US3294364A

US3294364A - Rotor assembly

Info

Publication number: US3294364A
Application number: US163926A
Authority: US
Inventors: Max W Stanley
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1962-01-02
Filing date: 1962-01-02
Publication date: 1966-12-27
Anticipated expiration: 1983-12-27

Description

M- W. STANLEY ROTOR ASSEMBLY Dec. 27, 1966 Filed Jan. 2, 1962 INVENTOR. MAM W. 579N115 V United States Patent 3,294,364 ROTOR ASlEMllLY Max W. Stanley, Fairlield, Ohio, assignor to General Electric Company, a corporation of New York Filed fan. 2, 1962, Ser. No. 163,926 4 Claims. (Cl. 25377) extending radially from a rotor wheel across the annular gas passage for either driving or being driven by this gas flow. The blades generally comprise an airfoil and shank portion with a base for attachment of the blade in some manner to the rotor wheel. It is subsequently necessary that substantially all of the gas flow pass by the airfoil portion of the blades to provide a high efficiency rotor assembly, therefore sealing is provided where feasible, such as around the outer peripheries of the blades.

Another critical area where scaling is critical is between adjacent blade shanks, which extend between the airfoil portions of the blades and the rotor wheels. Such a bafile here seals against the axial flow of gas, however since the effective weight of such a baffle may be multiplied thousands of times by centrifugal force acting on the assembly during operation, a lightweight construction is imperative. In addition, such a baffle should provide ease of assembly of the blade structures and the rotor wheel and also should be interchangeable to simplify maintenance on the assembly. Additionally, such a baffle may perform a damping function by limiting vibration between the adjacent blades thereby adding to the overall structural integrity of the rotor assembly.

In the past, rotor assemblies have generally utilized blades having circumferentially extending platforms between the shank and airfoil portions of the blades which serve to prevent the passage of gas radially along the blade axis and serve such other functions as damping vibration between adjacent blades. Further developments however have led to lightweight turbomachinery, particularly in turbomachines developed for aircraft, and it has been found advantageous to use fabricated blades and decrease the weight of the blade and rotor assemblies wherever possible. Naturally, solid platforms integrated structurally with the blades add weight to the rotor assembly by their own weight as well as added weight to the blade to support such heavier assemblies. However, in the past, such platforms have served an additional function of supporting a baffle as mentioned heretofore for sealing against the axial passage of gas between adjacent blade shanks. With the advent of the use of blades not having platforms integrated with the blade structure, the support of such bafiles becomes more of a problem, also the functions able to be fulfilled by such bafiles have increased. For instance, if no blade platforms are provided on the blades themselves, the bafile can be designed to damp vibrations between adjacent blades in addition to sealing against this radial and axial fiow of gas. Such bafiles must perform these functions and yet be of lightweight construction and if possible, self-supporting in some manner because if such baflies are supported by the blades, then additional structure must be added to the blade and to the blade support means to react the additional loading, all of this leads to a heavier rotor assembly.

It is accordingly a primary object of this invention to provide a lightweight rotor assembly for a turbomachine,

It is another object of this invention to provide a specific 3 ,294,354 Patented Dec. 27, 1966 lightweight baffle and blade assembly with means for assembly with a rotor wheel,

It is another object of this invention to provide a particular lightweight bafile construction which performs such functions as sealing against air flow, damping vibration between adjacent blades and is self-supporting on the rotor wheel.

In accordance with one embodiment of the invention, there is provided a rotor assembly comprising the combination of a rotor wheel with a plurality of rot-or blades having airfoil and shank portions attached extending radially from the wheel, with a bafile for preventing the axial and radial flow of gas adjacent the blade shanks comprising a first wall member normal to and surrounding the blade at the juncture of the airfoil and shank portions, with a second wall member extending between the first wall member and the rotor wheel on the upstream side of the blade, and two additional wall members extending transverse to the rotor wheel and on each side of the blade attached to the first and second wall members with separate attachment means to the rotor wheel.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of the rotor wheel and bafile assembly with the blade outlined in phantom,

FIG. 2 is a cross-sectional view taken along a plane normal to the rotor wheel axis and bisecting the rotor wheel at its midpoint,

FIG. 3 is a cross-sectional view of the baffle along the lines 3-3 of FIG. 1 with the rotor wheel and blade illustrated in phantom, and

FIG. 4 is an end view of the baffle from the downstream direction.

Referring now primarily to FIG. 1, therein is illustrated a turbine wheel 11 with attached radially extending blades 12 attached thereto by means of the base portions 13 interfitting with undercut axially extending grooves 14 in a manner well known in the art. The blades consist of a shank portion 17 extending from the base 13 with a small transition section 18 situated radially outward therefrom and connecting the shank with the airfoil portion 19. A turbomachine in which this rotor assembly may be utilized consists of substantially concentric cylindrical casing members (not shown) forming an annular gas passage for either a compressor or turbine section with the rotor assembly representing either a compressor or turbine rotor wherein the airfoil portions 19 of the blades extend across the annular gas passage to either drive or be driven by the primary gas flow of the turbomachine. The rotor wheel 11 is rotatably supported to revolve about the axis of the annular gas passage which generally coincides with the axis of the turbomachine.

The concentric casing members described heretofore extend axially with the outer casing member closely adjacent to the outer ends of the rotor blades and the inner casing member discontinued a short distance along a plane normal to the axis of the turbomachine to allow insertion of the rotor assembly with the casing extending immediately adjacent to the transition portion 18 of the blades so that just the airfoil portion of the blades extends through the gas passageway.

In view of the fact that platforms are not provided integral with the blade structure, the space between adjacent blades must be sealed to prevent the flow of gas radially along the blade shank in order to provide a continuous annular gas passageway. In addition, since an absolutely gas-tight seal is not possible between the edge 3 of the inner casing and the upstream edge of the rotor assembly because of thermal expansion, etc. the space between adjacent blade shanks must also be sealed to prevent the axial passage of gas therebetween and therefore around the annular passage in which is located the blade airfoil. To accomplish this, there is provided the baffle 22 consisting of a first wall 23 acting as a blade platform having an opening 24 therethrough fitting the contour of the blade at the transition portion 18 and thereby sealing against the radial passage of gas along the blade. To seal against the axial passage of gas, front wall 25 is provided extending between the upstream edge of first wall 23 and the rotor wheel 11. Additionally,

side walls

26 and 27 extend in an axial direction substantially transverse to the first wall 23 and the front wall 25 on each side of the blade shank to add structural rigidity to the bafiie assembly and to provide means for attachment to the rotor Wheel 11 as will be explained later. Inner diagonally extending walls 30 and 31 are provided extending from the top wall 23 on each side and adjacent to the opening 24 down to the

side walls

26 and 27 respectively. These walls provide added strength to the bafiie particularly against forces extending circumferentially and radially on the baffle and also add rigidity by reinforcing the front wall 25.

End walls

34 and 35 are provided on the downstream end of the baffle as illustrated in FIG. 4 connecting the edges of the top wall 23, side wall 26 and diagonal wall 30; also the top wall 23, the side wall 27 and the diagonal 31 respectively. The walls may be fastened together by any suitable means such as welding, brazing, riveting, etc.

To attach the baffle to the rotor wheel, the

side walls

26 and 27 have

base portions

37 and 38 respectively which when the bafiies are assembled in the manner illustrated adjacent one another around the periphery of the rotor wheel, the

base portions

37 and 38 of adjacent bafiies abut to form a base cooperating with the axially extending undercut groove 40 to hold the bafiie against being moved radially when being acted upon by centrifugal force during rotation of the rotor assembly. By this attachment means the baflie is allowed to be inserted axially with the rotor blade and securely held in position by reacting radially acting forces primarily through the

base portions

37 and 38 and by reacting axially directed forces, generally in the downstream direction, by the interaction of the front wall 25 and the rotor wheel and blade.

To assemble the rotor assembly, the bafile being of a lightweight thin-walled construction and having the downstream wall split between the

end walls

34 and 35 with the opening 24 extending across the top wall 23 to that cleavage in the downstream wall, the baffie may be sprung open sufiiciently by flexing the front wall 25 to allow insertion of the rotor blade such that the transition portion 18 extends through and aligns with the opening 24 as illustrated. A locking means (not shown) may be provided at a point adjacent the downstream edge of the opening 24 to lock the baffle around the blade if necessary. Thereafter, the baffle and blade may be simultaneously inserted in an axial direction into the rotor wheel with the base 13 on the blade fitting into the slot 14 and the

base portions

37 and 38 fitting into the groove 40 located adjacent the slot 14. In this manner the complete rotor assembly may be built up of individually assembled blade and bafile components in a manner allowing for both ease of assembly and removal thereby simplifying maintenance and replacement. Thereafter a locking pin 46 may be inserted which fits through a slotted opening 47 in the front wall 25 and aligns with the bottom or radially inward side of the slot 14 between the base 13 and the slot wall to extend axially through the rotor wheel. The pin may be provided with an enlarged head 48 on the upstream edge to overlie the adjacent portions of the front wall 25 so as to lock this front wall against the rotor wheel.

Thereafter the downstream edge of the pin may be bent or otherwise deformed against the downstream edge of the blade base 13 and the downstream face of the rotor wheel 11 to lock the complete assembly against axial movement. Since the base portions 13 of the blade and the

base portions

37 and 38 of the bafiles lock the bafiie and blade against radial movement, the complete rotor assembly is formed as one integral self-locking unit.

With the baifies so assembled, it may be readily seen that the abutting edges of the top wall 23, together with the top wall of the adjacent baffle, form a platform or wall extending between the blades to seal against radial passage of gas while the abutting front walls 25 form a substantially continuous upstream Wall preventing the axial passage of gas. If additional sealing is desired, an insert 50 may be attached to the side wall 27 as by brazing as illustrated in FIG. 1, which may thereafter be machined to precisely dimension the width of the top wall 23 for closer fitting of the top walls between adjacent blades. Or in the alternative as illustrated in FIG. 2, the side wall 27 may have an indented area 51 in which may be fastened a similar strip 52 which may subsequently be machined in the same manner to closely abut the adjacent side wall 26 of the next adjacent baflie for more complete sealing.

With the top walls 23 forming a substantially continuous mid-platform about the periphery of the rotor wheel at the transition portion 18 of the blades, any vibrations between adjacent blades will be clamped by these abutting walls 23. By use of the diagonal walls 30 and 31 additional strength is provided against circumferentially acting forces between adjacent blades thereby providing a substantially rigid rotor assembly. Furthermore, by making the bafiie self-supporting on the rotor wheel, the blade itself need not support the battle against radial movement and therefore the size and weight of the blade base and shanks may be reduced substantially; this has the added effect of allowing the blade shanks to be more flexible thereby reducing vibrational problems often encountered with the use of rigid blade shanks.

While particular embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention and it is intended to cover in the appended claims all such changes and modifications that come within the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A rotor assembly for an axial flow turbomachine comprising the combination of a rotor wheel having a plurality of axial-1y extending undercut grooves in the periphery thereof,

a plurality of rotor blades having airfoil shank and base portions,

said base portions shaped to interfit with alternate grooves in said wheel to hold and circumferentially space said blades to extend radially from said wheel,

a plurality of battles for preventing the axial flow of gas between adjacent blade shanks,

each bafile comprising a first wall member extending normal to and around a blade at the juncture of said airfoil and shank portions and having an opening t'herethrough fitting the contour of the blade at that point,

a second wall means extending radially between said first wall member and said rotor wheel on the upstream side of said blade,

third wall members extending transverse to said rotor wheel on each side of said blade and attached to said first and second wall means,

said third wal-l members having means for attachment to said rotor wheel comprising a base portion which with the adjacent bafile third wall member interfits with the remaining alternate undercut grooves to lock said baffles to said rotor wheel.

2. A rotor assembly for an axial flow turbomachine comprising the combination of a rotor wheel,

a plurality of rotor blades having airfoil and shank portions,

means to attach said blades to extend radially from said rotor wheel,

said rotor whee-1 having a plurality of grooves spaced between said blades,

a battle for preventing the flow of gas between adjacent blade shanks,

said bafile comprising a first wall member extending normal to and around a blade at the juncture of said airfoil and shank portions and having an opening therethrough fitting the contour of said blade at that point,

a second wall member extending between said first wall member and said rotor wheel on the upstream side of said blade,

third wall members extending transverse to said rotor Wheel on each side and cireumferentially spaced from said blade and attached to said first and second Wall members,

means to support said third wall members in said rotor wheel grooves,

and a locking pin extending axially through said rotor wheel and said second wall means to lock said blades and baifie in place on the rotor wheel.

3. A rotor assembly for an axial flow turbomachine comprising the combination of a rotor wheel,

a plurality of rotor blades having airfoil and shank portions,

means to attach said blades to extend radially from the periphery of said rotor,

said rotor wheel having a plurality of grooves spaced between said blades,

a bafile for preventing the flow of gas between adjacent blade shanks,

said bafiie comprising a first wall member extending normal to and around a blade at the juncture of said airfoil and shank portions and having an opening therethrough fitting the contour of the blade at that point,

a plurality of third wall members extending transverse to said rotor wheel cireumferentially spaced from said blade and attached to said first and second wall members,

means to support said third wall members in said rotor wheel grooves,

and strip means attached to said third wall members which may be machined to the correct thickness to allow adjacent battles to fit closely adjacent one another.

4. A baflle for sealing between adjacent blade shanks of blades supported on a rotor wheel of a turbomachine with said rotor wheel having undercut tgrooves alternating with and cincumferentially spaced from said blade shanks, said baffle comprising,

a first four sided wall member having an opening therethrough fitting the contour of a blade,

additional wall members extending normal and fastened to three sides of said first wall member,

said two additional wall members on opposite sides of said first wall member including means for attachment to said rotor wheel at points circumferentially spaced from said blade shanks,

said means for attachment comprising enlarged base portions shaped to interlock with said rotor wheel grooves,

whereby said first wall means extends around and normal to said blade with said two additional wall members supporting said bafile from said rotor wheel.

References Cited by the Examiner UNITED STATES PATENTS 2,819,870 1/1958 Wayne 253-77 2,853,272 9/1958 Odds 25339.15 2,940,726 6/1960 Dennis 253-77 2,967,043 1/ 1961 Dennis 25377 3,008,689 11/1961 Morley et al. 253-77 MARTIN P. SCHWADRON, Primary Examiner.

SAMUEL FEINBERG, BENJAMIN A. BORCHELT, Examiners. S. W. ENGLE, Assistant Examiner.

Claims

1. A ROTOR ASSEMBLY FOR AN AXIAL FLOW TURBOMACHINE COMPRISING THE COMBINATION OF A ROTOR WHEEL HAVING A PLURALITY OF AXIALLY EXTENDING UNDERCUT GROOVES IN THE PERIPHERAY THEREOF, A PLURALITY OF ROTOR BLADES HAVING AIRFOIL SHANK AND BASE PORTIONS, SAID BASE PORTIONS SHAPED TO INTERFIT WITH ALTERNATE GROOVES IN SAID WHEEL TO HOLD AND CIRCUMFERENTIALLY SPACE AND BLADES TO EXTEND RADIALLY FROM SAID WHEEL, A PLURALITY OF BAFFLES FOR PREVENTING THE AXIAL FLOW OF GAS BETWEEN ADJACENT BLADE SHANKS, EACH BAFFLE COMPRISING A FIRST WALL MEMBER EXTENDING NORMAL TO AND AROUND A BLADE AT THE JUNCTURE OF SAID AIRFOIL AND SHANK PORTIONS AND HAVING AN OPENING THERETHROUGH FITTING THE CONTOUR OF THE BLADE AT THAT POINT, A SECOND WALL MEANS EXTENDING RADIALLY BETWEEN SAID FIRST WALL MEMBER AND SAID ROTOR WHEEL ON THE UPSTREAM SIDE OF SAID BLADE, THIRD WALL MEMBERS EXTENDING TRANSVERSE TO SAID ROTOR WHEEL ON EACH SIDE OF SAID BLADE AND ATTACHED TO SAID FIRST AND SECOND WALL MEANS, SAID THIRD WALL MEMBERS HAVING MEANS FOR ATTACHMENT TO SAID ROTOR WHEEL COMPRISING A BASE PORTION WHICH WITH THE ADJACENT BAFFLE THIRD WALL MEMBER INTERFITS WITH THE REMAINING ALTERNATE UNDERCUT GROOVES TO LOCK SAID BAFFLES TO SAID ROTOR WHEEL.