US1897172A - Vane rim for turbines - Google Patents

Description

Feb. 14, 1933. F. LJUNGSTROM VANE RIM FOR TURBINES Filed Aug. 16, 1929 2 Sheets-Shet 1 Feb. v14, 1933.

F. LJUNGSTROM VAN}; RIM FOR TURBINES Filed Au /1s, 1929 2 Sheets-Sheet 2 Patented Feb. 14, 1933 FFIUE FREDRIK LJUNGSTRile'I, 0F BREVIK, SXVEDEN, ASSIGNOR TO AK'lIEBOL-AGET SPONTAN, OF STOCKHOLM, SWEDEN, A CORPORATION OF SWEDEN VANE RIM FOR TURBINES Application filed August 16, 1929, Serial No. 386.241, and in Sweden In turbines, especially steam turbines of the kind in which the driving medium passes through the turbine in radial direction, which type of turbine is generally known under the denomination Ljungstrom turbines, the maximum output of the turbine is limited by the cross-sectional area of the steam passage between the blades of the outermost rotor of the turbine. The magnitude of said area depends on how long the blades can be made, the length, in turn, being d termined by the capacity of the blades to take up stresses due to the centrifugal force to which they are subjected during rotation. The blades are subjected to bending stresses due to the centrifugal force and, as their section approximately determined by the conditions of flow of the driving medium, i. e. the steam, the length must be limited so that the stresses arising in the outer portions of the blades due to the bending stresses lie within permitted limits. It is evident, however, that, under such conditions, the strength of the material of the blade lying radially in ward with respect to said portions, as in the central part of the blade, will not be fully utilized, as the stresses created in the central part on account of the centrifugal force (and arising from bending stresses) are consider a ly smaller than the stresses in the outer portions.

The present invention has for its object to render it possible to more rationally utilize the whole cross-section of a blade of the type above referred to for taking up stresses aris ing from the centrifugal force, and to this end I provide radial flow blades so constructed and arranged that only tension stresses or only compression stresses arise in the same, which stresses are uniformly or practically uniformly distributed over a cross-section of the blade taken anywhere along the length of the blade.

The invention will be more fully described with reference to the embodiments thereof August 18, 1928.

illustrated on the accompanying drawings, in connection with which further features characterizing the invention will be set forth.

In the drawings, Fig. 1 is an axial sectional view of part of a rotor constructed ac- 5o cording to the invention; Fig. 2 an elevation of the same seen from below in Fig. 1; Fig. 3 is a cross section of part of a rotor illustrating the manner of securing blades and stays, respectively, to supporting annular members; Fig. 8a is a cross-sectional View taken on the line 3a-3a of Fig. 3; Fig. 3b is a cross-sectional view taken on the line 3b8?) of Fig. 3; Fig. 4 is a cross section of the blades and the stays taken on the line 4-4 in Fig. 3; Fig. 5 is a section taken on the line 55 in Fig. 3 illustrating thickening of the blades and the stays, respectively, at their fastening places; Fig. 6 is a cross-sectional View t lien on the line 6-6 in Fig. 1; and

Figs. 7 and 8 illustrate an embodiment of the invention including straight stays.

Referringmore particularly to Figs. 1 tirough 6, reference character a designates turbine blades which may be secured in known manner to rotatable auxiliary spaced annular supporting or retaining members or rings 6, for instance, by welding or rolling. Two annular members I) and the blades connected thereto constitute a rotor. The steam fio is in generally radial direction through the rotor. As is well known, a radial flow turbine includes a number of such rotors which are alternately connected to aligned shafts which rotate in opposite directions. According to the invention, said blades have such a shape (in the present case a shape bent outwards in relation to the center of rotation of the rotor) and are so supported that stresses in the same due to the centrifugal force are substantially taken up by tension stresses only, which are distributed evenly or approximately evenly over the cross-section of the blade. On account of I to preferably increase towards the endportions,

the stresses increasing at the'end portions of the blades, the cross sectionsofsaid blades for the blades may be reinforced at their end lar to' the aforesaid" edges,

annular .ineinbers b, as shown at 2'in Fig. 5,

H IAs clearly shown in the blades preferably have parallel outwardly curved inlet and outlet edges and theorosspoints, i. e. at theirplaces of fastening in'the drawings, the

seotionstaken normal (that is, perpendicuare of equalsarjea.

2 for all or "a greater portion'of the length of the'gblade;Referring to the cross-section H .Ljungstrom radial known construction,

line crossing the line of zero stress ;7 Whereas would give'a foroe hmtre s a r It is oobe obseryedr that, Kin blades fcon- "lar meinber s' Z) toward. each -are so formed that,onfaccount ofthe een-l trlfugal force, compression stresses willwith blades in ac cordance with the present invention; Corresponding stress x diagram;

line parallel to the l ne structed in the manner aboye'setforth; the tension stresses 'createdby the" centrifugal; force will have a tendency to draw the annuother-.7; In order;

I provide stays 1 to counteract this; tendency,

0 so formed as to maintain themutual PCS]:

tion of the annular members ;"that is, to maintain the annular members. -ai-fiXeddi's -l tanoe apart, In the present case the stays arise in the same haying tendency to move 'tation, are bent or rotation outwar blades as, aboyefdescribed, whichfstresses' t wouldbe obtained, if the blades, instead of being bent outwardly from the centerofi ro- 1 inwardly. In this case coinpression stresses 'only would arise in; the v bladesl'instead' of tension stresses," and, asa 'fconsequenoe of this, i

the stays in this case should be bent outwardly-so that correspond;

ingltension stresses arise in the stays In Figs;

Tand 8 another'einbodimentof the inventionis shown] Fig. 7 shows aeross section through aflnumber of rotors vof aturf binebf these-called louble rotating type clesigned for a high number of revolutions and for a highrcapacity and Fig. "8;;shows a pro-2 j ection of onerotor, carried out'in'accordance and seen froin'the center with the invention ell y, with the blades omit-- ted.* Thisrotor comprises anuniber of out-5' wardly'bent'blades d whiohattheirends are attaohedgto elements be iUponl -rotation ot the turbine,"the'centrifugal forces cause annular blade; retaining members of stresses in'these' to clraw the' ring element's}' toward other '1 order tocounte balance thisustays which stays;

the plane of rotation ofi 'an stays their carrying rings 0 as illustrated in 8,;

ed betureenfsaidring' elements v njthis' ernbodiment are straight or substantially straight but,- as above ole a-ife a'rranged with a n obliqueangle with respect p nular 'inember of the .rotor. Forthep'ur-i poselof' taking up the i V I stresses originating- V fironij th centrifugal forces on these 'and,; .for, the purpose "of increasing the annular' members I; away iroineach -\E he bl ades a "intheouterrnost rotorsare; "other, thus counteracting the act on on said. as w ll appear rom Fig. 7; b'ent outwardly'to j V may: be so-gdimensioned' or ti'vely,

" to-the plane ofrotation of the annular menu bers balanceeaoh j result upon said annular members -speeclsof I haveaso callecl'drop or streainlinecrosssection as shown in Y In rotors jhaying long blade r respectively f reinforcing provided, for instance '1 I members of stresses -:in the blades. 0;. i The dos and the stays, arranged, respectthat, as shown, in- Big; 3, the eom B l r-1Q d rect d a rig t wa different parts, is the bl ponents other so that said stresses 3 wi s i dial yi ect r les.

Preferably the stays are arran ged, between the;annularimembers as; seen in radial direct1on,1 a n oblique angle f fastening to the fplane ofrotation may without. dii fioulty be usedalso at considerably hlgh revolution. Preferably the stays t r' bands j inayj bethe mannershown t fin Figs, 1 2; 6, in order to counteractayi;

tion l, 675 bra v of th'eyanes' or thestays', respectively,

Anefi'eot-siinilar to that above'describedf 1 a large outlet? ininute I and with outlet of to 4 m ancl nore; allowing "afpower output';'of.inore}than EZOQOO.kwi v f It isto be'obseryedthat thei'nyention-is a high degree for the purpose of obtaining for. the driving inedi-uin, am in 'a'steam turbine; 1 i I ,J TlllS lieatvye outward bending does'fhon ever, {not require a y particular "attachment i e. forthe st of the blades to; theriiig el mental); but-this 'attaqhmentjmayb effeete'd ininanner-known in; ofi'the metastases be areas in the last rotor teammate to thi embodiment of the same desoribeclaboye' but includes also other 'con- 7 structions falling vyitliiilv the invention J l off-blades secured itoiand extending between oonstruotechwhiehif eiiahle are: building-of; double rotating turbines Wltllladlfil ojrf'nearly r adial steam flow for-3000 revolutions per 1115 Having thus described my inventi ni h t l claimisi; 7-7 a L a turb ineya rotor eo nprising axially spaeedfsupfporti'ng ineinb'ers and a plurality said members said jblades -having axially ouryed inlet and outlet edges, tlie conforma 1 tion of u said blades being srichthat stress therein due to centrifugal force, on rotation of the blades, is substantially uniformly distributed over and at right angles to any cross-section of minimum area.

2. In a turbine, a rotor comprising axially spaced supporting members and a plurality of blades secured to and extending between said members, said blades having parallel and axially curved inlet and outlet edges, the conformation of said blades being such that tensional stress substantially uniformly distributed over the entire cross-sectional area of any cross-section perpendicular to said edges is imposed thereon by centrifugal force due to rotation of the blades.

8. In a turbine, a rotor comprising axially spaced supporting members and a plurality of blades of substantially uniform width at cross sections normal to an axially extending edge thereof, said blades being secured to said members and disposed therebetween, the central portions of said blades being at a different radial distance from the axis of rotation than the ends of the blades and means providing a radial flow of fluid to said blades.

In a turbine, a rotor comprising spaced supporting members and a plurality of blades of substantially uniform width at cros sections normal to an axially extending edge thereof, sa d. blades being secured to said members and disposed therebetween, the end portions of the blades being radially nears the axis of rotation than the inter mediate portions, and means providing rasaid blades.

dial flow of fluid to 5. In a turbine, a rotor comprising spaced supporting members and a plurality of lades of substantially uniform, width at ss sections normal to an axially extend- .,...id bla des being secured to said members and disposed therebetween at an angle to a plane normal to the axis of rotation of the turbine, said vanes being curved racially outwardly intermediate the ends 6. In a turbine, a rotor comprising axially s, aced supporting; members and a plurality blades secured to and extending between said members and having their end portions oblique to a plane normal to the axis of roation of the turbine, said blades transmit to said members, due to centrifugal i'orce. forces haying axial components, and a plurality of stays between said members for counteracting axial components of said forces.

7. In a turbine, a rotor comprising axially spaced supporting members, a plurality of blades and a plurality of stays, said blades and said being secured to said members and disposed therebetween and having ieir end portions oblique to a plane normal the axis of rotation of the turbine, the blades being bent radially in one direction intermediate their ends and the stays being the bent radially in the opposite direction intermediate their ends.

8. In a turbine, a rotor comprising axially spaced supporting members, a plurality of blades and a plurality of stays, said blaces and said stays being secured to said members and disposed therebetween and having their end portions oblique to a plane normal to the axis of rotation of the turbine, the blades being bent radially out "'ardly intermediate their ends, and the stays being bent radially inwardly intermediate their ends.

9. In a turbine, a rotor comprising axially spaced supporting members, a plurality of blades having curved edges and a plurality of stays secured at their ends to saidmembers, said blades and said stays having their respective ends disposed equidistant from the axis of rotation of the turbine and arranged so that the axial components of forces exerted on said members by the blades due to rotation of the blades are balanced by substantially equal and opposite axial force components exerted on said members due to rotation of the stays.

10. In a turbine, a rotor comprising axially spaced supporting members, a plurality of blades secured at their ends to said members and disposed therebetween and having their end portions at an angle to the axis of rota tion, and a plurality of oblique stays secured at their ends to said members and disposed therebetween.

I 11. In a turbine, a rotor comprising axially spaced supporting members, a plurality of blades secured at their ends to said members and disposed therebetween and having their end portions at anangle to the axis of rotation, said blades being bent radially outwardly intermediate their ends, and a plurality of stays secured at their ends to said members, said stays being equi-distant radially from the axis of rotation throughout their length.

12. In a turbine, a rotor comprising a pair of axially spaced supporting members, a plurality of blades secured at their ends to said members and disposedtherebetween and having their end portions oblique to a plane normal to the axis of rotation, said blades being bent so that centrifugal force acting thereon due to rotation produces tension in said blades, and a plurality of stays secured at their ends to said members and disposed therebetween and having their end portions at an angle to a plane normal to the axis of rotation, said stays being bent so that centrifugal force acting thereon due to rotation produces compression in said stays.

13. In a turbine, a rotor comprising axially spaced supporting members and a plurality of blades secured at their ends to said members, said blades each having curved inlet and outlet edges in an axial directionand said blades f being thicker} {peripherally at their ends than at their centralportions;

14;. In a turbine, arotorcomprisingaxially spaced -supporting members; a plurality of elements including blades and stays secured at their'ends to said'members; said'blades each having curved inletandoutletedges in an I fly spaced supportingme'mbers, a plurality of L blades and a plurality axial direction and vibration preventing means c1rcu1nferent1allyassociated with some of said elements intermediate their ends.

15. In a turbine, a rotor comprising axial v of; stays secured at their ends to said Inembergsaid blades I each? 7 xha'vii'igf curved inlet and outlet edges; and 'mea'ns circumferentially I V engagingsaid stays aintermediatetlielrends; e

' 21 A, turbine comprising rotatable blade retaining: niembe'rsy means to axially space said retaining members,and'blades'extendmg between and having their ends secured to sald retainingfmembers; said blades havingfl inlet edgesfandout'let edges, said inlet and outlet edgesbeing said retaining members, and saidEb-lades being ends than intermediate the'endsL 7' signature. I 7

-e EQRI J NGS RoM;

' 16.-'In a turbine, a rotorcomprisingaxially pluralityoutlet edges being both curved to form arcs between said retaining members, a 'l f n eans 1 for? axially "extending between and having secured,.tojfsaidfretainiug members, said 7 blades haying inlet edges and outlet edges, w and fsaidinletand goiitlet" ed'ges 'being'both retaining members,

spaced supporting members, a plurality of blades and aplurality o'fistaysjsecured at their endsxto said mefnbers,

meansii to axially space said-retaining members,'bladesextendingihe 1 tween and"having their ends ise'cured to said and'said "inlet and edges and outlet ed esreta1ningnemhers,- and inean's proyi'dinga radial flow: of fluid to'js'aid blade.

- 18.7 A "turbine saicl blaid'es haying 1111a pris iig rotata e blade 1 spacing said retaining meinbersQandflolades I their? {ends Jcurvedto formarcsfhetwyeenfsaidretaining I lneinbeis said 151 A l retaining-me and means i ne' rj ia v w oiifluidto 23% i b ades;

retaining memb .7 fly area normal to said edges,

fand saidfstaymea nsbeing:under compression". stre'sst kw V adcs'loeingisoforrned as'to I 1 5 be subject substantially only'to tensionjstress;

: f19.--' A areas eenipfi iingfrotatable blade said'ireta'ining;members, bladesIextendingbe-T tween and havlng thelrends secured; to said a retaining members; each of.said bladesliaw V 1 I inglengthwise'curyedinlet and outlet edges,

.20. 9A neaapa agmama tha spacing; said retaining outlet edgesy andfcross e y hers, mean'sm axially space ers, aiwelbfstructure for; axial a 1 a a i f fie d.5

formed th'atfstrestherein'due tocentrifugal forcei' issubstantiallyuniformly distrihuted ave nyorsa1aarqss aaio s5 of greater cross-sectional area adjacent the ,In' testimony whereof I haveaflixedgrny both curved to form arcs between sip

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