US3172640A

US3172640A - Dry band francis turbines

Info

Publication number: US3172640A
Application number: US271169A
Authority: US
Inventors: Robert S Sproule
Original assignee: Dominion Engineering Works Ltd
Current assignee: Dominion Engineering Works Ltd
Priority date: 1963-04-08
Filing date: 1963-04-08
Publication date: 1965-03-09
Anticipated expiration: 1982-03-09
Also published as: GB1013638A; CH427697A

Description

3 Sheets-Sheet l INVENTOR.

ATTOPNE).

March 9, 1965 R. s. SPROULE DRY BAND FRANCIS TURBINES Filed April 8, 1963 ROBERT S. S'PEOULE March 9, 1965 R. s. SPROULE 3,172,640

DRY BAND FRANCIS TURBINES Filed April 8, 1963 3 Sheet.sSheet 2 zany:

INVENTOR- 'EOBE'ET S S'PEOU LE BY p A T TZPNE K March 9, 1965 R. s. SPROULE 3,172,640

DRY BAND FRANCIS TURBINES Filed April 8, 1963 s Sheets-Sheet 5 X7 2). 27 W i. 3-

INVENTOR. ROBERT S. S'P'EOULE ATT IPA/EX United States Patent 3,172,640 DRY BAND FRANCIS TURBINES Robert S. Sprouie, Montreal, Quebec, Canada, assignor to Dominion Engineering Works Limited Filed Apr. 8, 1963, Ser. No. 271,169 2 Claims. (Cl. 25326) This invention relates to hydraulic turbines of the Francis type or similar hydraulic machines, and has particular reference to the provision of new and improved means for the reduction of frictional losses caused by churning in the annular space between the runner band and the surrounding stationary ring.

An object of the invention is to provide new and improved means for improving the efliciency of hydraulic turbines of the Francis type or similar hydraulic machines through the reduction of fluid frictional losses.

Another object of the invention is to provide new and improved means of the type set forth, which act to reduce frictional losses caused by churning in the annular space between the runner band and the surrounding stationary ring in hydraulic turbines of the Francis type or similar hydraulic machines.

Another object of the invention is to provide new and improved means of the type set forth, which effect separation of air and water by providing a relatively free path for the escape of water while impeding escape of air.

Another object is to provide new and improved means of the type set forth, to minimize the power required to pump air into the annular space between the runner band and the surrounding stationary ring.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings. It will be understood that changes may be made in the details of construction and arrangement of parts shown and described, as the preferred form of invention has been given by way of illustration only. Referring to the drawings:

FIG. 1 is a fragmentary radial vertical section of a Francis turbine incorporating a preferred execution of the invention;

FIG. 1A is an enlarged view of the portion of FIG. 1 shown encircled;

FIG. 2 is a detailed view of that portion of FIG. 1A shown encircled;

FIG. 3 is a sectional View taken on line 3-3 of FIG. 2, looking in the direction of the arrows, and

FIG. 4 is a sectional view taken on line 44 of FIG. 2, looking in the direction of the arrows.

Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout the several views, and with particular reference to FIGS. 1 and 1A, such figures show the boundaries of annular space 16 between runner band 36 and static structure 19. In the operation of the turbine, water enters the turbine from inlet casing 11 and passes stay vanes 12 and wicket gates 13 before flowing through runner 15 and discharging from the turbine by way of draft tube 17.

The band 36 of runner 15 is provided with a sealing face 24, which cooperates with sealing face 25 of lower distributor ring 14. Seal leakage water 23 enters annular space 16 through clearance 22 between sealing

faces

24 and 25.

Baulk ring 21 and air supply pipe 20 are also illustrated in FIGS. 1 and 1A; said baulk ring being located near to, and outside of, the lower extremity of runner band 36.

Said baulk ring acts to impede the escape of air and to facilitate the escape of water from annular space 16. Said baulk ring, an important feature of the present invention, is more clearly illustrated in FIGS. 2, 3 and 4.

Referring to FIG. 2, such is an enlarged view of the ice encircled portion of FIG. 1A, and illustrates details of baulk ring 21 and its environment. From such figure, it may be seen that when the turbine is in operation, rotating band 36 of runner 15 drives accumulated leakage water 23 in the form of a rotating annulus 34, the tangential velocity component of which is a minimum at vertical face 39 of static structure 19. In existing Francis turbines, there is a zone of turbulence between periphery 38 of runner band 36 and vertical face 39 of static structure 19; in a turbine constructed in accordance with the present invention, there is provided an escape path 28 for leakage water 23, through which said leakage water escapes to draft tube 17 by way of spaces 27 between baulk ring 21 and static structure 19.

Between spaces 27, uniformly-spaced webs 26 are positioned, said webs being attached to horizontal face 29 of static structure 19. Webs 26 support baulk ring 21.

Instead of the web and space shown, any practicable structure may be employed for attachment of the baulk ring 21 to the static structure 19 which allows flow of water past the outside diameter and the lower face of the baulk ring.

It has been found that baulk ring 21 is most efficient when the vertical dimension of openings 27 is approximately one-half of the vertical distance from horizontal face 30 of runner band 36 to horizontal face 29 of static structure 19. The present invention is not limited to this proportion, however, and such is given only as a preference and not as a requirement. Vertical face .32 of runner band 36 cooperates with vertical face 33 of baulk ring 21 to impede escape of air through radial clearance 35 from annular space 16.

In short, baulk ring 21 functions to provide a means of assuring deaeration of the leakage water before it is discharged to the draft tube, and serves as a bafiie to discourage recirculation in an axial direction in the annular space 16 and, hence, reduces turbulence.

Baulk ring 21, therefore, substantially reduces the amount of air that must be supplied to annular space 16 in order to keep the periphery of band 36 free from contact with water, improves the drainage of leakage water to draft tube 17 and improves the efliciency of the turbine by reducing frictional losses at the band.

From the foregoing, it will be apparent that I have provided new and improved means for accomplishing all of the objects and advantages of the invention.

I claim:

1. In a Francis turbine, a static structure having a smoothly continuous surface portion, a draft tube, a runner having a band shroud with upper and lower edges adjacent to said static structure but spaced therefrom to provide running clearances at said upper and lower edges, said smoothly continuous surface portion and said band defining an annular space between said shroud and said static structure communicating with said clearances between the shroud and the static structure at both the upper and lower edges of said shroud, air supply means through said static structure for supplying air to said annular space, a distributor ring supplying water under pressure to the runner, said distributor ring spaced from said upper edge of said shroud and provided with a sealing face, a sealing face around the upper portion of said band shroud for cooperating with said sealing face on the distributor ring so as to restrict the flow of leakage water into said annular space through the clearance between the static structure and the upper edge of the shroud, a baulk ring fixed to said static structure in said annular space adjacent to the lower edge of said shroud but spaced therefrom to provide a running clearance therebetween, said baulk ring being supported in spaced relationship from said static structure so that an annular passage is provided between the static structure and the baulk ring, said shroud on rotation forming a rotating ring of water adjacent to said smooth surface of the static structure to permit the escape of leakage Water only from the annular space around the baulk ring and through the clearance between the static structure and the lower edge of the shroud into the draft tube. v

2. A Francis turbine as claimed in claim 1 in which the support for the baulk ring comprises a series of spaced webs secured to thestatic structure at points within said annular space, the openings between adjacent webs being used to permit the escape of leakage water from the annular space into the draft tube References Cited by the Examiner UNITED STATES PATENTS KARL J. ALBRECHT, Primary Examiner. JOSEPH H. BRANSON, JR., Examiner.

Claims

1. IN A FRANCIS TURBINE, A STATIC STRUCTURE HAVING A SMOOTHLY CONTINUOUS SURFACE PORTION, A DRAFT TUBE, A RUNNER HAVING A BAND SHROUD WITH UPPER AND LOWER EDGES ADJACENT TO SAID DISC STRUCTURE BUT SPACED THEREFROM TO PROVIDE RUNNING CLEARANCES AT SAID UPPER AND LOWER EDGES, SAID SMOOTHLY CONTINUOUS SURFACE PORTION AND SAID BAND DEFINING AND ANNULAR SPACE BETWEEN SAID SHROUD AND SAID STATIC STRUCTURE COMMUNICATING WITH SAID CLEARANCES BETWEEN THE SHROUD AND THE STATIC STRUCTURE AT BOTH THE UPPER AND LOWER EDGES OF SAID SHROUD, AIR SUPPLY MEANS THROUGH SAID STATIC STRUCTURE FOR SUPPLYING AIR TO SAID ANNULAR SPACE, A DISTRIBUTOR RING SUPPLYING WATER UNDER PRESSURE TO THE RUNNER, SAID DISTRIBUTOR RING SPACED FROM SAID UPPER EDGE OF SAID SHROUD AND PROVIDED WITH A SEALING FACE, A SEALING FACE AROUND THE UPPER PORTION OF SAID BAND SHROUD FOR COOPERATING WITH SAID SEALING FACE ON THE DISTRIBUTOR RING SO AS TO RESTRICT THE FLOW OF LEAKAGE WATER INTO SAID ANNULAR SPACE THROUGH THE CLEARANCE BETWEEN THE STATIC STRUCTURE AND THE UPPER EDGE OF THE SHROUD, A BAULK RING FIXED TO SAID STATIC STRUCTURE IN SAID ANNULAR SPACE ADJACENT TO THE LOWER EDGE OF SAID SHROUD BUT SPACED THEREFROM TO PROVIDE A RUNNING CLEARANCE THEREBETWEEN, SAID BAULK RING BEING SUPPORTED IN SPACED RELATIONSHIP FROM SAID STATIC STRUCTURE SO THAT AN ANNULAR PASSAGE IS PROVIDED BETWEEN THE STATIC STRUCTURE AND THE BAULK RING, SAID SHROUD ON ROTATION FORMING A ROTATING RING OF WATER ADJACENT TO SAID SMOOTH SURFACE OF THE STATIC STRUCTURE TO PERMIT THE ESCAPE OF LEAKAGE WATER ONLY FROM THE ANNULAR SPACE AROUND THE BAULK RING AND THROUGH THE CLEARANCE BETWEEN THE STATIC STRUCTURE AND THE LOWER EDGE OF THE SHROUD INTO THE DRAFT TUBE.