US2295012A

US2295012A - Turbine blading

Info

Publication number: US2295012A
Application number: US382322A
Authority: US
Inventors: Harold W Semar
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1941-03-08
Filing date: 1941-03-08
Publication date: 1942-09-08
Anticipated expiration: 1959-09-08
Also published as: GB549100A

Description

Sept. 8, v W. SEMAR TURBINE BLADING Filed March 8, 1941 as ,o as 3 le wlNgssEs: A 9 .3| F-l 1 4. INVENTQR ,2z l H'nRoYn W. Samui.I 6. l I i Op, P9,

ATTORNEY la n .www| 4 Patented Sept. S, i942 narnia w.- semi, springfield,- ra,iass`ignqr to Westinghouse Electric & Company, East' Pittsburgh, Pa., a corporation of Pennsylvania Application Maren s, 194i; serial No, :'tfa-szz. j

The invention relates to turbine blading `o rabutment snrfaxcesz22n-lfoeengagement with the it has-foi:- itsobjectfthe provision of an improved innergoffthe so that, infoperatlon. as typeof bladefastening. hereinafter pointed but, forces appliedto each This and other objects are elfected by the infblade arevell'ectivelyresis'ted'by the cooperative ventionas .will be apparent from the following description, and claims taken in connection withv the4 intermediate and outer anges are provided actionftiffthe bearing surfaces 2l) anq 2&- Also',

the accompanying drawing forming a part of this with opposedbearing surfaces 23 and Z4; respeoflv i application, inv'which: tively, for eri'g.agcrrientv with the necks near the "Figsg 1 and 2 are diagrammatic views showing top of the grooves, these surfaces being effective C Ollvellifmal types of blade fastenings; and, 10 to hold the blades in position at lower speed.

Figs; 3, and 4 are detail`sefctional views showing Preferably, each groove Il isfradial and underthe improved type` ofA fastening. cut at one side and the outermost wall is relieved,

With' blade iastenings of the straddle-T type, at 26, to provide the inner and outer bearing sur- Whether the` `disc straddles the root, Fig. 1, or faces 22`4 and 24 and the inner-wall is shown as the rootstraddlesthe disc, Fig. 2, the centrifugal A15 being relieved, at 21 in-Fig. 3, to provide a bear- .I force is concentric with the neck sections Ses, ing surface 23 spaced from-the overhanging bear.

but is eccentric to'thesections T-'T. .A bending surface l5. Furthermore, the grooves are ing moment Y cf, f Y the walls of each groove with a. root is restricted XX Y V ,n A 20 to the opposed radial bearing surfaces 23 and 24 Y near the top of the groove and to the inclined where cf is the centrifugal force of the blade, surface t5 and the radial surfaces 22 near the would `be' exerted' on each section 'IJ-7T but forA bottom of the groove. the straddle connection at R, which exerts a In Fig. 4, showing a particular application of Vbending moment` LRXy; on Asection 'If-T: The 25- the invention,'the structure'is fundamentallyvtlie a part of the rotor, except that a bladeiisV atforce R, however, is statically indeterminate-desame as that already described, except that the pending upon the flexibility of thetension arm reliefo'l between the bearing surface 23 and the T T and the'initial clearance or press fit at R. inclined surface I5' is omitted, and caulking or and it cannot relieve the entire tension arm T-T wedges 3l are associated with the inner ends of of bending stresses. 3o the roots to bring about initial rm engagement With the improved root construction, statically of the inclined surfaces l5 and 20 with the inner indeterminate` -bending stresses in the tension end of the root abutting the surmembers-areavoided,-thenecessity for anacfaceA 22. d -curately-ttin'g`-straddl isileliminated, and` for In Figsaaand 4, the..centrifugal force iswcona given space, lower stresses on account of 'cen- 35'centric with-tension sections B-'B andY with the trifugal and steam forces are encountered. The tension sections A-A because of the equal, or

relieved at 28 and 29. Thus, the engagement of` improved fastening is particularly applicable to nearly equaLcentrifugal forces of the two rowsimpulse blades where there are two rows of blades of blades. The centrifugal force cfr is balanced on a disc or rotor, as shown in Figs. -3 and 4. bythe components .f1 and fr, which are statically The fastening resembles Fig2,'the Tineadzbeing aioidetermined Vby the simple'force triangle. 'The component frisdirectednormally with respect to tached to each-of the. tension arms T T. Y the overhanging inclined bearingsurface. 45 and Referring to Fig. 3, the blade disc or rotor'l the component 'f2 Vis directed normally with rehas a .pairyof grooves II defined by an intermediate ange'fl2 and outer anges i3. The' inv Y i5-'these components are `opnosedby thebearing surterme'diate flange I2is undercutat-eachsidm-as *facesl and 22, andastructure having such a indicated at 14, to provide overhanging .bearing disposition of'bearing smceswould be adequate surfaces l5` which are inclined outwardlyand fino.holdtherootanderesistlforces'applied to the towardrhe Vgutter anges I3. A Y ffloladeinoperationfhcwaever, tprefertohave-the The blades i6 havefroots l1 designed toit'the po-rotorlnangessexnufuuttmoly Yso -as roi-provide groovesgeach root having a fieckportion '18 Vand theopbosedheangsmaces'landli near the an inner portion `l9 enlarged at one'side.' The topsof assemble the blades enlarged portions have' surfaces 20 inclined conwith a-clearanceforlightpress fit. at 23 andl 2l, formably to the surfaces l5. to hold the blades in position at lowr speeds.

The oter flanges I3 are provided with bearing 55 From the foregoing, it will be apparent that,

spect toi the radial bearing surface 22. Thus,

v to the rotor, the necessity for accurate fits, such as heretofore required for the straddle connection, is avoided.

(3) For given limitations of space, the improved root construction provides for lower stresses in the fastening due to centrifugaland steam forces.

While the invention has been shown in two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of `various other changes and modifications without departing from the spirit thereof, and it is desiredl therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What is claimed is:

1. In a turbine, a rotor and a row of blades carried thereby, said rotor having first and second flanges defining a blade groove which is undercut at the second flange side to provide a bearing surface which overhangs the groove bottom and which is inclined outwardly and toward the first flange, said second flange being relatively thicker in an axial direction than the rst flange, each blade having a root provided with an inner enlarged portion and the enlarged portion having a surface inclined conformably to said inclined bearing surface for engagement with the latter, and said iirst flange having a bearing surface adjacent to the bottom of the groove for engagement with the root with the inclined surface of the enlargement engaging said inclined bearing surface.

2. In a turbine, a rotor and a row o f blades carried thereby, said rotor having first and second flanges defining a blade groove whichis undercut at the second-ange side to provide a bearing surface which overhangs the bottom of the groove and which is inclined outwardly and toward the rst ange, said second flange being relatively thicker in an axial direction than .the first flange, each blade havingv a root provided with an inner enlarged portion having a surface inclined conformably to said inclined bearing surface for engagement therewith, and said first and second fianges having opposed bearing surfaces adjacent tothe top of the groove for engagement with the root and said first flange having a. bearing surface adjacent to the bottom of the groove for engagement with the root with the inclined surface of the enlargement engaging said inclined bearing surface.

3. In a turbine, a rotor, and a pair of rows of blades carried thereby, said rotor having a pair of outer flanges and an intermediate flange defining a pair of blade grooves which are undercut at ther intermediate-flange sides to provide bearing surfaces which overhang the groove bottoms and which are inclined outwardly and toward the outer anges, the blades having roots provided with inner enlarged portions having surfaces which are inclined conformably to said inclined bearing surfaces for engagement therewith, and said outer flanges having bearing surfaces for engagement with the roots near to the groove bottoms with the inclined surfaces of the enlargements thereof engaging said inclined bearing surfaces.

4. In a turbine,` a rotor; a pair of rows of blades y carried thereby; said rotor having a pair of outer anges and an intermediate flangedefining a pair of blade grooves which are undercut at the intermediate-flange sides to provide bearing surfaces which overhang the groove bottoms and which are `inclined outwardly and toward the outer flanges, the blades having roots provided with inner enlarged portions having surfaces which are inclined conformably to said inclined bearing surfaces for engagement therewith, and said outer flanges having bearing surfaces for engagement with the roots adjacent to the bottoms of the grooves; and caulking cooperating with the inner ends of the roots for tightening the blades in the grooves with the inclined surfaces of the enlarged portions-.engaging the inclined overhanging surfaces of the intermediate flange and with surfaces opposite to theinclined surfaces and adjacent to the bottoms of the groovesfengaged by the outer fianges.

5. In a turbine, a rotor, and a pair of rows of blades carried thereby, said rotor having a pair of outer flanges and an intermediate flange defining a pair of blade grooves which are undercut at the intermediate-flange side to provide bearing surfaces which overhang the groove bottoms and which are inclined outwardly and toward the outer flanges, the blades having roots provided with inner enlarged portions having surfaces which are inclined conformably to t inclined bearing surfaces for engagement therewith, said outer flanges having bearing surfaces for engagement with the roots withthe inclined surfaces of the enlargements thereof engaging said inclined bearing surfaces, and said flanges having opposed bearing surfaces at the tops of the grooves for engagement with opposed sides of the roots.

6. In a turbine, a rotor; and a pair of rows of blades carried thereby; said rotor having a pair of outer flanges and an intermediate flange devment with the roots'near the bottoms ofthe grooves with the inclined surfaces of the enlargements thereof engaging said inclined bearing surfaces, and the intermediate and outer flanges having opposed bearing surfaces for engagement with opposite sides of the roots at the tops of the grooves; and caulking cooperating with the inner ends of the roots to obtain a tight fit of the roots with respect to the grooved overhanging inclined surfaces and the surfaces opposed thereto adjacent to the groove bot-roms.

' HAROLD w, SEMAR. v