US2649278A - Rotor construction for fluid machines - Google Patents

Description

Aug. 18, 1953 E. A. STALKER ROTOR CONSTRUCTION FOR FLUID MACHINES Filed July 15, 1948 IN V TOR.

Patented Aug. 18, 1953 UNITED STATES PATENT OFFICE ROTOR CONSTRUCTION FOR FLUID MACHINES This invention relates to rotor construction for elastic fluid machines of the type wherein there is an interchange of energy between the rotor and a fiuid.

An object of the invention is to provide a low cost type of construction for turbine and compressor rotors and stators.

Another object is to provide a rotor wherein thermal stresses are substantially reduced.

Still another object is to provide a rotor structure for fluid machines of the compressor or turbine type which is readily made at low cost.

Other objects will appear from description, drawings and claims.

Fig. 1 is a fragmentary axial section of a turbine rotor according to the invention, shown in relation to a fragment of the outer case;

Fig. 2 is a fragmentary development of the rotor blades;

Fig. 3 is an axial view of one of the blade plates;

Fig. 4 is a fragmentary perspective of the turbine rotor;

Fig. 5 is a perspective of an inner shroud plate; and

Fig. 6 is a fragment of a junction of an inner shroud and rotor plate.

Present day turbine construction is very costly. In large part this is due to the fine machining put into individual parts, each of which are handled individually. The blades for instance are made individually and since they have cross section contours which are bounded by streamline curves, they must be cut on special machines at a relatively slow rate. The blades must have special root ends for attachment to the rotor hub which must in turn be accurately machined to receive the root ends of the blades.

In contrast, in the present invention, the blade parts and hub are assembled from precision stampings. As is well known stampings are the cheapest metal construction known for quantity production.

Once the dies are procured, the stampings may be produced without skilled labor. The blade parts are integral with the central hub member so the blades do not have to be handled individually.

The parts require only placing in a fixture while they are welded, as by an automatic welder. They may be bonded by other means such as braz ing and the like.

The rotor is formed from several blade plates, each of which carries a portion of each blade. At each side of the group of blade plates is a rotor plate sometimes called a side disk. The upstream and downstream rotor plates are joined by irmer 2 or hub shrouds extending from one rotor plate to the other.

In this invention the blades are made from thin sheet metal defining a hollow interior. Since the blade walls are thin, the blades are very light and can dispense with blade bases. Since no blade bases are employed and the blade does not rely on attachment to the rim for support against centrifugal force, the rim structure also can be thin and of light weight. Further, since the blades and rim are of light weight and no heavy blade bases are present, the centrifugal loads accumulated radially inward are relatively small and consequently the supporting plates can be thin and light in weight. Thus by providing for cumulative lightness from the tips inward, the plates may be of sheet metal of the order of thickness of the blade walls.

The structure of this invention differs from the usual arrangement where solid blades impose heavy centrifugal loads requiring heavy blade bases. The heavy loads require a heavy hub rim made heavier by slotting to receive the blade bases. The portions of the rim between slots are unable to carry any peripheral stress and are consequently sources of more centrifugal load for the hub without any compensating load-carrying ability to be contributed to the hub.

The blades are attached by sheet metal elements to the hub structure so that the joint is a shear joint, subjected principally to a shear stress. This is important in providing great strength with light weight for the blade attachment and relieving the plate of heavy loads, such as other kinds of attachment impose. It is also important to have the shear joint radially inward a substantial distance from the rim of the hub structure.

In Figs. 1 to 3 the blade plates are It, l2 and [4. The plate it has the plurality of blade nose parts [8 disposed about its periphery. The plate 12 has the middle body blade parts 26 disposed about its periphery. The plate I4 has the tail blade parts 22 about its periphery.

The nose and middle body parts each are channel or trough-like in form with the trough opening toward the downstream or rear side of the rotor.

The blade plates are assembled in axial tandem or chordwise relation with the middle body parts nested in the nose parts. The tail part is made to nest in the middle body portion. These parts form a plurality of blades 26 having the slots 28 and 30 on one side and the slots 32 and 34 on the otherside.

The tail parts are preferably solid as shown in Figs. 1 and 2.

The blade parts are preferably spaced axially so that the slots have a proper width for the emission of a flow of cool fluid to separate the hot gases of the turbine from the blade walls. However the slots may be closed by fusing the walls of the blade parts together.

The gaps between blades are closed by the inner shrouds it which extend axially from the front rotor plate or side disk 42 to the rear rotor plate or side disk I'hese are bonded together along the flanges .8 and B of the rotor plates and the entire blade supporting structure is thus formed of sheet metal with the shrouds forming the rim of the hub structure.

The shrouds have flanges d5 along the blade contour to resist deformation from centrifugal stresses.

The shroud elements as a group comprise the rotor shroud or rim means 3!.

The inner shroud is preferably not fixed to the sides of the blades but by being properly contoured it closely conforms with and fits snugly against the blade walls.

The shrouds between all the blades provide for the guidance of the flow between the blades. In fact these shrouds as a group define an inner cylindrical boundary of the annulus whose outer boundary is the turbine case 59 which closely conforms with the tip ends of the blades.

As shown in Fig. 6 the inner shrouds 48 may be made with an extension Mia which is folded under the flanges Q5 and 48. The joint is then resistance welded. Because of the folding under the Weld is not in tension as is the case in Fig. 1 where the shroud simply rests on the upper surface of the flange of the closure plate. If the turbine is required to have a long life it is better to use a weld in shear rather than tension because of fatigue characteristics.

The hub structure includes rotor plates, the blade plates, and a suitable hub element 55 which is fixed to the shaft 52. The fixing may be done by any method but brazing or silver soldering is preferred. Welding would also be a satisfactory method.

Cooling air is introduced into the rotor assembly through the slot 5 in the front rotor plate for emission through the blade slots.

The tip ends of the blades are closed by folding over two leaves such as 66 and ti to butt along the center line. The leaves normally are not fused together along this line. lhe small leakage of cooling air through any crevice between leaves would be unimportant.

As discussed above the blade parts extend inward through the peripheral surface of the rotor formed by the shroud elements 50. Throughout this extension the blade parts remain substantially free to shift relative to each other by small amounts. Since the blade plates are cooled by conduction and by the fiow of cooling air within, thermal strains are not significant in them. The blade parts are the highly heated elements and since they will be heated and cooled at different rates it is important that theycan expand .or contract at different rates. The division of the blades into independent parts permits relative movementof the parts, not only the portions outside the rotor shroud di but even of the parts extending for a substantial distance inward'from the rotor shroud substantially to the locality where the relative movement will lose significance as a cause of rupture of the material.

It is undesirable to have the blade parts fixed to the shroud of the rotor because then the shroud will try to restrain the relative movements of the parts and one or the other may be cracked or distorted by the thermal strains.

Although the rotor structure has been discussed particularly with respect to gas turbines it is to be understood that the same construction can be used for compressor rotors particularly axial flow compressor rotors. It is also to be understood that the blade parts may be fitted together to exclude blade slots entirely or on either side of the blade.

Cross reference is made to my copending application, Serial No. 42,565, filed August 5, 1948, covering similar subject matter.

While I have illustrated a specific form of this invention it is to be understood that I do not intend to limit myself to this exact form but intend to claim my invention broadly as indicated by the appended claims.

I claim:

1. In combination, in a bladed axial flow rotor, a plurality of blade plates, each having a plurality of blade parts spaced peripherally thereabout, each said blade part having a radially extending trough opening rearward, said plates being positioned in axial relation to nest some said blade parts each in the trough of another said blade part, and means fixing said blade parts in blade relation.

2. In combination, in a bladed axial flow rotor, a plurality of blade plates, each having a plurality of blade parts spaced peripherally thereabout, each said blade part having a radially extending trough opening rearward, said plates being positioned in axial relation to nest some said blade parts each in the trough of another said blade part in axially spaced relation to form slots between said blade parts, and means fixing said blade parts in blade relation.

3. In combination, in a bladed axial flow rotor, a plurality of blade plates, each having a plurality of blade parts spaced peripherally thereabout, each said blade part having a radially extending trough opening rearward, said plates being positioned in axial relation to nest some said blade parts each in the trough of another of said blade part in axially spaced relation, and a trailing edge blade plate having blade parts spaced peripherally thereabout with each last said blade part positioned within the trough of the last downstream said blade part.

4. In combination in a turbine rotor having axially spaced side disks, a hub shroud, a plurality of sets of blade parts disposed peripherally about said rotor, each said set forming a blade, and a blade supporting structure within said rotor spaced inward from said shroud, said blade partsextending inward through said shroud to said supporting structure within leaving said parts substantially free to move relative to each other outward from said structure, said structure comprising a plurality of axially spaced plates spaced inward from said side disks.

5. In combination, in a bladed axial flow rotor, a plurality of blade plates forming hollow'blades, each plate having a plurality of blade parts spaced peripherally thereabout, each said blade part having a radially extending trough opening rearward, said plates being positioned in axial relation to nest some said blade partseach in the trough of another said blade part in axially spaced relation to form slots betweensaid blade parts, said blade parts being fixed in blade relation, and means to admit cooling air into the interior of said blades for flow outward through said slots.

6. In combination in an axial flow turbine rotor, a hub structure comprising a hub element, axially spaced side plates fixed to said hub element, and a rim peripheral surface extending between said side plates, a plurality of hollow blades whose walls are formed from thin sheet metal blade plates, said blades being spaced peripherally about said rim surface and extending radially outward therefrom, each said blade having a radially inner part fixed thereto and of the order of thickness of said blade walls, said internal parts extending inward through said rim surface, and fused metal means fixing said parts directly to said hub element forming a joint subject to stress in shear.

7. In combination in any axial flow rotor adapted to interchange energy with a fluid, a hub structure including a hub element for driving said rotor, axially spaced side plates fixed to said element and extending radially outward therefrom, a sheet metal rirn fixed to said side plates adjacent the peripheries thereof and extending between said side plates from the front side to the rear side of said rotor, a plurality of hollow blades spaced peripherally about said rim and extending radially outward therefrom, said riin forming a pressure sustaining surface for directing fluid through between said blades, said blades being defined by walls of thin sheet metal extending inward through said rim, said blades having radially inwardly extending sheet metal parts fixed to opposite said blade walls and extending inward through said rim beyond said blade walls, and fused metal means fixing each said part to said hub structure at a locality a substantial distance radially inward from said rim.

8. In combination in a bladed axial flow rotor adapted for interchanging energy with a fluid, a hub structure, a plurality of blade plates each having a plurality of blade forming parts spaced peripherally thereabout, said plates being positioned in axial relation to locate a rearward blade part in tandem relation with respect to a corresponding forward blade part, both said blade parts having a continuous wall at their respective nose portions extending transversely of the blade from the upper to the lower surface thereof, said blade plates extending inwardly from said continuous walls to said hub structure and supporting said blade plates thereon.

9. A light weight rotor for an axial flow elastic fluid machine having an enclosing casing and in which energy is exchanged with the fluid flow comprising a plurality of angularly fixed blades peripherally spaced about said rotor and having tip ends in operatively conforming relation with said casing, said blades being formed of hollow sheet metal construction providing low weight and limiting the centrifugal forces developed therein during operation at high tip speeds with accompanying flow of said fluid in a generally axial direction with increased density and pressure, sheet metal rim means extending between and closely conforming with the walls of said blades from the leading to the trailing edges thereof and from blade to blade at localities thereon outwardly adjacent the root ends thereof to sustain a substantial diiference in static pressure and density in said fluid flowing between said blades, said blades having parts thereof extending radially inwardly of said rim means for supporting the centrifugal loads developed in said blades in operation, and a hub structure including sheet metal means connected to said in wardly extending parts and to said rim means to support and sustain the limited centrifugal forces developed in said blades and rim means during operation while leaving said rim means substantially free of the centrifugal forces developed in said blades during operation.

EDWARD A. STALKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 648,158 Zoelly Apr. 24, 1800 702,461 Nadrowski June 17, 1902 874,398 De Ferranti Dec. 24, 1907 1,210,978 Parsons et al Jan. 2, 1917 1,601,402 Lorenzen Sept. 28, 1926 2,232,670 Barrett Feb. 18, 1941 2,271,971 Doran Feb. 3, 1942 2,335,091 Utz Nov. 23, 1943 2,428,728 Watson Oct. 7, 1947 2,506,581 Cowles May 9, 1950 FOREIGN PATENTS Number Country Date 593,093 Germany Feb. 21, 1934 810,883 France Jan. 9, 1937

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