US 3892497 A
An axial flow gas turbine has inner and outer casings. Arrays of stationary integral vane segments and adjacent arcuate blade ring segments are supported inwardly from and interlocked with the inner casing by arcuate segmented support members. The arcuate support members are fixedly attached to the inner casing by an arrangement of interlocking plates and bolts in registration with said support members. This arrangement not only permits thermal expansion and contraction between adjacent members with respect to one another, but it permits ease of assembly and maintenance.
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Description (OCR text may contain errors)
United States Patent 1191 Gunderlock et a]. 1 July 1, 1975 AXIAL FLOW TURBINE STATIONARY g TP -i cazo eta...... 0. RING LOCKING 3,542,483 7/1968 Gagliardi 1 415/139 3,542,483 11/1970 Gagliardi 1 415/136  Inventors: Richard P. Gunderlock, Prospect 3,752.593 3/1973 Bower-S 415/1 p Ted H. Knutzen, Rutledge, 3,781,125 12/1973 Rahaim 415/217 both of Pa. 3,841,787 9/1973 Scalzo 415/136  Assignee: Westinghouse Electric Corp., primary Examiner Hemy F. Raduazo Pmsburgh Attorney, Agent, or Firm-G. H. Telfer  Filed: May 14, 1974 21 Appl. No.: 469,928  ABSTRACT An axial flow gas turbine has inner and outer casings. Arrays of stationary integral vane segments and adja-  U.S.Cl. 415/134, 3115501137855.441155912319; cent arcuate blade ring segments are Supported 51 l Cl Fold 25 24 wardly from and interlocked with the inner casing by l l i 134 arcuate segmented support members. The arcuate [5 1 le 0 care g/ support members are fixedly attached to the inner casing by an arrangement of interlocking plates and bolts in registration with said support members. This ar-  Reierences cued rangement not only permits thermal expansion and UNITED STATES PATENTS contraction between adjacent members with respect 3,262,677 7/1966 Bobo et al, 415/217 to one another, but it permits ease of assembly and 3,275,294 9/1966 Allen et a1. 415/1 15 maintenance 3,341,172 9/1967 Rahaim s t t 1 1 t 415/139 3,427,000 2/1969 Scalzo 415/115 6 Claims, 9 Drawing Figures SHEET FIG-6. PRIOR ART I AXIAL FLOW TURBINE STATIONARY BLADE AND BLADE RING LOCKING ARRANGEMENT CROSS-REFERENCES TO RELATED APPLICATIONS In copending application Ser. No. 394.599. filed Sept. 5. 1973 now US. Pat. 3.84l.787. and owned by the same assignee. there is disclosed an arrangement of arcuate support segments supporting vane segments and blade rings adjacent the inner casing of a gas turbine.
BACKGROUND OF THE INVENTION 1. Field of the Invention:
This invention relates generally to gas turbines. and more specifically to shroud and blade ring support arrangements within a gas turbine engine.
2. Description of Prior Art:
Turbines operated with hot motive gases. for example gas turbines. require cooling fluid such as air. to control temperatures of stationary components as well as rotating components. Turbines of this type are usually provided with outer casings divided in a horizontal plane with an upper and lower half bolted together for easy assembly and service. Also. pressurized cooling air or other suitable fluid is directed through the outer casing into an outer plenum chamber or space between the outer casing and the outer diaphragm shrouds and then through the stationary turbine blades. It has been found that undesirable leakage of cooling air from the plenum chamber into the motive fluid flow path occurs during machine operation. This leakage is most pronounced at the horizontal joint of the turbine diaphragm and at the juncture of adjacent shroud portions of the stationary blade segments that comprise the diaphragm. An analysis of the harmonic vibration of the above described leakage pulses indicates that even harmonics of the turbine running speed are produced which in some instances results in blade excitation leading to failure.
Assuming that leakage of cooling air past the horizontal joint can be eliminated, an excitation pattern can still persist as a result of changes in stationary blade gauging or pitch, i.e.. spacing between adjacent blades through which the motive fluid flows. Changes in gauging results when the outer shrouds of the stationary blade diaphragm expand relative to the casing with consequent uneven shifting of the stationary blades in the circumferential direction. The amount of gauging change is proportional to the number of blades in the integral structure which is maximum for a two-half diaphragm system.
In addition to the above. shroud restraints in existing l80 divided diaphragms can develop excessive thermal stresses of a damaging nature during transient operating temperature cycles.
US. Pat. Nos. 3.427.000 by A. .l. Scalzo, and 3,493.2l2 by A. J. Scalzo and A. Zabrodsky, both assigned to the present assignee approach the problem of split casings and blade support arrangements.
Yet another approach to blade support structure was presented by copending U.S. application Ser. No. 394,599 cited earlier. Arcuate support segments therein. are arranged between the inner housing of the turbine. and vane segments and blade rings. A locking arrangement for the arcuate support segments adjacent the split in the casing has presented problems with thermal expansion of the arcuate support segments and providing effective seal members therebetween.
It is an object of the present invention to improve the restraining arrangement and sealability of the arcuate support segments.
SUMMARY OF THE INVENTION In accordance with the present invention. there is provided an axial flow gas turbine having a split casing. The split casing comprises an outer casing and an inner casing with a plenum chamber therebetween. The inner casing permits arcuate support members to be disposed inwardly thereof and adjacent thereto. The arcuate support members in turn provide support for vane seg ments and blade rings. Each arcuate support segment supporting a vane segment is locked to the inner casing by a bolt arrangement. The arcuate support segments adjacent the horizontal split in the casings are secured with a locking plate that provides restrain against movement of the arcuate support segments in both circumferential directions. Each arcuate support segment supporting the downstream edge of each blade ring has a generally radially directed lock plate restraining both the arcuate support segment and its respective blade ring.
BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of this invention will become more apparent from reading the following detailed description in connection with the accompanying drawings. in which:
FIG. I is an axial sectional view ofa portion of a gas turbine engine incorporating the invention;
FIG. 2 is an axial sectional view of the locking arrangement for the arcuate support segments constructed in accordance with the principles of this invention;
FIG. 3 is a view taken along the lines III-III of FIG. 2;
FIG. 4 is a transverse view of a portion of an annular array of ring segments and locking plates;
FIG. 5 is a prior art view of the locking arrangement of segments adjacent the horizontal split in the turbine casing;
FIG. 6 is another view of the prior art taken along the lines VIVI of FIG. 5;
FIG. 7 is an axial sectional view of a prior art locking arrangement;
FIG. 8 is a view of the locking arrangement of arcuate support segments adjacent the horizontal split in the casing. constructed in accordance with the principles of this invention; and
FIG. 9 is a view taken along the lines lXlX of FIG. 8, showing both the upper and lower casing halves.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail. and particularly to FIG. 1, there is shown an axial flow gas turbine 10. Only a portion of the upper half is shown since the lower half is identical to the upper half. The turbine I0 comprises an outer casing 12 of generally tubular or annular shape. a plurality of inner casing members 14 of annular shape encompassed by the outer casing I2, and a rotor 16 rotatably supported within each of the inner casing members 14, in any suitable manner. not shown.
3 and having a plurality. two in this example. of annular rows or arrays of blades 18 and 20.
Cooperatively associated with the rotor blades 18 and 20. to form two stages. for this example. for motive fluid expansion. is an equal number of blade diaphragms or annular rows of stationary blades 22 and 24, supported within the inner casing members 14. An annular grouping of stationary blades 22 or 24. comprises an integral arcuate vane segment 23.
The rotor blades 18 and are substantially similar to each other except for a gradual increase in height from left to right. and are of the unshrouded type with a radially outwardly extending vane portion 26 and a root portion 28 suitably secured to the rotor 16.
In a similar manner. the stationary blades 22 and 24 are substantially similar to each other but gradually increase in height from left to right. and are provided with a radially inwardly extending vane portion 30, a base portion 32. and an outer shroud portion 34. The outer shroud portion 34 comprises a portion of the track and channel arrangement 49 for supporting the integral vane segments 23.
As well known in the art, hot motive fluid. such as pressurized combustion gas. generated in a suitable combustion chamber. not shown. is directed through the first row of stationary vanes 22 past the rotor blades 18 and 20. in the direction indicated by the arrow 35a. with the resulting expansion of the hot motive fluid to rotate the rotor 16 about its longitudinal axis. and thence directed through a suitable outlet. not shown. located at the furthermost downstream end of the turbine 10.
In accordance with the invention. as shown by the vertical sectional view in FIG. 1. each inner casing member 14, encompassed by the outer casing 12. and having a plenum chamber 42 therebetween. supports a plurality of annular arrays of arcuate support or isolation segments 44. The arcuate support or isolation segments 44 provide the support for the outer shroud portions 34 of the stationary arcuate vane segments 23 that comprise the annular arrays of stationary blades 22 and 24. and the blade rings 46. The arcuate support seg ments 44 slid-ably mate with grooves 45 in each inner casing member 14 in a track and channel arrangement 51 to support the stationary vane segments 23 comprised of the blades 22 and 24. There is a similar track and channel arrangement 49 between the radially inner side of the arcuate support segments 44, and the vane segments 23 and the blade rings 46, for providing support therebetween.
The arcuate support segments 44 help support axially adjacent arcuate blade ring segments 46. The number of stationary vane segments 23 and the arcuate blade ring segments 46 control the number of gaps or open ings between circumferentially adjacent shroud portions 34 and between circumferentially adjacent arcuate blade ring segments 46. This aids in controlling the leakage of cooling air therepast. The arcuate ring segments 46 have a gap 76 between one another as shown in FIG. 4. The arcuate support segments 44 and the vane segments 23 do likewise. Disposed across the gap 76 between circumferentially adjacent arcuate ring segments 46 is a plate-like seal member 78. The seal member 78 is fixedly attached to one ring segment 46. and it slidingly mates with a groove 80 in its adjacent ring segment 46. The sliding arrangement between the fixedly attached seal member 78 on one ring segment 46 and its neighboring ring segment 46 permits thermal expansion and contraction of adjacent circumferentially disposed ring segments 46 without cooling fluid leakage and undesirable harmonic effects acting upon the rotor blades. 18 and 20.
Each arcuate isolation or support segment 44 is restrained however. with respect to the inner casing 14, as shown in FIGS. 1 and 2. The restraint is at a single point on its radially outer periphery of each arcuate support segment 44 to permit expansion and contraction with minimum deleterious effects therein. The furthermost upstream arcuate support segment 44 per inner casing member 14 as shown in FIG. 2. is designated 44a. It has a track and channel interlock arrangement 51 with the upstream end of its respective inner casing member 14. The upstream and downstream ends of each inner casing member 14 have radially directed flanges 82 and 84, respectively. The upstream and downstream flanges. 82 and 84, permit the support arrangements. not shown. and annular seal arrangement 43. between axially adjacent inner casing members 14. Each upstream arcuate support member 44a is restrained from circumferential movement or slippage by a radially directed lock plate 53. Each radially directed lock plate 53 is anchored to inner casing 14 by a bolt 53'. The radially directed lock plate 53 mates with a radially directed groove 86 in a lip member 87 on its arcuate support member 44a.
A support arrangement is shown in the furthermost downstream arcuate support segment 440 on inner casing member 14 which has a similar track and channel interlock arrangement 51 for support therewith. A radially directed lock plate 50 has a similar bolt 50' holding the plate 50 to the downstream side of the inner casing member 14. The lock plate 50 is seated in a radially directed groove 55 on the downstream side of the inner casing 14. The lock plate 50 extends radially inwardly and mates with a groove 57 in lip member 58 in the downstream side of arcuate support segment 44c. The lock plate 50 extends further inwardly and mates with a notch 56 disposed on the downstream lip of its respective arcuate bladering segment 46. as shown in H68. 2 and 3. The prior art arrangement for restraining circumferential dislocation of each ring segment 46, as shown in FIG. 7. was the use of a lock screw 54 disposed through the inner casing 14 and in registration with each ring segment 46. This necessitated more elaborate machining and combersome assembly and repair due to its proximity to the annular flange 84 which itself is required for assembly to its adjacent inner casing member. as shown in FIG. 1.
Disposed intermediate between the upstream and downstream arcuate support segments 44a and 440. is an annular array of arcuate support segments 44b. supported by the inner casing member l4 by a track and channel interlock arrangement 51. Each intermediately disposed arcuate segment 44b is restrained from circumferential dislocation by a bolt 48 disposed through the inner casing member l4 and being in registration with said arcuate support segment 4411.
Preventing dislocation of arcuate support segments 44 adjacent the horizontal split between the upper and lower halves of the inner casing 14 was unsatisfactorily accomplished by a retaining screw 58 of the prior art as shown in FIGS. 5 and 6. FIG. 6 shows both halves of the prior art split turbine casing designated C and D respectively. This arrangement only prevented dislocation of arcuate isolation segments 44 in one direction. The improvement is shown in FIGS. 8 and 9, wherein a horizontal joint locking plate 59 has a tang portion 60 mated into a groove 61 ofa lip member 62 on support segment 44. The locking plate 59 is held to each arcuate support segment 44 adjacent the horizontal split in the casings l4 and 12 by a bolt 63 in casing 14. Thus, the interlocking relationship between the tang 60 and groove 61 prevents circumferential dislocation in both directions, of the arcuate support segments adjacent the horizontal split in the casings l2 and 14. FIG. 9 shows both the upper and lower portions of the turbine casing, designated A and B respectively.
Thus. there is presented an improved arrangement for the restraint from circumferential dislocation of vane and blade ring support members and improved sealing therebetween. The improvement permits easier assembly and servicing of the casing, vane segments and blade rings, while eliminating more expensive drilling and threading operations required by locking arrangements of the prior art.
Although the invention has been described with a certain degree of particularity, it is intended to be exemplary only, and not in a limiting sense.
1. An axial flow turbomachine comprising:
an outer generally cylindrical casing;
a generally coaxial inner casing, said inner casing and said outer casing generally defining a plenum chamber therebetween;
an annular array of stationary blades disposed within said inner casing said stationary blades having an outer shroud portion;
a rotor having an array of rotatable blades on its periphery. said rotatable blades being mounted coaxial and adjacent said stationary blades;
an array of arcuate blade ring segments disposed radially outwardly of said rotatable blades;
said array of stationary blades comprising arcuate integral vane segments thereof;
said stationary blades being supported from said inner casing by arcuate support segments disposed on the upstream portions and intermediate portions, of said inner casing. all of said arcuate support segments and said innner casing having a track and channel interlock means therebetween, said arcuate support segments and said outer shroud portion of said stationary integral vane segments and said blade rings having a track and channel interlock means therebetween. the downstream edge of said blade rings supported by an array of arcuate support segments. each arcuate support segment having means to fixedly attach at least one point of its radially outer periphery to the inner casing to permit free circumferential expansion and contraction of said arcuate support segments;
said inner and outer casings being separable longitudinal into generally upper and lower halves;
said vane segments and blade rings being separable into generally equally segmented arcuate semiannular arrays. each semi-annular array having one of said arcuate support segments at each respective end thereof, said arcuate support segments at each end of each semi-annular array being fixedly at tached to said inner casing by a locking plate.
2. An axial flow turbomachine arrangement as recited in claim 1. wherein each of said arcuate support segments supporting said arcuate blade ring segments are interlocked with said inner casing by a generally radially directed locking member.
3. An axial flow turbomachine arrangement as recited in claim 1. wherein each of said generally radially directed locking members interlocking said inner casing and each respective arcuate blade ring segment, is fixedly attached to said inner casing. each of said generally radially directed locking members extending radially inwardly to and mating with a generally radially directed channel in each of said arcuate support segments and a notch in each of said blade rings to prevent dislocation therewith.
4. An axial flow turbomachine arrangement as recited in claim I. wherein said means to fixedly attach each of said intermediately disposed arcuate support segments to said inner casing comprises a bolt in registration therebetween.
5. An axial flow turbomachine arrangement as recited in claim 1, wherein each of said locking plates is bolted to one of said inner casing halves. a tang member on said locking plate being disposed in a groove on a lip portion on said arcuate support segment to inter lock with and prevent circumferential motion thereof. each of said locking plates being secured to an inner casing halve by a bolt.
6. An axial flow turbomachine arrangement as recited in claim I, wherein a seal plate is disposed between circumferentially adjacent blade ring members and between adjacent vane segments, to prevent excessive cooling fluid leakage therebetween.