US2654565A - Construction of rotors for compressors and like machines - Google Patents

Description

Oct. 6, 1953 G. a. R. FEll DEN CONSTRUCTION OF ROTORS FOR COMPRESSORS AND LIKE MACHiNES 3 Sheets-Sheet 1 Original Filed Jan. 15 1946 QLJRQ Oct. 6, 1953 G. B. R. FEILDEN 2,654,565

CONSTRUCTION OF ROTORS FOR COMPRESSORS AND LIKE MACHINES 3 Sheets-Sheet 2 Original Filed Jan. 15, 1946 Inventor Wfi/W ROBE/F7 Ff/LOE V,

Attorney QM'RQM Patented Oct. 6, 1953 CONSTRUCTION OF ROTORS FOR COM- PRESSORS AND LIKE MACHINES Geoffrey Bertram Robert Feilden, Lincoln, England, assignor to Power Jets (Research and Development) Limited, London, England, a

British company Original application January 15, 1946, Serial No. 641,305. Divided and this application March 4, 1948, Serial No. 12,993.

December 19, 1945 In Great Britain 7 Claims. (Cl. 253-39.15)

This invention relates to the construction of bladed rotors for multistage axial flow compressors, turbines and similarly bladed machines, but especially rotors of multistage axial flow compressors. This application is a division of applicants copending application Serial No. 641,305, filed January 15, 1946, which issued on November 2, 1948 as Patent No. 2,452,782.

The present invention has special, though not exclusive, application in the construction of a rotor for a compressor which is to form an element in a gas turbine engine suitable for aircraft propulsion, in which the requirements of robust construction allied to light weight are of major importance. The invention lends itself to accuracy of manufacture, freedom from distortion, facility in the attachment of blading and assembly or removal of individual parts, which being broken down into comparatively small units are capable of close inspection. The construction also lends itself to the uniform distribution of temperature by virtue of the provision of favourable internal cavities in which air may be circulated or set in relative motion to act as a convective or cooling agent.

According to the invention a bladed rotor for a multistage axial flow compressor, turbine, or similarly bladed machine, comprises at least three axially spaced separate discs or wheels having radially extending bodies and axially enlarged rims between which rims the blade roots of successive rows of 'bla-ding made separately from the discs or wheels are disposed so as to space apart the opposed faces of adjacent rims,

the discs or wheels and the blade roots having complementary formations providing both for their abutment in the axial sense and their relative-radial location and the discs or wheels being held together by axially applied compressive stress so as to nip the blade roots between them, the arrangement being such that the whole of said compressive stress is transmitted between adjacent discs or wheels at their rims by the roots of the intervening row of blading and that the latter bound circumferentially an air space between said discs or Wheels.

Preferably the compressive stress is applied by a centrally and axially disposed tension element surrounded by the discs or wheels. Since the blade roots form the circumferential wall of an annular air gap left between adjacent discs or wheels cooling of the blade, if required, is facilitated. Further, since the root is held only along two opposite sides, it may be hollow, so further economising in weight and material.

The discs or wheels may have at or towards their hub portions complementary radially 10-.

eating or/and torque-transmitting formations which, however, are arranged to have an axial clearance to ensure that they do not take part in the transmission of the compressive stress applied by the tension element.

Other and more detailed features of the invention will appear from the following description with reference to the accompanying drawings, which illustrate by way of example two constructional embodiments of the invention and in which:

Figure 1 is a part longitudinal section of a rotor of an axial-centrifugal compressor constructed in accordance with the invention;

Figure 2 is an enlarged detail of part of Figure 1;

Figures 3 and 4 are detail views illustrating a modified form of blade root and mounting suitable for the construction of Figures 1 and 2.

Figure 5 is a detail view of a blade root suitable for use when frictional engagement between the roots and the enlarged wheel rims is insufiicient to ensure proper transmission of driving torque from one wheel to another.

Figures 6 and '7 are detail views showing blade roots of Figure 5 in operative engagement with suitable wheel rims.

Referring to Figure 1, it will be seen that the compressor rotor comprises a plurality of bladed discs or wheels I mounted in the form of a pack which is held together by the compressive stress applied by a tensioning element 2 passing through the hollow centres of the discs and having a tensioning nut 3 bearing on the last disc at one end and a head 4 bearing on the other end of the rotor, which in this case is formed by an additional disc 5 providing a centrifugal impeller stage of the compressor. The discs I have hubs provided with complementary spigot and socket formations 6 to locate the parts radially and transmit centrifugal stress, but which, however, have an axial clearance so as not to transmit any compressive stress. The hubs also have internal grooves to co-operate with a disc or wheel extracting tool. At their peripheries the discs I have enlarged rims 1 which are spaced axially by the roots 8 of blades 9, the latter and the discs abutting at H! (see Figure 2) for the transmission of the compressive stress, and the roots having also shoulders H engaging with an axial clearance in corresponding recesses of the rims T to afford radial location and to take centrifugal stress.

The disc I forming the left hand end of the rotor as viewed in the drawing is dished so that under the influence of centrifugal force when running it will tend to straighten and thus supplement the compressive stress transmitted axially of the rotor by the discs and blade roots. It also has an axially extending flange 12 the dimensions of which are adjusted so as to produce under the influence of centrifugal force a bending moment at the rim of the disc opposing and compensating for the bending load due to the first row of blading at the same point.

The construction illustrated in Figure 1 is of course applicable also to a purely axial compressor in which case the end discs at both ends of the rotor will be dished and provided with an axially extending flange as just described.

As can be seen, the blade roots 8 are of hollow box formation, thus enhancing the lightness of the structure.

In the modified blade root and mounting illustrated in Figures 3 and 4 (which in fact is the preferred form) the axially outermost points at which root walls [8 meet the base platform 8a of the blade 9 proper, through which points the centrifugal stress is transmitted from the blade 9, are axially inset from the leading and trailing edges of the blade, with the object of taking the centrifugal load through thicker parts of the blade section and thus obtaining a wider distribution of the stress path between blade and root. The centrifugal stress due to the blade is taken by the discs l through the entry of their enlarged rim flanges l with axial clearance into a groove formation at l3 in the sides of the roots, and the compressive stress due to the tensioning element 2 by the abutment of the upper part of the root without axial clearance at M with rebated portions of the flanges 1. The blade and root are also so arranged that the line of action l5--l5 of the centre of gravity of the blade lies in the median plane of the gap between adjacent discs I, and a stiffening rib i6 is provided in the hollow root to minimise outward bowing of the blade platform due to centrifugal force during running,

In case frictional engagement between the blade roots and the enlarged Wheel rims is insuflicient to ensure proper transmission of the driving torque from one wheel to another the sides of the blade roots 8 and the rims i have complementary discs or similar formations. These formations might for example, be afforded, as shown in Figure 5, by the provision on the blade roots 8 of dowels 20, or equivalent formations which in the construction shown in Figure 6 are adapted to crush and bite into crushable ribs 2! on the rims i of the discs or wheels I on assembly of the blades and discs.

In the construction illustrated in Figure '7 the dowels 2!! on assembly of the blades and discs are adapted to enter recesses 22 in ribs 23 on the rims I to afford the desired positive driving connection. As an alternative or in addition the wheel hubs at 6 (Figure 1) may have driving dogs.

In each of the constructions illustrated it will be noted that ample internal cavities are afforded which may be used either for the forced or natural circulation of cooling air, or for the bleeding of air under pressure from any stage of the compressor, for example through the passage formed Within the disc hubs.

It should be observed that the tension element 2 must have appreciable elasticity and to achieve this without the use of springs the tension element is made up of a central member 2, upon which the tensioning nut 3 is threaded, attached at its other end to an intermediate compression sleeve 2a which extends back along the member 2 almost to the nut 3 and is there attached to an outer tension sleeve 21) which extends away from the nut 3 again and carries the head 4 by which the tensioning element is anchored. By means of this arrangement, the inner and outer members 2, 2b are placed in tension and the intermediate sleeve 2a in compression, and the effective length of the element as a whole, and thus its effective elastic movement, are substantially trebled.

I claim:

1. A bladed rotor for a multistage axial flow compressor, turbine or similarly bladed machine, comprising at least three axially spaced, centrally bored, discs or Wheels, each comprising a rim portion and an integral body portion, said rim portion being axially enlarged as compared with said body portion and the latter being relatively thin in the sense that it radial extent is greater than its axial thickness and constitutes the major dimension of the disc or wheel; said discs or wheels having interengaging hub means; successive rows of blading separate from said discs or wheels and having blade roots disposed between said rims so as to space apart the opposed faces of adjacent rims; said rims and blade roots having complementary formations providing both for their abutment in an axial sense and their relative radial location; an axial tensioning element located within the central bores of said d s for applying an axial compression to said discs to nip said blade roots between them; said tensioning element having an outside diameter substantially smaller than the diameters of the central bores, thereby providing a clearance between said tensioning element and said discs along at least a major portion of the length of said tensioning element and leaving the radial positioning of the discs substantially entirely to the interengaging hub means, the arrangement being such that the whole of said compressive stress is transmitted between adjacent discs or wheels at their rims by the roots of the intervening row of blading and that the latter bound circumferentially a space between said discs or wheels.

2. A rotor as claimed in claim 1, wherein the spacing blade roots are of hollow box form having an internal stiifening rib.

3. A rotor as claimed in claim 1, wherein the axially outermost points of junction between the foot of a blade part proper and the root struc ture through which stress due to centrifugal force is transmitted to the adjacent disc or wheel rims are axially inset With respect to the leading and trailing edges of the blade part proper, the better to distribute the stress path from the blade part proper to the root structure.

4. A rotor as claimed in claim 1, wherein the blade roots and discs or wheels have complementary torque-transmitting formations.

5. A rotor as claimed in claim 4, wherein the said torque transmitting formation includes a rib on the one part which is locally crushed during assembly of the rotor by engagement by the other part.

6. A rotor as claimed in claim 1, wherein the discs or wheels have at or towards their hub portions complementary radially locating and torque-transmitting formations which have an axial clearance to ensure that they do not take part in the transmission of the compressive stress applied by said tension element.

7. A bladed rotor for a bladed machine such as a multistage axial flow compressor, turbine or the like, comprising at least three axially spaced separate discs or wheels each comprising a rim portion and integral body portion, said rim portion being axially enlarged as compared with said body portion and said body portion being relatively thin in the sense that its radial extent is greater than its axial thickness and. constitutes the major dimension of the disc or wheel, said discs or wheels having radially inwardly of their rims spigot and socket connection with one another to effect their relative radial location and to accommodate bending loads; successive rows of blading made separately from the discs or Wheels and having blade roots disposed between said rims so as to space apart the opposed faces of adjacent rims, said rims and the blade roots having complementary formations providing both for their abutment in the axial sense in planes normal to the axis of rotation and for their relative radial location; and an axially located tension element adapted for holding said discs or wheels together by axially applied compressive stress so as to nip the blade roots between them, the spigot and socket connections however having an axial clearance so that the whole of said compressive stress is transmitted between adjacent discs or wheels at their rims by the roots of the intervening row of blading and that the latter bound circumferentially a space between said discs or wheels.

GEOFFREY BERTRAM ROBERT FEILDEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,551,402 Junggren Aug. 25, 1925 2,401,826 Halford June 11, 1946 2,440,933 Cunningham May 4, 1948 2,458,149 Cronstedt Jan. 4, 1949 FOREIGN PATENTS Number Country Date 217,031 Switzerland Jan. 5, 1942 225,640 Switzerland May 17, 1943 492,252 Germany Feb. 20, 1930 543,985 Great Britain Mar. 23, 1942

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