US2795393A - Rotors of multi-stage axial flow compressors or turbines - Google Patents

Description

June 1957 F. B. HALFORD ET AL ROTORS OF MULTI-STAGE AXIAL FLOW COMPRESSORS'ORYTURBINES Filed Dec. 11, 1953 v 2 Sheets-Sheet l on Y INVENTORS Fen/va 8. I'lflLFOED t WILL/A M K. WILSON 8y HQQM, QM BM ATTOQNEYS J 1957 F. B. HALFORD ETAL ROT ORS OF MULTi-STAGE AXIAL mow COMPRESSORS OR TURBINES Filed Dec. 1 1, 195a 2 Sheets-Sheet 2 INVENTORS Fen/w: B. A amo/ea? WILL/AM K WILSVON BY I H @QW, QQLW Em ATTORNEYJ FIE. 5 5

United States Patent" ROTORS OFMULTI-STAGE AXIAL FLOW COIVLPRESSORS- OR TURBINES Frank Bernard Halford and William Ker Wilson, Edgware, England, assignors to The De Havilland Engine Company Limited, Edgware, England, a British com- D Application December 11, 1953, Serial'No. 397,742

1. Claim. (Cl. 253-39) This. invention relates to rotors for multi-stage axial flow compressors or turbines, and has for its object to provide a light andiyet' rigid rotoriconstruction.

A rotor construction for a multi-stage'axial flow compressor'or turbine according to the present invention comprises twowor more axially displaced discs lying in planes normal to the axis of rotation of the rotor, tubular connecting pieces extending between each. adjacent pair of discs and rigidly connected thereto, each tubular connecting piece beingiconcentric with the axis of rotation of the :rotor and having such dimensionsrelatively to the diameters of the discs between which it extends that the edge portion of eac'h of'such discsextends radially out-' wards beyond the adjacent end' of the tubular connecting piece, and blades constituting a ring of blades connected to the'outer edge portion of'each' disc, as'for example'by having the root portion thereof connected by one or more pinst'o such edge'portion.

Conveniently the root of each blade is forked to receive" the edge portion of the appropriate disc and is connected to such edge portion by one or more pins or the equivalent passing through the edge portion of the disc and the'parts of the forked blade root lying respeo tively on the'twosides of such edge portion.

Moreover it will generally be preferred to connect each blade root to'the edge portion of its disc by a single pin about which the blade is free to swing to a limited extent under the combined influence of centrifugal force and gas reaction thereon. With such an arrangement by suit able positioning of the blade root section and tilting of the longitudinal axis of the blade relatively to the pin axis, the bending stresses due to centrifugal force and gas reaction on the blade can be largely minimised for most conditions of operation, the ideal to be aimed at being, to provide for zero bending stresses at all sections of the blade.

The tubular connecting pieces extending between each adjacent pair of discs may be formedintegral with one of such. discs and be spigoted and bolted or riveted to the other disc, or may be formed separatelyfrom both discs and spigoted and bolted or riveted to the two discs.

In any case the male and female parts of each spigot joint will be arranged so that the fit of the parts tends to be tightened during operation by centrifugal loading, that is to say the male part is formed on the member which tends during operation to expand circumferentially relatively to the member carrying the female part.

I Moreover each of the tubular connecting pieces preferably includes a cylindrical portion which can constitute a surface with which sealing means on the stator can cooperate to prevent unwanted fluid leakage between the stages of the compressor or turbine. Since in many cases the diameter of the discs will increase progressively from the low pressure stage end of the rotor to the high pressure stage end thereof, it will usually be desirable for each tubular connecting piece to have a smaller diameter at one end than at the other. Thus each tubular connecting 2 piece may comprise afrusto-conical portion and an externally cylindrical portion, the frusto-conical portion providing for the desired increase in diameter while the cylindrical portion provides the desired cylindrical surface-to cooperate with the sealing means referred to.

Moreover in any case in addition to the tubular connecting pieces extending between the pairs of adjacent discs, one-or more tubular or other strut members and/or spacers may extend between the discs constituting one or more of the pairs at a point within the tubular connecting piece for the purpose of assisting in preventing distortion andyor vibration of the discs.

It will be realised that in rotor constructions according to the invention the need for a normal central rotor shaft is obviated.

Thedetai'ls of construction may vary considerably according to the requirements of each individual case but one construction according to the invention as applied to afive-stage compressor is shown by way of example together with: a modification thereof, in the accompanying drawings, in which- Figural is a sectional side elevation in a plane containing the axis of the rotor, the arrangement being shown in half sectionfor convenience of illustration on an adequate scale, and

Figure 2 is a scrap sectional view showing a modificationxof. the construction shown in Figure 1.

In the construction shown in Figure 1 the rotor comprises five spaced paralleldiscs A, B, C, D and E, the di'scsA, B, C and D each having formed integral with it" a tubular connectingLpie'ce A B C D The discs lie ihaplanes normal to the axis'of rotation of the rotor while the'tubular connecting pieces are concentric with respect to such: axis. Each of the tubular connecting pieces A B C and D hasafrusto-conical part at the end adjacent to thedisc withwhich it is formed integral, and a cylindrical section, A B C D adjacent to its other end, terminating in a flange A B C D Each of the discs B, C, D and E is provided on its appropriate'face with an annular rib Q, Q Q Q forming with the-adjacent flange A B C or D a spigot joint of which said flanges constitute the male parts, by which spigot joints, therefore, the discs A, B, C and D and the tubular distance pieces A B C and D are maintained concentric and coaxial with one another, the flanges being rigidly secured to the discs which they engage by means of rings of axial bolts F.

Formed integral with the disc A is also a tubular strut part or spacer A extending between the discs A and B and connected to the disc Bby a spigot joint and bolts as indicated at A A In addition a frusto-conical strut member or spacer G extends, as shows, between the disc's A and B to assist in preventing distortion and/or vibration of the discs, and is connected at one end by the spigot joint A and the bolts A to the disc B and at its other end by a spigot joint A and bolts A to the disc A.

in addition tubular strut members or spacers G G extend respectively between the discs C and D to assist in preventing distortion and/or vibration of the discs, and the discs D and E and are located on the discs between which they extent by spigot joints as shown.

Rigidly connected to the face of the disc E remote from the disc D by a spigot joint and the bolts F associated with the spigot joint D is a connecting piece H of generally frusto-conical form having a series of step-like cylindrical surfaces H formed thereon and provided at its smaller end with a tubular flange H by which it can be connected to one end of a turbine shaft or the equivalent.

The disc A is also provided with a tubular extension A by which it can be supported in a suitable bearing as indicated at A Each of the discs A, B, C, D and E has a rim portion, A B C D E, which extends radially 3 outwards beyond the adjacent tubular connecting piece or pieces A B C D and a ring of rotor blades 1. K, L, M, N, is connected to each of these rim portions as shown each blade having a forked root J K L M N the sides of which lie on opposite sides of therim portion of the disc and are connected to it by a single pin J K L M N passing through bores respectively in the disc and the root portion and on which the blade is free to rock to a limited extent- The disposition of each pin J K L M N in relation to the longitudinal axis of its blade and the blade root section is such that bending stresses on the blade due to centrifugal force and gas reaction are largely eliminated.

The various spigot joints between the parts A B, B C, C D, D E, H, G, G and G are so arranged, as regard the parts on which the male and female parts of each spigot joint are respectively formed, that in operation the loads imposed on the parts by centrifugal force will tend to cause greater expansion of the male part on each spigot joint than of the female part. Thus, for example it will be seen that in the spigot joint between the parts A and G the male part is on the disc A which, being relatively heavily loaded centrifugally during operation, will tend to expand more than the adjacent end of the conical strut member G. Thus centrifugal force tends to tighten the spigot joints during operation.

Small bleed holes (not shown) will preferably be pro vided between the spaces between the discs A, B, C, D and E to prevent the risk of pressure build-up in these spaces, as for example when rapid changes in altitude or operating conditions occur.

In the construction shown the stator assembly, within which the rotor assembly is mounted, is constructed in accordance with the invention forming the subject of co pending British patent application No. 17,413 of 1952 with the various blade rings of the stator carrying annular sealing members 0, O O and 0 provided with sealing parts cooperating, as shown, with the parts A B C D and H of the rotor to limit unwanted flow of working fluid between the stator blade rings and the rotor.

It is to be understood, however, that the form of stator assembly shown is shown by way of example only and that rotor assemblies according to the present invention may be employed with other forms of stator assembly.

It will, moreover, be readily understood that in con-.

structions according to the invention any one or more of the tubular connecting pieces extending between the discs may either be formed integral with one of the two discs between which it extends or may be formed separately from each of these discs and connected to each of the two discs by a spigot or like joint and bolts, rivets or the like, while the tubular strut members, when provided, may either be connected at one or both of their ends to the discs between which they extend or may merely make a close fit with appropriate locating surfaces on these discs so as to be held in position without being positively connected to the discs.

Thus, in the modification shown in Figure 2 of the accompanying drawings, which is to be regarded as applied to a structure of rotor otherwise similar to that shown in Figure 1, the discs constituting each of the pairs B, C and C, D are connected to one another by a tubular connecting piece P or P the ends of which are connected to the appropriate discs by means of spigot joints, and bolts F. The spigot joints comprise respectively female parts R, R R R R R on the discs and male parts S, 5 S S 5 S constituted by flanges on the ends of the tubular connecting pieces. The connecting pieces P and P moreover includes cylindrical parts P similar to the parts B and C of the connecting pieces B and C in Figure 1 and cooperating with the sealing members C C. In Figure 2 it is also assumed that the connecting pieces A and D of Figure 1 have been replaced by connecting pieces P and P formed separate respectively from the discs A and B and from the discs D and E and connected by spigot joints and bolts to the discs between which they extend.

What we claim as our invention and desire to secure by Letters Patent is:

A rotor construction for a multi-stage axial flow compressor or turbine comprising at least two axially displaced discs lying in planes approximately normal to the axis of rotation of the rotor, tubular connecting pieces extending between each adjacent pair of discs and rigidly connected thereto, each tubular connecting piece being concentric with the axis of rotation of the rotor and having such dimensions relatively to the diameters of the discs between which it extends that the edge portion of each of such discs extends radially outwards beyond the adjacent end of the tubular connecting piece, each tubular connecting piece being separate from at least one of the discs between which it extends, being located concentrically with respect to that disc by a spigot joint and con: nected tothe discs at a radial diameter greater than the diameter of the said tubular connecting pieces by a series of axially extending bolts the heads of such bolts being accessible from outside the rotor and the outer edge portion of each disc being separately formed to independently support the root portions of a ring of rotor blades, and including at least one unstressed tubular strut member extending between at least one adjacent set of discs at a point within the tubular connecting pieces.

References Cited in the file of this patent UNITED STATES PATENTS 1,362,074 Baumann Dec. 14, 1920 1,452,602 Herr Apr. 24, 1923 2,452,782 McLeod et al. Nov. 2, 1948 2,530,477 Ostmar 2. Nov. 21, 1950 2,675,174 McDowall Apr. 13, 1953 2,738,126 Edwards Mar. 13, 1956 FOREIGN PATENTS 621,315 Great Britain Apr. 7, 1949 667,979 Greae Britain Mar. 12, 1952

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