US3008689A

US3008689A - Axial-flow compressors and turbines

Info

Publication number: US3008689A
Application number: US523900A
Authority: US
Inventors: Morley Frederick Willia Walton; Cook Henry
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1954-08-12
Filing date: 1955-07-22
Publication date: 1961-11-14
Anticipated expiration: 1978-11-14
Also published as: FR1134548A; GB781771A; BE540433A

Description

196.1 F. w. w. MORLEY ETAL 3,008,689-

AXIAL-FLOW COMPRESSORS AND TURBINES Filed July 22, 1955 4 Sheets-Sheet 1 FIG. 1. 12 13 12 K 11. s5z..M..

' ATTORNEYS Nov. 14, 1961 F. w. w. MORLEY ETAL 3,008,689

AXIAL-FLOW COMPRESSORS AND TURBINES 4 Sheets-Sheet 2 Filed July 22, 1955 /M 22 .m. 2 a w 4m 41-- I 8 6 .m. 4| 1 3 1 .s... .7 F hu h 6 I H 1 5 1 a 1 3 0 2 2%2 W2.

INVENTOR WQM QMW 1 Q .222 $22.2 RMM ATTORNEYS Nov. 14, 1961 F. w. w. MORLEY ETAL 3,008,589

AXIAL-FLOW COMPRESSORS AND TURBINES Filed July 22, 1955 4 Sheets-Sheet 3 ATTORNEYS N 1961 F. w. w. MORLEY ET AL 3 AXIAL-FLOW COMPRESSORS AND TURBINES Filed July 22, 1955 4 Sheets-Sheet 4 V TOR M QEELMMWMQ United States Patent.

3,008,689 AXIAL-FLOW COMPRESSORS AND TURBINES Frederick William Walton Morley, Castle Donington,

and Henry Cook, Derby, England, assignors to Rolls- Royce Limited, Derby, England, a British company Filed July 22, 1955, Ser. No. 523,900 Claims priority, application Great Britain Aug. 12, 1954 11 Claims. (Cl. 253-77) This invention relates to axial-fiow bladed rotors for compressors and turbines, and relates in particular to compressors and turbine rotors of the kind having blades, the root-fixing portions of which engage with associated compressor or turbine structure and are connected to the blade portion proper, which is of aerofoil section, by an intermediate portion. Such blades will be referred to as blades of the kind described.

An object of the invention is to provide a construction wherein the said intermediate portions of the blades are of suitable form for the transmission of loads between the associated blade portions and root-fixing portions, and wherein the leakage of working fluid from the high-pressure side of the blade row to the low-pressure side between the intermediate portions of adjacent blades is eliminated or substantially reduced. Another object of the invention is to provide a boundary for the working fluid passage of suitable form between adjacent blades of a blade row.

According to this invention an axial-flow compressor or turbine having blades of the type described is provided with separate platform members between pairs of blades, the platform members being secured to the associated compressor or turbine structure by fixing means and forming the boundary of the working fluid passage between adjacent blades of a blade row, and means is provided associated with each platform member substantially to close off the space bounded by the inner surface of said intermediate portions of the blades, the

boundary of the working fluid passage, and the surface of said associated compressor or turbine structure and thereby to minimise the leakage of working fluid. There will also be provided locking means where appropriate,

to prevent disengagement of said fixing means. 7

The invention is primarily applicable to the rotor blades of compressors or turbine, though in certain constructions it may be applied to the stator blades.

Each blade may carry a platform portion which will abut against the said platform members on either side of it to form a continuous boundary for the working fluid.

According to a feature of the invention the said closing may be effected by means formed integral with the associated platform member. These means may comprise for example a circumferentially-extending plate formed at one end of the platform member. Alternatively the platform member itself may close off the said space over a substantial proportion of its axial dimension.

According to another feature of the invention, the closing may be effected by a separate plate member; the plate member may be adapted to engage with the platform member and the associated compressor or turbine structure to lock the platform member against disengagement during operation.

According to another feature of the invention the fixing means may comprise parts formed on the associated compressor or turbine structure and on the platform member. According to yet another feature of the invention, said parts may comprise a projection substantially T-shaped in cross section on one member engaging with the cooperating wall of a groove on the other member.

Where the invention is applied to a compressor or turbine rotor, the T-shaped projections may extend across the rotor from its forward face to its rear face, either axially or skewed, 'or the projections may extend circumferentially or tangentially of the rotor, the grooves being formed in the platform members. Where the projections extend across the rotor, some form of locking means will be provided to retain the fixing means in engagement.

Four embodiments of this invention will now be described by way of example with reference to the accompanying drawings in which,

FIGURE 1 is an axial view of a first embodiment,

FIGURE 2 is a developed plan view of FIGURE 1,

FIGURE 3 is a section on the line III--III of FIG- URE 2,

FIGURE 4 is a section on the line IV.-IV of FIG- URE 3,

FIGURE 5 is an axial View of a second embodiment,

FIGURE 6 is a developed plan view of FIGURE 5,

FIGURE 7 is a section on the line VII-VI I of FIG- URE 6,

FIGURE 8 is a section on the line VII-VIII of FIG- URE 6.

FIGURE 9 is a view corresponding to FIGURE 1 of a third embodiment,

FIGURE 10 is a view of the third embodiment correspoding to FIGURE 8,

. FIGURE 11 is a view corresponding to FIGURE 1 of a fourth embodiment,

FIGURE 12 is a developed plan view of FIGURE 11, partly in section, and

FIGURE 13 is a view on the line XIII-XIII of FIG- URE 12.

Similar parts in different figures are indicated by the same numerals.

Referring now to FIGUR'ES l to 4 there is shown a compressor disc 10 which is formed with fir-tree slots '11 extending between the front and rear faces of the disc and through the periphery :10 thereof. Compressor blades 12 are mounted on the disc 10 by having their roots in engagement with the fir-tree slots 11 and each blade comprises a blade portion proper '13 which is of aerofoil section, a fir-tree root section 114 which engages in the corresponding fir-tree section slot 11 in the disc, and an intermediate portion 15 which extends between the 'fir-tree root portion 14 and blade portion proper 13. The intermediate portion 15 may be of rhomboidal section throughout its length or it may change gradually from rhomboidal section where it joins the fir-tree root portion 14 to a substantially aerofoil section where it joins the blade portion proper 13. The blade 12 is also formed with a platform portion 16 at the junction of the blade portion 13 and the intermediate portion 15, and the platform portion has the form of a rhombus and is also curved to conform with the circumference of the disc 10.

On each of the projecting portions between adjacent slots 11 there is formed a substantially T-shaped projection 17, the arms of the projection extending tanof the platform. These are provided with inwardly-facing toes 20 one on each side of the groove 19. The toes 20 are not continuous from the leading to the trailing edge of the platform member 18, but are cutaway adjacent their centres as indicated at 20a. Each platform member 18 is adapted to engage with one of the T-shaped projections 17, the inwardly-directed toes of the platform member engaging under the tangentially-directed arms of the T-shaped projection.

In order to lock each platform member 18 axially relative to the disc 10, and to prevent flow of gas from one side of the disc 10 to the other through the space between the roots of the blades 12, there are provided a number of plates 21 one for each of the platform members 18. A groove 22 is also formed in the rim of disc 10, the depth of the groove 22 being substantially equal to the depth of the fir-tree slots 11. A corresponding groove 23, but of less depth, is also formed at the base of the groove 19 in the platform member 18, that is, on the underside of the part of the platform member 18 which bounds the working fluid passage. In operation, each plate 21 engages with the

grooves

22 and 23, thereby preventing axial movement of the platform member 18 with respect to thedisc 10, and the plate 21 extends circumferentially into abutment with the intermediate portions 15 of the two adjacent blades 121 plates 21 tend to be main tairied in the grooves 23 in the platform members may centrifugal force during operation of the compressor, but are also maintained in engagement by the inner edges of the plates 21 co-operating with outwardly-facing surfaces 24 at the outer side of the root portions 14 of adjacent blades.

The blades 12, platform members 18 and plates 21 are assembled as follows. A blade 12 is mounted on the disc with its fir-tree root portion 14 inserted in a groove 11, the blade being located axially in the groove in any known or convenient manner. The plate 21 is dropped into groove 22 in the disc immediately to one side of the blade 12, and a platform member 18 is mounted on the disc by engagement with the projection 17 immediately on thesame side of the blade. The plate 21 is then raised until it cooperates with the groove 23 in theplatform 18 (i.e., until it i's in the position shown in FIGURE 4) and the next adjacent blade 12 is then mounted on the disc, the outwardly-facing surfaces 24 on the root portion 14 of the blades preventing the plate 21 becoming disengaged from the groove 23 in the platform member 18. In the case of the insertion of the last platform member 18 of a disc, two blades are left out of their slots 11, a plate 21 is inserted in the groove 22 between the two empty slots 11, and the platform member 18 is mounted on the projection 17 between the slots. The plate 21 is then moved radially outwardly to engage with the groove 23 in the platform member 18, and held in this position while the two blades 12 are inserted into the adjacent slots-11.

Referring now to the construction of FIGURES to 8 there is shown a similar arrangement in which platform members 18 are engaged with projections 17 on the periphery of the disc between adjacent fir-tree slots 11 in which are mounted blades 12.

In case, however, the groove 19 in each of the platform members 18 is closed at one end by a transverselyextending wall 25 and the platform members 18 are engaged with the disc 10 by being slid into engagement with the projections 17 from the upstream side of the disc until the walls 25 abut the ends of projections 17 which are cut away to an appropriate depth. The transverse wall 25 extends circumferentially to each side of platform member 18 for a distance appropriate to engage the intermediate portions of the adjacent blades 12, thus blanking off the spaces between the adjacent blades through which working fluid may pass. The platform members 18 are restrained against disengagement'in the forward direction from the discs 10 by means of locking plates 26. The platform members 18 are formed with pair of grooves 11, and also with a continuous circumferential groove 29 at a lesser radius than the lugs 28. The locking Plates 26 are formed with central apertures 30, and the locking plates are moved into engagement by one edge of the aperture 30 being slid into the groove in the under-cut log 28; the outer periphery of the looking plate 26 at the same time engaging with the groove 27 in the platform member 18. When the locking plate 26 is fully in engagement as just described, the inner end of the locking plate is bent into the groove 29 as shown at 31, thereby retaining the locking plate in position.

Referring now to FIGURES 9 and 10 there is shown yet another embodiment in accordance with the invention. In this embodiment the platform elements 18 are formed with a central groove 19 which is of a form suitable for having its walls cooperate with the T-shaped projection 17. Further, the base of the groove 19 of the platform member 18 is formed with a rectangular-section slot 50' terminating in a drilled hole 51 on the centre-line of the disc, to receive a locking tab 52. The platform member 18 in this case is formed with a transverse wall 25 at one end of the inwardly-turned toes 20, and the platform member extends circumferentially to abut the intermediate portions 15 of the adjacent blades at its circumferentially-spaced. edges.

In this construction the blades 12 and platform members 18 may be assembled alternately, the blades being mounted on the disc by having their fixing portions 14 slid into the corresponding grooves 11 and the platform members 18 being mounted from the forward side of the disc by the inwardly-directed toes 20 engaging the tangentially-extending arms of the corresponding projection 17. Before the platform member 18 is engaged, a looking tab 52 is inserted in the groove 50. The locking tab has a projecting portion to engage in the hole 51, and when the platform member 18 has been slid fully home so that the transverse wall 25 abuts the forward face of the disc, the end of the locking tab 52 remote from the hole 51 is bent down into engagement with the rear face of the diseas seen at 53, so as to prevent disengagement of the platform member 18 in a forward direction.

Referring now to FTGURES 11 to 13 there is shown yet another embodiment in accordance with the invention. in this arrangement the projections between adjacent fir-tree grooves 11 in the disc 10 are formed at their tips as formations which are of substantially T-seotion when seen in radial cross-section; these formations 117 being axially-extending arms which are curved as seen in FIG- URE 11 about the centre of the disc 10.

Platform members 118 are provided which are formed with a curved groove 119 so shaped as to form a pair of inwardly-directed toes 120 which are curved to corre spend with the curvature of the formations 117. The platform members 118 are preferably formed by turning from a continuous ring of the appropriate radius, the individual members being parted off.

In the construction shown the length of the platforms 118 measured in the circumferential direction is slightly less than the distance between the adjacent ends of neighbouring formations 117, so that each platform 118 can be entered in the open end of a fir-tree groove 11 and engaged with the co-operating formation 117 by a circumferential movement. It is arranged that the platform member 118 is moved circumferentially into engagement with the intermediate portion 15 of a previously inserted blade, and that this movement permits the next adjacent blade to be inserted in its groove 11 on the other side of the plaform 118. The next platform 118 may then be assembled and so on.

Before the last blade is inserted in its groove 11, the platform members 118 on each side of this groove will be assembled by being entered into the mouth of the groove and engaged with the corresponding formations 117 by circumferential movement in opposite directions. The last blade 12 may then be entered into its groove 11 between the platform members 118 thus securing them against disengagement.

What we claim is:

1. In an axial flow bladed rotor in combination, a rotor disc member having forward and rear faces and blade-root interengaging slots extending through its periphery and formations adjacent its periphery intermediate said slots; blades spaced circumferentially about said periphery and each comprising a working portion of airfoil cross-section, a root portion received in and interengaging the walls of one of said slots by which the blade is directly attached to said disc member, a platform portion disposed at the radially inner end of the working portion, and an intermediate portion between the root portion and the platform portion, there being a space between each intermediate portion and the adjacent intermediate portion radially beyond the disc member periphery and the platform portions of adjacent blades being circumferentially spaced; a separate platform member having an inner and an outer facing surface in the space between each pair of adjacent blades, each separated platform member having integral formations extending from said inner suface and in sliding interlocking engagement only with said formations adjacent the periphery of said disc member and having its outer surface aligned circumferentially with said platform portion of each adjacent blade, the outer surface forming with the adjacent blade platform portions the boundary of the working fluid passages between adjacent blades; and means associated with each separate platform member, portions of the adjacent blades and the disc member to substantially close off the space between the intermediate portions of adjacent blades to thereby minimize leakage of working fluid.

2. A rotor as claimed in claim 1 in which the said closing means is formed integral with the associated platform member.

3. A rotor as claimed in claim 2 in which said closing means consists of an inwardly and transversely-extending wall adapted to extend across said space and to abut against the associated disc.

4. A rotor as claimed in claim 2 in which the platform member itself is shaped and fitted to substantially fill and close off the space over a substantial proportion of its dimension axially of the rotor.

5. The rotor as claimed in claim 1 in which said means is a plate member separate from the platform member, the adjacent blade portions and the disc; said disc and platform member being each provided with a radial circumferential groove receiving edge portions of said plate member; said plate member having other edges substantially engaging the intermediate portions of adjacent blade whereby it closes off said space.

6. A rotor as claimed in claim 5 in which said plate is adapted to lie in said groove in the disc member to 6 permit the platform member to be fitted into position and in operation to extend partially into said groove and to extend therefrom to close off said space and to project into said groove in theplatform member, thus locking the platform member in position, and means retaining said plate in the operative position.

7. A rotor as claimed in claim 6 in which such lastmentioned means comprise parts of the roots of adjacent blades, which when the adjacent blades are in position prevent the return of the plate member from the position in which it engages the groove in the platform member.

8. A rotor as claimed in claim 1 in which one of the formations by which each platform member is fixed to the associated disc member is substantially T-shaped in cross-section on one of said members and engages in a cooperating groove formation in the other of said members.

9. A rotor as claimed in claim 8 in which the platform members are carried by said rotor disc member on which the T-shaped formations are formed, the T-shaped formations engaging with groove formations in the platform members.

10. A rotor as claimed in claim 9 in which the T-shaped formations extend across said rotor disc member from its forward face to its rear face, so that the platform members are slid on to the said T-shaped formations in a direction substantially axial of the rotor disc member.

11. A rotor as claimed in claim 9 in which the T-shaped formation extend substantially circumferentially of the rotor disc member and lie between blade root interengaging slots, and the spaces between adjacent T-shaped formations are suflieient to allow the platform members to be entered into the said spaces and then moved substan tially circumferenitally of the rotor disc member to engage one of said T-shaped formations.

References Cited in the file of this patent UNITED STATES PATENTS 1,585,713 Herr May 25, 1926 2,669,383 Purvis Feb. 16, 1954 2,751,189 Ledwith June 19, 1956 2,755,063 Wilkinson July 17, 1956 FOREIGN PATENTS 59,398 France Ian. 6, 1954 (1st addition to No. 969,413)

459,735 Italy Oct. 4, 1950 671,960 Great Britain May 14, 1952 687,507 Great Britain Feb. 18, 1953 989,556 France May 23, 1951 998,221 France Sept. 19, 1951