US2007408A - Turbine - Google Patents

Description

July 9, 1935. c. A. scHELLENs TURBINE 2 Sheets-Sheet l Filed March 26, 1932 u, W .www 1mm. n /F July 9, 1935. C, A, `SQ'HELLNS 2,007,408

TURBINE Filed March 26, 1932 2 Sheets-Sheet 2 verz'or. Lf/Law..

,. Patented July 9,1935 g 'Y i oFxlvflcE,

Y ompany, Engle- VwoodyN. J.v,`a.lc'orporation'of Pelawaltrev f Y Appucetionmarch ze, 1932,l serisiNo. 601,315

" ,.110 claas# @tiene one. orl more nozzles which convert the pressureY ofthe steam into velocity and a turbine wheel having two velocity stages fromv one to theother of which the steam isV passed in succession: The

` ,invention ,is also applicable to other .types of yturbines havingaturbine wheel provided with Y twoV or more successive pressure stages.

1 ,The Vusual two-stage turbine wheel has." two vaxially'-spacecl''rows. of buckets from one tothe other of whichv rows 'thesteain is guided invsuc'- cession. A turbine drivenlocomotivei feed water `pump is subject tohigh over speeds atl times when the pump accidentally becomes'dry andthe overspeed tripping mechanism fails to operate, as may happen when the mechanismV is Knot inspected at .reasonable intervals. When Vover-speeding occurs the'connections between the turbine buckets and thewheel are subi ected to severe stresses suf jiicient, sometimes, to cause the buckets to leave the wheel. Hencean object ofthe presentinvention is the provisionr of a turbine construction which permits the buckets to ybe welded in acommercial manner to the Wheelsothat they are in eiect integrally connected so strongly `as to resist high centrifugal forces. V-

A turbine wheelV having two rows of buckets can not have its buckets welded readily tos-the r.wheel since, the .bucket rows are soi close together that Welding can not, be donelatany .commercial speed between the rows. Hence a furtherobject -ofthe invention is theprovision of'atWo-stage turbinewhaving but' one" row of buckets on'. its vlrheeho that the single row of buckets can be Vwelded readily to the wheelA while.preservingV th advantages of the tworeaction passages; "r

nitt is a further: object. of theinvention'ftolpro- 'vide a turbine wheelwitha single rowA of buckets Lwhich are, so arranged as to provide. outer-andv 4inner sets of moving reaction passages; orstages', through which the steamA passes fro'moneV side to 4the other ofthe wheeltogether witha stationary passage on one side of the Wheel for directing the steam into one'setnf reaction'passagesand a 'stationary reversing passage onthe'veother side 'of the` wheel which receivesthe steamfrom said set of reaction passages-andredirects the steam toward theilrstV sidev of the wheel. andinto -said other set of reaction-"passageang said` passages, 'or cneor mareo!l them, Amayor-may' notfprovide lthe'bowl 20 and the expandingvpassage 22.

for lthe'expansion of the steam therein, attheV will Tof the designer. l

`:lItF is also an object of the present invention 'to'direct'thesteamzto enter the sets oi reaction lpassages in ylsuch' order that the diii'erence in V5 peripheral speeds of the sets of passages is most nearlygin accord with the velocities of the steam entering the passages and, for this purpose, with the specific construction inrwhich the invention is y herein illustrated, to enter the upper portion of 10 thebucket. irst and the lower portion last. The direction of iiow of the steam' passing p through the one portion of the buckets mustbe reversedto be directed into-the other portion of .the buckets and a further object of the invention `15 isrthe .provision of a novel form` of'reversing chamber adapted for thispurpose. Affurther object of the invention is generally to improve the construction and operation of steam turbines.p Y

' Fig. lis' a sectional elevation of a steamturbine embodying. the present invention. y

Fig; 2-is'adeveloped section taken alongk line 2-2 ofFig. 1.

. 'Fig'. is a sectional side elevation of the buckets 25 of the turbine wheel. y "f Fig. 4 isa front elevation of one of the reversvingzchambers.v L Y. Y' '1 Fig. 5 isa section along line 5-5 of Fig. 4.

`rl'ig. 6` is a Fig..4.- 1 Y As/here shown; thev turbine embodying the presentv invention comprises aV casing'4 l0 having a a steam'chest I2 into which steam is Vadmitted 4through-th'epipe I4. The steam chest is in com- 35 munication with a' block I6 havingY a row of Vpassages'. I8 therein which direct the steam intothe 'wheel 'buckets.- As herein shown, the passages f'l 8 fconstitute expanding nozzles each j comprising A 40 :valve `23 isprovided which is adapted to be'closed tby'over-speed mechanism, `not shown, when the Afturbinevspeed'becomes excessively high and shut' off the supplyY of steam to the nozzles. The nozzles'discharge steam through the turbine buckets 45 lhereinafter toV be described and finally into-the Awheel chamber 24.01 the casing from which the exhaust steamis discharged through the outlet 16..' `The wheel chamber is closed by the removlablezcover 28. A-turbine wheel '30.is located in 50 thewheelchamber andfcomprises a radialdisc y32fhaving al central hub. that is fixed tothe ldriveshaft 36. Thedrive shaft is suitably supported `in bearings38,one of which is here shown, Pand connected to the centrifugal pump or other section taken along line 6 6 of 30,

power` consuming device not herein shown. The wheel disc is provided with an enlarged rim 40 in which an endless peripheral bucket groove 42 is formed, the side walls of the groove being parallel. 'I'he peripheral faces 44 of the rim on the opposite sides of the groove are inclined inwardly toward the shaft for a purpose to be explained hereinafter. The turbine wheel is provided with a series of buckets 46 which nest one within the other and have shanks or roots 48 that are located in the bucket groove 42 and are weldedV toV the wheel. The opposite faces of the roots of'the` buckets are provided with grooves 50 which areY located about flush with the top faces of the wheel rim on opposite sides of thegroove. The material 0f the wheel rim is peened into the grooves 50 whereby to hold the buckets firmly in position during the welding operation; The buckets are then welded to the rim by applying welding material 52 to the inclined faces 44 of the rim and to the buckets on both sides of the bucket, as illustrated in Fig. 1, thereby :building up the rim on both sides of the buckets and forming an effective `bond between the buckets andthe rim so that the buckets and rim are in effect one integral mass. The body of the buckets, above theroots,

Yare formed with upwardly and outwardly inclined bottom faces 53 which oppose the rim faces 44 and cooperate therewith to form V-shaped channels in which the welding material can bedeposited to form a strong bond between the wheel and buckets. Y i

Each bucket is provided with a shroud plate 56 at the top and av second shroud plate 58 in the middle thereof, .each shroud plate extending behind the bucket and nesting against. thefront face of the next adjacent bucket so that the buckets are provided with isolated outer andinner steam reaction passages 60 .and 62, respectively, the inner passages being radially longer than thc outer passages. 'I'he oppositesides of the middle shroud plates 58 are provided with peripheral grooves 6 4 for the purpose of lightening the buckets. The upper shroud plates 56 form in effect an endless shroud which is machined oi to provide an apex 65 in the median line or at the outermost diameter of the wheel. The wheel is balanced by removing the material where necessary from the apex 65, where the least material has the most effect on the balance of the wheel. The wheel is located in its Ychamber withvthe buckets adjacent the nozzles I8 so that the steam discharged from the nozzles mustl pass through the outer steam passagesv 60 of the buckets, thereby to rotate the wheel. The steam leaving the outer passages of the buckets isdirected through a series of reversing chambers 66 which confront the nozzles on the opposite sides of the wheel and by them is directed into the inner steam passages 62 of the buckets.

The reversing chambers are identical. Each comprises a block 68 the outer end of which is located in an acruate groove 10 of the cover plate 28 of the wheel chamber and has a fiat end face 12 that is seated in the bottom of said groove. The block is provided with astud bolt 14 which projects through the cover plate and has a nut screw-threaded thereon whereby to hold the block removably in position. Each block is provided with arcuate side walls 18 and 80 curved in the direction of rotation of the'wheel, and s0 arranged that the blocks seat one against the other, where- -by the open-reversing chamber 6601 one block is closed by the next adjacent block. Theopen reversing chamber for theiirst block 0f the series is covered by a cover member 82 which is separately secured to the turbine casing in the same manner as the blocks 68. The reversing chamber 66 of each block comprises relatively straight upper and lower passages 84 and 86 which are separated by a wall 88 and are connected at the rear by an arcuate connecting passage 90, the cross-sectional area of the passagespreferably increasing progressively from the inlet of the upper passage to the 'exit of theV lower 'passage to Acompensate for loss in steam speed in the passage due to friction therein. The entrance to the chamber is at a somewhat different angle than the discharge fromthe chamber s0 that the steam is taken from the outer portion of the buckets and is` delivered to the inner portion without shock, the angle of the lip 92 of the wall 18 for the ,upper passage beinggreater than that of the lip 94 of theV lower passage, the material of the wall 18 being filed away, or otherwise removed, at the lip 92, as indicated by the-dotted lines, Fig. 5, `'for thispul'posef. l

'With the constructionv above described one row of buckets and the reversing chambers take the place of the usual two rowsof buckets, Ithereby reducing the cost of the turbine and also permitting the buckets to be welded economically to'the wheel, so that they can resist successfully the high centrifugal stresses to which they may be subjected if the wheel overspeeds.

The weight of the wheel is also lighter than that of the usual two-row type, which is important, especially in high speed turbines. With the type of turbine illustrated, there is no harmful axial thrustnn the wheel since :the steam pressures on opposite sides of the wheel are the same, there being n0 particular-expansion of steam in the buckets. 'Ihe efficiency of the turbine as thus constructed has been found to be about the same as with the usual two-velocity stage construction. With the particular type of turbine herein chosen to illustrate the invention, the main expansion of the steam from the high tothe exhaust pressure occurs in the nozzles I8, the steam passing through the bucket passages and the reversing chambers 66 with little or no drop in pressure. The proportion of the reversing chambers may obviously be such as to permit of a drop in pressure therein. i Or the bucket passages can be made toexpand the ste'am as it passes therethrough, as in the Parsons vtype of turbine in which case the nozzles I8 andl the reversing chambers may not have expanding passages; The

application of the invention'is the same regardless of where the steam is expanded.

Iclaim:V 1. A turbine comprisinga turbine wheel having a row of buckets provided with outer and inner passages therebetween, a nozzle which directs steam into oneof said passages, and a series of steam reversing members which vreceive the steam from said passage and reverse the direction of iiow thereof anddirect it into said other vand which closes the open reversing chamber o the end reversing memberoftheseries. 1 3. A turbine comprising 4a casing having a wheel compartment, a turbine wheel therein having aro'w of buckets provided withouter and inverse to the ner steam passages therebetween, nozzles which direct steam into one of said passages, said casing having a Wall confronting said Wheel opposite said nozzles and provided With an arcuate groove therein, a series of separate identical reversing blocks located inV said'groove in contiguous relation, each block having a generally- U-shaped passage therein provided with an inlet opposite'the exit of one bucket passage and an exit opposite theinlet of the other bucket passage, ther passage between its inlet and exit being open on the side facing' the Wheel, and the contiguous block overlying said open passage and constituting'the closure therefor, and a passage-free cover plate overlyingV the open passageV of the end block of the series. l Y

4. `In a turbine havinga bucket wheel, a nozzle for directing steam through the buckets, and a series of separate identical but nested reversing series of separate identical but nested reversing blocks each having a reversingpassage having aj reverse bend in the middle, an inlet confronting the bucket exits and an exit confronting the bucket inlets and arranged torreceive steam from thebuckets and to redirect the steam to re-pass through the buckets, said passages being curved in a direction axially of the WheeLWhereby to increase the dimensions of saidy passages trans- Wheel as they approach said reverse bends.

6. In a turbine having'a bucket Wheel, a nozzle for directing steam through the buckets, and a series Aof separate identical but nested reversing blocks each having a reversing passage having a reverse bend in the middle, an inlet confronting theY bucket exits and an exit confronting the bucket inlets'and arranged to receive steam from the buckets and `to redirectrthe steam to re-pass through the,` buckets, the dimension of each passage transverse to the wheel increasing as the passage approaches the bend'.

'7. In aturbine having a bucket wheel, a nozzle for directing steam through thebuckets, and a.

series of separate identical but nested reversing blocks each having a reversing' passage having a reverse bend in the middle, an inlet confrontingV the `bucket exits and an exit confronting the bucket inlets and arranged to receive steam from the buckets and to redirect the steam to re-pass through the buckets, the dimension of each passage transverse to the wheel increasing as the passage approaches the bend and the dimension lof each passage radially of the Wheel decreasing as the passage approaches the bend.

8. In a turbine having a bucket wheel, a nozzle for directing steam through the buckets, and a series of separateidentical but nested reversing blocks each havingV therein a reversing passage having a reverse bend in the middle, van inlet confronting the bucket exits and an exit confronting the bucket inlets and arranged to receive steam from the buckets and to redirect the steamto rep'ass through the buckets, the nested faces of said blocks vbeing arcuate and cylindrical and the reversing passages being openV in the faces of said blocks. Y

9. In a turbine having a bucket wheel, a nozzle for directing steam through the buckets, and a series of separate identical but 4nested reversing blocks each .having therein a reversing passage having a reverse bend in the middle, an inlet confronting the bucket exits and an exit confronting the bucket inlets and arranged to receive cylindrical steam from the buckets and to redirect the steam to re-pass throughthe buckets, the nested faces of said blocks being arcuate and cylindrical, one side of each passage being open in a cylindrical nesting face thereof and .one block constituting a cover for the open side of the passage in the adjacent block. Y

, 10, In a turbine having a bucket Wheel, a nozzle Vfor directing steam through the buckets, and a. Y

series `of, separate identical but nested reversing blocks each having a reversing passage having a reverse bend in the middle, an. inlet confronting the bucket exits andV an exit confronting the bucket inlets and? arranged to receive steam from the buckets and to redirect the steam to re-pass through the buckets, the nested faces of said `blocks being arcuate andcylindrical, one side of each passage being open in a nesting facethereof,

Vand one block constituting a cover for the open side of the passagein the adjacent block, the end portion of the bottom Wall of the block opposite the open face of the. passageV being inclined with respect to the median line of the passage.

CHRISTOPHER A. SCI-IELLENS.

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