US2531178A - Frame structure for turbinegenerator prime movers - Google Patents

Description

New 21, 1950 F. H. VAN NEST 2,53178 FRAME STRUCTURE RoR TURBNEv-GENRRATOR PRIME MovRRs Filed Sept. 8, 1949 Ihvhtor: Frm/'atrs H. Van Nest,

A* storm ey.

Patented Nov. 21, i950 STRUCTURE FOR) TURBI'NE- GENERATR PRIIWE MOVERS Francis Ervan Nest, Marblehead, Massa assignor to Generali Electric Company, a corporationY of- New. York Application September 8, 1949; SerialNo. 114,482'

(C1. Bil-95:)

5 claims;

AThis.A invention relates. to. supporting frame structureW for a prime mover:v such; as a steam turbineA generator', particularly" to; a'. frame struc'- tuiie ior.' such a prime mover as used'. in. marine.

vessels: for' auxiliary shipboard power where the ships structure is subj ecttosubstantial.deformations' in operation and the #rame structure of the" primer mover is? relied upon to'v maintain accurately the required alignment of the bearings. A sf'willi'be appreciated by those skilled in the art,l the comparatively small turbine-generator' units usedtor auxiliary'power' on marine vessels ordinarily comprise an' electricv generator, with its exciter, andi a steam turbine' arranged in substantially coaxial relation: on a common supporting'! base' orfranie structure', o'r fastened. to a. .portionl of the ships' framework which is made suiciently ri'gi'cl as to maintain the required accurate alignment of the shafts of there'spe'ctive components.

but d-rives'throu'gh a. suitable" speed! reducing gear.. For"instance,V the turbine speed' may4 be' onV the order of. from 10,009 to' 25,000'R; Pililfwhile the' generator runs: at from 906 to 3650 Roll?. and" a single reduction gear', ordinarily off thehelical type; isf' provided between turbine and generator.. Because of the severe' operating conditions under which' such: powerplants operate, maintaining proper alignment or the tnrbinerr generator; andl necessary rigidity. This practice has had certain undesirable consequences. The site and weight oi the" framework required have Abeen a disadvantage' since every' pound added or cubic foot occupied reduces the payload the shfp may carry. Furthermore, ii the' prime mover frame or bed is connected at four or' more points tothe ships structure', then any distortions in the ships framework eausedtby' severe stresses encountered' in heavy seas is likely to' be transmitted to the powerpant, the resulting possibility that distortion of the frame and disalign'ment oi'. the bearings will occur.`

A further.V source` of distortion of the prime mover' frame has resulted from the increasing practice of." supporting' the steam' tuebines conte In' many such` powerpl'ants. the: turbine'is vnot directly connected to' the'ge'nerator- 2' denser directlyfromthe'prime mover frame. The most usual practice has been to` suspend ther condenser' below the' frame. It is', of course', wellknownrthatt a steamicondenserchangesfitsdimeirsionsv quite appreciably as the operating.' temperatureY changes.` The most obvious and substantial chanig'e is that: an elongated condenser will` change in. length'. Howevenit has also been discovered that along condenser will experience' what is' referred to hereinafter' as humping distortion,` resulting from the fact that there' may be a. veryl substantial temperature difference between. the top and bottom` of'. the condenser.:` Since' the hotter liuidl in the condenser is at` the top While the coolerv fluids. sink: tothef bottom, the upper half' of thev condenser shell; willi tend* to' be ata substantiallyhgher'temperature than tlrieulower` half. The result. is that thefwholef con denser'she'll tends 13o-bulge or hump upwardly i in' the middle: Considerable diiiiculty has been;

experienced ini providing suitable means for supporting the condenser from the prime mover fra-me' in such` a manner` that rthese thermal` dis-` tortions experienced by the condenser willA not. result in additional distorting forces beingapplied: tothe primemoverrframe';

It is also'to` be noted: that. ther steamr turbine, itself? will. cha-nge its,y length substantially so that. special. provision must be made in*` order that thermalchangesinthedimensions of theturbine casingi will; not imposeA distorting forces on the framework.

Accordinglyr the object of this invention is to provide a' supporting: frame-.for a powerplantI of the'ltype'y described so designedY tha-tit may be of Y neatli the turbine-generator,thefarrangement bem ing. such that not only does the condenser not transmit any distorting forces, to the frame but; on the contrary it enters into structural cooperation with the frame to-greatly increase the rigidity thereof;

Other obj ectsY and advantages willbe apparent from' the following descriptiontaken incormection with the accompanying drawing., in which Fig. 1 is a side view in. elevation of' a steam turbine-generatorprme moverihavinglabaseand condenser arrangement arranged in accordance with the invention; Fig. 2 is a plan view of the base and condenser combination with the other powerplant components removed; Fig. 3 is an end view of the complete prime mover and frame structure, partly in section; and Fig. 4 is a sectional view on, line 4 4' of Fig, 3 illustrating the special mounting trunnions for connecting the prime mover base to the ships frame.

Turbine-generator frames of the type described ordinarily comprise a pair of transversely spaced longitudinal beamfmembers parallel to the axis of the turbine-generator. Such beams are comparatively easy to fabricate by welding plate and structural steel shapes to provide the requisite stiffness with respect to bending deformations. These longitudinal beam members are connected by a plurality of transverse beams and stiffener members, with suitable mounting plates secured to the top of the frame for supporting the exciter, generator` turbine, reduction gear, etc. While such a frame can be readily designed to provide good stiffness against bending deections, it has been found extremely difficult to provide the necessary resistance to torsional deformation of the frame about a longitudinal axis parallel to the turbine-generator axis. Unfortunately, this particular type of deformation has'a most serious elfect on the alignment of the powerplant bearings, especially with respect to misalignment of the teeth in the reduction gear. The present. invention is specificallyV intended to provide the necessary rigidity against such torsional deformations; and to this end the condenser mounted below the prime mover base structure is employed as a stressed member Which enters into cooperativestructural relation with the base, While at the same timeY the relation between condenser and base is such that the peculiar thermal l,distortions of the condenser do not impose any additional distorting forces on the base.

Referring now more particularly to Fig. 1, the turbine-generator comprises, from left to' right, an exciter indicated generally at I, a generator shown at 2, a reduction gear at 3, and a suitable Steam turbine 4. The internal mechanical details of these components are not material to an understanding of the present invention and are therefore not disclosed more specifically. It may be noted, however, that high temperature steam is supplied to the turbine through a flanged inlet connection shown at 5 from which amanually operated shut-01T valve 6 admits motive fluid to the valve chest, where suitable governing mechavnism positions admission valves to control the operation of the turbine. Spent motive fluid passes from the exhaust casing 'I through a flanged outlet indicated at 8 to the condenser,

in a manner described more particularly hereinafter.

The base proper comprises the main longitudinal beam members 9, I0. 'I'hese have a plan shape as shown in Fig. 1 and a channel cross section as shown at 9 in Fig. 3, and are arranged in transversely spaced parallel relation as lshown in Fig. 2. At the left-hand end, these main side beams are connected by an end cross'beam II, which may also be of a channel shaped section as indicated bythe dotted lines in Fig. 1. A similar channel-shaped cross beam is provided at the right-hand end of the frame as shown at I2. Additional cross members for supporting the powerplant components and stiiening ,the base are provided in the form of an intermediate main Cross beam I3 shown in dotted lines in FgS- l and 2, also a plurality of cross-brace plates shown at I4, I5, I6. 'Ihe direct supporting members for the powerplant components are a plurality of base plates, as follows. The base plate I 'I is welded to the side beams 9, I0, the end beam I l, and the cross-plate I4, and carries the generator pedestal 2a. and the' exciter pedestal Id. The base plate I8 supports the main generator casing and is welded to the main cross beam I3 and the side beams 9, I0. Plate I9 is welded'to the top edges of the cross-brace plates I5, I6 and A to the side beams. It carries the reduction gear housing 3 from which the inlet end 20 of the turbine is supported. The exhaust end of the turbine casing is supported from the end crossbeam I2 by one or more vertical transversely arranged support plates 2|. In the present instance, there are two of these plates as may be seen in Fig. 3. It is to be noted that 'these support plates 2I are sufficiently thin in cross section as to have appreciable exibility in the longitudinal direction relative to the turbine axis. With this arrangement, the turbine casing portion 20 is fixed at the gear casing so that any change in length of the turbine easing due tov changes in operating temperature results in iiex-v ing of the support plates 2I. Thus the turbine casing is free to expand and contract without imposing bending stresses on the base structure. At the same time, the inlet end of the turbine is fixed in space relative to the base so that the problem of coupling the turbine shaft to the reduction gear is simplified.

It will be understood that the main side beams 9, IU and the various transverse members are all suitablywelded together so that the base proper forms a quite rigid integral structure. This integral base is supported from the ships structure by a special three-point'trunnion arrangement as follows. The location `of these trunnion supports is best seen in the plan view of Fig. 2. A pair of transversely spaced trunnions are indicated at 22, 23. The third point of support is provided by a trunnion 24 associated with the end cross beam I2. The details of these supporting' trunnions may be best seen by refer-y ence to Figs. 1, 3, and 4. In Fig. 3 it will be` seen that the trunnion assembly consists of a heavy lug member 23a welded to the outer surface of the main side beam 9, and having an end portion 23h which is square in section as may be seen in Figs. 1, 4. Aswill be seen more clearly in Fig. 4, the lug end portion 23b is received in the central opening of a hollow rectangular mounting support 23e, which is carried on the shipfs frame structure by any suitable means (not shown). Lug 23h is pivotally carried in the mounting support 23e by means of a specially shaped pintle 23d. This includes end portions tting a transverse bore 23e as will be apparent from Fig. 4. 'I'he intermediate pintle portion 23j has a spherical curvature, the maximum diameter portion of which fits the transverse bore 23g in member 2312. It Will also be apparent that the spherical intermediate portion 23j is connected by reduced diameter portions 23h, .to the pintle end portions 237'. With this pintle coniiguration, it will be apparent that the lug end portion 23h is free to move pivotally to a limited extent, either about the axis of the pintle 23d,

or to tilt aboutan axis normal to the-plane' of Fig. 4, as permitted by the spherical intermediate portion 23f. With this arrangement, it Ywill be obvious that any distortion of the mounting support 23C, due to Weaving of the ships frame,

asegure adiustment of. theisupporting lugsI 23a,y relative tof the: pintl'es, without: any stresses: being: trans-A mitted from the shipsstructure to the prime mover; baser structure.

The mounting trunniens` 22, 2,4 are, of course.. similar: in structaue toI the-trunnion 231 It will be apparent from the above that" the; side: support trunnions 22, 23 ,may be displaced vertically, in opposite.- directions, without pro ducting any torsional' stresses: on` the base member, the only resultlbeing a. slight rotational shifting; of the end, trunnion lug 24a.

The manner in which the condenser is incorporated into the primemover frame structure is. as follows. The condenser'fis shown` generally atl 25'.. In'. practicing the invention, the condenser used` is of a. type: which: is circular in cross section; as seen in Fig.. 3 withr ani integral cylindrieat outer shell. of a thickness adequate: tor en abler the.. z-:ondenserV toY perform the: structural functions described hereinafter. It will. also` be observed the condenserislof substantial axial; length',` roughly equal to the longitudinal distance between. the sidesupporting trunnions.` 22?, 23.v and'. the: end! trunnion 24. While. in` actualv installation, this' condenser.'l would. be' provided with; various auxiliary devices, such as an ejectcu: or

equivalent pump forremoving'air from the: con

denser, cooling water circulating. pumps, and a hot-well or" condensate pump.. etc., these auxdevices have been omitted from the drawing since they arenot material` to an;` understanding' of. the present invention..

The condenser` is.' suspended from, the base proper in; the.` following manner; At the respec' tive endsv of the,l condenser shell there are' firmly secured transverse vertically extending supportplates, each weldedV to the` upper half; of the cir-- cunerence oi the condenser shell, as may be seem in Fig.. 3'. The` left-hand condens'ei-r support plate- 26" extends upwardly as indicated by thed'ottedf. lines in Fig; 3 and is secured atj its top. edgeA only' to thev base, as by welding: to the main intermediate cross beams i321. Whilev this support' plate: 26 isl comparativelyy thin' so ass to. be flexible!- in an axial. direction,` its, plan View, as shown; in Fig. .3, is' suchv that it i's extremely rigid withrespect: to resistance.v to forces constitutinga couplel in the.` plane of the plate; y

The-other condenserI end support plate 2T may be of' thicker, stiffer cross. section and is. weld'efdi rigidly tothe outer-end' surface: of the mainl cross: beaml 2f, with ther result that the. rightehand end; ofthe condenser is supported iny fixedj relation'y relativeto the base. The plan shape. of the' sup portv plate 2 is likewise such that ity furnishes very considerable resistance to any couple tend-- ing to` rotate the end cross beam l'2l relative' to the condenser about a longitudinal axis. Withl thisA supportingv arrangement, the condenser is xed at the right-hand end but is free to expand to the left as its operating temperature changes, which expansion is'accompani'ed by lateral flexing of the other end support` plate 2E. Thus changes in theover-all length of the condenser' have no tendency to impose deforming forceson the' base structure.

It will* be apparent that, alternatively, the plate 26 might be rigidly fixed to the base, with the endl plate 2Tl'eft1free toex with changes in the Iengthf of the condenser; They criterion is of course, that't'he condenser must be rigidly secured' to'l'theba-'se at one point in' order to withstandv shock loads in the vfore and aft and sidewaysdiz:

rections,l the support for: the otherl end: being; free to flex in. a longitudinal; direction,V

It is important.- to note',- that the cross-brace plates i5., t6 are not secured to: butform: aspir-v stantia-l clearance: space, shown at l5'a.'` in Fig. 3., with the top of the condenser shell..v When the condenser is'. subject` to the humping type: of: distortion, the clearance space lia. prevent any distortingv eect onthebase structure. Thus itl will be seen. that, by iixing' the condenser at one end tothe base, flexibly supporting it at the:- other end from the basegand" havingY no intermediateY points of' contact: between condenser and base,V there is; no; tendency for deformations of' the condenser to impose, extraneous. stresses on' the. base..

It will, of. course. be' understood that the; tur-v bine. exhaust flange 8 i-s connected' tothe condenser inlet ange 25d by a nexible conduit; such: as; thebellows shown in dotted lines at. 28 inFig'.. l, or by any other equivalent suitable type of flexible. expansion joint. The exbility oiA this connection is, of coursalmportant to insmeathat: distortions of the condenser willimpose no de forming forces on; the. turbine.

It will be observed that the base plate i9, they cross-brace plates I5, I6, enclose a space: above the condenser which may be employed as the4 oil reservoir for the turbine, reduction gear, etc.,` simply by adding a flat horizontal plate.` shown in dotted lines at 29 in Fig. 1. Alternatively, a separately fabricated oil tank might'bel supportedv by suitable'means in. this. space. Thus the oilf reservoir is conveniently located relative to the?.v

i turbineV and gear, which are the components 1re--v quiring most lubrication.

The'V manner in which thev condenser enters intov structural cooperation. with. the'. base may now be= seen. As is well understood, a hollowI cylindrical shell is the geometrical shape-.Which has the max-l iinuin possibleresistance,` per unit weight of materiali employed, to torsional deformationV about the axis of the cylinder. As noted above, the: condenser is considerably elongated and extends substantially between the mounting` trunnions,

being; connected. to: the; base proper by the condenser support plates which are exceptionally rigidv against torsional' deformations. about anVv axis normal' to the plane of the: support plates.A Thus. it willbe apparent` that,.if the base shouldl beheld xed at the side supportV trunnions- 22, 23- and av twisting couple applied to the right-hand' end of the base, this couple will be transmitted; through the condenser support plates to the cylindrical condenser shellwhich will stronglyI tend to resistany such torsional deformation. Thus it'. is seen that the condenser shell cooperatesv as' a structural member with the base. toy preventtorsional deformation thereof.

fisV will' be apparent from the drawing, the cylindrical condenser shell has a diameter roughly equall to half the width of: the base. It would, of course, be feasible to use cylindrical members somewhat' smaller, ori much larger, i`ndiameter than that shown. The the diam--r eter'of the shell, the stiffer' it willl bein resisting torsional deformations. As a practical matter, in order to have a neat compact assembly, it is desirable that the diameter of' the shell should' not have a diameter greater than the width of the base. On the other hand, the diameter of the shell should not be less than about half the width 4of the base if the' requisitev stiffness against tor-- sional' deformation is. to. be obtained'. It will be obvious thatv in; some installations the deformng 7, forces may be sufficiently lowv that `a somewhat smaller shell would be adequate to prevent twisting of the'base. In general then, it may be said that for all practicable purposes the diameter of the cylindrical member should at least be on the order of half the width of the base, with the maximum practical Value about equal to the width-of the base.v

Likewise it willbe obvious that the depending transverse plate members must be spaced apart a sufficient 'distance longitudinally. Ordinarily, the three mounting trunnions will be located first, giving due consideration to the distribution-f the weight of the machine components on the base, the location ofl the center of gravityvof the whole assembly, and the effect of any gyroscopic loads on the mounting trunnions which may be encountered, etc. Having determined the location of the trunnions, the depending plate members are located in close proximity to the longitudinally spaced Vtrunnions so that any twisting couple transmitted to the base through the trunnions will be directly transferred' to the cylindrical shell.'

The invention provides a compact steam turbine prime mover frame in which an elongated steam condenser occupies a minimum amount of space beneath the base and is so connected thereto that the condenser serves as an important stressed component of the complete frame structure, providing exceptional rigidity against torsionaldeformation of the base. With the aid of the invention, an integral turbine-generator frame is provided of such rigidity that it may be conveniently supported by three mounting trunions from a ships framework as described above, the trunnion supports being specially arranged to prevent the transmission of any deforming forces from the ships structure to the prime mover. At the same time, the compact shape and minimum over-all dimensions of the turbinegenerator with its integral base and condenser structure make it exceptionally easy to handle in installing and removing it from its foundation in a marine vessel.

While the invention has been described as applied to steam turbine-generator units for marine vessels, it is obviously adapted to other uses, for instance gas turbine powerplants supported from framework subject to distortions, such as the chassis of a locomotive or frame of an aircraft, in which cases the condenser might be replaced by a cylindrical fuel tank. It may also be used'on land-based powerplants to simplify installation and to overcome difficulties which sometimes are caused by foundations settling.

While only one embodiment of the invention hasvbeen described in detail, it will be apparent to those skilled in the art that many changes may be made in the specific arrangement of the prime mover components on the base, and in the mechanical details of the base structure; and it is desired to cover by the appended claims all transversely spaced longitudinal side beams eX- YVtending substantially the length Vof the machine,

atleast two longitudinallyspaced cross members connecting the side beams; two parallel transverse plate members depending from the cross members, at least one of the plate members being adapted to flex in a longitudinal direction so the distance between the depending end portions of the plates may change without imposing excessive stresses on the base, a hollow elongated substantially cylindrical shell disposed longitua dinally beneath the base, and means securely fastening said depending plate end portions to axially spacedportions of said shell whereby forces tending to torsionally deform the base about a longitudinal' axis are resisted by the shell while the shell is free to expand and contract longitudinally, there being no points of rigidly fixed connection between the shell and base intermediate said plates, '2.' In a frame for a machine of substantial length having longitudinally spaced bearings the alignment of which depends on the rigidity of the frame, the combination of a base comprising a pair of transversely spaced longitudinal side beams extending substantially the length of the machine, a plurality of longitudinally spaced cross members connecting the side beams, two' parallel transverse plate members depending from' two of said cross members and spaced longitudinally a substantial distance apart, at least one of said plate members being adapted to flex in a longitudinal direction so that the distance between the depending end portions of the yplates may change without imposing excessive stresses on the longitudinal beams or cross members, said depending plate end portions being securely fastened to axially spaced portions of a longitudinally extending cylindrical member whereby forces tending to torsionally deform said-base about a longitudinal axis are resisted 'by the cylindrical member while the latter is free to expandy and contract longitudinally.

' 3. In a frame for a machine of substantial axialY length having longitudinally spaced bearings the alignment of which depends on the rigidity of the frame, the combination of a base comprising a pair of transversely spaced longitudinal side beams extending substantially the length of the machine and adapted to withstand bending stresses without substantial deformation, at least two longitudinally spaced cross members connecting the side beams, an elongated cylindrical shell disposed below and with its axis parallel to the length'of the base, the diameter of -said shell being at least on the order of half the width of' the base, two transverse plate members, one se'- cured to each of said cross members, said plates having depending end portions firmly secured to axially spaced portions of said shell around substantially half the circumference thereof, at least one of said plate members being adapted to flex in a longitudinal direction in order that the shell canvchange length without imposing substantial bending stresses on the base, whereby any forces imposing a couple on the base tending to deform it ltorsionally about a longitudinal axis are resisted by the cylindrical shell. Y

4. In a frame for a prime mover of substantial axialvlength having longitudinally spaced bearings the alignment of which depends on the rigidity of the frame and adapted to be supported from other frame structure subject to substantial deformation in service,v the combination of a base comprising a pair of transversely spaced longitudinal beams extending substantially the length of the machine, at least two longitudinally spaced cross members connecting the beams, two parallel transverse plate members depending from said respective cross members, at least one of the plate members being adapted to flex so the distance between the depending end portions of the plates may change without imposing excessive deforming stresses on the base, said depending plate end portions being securely fastened to axially spaced portions of a hollow cylindrical shell around substantially half the circumference thereof whereby forces tending to torsionally deform the base about a longitudinal axis are resisted by the shell while the latter is free to expand and contract longitudinally, and means for supporting the base at three points including a pair of transversely spaced trunnions adjacent one of said plates and a third trunnion adjacent the other plate, each of said trunnions being adapted to eiect a limited degree of free movement between the base and the supporting frame both about an axis which is parallel to the plane of the base and also parallel to the longitudinal axis of the prime mover and also about an axis normal to said rst axis and parallel to the plane of the base, whereby deformations of the supporting frame structure during operation result only in limited relative movement in said trunnions without transmitting deforming forces from the supporting framework to the base.

5. In a frame for an elastic fluid turbinegenerator of substantial axial length having longitudinally spaced bearings the alignment of which depends on the rigidity of the frame, the combination of a base comprising a pair of transversely spaced longitudinal beams extending substantially the length of the machine, at least two longitudinally spaced cross members` connecting 10 of the plate members being located adjacent the exhaust casing of the turbine. and one of the plates being adapted to llex transversely so the distance between the depending end portions of the plates may change without imposing excessive deforming stresses on the base, a motive fluid condenser disposed below the base and having an elongated cylindrical shell with end portions adjacent said plate members, and means securing the end portions of the condenser shell to said depending plate end portions whereby forces tending to torsionally deform the base about a longitudinal axis are resisted by the condenser shell, the flexibility of said plate member permitting the condenser to expand and contract longitudinally without imposing deforming forces on the base, flexible conduit means connecting the exhaust casing of the turbine with the condenser, said exible conduit constituting the only point of contact between said shell and base intermediate the supporting plate members whereby humping deformation of the condenser imposes no deforming stresses on the base.

FRANCIS H. VAN NEST.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,491,423 Rice Apr. 22, 1924 1,760,545 Doran May 27, 1930 2,264,830 Dickinson Dec. 2, 1941 2,394,685 Hall Feb. 12, 1946 2,464,357 Stearns nat- Mar, 15, 1949

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