US2382705A - Steam turbine - Google Patents

Description

ug. 14, 1945. E. GENTE 2,382,705

STEAM TURBINE l Filed Jan. 3, 194].A

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Patented Aug. 14, 1945 aasavosr' a v i -l STEAM TURBINE Ernst:(rente;` Berlin Siemenss'tadt; Germany; ves-technl the-A1ien PropertwGustotliana ApplicationJnuary 3, 1941, SerialrNoJ373Jl58`. t

InGermanyDecembenl; 1939 This' invention' relates-'tor the'ixingv of; blade rings for centrifugal'machines'with'gradial admis; sion of the working fluidparticularly for'steam turbines.

The two V main constructiona* parts "of a steam 1 turbine withm radialv admission off the working' medium,` i: ez; blade ringan'dfdiscrepresentbodies' having' different'masses land surf acesso that'these parts-when heated; cooledl or deformedby-exe Y ternal mechanical forces,- for' instance;l by the i0 centrifugal forcereactA in' a different manner.`v For instance, the ring withf-itssmall mass-and largeL surfacel when heated expands quicker I than the disc: Ifia rigid vconnectionvvouldl heusedbetween theL ringf and the' dis`lc,lsuchhigh stresses'v 15 would result `owing tothe diibrence inL expansion that'th'e vmaterial lcannotabsorb the #sainewithn out 'damagingdts'texture-, so tliata rigid conn'ection between the ring andi-'discl must beeavoided'i andfsuchf constructionsmustlfbeiusedas to permit' 20 a free and independent -expansimrof'fthe.ringanddisc. l

According to United;StatesBatentNo;1;000,097" this. connectionv is: obtained ibvainsertingbetween-i theblade yring and the-disc,v thinc-ival-l'edfcylinders` 25 the thickness of whichl is so' fchosen 'that;f onthef one han'dg'arltransfer offheat between th'ewbladef rings and'ithe disc is fpreventedltoiaaconsiderabie extent and that; on'; the: other1 handg. the :bladen ringwhen. being 'deformed'isi asf fan: as"` possible :so free to expand:^ However; .considerable berfdingff stresses occurx ini the'cylindere'shaped connectimgi`v piecewith; increasingaenlargement Ithatxthei 5mae.- terialzV cannot takeaupthe-rstresses: 'Ifoz,meet-.athisl requirement the cylindereshapeduringf*must' 'be 35 slotted, so thatv its cross-,section L isf.: weakenedi; whereby the tangential stressesk are, so to say;A splitlup.y Besides otherfd-rawbacksithe slotting of vtheI ring may-impair. the :steam-,tight iconditionv of the structure.

Theotherfpossibility of-providing; a joint beel tween the blade'ringanduthe-disc, asffreefas pos-. sible isthe kidney-shapedintermediate'ring em-y ployed in thedeviceof United States:Patent-No: 1,146,183 and Whiclrhas-'given satisfactory-me45 sults in a largefnumber of turbines.. 'Phisiintera` mediate ring is,` however; capableff of'beingximaproved, insofar asi it :,presupposesraf beady joints Such joints :not: only cause-astressingfof thezina:5

terial beyondits yieldcpointbut, alsof asidyfbring: 50'` about a non-circular cross-section of'fthevringf. In thiscase either the faults caused by the out of balance must be put up with or a rather comp1icated balancing method must be employed in order to ensure a smooth running of the tur-bine. 55

From the manufac-turingoandloperatingapnintiofv.V View, thejointfaccording t0 Unitedl-StatesvPatent No.k 1,000,09'1wou1d thereforelbex preferable;A a pro-.- vided@ thatit would loe-.possible to eliminatethef faults'finherentinthejoint Thefproblemsresultlingr-therefromare jsolved. aocordingtothepresent ,n invention.

If. theiconditions (presented, when iixing; the. bladeqring. according.A to lllniteel-` States Patent N o. 1,000,0971areenvestigatedKitt.will be Y found. that Y the moments whichoccunin the .connecting ring betweenthe blade ringanddiscas aresult ofthe enlargement-.of the blade ring, are very great) at thepoint Where ,the blade ring. is xedrb'ut. then,V decrease relatively rapidly, in the formof `a hyper- :bola The material is'therefore highly stressedA at the p oint Where the blade Aringvis .fixed'whereas the other partof the crossfsection is only sub`. ject'ed to relatively, small stresses.. Asr already mentioned above the high.stresses have been'.reduced'by slottingjtheiring; `The above-said draw-- backsmaybe removed Vaccordi'ngto theinvention by a .structure wherein' ,the entire "cross=section `is as fair as'possible uniformly'stressed If"'th'e-en tiretblade ringwereso"dimensioned astoltakepup the'maximumN stress,v without any shitting-,1the above-mentioned drawback would notfberemoved;

` sincethering would have vto be so amplydilnem stoned that-arigidconnection'witlfithe disc would' result which` would not' meet' the' desired require ments.v The y'resiliency' of-theringfwhich provides fr`v the free 'expansion withrespect toth'eLdisc must therefore be retainedi This may beiaccomplished `according to theinvention by-'th'e provision of" an intermediatey ring connecting the blade 'ring-f withlthe disc; thel cross'esection-f orl thickness vof 'which decreases towards the point" wheretlfelintermediate ring `is securedfto `th`e disc, the crosslsection beingfprefrably of f the--triangu-v lar' for-m. A's already'- mentfcm'edIabovetheI nrorrrentfcurve` is similarfto tlat'fof a'hyperb'olaz- Ac cordinglyrthe contour line-offthe crossesect'on is also fadaptedf' tol the Ymomentl curve:l It' i'sQtlien possible without slottingthe-intermediatering to absorbir all'stresses fwith'out overstressing the mal. terial 'andto utilize ati the :same :time the material offtlieintermediatefringiin:amost favorable man-- ner, sinoefitsentirecross-section: or a substantial portion thereof'sLA uniformly stressed? Ifthecasef offa revolving: disc-the centrifugal fo'ree=acti1"1gx thereon -h'as its poirr-t-'-offapplicationf in='the1center'-of'gravity of-"the'r blade ring.L The centrifugal force tends to shift outwardly the center of gravity of the blade ring cross-section, i. e., the intermediate ring integral with the blade additional weights to the blade ring or to the in termediate ring or to both, moments may be produced which more or less balance the moments resulting from the two centrifugal forces mentioned above. weights, the fact must be still considered that the shearing force produced by the enlargement of the intermediate ring produces a moment which opposes the enlargement. It may be necessary under certain conditions to consider this moment when determining the balance Weights.

As already mentioned above this form of the invention is based on the proposals to provide balance Weights or inertia masses which have been made for different purposes for example, in the U. S. Patent 1,906,697. When fixing the blades according to United States Patent No. 1,146,183 with .the aid of kidney-shaped intermediate rings as previously mentioned, the blade centrifuga-l force the point of application of which is in the center of gravity of the blade causes a twisting of the cross-section of the blade ring about its center of gravity, i. e., the blade with its sup-V port assumes then the form of an arc. To

straighten the cross-section of the blade ring it has been proposed in this patent to employ additional masses the centrifugal forces of which produce moments in the ring which balance the moments produced by the centrifugal forces of the blades and acting in 'the opposite direction. However, this refers as mentioned above only to such blades which are secured between two ring ygroups hingedly connected to the turbine discs, whereas the present invention is based on the fact that the blade ring ends in a thin tubular portion which is secured to the disc.

An embodiment of the invention is shown in the accompanying drawing in diagrammatic form in which Fig. l is a longitudinal vertical section through the blade ring, the intermediate ring and the disc, and Fig. 2 is a rtransverse vertical sec-'7,

tion on the line 2-2 of Fig. 1. The blades I of a st eam turbine with radial admission of the working uid are firmly held in position by the support or blade ring'2 which ends in an intermediate ring or tubular portion 3.' The latter is firmly secured .to the carrier member or disc 4 by means of a caulking joint 5 and is prevented from being displaced by a weld joint 6. The centrifugal force P1 is applied to the center of gravity of the support ring 2 and causes an enlargement of the ring 3. The rim force Pz produces by the blades acts in the same direction. As a result of the rigid connection between the support ring 2 and the tubular portion 3 thereof,

shearing forces P4 are produced in the latter which tend to oppose the centrifugal forces P1 and Pz. In View of the very high stresses to which the intermediate ring 3 is subjected the crosssection of the tubular por-tion thereof is not madev cylindrical as has hitherto been proposed but decreases as shown in the drawing from the blade ring 2 to the disc 4. In order to prevent the blades l from assuming an inclined position, balance weights are provided which produce the balance forces P3 and P5. In this case the force P3 balances the forces P1 and Pz, Whereas the force P5 balances the force P4. 'Ihe representation of the balance weights is purely diagrammatic. It is not necessary that two balance Weights be provided. The two weights may also be combined in a single mass. It is likewise not necessary to arrange the balance mass as shown in thedrawng.

When selecting these balance Y The above considerations on the revolving disc of a steam turbine with radial admission of the working fluid apply also to other centrifugal machines with radial admission of the working fluid in which similar conditions occur. The same considerations apply also to the stationary disc in which no stresses due to centrifugal forces but other stresses caused by the unilateral superatmospheric pressure may occur.

What is claimed is:

l. In a radial flow turbine, the combination of a radially extending rotor disc; a cylindrical blade ring; a plurality of turbine blades carried by said ring; and an elastic ring formed integral with said blade ring and secured to said disc, said elastic ring having a face tapered from the bla/de ring to the disc, on a curve corresponding to the curve of the moments set up in said elastic ring by the operation of the turbine. v

2. In a radial flow turbine, the combination rof a radially extending rotor disc; al plurality of turbine blades; and a tubular member axially extending from said disc, and comprising a cylindrical portion at its outer end, serving as a blade ring and upon which said blades are mounted, a reduced cylindrical portion at its 'inner end, received in and secured to said disk, and an elastic portion disposed between said cylindrical portions and having its outer end of the same thickness as `the outer end portion, and so .tapered to the reduced thickness of the inner end portion that its cross-sectional area on any radial plane is directly proportional to the stress exerted along said plane by the operation of the turbine.

3. In a radial flow turbine, the combination of a radially extending rotor disc; a cylindrical blade ring; a plurality of turbine blades carried by said ring; and an elastic ring secured to said disc, rigidly connected to said blade ring, and having a cross-sectional area in direct proportion to the shearing force produced inthe elastic ring, and the opposing centrifugal force applied to the blade ring and'blades, as a result of the operation of the turbine.

4. In a radial flow turbine, the combination of a radially extending rotor disc; a cylindrical blade ring; a plurality of turbine blades carried by said ring; an elastic ring secured to said disc and rigidly connected to said blade ring, the parts being so related that the centrifugal force, caused by the operation of the turbine, is applied t0 the blade ring and .the blades, and resulting shearing force is produced in the elastic ring; and two balancing masses located on said elastic ring adjacent said blade ring so as to counteract the eil'ects of centrifugal force on the blade ring and the blades and shearing force on the elastic ring respectively.

ERNST GENTE. l

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