US3446480A

US3446480A - Turbine rotor

Info

Publication number: US3446480A
Application number: US602795A
Authority: US
Inventors: Calvin W Emmerson; George B Meginnis
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1966-12-19
Filing date: 1966-12-19
Publication date: 1969-05-27
Anticipated expiration: 1986-05-27
Also published as: DE1601568A1; GB1161298A; GB1161297A

Description

. 3May 27, 1969 TURBINE ROTOR Filed DSC. 19, 1956 Sheet of 2 ,5p-g.

cl:.w.MMRsoNfETA| 3,446,480 u y ATTO RNEY May 27, 1969 c.w. EMMERVSN ET AL 3,446,480

TURBINE RoToR Filed Dec. 19. 1966 sheet 2 012 ATTORNEY United States Patent O 3,446,480 TURBINE ROTOR Calvin W. Emmerson, Mooresville, and George B. Meginnis, Indianapolis, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Dec. 19, 1966, Ser. No. 602,795 Int. Cl. F01d 5/18 U.S. Cl. 253-39.15 Claims ABSTRACT OF THE DISCLOSURE A turbine wheel particularly adapted for cooling. Hollow air-cooled blades inserted through holes in the rim are retained by circumferential rings under the rim passing through holes in the blade bases. A sheet slightly spaced from the rim by projections defines a passage for cooling air between the sheet and the rim.

Our invention is directed to improving the structure of turbine rotors, with particular emphasis upon improving the cooling of such rotors so that very high temperature motive fluid may be used in the turbine and upon provisions for the use of lightweight blades formed from sheet metal.

The objects of our invention are to raise the temperature tolerance of turbines, to provide a lighter weight and more economical turbine blade and improved means for mounting lightweight blades on a turbine rotor, to provide improved structure for cooling the blade, to provide improved structure for cooling the surface of the rotor which is exposed to hot motive fluid, and to provide a high temperature turbine which dispenses with blade platforms and blade stalks and thus reduces the weight of the rotating structure.

The nature of our invention and its advantages will be clear to those skilled in the art from the succeeding detailed description and the accompanying drawings of the preferred embodiment of our invention.

FIGURE 1 isa sectional view of the radially outer portion of a turbine wheel and adjoining turbine structures, taken on a plane containing the axis of the turbine.

FIGURE 2 is an enlarged partial sectional view taken on the plane indicated by the line 2 2 in FIGURE 1.

FIGURE 3 is a sectional View, with parts cut away, taken on the plane indicated by the line 3 3 in FIGURE 1, and

FIGURE 4 is a fragmentary sectional view taken on a plane generally as indicated Iby the line 4-4 in FIG- URE 1.

The turbine rotor of FIGURE 1 includes a wheel 7 which may be mounted on a shaft (not illustrated). The wheel includes a radial web 9 and a rim 10 which denes flanges 11 and 13 extending from the forward or upstream face and the rearward or downstream face of the web, respectively. The rim is a structural part on which turbine blades 14 extending radially from the wheel are mounted. The blades, as will be clearly apparent from FIGURES 3 and 4, are of a cambered airfoil section having a curvilinear outline, one face being convex and the other concave. The particular contours of the blades are of a matter of design for a particular turbine, but turbine blades ordinarily are of a curved airfoil configuration, much as illustrated. These blades include a base or root 15, each of which extends into an opening 17 which goes through the rim and includes a slot across the radially youter part of the web 9. The openings 17 are of the same curvilinear cross section as the blades and are dimensioned to provide a sliding ilt for the blade root.

Each blade comprises three elements, a folded outer skin 18, a liner 19, and a root block 21, 21'. The blade skin is of relatively thin Sheet metal. In a typical blade of about three-inch span, the skin may be about 0.03 inch thick, and the liner, which is not a structural part, is of much thinner sheet metal, ordinarily about 0.01 inch thick. At the root end of the blade the liner fits closely within the skin and the root block lits closely within the liner. The liner and skin may be folded around the root block, and all three of these are rigidly fixed together by some such process as brazing, diffusion bonding, or welding. Thus, in effect, the blades are lightweight hollow airfoils with a solid root portion for mounting in the Wheel. The openings in the wheel to receive the blades may be formed by electrochemical machining or any other suitable process. The root block is made in two parts 21 and 21' to provide an air entrance 24 through the blade root. Obviously, the air entrance 24 need not extend all the way across the interior of the blade and, therefore, the root block may be one piece, if desired.

The mounting of the blades involves

circumferential holes

31 and 32 extending through the two portions of the root block. These holes receive

circumferential rings

33 and 34, one disposed at each side of the web 7. The rim portions 11 and 13 have circumferential grooves 35 and 36 which it the outer portion of the

rings

33 and 34, locate the rings, and receive the radial load due to centrifugal force on the mass of the blades and the retaining rings. These retaining rings are preferably complete circles with one break 38 (FIGURE 4). The blades are installed `by extending them individually through the rim with the gaps in the retaining rings aligned with the particular blade opening 17, then indexing the rings through the

holes

31, 32 in the blade. This procedure is continued until all the blades are secured in place.

The

rings

33 and 34 may be locked so that the gaps 38 cannot realign with a blade root in any suitable way, but We prefer for this to be accomplished by wheel shrouds. The wheel 7 bears a shroud 41 on its forward face and a shroud 42 on its rear face, These shrouds are piloted on the wheel within

shoulders

43 and 44, respectively, and are retained by bolts 45. The forward shroud 41 bears ribs 47 on the Wheel face and denes radial passage's 49 between the shroud and the Wheel through which air is supplied to the wheel rim from a conduit 51 concentric with the wheel axis. Conduit 51 projects from fixed turbine structure such as a diaphragm 52 and the shroud 41 includes a labyrinth seal 53 around the inlet 51. It may also have a lip 54 in close proximity to a flange 55 on the diaphragm to exclude hot gas from the space between the shroud 41 and diaphragm 52. The outer margin of shroud 41 includes a rearwardly directed flange 56 which is received in a circumferential groove in the forward face of rim 10, and retains a sealing ring 57. The rear shroud 42 is disposed in close proximity to the rear face of rim 10 and is in semi-sealing relation with a downstream structure 58 which may be xed or may rotate with wheel 7.

Blade retaining rings

33 and 34 are locked in place upon completion of the assembly by a lug 91 on Ishroud ring 41 and a lug 92 on shroud ring 42,

these entering the gaps 38 of the rings between two of the blade roots.

Thus, the outer portion of shroud 41, the turbine wheel web, and flange 11 define an annular cooling air plenum 59 to which air is circulated through passage 49 and from. which it can flow through a slot 60` in the wheel rim and the passage 24 in the blade root into the blades. We may now consider the structure for cooling the surface of the rim which is exposed to the hot motive fiuid and for isolating the structural part of the rim from the motive fluid and for cooling part 10. The outer surface of the rim is formed by any suitable process such as photoetching or chemical milling, with spaced projections 61 which may be, in this instance, about 0.1 inch Iwide and 0.04 inch high. A thin sheet metal ring 62 about 0.02 inch thick is disposed over the outer surface of the rim and a portion of the forwavd face of the rim, supported by the projections 61 and bonded to them by high temperature brazing, welding, or other process. It will be seen that a labyrinthine path for cooling air is defined between the rim 10 and cover sheet 62 and between the projections 61 for cooling air. This cooling air is fed from the chamber 59 within the rim through a number of radial passages 65 into a small annular `cham-ber 66 at the leading edge of the rim, from which it flows rearwardly under the cover sheet I62, and exhausts through a number of small ports 67 downstream of the blades. The size and number of the

passages

65 and 67 can be chosen to cause the desired rate of circulation of the cooling air under the sheet 62. Because of the relatively narrow passage and also because of the projections 61, efficient transfer of heat from the cover sheet 62 to the cooling air is effected, and very effective cooling may be achieved.

It is preferred in most cases, to avoid loss of rim cooling air around the blades, to provide a continuous land 68 around each blade opening 17, of the sarne height as projections 61. This may be accomplished during the formation of the projcetions. The ring 62 is bonded to lands 68.

It should be noted that projections y61 and lands 68, or either of them, may be provided on the inner surface of ring 68 instead of the outer surface of the wheel rim. Also, projections 61 may be distributed in any desired pattern other than the rectilinear one illustrated.

Considering the blade structure in more detail, the outer sheet or skin 18 of the blade before folding into the blade is likewise treated to provide numerous closely spaced projections 71 distributed o'ver most of the interior surface except the root. The tip portion of the blade has radial ridges 73 rather than the projections 71. The projections 71 provide accurate control over the spacing of the liner 19 from the blade skin. Typically, the skin 18 may be originally 0.05 inch thick and the base portion and the skin between the projections and ridges may be etched away about 0.02 inch. As previously pointed out, the liner 19 is in contact with the smooth skin within the root but is spaced from the blade through most of the span of the blade. The liner is folded and has a 'welded or otherwise constructed seam 76 at its trailing edge and likewise a seam 77 at its outer en-d so that this is closed. Air entering the liner is distributed to cool the blade through a radial row of small holes 78, preferably about one hundredth of an inch in diameter, in the leading edge of the liner. The cooling air discharged from these holes impinges against the inner surface of the leading edge of the blade, which generally is an area of maximum transfer of heat from the motive fluid to the blade, The blade skin has a welded or otherwise formed seam 81 at the trailing edge which is interrupted by notches 82 in the trailing edge portion of the convex side of the blade to provide outlets for the cooling air. Thus, the cooling air, after impinging in the leading edge, ows rearwardly through the passages 85 defined between the blade and liner to the outlets 82.'

Some part of the cooling air also issues from the open end 86 of the blade, passing over ridges 73. As with the rim, the projections 71 on the inner surface of the blade maintain an accurately controlled small clearance between the blade and liner and improve heat transfer from the blade wall because of the additional surface provided by the projections. The liner is fixed to the skin only at the root. Internal air pressure will maintain the remainder of the liner against the skin.

The structure of our invention is very well suited to a rotor of drum type, in addition to disk rotors. Also, holes may be put wherever desired or needed in the liner 19 to direct more cooling air to critical areas of the blade, such as the trailing edge, for example.

It should be apparent from the foregoing that the structure described is particularly suited to endurance of high temperature motive fluid and to effective cooling with minimum use of coolant and that it furthers the use iof a structure of light weight as compared to the usual structure lwith blade platforms.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, as many modifications may be made yby the exercise of skill in the art.

We claim:

1. A turbomachine rotor comprising, in combination, a rotor body in the form of a body of revolution about an axis and having an outer and an inner surface, blades spaced circumferentially of and extending radially from the body, the blades having a curvilinear outline in crosssection, the body having a ring of radial openings distributed around its periphery, the holes extending through the body and being shaped to Ifit the curvilinear blade cross-section, each blade including a root end of said curvilinear outline extending into a said opening and having a pair of holes spaced axially of and extending circumferentially of the body through the root end radially within the body, and a pair of blade retaining rings extending circumferentially of the body through the holes, the rings being in position to engage the radially inner surface of the body.

2. A rotor as recited in claim 1 in which the said rotor body is the rim of a turbine wheel.

3. A rotor as recited in claim 2 in which the rim extends from each face of the wheel and one ring is disposed at each face of the wheel.

4. A rotor as recited in claim 2 including also shrouds fixed to the faces of the wheel, and in which each retaining ring has a gap, and including means on the shrouds engaging the retaining rings within the gaps to lock the rings circumferentially of the rotor.

5. A rotor as recited in claim 1 in which the rotor body is provided with internal circumferential grooves to receive the retaining rings.

6. A turbomachine rotor comprising, in combination, a rotatable body defining a blade-mounting portion, blades extending from the said portion of the body, the said portion being adapted to provide one boundary of a motive fluid path in operation of the rotor, the said portion having a relatively thin nonstructural sheet extending over the portion and between the blades and having a relatively thick structural part closely underlying said Sheet, the blades being supported on said structural part and extending through said sheet, means fixing said sheet to said part including projections ldistributed over one and extending fromv one to the other of said sheet and said part to provide passages between the sheet and part and around the projections distributed over the area of the portion between the blades, and means for circulating a cooling fluid through said passages.

7. A turbomachine rotor as recited in claim 6 in rwhich the last-recited means includes means for admitting a coolant through the structural part and means providing for `discharge of the coolant through the sheet spaced 5 6 from the means for admitting the coolant so that the References Cited coolant circulates through the said passages: UNITED STATES PATENTS 8. A turbomachine rotor as reclted 1n claim 6 lnclud- 2 601 969 7/1952 Ea t an t l 253 39 15 f dtt ltr 'd ae d' t Sm ea. -1. lng means or a m1 mg coo an o sai pass g s a Jacen 2,779,565 1/1957 Bruckmann Zig-39.15

the leading edge of the blades and means for discharge 5 2,840,299 6/ 1958 Paetz. of coolant from sald passages adjacent the traillng edge 2,888,243 5/1959 Pollock.

of the blades.

9. A turbomachine rotor as recited in claim 6 in which 3010696 11/1961 Everett' the said sheet is of the order of 0.02 linch thick. EVERETTE A. POWELL, JR Primary Emmi-nen 10. A turbomachine rotor as recited in claim 6 in 10 which the said projections include a continuous land ex- U.S. C1. X.R.

tending around each blade. 253-77