US2786625A - Turbo-machines - Google Patents

Description

March 26, 1957 N. H. KENT EI'AL 2,786,625

TURBO-MACHINES Filed April 3, 1952 TURBO-MACHINES Nelson Hector Kent, Allestree, Derby, Norman Robert Robinson, Quarndon, Derby, and'Cyril Armer, Chellaston, Derby, England, assignors-to Rolls koyce "Limited, Derby, England, a British company Application April 3, 1952, Serial No. 280,233

'11 Claims. (Cl. 230-134) This invention relates to turbo rnachines and is concerned more especially with rotor constructions for such machines.

The object of this invention is to provide :a simple, light and inexpensive form of rotor for axialeflo'wturbomachines, such as axiabflow compressors ofgasaturbine engines.

According to this invention, a rotor drum comprises a plurality of stages of rotor blades, a series of like discs, one for each of the stages of rotor "blades, a thin-walled tube of substantially uniform diameter, and a series of blade-carrying rings each having an internal diameter-to fit on the tube, said discs being arranged within-the tube in an axially-spaced relation appropriate to the-spacing of the stages of rotor blades-and being located "by having their rims brazed to the inner surface of the tube, and the blade-carrying rings beingbrazed to the external surface of the tube to be-coplanarwith'the discs.

In such a rotor drum, the centrifugal? loads due "tothe blades are transmitted to thediscs,'-and the tube acts to locate the discs, to transmit torque between the discs and rings, and to take the bending loads on the rotor.

The discs may have axially widened rims and the rings may be of H-section, one flange fitting on the tube and the other being arranged to receive the blades, which are conveniently attached to the rings in the manner of mounting blades described in the specification of co-pending application Serial No. 280,234 in the name of N. R. Robinson. The web of the H-section rings normally increase in radial extent from one end to the other of the rotor drum.

One construction of rotor drum having the above and other novel features will now be described with reference to the accompanying drawings, in which Figure 1 is an axial half section through the rotor, and Figure 2 is a similar view illustrating an alternative construction.

In the construction of rotor drum shown in Figure 1, there is a torque-transmitting and bending-load-carrying tube 1 which is thin-walled and cylindrical, and has a diameter slightly less than the minimum diameter of the working gas passage, and a plurality of discs 2 which are all of equal diameter and are fitted within the tube 1 in axially-spaced relationship lengthwise of the tube. The discs 2 have axially widened rims 2a by which they are secured to the tube 1 by brazing and the discs are slightly thickened at their centres.

The external surface of the tube 1 is stepped to afford a number of axially-facing abutment shoulders 10, one per disc and each slightly offset from the plane of the disc 2. A number of H-section blade-carrying rings 3, one for each stage or ring of blades 4 except the first stage of blades 5 are fitted to the outside of the tube 1, being located axially by the shoulders 1a to have their webs coplanar with, that is radially aligned with the associated discs 2.

The blade-carrying rings 3 are secured to the tube 1 by brazing one flange 3a of each H-section ring 3 to the tube 1. The other flange 3b of each ring is formed as a bladenited States Patent 2 carrying The webs of the H-section rings '3'increase in radial dimension from the inlet end-of the compressor rotor tothe outlet end thereof. "The ringsBareformed with radial slots to receive the root ends-4a of thebla'des 4, which are brazed in the slots.

The first stage blades 5 are carri'edby a dished disc 6 having a cylindricalsocket 6a into which the end of the tube 1 is brazed, and the disc 6 is formed with a stubshaft 6b to engage a frontbearing for'the rotor.

"The inner wall of the working gas passage may be partly formed by frusto-conical sheet-metal sleeves 7 with inturned flanges at "their axially spaced edges; which sleeves extend between-and are'secured'to the blade-carrying flanges 3b of the H-section rings 3.

The'blade-carryingring at the outlet-end-of the rotor may support a sheet-metalsleeve=like member 8'forming .a rotating part .of a'labyrinth seal of which the stationary part isindioatedat 9.

'Theztube 1 byrneans 'of which the torque is transmitted between the discs 2 and Lbymeans of which thedis'cs 2 are heldtin axially-spaced relation may .be-extended axially as indicated at 1b to :be connected with a rotor disc 10 of a turbine .fordriving the compressor, for example byforming a socket toreceive a fianged axial portion 10a on the turbine rotor. This arrangementensures that the compressor and turbine rotors are coaxial one with the other.

Instead of -frusto-co'nical sheet-metal sleeves 7, there may be provided between the blade carryin'g rings3 as shown in Figure 2 ystationaryelements 12 carried by the associated stator blading 1-1, "which stationary elements may be frusto-conioal rings or segments of such rings.

The parts of the compressor rotor as described are preferably formed from eithertanaluminium alley or from steel.

Where the parts to be brazed are made from steel, brazing will be copper or copper/silver brazing and where aluminium parts are to be brazed together aluminium brazing will be employed.

The discs 2 are formed with central apertures by which the spaces between the discs and within the tube 1 are vented during the brazing operation.

We claim:

1. A rotor for :an axial-flow fluid machine, said rotor comprising a plurality of rows of rotor blades, a thinwalled tube of substantially uniform internal diameter, a series of like discs each having an overall diameter to fit within the bore of the tube and extending radially at least substantially to the axis of rotation of the rotor, there being one such disc for each of a plurality of said rows of rotor blades, and a corresponding series of rings each having the blades of one of said rows of rotor blades mounted at its periphery and each having an internal diameter to fit on the external surface of the tube, said bladecarrying rings being secured on the tube in an axiallyspaced relation appropriate to the spacing of the rows of rotor blades by being brazed to the external surface of the tube, and the discs being brazed to the internal surface of the tube each to be coplanar with a corresponding rlng.

2. A rotor as claimed in claim 1, wherein the discs have axially-widened rims by which they are brazed to the tube.

3. A rotor as claimed in claim 1, wherein the rings are of H-section, are brazed to the tube through their inner flanges, and have their outer flanges formed as blade-carrying supports.

4. A rotor as claimed in claim 1, having a dished disc affording adjacent its periphery a socket to receive one end of the tube, the tube being brazed into the socket, and having the first stage blades carried at the periphery of the dished disc.

5. A rotor as claimed in claim 4, wherein the dished disc comprises a central, axially-projecting portion to afford a stub-shaft by which one end of the rotor can be supported.

6. A rotor as claimed in claim 1, wherein the tube is stepped in external diameter to afford axially-facing locating shoulders for the rings.

7. A rotor as claimed in claim 1, wherein said tube has an axial extension projecting beyond an end stage of said blades, said extension being adapted for torque transmission.

8. A rotor as claimed in claim 7, comprising also a further disc having an axially-extending portion, and a ring of turbine blades at the periphery of the further disc, the axial extension of the tube providing at its end a socket receiving said axially-extending portion on the further disc.

9. A rotor as claimed in claim 1, comprising also .frusto-conical sheet-metal rings extending between and secured to the blade-carrying rings to form parts of the inner wall of a working gas passage of the turbo-machine.

10. A rotor for an axial-flow fluid machine comprising a plurality of stages of rotor blades, an imperforate thinwalled tube of uniform internal diameter and stepped external form to provide a series of axially-spaced shallow shoulders one for each stage of said rotor blades, the tube having a mean diameter which is more than half the diameter of any circle traced by the inner end of a rotor blade, a plurality of blade-carrying rings, one for each stage of said rotor blades, each ring having an inner diameter to fit on the external surface of said tube at the corresponding shoulder, and said rings being brazed to the outer surface of the tube, and a plurality of like discs, each said disc having a diameter to fit Within the tube and being substantially solid, there being one of said discs located within the tube to be coplanar with each of said blade-carrying rings and said discs being brazed at the rims to the internal surface of the tube.

11. A rotor for an axial-flow fluid machine having Working gas passage means including an inner Wall, said rotor comprising a plurality of rows of rotor blades, an imperforate thin-walled tube of substantially uniform interrral diameter, said diameter being less than the minimum diameter of the working gas passage wall, a plurality of rings one for each row of said rotor blades, each ring having an inner diameter to fit on the external surface of said tube and each ring having the rotor blades of one of said rows secured to its periphery, and said rings being brazed to the external surface of the tube in axially-spaced relation, and a plurality of like discs each of said discs having an overall diameter to fit within the bore of the tube and extending at least substantially to the axis of rotation of the rotor, one of said discs being located Within the tube in the plane of each of said rings and said d-iscs being brazed to the internal surface of the tube, whereby each of said rings, the corresponding disc, and the portion of the tube therebetween form a substantially continuous circular disc Whose diameter is the diameter of the root portions of the blades of the corresponding row, thereby to resist the centrifugal stresses set up by said blades on rotation of the rotor.

References Cited in the file of this patent UNITED STATES PATENTS 2,243,467 Jendrassik May 27, 1941 2,501,614 Price Mar. 21, 1950 2,540,991 Price Feb. 6, 1951 2,579,745 Lombard et al. Dec. 25, 1951 FOREIGN PATENTS 238,207 Switzerland Oct. 16, 1945 274,606 Germany May 25, 1914 586,562 Great Britain Mar. 24, 1947

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