US1820150A - Labyrinth packing for turbines - Google Patents

Description

Aug. 25, 1931. MOODY 1,820,150

LABYRINTH PACKING FOR TURBINES Filed Sept. 15, 1920 3 Sheets-Sheet l U 8 M'UlzM l'o'e', 333% abl mme lg Aug. 25, 1931. F. MOODY 1,820,150

LABYRINTH PACKING FOR TURBINES Filed Sept. 15. 1920 3 Sheets-Sheet 2 16; 6 WWW Aug. 25, 1931.

L. F. MOODY LABYRINTH PACKING FOR TURBINES Filed Sept. 15, 1920 3 Sheets-Sheet 3 Patented Aug. 25, 1931 UNITED STATES earaur orrica LEWIS FERRY. MOODY, OF PHILADELPHIA, PENNSYLVANIA LABYBINTH PACKING FOB TURBINES Application filed September 15, 1920.

reducing the leakage of water between the runner and the surrounding stationary parts of a. rotary hydraulic machine, and more particularly the provision or" such apparatus in hydraulic turbines; and at the same time to provide means for reducing the axial thrust of the water upon the runner. Another object of this invention is to provide such apparatus so formed as to avoid extremely small clearances, and thus to reduce the risk of clogging by foreign matter carried by the water and the danger of injury from rubbing between the parts. These and other objects will be understood upon consideration of disclosures of several specific examples embodying the invention. It will be understood that modifications may be made within the scope of the invention.

In the accompanying drawings illustrating the invention Fig. 1 is a sectional elevation through the axis of a vertical shaft hydraulic turbine.

Fig. 2 is an enlarged view of a detail of Fig. 1 slightly modified.

Fig. 3 is a sectional view of another embodiment of the invention, and

Fig. 4 is an axial section of another turbine embodying the invention. In the embodiment of the invention shown inFig. 1 an entrance volute 5 guides the flow to the adjustable guide vanes 6 directing it onto the vanes of the runner R having shaft and discharging into the drafttube T. A

cover casting 7 carries bearings for the shaft S and the stems 10 of adjustable guide vanes 6. ,The runner R is formed with cylindrical ridges A machined upon its crown and band with intervening circular grooves B between the successive ridges. Into these grooves project correspondng ridges formed upon stationary plates C and D bolted to the surrounding portions of the turbine structure. Inthe design shown, the crown and band of the runner and the plates C and D are so formed that there are six points of contracted area through which the leakage water must flow to escape either above or below the runner, the first point of contraction being Serial N0. 410,454.

the simple straight seal formed between the runner periphery and plate. The water flowing through these points of small clearance will acquire a considerable velocity due to the pressure head existing in the space between the guide vanes and runner. This velocity will, however, be materially lower than it would be if a single point of small clearance were employed. If there were only a single clearance point, the water would acquire at such a point a velocity proportional. to the square root of the entire pressure producing the "leakage flow, By using a multiple arrangement of seals such as here shown the pressure head producing the leakage flow is sub-divided into a series of stages (here six) so that the velocity of flow becomes proportional to the square root of the pressure drop through only one stage, or I in this case, one-sixth of the entire pressure producing the flow. Without considering other features of the device, therefore, the ar singing of a number ofcontractions in series materially reduces the flow throu h the seal. In addition to arranging a num er of seals in series a sudden enlargement is left in the groove between each two seals in which a loss of head is imposed-upon the leakage flow due to the dissipation of velocity head, and these enlargements are so formed as to facilitate the producing of an eddy or eddies in the water filling the space. Just as-it is important to avoid in the main fiow ofthe water through the turbine any points in the water passage where eddies are likely to be formed, it is correspondingly important to introduce wherever possible in the passage through which the leakage water must fiow, spaces in which eddies may fornn Another purpose of the enlargements between successive seals is to provide a considerable body of Tater capable of momentarily absorbing any heat produced by friction if local rubhing should occur between the rotating and stationary surfaces.

After the leakage water has passed through the clearances, the water above the runner R flows into the spaces between the head cover plate 9 and the runner disc 11, and the; water flowing below the runner discharges into the l d Hi draft tube T. In order to reduce the disc friction on the runner, the width of the space between the runner crown 11 and the cover plate 9 and that surrounding the runner band is made small to reduce to a minimum the body of water in said spaces and both the runner and surrounding parts are given smooth circular contours with as little surface exposed to the water as possible. Since the water whirling in the space between the runner and head cover will tend to set up centrifugal pressures increasing toward the outer periphery, relief holes h are provided at or near the outer periphery of the spaces, through which the water may escape and thus relieve the pressure upon the runner, thereby reducing the hydraulic thrust which must be carried by the thrust bearing supporting the rotating parts of the unit. In the arrangement shown in Figure 1 the leakage water flowing through holes it above the runner escapes through the pipe at F which is a drain leading to the tailwater.

Another method of relieving the thrust, and one which forms in combination with the arrangement of seals described above an essential part of this invention, is shown in Figure 3. In this figure a modified arrangement of seals A B is shown, there being four points of small clearance at top and bottom of the runner instead of six. An arrangement of seals more like that of Figures 1 or 4 could be used in Figure 3 where desired. In the turbine here shown, llat liner plates 17, p are shown attached to the runner crown 8 and to the head cover 7 respectively, the head cover 7' being formed with an inner wall carrying the liner p. The liners are used for purposes of renewal in case of wear or corrosion, and may be used when desirable. The essential feature of this rrangenient as the stationary plate P forming part of the head cover, and located adjacent to the runner crown 8. This plate is connected to the upper wall of the head cover 7 by radial vertical ribs 1". The plate at its inner periphery forms a running clearance or seal with an extension of the runner hub u. Near the outer periphery of the space between the runner crown and the inner plate of the head cover, relief holes h are placed connecting with the space between the two walls of the head cover. The tendency of the water within the space between the runner crown and the lower plate of the head cover to set up centrifugal pressure is avoided by these relief holes which permit the leakage flow to be bypassed through the head cover and thence down through openings H in the runner hub into the center of the draft tube T, a point where low pressure exists. The vertical ribs 1 forming part of the head cover prevent any whirling of the water within the head cover, and thus avoid imposing a contrifugal force obstructing the flow. The small clearance or seal between the extension at of the runner hub and the inner periphery of the lower head cover plate P prevents a. return of the water into the space between the runner crown and head cover. If such a return were permitted, there would be a secondary circulation set up which would absorb a considerable amount of energy and which would also impair the relief of the pressure on the runner disc provided by this device.

The special arrangement of seals A, B when used in conjunction with the method of pressure relief just described cooperates with it to make the combination effective. If a single seal were used, the high rate of leakage would impair the action of the remainder of the device, particularly after the turbine has been in use for a considerable time, and wear due to either rubbing or cutting produced by the high velocity of flow has taken place. A large quantity of water flowing through the relief holes would result in a back pressure, and end thrust on the runner would be caused.

In Figure 3 the leakage water at the top of the runner passes through a relatively tortuv one and restricting seal A, B, to the chamher between the wearing plates 1), p. The pressure in this upper chamber is relieved as imlicatcd at and u to the draft tube so that the pressure in this chamber is substantially equal to or even less than that in the draft tube. The tendency of the centrifugal force of the water whirling in the space between 79 and p, together with the seal it, is to reduce the pressure in the inner portion of this space below that at it, that is belowthe pressure in the draft tube. The drop is pressure through the seal A, B, at the outer edge of the top of the runner is substantially the whole drop of pressure from the inlet to the draft tube.

At the bottom of the runner the seal through which the leakage must pass to the draft tube is divided into two portions, A and A, the upper seal A at the bottom of the runner being relatively simple 1n form so that only a part of the pressure drop from inlet to draft tube occurs at that point. The pressure in the chamber 1 at the bottom of the runner thus materially higherthan the pressure in the chan'iber between the plates 0, g) at the top of the runner.

Fig. t shows a horizontal section through the axis of a single runner horizontal shaft turbine in which a modified embodiment of this invention is employed. In this arrangement the runner 15 carries the crown plate 16 and band plate 17 having alternate grooves b and a. fitting the grooves and ribs of the stationary plates 19 and 20 respectively. The two stationary plates 19, 20 are made adjustable, bolts 28, 24 being provided for screwing down the plates to dress them toward the runner while bolts 21, 22 hold them from contact with the runner. The seals provided by the interfitting ribs and grooves are dividedinto two groups on both the crown and band of the runner, spaces 25, 26 being left between the groups in which the pres sure will be automatically regulated to maintain the runner in central position under all conditions of operation.

Between the plate 16 and the wearing ring 29 is a thin cylindrical passage 27 providing clearance or a simple seal which necessarily involves some leakage inward from the turbine intake. Following this passage 27 along the direction of leakage flow, the thin cylindrical portion 27 opens into the wider plane annular portion 28. Thus the size of the passage as awhole and its direction are changed abruptly at the same point, namely, where the portion 27 opens into the portion 28. Between the annular teeth or ribs a respectively on the runner and on the casing, the pas sage extends in thin cylindrical form, the flow being in the opposite direction to that in the passage 27, and again at 30 there is ail-abrupt change of direction with an increase of width. The passage then again continues through the narrow cylindrical portion between the ribs thence with an abrupt change of direction and enlargement to the plane annular portion 28, and so alternately narrowing or expanding at each change of direction. At each change of direction the passages are undercut a little as indicatedat 21.

Thence the passage continues through the enlarged portion 25, into the inner set of Seals which have the shape of a section of a conical surface cut off therefrom by two planes perpendicular to the axis and the tortuous path through these inner seals finally terminates at the point 32 of low pressure in the inner chamber 33 connected to the discharge. If the runner moves toward the head cover, it will be seen that this wedge arrangement of the inner set of seals will cause these seals to close and thus to restrict the flow of water on the head cover side. The clearance of the outer set of seals will remain the same for all positions of the runner. The restriction of the flow through the inner set of seals and the consequent increase of pressure produced in the intermediate space 25 will set up a thrust upon the runher crown which will tend to restore the runner to its central position. A similar ar-- rangementof outer and inner seals and intermediate space 26 is provided on the runner band and if the runner should travel too far in the opposite direction, a reduction of pressure will be caused in the intermediate space on the crown of the runner, and this, together with the opposite action occurring against the runner band, that is, an increase in pressure in the intermediate space against the band, will prevent the runner moving toward the draft tube. The device shown in this figure therefore provides an automatic balance and prevents any end thrust being developed by the runner.

It will be noted that in the inner set of seals enlargements of the passage are provided at points where the flow changes direction. This is in accordance with the principle which is followed in all of the arrangements of seals shown, that between each two points of small clearance a space isprovided in which the flow must change both in the direction and magnitude of its velocity, that is, the passage is enlarged at the same time that the direction of flow is altered. It

is not suflicient, for example, to provide enlargement of a passage and then to follow this enh-irgement by a second contraction directly in line with and in the same direction as the original contraction, for in such a de sign the water passes through the enlargement without its velocity being appreciably affected and without suifering a material loss of head.

I claim 1- i 1. In a rotary hydraulic machine, a casing, a rotor with vanes therein, a conduit through the casing to deliver water to the vanes of the rotor and another such conduit to convey the water away, the casing and runner having adjacent opposed faces spaced to form a passage between them, said passage consisting of a narrow part opening into a relatively wide part with an abrupt change of direction at the transition, then another narrow passage extending in a direction opposite to the direction of the preceding narrow passage, and soon repeatedly, at least two of said narrow parts with an intermediate wide pafrt constituting a passage through which leakage must flow.

2. In a rotary hydraulic machine, a casing, a rotor with vanes therein, a conduit through the casing to deliver water to the vanes of the rotor and another such conduit to convey the water away, the casing and runner having adjacent opposed faces spaced to form two similar passages between said faces on opposite sides of the runner, each of said passages consisting of a narrow part opening into a relatively wide part with an abrupt change of direction at the transition, then another narrow passage extending in a direction opposite to the direction of the preceding narrow passage, and so on repeatedly. i I

3. In a rotary hydraulic machine, a casing, a rotor with vanes therein, a conduit through the casing to deliver water to the vanes of the rotor and another such conduit to convey the water away, cicuniferential spaced ribs on the inner face of the casing and on the adjacent face of the runner interlocking alternately to form a leakage labyrinth, said ribs forming narrow-passages between them extending alternately in opposite directions and said ribs being undercut to give enlargements of the labyrinth, passage at each alternate change of direction thereof.

4. A labyrinth seal for a hydraulic machine comprising relatively rotatable parts formed to provide a series of narrow passages extending alternately in opposite directions and with enlarged connecting spaces between the ends of said passages so that the leakage water is passed with abrupt changes of direction and eddies set up in the flow at each such change of direction;

5. A labyrinth seal for a hydraulic machine comprising rotatable parts on opposite sides of the rotor of said machine with passages on opposite sides of said rotor adapted to pass the leakage water in two zig zag streams with narrow passages in alternately opposite directions and enlargements at'the places of change of direction.

6. In a hydraulic turbine in combination, labyrinth seals consisting of a plurality of contracted passages through which the leakage water escaping from the runner must flow in series, and alternating with said contracted passages enlarged passages in which the leakage fiow is deflected; a stationary plate adjacent to the runner crownhaving a contracted running clearance at its inner periphery, and relief openings through it at its outer periphery through which the leakage water can flow after passing through one of said labyrinth seals.

7. In a hydraulic turbine in combination, labyrinth seals consisting of a plurality of contracted passages through which the leakage water escaping from the runner must flow in series, and alternating with said contracted passages enlarged passages in which the leakage flow is deflected; a stationary plate adjacent to the runner crown having-a contracted running clearance at its inner periphery, and relief openings through it at its outer periphery through whichthe leakage water can flow after passing through one of said labyrinth seals, and passages outside of said plate leading to relief openings through the runner hub discharging the leakage water into the centre of the turbine draft tube.

8. In a hydraulic turbine a runner forming in combination with the surrounding s ationary parts of the turbine a plurality of contracted passages alternating with passages which enlarge in cross-section and simultaneously change the direction of flow, so disposed that the leakage water escaping from the runnermust flow through a series of said passages in succession, and means near the periphery of said runner through which the leakage water can escape to a point of low pressure, after it has passed through said it? passages.

1 9.- Ina vertical shaft turbine the' combination with a runner and means for supplying water thereto, of means for relieving downwater thereto, of means for relieving downward pressure on the top of the runner comprising a chamber abovethe runner and a relief opening at he outer portion ofsaid chamber leading through passages separated from the runner, followed by passages through runner crown or hub to the draft tube of the turbine.

" Q in a vertical shaft turbine the combinathereto, of means for relieving down- "d pressure on the top of the runner comprising stationary and rotatable surfaces forming a chamber above the runner and a relief opening at the outer portion of said chamber communicating with the centralportion of the draft tube through a'passage extending round said stationary surface and out of contact with the runner. 1

13. In a vertical shaft'turbine the com- A bination with a runner and means for supplying water thereto, of means for relieving downward pressure on the top of the-runner comprising stationary and rotatable surfaces adjacent to each other and forming a restricted chamber above the runner and a relief opening at the outer portion of said chamber.

14. In turbine the combination with a runner and means for supplying water thereto and clearance spaces at opposite sidesof said runner, one of said spaces having a relief connection at its outer portlon and the other of said spaces having a relief connection at its inner portion and labyrinth seals to reduce leakage into or out of said spaces.

15. In a Water turbine, a runner, a stationary part within which the periphery of the runner rotates, a chamber above the runner,

:h a runner and means for supplying r ward pressure on the'top of the'runner comprising a chamber above the runner and a relief opening at the outer portlon OfSZLlCl chamsaid chamber having a relatively free outlet for the water and having a tortuous passageway or labyrinth seal constituting its inlet and located between the upper part of the runner and the associated stationary part,

said warts and assa ew'a sbein constructed and arranged to cause the pressure above the runner to be materially less than below the same.

16. In a Water turbine, a runner, a housing enclosing the runner and having annular surfaces in proximity to which the peripheral part of the runer rotates, Water seals at the upper and lower portions of the runner, the seal at one point being relatively restricted, and the seal at another being relatively unrestricted.

17. In a Water turbine, a runner, a stationary part Within which the runner rotates, means forming a chamber located on the up per side of the runner, including a cover overlying and spaced from a top portion of the runner, and means forming a seal to restrict fluid flow to said chamber, said cover being provided With a relatively free outlet Whereby fluid in said chamber may be easily discharged.

18. In a Water turbine, a runner, a casing Within Which the runner rotates, and clearance spaces between the runner and easing such that leakage through one space is relatively restricted and leakage through the other is relatively free.

LEWIS FERRY MOODY.

CERTIFICATE or connection.

Patent No. 1,820,150. Granted August 25, 1931, to

LEWIS FERRY MOODY.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 129, for "dress" read press; page 3, line 34, for the numeral "21" read 31; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of November, A. D. 1931.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

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