US3206166A

US3206166A - Elastic fluid apparatus

Info

Publication number: US3206166A
Application number: US339294A
Authority: US
Inventors: Frank A Beldecos; Gordon B Leyland
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1964-01-21
Filing date: 1964-01-21
Publication date: 1965-09-14
Anticipated expiration: 1982-09-14

Description

Se t. 14, 1965 F. A. BELDECOS ETAL 3,206,166

ELASTIC FLUID APPARATUS Filed Jan. 21, 1964 3 Sheets-Sheet 1 Fig. l.

WITNESSESI F k A lgvlgNToRs d run e ecos on @W- R Gordon B. Leylond.

p 1965 F. A. BELDECOS ETAL 3,206,165

ELASTIC FLUID APPARATUS Filed Jan. 21, 1964 5 Sheets-Sheet 3 United States Patent 3,206,166 ELASTIQ FLUID APPARATUS Frank A. Beldecos and Gordon B. Leyland, Media, Pa, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pin, a corporation of Pennsylvania Filed Jan. 21, 1964, Ser. No. 33?,294 7 Claims. (Cl. 253-391) This invention relates to elastic fluid utilizing machines, more particularly to turbines motivated by hot elastic fluid, and has for an object to provide improved apparatus of this type.

Elastic fluid utilizing machines, such as turbines, now employ motive elastic fluid at such high temperature values, for thermodynamic efiiciency considerations, that some cooling is desirable for the hot and highly stressed running components, such as the rotor structure and rotor blades, to permit reliable operation at such high values.

In view of the above, many schemes have heretofore been proposed for cooling the above hot running components by employment of coolant fluids (both liquid and gaseous).

One of the most recent and effective arrangements is that described and claimed in Beldecos and Brown patent application No. 276,439, filed April 29, 1963 and assigned to the same assignee as the present invention. In accordance with the Beldecos and Brown arrangement, an axial flow steam turbine is provided in which the first expansion stage comprises an annular row of rotor blades carried by a disc portion of the rotor structure and cooperatively associated with a stationary varied nozzle structure. Blade sealing means is provided between the disc and the nozzle structure for minimizing leakage of motive steam from the main motive fluid path before expansion. Since leakage past the sealing means connot be entirely prevented and since this blade leakage steam is hot, its effect is to overheat the rotor structure including the disc portion and the blade roots.

To overcome the above overheating effect, the rotor disc is provided with an annular array of holes for pumping a portion of the steam, expanded (and thus cooled) in the first expansion stage, through the disc into the space between the nozzle structure and the rotor disc, with a sufficient rise in pressure to substantially oppose the hotter blade seal leakage. A plurality of small apertures are also provided adjacent the blade roots and extending through the disc, and these apertures are effective to direct a portion of the blade leakage and pumped steam mixture back to the downstream side of the disc portion, thereby maintaining a recirculatory flow of cooling steam through the disc.

The remainder of the above mixture is directed along the rotor and past a series of labyrinth seals to minimize overheating of the rotor and is then directed to a subsequent and lower pressure expansion stage for further expansion.

Although the above arrangement is a very desirable improvement in the art and has a notable cooling efiect on the rotating components of the turbine, some of the high temperature blade leakage is unavoidably mixed with the cooler (partially expanded) steam, thereby raising the temperature of the mixture that is directed along the rotor to the subsequent stage.

In view of the above, it is a primary object to provide an improvement in the above described Beldecos and Brown arrangement. I

A further and more specific object is to provide an arrangement that substantially minimizes the mixing of the hot blade leakage fluid with the pumped and cooler expanded fluid, thereby to enhance the cooling effect of the pumped fluid on the highly stressed rotor portions.

Yet another object is to provide a separate path for the hot blade leakage fluid that is out of direct heat exchange with the highly stressed rotor portions.

Briefly, in accordance with the invention, the above described Beldecos and Brown arrangement is modified to provide a second sealing means between the rotor disc and the associated nozzle structure, which second sealing means together with the first mentioned sealing means jointly defines a sealing space for the blade leakage steam. Also, a plurality of passages are provided in stationary structure, such as the nozzle structure, to bleed off the collecting leakage fluid in a manner to minimize heat exchange with the adjacent rotor portion.

The pumped fluid is directed to a portion of the disc in direct communication with the clearance space between the stationary portions and the rotor and in restricted communication with the sealing space. Accordingly, the second sealing means imposes a pressure drop adequate to prevent mixing of the two fluid flows and assure that substantially all of the cooler or pumped fluid flows through the clearance space with attendant enhanced cooling of the adjacent rotor portion.

The above and the other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

FIGURE 1 is a longitudinal view, taken along line II of FIG. 3, of a turbine incorporating the invention, the upper half being in section to show the internal arrangement;

FIG. 2 is an enlarged fragmentary sectional view showing in detail a part of the structure shown in FIGURE 1;

FIG. 3 is a left hand end view, on a smaller scale, of the turbine shown in FIG. 1;

FIG. 4 is a fragmentary view taken along line IV-IV of FIG. 2; and

FIG. 5 is a fragmentary sectional view taken along line VV of FIG. 2.

Referring to the drawings in detail, in FIG. 1 there is shown an axial flow elastic fluid turbine generally designated of the dual unit type, having a first motive fluid expansion section generally designated 12 and a second motive fluid expansion section generally designated 14 disposed within a unitary shell structure 15, and having an axially elongated rotor structure 16 disposed within the shell structure and supported therein for rotation by suitable bearings 17. The shell structure 15 includes an outer casing 18 and an inner casing structure 19 disposed within the outer casing 18 and spaced internally therefrom in a circumferential manner. The internal casing structure 19 further includes partition wall structure 20 acting to restrict flow of motive fluid from one of the expansion sections to the other during operation.

The first expansion section 12 includes a first portion 21 of the rotor 16 provided with a first expansion stage 22 disposed in axially spaced and opposed relation with a plurality of subsequent expansion stages 23. Expressed another way, the first expansion stage 22 is disposed in backto-back series flow relation with the second on the subsequent expansion stages 23. The expansion stages 23, as well known in the art, comprise stationary nozzle vanes 24 arranged in annular rows and supported in the inner casing structure 19, and cooperating rows of rotor blades 25 attached to the rotor portion 21 and rotatable therewith.

The first expansion stage 22, usually referred to as the control stage or governing stage, as more clearly shown in FIG. 2, employs a disc portion 27 provided in the rotor portion 21 and having an annular row of rotor blades 28 circumferentially disposed thereon. The rotor blades 28 are disposed immediately downstream of a stationary nozzle structure 29 having an annular array of nozzle vanes 30 cooperatively associated with the rotor blades 28 for directing the hot motive fluid thereto. The nozzle structure 29 further includes an annular nozzle chamber structure 31 for directing the motive fluid to the nozzle vanes 30. A plurality of suitable conduit structures 32 extending through the outer casing structure 18 and the inner casing structure 19 (FIG. 1) are employed for directing the hot motive fluid to the nozzle chamber structure 31, as well known in the art.

As well known in the art, the control stage blades 28 are usually of the impulse type and extract considerable energy from the motivating fluid, so that a substantial pressure drop occurs across this stage, with concomitant reduction in temperature.

The nozzle chamber structure 31, is preferably divided into a plurality of arcuate segments disposed in an annular array (not shown) jointly defining a circular radially innermost surface and disposed in closely spaced encompassing relation with the rotor, thereby providing an annular leakage space S. As best shown in FIGS. 2 and 5, each segment is provided by a nozzle box 33 defining an arcuate nozzle chamber 34 and having a tubular inlet 35 extending radially outwardly therefrom and connected to an associated conduit 32.

After partial expansion in the first stage 22, the motive fluid flows, as indicated by the arrows A in FIGS. 1 and 2, radially outwardly, and then reverses in direction and flows around the nozzle box inlets 35 to the subsequent stages 23 of section 12.

After expansion in the first expansion section 12, the fluid, as indicated by arrows B, is directed to an exhaust annulus 37, and from the exhaust annulus it is directed through the outer casing 18 by a tubular exhaust conduit 38.

The nozzle structure 29 further includes a nozzle ring carrying the vanes 30 and having an annular portion 411 encompassing the rotor blades 28.

The rotor blades 28 may be of any suitable structural type, for example of the well known side-entry r-oot type (not shown) for retention in the disc 27.

The blades 28 are connected to each other at their outermost ends or tips by annular shroud structure 44 disposed in radially inwardly spaced relation with the nozzle ring portion 41 and, to minimize the leakage of hot motive fluid therepast during operation, a plurality of stationary annular seal strips 46 are employed. These strips may be of any suitable type and extend radially inwardly into spaced relation with the shroud 44 to permit free rotation of the shroud while restricting flow of the motive fluid therepast.

The nozzle ring 40 is provided with a pair of annular radially inwardly extending seal strips 48 disposed in closely spaced relation with a peripheral shoulder 50 formed on the rotor disc 27 to jointly therewith provide a blade seal to minimize leakage, in radially inward direction along the upstream face 51 of the disc 27, of hot motive fluid before expansion in the rotor blades 28.

Between the first expansion stage 22 and the subsequent expansion stages 23, there is provided a space 52 for distribution of the motive fluid after expansion in the first stage. This space 52 is partly defined at its inner periphery by the downstream face 53 of the rotor disc 27 and the nozzle structure 29 and at its outer periphery by the partition 20 and a portion of the inner casing 19. The rotor disc 27 is provided with an annular row of openings or apertures 54 (only one shown), concentric with the axis of the rot-or. These openings may be bores or the like, and extend through the disc to provide communication between the distribution space 52 and the leakage space S. The openings 54 are effective to pump expanded motive fluid from the distribution chamber 52 through the disc 27 to the leakage space S, during operation. Accordingly, the openings are formed and arranged to provide a pumping action to occur during operation. As illustrated, the openings 54 are inclined with the rotational axis of the rotor 16 at an angle on the order of about 15.

The angle of inclination, size and number of the openings may be modified, as desired, to permit a larger or a smaller pumping action to occur during operation.

The second expansion section 14, is provided with a plurality of motive fluid expansion stages 55 which include annular rows of rotor blades 56 peripherally mounted on the rotor portion 57 and stationary nozzle structures provided with annular rows of nozzle vanes 59 cooperatively associated with the rotor blades 56, as well known in the art. Hot motive fluid is directed, as indicated by arrows C, to the second expansion section 14 through a plurality of tubular conduit structures 60 extending through the outer casing 18 and the inner casing 19 into an annular nozzle chamber 61 and is thence directed through the expansion stages 55 to provide a motive eifect upon the rotor 16. After expansion in the second expansion section 14, the fluid (arrows C) is directed to an annular exhaust passage 62 formed by the outer and inner casings and, from the exhaust passage 62, it is directed through the outer casing 18 by a tubular exhaust conduit 63.

Although the two

expansion sections

12 and 14 are isolated from each other by the internal wall structure 26, a plurality of labyrinth rotor seal structures 69 are provided therein to minimize or restrict .the leakage of motive fluid from the expansion section 12 to the expansion section 14, while permitting freedom of rotation of the rotor during operation. These labyrinth seals 69 may be of any suitable type and, as illustrated in FIG. 2, include a plurality of closely spaced rows of circular segments 79 disposed in the wall structure 2% and cooperatively associated with groups of circular serrations 72 provided in the rotor 16. Accordingly, as well known in the art, leakage flow of motive fluid past the labyrinth seals is restricted to a relatively small order.

In accordance with this invention, the nozzle structure 29 is provided with an annular array of passages 75 extending through the nozzle box segments 33 and the nozzle ring 40. In addition, a second seal structure 76 is interposed between the downstream face of the nozzle ring 40 and the upstream face 51 of the rotor disc 27 to provide a restriction to leakage fluid, as illustrated by arrows E, which fluid would otherwise flow into the leakage space S. The seal structure 48, '76 and the juxtaposed downstream and upstream surface port-ions of the nozzle ring 46 and disc 27, respectively, jointly define an annular sealing space 79, which space is in direct and unrestricted flow communication with the passages 75. The passages 75, in turn, are in direct communication with the second expansion stage 23.

In operation, hot motive elastic fluid is admitted joint- 1y through the conduits 32 to the first expansion section 12 and the conduits 60 to the second expansion section 14.

First considering expansion section 12, the motive fluid A is directed through the nozzle chamber 31 to the first expansion stage 22 (at a first temperature and pressure) and, during such flow, all but a small portion of the main fluid stream is directed through the rotor blades 28 to motivate the rotor, for example in the direction of the arrow D in FIG. 3. Small amounts of leakage are directed around the outer shroud 44 of the blades 28 past the seals 46, and this leakage subsequently rejoins the main motive stream in the distribution space 52. A sec ond leakage path, as indicated by the arrows E, is established, and this leakage path is in direct communication with the sealing space 79, but in indirect restricted flow communication with the seal structure 48.

The pumping apertures 54, during operation, are effective to pump a small portion of the expanded motive fluid (at a second and lower temperature and pressure) from the distribution space 52 through the disc 27 into the leakage space S, as indicated by the arrows F. The pumped motive fluid F is thus directed along the surface portions of the rotor to cool the same and then mixes with partially expanded motive fluid A adjacent the sec- 0nd stage 23 for further expansion. Accordingly, it will be seen that pumped motive fluid F flowing through the leakage space S is effective to provide continuous blanketing flow of expanded and thus cooler fluid along the rotor surfaces 80 and transfer the heat extracted during such flow to the second stage 23.

Since the second seal structure 76 is interposed between the outlet of pumping apertures 54 and the sealing space 79, flow of the hotter blade leakage fluid E into the leakage space is substantially eliminated because of the high restriction to any such leakage imposed by the seal structure 76. Conversely, the leakage flow E preferentially flows through the second passages 75 to rejoin the motive fluid A. The passages 75 are in direct heat exchange relation with the nozzle boxes 33 and nozzle ring 40, which further act to shield the rotor surfaces from the heating effect of the fluid leakage E.

It will now be seen that with this arrangement the hot leakage fluid E is prevented from mixing with the cooler pumped fluid F and is further directed through stationary structure that is readily capable of operating at higher temperature than the rotating components.

The expansion section 12 may be operated at a higher pressure than the expansion section 14, and, as well known in the art, the motive fluid after expansion in the z first section 12 and exhausted through the exhaust outlet 38, may be directed to a suitable reheater (not shown), where it is reheated to substantially the same inlet temperature value as originally, before employment in the second expansion section 14.

A small portion of motive fluid after expansion in the first stage 22 unavoidably escapes through the labyrinth seals 69 into the second expansion section 14 and serves the useful function of providing cooling for the second expansion section 14. This cooling is primarily effective in the higher expansion stages of the second section 14, where the operating environment is at its highest temperature value, so that the higher stages of the second section 14 are protected against overheating.

The invention is primarily advantageous when employed with .a governing stage of a turbine. However, it is not so limited and may also be employed with other types of stages employing reaction blades, for example.

Although only one embodiment has been shown, it 4 will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

What is claimed is:

1. A cooling and sealing arrangement for an axial flow elastic fluid turbine, comprising a rotor having a disc portion provided with a peripheral row of motor blades,

a stationary nozzle structure provided with an annular row of nozzle vanes for directing a stream of hot motive elastic fluid to said rotor blades,

said disc having a downstream face,

said nozzle structure being disposed in spaced relation with said disc,

said nozzle structure having a circular radially innermost surface disposed in closely spaced encompassing relation with said rotor and jointly therewith defining a leakage space,

first and second seal means disposed between said rotor disc and said nozzle structure for minimizing leakage of unexpanded motive fluid from said stream and jointly with said disc and said nozzle structure forming a sealing space,

means for pumping expanded motive fluid through the downstream face of said disc to said leakage space to minimize overheating of said rotor, and

passage means extending through said nozzle structure and communicating with said sealing space for bleed- 6 ing accumulating unexpanded motive fluid from said sealing space,

said second sealing means being effective to restrict flow of unexpanded fluid from said sealing space to said leakage space.

2. A cooling and sealing arrangement for an axial flow elastic fluid turbine having at least two expansion stages, comprising a rotor having a disc portion provided with a first peripheral row of rotor blades and another portion provided with a second row of rotor blades,

a stationary nozzle structure provided with an annular row of nozzle vanes for directing a stream of hot motive elastic fluid to said first rotor blades at a first temperature and pressure,

means for directing motive fluid to said second row of rotor blades at a second and lower temperature and pressure,

said disc having an upstream face and a downstream face,

said nozzle structure having a downstream face disposed in spaced relation with the upstream face of said disc,

said nozzle structure having an annular surface disposed in closely spaced relation with said rotor intermediate said disc portion and said other portion and jointly with said rotor defining a leakage space communicating with said directing means upstream of said second row of rotor blades,

first and second seal means disposed between the upstream face of said rotor disc and the downstream face of said nozzle structure for minimizing leakage of unexpanded motive fluid from said stream and jointly with the upstream disc face and the downstream nozzle face forming a sealing space,

means for pumping expanded motive fluid through said disc to said leakage space to minimize overheating of said rotor and thence to said second rotor blades for subsequent expansion, and

passage means extending through said nozzle structure and communicating at one end with said sealing space and at the other end with said directing means upstream of said second rotor blades for bleeding accumulating unexpanded motive fluid at substantially said first temperature from said sealing space,

said second sealing means being effective to minimize flow of unexpanded fluid from said sealing space to said leakage space.

3. A cooling and sealing arrangement for an axial flow elastic fluid turbine having at least two expansion stages, comprising a rotor provided with first and second peripheral rows of rotor blades,

first and second stationary nozzle structure provided with first and second annular rows of nozzle vanes cooperatively associated with said first and second rotor blades, respectively,

said rotor having a disc portion carrying said first blades and having an upstream face and a downstream face,

said first nozzle structure having a downstream face disposed in spaced relation with the upstream face of said disc and a circular radially innermost surface disposed in closely spaced encompassing relation with said rotor and jointly therewith defining a leakage space communicating with said second rotor blades,

means for directing a stream of hot motive fluid to said first nozzle structure for expansion in said first rotor blades,

first and second seal means disposed between the upstream face of said rotor disc and the downstream face of said first nozzle structure for minimizing leak age of unexpanded motive fluid from said stream and jointly with the upstream disc face and the downstream nozzle face forming a ealing space,

means for umping motive fluid expanded by said first rotor blades through said disc to said leakage space to minimize overheating of said rotor, and

means including a passage extending through said first nozzle structure and communicating at one end with said sealing space and at the other end with said second rotor blades for bleeding accumulating unexpanded motive fluid from said sealing space,

4. The structure recited in claim 3 in which,

the motive fluid directing means includes annular nozzle box structure provided by the first nozzle structure, and further including wall structure defining a chamber for redistribution of the motive fluid expanded in the first rotor blades, and

means including said chamber for directing the fluid expanded in the first rotor blades to the second nozzle structure.

5. The structure recited in claim 3 in which,

the motive fluid directing means includes annular nozzle box structure provided by the first nozzle structure, and further comprising wall structure defining a chamber for redistribution of the motive fluid expanded in the first rotor blades,

the first and second nozzle structures being disposed in spaced axially opposed relation to each other, and

, means including said chamber for reversing and directing the flow of the motive fluid expanded in the first rotor blades to the second nozzle structure for further expansion.

6. A high temperature axial flow elastic fluid turbine,

comprising a first motive fluid expansion stage and a second motive fluid expansion stage arranged in back-to-back series flow relation with each other,

said first stage including a nozzle structure having an annular row of stationary nozzle vanes,

a rotor structure having a disc portion disposed adjacent said nozzle structure and having a first annular row of blades circumferentially disposed thereon and cooperatively associated with said nozzle vanes,

said rotor structure having a portion extending to said second expansion stage and having a second row of blades forming a part of said second stage,

said nozzle structure being disposed in closely spaced encompassing relation with said rotor portion and jointly therewith defining a motive fluid leakage space,

means for axially directing motive fluid at a first temperature and pressure past said nozzle vanes and said first rotor blades,

said rotor disc having a plurality of apertures effective to pump through said disc to said leakage space, a portion of the partially expanded motive fluid leaving the first stage thereby to minimize overheating of said rotor portion,

first sealing means interposed between said nozzle structure and said disc for minimizing leakage therebetween of the motive fluid at said first temperature,

second sealing means interposed between said nozzle structure and said disc for minimizing leakage into said leakage space of the motive fluid leakage past said first sealing means, and

means including an annular array of apertures extending through said nozzle structure for directing to said second stage the motive fluid leakage from said first sealing means.

'7. A high temperature axial flow elastic fluid turbine,

comprising a first motive fluid expansion stage and a second motive fluid expansion stage arranged in axially opposed series flow relation with each other,

a rotor structure having a disc portion disposed adjacent said nozzle structure and having a first annular row of blades circumferen-tially disposed thereon and cooperatively associated with said nozzle vanes,

said nozzle structure further comprising an annular nozzle box structure disposed in closely spaced encompassing relation with said rotor portion and jointly therewith defining a motive fluid leakage space,

conduit means for admitting motive fluid at a first temperature and pressure to said nozzle box structure for. expansion in said nozzle vanes and said first rotor blades,

said rotor disc having a plurality of apertures eflective to pump through said disc to said leakage space a portion of the partially expanded motive fluid leaving the first stage,

second sealing means spaced from said first means and interposed between said nozzle structure and said disc for minimizing leakage into said leakage space of the motive fluid leakage past said first sealing means, and means including an annular array of apertures extending through said nozzle box structure for directing to said second stage the motive leakage fluid from said first sealing means.

References Cited by the Examiner UNITED STATES PATENTS 815,973 3/06 McKee 25339 FOREIGN PATENTS 1,262,633 4/61 France. 1,030,357 5/58 Germany.

929,103 6/63 Great Britain. 593,731 5/39 It-aly.

KARL I, ALBRECHT, Primary Examiner.

HENRY F. RADUAZO, Examiner.

Claims

1. A COOLING AND SEALING ARRANGEMENT FOR AN AXIAL FLOW ELASTIC FLUID TURBINE, COMPRISING A ROTOR HAVING A DISC PORTION PROVIDED WITH A PERIPHERAL ROW OF MOTOR BLADES, A STATIONARY NOZZLE STRUCTURE PROVIDED WITH AN ANNULAR ROW OF NOZZLE VANES FOR DIRECTING A STEAM OF HOT MOTIVE ELASTIC FLUID TO SAID ROTOR BLADES, SAID DISC HAVING A DOWNSTREAM FACE, SAID NOZZLE STRUCTURE BEING DISPOSED IN SPACED RELATION WITH SAID DISC, SAID NOZZLE STRUCTURE HAVING A CIRCULAR RADIALLY INNERMOSTO SURFACER DISPOSED IN CLOSELY SPACED ENCOMPASSING RELATION WITH SAID ROTOR AND JOINTLY THEREWITH DEFINING A LEAKAGE SPACE, FIRST AND SECOND SEAL MEANS DISPOSED BETWEEN SAID ROTOR DISC AND SAID NOZZLE STRUCTURE FOR MINIMIZING LEAKAGE OF UNEXPANDED MOTIVE FLUID FROM SAID STEAM AND JOINTLY WITH SAID DISC AND SAID NOZZLE STRUCTURE FORMING A SEALING SPACE, MEANS FOR PUMPING EXPANDED MOTIVE FLUID THROUGH THE DOWNSTREAM FACE OF SAID DISC TO SAID LEAKAGE SPACE TO MINIMIZE OVERHEATING OF SAID ROTOR, AND PASSAGE MEANS EXTENDING THROUGH SEAID NOZZLE STRUCTURE AND COMMUNICATING WITH SAID SEALING SPACE FOR BLEEDING ACCUMULATING UNEXPANDED MOTIVE FLUID FROM SAID SEALING SPACE, SAID SECOND SEALING MEANS BEING EFFECTIVE TO RESTRICT FLOW OF UNEXPANDED FLUID FROM SAID SEALING SPACE TO SAID LEAKAGE SPACE.