US1845905A

US1845905A - Governing mechanism

Info

Publication number: US1845905A
Application number: US296837A
Authority: US
Inventors: Ozro N Bryant
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1928-08-01
Filing date: 1928-08-01
Publication date: 1932-02-16
Anticipated expiration: 1949-02-16

Description

Feb. 16, 1932. o, N, BRYANT 1,845,905

GOVERNING MECHANI SM Filed Aug. l, 1928 NLA y i `lz WITNESSES: INVENTOR ATTORNEY Patented Feb. 16, 1932 UNITED STATES PATENT OFFICE OZRO N. BRYANT, OF MOOBES, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE EDEC- TRIC & MANUFACTURING COMPANY,

A CORPORATION F PENNSYLVANIA GOVERNING MECHANISM Application illed August 1, 1928. Serial No. 296,837.

,5i forth.

In an extraction or mixed-pressure turbine, the :flow of fluid at the point of extraction or induction is controlled in response to there quirements of partially expanded motive m fluid or the supply of low pressure motive fluid. The variation in extracted o1' inducted motive fluid varies the power output of the turbine, and, unless provision is made for compensating the admission governor, the speed must vary until the admission valve is adj usted to admit the proper amount of high pressure motive fluid. j

In accordance with my invention, I provide a fluid pressure relay for actuating the valve controlling the amount of extracted or in duct-ed motive fluid. The setting of the admission valve governor is varied by the position of the operating piston of the relay to compensate for the amount of extracted or` inducted motive fluid.

The mechanism for varying the setting of the governor includes a column of liquid, preferably mercury, the head of which is varied by displacement of liquid.

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

The single figure is a diagrammatic view of the novel governing system, parts thereof being shown in elevation and section.

Referring now to the drawing more in detail, I show an elastic fluid turbine 10, for example, a steam turbine, driving an electrical generator 20 and having a high pressure section 8, a low pressure section 9, an admission valve 11 for admitting steam to the high pressure section, a conduit 12 communicating with the turbine intermediate the high and low pressure sections thereof, and an interstage grid valve 13 located beyond the conduit 12 and controlling the flow of steam to the lower pressure section. Steam may be extracted from the turbine through the conduit 12 or low pressure steam of the pressure corresponding to this point of the turbine may be admitted through the conduit 12.

The governing system includes an impeller 14, mounted directly on the shaft 15 of the turbine, providing a fluid ressure varying as the square of the speed o the turbine. The admission valve 11 is actuated by a piston 16, disposed in a cylinder 17 and connected thereto through a lever 18 pivoted to a stationary fulcrum at 19. The piston is biased downwardly in valve-opening direction by a spring 21, and upwardly in valve-closing direction by the fluid pressure developed by the impeller 14, which is conveyed to the lower end of the cylinder 17 through a conduit 22.

The governing apparatus so far described constitutes a simple form of fluid pressure governor, the operation of which is well known and will be readily understood. As the speed of the turbine increases, the fluid pressure developed by the impeller 14 increases and moves the piston 16 in valve-closing direction against the force of the spring 21. Upon decrease in speed, the fluid pressure decreases, permitting the spring 21 to move the piston a corresponding amount in valve-opening direction.

In order to vary the setting of the governor just described, I impose a variable back pressure on the upper side of the piston 16 in Opf position to the im eller pressure. This fluid pressure is provi ed by a restricted flow of fluid through an orifice 23 in the piston 16 into an enclosed space consisting of the upper end of the cylinder 17, a conduit 24 communieating therewith, and the space below a back pressure or krelief valve 25. The latter con trols the escape of fluid from the enclosed space and thus controls the back pressure on the piston 16 and the setting of the governor.

The valve 25 is disposed in a casing 26 and connected to a diaphragm 27 secured therein. The casing 26 is provided with a tubular extension 28 projecting upwardly therefrom, and in the space above the diaphragm 27 and in the tubular part 28, I provide a liquid, preferably mercury, which has a high specie gravity. The liquid acts on the diaphragm 27 to bias the valve 25 downwardly to closed position, with a pressure proportional to the head of the liquid. Projecting downwardly within the tubular extension and below the level of the liquid is a rod or plunger 29, which is movable vertically to displace liquid and thereby to vary the head thereof.

The plunger 29 is moved in accordance with the position of the interstage valve 13, which is operated by a mechanism indicated generally by the numeral 31. This mechanism inV cludes an operating piston 32 connected to the interstage grid valve 13 by a piston rod 33, a cylinder 34 for the piston 32, a pilot valve 35 and a casing 36 for the pilot valve. The valve 13 is so arranged as to provide decreased opening upon downward movement of the piston 32 and increased opening upon upward movement thereof. The plunger 29 is'rigidly attached to the piston rod 33 and bodily movable therewith, Theplunger is thus moved in accordance with the opening of the interstagevalve 13.

The pilot valve casing 36 is provided with

ports

37 and 38, communicating'withthe upper and lowerends of the cylinder 34 and normally covered by piston portions 39 and 41, respectively, formed on the pilot valve 35. The casing 36 is further provided with a port 42 between the piston portions, for admitting motiveuid for operating the piston 34, and with discharge ports 43 and 44 beyond the piston portions. n

The relay 31 also includes a floating lever 45', pivotedfat one endto the piston rod 33, asindicated at 46, and intermediate its ends tothe pilot valve 35, as indicated at 47. The other end 48 of the lever controls the relay.

Upon upward movement of the end 48 of the lever, the latter first moves about the pivot 46, raising, the pilot valve 35. The port 37 is thus placed in communication with the inlet port 42 and the port 38 is placed in communication with the discharge port 44. The fluid pressure, therefore, moves the piston 32 downwardly, until the pilot valve, which isA moved downwardly at the same time through the lever-45, cuts off the

ports

37 and 38, at which time the point 47 will be returned to its original position. `Upon downward movevment, of the lever end 48, the

ports

37 and 38 are placed in communication with the exhaust port 43 andthe inlet port 42, respectively, and the piston 32 moves upwardly until the point 47 is returned to its original position.

In considering the operation of the fluid pressure relay 31, therefore, the lever 45 may be considered as movable about a stationary pivot at 47, the relay merely supplying power to eect the movement of the pivoted end 46.

The relay 31 is controlled by a diaphragm 49, connected by a stem 51 to the end 48, of

the floating lever 45. The diaphragm is biased downwardly by the pressure in the conduit 12 communicated thereto through ay conduit 52, and upwardly, in' opposition to said pressure, by a spring acting on the stem 51.

In view of the fact that the position of the interstage valve varies with changes in load as well as change in extraction demand, I may provide means for compensating for the variations in load, in order that the back pressure imposed on the upper side of the governor pis- Yton 16 may be substantially a function of the steam extracted or inducted through the conduit 12 only.

To this end, I may provide a diaphragm 53, communicating with the space above the diaphragm 27 through a conduit 54, and adapted to move liquid into or out of said space to vary` the head thereof. rThe diaphragm is connected through a stem.55 to a core 56 of the watt meter device 57. The latter includes a solenoid 58, connected to and energized by the leads 59 of the generator 20, and moving the core 56 and the diaphragm 53 downwardly in accordance with the load carried by the generator. The action of the watt meter device may be Vadjusted by a rheostat 61.

The operation of the above-described embodiment of my invention is as follows Assume that the turbine is being operated as an extraction turbine and that the demand for partially expanded steam increases, causingV the pressure in the conduit 12 to decrease. The decrease in pressure on the diaphragm 49 permits the spring 60 to move the stem 51 and the end 48 of the lever 45 upwardly. The pilot valve 35l is moved upwardly, at the same time, by the lever 45, admitting fiuid pressure tothe upper end of the cylinder 34 and permitting discharge of fluid from the lower end thereof. The piston 32 is moved downwardly and lowers the pivoted end 46 of the lever 45 until the pivot point 47 is restored to normal position, when the pilot valve cuts off further flow of fluid to or from the cylinder 34. The downward movement of the piston 32 effects closing movement of the interstage valve 13, thereby holding back more steam from the low pressure section to supply theconduit 12.l

The power developed by the low pressure section 9 is decreased accordingly.

The plunger 29 is moved downwardly with the piston rod 33, and displaces a quantity of liquid in the tube 28, causing the level thereof to rise. The pressure of the liquid acting on the diaphragm 27 to bias the valve 25 to closed position increases with the increase in head, resulting in increased back pressure on the upper side of the governor' piston 16. The increased back pressure effects a corresponding downward movement of the piston 16 and opening movement of the admission valve 11. The admission of steam to the high pressure section is thus increased, and the decrease in powerdeveloped by the low pressure section is compensated by the increase in power developed bythe high pressure section.

Upon a decrease in demand for partially expanded steam, the ressurc in the conduit 12 increases. The flui pressure relay 31 thereupon `effects an opening movement of the interstage valve 13 to increase the flow to the low pressure section and to decrease the amount of steam held back for the conduit 12. The power developed by the low pressure section is thus increased.

The upward movement of the plunger 29, during this operation, causes the level of the liquid in the tube 28 to fall, and the decreased head on the diaphragm 27 effects a decreased back pressure on the upper side of the governor piston 16. The latter thereupon effects decreased opening of the admission valve 11. The power developed by the high pressure section is thus decreased to correspond to the increase of the low pressure section.

Assume, now, that the extraction demand remains constant and that there is a decrease in electrical load on the generator 20, result ing in increased speed of the generator and turbine. The piston 16 thereupon moves in response to the increase in impeller pressure to decrease the admission of steam to the high pressure section 8. The decrease in flow through the high pressure section results in decrease of pressure in the conduit 12, and the interstage valve 13 is thereupon operated to decrease its opening in the manner de` scribed above.

In the operation just described, the plunger 29 moves downwardly and displaces a quantity of liquid in the tubular extension 28. This displacement, however, is compensated by the diaphragm 53. Upon the decrease in load on the generator, the watt meter device 57 exerts a decreased downward bias on the diaphragm 53, permitting the same to move upwardly. The quantity of fluid displaced by the plunger 29 thus fiows through the conduit 54 to the chamber below the diaphragm 53. The head of the liquid in the tube 28 and the back pressure on the governor piston 16 are thus substantially unaffected, and each remains substantially a correct function of the amount of extracted fluid.

Upon an increase in electrical load, the mechanisms operate in the reverse direction in exactly the same manner, as will be readily apparent.

The above described apparatus may also be used as a mixed pressure turbine where a supply of low pressure steam is available.

' In such case, the low pressure steam is admitted through the conduit 12. As the supply of such steam increases, the pressure thereof increases, and the interstage valve 13 is opened further to permit increased flow thereof to the low pressure section 9. At the same time, the back pressure on the piston 16 decreases and the admission to the high pressure section 8 is decreased to compensate for the increase in flow in the low pressure section.

Upon 4a decrease in the supply of the low pressure steam, the reverse operation takes place, as will again be apparent.

From the above description, it will be apparent that I have provided a novel governing system wherein the governor controlling the admission valve is compensated for the variations in power developed by the low pressure section.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is 1. In a regulating mechanism, a chamber containing a body of liquid, one wall of said chamber being a pressure-responsive element which is responsive to the pressure of the liquid generated by the action of gravity on the head of the liquid above the pressure-` responsive element, means controlled by the pressure-responsive element for effecting a regulating action, and a plunger movable into said body of liquid to vary said pressure by varying the level of the liquid in the chamber. i

2. The combination of a relief or back pressure valve, a chamber containing a column of liquid, one wall of the chamber being a pressure-responsive element, said element being responsive to thepressure of the liquid produced by the action of gravity on the liquid above the pressure-responsive element, means for applying the pressure exerted on the pressureresponsive element to said back pressure valve, and a plunger movable vertically in said column of liquid to vary said fluid pressure by varying the level of the liquid.

3. The combination with a prime mover having a speed' governor, of a pressure-responsive element to vary the setting of the governor, means for applying the head of a bodyv of liquid to said pressure-responsive element, a plunger movable vertically in said column of liquid to vary the head thereof, and means to move said plunger vertically in accordance with an operating condition of said prime mover.

4. The combination `with a prime mover having an admission valve, of a governing system therefor comprising means providing a fluid pressure varying with the speed of the primemover, means providing an enclosed space, means providing a restricted flow of fluid into .said space, a relief 6r bacli pressure valve controlling the escape of fluid from said space, means providing a column of liquid, a plunger movable vertically into said column lto vary the head thereof in responseto an operating condition of the prime mover, means for applying the head of said column to said relief or back pressure valve, and means responsive to the first-mentioned fluid pressure and to the fluid pressure in said space for controlling said admission valve.

5. A governing system for a bleeder or mixed pressure turbine having an admission valve, a bleeder or induction opening, and an interstage valve, comprising a governor responsive to speed of the turbine and controlling the admission valve, means including a pressure-responsive element for varying the setting of the governor, means including a fluid pressure relay for actuating the int-crstage valve to control the flow of iuid therethrough, means for providing a colmnn of liquid and for applying the head thereof to the pressure-responsive element, and means for varying said head by the relay in accordance With the position of the interstage valve.

6. A governing system fora bleeder or mixed pressure turbine having an admission valve, a bleeder or induction opening, and an interstage valve, comprising a governor responsive to speed of the turbine and controlling the admission valve, means including a pressure-responsive element for Varying the setting of the governor, means for actuating the interstage valve to control the flow of iuid therethrough, means for providing a column of liquid and for applying the head thereof to the pressure-responsive element, and a plunger actuated by the means for actuatingtheinterstage valve and movable vertically in said column of liquid.

7. The combination with an'elastic fluid turbine having an admission valve and a secondv valve controlling the flow of fluid at an intermediate point in the turbine, of a governing system therefor comprising a governor responsive to the speed of the turbine and controlling the admission valve, a fluid pressure relay including an operating piston for operating the said second valve, means controlling said relay in accordance With an operating condition of the turbine, and means responsive to the position of the operating piston for varying the setting of the governor.

8. The combination with an'elastic liuid turbine having an admission valve anda second valve controlling the flow of iiuid at an intermediate point in the turbine, of a governing system therefor comprising a governor responsive to the speed of the turbine -vand' controlling the admission valve, a fluid pressure relay including an operating piston for operating said second valve, means controlling said relay in accordance with an operating condition of the turbine, means providing a column of liquid, a plunger actuated by said operating piston and movable vertically intosaid column of liquid to vary the headthereof, and'means responsive to the head of said column of liquid for varying the setting ofthe governor.

9. The combination with an elastic uid turbine having an admission valve and a second valve controlling the flow ofvfluid aty an intermediate point in the turbine, of'a governing system therefor comprising means providing a Huid pressure varying with the speed of the prime mover, a fluid pressure relay including an operating piston for operating said second valve, means controlling said relay in accordance with an operating condition of the prime mover, means providing an enclosed space, means providing a restricted flow offluid into said space, means responsive to the position of said operating piston for controlling they escape of iuid Vfrom said space, and means responsive to the first-mentioned Huid pressure and to the fluid pressure in said enclosed space for controlling said admission valve.

l0. The combination with an elastic fluid turbine having an admission valve, means for extracting partially expanded motive fluid therefrom, and a valve controlling the iioW of fluid through the turbine at the point of extraction, of a governing system for; the turbine including means for regulating the admission valve in response to a characteristic of the extracted `fluid, speed-responsive means for regulating the admission valve, means for compensating the speed-responsive means in accordance with the position of the second-mentioned valve, and means for'compensating said compensating means in accordance with the load carried by the turbine.

In testimony whereof, I have hereunto'subscribed my name this 27th day of July, 1928.

- OZRO N. BRYANT.