US2978223A - Turbine apparatus - Google Patents

Description

April 4, 1961 W. E. KEENEY ETAL TURBINE APPARATUS Filed Feb. 2, 1959 I IIII INV'E NTORS WILLIAM E'.KEENEY WILLIAM R.BERRY ALVI L. sTocK BY 9 1 tends transversely ofthe rotor-axis and they 'arediyided TURBINE Arr William E. Keeney, Haverto'wn, Pa, William R. Berry, Camden, N.J., and Alvin L. Stock, Prospect Park, Pa, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pin, a corporation of Pennsylvania Filed Feb. 2, 195a, Ser. No. 790,496

Claims. c1. 253-39 This invention relates to elastic fluid turbine apparatus, especially steam turbines, and more particularly to an improved construction of the casing, the valve chest,

and the passagewaysbetweenthe valve chest and the provided with governor-controlled valves that are sequentially movable to open and close a plurality of flow paths between the chest and the passageways. During partload operation, for example, some valves will be open, otherswill be closed, and steam will flow'through those passageways open to the valve chest.

Where apparatus of the type setforth experiences fre:

qt ient load changes or frequent starting and stopping, and the inlet steam temperature is at least 850 F., fatigue failures, in the casing flanges and the nozzleboxes may be caused whentheir component parts aresubject'ecl to repeated, alternately large and small temperature jdiiierentials. This condition is termed thermal cycling? and is thought to" be the major cause of fatigue failures in Casing and nozzle'box parts. I a

The construction disclosed in U.S,' Patent 2,527,445, issued October 24, 1950, toGeorge-W'. Pentheny and pableof coping with the problemof thermal cycling, even 1 for inletsteam temperatures above. 12 0 0" F. For commercialreasons,however, itisfdesirable to provide an arrangement as efiective as .Pen'thenys butiless expensive t to construct. More particularly, the problemhasiarisen in turbines of single-wall casing construction and driven by steamj'having an inlet temperature in rthe'rangeof be- According" .to the present inventiom'thelcasing is of v tubular, single-wall construction withan opening formed therein. Anfinteg'rally castacavernous body is provided for conducting the elastic fiuid to nozzle 'grou'pswithin thecasing; The cavernous body, which may be of higher. strength material than the casing, 'compfisesavalve chest andwall structure including partitions definingfpassageways or'noz'zle boxes between the chest and the nozzle groups} The valve chest is formed integrally with the wall structure, as is a "circumferentially and, axially exthe casing, and

tending :fiange which his the'opening in is joined to the margin thereof by welding.

, 2,978,223 Patented Apr. 4, 1961 Another condition which imposes bending stresses on assigned to the assignee of the present invention, isca- I The passageways are arranged in a series which ex- V into at least-two groupsiwhich are spaced from each other, as well as from the wall ofthepcasing. Thisaarfrangement permits portio'nsot thewall structure connect ing, the partitions teas grojup great-exp ns in without, imposing force ire'ction a .ings ii) as therearenozzle' groups 3i), Inthis ernbodi ment, there in .SlX.Q1 JH ll'l gS f'@ and six nozzle groups.- i ed n a horizontal ag;-

results when one partition undergoes greater thermal expansion than a neighboring partition in the same group.

the cure for this condition it is necessary to mention that it is caused during part-load operation wherein a partition common to an open and a closed passageway is heated by the steam flowing through the open passageway, and the other partition of the closed passageway is unheated. In accordance with the invention, each group of passageways has conduit means providing restricted steam communication between its passageways so that the temperature difference between its partitions will be minirnized. When, in operation, at least one passageway of a group has fluid passing therethrough and there is at least one passageway of the same group closed to the valve chest, a small quantity of fluid bleeds from the open passageway into the closed passageway in order to hea t its surrounding wall structure. The detrimental effects of'a large temperature difference between the partitions are thereby avoided.

The various objects, features and advantages of the invention will appear more fully from the detailed de 'scription which follows, taken in connection with the ac- Fig. 2 is a transverse sectional view taken on line H -II of Fig. 1;

Fig. 3 is an exploded, perspective view of the appar a tussof Fig. l, but with the nozzle groups removed; and, 1 Fig. 4 is a horizontal sectional view taken along line IVIV of Fig. 2.

Referring to the drawing in detail, thelinvention'is.

applied to an axial-flow steam turbine comprising a'cylinder or casing it which is formed about a horizontal axis and includes anjupper half 12 and a lowerhalf 14, these halves having'respectivefianges 16and18; The

casing halves are joined together at the flanges by suitable boltsandhavea rotor 20 journalled therein and c0- "axially aligned therewith, A plurality of stages for extracting energy frornthesteamjis conventicmally provided 1 lay-cooperating, annular rows of blades, 'generallyindiesteem 22. In orderto minimizetheleakage of steam I from theinlet end; of the casing 10, the usual annular seals 26 are provided betweenthe'rotor and casing parts v Pressurized steam is conducted through an opening inthe upper casing half 12 to groups oino'zzles an, ar-

ranged in an annular array upstream of'the first stage blading by I1l6&11S. Of: Zi. cavernous body 28, the latter.

beinglof integraleonStruction andincludingz, ayalve chest 32, walistructure'fi and acircumierentiallyand axially extending, arcuate flange memberiie. :The flange member 36 is adapted to iit a similar shapedopening .37 in theupper casing half 12 and their respective man ginal portions are joinedtogether by welding. The loation of the welded jointwill be discussed. hereinafter in greater detail.

.: Ihe'valv'e GhSP t 3 2' has inletopenings33, "adapted for.

connection to "3T.-SO11'Y:C6 of. pressurized steam such as a boiler (notgshown), .and also has "as many outlet open- These openings 4% are air .t'l' extendsj'tr-ansverselyespec to the? rotor axis Preliminary to describing a I, The valve -chestlsz.is fnrtherfprovide'd*with ka'l I valve "42 for eachoutlet'ope'ning}itbthese valvesbeing carried by a vertically movable, horizontal lift bar 44. Movement of the lift bar 44 moves the valves 42 in succession to open and close the openings 40, all of which is well knownin the art. s

The primary function of the wall structure 34.is to conduct the elastic fiuidfrom the outlet openings 40 in the valve chest 32 to the nozzle groups 30. Since some of the valves 42 may be in position to close some openings 40, while other openings are opened to the valve chest 32, it is desirable for the wall structure 34 to define a plurality of passageways 48 downstream of the chest between associated openings and nozzle groups. To this end, there is a series of horizontally spaced, internal partitions 46 included in the wall structure 34, which series extends transversely of the rotor axis and defines fluid passageways 48. The lower casing half 14 is provided with two passageway extensions 49 for the purpose of completing the means for conducting steam from the valve chest 32 to the two nozzle groups 30 in the lower casing half 14. A centrally disposed pair of partitions 46 also define a space 50 which divides the passageways 48 into two groups 52 and 54. The end partitions 46 of the series are arranged in spaced relationship with the interior walls of the upper casing half 12. so that, as viewed in Fig. 2, there are left and right spaces 56 and 58, respectively, between the wall strucwhich members 59 extend transversely of the rotor axis and connect together the partitions 46 of each group. (See Fig. 4.) Unlike prior art structures, the members 59 can elongate due to thermal expansion without buckling or damaging the casing because the spaces 50, 56 and S8 permit the unresisted elongation of the members 59 of either or both groups. The elimination of repeated stressing of the rigid casing 10 and the wall structure 34 prevents their failure and avoids difiicult and costly repairs. Additionally, the wall structure 34 may be made from a stronger, through more expensive, material, since the wall structure is made separately from the upper casing half 12. Furthermore, the spaces 56 and 58 are provided without having to use a coring process during casting of the body 28, as is required for making the space 50.

As mentioned previously, the cavernous body 28 includes a flange member 36 formed integrally with the wall structure 34 and welded to portions of the upper casing half bounding the opening 37 therein. It is noteworthy that the flange member. 36 is of arcuate'shape and extends axially and circumferentially about the retor axis, as do the surrounding wall portions to which it is welded. The line of jointure between welded parts is axially and circumferentially aligned with the wall portions bounding the opening 37 in order to preserve the axial integrity of the upper casing half 12. As can be seen in Fig. 2, wherein the flange member 36 is mostly shown in dotted arcuate lines, the partitions 46 reinforce the wall structure 34 in axial direction, since portions of the partitions 46 are in axial alignment with the upper casing half 12, the welded joint, and the flange member 36. This feature can be best appreciated by now referring to Fig. 1 and visualizing steam forces within the casing 10' operating in axial, outwardly opposite directions on the end walls thereof; these forces tend to separate the easing into two halves along a circumferential line extending through the opening 37. By

" placing the welded joint and the partitions 46in axial alignment with surrounding portions of the upper cas-I ing half 12 there is no moment arm provided, which would impose bendingforces on the joint; The cavernous bedyQB. furtherincludes conduit means,

such as *an inte rnal nifold 6t},- providingrestricted which may be used for forming the manifold 60 it is most conveniently formed during the casting of the cavernous body 28 by a coring process that is well known in the foundry art. The purpose of the manifold 60 is to bleed a small quantity of inlet steam from any passageway 48 open to the valve chest 32 and deliver it to the closed or inactive passageways in the same group in order to heat their wall structure. Preheating of the wall structure prevents it from suffering a thermal shock, that is, a large temperature gradient in a short period of time, as a result of the sudden opening of the closed passageway and introducing high temperature steam thereto. Preheating also minimizes the temperature difference between the partitions 46 of a closed passageway in the situation where one of its partitions is in common with an open passageway through which hot steam is flowing. Thus, the partitions 4-6 of a closed passageway undergo a similar amount of thermal expansion and the portions of the wall members 59 connecting them do not warp.

Referring again to Fig. 2, it will be noted that the valves 42 associated with the right-hand group of passageways 48 are arranged to open in succession from left to right, and it follows that elastic fluid will flow through the left-hand passageway before the other two in that group. During part-load operation, forexample, the common partition 46 between an open and closed passageway, would be much hotter than the other partition of the closed passageway were it not for the small quantity of steam issuing from the manifold 60 into the closed passageway. During frequent load changes of a turbine not having such means for heating the closed passageways, a condition known as thermal cycling may be caused, wherein one passageway will be continually open to the valve chest 32, and an adjacent passageway will be alternately opened and closed to the valve chest, thus subjecting the portions of the wall members 59 connecting the partitions of the alternately opened and closed passageway to alternating bending moments. Without preheating, thermal cycling can cause a fatigue failure in this portion of the wall member '59. The manifold 60 provides a solution to this problem.

From the foregoing, it will be apparent that the spacing of the passageways 48 from the upper casing half 12 prevents buckling of the members 59 and the transfer of forces to the casing when the members 59 elongate due to, thermal expansion; the preheating of the passage ways 48, by means of the manifold 60,reduces the temperat'ure difference between adjacent partitions 46 and minimizes the chances of the wall members 59 failing from fatigue; and the structural arrangement lends itself well to inexpensive fabrication, while not impairing the strength of the casing 10 for resisting axial forces tending to separate the casing in two halves along a circumferential line through the opening 37. 7

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without-departing from the spirit thereof.

What is claimed is:

1. In an elastic-fluid turbine, a casing, a rotor, blading carried by the rotor and the casing, said casing including a wall portion formed about the rotor axis and being exteriorly of the casing, said conducting means compris ing a plurality of nozzle groups, a valve'chest, and Wall c ludingan exterior surface portion which fits said open; ingand is joined to the margin of said wall portion communication between the passageways48 of each of.

i two groups 52 and- S l Qfthe various methods structure integrally formed with said valve chest and defining a series; of fluid passageways between the chest and each of the nozzle groups, said wall'structure. in-

bounding said opening-said wall structure including; a;

series of partitions which are spaced from each other and the casing, said series extending transversely with respect to said rotor axis, there being two spaced partitions disposed between at least one pair of neighboring passageways.

2. In an axial-flow elastic-fluid turbine, a casing, a rotor having a row of blades, said casing including a wall portion formed about the rotor axis and being provided with an opening in said wall portion, an annular array of nozzle groups positioned upstream of said blades, a cavernous body extending through said opening for conducting elastic fluid to the nozzle groups from a source of pressurized fluid exteriorly of the casing, said body being integrally formed and comprising a valve chest, wall structure connected to said valve chest and defining a series of fluid passageways downstream of the chest, and an axially and circumferentially extending flange member connected to said wall structure and fitting said opening, said wall structure including a series of partitions which are spaced from each other and the casing, said series extending transversely with respect to said rotor axis, there being two spaced partitions disposed between at least one pair of neighboring passageways, the margin of said flange member and the margin of said wall portion bounding the opening being connected together along a line of jointure that is axially and circumferentially aligned with said wall portion, said flange member, and portions of said partitions.

3. In an axial-flow elastic-fluid turbine, a casing, a rotor, said casing including a tubular wall portion formed about the rotor axis and being provided with an arcuate opening in said wall portion, means including an annular array of nozzle groups and a cavernous body extending through said opening for conducting elastic fluid from the exterior to the interior of the casing, said body including a valve chest, wall structure integrally formed with said valve chest and defining a series of fluid passageways extending from the chest to the respective nozzle groups, and means connecting said wall structure to said tubular portion adjacent said opening, said wall structure including a series of horizontally spaced partitions which extends transversely with respect to said' rotor axis, there being two spaced partitions centrally disposed in said series between at least one pair of neighboring passageways, said two spaced partitions dividing the series into two groups each comprising a plurality of passageways, and means providing restricted communication between the passageways of each group.

4. In an axial-flow steam turbine, a horizontal-axis rotor, a casing, blading carried by the rotor and the casing, said casing having an opening formed therein, an annular array of arcuate nozzle groups positioned upstream of the blading, a cavernous body extending through said opening for conducting steam to the nozzle groups, a welded connection between the body and a portion of said casing bounding the opening therein; said body comprising a valve chest having an inlet opening and as many outlet openings as there are nozzle groups, wall structure including horizontally spaced partitions integrally formed with'said valve chest and defining steam passageways downstream of the respective outlet openings, valves for the respective outlet openings movable in succession to open and close said outlet openings, there being two partitions defining a space between at least two groups of neighboring passageways, and conduit means formed in said body providing restricted steam communication between the passageways of each group. a

5. In an axial-flow steam turbine, a horizontal-axis rotor, a casing including an upper half and a lower half, blading carried by the rotor and the casing, said upper casing half having an opening formed therein, an annular array of arcuate nozzle groups positioned upstream of the blading, a cavernous body extending through said opening for conducting steam to the nozzle groups; said body comprising a valve chest having an inlet opening and as many outlet openings as there are nozzle groups, valves for the respective outlet openings movable in succession to open and close said outlet openings, wall structure including horizontally spaced partitions integrally formed with said valve chest and defining steam passageways, there being one passageway between respective ones of said outlet openings and said nozzle groups, and an axially and circumferentially extending flange member formed integrally with said wall structure to fit the opening in said upper casing half and being joined to the margin of said upper casing half bounding the opening therein, said partitions being spaced from said upper casing half, there being two partitions defining a space between two groups of neighboring passageways, and conduit means formed in said body providing restricted steam communication between the passageways of each group.

References Cited in the file of this patent UNITED STATES PATENTS 2,294,127 Pentheny Aug. 25, 1942 2,304,993 Franck Dec. 15, 1942 2,308,897 Stearns Ian. 19, 1943

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