US2448825A - Turbine rotor - Google Patents

Description

l 1N. Pianos mm. I ,448,825 I mums moron medium 1944 I S-Shuta ShMtI Q HAMLZ AEWF mam NATHAN LI'FRME p 7, 1943- I N. 0. PRICE ETAL f 2,448,825

'TURBINE ROTOR Filed Mar h 20, 1944 v I z Sheets-She'ei; 2

. IN V EN TORS NATHAN 51 5155 25545471117 A.5HEENWALZ7 BY 2 f z.

- AGENT Patented Sept. 1, 194a TURBINE ROTOR Nathan C. Price and Harold A. Greenwald, Hollywood, Calif., minors to Lockheed Aircraft Corporation, Burbank, Calif.

Application March 20, 1944, Serial No. 527,306

v 3 Claims. (01. 253-39) This invention "relates to turbine rotors and particularly to turbine rotors in which a plurality of radial bladesare carried by a rotor of the drum type.

While this invention has manifold applications, it finds its most important application to the precision construction of axial flow combustion gas.

turbines which operate under temperature and speed conditions which are very much more severe than those-heretofore encountered in conventional turbine practice. v

In addition to its application under high temperature conditions, this invention also is particularly applicable to high temperature gas turbine'rotors and to high speed axial compressor rotors for gas turbine power plants which operate at design speeds which are substantially greater than those heretofore conventionally employed.

Turbine or compressor rotors have heretofore generally been constructed of a central drum or spindle member carrying a plurality of radially positioned impeller blades attached to the central drum or spindle by various attachment means. Usually the vanes or impeller blades are attached to the central drum by means of bolts, keys,dovetails, or the like attachments, which even under the relatively mild service conditions to which they were heretofore subjected, often became loosened, lacked rigidity and strength, and were subject to frequent breakage due to the critical vibrational characteristics which such attachment means allowed. Such attachment means heretofore employed also required elab-- orate machining and fitting operations applicable to both the blade and the drum in order to form satisfactory Joints.

It is accordingly an object of this invention to provide an improved turbine rotor particularly well adapted to high speed, high temperature combustion gas service, which will lend itself to simple, methods.

It is a further object of this invention to provide a turbine or compressor rotor which can be run hotter and at higher speeds than any heretofore employed in the elastic fluid turbine art.

It is a still further object of this invention to provide an efficient, simple, and accurate method and apparatus for the fabrication of the before mentioned high speed, high temperature combustion gas turbine rotor.

inexpensive and rapid production such section carrying a row of circumferentially spaced, radially positioned impellerblades, resistance welded to its periphery, forming in effect a homogeneous unitary-rotor body. These and other objects and features of novelty will become evident hereinafter in the description, which, together with the following drawings, illustrate preferred embodiments of the invention.

Figure 1 is a side elevational view of the general assembly of the apparatus of this invention.

Figure 2 is a front elevational view of the apparatus of Figure 1.

Flgure3 is a fragmentary cross-sectional view taken on line 3-3 of Figures 1 and 4.

Figure 4 is a fragmentary longitudinal crosssectional view taken on line 4-1 of Figures 2 and 8.

Figure 5 is a fragmentary sectional elevation taken on line 5-4 of Figure 4. Figure 6 is a fragmentary cross-sectional view of the rotor showing the impeller blade of Figure 4 after attachment to the drum.

The objects of this invention are attained in general by forming a built-up turbine drum having one or more coaxially joined annular sec-- Figure 10 is a cross-sectional view taken on line ill-Ill of Figure 9.

Referring now to the drawings in which like reference numerals refer to corresponding parts throughout the several figures, the apparatus of the invention is as follows:

In Figure 1. I0 is the yoke or frame of an' electric welding press supporting at the top a pneumatic or hydraulic cylinder H. A piston rod l2 extending from the lower end of the cylinder ll makes connection with a crosshead I3, which is reciprocably retained between opposite vertical guides I4 and i 5 formed in the outer portion of the upper arm iii. A ram plate I! is carried on the lower end of the crosshead ii. The ram plate i1 is provided with a pair of dovetails i8 and is by means of which an electrode holder rest 20 is supported thereunder with freedom for lateral adjustment fore and aft with respect to the vertical axis of the piston l2 and crosshead I3. Suitable means such as a setscrew 2i threaded through the side of the ram plate I1 and acting against a wedge plate 22 in contact with one of the dovetail elements I 9 serves adiustably to lock the electrode holder small quantities of strengthening elements such as beryllium or tungsten, of the type widely employed in connection with electric welding apparatus. A heavy flexible conductor lead 28, preferably formed of a plurality of thin copper laminations, serves as an electrical connection between the electrode holder ring 25 and a. stationary connector terminal 21 located in the inner face of the machine frame I and suitably insulated therefrom. The terminal 21 is in turn connected through a suitable electrical conductor 29 with one side of a suitable high amperage source of electrical current such as a transformer or a generator as illustrated at G.

Referring now primarily to Figure 4, 30 is a special electrode, the shank 28 of which is adapted to be plugged into the electrode socket ring 25 and, retained in place in good electrical and fluid-tight contact therewith by means of a plurality of circumferentially spaced flange bolts as shown at 3|. The lower end portion of the electrode 30 opposite the shank 28, is formed with an approximately coaxially located cavity extending inwardly from the lower-end and having a surface contour, as illustrated at 32, which closely conforms with the exterior surface contour of an impeller blade to be retained therein as shown at 33. The lower end of the impeller blade retaining electrode at surrounding the electrode retaining cavity is formed with saddle surfaces as shown at 34 and 35, adapted in operation to be congruous on one side with thecontour' of an integral guide ring 36 and on the opposite side with thesurface contour at 31 of the turbine rotor drum to which the blade is to be welded for accurately determining the position of the electrode 30 and the impeller blade 33 during the welding cycle as hereinafter more. fully described. The shank 28 of the impeller retaining electrode 30 is provided with a bore 39 containing a series of a plurality of Bellville spring elements as shown at 40 adapted to act under compression against a threaded, adjustable plug 4| and a pressure disc 42. The pressure disc 42 normally ,rests, under the force of the spring 40, against an annular shoulder 43 in the electrode 30, but the annular shoulder 43 is located in such an axial position that in order to fully insert an impeller blade such as that shown at 33, the pressure disc must be lifted on of the shoulder and ,forced inwardly a short distance against the force of springs 40. In operation, pressure may thus be brought to bear upon the tip of said impeller blade 83 by means of the pressure disc 42 acting through a suitable insulating pad 44-. An insulating ring 45 is also provided between the innermost Bellville spring element and the inner face of the adjustable screw 4!. The insulating washer 45 and the insulating pad 44, which may be of any suitable materialsuch as mica, fibre, rubber, or plastic, serve primarily to prevent flow of any portion of the heavy welding current through the spring elements 40.

Cooling ducts are provided within the impeller blade retaining electrode 30. The arrangement of the cooling ducts will vary as required by the shapes of the impeller blades to be accommodated. In an electrode as shown at til in Figures 4, and 6, a .pair of semi-circular ducts 4B and 48 are provided within the end portion of the elec- 5 trode on either side of the impeller blade root adjacent the welding area, as best shown in Figure 7. Suitable inlet and outlet passages 41, 48, 49 and 50, leading to these semi-circular cooling ducts are provided extending lengthwise through the electrode walls and communicating with suitable lateral inlet and outlet apertures in the shank, two of which are shown at BI and 52 in Figures 4 and 7. These apertures register with a pair of annular recesses 55 and 56 in the electrode retaining ring 26, and they in turn make connection through ducts 51 and 58 with flexible tubes 59 and 80 which lead to a suitable source of circulating coolant fluid.

A horizontally positioned drum supporting hub 65 is supportedon the inner face of the frame 1! in lateral alignment with the axis of the electrode by means of an integral attachment plate 68. A plurality of bolts 61 which pass through .holes in the margin of the attachment plate It am threaded into the inner face of the supporting frame as-best shown at 68 in Figure 4. The hub 65 is provided with an outer axial shaft portion 1i and an intermediate electrode supporting section 12. The upper surface of the intermedi- 30 ate section 12 of the hub 65 is provided with a flat surface as best. shown at 13 in Figure 8, upon which is fixed an electrode 15 having the form of a circular segment as viewed in cross-section,

such that the adjoining outer surfaces of the hub 12 and of the electrode I5 form a cylinder adapted to fit closely within the inner bore of a turbine rotor drum as hereinafter more fully described. Electrode I5 is preferably made of a material which is a good electrical conductor,

such as copper, or most preferably, tungsten copper or beryllium copper alloy of the type widely employed in connection with electric welding equipment. A heavy electrical conductor 11, preferably formed of a plurality of copper strands, interconnects the intermediate portion of the electrode I5 with a terminal block 18 by way of a centrally located bore 9| extending rearwardly through the hub 65 to the terminal block 16 retained within the frame In. The terminal block 16 is in turn connected through a suitable conductor I9 to the other side of the hercinbefore mentioned suitable source of current G.

The electrode 15 and the hub 65 are provided with longitudinal cooling ducts. The ducts 53 and 54 in the hub are joined at one end by a bend BI and at the opposite ends they make connection with the lateral passages 62 and 83 in the hub which, in turn, lead out of the hub through 50 passages 64 and 69 and thence through the attachment plate 86- through passages 10 and II to external circulating coolant connections, as shown at 88 and 88 in Figure 2.

The inner end of the hub 65 is adapted rotat- 65 ably to support an indexing disc adjacent the attachment plate 68 as shown at 80. The in-- dexing disc .80, which may be of any suitable thickness required properly to locate the turbine rotor drum axially upon the hub BI, is provided 70 with a plurality of equally spaced indexing holes which may be placed either in the exposed marginal portion of the face of the disc or as illustrated herein, located in the periphery. These indexing holes, as shown at II, are spaced so as 7 to subtend angles a, equal to that subtended by the radial axes of the turbine impeller blades as best shown in Figures 3 and 8-. An adjustable detent 8! having a conical end and adapted to enter and center itself within each of the indexing holes 8|, as illustrated in Figure 4, serves to determine and retain the indexing disc 80 at the predetermined increments of angular rotation a as controlled by the spacing of the indexing holes 8I. The indexing pin 82 guided at 88 is adjustable radially by means of threads 84 in bracket 80, which overhangs the periphery of the indexing discv 80 and is rigidly Joined to the upperedge of the attachment plate 88 by suitable means such as gas or electric'welding.

'The outer faceof the indexing disc 80 is provided with a drilled coordinating hole, as shown at 88,into which a coordinating pin 81 is adapted to extend. The coordinating pin 81 may be temporarily attached to the adjacent inner edge of the turbine rotor drum by any suitable means such as welding, or preferably silver. soldering in a furnace, and serves as a means to rotationally couple the said turbine rotor drum in a fixed reference position with respect to the indexing disc 80.

Referring now primarily to Figures 1 and 4, a turbine rotor drum 80 is shown supported upon the hub 80 and bearing upon the electrode I and retained in axial position and in forceful engagement with the indexing disc 80 by means of a helical spring 92 positioned on the outer extending end of the shaft 1| and which acts under compression between the outer end of the turbine rotor drum and a pin 03 positioned through the outer end of the shaft. The shaft II and hub 85 may be of any other desired form best adapted to support the electrode 10 and to fit the inside contour of the bore of the particular type and shape of rotor drum to which blades are to be welded. The corresponding inside shape of the rotor drum bore need not necessarily conform to that which it will have in its finished condition.

Shaft II may be provided with an axial duct 8| leading to a radialpassage 95, which in turn connects with a longitudinal vent groove asshown at 88, formed in the contacting surface of the electrode 10.

The turbine rotor drum of this invention is preferably constructed of a plurality of contiguous, coaxial annular shaped sections of differing average outer diameters, which. for convenience is herein illustrated as having three sections, as shown at I00, IN, and I02 joined together at their inner peripheries by are or gas welding as indicated at I05 and I06 to form a body hav-- ing a smooth, substantially continuous conoidal outer surface which is to constitute the inner flow channel boundary of the turbine expansion zone. The said sections I00, ml, and I02, which may be designated drum sections, are generally I-shaped in radial cross-section, and have an inner hub flange and a radially-outwardly spacedauaess pending upon the length, form, and number of rows of blades desired.

The before mentioned sections, I00, IOI, and III, of the turbine rotor drum are preferably formed with annular ccncavities on opposite faces which, as assembled together adjacent to one another, form annular cavities intermediate the inner and outer peripheries as shown at I01 and I00. The outer opposite flange portions of ad- Jacent rotor drum sections are preferably separated, as shown at I. I0 and III, by narrow annular expansion joints. Unequal expansion between the inner and outer peripheries of the drum is thus provided to eliminate thermal stresses, and a path for circulation of a cooling fluid, such as air, is provided from the inner to the outer surface of the turbine drum, for'examfil:,,by way of suitable ducts such as shown at 0n the outer conoidal suriacejof the drum and preferably symmetrically located with respect to the web of the cross-section of each drum section, insofar as it is possible, annular channels are formed as shown at H8, H4, and III preferably of a width substantially equal to that of the 1mpeller blade root or base to be attached therein. These grooves are preferably formed with a pinrality of circumferential serrations turned in the bottom surfaces thereof, as shown at I28, for the purpose of presenting an initial, reduced area of contact with the inner tapered end of the impeller blade root at the initiation of the welding rings as shown at III, 88, and Ill are also preferably integrally formed on thelower edges of the grooves Iii-I I0, particularly on those which have a considerable slope with respect to the axis of the rotor drum to serve as a means for preventing the tendency of the electrode to slide downward along the surface of the groove while being subject to welding force during the welding cycle. The guide rings 0,18, and I", also serve the more important function of providing a reference surface upon which the saddle ends 84 and 80 of the electrode 80 are adapted to fit and seat during the welding cycle to accurately determine the depth to which the impeller blades are forced into the rotor drum welding groove during the welding cycle. The impeller blade roots are preferably beveled on the underneath surface as shown at I28 in order to presentan initial reduced area of contact with the welding groove serrations and to provide space for molten metal to flow to minimize extrusion thereof which would otherwise occur at the edges, to cause interference with the next adjacent blade to be welded. When the welding of the rows of the impeller blades lnthe welding grooves of the various sections of the rotor drum has been completed, the guide rings H0, 88, and H8 are then partially removed by turning them down in a suitable lathe to a form approximately indicated by the dotted line shown at I20 in Figure 6 to form a step or corner fillet Joining the upper surface of the impeller blade roots with the adjacent surface of the drum.

As stated hereinbefore, the impeller blade-retaining electrode 80 is formed with an end cavity .which accurately conforms with the ,outer surshown at I in Figure 4 iii and seated against the forward face of the 7 blades previously welded in place in the rotor drum welding groove. In cases where the impeller blades are airfoil shaped. as illustrated in Figures 4 to 7 inclusive, the electrode may be substantially cylindrical in shape. as best shown in Figure 7. However, with other types and shapes of impeller blades, for'example with an impulse bucket of the type shown at II! in Figures 9 and 10, the blade retaining end of the elec-- trode ill may have to be formed as there illustrated in order to accommodate this shape of impeller bucket and at the same time provide for necessary clearance with the adjacent previously attached impulse bucket. The shank 20 of the impeller blade retaining electrode may be standardized for all types of blade retaining electrodes in order to be interchangeably adaptable to plug into the electrode retaining ring 3!. In some cases where the impeller blade has considerable twist throughout its length, it may be necessary to construct the retaining electrode split longitudinally to form two halves which may be separated to allow the inserting and withdrawal of the impeller blade.

The impeller blades and buckets may, as illustrated in Figure 9, be provided with cooling passages or vents I20 through their roots which are adapted to register with corresponding passages I2I extending radially through the drum sections. The operation of the apparatus of the invention is as follows: An indexing disc 80 of the required thickness and having peripheral indexing holes iii of the required number and spacing corre sponding with the size and spacing of turbine impeller blades to be welded in place in one of the annular welding channels, for example the one is placed over the hub attachment plate 68. The prefabricated rotor drum comprising the sections IIIO, II, and I02 is next placed upon the hub II and forced into engagement with the face or the indexing disc 80 by means of the spring 92, which in turn is placed in position on the outer-end of the shaft II and retained under the required compression by means of pin 93. Upon installation of the turbine rotor drum as lust mentioned. the coordinating pin 81, previously attached at any suitable arbitrary point on the rim of the rotor, is inserted in place in the indexing hole 88 in the indexing disc 80. disc 80 are next rotated together to a position of registry between the indexing pin 82 and one of the peripheral indexing 'holes II, after which the indexing pin or detent I2 is seated firmly in place in the indexing hole by means-of threads 84. The turbine rotor drum is thus adjusted to and locked in a suitable position in readiness for the initial welding of a turbine impeller blade in the welding groove II as illustrated in Figure 4. An impeller blade which is to be welded in place on the rotor drum is inserted into the lower blade the body of the impeller blade.

The rotor drum and indexing retaining portion 30 of the electrode and lowered tips of the serrations I23 in the welding groove I I4, the impeller blade 33 is forced upward by the resultant reaction into snug engagement with the inner surface 32 of the electrode against the pressure of the accompanying upward movement of The distance I24 under the welding force 8 plate 42 and springs III. The narrow gap initially present between the lower end of the electrode and the upper surface of the impeller blade root shown at I24 is thus closed and the pressure plate 42 displaced inwardly a corresponding distance I24 against the springs 40, as shown in Figure 6, which results in an initial compressive force being applied axially through the impeller blade body. generally does not exceed .008" per inch of blade length, which is greater than the dimensional tolerance in blade manufacture. The electrode pressure in excess of that which is exerted axially through the impeller blade by means of the pressure plate 42 is received by the flange oi the impeller blade root and thus the total welding force applied between the drum and the electrode is divided between the flange and The purpose of thus dividing the welding pressure is to'reduce the maximum stress which must be imposed upon any one portion in the impeller of damaging or collapsing relatively thin, hollow blades is thus reduced, and the flange of the impeller blade is protected from cracking by bending stresses during fusion.

Bufllcient current is next passed through the point of contact between the impeller blade root and-the drum by way of the electrodes in and 18 and the conductors 28, 29 and II. II for fusion of the interface between the bottom I 22 of the impeller blade root and the serrations I22 of the welding groove. As the fusion progresses the electrode 30 carrying the impeller blade ll lowers until the saddle surfaces upon the upper surfaces ring and the rotor drum surface respectively, as shown at I I8 in Figure 6. At this point of time at the end of the welding cycle, the welding currentis cut off, and after 34 and 35 meet and rest 26 and 31 of the guide a brief forging delay period of time during which drum together with the indexing disc is rotated.

location of the next through an angle a to the adjacent indexing hole in the periphery of the indexing disc, and the indexing disc detent 82 again introduced and tightened therein by means of the threads 84 to determine the next position for welding or another impeller blade in place in a position adjacent to the first impeller blade. The steps just described are repeated successively for each impeller blade until all of the impeller blades in a given row are welded in place.

After completion of welding of all of the impeller blades in any given row. the electrode rest 20 may be moved inward or outward parallel to the rotor drum axis into position as indicated by the indexing lines I25 or I27 to an alignment with the next rotor section welding groove, and after installing the proper impeller blade retaining electrode in the holder 26 adapted to retain the type and size of electrodes for welding that particular row. the hereinbefore described welding cycles are repeated for each impeller blade until that row of impeller blades has also been welded in place. J

For each row of impeller blades thus welded in place on the rotor drum. a separate indexing disc all is usually employed which has the required number and spacing-of indexing holes in its-periphery as determined by the number and angu blade. Danger 9 lar spacing of the impeller blades in that particular row. Instead of depending entirely upon ad- Justment f the impeller blade retaining electrode hold r rest "upon the ram plate l1, as hereinbefore mentioned, indexing discs of suitable thickness may be alternatively employed to position the rotor drum axially upon the hub CI in the desired welding positions. Thus a number of indexing discs corresponding. to the number of rows of impeller blades to be welded in place may be employed, each of. diflerent thickness and having a different number ofequally spaced indexing holes in their periphery.

During the welding cycle. a suitable coolan such as water is circulated through the ducts in the electrodes 30 and II by way of the connections 58, and 80, 00 hereinbefore-described.

In the welding cycle an electrode pressure varying generally from approximately 1,200 to 3,000 pounds is employed for impeller blade-root areas of approximately .20 square inch. The maximum current value required under this condi-' tion varies from approximately 50,000 to 60.000 amperes at the peak current portion of the welding cycle.

For example, a typical welding cyclesuitable for the resistance welding of the impeller blades, in accordance with this invention, comprises the steps of flrst applying an initial pro-forging force between the blade root and drum of approximately 1,200 to 1,500 pounds for a period of time corresponding to flve cycles of a sixty-cycle heating current, followed by an increased force, of approximately 2,400 to 8,000 pounds for forging the heated area of the weld during the following remaining one cycle period of heating time, and then holding this' forging force for an additional period of time corresponding to that from the sixth to approximately the sixteenth alternatin! current cycle, afterwhich the pressure isremoved and the weldallowed to cool. The heating current is applied during the five-cycle pre -forging time and continues for approximately one-cycle during application of the initial forging pressure. It has a value, as before stated, of approximately 50,000 to 60,000 amperes. Some 'variation of these welding cycle values may be made by those skilled in the art, without departing from the invention, to suit the particular welding conditions which may vary with size of parts and materials employed.

Advantages accruing from the invention are better stress distribution in the base of the blade and; in the drum to which it is attached, more efficient use of the drum material which results in reduced stresses in the drum or makes it possible to employ a lighter drum, and improved rigidity and freedom from vibration in the blades resulting in freedom from blade failure. The heat conduction from the blade to the drum is higher with the construction of the present invention than with conventional attachment methods, which results in better cooling of the.

ject to severe service conditions, the process and apparatus may be similarly and advanta l'llhe foregoing descriptions and following claims are therefore intended to include and beapplicable to axial flow compressors for elastic fluids,

zherein like advantages accrue from the inven- It is to be understood that the foregoing is not to be limiting butmay include any and all forms of methods and apparatus and articles 'of manufacture whicliare included within the scope of the claims.

We claim:

1. A gas turbine rotor comprising a plurality of separately formed annular sections arranged in coaxial side by side relation, the sections having hubs the internal surfaces of which define a large diameter axial bore in the rotor, the sectime also having rim portions of substantial axial extent and webs of reduced axial extent joining the hubs and rim portions, circular. mating splines on the hubs for maintaining the sections in coaxial relation, welds Joining the hubs of the several sections, said rim portions of the adjacent sections being spacedapart by narrow slots, the

peripheral surfaces of said portions having annular grooves, and rows of blades resistance buttwelded in said grooves. 2. A gas turbine rotor comprising a'plurality of separately formed annular drum sections having radially-spaced hub and rim flanges connected by radially extending webs of reduced axial extentfsaid drum. sections being arranged with their hubs in end-to-end axial alignment so that the internal surfaces of the hub flanges define a central bore which is large in diameter in relation to the radial wall thickness of the assembled -drum sections-and so that the circumferential marginal edges of'adjacent rim flanges are spaced apart to provide narrow, annular expansion slots, said rim flanges forming a flow channel boundary, welds joining the hubs of adjacent drum sections and securing said sections so that said hub and rim flanges are related in the manner described, said rim flanges being formed with annular channels, and blades having their root ends located in said channels and resistance butt welded to said sections.

3. A gas turbine rotor comprising a plurality of separately formed annular drum sections having radially-spaced hub and rim flanges con.- nected by radially extending webs of reduced axial extent, said drum sections being arranged with their hubs in end-to-end axial alignment so that the internal surfaces of the hub flanges define a central bore which is large in diameter in relation to the radial wall thickness of the assembled drum sections and so that the circumferential marginal edges of adjacent rim flanges are spaced apart to provide narrow, annular expansion slots, said rim flanges forming a flow channel boundary, welds joining the hubs of adjacent drum sections and securing said sections so that said hub and aim flanges are related in the manner described, said rim flanges being formed with annular channels, pre-formed circumferentially extending V-shaped serrations formed in the bottom walls of said channels, and

blades having their roots located in said channels and resistance butt welded to the walls thereor to fill said serrations.

NATHAN (1. PRICE. HAROLD A. GREENWALD.

REFEREhlCES CITED The following references are of record in the Ilia of this patent:

UNITED STATES PATENTS Number Number Number 12 Name Date De Femnti July 27, 1915 Noack .2 July 10, 1934 Wade May 4, 1937 Lysholm May 14, 1940 Zellbeck et ai. Sept. 29, 1942 Dahiatrand Apr. 4, 1944 I Meininghaus Aug. 22, 1944 FOREIGN PATENTS Country Date Holland Mar, 18, 1941 Great Britain Feb. 26, 1930 France Jan. 4, 1916 Great Britain Nov. 13, 1939 Great Britain Sept. 20, 1940

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