US2980396A - Stator construction for turbine engines - Google Patents

Description

A ril 18, 1961 E. N. MOVSESIAN STATOR CONSTRUCTION FOR TURBINE ENGINES Filed June 29, 1959 R m w W.

'Iill III" -m 0. w M N. w W 0 5 m a f STATOR CONSTRUCTION FOR TURBINE ENGINES Edward Neshan Movsesian, Stoneham, Mass, assignor to This invention relates to a stator construction for turbine engines, and more particularly to an improved construction for mounting segmented guide vane assemblies in a stator structure.

Guide vane assemblies commonly used in turbine engines comprise a row of vanes circumferentially spaced about supporting shroud rings, which are secured to radially inner and/or outer ends of the vanes. It has been found desirable to divide such an assembly into a plurality of arcuate segments, so that damaged vanes can be re placed in small groups, without reworking or replacing the entire assembly.

In engines having casings split into semi-cylindrical halves, i tis convenient to assemble the vane assembly halves, it is convenient to assemble the vane assembly segments by sliding them circumferentially into grooves formed in semi-circular rabbets in the casing halves. Each segment may be inserted in the grooves at the part-- ing line and slid circumferentially into position. A key may be placed over the grooves and segments at the parting line to restrain relative rotation of the vane assembly after the casing halves are assembled.

However, grooved rabbet structures have not been convenient for use in integral annular casings, because of the difiiculty of loading the vane assembly segments in the grooves. Alternative means of fastening the segments in the casing may be used, such as threaded fasteners, but generally the assembly and disassembly procedures are relatively involved and time-consuming, and do not afford as sturdy a construction as the grooved rabbet arrangement.

It is an object of this invention to provide an improved stator construction in which segmented arcuate guide vane assemblies may be easily and rapidly assembled and disassembled in grooved rabbets of an integral annular casing.

It is a further object of this invention to provide a stator construction including improved means for securing an assembly of arcuate guide vane segments in grooved rabbets of an annular casing, facilitating assembly and disassembly of the segments in the casing.

Other objects and advantages of my invention will become apparent from the following description.

Briefly stated, in accordance with one aspect thereof, my invention may be carried out by providing a first annular casing section having an annular recess with spaced parallel grooved rabbets extending circumferentially thereabout, for receiving segmented vane assemblies in circumferentially slidable relationship. A loading slot is formed in the casing in communication with the recess to permit insertion of a vane assembly segment into the recess. The loading slot has sufficient arc length to permit the insertion of one segment at a time. The segment is then slid circumferentially into and along the grooves to its assembled position, and further segments are similarly inserted until a full annular'vane assembly is completed.

My invention further comprehends the provision of an arcuate locking strip of congruent form with the loading slot, which is inserted in the loading slot to retain the vane segments in the casing after assembly. The stator assembly is completed by securing a further casing section to the first casing section. The second casing section overlies the locking strip and prevents its displacement from the loading slot. The circumferential edges of the locking strip and loading slot extend radially, or diverge outwardly of the casing, to secure the locking strip against falling radially into the engine.

The locking strip is preferably formed with a groove along an arcuate surface mating with vane segments which are located adjacent to the loading slot upon completion of the assembly, so that these segments are radially supported along both edges in the same manner as the remaining segments.

The locking strip is also preferably formed with a locking lug extending into a mating slot cut in a surface of a vane segment located adjacent to the loading slot, to prevent rotation of the vane segments relative to the casing section by working fluid forces after assembly.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which I regard as my invention, it is believed that the invention may be more clearly understood from the following description of a preferred embodiment, referring to the drawings, in which:

Fig. 1 is an elevation in section of a fragmentary portion of a turbine engine incorporating a preferred embodiment of my improved stator construction, taken on a plane passing through the engine axis;

Fig. 2 is a view taken along line 2-2 in Fig. 1, looking in the direction of the arrows;

Fig. 3 is a view similar to Fig. l, but taken on a different plane passing through the engine axis;

Fig. 4 is a pictorial view of a vane assembly segment and a locking strip, removed from the engine;

Fig. 5 is an elevation in section of fragmentary portions of the members of Fig. 4, on an enlarged scale; and

Fig. 6 is a view taken along line 6-6 in Fig. 5, looking in the direction of the arrows.

Referring to the drawings, a turbine engine of a conventional type is generally designated at 1. The engine includes one or more circumferentially-spaced rows of rotor blades 2 mounted upon the periphery of a disc 3 for rotation about a common axis. A duct 4 for guiding motive fluid in the direction shown by the arrow through blades 2 is partially defined by an inner shroud ring 5, and by an annular engine casing comprising at least a first section 6 and a second section 7. Radial abutting flanges 8 and 9 are formed about casing sections 6 and 7, respectively, and are joined in fluid-sealing engagement by means of a row of bolts 10 and nuts 11, or by any desired fastening means. Rows of openings 12 and 13 are formed through flanges 8 and 9, respectively, to receive bolts 10.

An arrangement of this general kind may be used for a compressor or a turbine in an engine, blades 2 being appropriately formed for the purpose intended. The engine structure forms no part of the present invention, and will not be further described.

In order to guide fluid flowing through duct 4 in the most advantageous angular path for exit from blades 2, and for entry into subsequent rows or stages of rotor blades, a circumferentially-spaced row of guide vanes 15 is provided, extending across duct 4. Guide vanes 15 are secured near outer ends 16 thereof in mating openings formed in'rings 7 and 18 of a composite box-section shroud ring generally designated 19. The vanes are secured in rings 17 and 18'by means of brazing, or in any suitable manner. Shroud ring 19 is divided into a number of segments 20 and 20:: (Figs. 2 and 4), to peromit replacement of a small of wear or damage to individual vanes.

tion' thus far described is conventional, and forms no part of thepresent invention.

group of vanes in theevent Present practice provides for mounting vane assembly rshroud segments; in :ajcasing section by ameans-ioffgrooyed -rabbet structures, in order to afiord'asturdy structure,

-WhlCh11'kaYib6 easily and quickly assembled and -disassembled. .However, this arrangement has previously required that the casing section beisplit into semi-cylindrical halves on'a'plane passing throughthe engine axis,

to permit insertion of the shroud segments in the grooves of the rabbets. According to my invention, conventional grooved rabbet structures are used'in'an integral annular casing section'6. For this purpose, circumferential 'rabbetsf22'and23-are formed on the inner surface 'of .casing section 6 (see Figsxl andf3) and are circumferentially grooved at, 24 and 25, respectively. A circumferential-recess 26is thus formed in casing section j t ,6 to receive shroud ring 19. p 7

. i Shroud ring 19 is'formed with axially-projecting flanges r 27 for circumferential sliding engagement with grooves 24 and 25, by folding the axial edgm of ring 17' into radial flanges'28 and U-shapedreturn portions 29, over the edges of ring 18 (seeFigs. 4 and 5). The construc- 1 of itself In order'tocarry out my -invention,'I form an arcuate .loading slot 30-through 'rabbet 22 (Figs; 1 and'2) extending along an arcuate portion of the rabbet through an arc length at least as. great as 'thatofan individual shroud 'segment or 20a. be assembled in casing section 6 'by inserting them indi- .vidually throughtloading slot'3l) inan axial direction 7 until a flange 27: engages grooveZS in rabbet 23. Each segment 20is then slid circumferentially'along groove 25, also engaging and sliding in groove 24 of rab-bet 22 after leaving the loading slot. The insertion of a last shroud segment ZGain-the loading slot-completes the assembly The 1 shroud segments may of shroud ring '19, and of a complete' circumferential row of vanesuls in recess 26 of casing section 6.

In order to retain shroud 'ring segments 20 in place in recess 26, and to prevent their-rotation relatiyeto the casing after assembly, I provide an arcuate locking strip 32.7 The locking strip is congruent with loading slot'30, and is identical in cross section with the portion of rabbet .22 milled out to form the loading slot;- it includes a groove 33 receiving flange 27 of the last shroud segment 20a. Insertion of'the lockingstrip into loadingslot 30 7 thus. efiectively completes the annulus of'rabbet 22,- so

that all of the shroud segments aresupported along both flanges -27.

Radial movement ferentiaJly-spaced edges 34 of the locking strip and mating .circumferentially-spaceda edges 35 of the loading slot, on planes diverging away from theengine axis as shown in Fig. 2, or on planes radial to the engine axis. p a 19 relative to notch.37 is cut throughtan adjacent one of flanges 27 and through'ring 18 ofse'grnent 20a,-to receive stop lug 36.

flanges by means of bolts 10 and nuts 11. This completes 70 V a row of blades mounted for rotation in said duct, and a theassembly oi the stator'structure.

of locking strip 32;out of loading, slotfifland into duct 4 isprevented by'forming circum- '1 have provided an improved stator construction by means i of which segmented vane assemblies are supported and secured in. grdoitedrabbets of: an integral annular casing 7 section, and which affords facility of assembly and disas- 'sembly. No additional fasteners, other than those used to secure the casing sections, are required in the assembly, and this minimizes the labor necessary in assembly and maintenance. With the casing sections parted, the segmented vane assemblies-and locking strip may be manual- -lyassembledin the casing,-or removed for inspection and freplacement, without the use of tools of any kind.

of blades mounted for rotation in said duct, and a row of guide vanes in said ductfor guidinga flow of working fluid therein, a stator construction for mountingtsaid vanes in said casing, comprising, in combination; an annular shroud ring secured to an end'of each of said vanes, said shroud ring divided circumferentially into a plurality of arcuate segments, said casing formed with a recess extending circumferentially ther'eabout for receiving said shroud ring, a pairof spaced-apart circumferentially-extending grooves formed in said recess'for receiving said segments in circumferentially-slidable supporting engagement, said casing formed with a'loading slot communicating with said recess for receivingsaid'segmentsindividually for movement into slidable engagement with said grooves, such that said segments may :be. individually inserted into said recess through said loadingslot and slid'along said grooves to assemble saidshroud ring'as a complete annulus in said recess. I 1 I f Y 2. In a. turbine engine of the type comprising an annular casing partiallydefining a working fluid duct, a row of blades mounted for rotation'in said duct, and a row of guide vanes in said duct for guiding a flowof working fluid therein; a stator construction for mounting said vanes in said casing, comprising, in: combination; and

annular shroud ring secured to amend of each of said vanes, isaid shroud ring divided'circumferentially into a plurality of arcuate segments, a pair of axially-spaced rabbets extending circumferentially about said casing and defining arecess therewith, each of said rabb'ets formed with a groove'extending circumferentially thereabout for receiving said shroud ring in circumferentially slidable supporting engagement, one ofsaid rab-bets-formed with a circumferentially-extending arcuate loading slot communieating with said recess for receiving said segments individually therein, such that said segments may be individually inserted into said recess through said loading slot and slid along said grooves to assemble said shroud ring as a verging outwardly from said casing, such that said edges cooperate to restrain said locking strip against movement relative to said loading slot in a direction transverse to said one direction.

5. In a turbine engine of the type comprising an annular casing partially defining a working fluid duct, said casing including'a pairxof axially abutting casing sections,

row of guide vanes in' said'duct for, guiding a flow of working fluid thereinra stator construction for mounting said-vanes in said casing, comprising,gin-combination;

an annular shroud ring secured to an end of each of said vanes, said shroud ring divided circumferentially into a plurality of arcuate segments, a pair of axially-spaced rabbets extending circumferentially about a first one of said pair of easing sections and defining a recess therewith, each of said rabbets formed with a groove extending circumferentially thereabout for receiving said shroud ring in circumferentially slidable supporting engagement, one of said rabbets formed with a circumferentially-extending arcuate loading slot communicating with said recess for receiving said segments individually therein, such that said segments may be individually inserted into said recess through said loading slot and slid along said grooves to assemble said shroud ring as a complete annulus in said recess, and an arcuate locking strip congruent with said loading slot and receiable therein by sliding in one direction to prevent disassembly of said segments from said casing through said loading slot, the other of said casing sections overlying said loading slot and said locking strip to prevent movement of said locking strip relative to said loading slot in said one direction.

6. A stator construction as recited in claim 5, in which said locking strip and said loading slot are formed with circumferential edges which lie in planes which diverge outwardly from said casing, such that said circumferential edges cooperate to restrain said locking strip against movement relative to said loading slot in a direction transverse to said one direction.

7. A stator construction as recited in claim 5, said locking strip being formed with a lug, and one of said segments located in said recess adjacent to said loading slot being formed with a notch receiving said lug and cooperating therewith to prevent circumferential sliding of said shroud ring in said grooves subsequent to assembly of said stator construction.

References Cited in the file of this patent UNITED STATES PATENTS 2,654,566 Boyd et a1. Oct. 6, 1953 FOREIGN PATENTS 760,884 Great Britain Nov. 7, 1956 777,835 Great Britain June 26, 1957

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