US3246874A - Overspeed limiting device for hydraulic machines - Google Patents

Description

April 19, 1966 R. s. SPROULE OVEHSPEED LIMITING DEVICE FOR HYDRAULIC MACHINES 2 Sheets-Sheet 1 F5 led Feb. 15, 1965 AIR OUT April 19, 1966 R. s. SPROULE 3,246,874

OVERSPEED LIMITING DEVICE FOR HYDRAULIC MACHINES Filed Feb. 15, 1965 2 Sheets-Sheet 2 INVENTOR. "ROBERT 6- SPEOULE BY ZM/J United States Patent 3,246,874 OVERSPEED LIMITING DEVICE FQR HYDRAULIC MACI-HNES Robert Stanley Sproule, Montreal, Quebec, Canada, as-

signor to Dominion Engineering Works, Limited, Quebec, Quebec, Canada, a corporation of Canada Filed Feb. 15, 1965, Ser. No. 432,805 6 Claims. (Cl. 25326) This invention relates to rotating hydraulic machines such as turbines, and pump/ turbines, which are characterized by having a shrouded runner and in which provision is made to aerate the spaces between the runner and the stationary members of the machine during normal operations of the machine and has particularly reference to the provision of new and improved means for automatically limiting overspeed of such machines.

In the past, hydro-dynamic brakes have been incorporated in rotating hydraulic machines to absorb some of the excess energy produced it the machines start running away and thereby reduce the upper limit of the runaway speed. One example of a brake used in this manner is described in British Patent 215,413 of Edward Charles Robert Marks, dated May 8, 1924 in which the rotating and stationary elements of the brake are mounted on and around the turbine shaft. The major disadvantages associated with the device as covered by the above patent are (1) it, adds to the initial costs of the turbine, and (2) involves additional installation costs in that the brake requires a special chamber in the powerhouse to accommodate it.

An object of the present invention is to provide new and improved means for automatically limiting the overspeed of rotating hydraulic machines incorporating aerated shrouded runners, in order that economic advantages can be taken of lower permissible design stress in the turbine and the associated electrical equipment. These improved means incorporate a hydro-dynamic brake without the disadvantages noted above.

According to the invention, in a hydraulic machine including a stator, a shaft, a shrouded runner secured to the shaft, and seals between the runner and the stator, an annular chamber between the crown of the runner and the stator, and an annular chamber between the band of the runner and the stator, said annular chambers being located on the high pressure side of their corresponding seal-s, means for aerating at least one of said annular chambers during operation of the machine, I have provided braking means in at least one of saidacrated chambers which braking means comprise a plurality of oppositely aligned pockets formed in the stator and the runner within the confines of said chamber, and control means responsive to increased speed of rotation of the escape of air from the pockets whereby working fluid is admitted to the pockets to provide a braking force on the runner.

In the execution of this invention it is important to note that the brake does not operate until after the aerated shrouds are de-aerated.

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, without departing from the spirit of the invention as the preferred form of the invention has been given by way of illustration only.

Referring to the drawings:

FIG. 1 is a fragmentary radial vertical section of a high head mixed flow turbine incorporating the preferred execution of the invention and;

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FIG. 2 is a plan view taken on line 2-2 of FIG. 1, looking in the direction of the arrows.

Although the invention is herein shown and described as applied to the crown shroud of a turbine, it will be understood that the application of said invention is not so limited; but that it is also applicable to the band shroud or to both band and crown shrouds together. It.

shroud or crown 1 and a lower runner shroud or band 2 connecting a plurality of blades 3 to each other and to a shaft 4. Members 1, 2 and 3 combine to form a runner 32 which rotates with shaft 4. The crown 1 and the band 2 are each bounded by a high pressure edge and low pressure edge, said high pressure edge being at a larger radius from the :axis of rotation than said low pressure edge. During the operation of the turbine, water is supplied under pressure to the runner 32 from a distributor 5 which extends around the stator 33 and is then discharged into a draft tube 6. It will be understood that when this machine operates as a pump, shaft 4 is rotated by an external source of power and the water flow is in the reverse direction.

Running clearances 13 and 14 are provided between the stator 33 and the high pressure edges of the crown and band of the runner 32. A seal 8 is provided adjacent to the low pressure edge of the band 2 and a seal 7 is located intermediate the ends of the crown 1 at substantially the same radius from the shaft as seal 8. An annular chamber 10 is provided adjacent to the high pressure end of the runner, between the stator 33 and the crown 1. An annular chamber 11 is likewise provided adjacent the high pressure end of the stator 33 and the band 2. The annular chambers 10 and 11 are in direct communication with the clearances 13 and 14 respectively. The seals 7 and 8 are of a type suitable to retain air in the shroud chambers 10 and 11. Air pipes 36) and 31 feed air into the chambers 10 and 11 respectively. It will be understood however that both of the chambers 10 and 11 need not be aerated in order to employ my invention. My invention may be employed at either or both chambers 10 and 11 depending upon which chambers are aerated.

In the drawings, annular chamber 10 is shown adapted to accommodate a hydro-dynamic brake of a type which is well known in the art. The portion of the static member 33 which forms part of the periphery of the annular chamber 10 is provided with a set of transverse ribs spaced around the annular chamber to form a series of pockets 15. These ribs are not illustrated but are the same as the set of ribs 16a provided in the crown 1 (FIG. 2) which form a series of pockets 16. These two series of pockets 15 and 16 cooperate together, and act as the hydro-dynamic brake when water is introduced therein. A sufficient clearance 34, is provided between aligned ribs 16a in the crown and the ribs in the stator to permit the air from supply pipe 30 to circulate freely throughout the pockets 15 and 16 and also to permit the flow of water either into or out of said pockets through clearance 13.

Although the hydraulic brake is illustrated and de-' When the above described braking device is used in conjunction with the annular chamber 10 or annular chamber 11, a source of air under pressure is introduced by pipe 30 as shown in FIG. 1, and is tapped into a second pipe 25. An air discharge valve 24 such as a solenoid operated valve, is connected in air pipe 25, in parallel with the air supply to chamber 10 and terminates in an exit or escape pipe 26. Pipes 25 and 26 are of greater diameter than the air inlet pipe 30 in order to carry away air introduced through pipe 30 as well as air discharging from chamber 10 when discharge valve 24 is opened. The air discharge valve 24 is connected by electrical conductor leads 23 to a source of electrical energy 27 and an electrical switch 22. Switch 22 may be actuated by a speed sensing device, for example, a runner driven governor 19 by means of a movable slide plate 20 and a bell crank 21.

The operation of the turbine employing my invention is as follows: with the hydraulic machine at rest, chambers 10 and 11 contain water, which will rotate in the chambers upon rotation of the runner. However, when the machine is started up and the runner rotates, air is introduced into either one or both of the chambers 1:1 and 11. Centrifugal force acts upon the contents of the chambers, and the water which is denser than the air, is thrown outwards from the shaft axis towards clearances 13 and 14, and the chambers 10 and 11 are refilled with air in the manner described in co-pending United States patent application Serial No. 201,881, Sproule and Boyd filed on June 12, 1962 and assigned to the same assignee as the present application. Ideally, all the water in the chambers 10 and 11 is replaced by air. If for any reason the machine speed exceeds the predetermined normal operating speed, said predetermined speed being higher than normal speed but substantially lower than runaway speed, slide 20 on speed sensing device 19 will move linearly upwards thereby causing bell crank 21 to operate the switch 22 and in so doing will open the air discharge valve 24. When air discharge valve 24 is open, air from the crown chamber 10 is released through pipes 25 and 26 and water from distributor by way of clearance 13 replaces the released air in chamber 10, and in so doing fills the stator pockets 15 and the runner pockets 16. The entry of water into pockets 15 and 16 increases the friction between the runner crown and the static member 33 to such an extent so as to produce a braking action on the runner 32. It should be noted that the overspeed reached by the turbine is in an inverse ratio to the braking capacity of the brake but in all cases is less than runaway speed without the brake being in operation.

When the machine has again resumed normal operating speed, speed sensing device 19 will linearly move slide 20 downwardly, thereby moving bell crank 21 away from the solenoid operated switch 22. This action closes the air discharge valve 24 so that air is once more admitted to chamber 10. The water in pockets 15 and 16 is driven out through clearance 13, as a result of the centrifugal action thereon and is replaced by air as described in the above mentioned pending US. application.

As explained previously, braking pockets may also be provided in the band chamber 11, in which case a separate air discharge valve and air discharge pipe would be connected with the air inlet pipe 31.

It will be readily understood that when a fabricated runner is employed in a hydraulic machine, the blade elements of the runner may be extended through the runner shroud into one or both of the aerated chambers to act as dividing ribs. The spaces between adjacent ribs may therefore be employed as pockets for the purpose described above. It will be obvious that these blade extensions must be in alignment with corresponding ribs provided on the static member and extending into the aerated chamber as explained previously and that a clearance 34 must be provided between the aligned blade extensions and ribs.

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

What I claim as new and desire to secure by Letters Patent of the United States is: p

1. In a rotary hydraulic machine, a stator, a shaft, a shrouded runner secured to the shaft comprising a crown and a band, and blades spaced between the crown and band, said crown and band each being bounded by a high pressure edge and a low pressure edge, said high pressure edges being at a larger radius from the axis of rotation than said low pressure edges, said high pressure edges and said low pressure edge of the band being positioned in cooperating relationship to said stator and dimensioned so as to provide running clearances between said edges and said stator, a crown seal and a band seal to provide sealing between the runner and the stator at points remote from said high pressure edges where said runner and stator are in close proximity, a first annular chamber extending between the crown seal and the high pressure edge of the crown and defined by the crown and the stator, a second annular chamber extending between the band seal and the high pressure edge of the band and defined by the band and the stator, means for aerating at least one of said annular chambers, braking means located in at least one of said aerated chambers comprising a plurality of oppositely aligned pockets formed in the stator and runner within the confines of said chamber, and control means responsive to increased speed of rotation of said runner beyond a predetermined level for permitting the escape of air from said pockets whereby working fluid is admitted to said pockets to provide a braking force on said runner.

2. In a rotary hydraulic machine, a stator, a shaft, a shrouded runner secured to the shaft comprising a crown and a band, and blades spaced between the crown and band, said crown and band each being bounded by a high pressure edge and a low pressure edge, said pressure edges being at a larger radius from the axis of rotation than said low pressure edges, said high pressure edges and said low pressure edge of the band being positioned in cooperating relationship to said stator and dimensioned so as to provide running clearances between said high pressure edges and said stator, a crown seal and a band seal to provide sealing between the runner and the stator at points remote from said high pressure edges where said runner and stator are in close proximity, a first annular chamber extending between the crown seal and the high pressure edge of the crown and defined by the crown and the stator, a second annular chamber extending between the band seal and the high pressure edge of the band and defined by the band and the stator, means for aerating at least one of said annular chambers, braking means located in at least one of said aerated chambers comprising a first set of spaced transverse ribs extending from the runner into said chamber to define a first series of pockets therebetween and a second set of spaced transverse ribs extending from the stator into said chamber to define a second series of pockets therebetween substantially aligned with said first series of pockets, said first and second sets of ribsbeing substantially in alignment with each other and terminating such that a clearance exists between said two sets of ribs whereby fiuid may fiow between adjacent pockets, and control means responsive to increased speed of rotation of said runner beyond a predetermined level for permitting the escape of air from said pockets whereby working fluid is admitted to said first and second series of pockets to provide a braking force on said runner.

3. In a rotary hydraulic machine, a stator, a shaft, a shrouded runner secured to the shaft comprising a crown and band, and blades spaced between the crown and band, said crown and band each being bounded by a high pressure edge and a low pressure edge, said'high pressure edges being at a larger radius from the axis of rotation than said low pressure edges, said high pressure edges and said low pressure edge of the band being positioned in cooperating relationship to said stator and dimensioned so as to provide running clearances between said high pressure edges and said stator, a crown seal and a band seal to provide sealing between the runner and the stator at points remote from said high pressure edges where said runner and stator are in close proximity, a first annular chamber extending between the crown seal and the high pressure edge of the crown and defined by the crown and the stator, a second annular chamber extending between the band seal and the high pressure edge of the band and defined by the band and the stator, means for aerating the annular chamber extending between the crown and the stator, braking means located in said annular chamber between the crown and the stator comprising a plurality of oppositely aligned pockets formed in the stator and runner within the confines of said chamber, and control means responsive to increased speed of rotation of said runner beyond a predetermined level for permitting the escape of air from said pockets whereby working fluid is admitted to said pockets to provide a braking force on said runner.

4. In a rotary hydraulic machine, a stator, a shaft, a shrouded runner secured to the shaft comprising a crown and a band, and blades spaced between the crown and band, said crown and band each being bounded by a high pressure edge and a low pressure edge, said high pressure edges being at a larger radius from the axis of rotation than said low pressure edges, said high pressure edges and said low pressure edge of the band being positioned in cooperating relationship to said stator and dimensioned so as to provide running clearances between said high pressure edges and said stator, a crown seal and a band seal to provide sealing between the runner and the stator at points remote from said high pressure edges where said runner and stator are in close proximity, a first annular chamber extending between the crown seal and the high pressure edge of the crown and defined by the crown and the stator, a second annular chamber extending between the band seal and the high pressure edge of the band and defined by the band and the stator, means for aerating the annular chamber extending between the crown and the stator, braking means located in said annular chamber between the crown and the stator comprising a first set of spaced transverse ribs extending from the runner into said chamber to define a first series of pockets therebetween and a second set of spaced transverse ribs extending from the stator into said chamber to define a second series of pockets therebetween substantially aligned with said first series of pockets, said first and second set of ribs being substantially in alignment with each other and terminating such that a clearance exists between said two sets of ribs whereby fluid may flow between adjacent pockets, and control means responsive to increased speed of rotation of said runner beyond a predetermined level for permitting the escape of air from said pockets whereby working fluid is admitted to said first and second series of pockets to provide a braking force on said runner.

5. In a rotary hydraulic machine, a stator, a shaft, a shrouded runner secured to the shaft comprising a crown and a band, and blades spaced between the crown and band, said crown and band each being bounded by a high pressure edge and a low pressure edge, said high pressure edges being at a larger radius from the axis of rotation than said low pressure edges, said high pressure edges and said low pressure edge of the band being positioned in cooperating relationship to said stator and dimensioned so as to provide running clearances between said high pressure edges and said stator, a crown seal and a band seal to provide sealing between the runner and the stator at points remote from said high pressure edges where said runner and stator are in close proximity, a first annular chamber extending between the crown seal and the high pressure edge of the crown and defined by the crown and the stator, a second annular chamber extending between the band seal and the high pressure edge of the band and defined by the band and the stator, means for aerating the annular chamber extending between the band and the stator, braking means located in said annular chamber between the band and the stator comprising a plurality of oppositely aligned pockets formed in the stator and runner within the confines of said chamber, and control means responsive to increased speed of rotation of said runner beyond a predetermined level for permitting the escape of air from said pockets whereby working fluid is admitted to said pockets to provide a braking force on said runner.

6. In a rotary hydraulic machine, a stator, a shaft, a shrouded runner secured to the shaft comprising a crown and a band, and blades spaced between the crown and band, said crown and band each being bounded by a high pressure edge and a low pressure edge, said high pressure edges being at a larger radius from the axis of rotation than said low pressure edges, said high pressure edges and said low pressure edge of the band being positioned in cooperating relationship to said stator and dimensioned so as to provide running clearances between said high pressure edges and said stator, a crown seal and a band seal to provide sealing between the runner and the stator at points remote from said high pressure edges where said runner and stator are in close proximity, a first annular chamber extending between the crown seal and the high pressure edge of the crown and defined by the crown and the stator, a second annular chamber extending between the band seal and the high pressure edge of the band and defined by the band and the stator, means for aerating the annular chamber extending between the band and the stator, braking means located in said annular chamber between the band and the stator comprising a first set of spaced transverse ribs extending from the runner into said chamber to define a first series of pockets therebetween and a second set of spaced transverse ribs extending from the stator into said chamber to define a second series of pockets therebetween substantially aligned with said first series of pockets, said first and second set of ribs being substantially in alignment with each other and terminating such that a clearance exists between said two sets of ribs whereby fluid may flow between adjacent pockets, and control means responsive to increased speed of rotation of said runner beyond a predetermined level for permitting the escape of air from said pockets whereby working fluid is admitted to said first and second series of pockets to provide a braking force on said runner.

References Cited by the Examiner UNITED STATES PATENTS 3,174,719 3/ 1965 Sproule et al. 253--26 FOREIGN PATENTS 928,588 6/ 1947 France. 691,148 8/1937 Germany. 714,290 11/ 1941 Germany. 867,933 3/ 1953 Germany. 934,106 8/1963 Great Britain.

SAMUEL LEVINE, Primary Examiner. E. A. POWELL, .lR., Assistant Examiner,

Claims (1)

1. IN A ROTARY HYDRAULIC MACHINE, A STATOR, A SHAFT, A SHROUDED RUNNER SECURED TO THE SHAFT COMPRISING A CROWN AND A BAND, AND BLADES SPACED BETWEEN THE CROWN AND BAND, SAID CROWN AND BAND EACH BEING BOUNDED BY A HIGH PRESSURE EDGE AND A LOW PRESSURE EDGE, SAID HIGH PRESSURE EDGES BEING AT A LARGER RADIUS FROM THE AXIS OF ROTATION THAN SAID LOW PRESSURE EDGES, SAID HIGH PRESSURE EDGES AND SAID LOW PRESSURE EDGE OF THE BAND BEING POSITIONED IN COOPERATING RELATIONSHIP TO SAID STATOR AND DIMENSIONED SO AS TO PROVIDE RUNNING CLEARANCES BETWEEN SAID EDGES AND SAID STATOR, A CROWN SEAL AND A BAND SEAL TO PROVIDE SEALING BETWEEN THE RUNNER AND THE STATOR AT POINTS REMOTE FROM SAID HIGH PRESSURE EDGES WHERE SAID RUNNER AND STATOR ARE IN CLOSE PROXIMITY, A FIRST ANNULAR CHAMBER EXTENDING BETWEEN THE CROWN SEAL AND THE HIGH PRESSURE EDGE OF THE CROWN AND DEFINED BY THE CROWN AND THE STATOR, A SECOND ANNULAR CHAMBER EXTENDING BETWEEN THE BAND SEAL AND THE HIGH PRESSURE EDGE OF THE BAND AND DEFINED BY THE BAND AND THE STATOR, MEANS FOR AERATING AT LEAST ONE OF SAID ANNULAR CHAMBERS, BRAKING MEANS LOCATED IN AT LEAST ONE OF SAID AERATED CHAMBERS COMPRISING A PLURALITY OF OPPOSITELY ALIGNED POCKETS FORMED IN THE STATOR AND RUNNER WITHIN THE CONFINES OF SAID CHAMBER, AND CONTROL MEANS RESPONSIVE TO INCREASED SPEED OF ROTATION OF SAID RUNNER BEYOND A PREDETERMINED LEVEL FOR PERMITTING THE ESCAPE OF AIR FROM SAID POCKETS WHEREBY WORKING FLUID IS ADMITTED TO SAID POCKETS TO PROVIDE A BRAKING FORCE ON SAID RUNNER.

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