustrated in Figure 11;

Figure 13 is a part sectional side'view showing an arrangement for introducing cooling air at the hub of such a rotor;

Figure 14 illustrates in axial section partof an axial iiow compressor having the invention applied thereto both in the rotor and stator construction, alternative methods of blade mounting being shown, which are also illustrated in front elevation in Figures 15(50) (b) and (c) Figures 16 and 17 are detail views illustrating alternative forms of root mounting that might be employed.

The general conception on which the invention is based is illustrated in Figure 1, which shows a turbine rotor, suitable for use in a highly stressed combustion turbine assembly, comprisinga pack of sheet metal laminae I secured by'bolts 2 to theflange of a shaft 3, the bolts 2 passing through all the laminae so that each sustains a shareof the radial stress in operation. laminae are thin sheets'of a heat-resisting alloy which has had its tensile strength and elastic properties improved by a cold rolling process, a suitable alloy for the purpose being an austenitic steel alloy containing 18% chromium and 8% nickel stabilisedwith titanium.

This construction lends itself to a variety of root mountings for the blades; for example as illustrated in Figure 2a, and in Figure 3, a root 4 may be of the fir tree type commonly used in combustion turbines, this type of root and its broaching may still be used as a finishing process;

In this construction axial displacement of the Preferably the 4 blades after assembly maybe preventedjeither by peening over the ends ofthe blade roots or (see Figure 3) by providing outside laminae 5 which are not notched and thus extend across the ends of the blade root faces, or again (see Figures 4 and 5) by displacing a notched lamina '6 peripherally in relation to the remainder of the laminae 1 before securing the rotor finally, so as to enter 'agroove in the blade root.

In place of the fir tree type of root fastening, the sides of a root and seating may have complementary semicircular grooves as indicated in respect of the root I in Figure 2b, the blade being retained. against radial displacement by pins 8 fitting the holes thus formed, and against axial displacement by peening of the pins 8.

It will be appreciated that in each of the constructions just described the centrifugal load due to the blades will be distributed over. all the laminae. I

,As an alternative to axially extending root mountings, adjacent laminae I may be of diiferent radial dimensions as illustrated in Figure 6 so as to form peripheral channels at the rim of the rotor, and the blade roots have corresponding tongues 9 lying in the peripheral direction, the bladescbeinglocked in position by pins or dowels Ii] passing through aligned holes in the tongues 9- and laminae I and peenedover for axial.

retention, the arrangement thus being such that the securing pins Iii are in shear at several points but they can be enabled to do so by; pinning the.

laminae together. Alternatively the laminae of smaller diameter can be left unstressed, in which.

case they act merely as spacers and can be made of inferior material to the larger laminae. There may, of course, beseveral of the latter grouped together as shown at the right hand side of the figure.

In order to cool the blades and, if necessary, the rotor itself, the latter may be formed with coolant passages I I in the mannerindicated in Figures 9 and 10, in which successive laminae I are pierced with holes in such a way that the holes in successive laminae overlap and together form continuous passages I I extending from a radially inner point on the rotor to the blade root seatings.

It will be noted that in this instance the passages I I are arranged to emerge at one face of the rotor and the outermost lamina at that poi nt is deformed to provide a lip I2 which willact as a scoop for entraining air into the passages. It will also be noted that although'no one lamina is unduly weakened by perforations it is possible to obtain a distribution of coolant passages supplying every blade root.

In the alternative suggested cooling arrangement illustrated in Figures 11 wi it is proposed to deform individual laminae I so as to produce a spacing between themat desired points. For example, as illustrated in Figure 11(a), successive laminae have interengaging combined grooves and ribs I3 formed therein which result in a specing of adjacent laminae, whilst in Figure 11(1)),

only ribs I4 are employed and in Figure 11(c) alternate plane and grooved laminae I, I5 are provided. The deformations of the-various types suggested may be arranged, for example, in any of the three ways indicated in Figure 12, that is, radially as at I6, annularly as at I 'I, or spirally as at I8, in order to provide continuous passages from some radially inner point of the rotor to;

the periphery. In the example illustrated in Figures 12 and 13 it is assumed that the air is to be supplied from a hollow shaft 3 (see Figure 13) through appropriate ports communicating with an inner space [9 at the centre of the rotor.

A laminar construction of blade carrier element in accordance with the invention, particularly a rotor with cooling passages as in Figures 9 to 13, may be advantageously combined with a hollow sheet metal blade, an example of which is illustrated in Figure 8, in which a root 33 of corrugated form is employed, being secured in a correspondingly shaped seating by the insertion of an internal filler block 34. The latter has passages at 35 to conduct cooling air emerging from the rotor into the body 36 of the blade, which is open at its trailing edge and radially outer end for the escape of the cooling air into the working fluid flow.

A method of attaching rotor balance weights which makes use of the characteristics of laminar construction in accordance with the invention is illustrated in Figure 7, in which the weight is in the form of a headed stud 3| accommodated by perforating successive laminae l and retained by its head 32 being buried as shown. There might be several of these studs 3| annularly arranged on the rotor, and to assist balance adjustment each might be tapped to receive grub screws such as 31a of different weights, or bored to receive other forms of balance weight. Balancing might also be achieved by the provision of a bead 31 (Figure 3) from which material can be ground as required.

Although the drawings illustrate a simple form of rotor built up from plane laminae, it will be understood that some of these may be dished or otherwise centrifugally unbalanced in order to enable the centrifugal load to be utilised to maintain stability in the axial direction by reason of its straightening effect on the laminae.

In applying the inventon to stator elements, blade carrier rings 20, as illustrated in Figure 14, may be formed each from a pack of thin laminae providing at the inner periphery of the ring suit able blade retaining formations, the individual rings being supported between spacing rings 22 and the whole secured to form a rigid unit which may be mounted in an outer casing 23 or not as desired. It would be possible to construct the entire stator element as a pack or series of packs of thin sheets, but in its relation to stator elements the principal advantage offered by the invention is in adaptability to mass production, and this advantage is largely achieved if the laminar construction is confined to the blade supporting parts proper of the stator.

As indicated at 24 in Figures 14 and 15601 the blade seatings might be formed by a simple tapered recess in all except the two outermost laminae of a ring, the blade being secured by a dowel 25. Alternatively, as at 25 (Figures 14 and 15(1)) where the blade seating is again a simple tapered recess, the outermost laminae 29 are of reduced radial depth to make room for retaining rings 20a which engage axially extending projections 21 on the roots; or again the fir tree type of fixing already described may be employed as at 28 (Figures 14 and 15(0)).

In the construction illustrated in Figure 14 the compressor rotor also employs the laminar construction, but in this case again the laminar packs are used only for those parts of the rotor actually required to support blades, the individual packs forming rings 29 separated by spacers 39.

In any of the cases described in the foregoing which employ axially directed blade seatings, the seating could be skewed in the manner indicated in Figure 16(1)), this formation being attained quite simply by relative peripheral displacement of adjacent laminae l and, if necessary, machining the inner faces of the seatings to remove the small steps thus produced. A further alternative form of seating, suitable for rotor or stator elements, is illustrated in Figure 17, and is of dovetail form afiorded by matching recesses 81 in successive laminae I.

If difliculty should be experienced in achieving acceptably close limits for the axial dimension of a blade carrier element with a laminar construction in accordance with the invention, without recourse to special finishing of the surfaces of individual laminae, such ditficulty may be met by using laminae of differing standard thicknesses as illustrated in Figure 6 so that by ap propriate combinations of laminae the correct thickness may be obtained.

I claim: a

1. A bladed rotor for an axial flow gas turbine operating at high temperatures comprising a rotor body composed of a plurality of fiat metal discs, means to hold the discs together in mutual- 1y supporting relation as a pack, some of said discs having a plurality of circumferentially spaced apertures therethrough extending for only a part of the radius and only partly overlapping like apertures in adjacent discs to define a coolant passageway extending between laminae from a point adjacent the axis of the pack to its margin, blades, and means afiixing said blades adjacent the marginal termini of said passageways.

2. A bladed rotor as claimed in claim 1 where in the face of the rotor is provided with a scooplike protrustion for entraining air into said coolant passageway at a point adjacent the axis of the pack.

JOSEPH ATKINSON.

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

UNITED STATES PATENTS Number Name Date 702,461 Nadrowski June 17, 1902 764,230 Edwards July 5, 1904 929,129 Harder July 27, 1909 1,210,831 Pfeiffer "I-" Jan. 2, 1917 1,289,278 Schmidt Dec. 31, 1918 1,347,031 Guy July 20, 1920 1,429,570 Dake Sept. 19, 1920 1,431,636 Dake Oct. 10, 1922 1,455,022 Dake May 15, 1923 1,959,220 Robinson May 15, 1934 2,187,033 Hubacker Jan. 16, 1940 2,271,971 Doran Feb. 3, 1942 2,354,304 Celio July 25, 1944 FOREIGN PATENTS Number Country Date 46,769 Denmark Jan. 16, 1933 319,622 Great Britain Dec. 18, 1930 736,188 France Sept. 12, 1932 790,131 France Sept. 2, 1935 OTHER REFERENCES The Book of Stainless Steels, by E. E. Thum, 2nd ed. pub. by The American Society of Metals, Cleveland, Ohio, Jan. 1935.

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