US3529901A - Turbine motive fluid inlet seal structure - Google Patents

Description

Sept, 22, 1970 J, J.-HART ETAL TURBINE MOTIVE FLUID INLET SEAL STRUCTURE Filed Nov. 18, 1968 3 shets-sheet 1 INVENTORS John J Hurt and WITNESSES Lewis J. Miller BY I J. J. HART ETAL TURBINE MOTIVE FLUID INLET SEAL STRUCTURE Filed Nov. 18, 1968 5 Sheets-Sheet 2 nited States US. Cl. 415-103 11 Claims ABSTRACT OF THE DISCLOSURE A double, opposed axial flow turbine having an outer casing structure and an inner casing structure, the latter formed in at least two sections, and having an inlet conduit structure extending through the outer casing structure and into the inner casing structure, is provided with a flexible seal structure to seal the zone of intermediate pressure between the sections of the inner casing structure from the atmosphere, and to also seal the zone of exhaust (vacuum) pressure between the outer casing structure and the inner casing structure from the atmosphere. The seal structure comprises annular sealing elements connected between the inlet conduit structure and the outer casing structure, on the one hand, and between the conduit structure and one of the sections of the inner casing structure, on the other hand. Guide structures are also provided to maintain the alignment of the inlet conduit structure with the outer casing and with one of the sections of the inner casing. The inlet conduit structure includes only one flanged connection which is placed in the annular space between the outer casing structure and the inner casing structure.

BACKGROUND AND BRIEF SUMMARY OF THE INVENTION Double, opposed axial flow steam turbines having an outer casing structure and an inner casing structure are well known. Where the temperature difference between the steam temperature at the inlet and the steam temperature at the exhaust is large, it has been found that the use of an inner casing structure divided into separate sections reduces the tendency of the inner casing structure to distort. When the inner casing structure is so divided into sections, a flexible seal must be provided between the sections thereof so as to prevent the steam from escaping from between the sections into the exhaust of the turbine.

Further, since the conduit structure must extend through the outer case, a further flexible seal has been required between the conduit structure and the outer casing structure so as to seal the steam between the inner and outer casing structure from escape into the atmosphere.

Thus, heretofore, two separate seal structures have been provided. One seal structure between the inner casing structure and the conduit structure and the other between the outer casing structure and the conduit structure. This has, in turn, required four flanged connections at the conduit structure.

In view of the foregoing, it is an object of this invention to provide a single seal structure in place of the two separate seal structures heretofore required in such turbines.

A further object is to reduce the cost of the required seal structure.

Briefly, this invention is incorporated in a central admission double, opposed flow elastic fluid turbine comprising inner and outer casing structures. The rotor has at least two annular rows of rotatable blades and two atent ice annular rows of stationary nozzle vanes cooperating with the rotating blades to provide two pairs of axial motive fluid expansion stages on opposite sides of a central inlet conduit structure. The inner casing structure comprises a central casing section, and a second inner casing section movable relative to the central inner casing and encompassing the latter to define therebetween a zone of intermediate fluid pressure and temperature. The second inner casing section denfies with the outer casing structure an exhaust pressure Zone. The inlet conduit structure supplies fluid at the inlet pressure and temperature and extends through an opening in the outer casing structure and through an opening in the second inner casing structure. An annular flexible sealing means is provided to seal the fiow of the fluid from said zone of intermediate pressure and from said exhaust pressure zone. The sealing means comprises three annular elements, the first annular element being connected to the inlet conduit structure, the second annular element being connected to the outer case structure, and the third annular element being connected to the second inner casing system.

Thus, one sealing means is provided by this invention to perform the functions of the two separate sealing means heretofore utilized. The sealing means of this invention is more economical, because less welding and fewer machined surfaces need be provided as compared to the previously known sealing structures. Since only one sealing structure is utilized in this invention, the number of flanges in the inlet conduit structure required is reduced to two flanges.

Further, in the preferred embodiment, the inlet con duit structure comprises a crossover pipe and a transition pipe connected together by flanges disposed in the annular space between the outer casing structure and the inner casing structure. The placement of the flanges in this space permits the height of the crossover pipe to be reduced from what it would be otherwise, permitting the ceiling height of the power house to be reduced, if desired.

The foregoing and other objects of this invention will become more apparent from the following detailed description thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE VIEWS FIG. 1 is a longitudinal, partial sectional view, taken in a vertical plane, of a central admission, double opposed flow turbine incorporating this invention, showing a part of the turbine in side elevation;

'FIG. 2 is a partial axial sectional view, on an enlarged scale, of the inlet conduit shown in FIG. 1, showing the flexible seal structure of this invention, the view being generally taken along the line II-II in FIG. 3;

FIG. 3 is a cross-sectional view of the flexible seal structure taken along the line III-III in FIG. 2;

FIG. 4 is a partial axial sectional view of the flexible seal structure, showing only the right hand portion thereof, and on a greatly enlarged scale for better clarity;

FIG. 5 is a partial, top view of the guide structure, showing the legs thereof in part only; and

FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5, showing the guide spacer, the tongue, andthe arms of the guide structure in vertical section.

DESCRIPTION OF THE PREFERRED- EMBODIMENT Referring to the drawings, in FIG. 1 there is shown a central admission, double, opposed axial flow turbine 10 having a first set or plurality of stages 11, on the righthand side, as viewed in FIG. 1, for expanding fluid in one axial direction and a second set or plurality of stages 12, on the left-hand side, for expanding fluid in an opposite axial direction. As well known in the art, each expansion stage comprises an annular row of stationary nozzles or vanes, such as vanes 14, cooperating with and immediately preceding an annular row of rotatable blades, such as the blades 15. The stationary vanes 14 in the first set (or right-hand set) of stages 11 increase in radial length progressively from the first row of stationary vanes 16 to the last row of stationary vanes 17, and, similarly, the rotatable blades in the first set of stages 11 increase in radial length progressively from the first row of rotatable blades 18 to the last row of rotatable blades 19. The second, or left-hand, set of stages 12 are similar to the first, or right-hand, set of stages 11 described above, and, hence, are not further described.

The stationary vanes are retained within an inner tubular casing structure 21, the latter being described hereinafter in further detail, while the rotatable blades are carried by a rotor 22 disposed within the iner casing structure 21 and rotatably supported at its end portions by suitable bearings 25 and 26.

The inner tubular casing structure 21 is formed in two sections, a central or first, inlet inner casing section 23 and a second or exhaust casing section 24.

An inlet conduit structure 27 is provided for conducting hot, pressurized motive fluid to a central, annular chamber or space 28 and, thence, in opposite axial directions through the axially spaced first rows of stationary vanes 16 for expansion in the first and second sets of stages 11 and 12, respectively.

After expansion, the motive fluid is exhausted through opposite annular outlet fairing members 29 and 30 attached to the second inner casing section 24 in any suitable manner.

The entire structure described thus far is enclosed in an outer casing structure 37 comprising a central, tubular outer case 32 disposed in spaced encompassing relation with the inner casing structure 21 and, more specifically, defining an annular space 69 between the tubular case 32 and the second inner casing section 24. Further, a pair of oppositely disposed end portions or hoods 33 and 34 is disposed in communication, and enclosing relation, with the exhaust outlet members 29 and 30, respectively, and having openings 35 and 36 for further directing the expanded motive fluid in a downward direction to a region of lower pressure, such as a lower pressure turbine or a fluid condenser (not shown).

The exhaust hoods 33 and 34 may be provided with centrally disposed annular fairing members 37 and 38 to enhance the flow characteristics of the hoods and to permit the exhausting fluid to flow smoothly and with a minimum of turbulence therethrough into the openings 35 and 36.

Further, as is known, the various stationary components are divided along a horizontal plane (FIG. 1) passing through the center of the rotor 22 to facilitate assembly and servicing. That is, the outer casing 31 is divided into upper and lower casing portions 31a and 31b which are provided with flanges 31c and 31d, respectively, secured together by suitable bolts 49. Similarly, the inner casing 21 is divided into upper and lower casing portions, and the stationary vanes are divided into upper and lower semi-circular half portions.

In accordance with this invention, a simplified flexible seal structure 50 is provided, which structure is connected to inner and outer casing structures 21 and 31, as shown in the drawings, to permit both axial and radial expansion and contraction of the inlet conduit structure 27, the inner casing structure 21, and the outer casing structure 31 relative to each other. The flexible seal structure 50 also permits expansion and contraction of the two sections 23 and 24 of the inner casing structure 21 relative to each other and to the inlet conduit structure 27. The aforesaid expansion and contraction is permitted while providing a pressure seal against the flow of motive fluid out of the intermediate pressure zones 58 and 59 formed between the sixth and seventh stages on the right and left- 4 hand sides, respectively, of the inlet conduit structure 27 and into the annular space 69, the latter being at exhaust pressure, which may be below atmospheric pressure.

Further, the aforesaid expansion and contraction is permitted while also providing a pressure seal against atmospheric pressure entering the annular space 69 when the latter is at below atmospheric pressure.

In the illustrated embodiment, the central or first inner inner casing section 23 supports a diaphragm ring on the right-hand side of the central inlet conduit structure 27 the ring 45 being divided into upper and lower semicircular half-portions and secured to the inner casing halfportions of the iner casing section 23 by rods 46. The diaphragm ring 45 supports the first four rows of stationary vanes, of the stage 11, in the flow path extending to the right, as shown.

Likewise, the central or first inner casing section 23 supports a diaphragm ring 47, on the left-hand side of the central inlet conduit structure 27, the ring 47 being also divided into upper and lower semi-circular half-portions and secured to the inner casing structure 23 by rods 48. The ring 47 supports the first four rows of stationary vanes of the stages 12 in the flow path extending to the left, as shown.

If desired the diaphragm rings 45 and 47 may be integral.

The diaphragm rings 45 and 47 define an opening 51 between the annular space 28 and the inlet conduit structure 27 for placing the latter in communication with the former.

The inlet conduit structure 27 comprises coaxially aligned pipes 40 and 42 in communication with the opening 51 and the annular chamber 28. The pipe 40 may be a crossover pipe connecting the turbine 10 to a region of higher pressure, such as the outlet of a higher pressure turbine, for supplying fluid to the turbine 10. The pipe 42 extends radially inwardly and has its inner portion in the shape of a truncated cone, as shown in FIG. 1, the pipe 42 being suitably secured to a radially outer portion of the central inner casing section 23, such as by being welded thereto, and with its radially inner part in fluid communication with the opening 51. The truncated cone shape of the pipe 42 is provided to form a transition between the larger diameter of the crossover pipe '40 and the smaller width of the opening 51, and, hence the pipe 42 is referred to hereinafter as a transition pipe.

The crossover pipe 40 and the transition pipe 42 have annular flanges 43 and 44, respectively, disposed within the annular space 69 betwen the tubular outer case 32 and the second inner casing section 34. The flanges 43 and 44 may be suitably welded to the crossover pipe 40 and to the transition pipe 42, respectively, and are connected to each by an annular array of suitable bolts 41 extending through suitable holes in the flanges 43 and into suitably threaded holes in the flange 44, FIG. 4.

The central or first inner casing section 23 is formed, in part, by a cylindrical outer shell 66 which has a suitable opening to receive the transition pipe 42, and the shell 66 may be welded to the transition pipe 42 to secure the two to each other.

The second inner casing section 24 is formed, in part, by a cylindrical outer shell 67 concentric with, and encompassing the shell 66. The shell 67 defines a hole 68 through which the transition pipe 42 extends, as shown.

Extending between the inlet conduit structure 27, on the left as shown in FIG. 4, and the outer casing structure 31 and the second inner casing section 24, on the right, is the flexible seal structure of this invention.

The flexible seal structure 50 comprises a (horizontal) ring 52 secured to a cylindrical (vertical) flexible band 54, such as by being welded thereto, as shown in FIG. 4. Preferably the ring 52 is clamped between the flanges 43 and 44, as shown, the ring 52 being flat but having thickened spaced portions providing raised, annular, marginal, spaced surfaces on its opposite sides which are accurately machined to provide a seal (with the opposed accurately machined flat surfaces of the flanges 43 and 44) against the outward flow of the fluid within the pipes 40 and 42. To further seal the joint between the flanges 43 and 44, soft iron gaskets 55 and 56 may be placed above and below the ring 52, as shown in FIG. 4.

Preferably, the band 54 has a central thicker portion and thickened extremity portions connected by thinner intermediate portions for increasing the flexibility of the band 54 while the thicker portions facilitate welding thereto.

The flexible, vertical band 54 is secured at its upper and lower extremities to annular upper and lower, flexible, relatively thin, flat and horizontal rings 60 and 61, respectively, so that in cross-section, a U placed on its side is formed, as seen in FIG. 4. Further, the upper ring 60 is suitably secured, such as by being welded to the band 54, the upper ring 60 having its radially inner peripheral portion partially overlying and abutting the upper annular surface portion of theband 54, as shown in FIG. 4.

Likewise, the lower ring 61 is suitably secured, such as by being welded, to the band 54, the lower ring 61 having its radially inner peripheral portion partially underlying and abutting the lower annular surface portion of the band 54.

The radially outer margins of the upper and lower rings 60 and 61 are suitably secured to upper and lower flanges, 64 and 65, respectively, concentric with and encompassing the rings 60 and 61.

Preferably, the rings 60 and 61 have thickened extremity portions connected by intermediate thinner portions for increasing the flexibility of the rings while the thicker extremity portions facilitate welding of the rings to the band 54, on the left, and the flanges 64 and 65, on the right.

Referring to the outer tubular case 32 of the outer casing structure 31, a suitable central hole 70 is formed therein through which the crossover pipe 40 extends. The hole 70 receives an upper flanage 72 which is suitably secured around its outer, circular peripheral surface to the wall of the tubular case 32 defining the hole 70, such as by being welded thereto, as shown. Since the flange 72 is flat, while the tubular case 32 has a cylindrical curvature, suitable spacer members are welded in the space therebetween, but such members are not shown.

The upper (outer casing) flange 72 has an annular array of holes 73 to receive an annular array of bolts 74 which extend therethrough and into an annular array of holes in the (seal) upper flange 64 to secure the (seal) upper flange 64 to the (outer casing) flange 72, as shown in FIGS. 3 and 4.

Likewise, the lower (seal) flange 65 is secured to the second inner casing section 24 by an annular array of bolts 78 extending through suitable holes 79 in the lower (seal) flange 65 and into suitably threaded holes in an annular flange 80 which is carried on an upstanding projecting cylindrical column 81. The cylindrical column 81 is secured to the outer cylindrical surface of the shell 67 forming part of the second inner casing 24, for example, by being welded thereto.

To maintain the crossover pipe 40 in proper alignment with the outer casing structure 31 while providing for relative expansion and contraction therebetween, four upper guide structures 90 are placed in equi-spaced relation about the crossover pipe 40, as shown in FIGS. 2 and 3.

Likewise, to maintain the transition pipe 42 in proper alignment with the second inner section 24 (of the inner casing 23) while providing for relative expansion and contraction therebetween, four lower guide struc tures 92 are placed in equi-spaced relation about the transition pipe 42, as shown in FIGS. 2 and 3.

The eight guide structures 90 and 92 are similar to each other, and for purposes of brevity only one of the upper guide structures 90 will be described in detail. Referring to FIGS. 5 and 6, an upper guide structure 90 comprises a female element 94 formed by a U-shaped body 96 defining a groove 97 bounded by arms 98, and legs 99, the latter being only partially shown in FIG. 5. The legs 99 extend toward the outer surface of the crossover pipe and may be welded thereto.

The guide structure 90 further comprises a male element 100 having a tongue 102 on one side extending into the groove 97, but the tongue 102 is substantially narrower than the width of the groove 97 to provide two spaces, one on either side of the tongue 102, into which inverted L-shaped spacers 104 and 106 are inserted. As illustrated, the tongue 102 is also shorter than the depth of the groove 97 to provide a suitable clearance. On the side opposite the tongue 102, the male element 100 is provided with legs 108 extending toward, and secured to, the radially inner surface of the flange 72, such as by being welded thereto.

The vertical surfaces of the spacers 104 and 106, as viewed in FIG. 6, are machined so that the spacers 104 and 106 will closely fit within the spaces between the tongue 102 and the arms 98, the machining being done af ter the various elements are assembled, while permitting the tongue 102 to move relative to the spacers 106 when thermal expansion and contraction causes relative movement between the inlet conduit structure 27 and the outer casing structure 31. Preferably, the height (as shown in FIG. 5) of the spacers 104 is such as to provide a clearance between the base of the groove 97 and the base of the L-shaped space formed on either side of the tongue 102.

The spacers 106 are thereafter secured to the arms 98 by drilling suitable aligned holes in the fingers 107 of the spacers 106 and the arms 98 and threading the parts of the holes in the arms 98. Suitable bolts 110 are then inserted into the fingers 107 and arms 98 to secure them together, as shown in FIG. 6.

The (female) legs 112 of the lower guide structures 92 are secured to the transition pipe 42 while the (male) legs 114 are secured to the flange and column 81 by suitable means, such as by being welded thereto, FIG. 4.

It is thus seen that the foregoing arrangement permits the inlet conduit structure 27, the outer casing structure 31, and the inner casing structure 21 to undergo both radial and axial relative movement due to thermal expansion and contraction while preventing the elastic fluid with in the intermediate pressure zones 58 and 59 from flowing into the annular space 69 (which is at a lower pressure and which may be at a vacuum pressure) by the lower half 5412 of the band 54 and the ring 61. Also, the fluid Within the zones 58 and 59 is: prevented from flowing to the atmosphere by the portion 52a (of the ring 52) which extends radially beyond the flanges 43 and 44. Further, the annular space 69 is sealed against atmospheric pressure by the upper half 54a of the band 54 and the ring 60.

When this invention is incorporated in a turbine 10 which is connected to a source of hot motive fluid, such as a higher pressure turbine, not illustrated, the crossover pipe 40 is usually provided with an angled horizontal portion (not shown) extending toward such higher pressure turbine. Since the connection between the crossover pipe 40 and the transition pipe 42 is within the annular space 69 between the outer casing structure 31 and the inner casing structure 21, the distance between the top of he outer casing structure 31 and the horizontal pipe portion need be less than if a similar flanged connection was placed outside of the outer casing structure, as was the previous practice in such turbines. By lowering the height of the horizontal pipe portion it is possible to provide a ceiling in the room of the power plant building (Within which the turbine is located) of lesser height.

In some of the appended claims, three elements are specified in referring to the seal structure 50. While not intending to be limited by the specific parts enumerated, but for clarity and better understanding of the claims, the first element, referred to in the claims, is described herein as the ring 52. The second element is considered as the upper half 54a of the band 54 and the ring 60. The third element is considered as the lower half 54!) of the band 54 and the ring 61.

We claim as our invention:

1. A central admission double, opposed flow elastic fluid turbine comprising inner and outer casing structures,

a rotor having at least two annular rows of rotatable blades,

and two annular rows of stationary nozzle vanes cooperating with said blades to provide two pairs of axial motive fluid expansion stages,

said inner casing structure comprising a central inner casing section, and

a second inner casing section movable relative to said central inner casing section and encompassing the latter to define therebetween a zone of intermediate fluid pressure,

said second inner casing section defining with said outer casing structure an exhaust pressure zone,

an inlet conduit structure for supplying motive fluid between said pairs of axial motive fluid expansion stages,

said inlet conduit structure extending through an opening in said outer casing structure and through an opening in said second inner casing section, and

an annular flexible sealing means connecting said inlet conduit structure to said second inner casing section and to said outer casing structure for sealing said zone of intermediate pressure and said exhaust pressure zone.

2. The structure recited in claim 1 wherein said annular flexible sealing means comprises three annular element,

the first annular element being connected to said inlet conduit structure,

the second annular element being connected to said outer case structure, and

the third annular element being connected to said second inner casing section.

3. The structure recited in claim 2 wherein the second annular element is also connected to the first annular element, and the third annular element is also connected to said first annular element.

4. The structure recited in claim 3 wherein the three annular elements comprising the annular flexible sealing means are integral.

5. The structure recited in claim 2 wherein the second and third annular elements together have the general shape of a U placed on its side when viewed in cross section with the base of the U closest to said inlet conduit structure.

6. The structure recited in claim 2 wherein said inlet conduit structure includes first and second flanges suitably secured to each other,

said first annular element being disposed between said first and second flanges,

a third flange suitably secured to said outer case,

said second annular element being secured to said third flange,

a fourth flange suitably secured to said second inner casing section, and

Q u said third annular element being secured to said fourth flange.

7. The structure recited in claim 6 wherein gaskets are placed above and below said first annular element and between said first and second flanges.

8. The structure recited in claim 6 wherein said first, second and third elements are formed from relatively thin metal plates.

9. The structure recited in claim 6 wherein said first annular element extends radially outwardly of said first and second flanges, and the second and third annular elements are long and flexible relative to the portion of the first annular element which extends radially outwardly of said first and second flanges.

10. The structure recited in claim 1 wherein said inlet conduit structure includes first and second flanges suitably secured to each other,

said inner and outer casing structures defining an annular space therebetween within which are disposed said first and second flanges.

11. A central admission double, opposed flow elastic fluid turbine comprising inner and outer casing structures defining an annular space therebetween,

a rotor having at least two annular rows of rotatable blades,

two annular rows of stationary nozzle vanes cooperating with said blades to provide two pairs of axial motive fluid expansion stages,

said inner casing structure comprising a central inner casing section, a second inner casing section movable relative to said central inner casing and defining therewith a zone of intermediate fluid pressure, an inlet conduit structure for supplying motive fluid between said pairs of axial motive fluid expansion stages, said inlet conduit structure extending through an opening in said outer casing structure and through an opening in said second inner casing structure,

said inlet conduit structure comprising a crossover pipe and a transition pipe,

said crossover pipe being connectable to a source of high pressure fluid,

said transition pipe being connected to said central inner casing section,

said crossover pipe and said transition pipe each having only one flange,

the flanges being connected to each other and disposed in the annular space between said inner and outer casing structures.

References Cited UNITED STATES PATENTS 2,215,997 9/1940 Blowney 415103 2,920,864 l/l960 Reese et al. 4l5-l03 3,408,045 10/1968 Hart 415103 3,043,559 7/1962 Bauer e t al 415138 FOREIGN PATENTS 362,093 7/ 1962 Switzerland.

HENRY F. RADUAZO, Primary Examiner US. Cl. X.R. 4l5136, 138

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