US3588277A - Bladed rotors - Google Patents

Abstract

A ROTOR COMPRISING TWO AXIALLY SPACED DISCS, A PLURALITY OF RADIALLY EXTENDING VANES BETWEEN THE DISCS WHICH JOIN THE DISCS TOGETHER, PREFERABLY THE VANES EXTEND BEYOND THE DISC AS LUGS WHICH DEFINE GUIDEWAYS FOR RECEIVING BLADES, WHEREBY THE RADIAL FORCE OF THE ROTATING BLADES IS TRANSMITTED IN TENSION TO THE VANES AND THEN AS A SHEAR LOADING INTO THE DISCS OVER A RELATIVELY LARGE AREA. IT IS ALSO PREFERABLE THAT ONE OF THE DISCS BE ANNULAR SO THAT COOLING AIR CAN ENTER AT THE INNER PERIPHERY AND BE IMPELLED THROUGH THE PASSAGEWAYS DEFINED BY THE VANES AND THEN ENTER THE BLADES THROUGH HOLES IN THE BASES OF THE TANGS.

Description

United States Patent [72] Inventors Werner E. Howald 2,438,998 4/1948 Halford 60/392 Cincinnati; 2,947,512 8/1960 Jones et a1. 415/114 1 N 'gg g' Mason 0M0 Primary Examiner-Samuel Feinberg [21] g M 16 I966 Attorneys-Melvin M. Goldenberg,Frank L. Neuhauser, [22] e Oscar B. Waddell, E. S. Lee, 111, G. R. Powers and Derek P. [45] Patented June 28, 1971 Lawrence [73] Assignee General Electric Comapny [54] BLADED ROTORS I 6 Claims, 5 Drawing Figs.

ABSTRACT: A rotor compnslng two axially spaced discs, a [52] U.S. Cl. 416/96, m m f radially extending vanes between the discs which 416/97 416/2M join the discs together; preferably the vanes extend beyond the [51] lnt.Cl. Fflld 5/08, disc as lugs which d fi guideways f receiving blades Fold 5/ whereby the radial force of the rotating blades is transmitted [50] Field ol Search 253/39.l5, in tension {0 the vanes and hen as a shear loading into the 39 (F-R); 416/961 97 discs over a relatively large area. It is also preferable that one of the discs be annular so that cooling air can enter at the [56] References CM inner periphery and be impelled through the passageways UNITED STATES PATENTS defined by the vanes and then enter the blades through holes 2,405,190 8/1946 Darling 60/3917 in the bases of the tangs.

/l I' II KY\\\ \\\\m7 PATENTED JUH28 I97! SHEET 1 OF 2 INVENTORS WERNER E. HOWALD JACK D. WRIGHT PATENTEUJUH28IH7E 3588277 SHEET 2 OF 2 INVENTORS WERNER E. HOWALD JACK o. WRIGHT BY "V k p 1 BLADED ROTORS The present invention relates to improvements in bladed rotors employed in axial flow turbines and compressors.

In gas turbine engines, particularly those employed for aircraft propulsion, engine weight is of particular concern. One way in which weight reduction can be obtained is to reduce the size and mass ofindividual components of the engine.

Toward this broad end of reducing gas turbine engine weight, one object of the present invention is to substantially reduce the weight of the turbine rotor normally employed in such engines.

Another and broader-object of the invention is to provide an improved turbine rotor which for a givensize and mass has greater strength, reliability, and operating life, particularly at extremely high rates of rotation which have become essential in present engine designs.

Another object of the invention is to attain the above ends and further provide for the passage of cooling air through the blades of the turbine rotor in order that they will not be overtemperatured when driven by a gas stream which is at an elevated level.

These ends are attained by a turbine rotor which comprises two axially spaced, generally parallel discs. These discs are joined by vanes formedintegrally therewith and extending radially thereof. A plurality of blades are angularly spaced about and project from the peripheries of the discs.

In another aspect, the objects of the invention may be attained by a rotor comprising a pair of discs having radial vanes therebetween. One of the discs is annular to define, in part, an inlet for cooling air which passes between the discs and then enters passageways in blades secured to the discs.

Preferably lugs are formed as integral extensions of these vanes, beyond the peripheries of the discs. These lugs span the discs and are also integral therewith. The lugs define tapered, dovetailed guideways, extending generally axially of the rotor. The blades have tangs on which are formed bulbous tenons slidingly received by the guideways defined by the lugs. The radial forces acting on the blades, as a result of centrifugal force, are taken as a tension loading on the lugs. This loading is transmitted as a tension loading into the discs and the vanes, and from the vanes as a shear loading into the discs, thereby attaining a high strength rotor structure.

It is further preferred that both discs be annular and that a shaft portion be formed integrally with the inner periphery of one of the discs and extend through the other disc in an axial direction for connection with an element to be rotated thereby. The inner periphery of the other disc is spaced from this shaft portion to define an inlet for cooling air to pass between said disc to said blades. The vanes function to pump the cooling air and assure a continuous flow thereof through passageways provided in the blades. The entrances of the blade passageways are formed at the base of the tangs in communication with the passageways defined by the vanes.

The above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawings and the novelty thereof pointed out in the appended claims.

In the Drawings:

FIG. 1 is a longitudinal section through a turbine embodying the present invention;

FIG. 2 is a fragmentary view partially in section taken generally on line IIII in FIG. 1;

FIG. 3 is a section, on an enlarged scale, taken generally on line Ill-Ill in FIG. 2;

FIG. 4 is a perspective view, on a further enlarged scale, ofa portion ofthe turbine rotor with portions thereofbroken away and in section; and

FIG. 5 is a fragmentary perspective view of the portion of the turbine rotor which defines the inlet for cooling air passing therethrough.

Gas turbine engines conventionally comprise an axial flow compressor which discharges compressed air to a combustor to generate a hot gas stream. In FIG. 1 duct walls 10 and 12 represent the structure which defines the annular flow path of such a hot gas stream discharged from a combustor. Nozzles 15 direct this hot gas stream to drive a turbine 14 which comprises a plurality of blades 20 projecting from a rotor 22. The rotor 22 is connected to a tubular shaft 16 which is appropriately journaled, with bearing 18 supporting the aft end of the shaft relative to a frame member 19. The shaft 16 is in turn connected to the rotor (not shown) of the axial flow compressor of the gas turbine engine. The turbine 14 thus performs the usual function of driving the compressor rotor of a gas turbine engine.

The rotor 22 is preferably integrally formed and comprises a tubular shaft portion 24, having a flange 26 through which bolts 28 extend in securing the turbine rotor to the drive shaft 16. An annular disc 30 extends radially outwardly from the tubular shaft portion 24. A second disc 32 is joined to the disc 30 by integral vanes 34, which extend radially outwardly. Bulbous lugs 36 are formed beyond the outer peripheries of the discs 30 and 32 as integral continuations of the vanes 34. The lugs 36 also span the discs 30, 32 and are integral therewith. Adjacent lugs 36 define tapered dovetail guideways or slots which receive correspondingly shaped bulbous tangs or tenons 38 formed on the blades 20. As will be evident from FIGS. 3 and 4, the slots defined by the lugs 36 are preferably arcuate and approximate the outline of the airfoil shaped blades 20.

The blades 20 are axially retained in the rotor 22 by retainer plates 40 and 42. The plates 40 and 42 are secured to the rotor 22 by bolts 44 which extend through the lugs 36. The retainer plates 40, 42 also have lips 46, 48 which engage shoulders on the discs 32, 30 respectively. The plates 40 and 42 also extend outwardly to platforms 50 which define the inner surface of the hot gas stream flow through the turbine wheel. The platforms 50 are cut away at one end to facilitate assembly of the blades into the arcuate guideways on the rotor. Plate 40 has fingers 51 which fill in these cut away portions of the platforms. It will also be seen that the retainer plate 40 has a labyrinth seal member 52 formed integrally therewith. This seal minimizes flow of hot gases into a chamber 54 which is connected to a source of cooling air usually derived from the engine compressor.

This cooling air is employed to prevent overtemperaturing of the blades 20. Cooling air enters an annular inlet 56 defined by the inner periphery of the disc 32 and the shaft portion 24. An inducer comprising blades 58 integral with rings 60 (FIG. 5) is mounted in the inlet 56 by means of a snapring 62 and facilitates entry of air between the discs 30 and 32. The vanes 34 then function to pump the cooling air toward the blades 20. This cooling air then passes through passageways 64 in the tangs 38, circulates through the hollow interior of the blades 20 and is discharged through the outer ends of the blades into the hot gas stream. It will, of course, be evident that other forms of blades having cooling passageways therein or therethrough may also be employed.

The described construction of rotor 22 not only provides an effective means for conveying cooling air to the blades 20, but of equal, if not greater, importance are its structural features which enable substantial savings in weight for any given set of operating parameters.

In discussing these structural features, it will first be pointed out that turbine rotor speeds are desirably extremely high, particularly in finely tuned gas turbine engines used for aircraft propulsion. The stresses induced into the rotor 22 as a result of centrifugal force far exceed the stresses attributable to the torque which is to be transmitted to the compressor shaft. These centrifugal forces thus are the limiting parameter in providing sufficient strength in the rotor 22.

Considering first the centrifugal forces on the blades 20, such forces are carried in tension through the narrow neck n (FIG. 4) at the base of the tangs 38. The arcuate shape (approximating that of the blades 20) of these tangs minimizes stress levels as substantially all loading is taken in tension. The mating, tapered, tenon and dovetail portions of the tangs 38 and lugs 36 mutually load each other in compression as the radial forces are transmitted in shear to the lugs 36. The radial stress on the lugs 36 is distributed as a tension loading throughout their axial width across their bases b. The bases b blend with the outer peripheries of the discs 30, 32 so that a portion of the radial stresses on the lugs 36 is carried as a radial tension loading on the discs 30, 32. The remainder of the radial stresses on the lugs 36 is carried as a tension loading on the vanes 34. This tension loading of the vanes 34 is then transmitted to the discs 30, 32 by a shear loading which is distributed over a relatively wide area to minimize stress values. Dotted lines a in FIG. 4 illustrate the approximate shear stress distribution between the discs 30, 32 and vanes 34 resulting from radial forces on the latter. It will be noted that the shear stress attenuates radially inwardly of the discs 30, 32. The width of the vanes 34 is made greatest at the outer peripheries of the discs 30, 32 where shear forces are greatest (see also FIG. 1). The vanes then taper to a narrower width as the shear forces decrease. In this fashion unit stress is minimized and at the same time weight is also minimizedv The vanes 34 continue radially inwardly, with a constant width, beyond a point where the shear stresses are attenuated, in order to give further rigidity to the discs 30, 32 which are joined thereby.

The described integral construction of the rotor 22 assures that radial stresses are taken in substantially pure tension or in shear over a relatively large area. This is also true as to any stresses which would be generated in the event there were differential radial expansion of the discs 32 either because of centrifugal force or thermal differences.

Another factor to be considered is that the extreme rates of rotation produce very high tangential hoop forces on the discs 30, 32. The described construction minimizes the resultant hoop stress by essentially eliminating any cause of stress concentration. Thus it will be noted that the annular discs 30, 32 have structural integrity, being free of any holes, notches or the like which would cause stress concentrations. in this connection, while the lugs 36 are integrally formed with the discs 30, 32, they arenot a structural component thereof, in that they are not subjected to tangential hoop loading. Thus the provision of holes for the bolts 44, through these lugs, does not weaken the rotors ability to withstand the hoop stress resulting from centrifugal forces.

It is preferred that the rotor 22 be integrally formed, as described. This, however, does not mean that the rotor must initially comprise a single element. For example, the disc 32 and a portion of the vanes 34 could be separately fabricated and the vanes then joined by brazing, diffusion, bonding, or the like.

Thus it will be recognized that these and other variations from the described embodiment are within the scope of the present inventive concepts which is to be derived solely from the claims herein.

Having thus described the invention, what is claimed as novel and desired by Letters Patent of the United States is:

We claim:

1. A rotor comprising:

two axially spaced, generally parallel discs;

radially extending vanes integral with the discs, disposed between said discs and joining said discs together;

a plurality of blades projecting from and angularly spaced about the periphery of said discs; and

said blades being connected to said vanes whereby radial centrifugal forces on the blade will be taken, at least in part, as a tension loading on the vanes, which, in turn, is transmitted as a shear loading to the discs over a relatively large area.

2. A rotor as in claim 1 wherein:

lugs are formed as integral extensions of said vanes beyond the peripheries of said discs, said lugs further spanning said discs and being integral therewith;

said lugs defining tapered, dovetail guideways extending generally axially of said rotor and, further wherein; said blades have tangs with tapered tenons slidingly received by said guideways; and

whereby radial forces acting on said blades are taken as a tension loading on said lugs which is transmitted as a tension loading into said discs and vanes and from said vanes as a shear loading into said discs.

3. A rotor as in claim 1 wherein both discs are annular:

a shaft portion is integral with the inner periphery of one disc and extends in an axial direction through said other disc for connection with an element to be rotated thereby; and

the inner periphery of said other disc being spaced from said shaft portion to define an inlet for cooling air to pass between said disc to said blades.

4. A rotor as in claim 1 wherein:

lugs are formed as extensions of said vanes beyond the peripheries of said discs, said lugs further spanning said discs and being integral therewith, said lugs defining tapered, dovetailed guideways extending generally axially of said rotor;

said blades have tangs with tapered tenons slidably received by said guideways;

whereby radial forces acting on said blades are taken as a tension loading on said lugs which is transmitted in tension directly into said discs and vanes and from said vanes as a shear loading into said discs, and further wherein;

both of said discs are annular;

a shaft portion is integral with the inner periphery of one disc and extends in an axial direction through said other disc for connection with an element to be rotated thereby;

the inner periphery of said other disc being spaced from said shaft portion to define an inlet for cooling air to pass between said discs to said blades;

said blades having air cooling passageways extending from the bases of said tangs therethrough; and

whereby cooling air entering said inlet will be pressurized by the pumping action of said vanes to be discharged through said blade passageways.

5. A rotor as in claim 4 wherein, said vanes have a maximum cross-sectional width at the bases of said lugs and are progressively tapered to a narrower cross-sectional width as they extend inwardly to a point where the shear loading thereon is substantially attenuated, said vanes having a substantially uniform cross-sectional thickness inwardly from such point and continuing to the inner periphery of said other disc.

6. A rotor as in claim 4 wherein, said discs are solid from their inner to their outer peripheries.

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