US2992809A - Tandem compound steam turbine - Google Patents

Description

July 18, 1961 B. s. HERBAGE TANDEM COMPOUND STEAM TURBINE 2 Sheets-Sheet 1 Filed May 20, 1960 f/VERATOP art mm A 5 M 4! July 18, 1961 s, RB 2,992,809

TANDEM COMPOUND STEAM TURBINE Filed May 20, 1960 2 Sheets-Sheet 2 hip TUBE/NE I? THEE/NE United States Patent 9 2,992,809 TANDEM COMPOUND STEAM TURBINE Bernard S. Herbage, West Allis, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed May 20, 1960, Ser. No. 30,515 6 Claims. (Cl. 25339) The present invention relates to elastic fluid turbines and in particular to elastic fluid turbines of the tandem compound type.

Modern day requirements for very large capacity steam turbine driven generating units have resulted in large machines being designed both of the tandem compound and cross compound types. Tandem compound machines are provided, for example, with high pressure and low pressure turbine units or high pressure, intermediate pressure and low pressure turbine units. In either case, a tandem compound machine is provided with two or three separate turbines that have a single shaft assembly extending through all units and connected to a generator. A cross compound design provides a high pressure turbine and intermediate pressure turbine on one shaft and connected to one generator with a parallel low pressure turbine connected to a second generator. A crossover connection is provided to conduct steam discharged by the intermediate pressure turbine to the low pressure turbine on the second shaft. Of these two general types of steam turbines, the tandem compound design results in far greater length than does a cross compound design of the same capacity.

In fact, tandem compound turbines have been designed having a total shaft length of almost 100 feet not counting the length of the generator. As might be expected, a shaft of such great length, subjected to high steam temperatures, results in considerable expansion of the shaft. The expansion of such long shafts is sufficient to greatly magnify the usual problems relating to thrust bearing design, maintaining proper yet close clearance between rotors and housings for the rotors, and maintaining the proper position of the parts of all of the shaft seals that are required. Such problems can to a great extent be avoided, of course, by resorting to the cross compound design which provides a machine of much less overall length. However, the cross compound type of machine is considerably more expenisve to build than the tandem compound machine for reasons that include the fact that two generators are required. The added investment required for a cross compound machine can often be justified, especially in northern climates, where relatively cold water is available for cooling condensers. When cold water is available, a cross compound machine having a high pressure and intermediate pressure turbine shaft turning at 3600 rpm. and a low pressure turbine shaft turning at 1800 r.p.m. can be operated to exhaust steam from the low pressure turbine at a vacuum of about /2 inch of mercury. In warmer climates where such cold water is not available, it may not be possible to exhaust steam under a vacuum of better than 1% inches of mercury. The cross compound machine, which can be provided with very large blades turning at 1800 rpm. and a very large exhaust casing to the condenser, can operate sufliciently more efiicient than a single shaft machine turning at 3600 r.p.m., to make the added investment worthwhile, provided the cold water is avail: able to operate to exhaust at such a substantially better vacuum. Where the added cost of cross compound units cannot be justified the turbine builder, if he is to provide large capacity machines, must then face the problems resulting from the increased length of the tandem compound machine.

Among the practices of the prior art before the present 2,992,809 Patented July 18, 1961 invention, was that of providing a thrust bearing on the end of the turbine shaft remote from the generator. Various means have been developed to adjust such a thrust bearing to compensate for the unequal expansion of the turbines, shafts, rotors and the casings. Inherent in any approach is the basic requirement that blades attached to the turbine spindle rotate at very high speed with relatively small clearance between the rotating and stationary parts of the turbine. With the design of new, much longer, tandem compound machines, the length of the shaft is so great and the expansion of it so great that such existing designs of thrust bearings and adjusting mechanisms can no longer be relied upon to perform as required unless greater clearances are provided between rotating and nonrotating parts to compensate for the ability of the thrust bearing mechanism to properly compensate for such expansion.

Accordingly, it is a primary object of the present invention to provide a tandem compound machine with a thrust bearing arrangement that will be efiective to compensate for the expansion of a very long machine and yet permit clearances between rotating and nonrotating parts to be kept to a minimum.

It is also an object of the present invention to provide a tandem compound machine with a thrust hearing assembly arranged to permit intermediate and/or low pressure units to expand and push the casing of a high pressure turbine to maintain approximately constant spacing of said units and simultaneously move the shaft of the machine to maintain the rotors of the turbines sufficiently close to desired positions so that increased clearances are not required.

It is a further object of the present invention to pro vide a tandem compound machine with a thrust bearing assembly arranged to prevent the warping or distortion of the intermediate pressure turbine casing that does take place being transmitted to the thrust bearing assembly and to guard against the possibility of such warping or distortion moving the thrust bearing and moving the rotor relative to the turbine casings into rubbing contact with nonrotating parts.

According to a preferred embodiment of the present invention a thrust bearing assembly is arranged between a first and second unit of a tandem compound steam turbine. The first and second units may be the high pressure and intermediate units respectively of a three unit machine having high intermediate and low pressure turbine units; or the first and second units may be the high and low pressure units, respectively,-of a machine having only those two units. The first unit, since it utilizes the highest pressure steam, must be provided with a stronger cas-- ing than the second unit. Further, this means that more twisting and warping occurs with the second unit casing than occurs with the first unit casing. The thrust hearing assembly maintains the proper axial alignment of the shafts and rotors relative to the casing structures while this warping and twisting due to unequal expansion and contraction takes place. The thrust bearing assembly includes a pair of parts that engage each other, one carried in fixed position on the turbine shaft and the other slidably supported relative to supporting structure. In addition, the first unit casing and at least the adjacent end of the second unit casing are slidably mounted on support structure. A first pair of massive links connect the adjacent ends of the two casings. Thus, warping and twisting due to the expansion and contraction of the second unit casing (this casing being more susceptible to such action) to a degree greater than that which occurs to the first unit will cause this second unit casing, through the first pair of links, to pull or push the first unit casing and move it relative to the supporting structure in an axial direction. In order for the machine to operate with close clearances between rotor and stator parts, the shaft and rotors must be moved to maintain the desired relationship therebetween when casing structure moves in an axial direction. To move the shaft and rotors of the machine, the second part of the thrust bearing (the part slidably supported by the supporting structure) is connected by a second pair of relatively massive links to the first unit casing. Thus, if the second unit casing does push or pull the first unit casing through the first pair of links, then the first unit casing through the second pair of links will pull or push the thrust bearing assembly which in turn moves the shaft. Twisting, warping, expansion or contraction of the second unit casing that does not have enough of an axial component of force to move the first unit casing, will not result in any axial movement of the shaft and rotor. However, if the twisting or warping by expansion or contraction of the second unit casing has a suflicient axial component of force to move the first unit casing, then the first unit casing will move the shaft and rotor. Although expansion and contraction of the turbine shafts will move the turbine casings, this arrange ment is, therefore, discriminating in that expansion and contraction of the casings may or may not move the shafts. Because this arrangement is (1) discriminating as to the nature of the twist or casing warping of the second unit casing that will result in the shaft and rotors being moved, and additionally (2) effective to isolate the thrust bearing assembly from movements of the second unit casing that do not require adjustment of the thrust bearing assembly, the thrust bearing and rotor assembly move only when it is necessary to do so and relatively close clearances can be utilized even when the machine has an unusually long axial length.

The above general description of a preferred embodiment of the invention accomplishes those objects that have been previously specifically set forth. Other objects will, however, appear hereinafter as a description of the invention proceeds. The novel features of the invention and how all of the objects are obtained will appear more fully from this specification and the accompanying drawings showing an embodiment of the invention and forming a part of this application. All of the novel features are intended to be pointed out in the appended claims.

In the drawings:

FIG. 1 shows the general outline and arrangement of a tandem compound steam turbine having a high pres sure turbine unit, an intermediate pressure turbine unit, a low pressure turbine unit and a dynamoelectric machine for converting the mechanical energy of the turbine units into electrical energy;

FIG. 2 is a view taken along planes II-II of FIG. 1 and additionally with a portion of the high pressure turbine casing broken away to more clearly show the arrangement of parts within;

FIG. 3 is a cross sectional view taken on plane III-III of FIG. 2 and FIG. 4 is a fragmentary perspective view in cross section taken on plane IVIV of FIG. 2.

Referring to the drawings, FIG. 1 shows schematically the arrangement and silhouette of units that make up a tandem compound steam turbine. The first unit entered by the steam that drives the machine is a high pressure turbine unit 10. Steam discharged from this first high pressure turbine unit is delivered by means not shown to the second unit 11 which is labeled in FIG. 1 to indicate that this is an intermediate pressure turbine unit. Steam discharged by this second turbine unit 11 is delivered through means not shown to a third unit which is the low pressure turbine unit 12. The silhouette. of the machine shown in FIG. 1 represents the shape and silhouette of shrouds that cover each of the units rather than the shape of the turbine unit. Beneath each of the shrouds 10, 11 and 12, a turbine unit is disposed having a casing and a rotor mounted on a shaft. Connecting flanges join the shafts together to provide a continuous rotor assembly extending through the casings of all units. Referring to FIG. 2, such structure is illustrated wherein the high pressure turbine 10 is shown as having a casing 20. A portion of the casing 20 is broken away in FIG. 2 to show a portion of a rotor 21 and its shaft 22 within the casing 20. The intermediate pressure turbine 11 is similarly constructed and FIG. 2 shows a shaft 23 projecting from the second unit casing 26. Shaft 23 is connected to the shaft 22 of the first unit by a pair of flanges 27, 28 secured together by any suitable means such as plurality of bolts similar to the bolt 29 shown in the portion of couplings that is in part broken away.

The turbine casing 20 of the first unit 10 is of greater strength than the casing 26 within the second unit 11. This is necessarily so since in a tandem compound ma chine the first or high pressure turbine uni-t utilizes the highest pressure steam that is delivered to the machine.

FIGS. 2 and 4 show how the units are supported so that they may move axially, and additionally (especially casing 26) twist and warp due to expansion and contraction without transmitting damaging stresses to foundation structure. FIG. 2 shows that the high pressure turbine casing 20 is provided with projecting flanges 31 and the casing 26 of the intermediate pressure turbine is similarly provided with projecting flanges 32. When the turbine casings are of the horizontal split type as shown in FIG. 2, the flanges 31, 32 may be made integral with either the upper or lower halves of the turbine casing. As shown in FIG. 2, the flanges are an integral part of the lower half of the turbine casings. The manner in which the flanges 31, 32 provide for the support of the turbine uni-ts relative to the supporting structure 30 may be understood with further reference to FIG. 4. As shown in FIG. 4, a bearing plate 33 is fitted in the flange 32. A part 34 that has the shape of one-half of a sphere is positioned with its convex surface 35 fitted into a block 36 having a cooperating cavity 35a. The plate 33 tests on top of a flat surface 37' of the part 34 to support flange 32 of the machine. With a similar flange 31 On the opposite side of the shaft 23 similarly supporting the opposite side of turbine casing 26 it can be seen that the expansion or contraction causing a casing to move axially will cause the bearing plates 33 and the paths 34 to slide relative to each other. Furthermore, distortion of the turbine casing resulting in twisting of the casing will move the flange 32 so that the convex surface 35 rolls within the concave surface 35a of the part 34.

Referring once again to FIG. 2, connecting means are provided that include a first pair of massive links 38 that connect the adjacent ends of casings 20 and 26. The ends of each of the links 38 are connected to flanges 31, 32 projecting from casings 20, 26, respectively, by any suitable means such as tapered pins or bolts as at 39.

With still further reference to FIG. 2, a pedestal 4a is shown arranged between the first unit, the high pressure casing 20 and the second unit, the intermediate pressure casing 26. A pair of journal bearings 41, 42 are mounted in axially spaced and fixed positions in the pedestal 49. Each of the journal bearings 41, 42 encircle the shafts 22, 23, respectively, to support the entire shaft and rotor assembly within their respective casings.

A thrust bearing assembly 50 is provided within the pedestal 40 and is located between the journal bearings 41, 42. The thrust bearing comprises a pair of engaging parts 51, 52. Both of the parts 51 and 52 are annular collar means. The collar 51 is fixed to the shaft portion 22 of the spindle assembly and the second collar means 52 is slidably supported by the pedestal 4t) in a manner that will be described. The collar means 51 is in the form of an annular disk whereas the second collar 52 is formed as a yoke to engage oppositely facing portions of the collar 51. In essence then the collar 51 projects be tween a pair of collars 52a and 52b. This arrangement as shown in FIG. 2 is, of course, merely one of choice.

It would be just as suitable to provide the reverse arrangement with a yokelike collar means on the shaft with two collars projecting radially outward to engage either side of a single collar slidably supported by the pedestal. The collar means 52 may for ease of assembly be split along a horizontal plane as shown in FIG. 3 to provide an upper half 53 and a lower half 54. Further, as shown in FIG. 3, the lower half 54 of the collar means 52 is carried by a pair of supports 55, 56 that extend parallel to the axis of the shaft 22 and as shown in FIG. 2 extend between vertical surfaces.

A second link means connects the first unit casing 20 to the second collar 52 of the thrust bearing assembly 50. The second link means comprises a pair of links 57, 58 which are connected to the casing 20 by any suitable means, such as bolts at 59, 60. The ends of each of the links 57, 58 remote from the bolts 59, 60 are connected to the collar 52 by means that will move and be moved by the thrust bearing 50 when casing 20 moves or the shafts expand. Further, these connecting means are adjustable to move the collar 52 relatively and axially toward or away from the casing 20. Movement of collar 52 in an axial direction because of either (1) movement of casing 20 that pushed or pulled on links 57, 58 and collar 52; or (2) an adjustment of the connection between links 57, 58 and collar 52 will result in the collar 52 moving the collar 51 and the connected shafts and rotors of the machine.

To provide an adjustable connection between the links 57', -8 and the collar 52, each of the links is provided with a vertical wall member 61 as shown in FIG. 2. The vertical wall member 61 is joined to a similar vertical wall member 62 shown in FIG. 2 by connecting portions shown in FIG. 3. FIG. 3 shows connecting portions 63, 64 that span the top and bottom respectively of the space between the two walls 61, 62 shown in FIG. 2. Thus, the portion 63 shown in FIG. 3 provides a roof over the two vertical walls 61, 62 shown in FIG. 2 and a portion 64 shown in FIG. 3 provides a floor beneath the two wall sections 61, 62 of FIG. 2. A yoke 65 is secured to the collar 52 and projects into the space defined by walls 61, 62, floor portion 64 and roof portion 63. As shown, the yoke 65 has a pair of arms 66, 67 connected together by a back portion 68. The back portion 68 is sandwiched between projections 70 and 71 that extend from the top and bottom halves, respectively, of the collar 52 as shown in FIG. 3. Bolts as shown at 72 may be used to secure the upper and lower halves 53, 54, respectively, of the collar 52 together with the back portion 68 of the yoke 65 pinched therebetween. A thrust block 73 is fitted in the space between the arms 66, 67 as shown in FIG. 2 and between the floor portion 64 and roof portion 63 as shown in FIG. 3. The thrust block 73 is bored to receive a vertical sleeve 74. The sleeve 74 is in turn eccentrically bored to receive a shaft 75. The shaft 75 is keyed to the sleeve 74. Since a similar arrangement is provided on both sides of the collar 52 a pair of shafts 75 therefore projects upwardly as shown in FIG. 3 through the roof portions 63.

The shafts 75 are adapted to be rotated simultaneously by levers 76 which are mounted on the shafts 75 and restrained from rotation relative to the shafts 75 by keys 77. The levers 76 are movable in a plane perpendicular to the longitudinal axis of the shafts 75 by a lever actuating mechanism 78 which slidably engages slots 79 in the end portions of levers 76. Movement of the levers 76 will cause the shafts 75 and the eccentrics 74 to rotate and the rotation of the eccentrics 74 in the thrust blocks 73 will move theyoke 65 and the yoke collar 52 longitudinally relative to the turbine casing 20, thereby adjusting the relative positions of the turbine casing 20 and rotor 21 and making similar adjustments of the rotors of subsequent units their respective casings.

To actuate the adjusting mechanism the levers 76 must, as previously stated, he moved to rotate shafts 75. As

6 here shown, this motion of the levers 76 is achieved by an arrangement in which the ends of levers 76 are slotted at 79 to receive trunnions 83 extending from opposite sides of a rectangular block 84. Block 84 has a threaded opening 85 extending through it parallel to the turbine shaft 22. Through this opening 85 is disposed a threaded rod 86, the threads of which cooperate with the threads of the threaded opening 85 and the ends of which may be journaled in any rigid supporting structure (not here shown) as might be desired in order to hold the nod 86 in a fixed position as it turns so that the movement or turning of rod 86 is imparted to the levers 76. Means may be provided as desired to permit the turning of shaft 86 from a convenient location. That is a means, not shown, such as a worm gear and worm connecting shaft 86 to a shaft 87 and wheel 88 as shown in FIG. 1 would provide a convenient way to move the levers 76 and achieve the desired adjustment.

In the operation of a tandem compound steam turbine embodying the preferred embodiment of the invention as shown in the drawings, the steam, that is admitted to the intermediate pressure turbine casing 26 after it has passed through the high pressure turbine casing 20, will be of lower pressure than when this steam was first admitted to the high pressure turbine. The high pressure turbine casing 20 must therefore be heavier and stronger than the casing 26 need be because the steam within casing 20 is of higher pressure and temperature than the steam within casing 26. Such characteristics of a tandem compound steam turbine result in the intermediate pres sure turbine casing 26 being more affected by expansion and contraction than is the high pressure turbine casing 20. The expansion and contraction of casing 26 will manifest itself both in twisting and warping of the casing itself and in changes in the axial length of the casing. Twisting and warping movements in the casing 26 are accommodated by supports of the type shown in FIG. 4 wherein much motion results in the fiange member '32 turning the convex surface 35 of the member 34 within the concave surface 35a of block 36. Expansion and contraction of the intermediate pressure turbine casing 26 that results in a change in the axial length of the casing is accommodate as shown in FIG. 4 in that the plate 33 is permitted to slide upon the surface 37 of part 34. Thus, any change in the thermal conditions imposed upon the machine that results in an increase in the axial length of the casing 26 will provide axial component force greater than any opposing force from the heavier casing 20 that is less affected by thermal changes, and the result is that the casing 26 will push the links 33 and casing 20, moving the casing 26 along its support plates 37. Expansion of the casing 26, therefore, that results in the casing 26 pushing the shorter casing 26, will also result in the casing 20 pulling the links 57, 58. When these links 57, 58 move they will also move their vertical walls 61, 62, the floor portions 64, the roof portions 63 and the shafts 75 journaled in the roof portions 63. The movement of the shafts 75 in a direction parallel to the axis of the turbine shaft 22 will move the eccentric sleeve 74 and the thrust block 73 along with the links. Since the yoke is fitted about the thrust block 73, it will also move with the links 57, 58. Further, the yoke 65 is connected to the collar 52 that engages the collar 51 on the turbine shaft 22. Thus, when the links 38 push the turbine casing 20, the links 57, 58 pull the shafts which in turn pull sleeve 74, thrust block 73, yoke 65, collar 52, collar 51 and thereby moves the turbine shafts 22, 23 and their connected rotors in an axial direction.

A decrease in thermal energy delivered to the intermediate pressure turbine casing 26 will result in the casing 26 contracting in its axial length and twisting and warping with an axial component of force to a degree greater than that which occurs with respect to casing 20. Thus, under these circumstances the casing 26 will pull on the 7 links 38 and pull the casing 20. This motion will result in the links 57, 58 pushing the thrust bearing assembly 50 and again moving the shafts 22, 23 and their rotors to a position appropriate to maintaining close clearances in the casings 20 and 26.

Expansion and contraction of the shafts 22, 23 will, of course, also move thrust bearing assembly 50; links 57, 58; casings 20; links 38; and casing 26.

Further, the relative position of the shafts 22, 23 and rotors can be manually adjusted relative to the casings 2d and 26 by turning the hand wheel 88 shown in FIG. l. The turning of hand wheel 88 which is mounted on shaft 87 turns the shaft 87 and through a worm connection not shown turns the rod 86. Rotation of the rod 86 moves the block 84 along an axis parallel to shaft 22. The movement of block 84 carries the trunnion S3 in an axial direction and as a result of the slotted connection between trunnions 83 and levers 76 the levers 76 are turned about the central axis of the shafts 75. The shafts 75 which are keyed to both the levers 7 6 and to the eccentric sleeve 74 transmits the turning movement from levers 76 to eccentric sleeves 74. The turning of eccentric sleeves 74% moves thrust block 73 and yoke 65. This movement of the yokes 65 is also transmitted, of course, to the collars 52, 51 and the shafts 22, 23 to move the shafts and their connected rotors Within the casings 20 and 26.

From the foregoing it will be apparent to those skilled in this art that an arrangement is provided for moving casings along shafts and turbine shafts and connected rotors within casing structures, that accomplishes the objects of this invention. That is, a change in shaft length Will move the thrust bearings and casings while only expansion or contraction of the second unit casing 26 that has as axial component of force sufficient to exceed any similar but opposite component of force due to expansion or contraction of casing 20 will result in such force being applied to move the thrust bearing 50 and shafts 22, 23 and their connected rotors. Any expansion or contraction of easing 2.6 that has axial components of force insufficient to move casing 20 will not be applied to the thrust bearing assembly and turbine shaft. Further, any twisting or warping of casing 26 that does not have an axial component of force great enough to move casing 20 will be isolated from the thrust bearing assembly. It will also be obvious to those skilled in the art that the invention is not entirely limited to the preferred form described and shown in the drawings but is susceptible of various changes and modifications without departing from the spirit of the invention. Accordingly, the disclosure herein is illustrative only and the invention is not limited thereto.

What is claimed is:

1. A tandem compound rotary machine comprising: at least a first and a second rotary machine unit, said units each having a casing and a rotor disposed therein with said rotors constructed to provide a continuous rotor assembly extending through both of said casings, and said first unit being more resistant to physical change due to temperature and pressure change than said second unit; structure for supporting the machine; a thrust bearing assembly comprising a pair of engaging annular collar means, a first of said pair of collar means being supported in fixed position on said rotor assembly and a second of said collar means being slidably supported by said supporting structure, said first unit casing and at least the adjacent end of said second unit casing being slidably mounted on said structure; first means connecting said first unit casing to said second unit casing; and second means connecting said first unit casing to said second collar means so that expansion and contraction of said second unit casing that moves said first unit casing will also move said second collar means and said rotor assembly relative to said supporting structure.

2. A tandem compound rotary machine comprising: at least a first and a second rotary machine unit, said units each having a casing and a rotor disposed therein with said rotors constructed to provide a continuous rotor assembly extending through both of said casings, and said first unit being more resistant to physical change due to temperature and pressure change than said second unit; structure for supporting the machine; a thrust bearing assembly comprising a pair of engaging annular collar means, a first of said pair of collar means being supported in fixed position on said rotor assembly and a second of said collar means being slidably supported by said supporting structure, said first unit casing and at least the adjacent end of said second unit casing being slidably mounted on said structure; first means connecting said first unit casing to said second unit; second means connecting said first unit casing to said second collar means so that expansion and contraction of said second unit casing that moves said first unit casing will also move said second collar means and said rotor assembly relative to said supporting structure; and said second means including means for adjusting said second collar and said rotor assembly regardless of the movement of the casings of said machine.

3. A tandem compound rotary machine comprising: at least a first and a second rotary machine unit, said units each having a casing and a rotor disposed therein with said rotors constructed to provide a continuous rotor assembly extending through both of said casings, and said first unit being more resistant to physical change due to temperature and pressure change than said second unit; structure for supporting the machine; a pedestal mounted in a fixed position on said structure between said first and second units; a pair of journal bearings mounted in axial spaced and fixed positions in said pedestal, said journal bearings encircling said rotor assembly to support same relative to said pedestal and said structure; a thrust bearing assembly between said journal bearings comprising a pair of engaging annular collar means, a first of said pair of collar means being in fixed position on said rotor assembly and a second of said collar means being slidably supported by said pedestal, said first unit casing and at least the adjacent end of said second unit casing being slidably mounted on said structure; link means between said first and second units connecting said adjacent ends of said casings; and second link means connecting one of said first and second unit casings to said second collar means so that expansion and contraction of said second unit casing that moves said first link means and said first unit casing will also cause said second link means to move said second collar means relative to said pedestal and thereby move said rotor assembly relative to said journal bearings and said pedestal and said supporting structure.

4. A tandem compound rotary machine comprising: at least a first and a second rotary machine unit, said units each having a casing and a rotary disposed therein with said rotors constructed to provide a continuous rotor assembly extending through both of said casings, and said first unit being more resistant to physical change due to temperature and pressure change than said second unit; structure for supporting the machine; a pedestal mounted in a fixed position on said structure between said first and second units; a pair of journal bearings mounted in axial spaced and fixed positions in said pedestal, said journal bearings encircling said rotor assembly to support same relative to said pedestal and structure; a thrust bearing assembly between said journal bearings comprising a pair of engaging annular collar means, a first of said pair of collar means being in fixed position on said rotor assembly and a second of said collar means being slidably supported by said pedestal, said first unit casing and at least the adjacent end of said second unit casing being slidably mounted on said structure; first link means between said first and second units connecting said adjacent ends of said casings; second link means connecting one of said unit casings to said second collar means so that expansion and contraction of said second unit casing that moves said first link means and said first unit casing Will also cause said second link means to move said second collar means relative to said pedestal and thereby move said rotor assembly relative to said journal bearings and said pedestal and said supporting structure; and said second link means including means for adjusting the connection between said second collar means and said first and second unit casings to move said second collar and said rotor assembly regardless of the movement of the casings of said machine.

5. A tandem compound rotary machine comprising: at least a first and a second rotary machine unit, said units each having a casing and a rotor disposed therein with said rotors constructed to provide a continuous rotor assembly extending through both of said casings, and said first unit being more resistant to physical change due to temperature and pressure change than said second unit; structure for supporting the machine; a thrust bearing assembly comprising a pair of engaging annular collar means, a first of said pair of collar means being supported in fixed position on said rotor assembly and a second of said collar means being slidably supported by said supporting structure, said first unit casing and at least the adjacent end of said second unit casing being slidably mounted on said structure; a first connecting means connecting said first unit casing and said second unit casing; and a second connecting means connecting said first unit casing and said second collar means so that expansion and contraction of said second unit casing that moves said first connecting means and said first unit casing will also cause said second connecting means to move said second collar means and said rotor assembly relative to said supporting structure.

6. A tandem compound rotary machine comprising: at least a first and a second rotary machine unit, said units each having a casing and a rotor disposed therein With said rotors constructed to provide a continuous rotor assembly extending through both of said casings, and said first unit being more resistant to physical change due to temperature and pressure change than said second unit; structure for supporting the machine; a pedestal mounted in a fixed position on said structure between said first and second units; a pair of journal bearings mounted in axial spaced and fixed positions in said pedestal, said journal bearings encircling said rotor assembly to support same relative to said pedestal and said structure; a thrust bearing assembly between said journal bearings comprising a pair of engaging annular collar means, a first of said pair of collar means being in fixed position on said rotor assembly and a second of said collar means being slidably supported by said pedestal, said first unit casing and at least the adjacent end of said second unit casing being slidably mounted on said structure; a first link means between said first and second units connecting said adjacent ends of said casings; and a second link means connecting said first unit casing and. said second collar means so that expansion and contraction of said second unit casing that moves said first link means and said first unit casing will also cause said second link means to move said second collar means relative to said pedestal and thereby move said rotor assembly relative to said journal bearings and said pedestal and said supporting structure; and said second link means including means for adjusting the connection between said second collar means and said first unit casing to move said second collar and said rotor assembly regardless of the movement of the casings of said machine.

No references cited.

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