US2931623A

US2931623A - Gas turbine rotor assembly

Info

Publication number: US2931623A
Application number: US656527A
Authority: US
Inventors: Hyde John Alan Courtney
Original assignee: Orenda Engines Ltd
Current assignee: Orenda Engines Ltd
Priority date: 1957-05-02
Filing date: 1957-05-02
Publication date: 1960-04-05
Anticipated expiration: 1977-04-05
Also published as: GB837469A

Description

April 5, 1960 J. A. c; HYDE GAS TURBINE ROTOR ASSEMBLY Filed May 2, 1957 INVENTOR. V J. A. c. HYDE United States Patent GAS TURBINE ROTOR. ASSEMBLY John Alan Courtney Hyde, Georgetown, Ontario, Canada, assignor to Orenda Engines Limited, Malton, Ontario, Canada, a corporation Application May 2, 1957, Serial No. 656,527 2 Claims. (Cl 253-39.15)

This invention relates to gas turbine rotor assemblies and, in particular, to a gas turbine rotor assembly in which novel means are provided for conveying cooling air to the interior of a turbine blade provided with passages for cooling purposes.

The use of cooled gas turbine blades in gas turbine engines of the type commonly used to power jet propelled aircraft is now a well established practice due to the high temperatures which are encountered in the engine during operation.

The use of such cooled turbine blades, however, creates a number of problems in the design of the turbine rotor assembly. One of these problems is the provision of means to convey the cooling fluid, which is usually air, to the interior of the turbine blade where it may flow through the cooling passages provided within the blade. One method of solution which has been adopted by a number of manufacturers is to provide the blade root itself with a passage for the transmission of cooling air. Such a passage is diflicult to machine and usually requires that the blade root be made somewhat larger than ,would otherwise be necessary since the passage in the blade root weakens it considerably and more material must be used to compensate for this factor. The use of more material may increase the over-all weight of the blade which, in itself, is an undesirable feature.

Other methods which have been employed in an attempt to overcome the problems attendant upon the use of a passage within the blade root include the use of a root platform which is spaced from the periphery of the rotor disc upon which the blades are mounted to provide a plenum chamber between the rotor disc and the blade itself into which cooling fluid may be conducted and from which it may be led into the cooling passages Within the blade without the necessity of weakening the blade root itself.

This methodinvolves the disadvantage that it is necessary to seal the edges of the annular ring of root platforms to enclose the plenum chamber. As a result, additional weight is added to the rotor assembly which, again, is a disadvantage whichit would be desirable to eliminate. g

It is an object of the present invention to employ a construction in which the cooling air may be conducted from a gallery within the rotor disc to the interior of a hollow gas turbine blade without either a passage through the root of the blade or a fully enclosed, heavy plenum chamber beneath the root platform.

According to the invention, the gas turbine rotor assembly comprises a rotor disc having turbine blades mounted on and extending radially therefrom, each blade having a root platform spaced from the rotor disc, the

root platform being hollow and constituting a plenum chamber in communication with cooling passages within the blade, a gallery for cooling fluid in the rotor disc having an opening beneath the root platform of each blade, an aligned opening in the radially inner; surface of the root platform and means operable under the infiuence of centrifugal force to join the two openings with a substantially air-tight conduit.

Other advantages and objects of the invention will appear as the following detailed description proceeds A preferred embodiment of the invention is illustrated in the accompanying drawings in which like reference'numetals denote like parts in the various views and in which:

Figure 1 is a partially cut away perspective view of a portion of a gas turbine rotor disc supporting a gas turbine blade, and

Figure 2 is a section taken along line 2-2 of Figure 1.

In Figure 1 a fragment of a gas turbine rotor assembly is shown. The rim 10 of the rotor disc supports gas turbine blades shown generally at 11. The rim 10 of the rotor disc is, of course, supported by a structure which enables the rim 10 to rotate about an axis. Since this part of the structure forms no part of the present invention and iscommon knowledge, it is not described in detail. It may be noted, however, that the rotor is of the split disc construction, comprising two mating discs 10:1 and 10b in abutment near their periphery b'ut separated by a space adjacent their centres.

Each gas turbine blade 11 is provided with a root portion 12 which is a'snug sliding fit within a root slot 13 in the rim 10, means being provided to lock the root portion 12 in the slot 13 when it is in the position shown in Figure 1. These means are also common knowledge in the art and; accordingly, are not shown in the drawing.

The gas turbine blade illustrated in the drawings accompanying this application is shown as having, in addition to the root portion 12, a root platform 14 which extends laterally of'the root on either side thereof and a central forged blade core 15 which is provided with grooves 16 cut in its external surface in a direction parallelto the longitudinal axis of the blade core.

A sheet metal casing 17 is provided with an upper wall 18 having an aperture through which the blade core 15 protrudes and having side walls 19 which depend from the free edges of the upper wall 18 and which are secured to theedges of the root platform 14 by brazing or other suitable means. A blade. skin 20 is provided around the forged blade core 15 to enclose the grooves 16 to define passages for cooling fluid, the lower end of the skin 20 being brazed, welded or similarly secured to the upper wall 18 of the casing at 21. Brazing, welding or similar means of securing are employed to fix the side walls 19 of the casing 17 to the edges of the root platform 14.

conjunction with the root platform 14, a plenum chamber PC which is in communication with the grooves 16 in the blade core 15 so that cooling air in the chamber PC has free access to the cooling passages 16 within the blade skin 20.

A plurality of first passages are provided in the rim 10 of the rotor disc, one on either side of each root slot 13 as may-be seen in Figure 2, the passages being cylindrical and each having its axis lying along a radius of the rim 10. Since each passage 22is similar toeach other such passage and since all the structure associated'with each passage is similar to the structure associated with each other passage, the description will proceed with reference to only one such passage and associated structure. The end of the passage 22 adjacent the periphery 23 of the rim 1% is enlarged at 24 to provide an enlarged diameter, the shoulder 25 separating the portion 24 from the passage 22 constituting a stop for a purpose which will be later described. The'other end of passage 22 is in communication with a gallery 22a which lies within the rotor rim 10 and which is constituted by the space separating the two sections of the split disc rotor. This gallery or space is in communication with a source of cooling air.

Coaxial with the first passages 22 are a plurality of second passages 26 in the radially inner surface 31 of the root platform 14, the end of the passage 26 adjacent the Patented Apr. 5, 1960 passage 22 being similarly enlarged at 28 to provide a larger diameter portion, the shoulder 29 separating the passage 26 from the enlarged portion 28 constituting a second stop for a purpose which will subsequently be described. 7

A tube 30 which is freely slidable in the enlarged portion 24 of passage 22 is positioned therein, the tube 30 being of a length which is greater than the separation between the radially inner surface 31 of the root platform 14 and the periphery 23 of the rotor rim 10. t The tube 30 has an external dimension which, as mentioned above, is a sliding fit within the enlarged

portions

24 and 28 of

passages

22 and 26 which are of equal diameter and has an internal dimension equal to the diameter of-the

passages

22 and 26 which are also of equal diameter. Hence, when 7 the tube 30 is in the position shown in Figures 1 and 2 it constitutes a substantially air-tight conduit between the plenum chamber 27 and the passage 22 which is in communication with a gallery 22a within the rim of the rotor disc.

The distance between the periphery 23 of the rim 10 and the shoulder 29 separating the

portions

26 and 28 of the passage 26 in the root platform 14 is less than the length of the tube 30 but the distance between the radially inner surface 31 of the rootplatform 14 and the shoulder separating

portions

24 and 22 of the passage 22 in the rotor rim 19 is greater than the length of the tube 30.

Having now set forth the structure which embodies the present invention, the mode of operation will be described.

Assuming the rotor rim 10 and the associated structure to be stationary and not revolving, "and the axis of the rotor to be horizontal, the tubes 30.near the top of the rotor will occupy a position in which the end a of the tube will be in abutment with the shoulder 25 due to gravitational forces. .Since the distance between the shoulder 25 and the radially inner surface 31 of the root platform 14 is greater than the length of the tube,.the end 30b of the tube will, be completely free and clear of the root platform and, hence, the blades 11 can be readily removed from the rotor rim by sliding it in a direction axially relative to the rotor rim 10 and in the sense of the leading edge otthe blade to remove the root 12 from the slot 13. As the rotor is moved to position successive blades above the axis of rotation, the tubes 30 associated with such blades will drop into the drillings 24 and thereby free these blades-for removal. The presence of portion 19b of side wall 19a of-the casing prevents the removal of the blade in a direction axially of the rotor and in the sense of the trailing edge. This portion 19b is necessary to form a barrier for the motive fluid in the turbine which could otherwise bypass the blades by flowing between the rim 10 and the root platform 14 of the blades.

When the rotor rim 10 is rotating, however, centrifugal forces will be set up within the rotating mass and,

as a result, tube 30 will movein a direction radially outthe enlarged portion 24 of thepassage-ZZ even though the end 30b is in abutment with shoulder 29. Thus, when the rotor rim 10 is revolving as is the case when the engine is in operation the tube 30 will constitute a; substantially air-tight conduit between the gallery 22a in the rim 10 and the plenum chamber 27 defined'by the root platform 14 and the sheet metal casing 17 surrounding it. As a result, cooling air may follow the flow paths indicated by the arrows in Figures 1 and 2 to provide cooling means for the blade.

The structure which has been disclosed in the specification and illustrated in the drawings providesmeans for supplying cooling air to the interior of-agas turbineblade without the necessity of providing a passage through the root of the blade and without the provision of enclosing members to enable the space between the lower surface 31 of the root platform and the periphery of the rim 23 to define a plenum chamber in thislocation. As a preferred construction the plenum chamber is integral with and carried by the blade in a manner which can be done with a considerable saving in weight.

In addition, a positive sealing arrangement has been provided to conduct the cooling air from the gallery 22a within the rim 10 to the passages 'in'the turbine blade which means will still permit individual blade removal without disassembling any. of the cooling conduits.

While the inventionhas been disclosed and described in detail in the form of a single preferred embodiment it is to be understood that this embodiment is considered 7 to be illustrative of the invention rather than limiting and minor modifications may be made in the construction and arrangement of parts without departing from the spirit of the invention or the scope of the appended claims.

What I claim as my invention is:

1. A gas turbine rotor assembly comprising a rotor disc in which there is provided an annular cavity in communication with a source of cooling fluid. a rim on the rotor disc, the rim having a plurality of circumferentially spaced, axially aligned slots cut therein, a blade mounted in each slot by means of a root portion adapted to be inserted in the slots in an axial direction, cooperating abutments on the sides of the slots and the roots to maintain the blades and the rim against relative radial movement, a root platform on each blade extending laterally from each side thereof and spaced from the rotor disc rim in a radial direction, a sheet metal casing surrounding the root platform on the side thereof remote from the rim of the rotor disc and having a radially outer wall spaced from the root platform and having side walls,

the radially outer wall and the side walls, in conjunction with the root platform, defining a plenum chamber, cooling passages within the blade and in fluid communication 7 with the plenum chamber, first passages in the root platform radially aligned of the rotor disc, one on each side of the blade, each first passage communicating between the plenum chamber and the space between a root platform and the rim of the rotor disc, second passages in the rim of the rotor disc radially aligned of the rotor disc and aligned with the first passages, each second passage communicating between the space between the rim of the rotor and a root platform at one end and, at the other end, with the annular cavity in the rotor disc. one second passage on each side of each slot and conduit means slidably associated with each pair of first and second passages, the conduit means being movable under the influence of gravity when the rotor is stationary, to a first position within the second passages and out of engagement with the first passages to permit withdrawal of the blades from their .slots and movable to a second position under the influence of centrifugal force when the rotor is rotating to extend from the second passages into and in engagement with the first passages to join the two passages with asubstantially air-tight conduit thereby establishingfluid communication between the annular cavity in the rotor disc, the plenum chamber and the cooling passages within the blade.

2. A gas turbine rotor assembly as claimed in claim -1 in which the conduit .means includes a tube of a length greater than the-distance from the rim of the rotor disc to the adjacent, radially inner surface'of the root platform Belluzzo Dec. 6, 1927 Bruckmann Jan. 29, 1957