US1777461A - Turbine-control mechanism - Google Patents

Description

()t. 7, 1930. c. B. CAMPBELL 1,777,461

lfI'URB'INEL CONTROL MECHANISM Filed April 18, 1929 INVENTOR (I. B- CAMPBELL. BY

ATTORNEY Patented Oct. 7, 1930 UNITED STATES PA ENT OFFICE CLABENGEB. CAMPBELL, or moonns, rnNNsYnvANIA, AssIeNon'ro WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A conPonATIo on PENNSYLVANIA zrnmarNn-eo rnon MncHANIsM Application filed April 18,

My 'invention-relatesto acontrolmecha ni'sm, more particularly to a" control mechanism for an elastic fluid turbine having means atan intermediate stage for either extracting-partially expanded motive fluid or for admitting low-pressure motive fluid thereto, and'it has for its object to provide means for compensating the admission of high-pressure motive fluid to the turbine in accordance with the amount of partially expanded motive fluid extractedor the amount or low prjess'ure motive fluidadmitted, Control mechanisms for extraction turbines have heretofore been built wherein a 15 speed-responsive governonis provided for controllingi the admisslonof motive fluid to the turbine and wherein the action of the speed-responslve' governor is modified or compensated in response to an operating condition or Variable which varies with the amount of partially expanded motivefluid extracted fromthe turbine. Such compensating means have heretofore been designed, so far as I am aware, upon the premise that the amount of inotivefluid extracted is a function of the pressure within the turbine at the point where itis extracted, or upon the premise that the amount of motivefiuid varies with the pressure diflere'ncesin the extraction conduit. While such control devices modify theaction or the governor in a satis factory manner fora portion of the range of extraction demands, they are usually inaccurate over the remaining portion of the range. 7 My invention, while compensating for the variations in amount of extracted fluid,is based upon the premise that the powe'rfdeveloped by the low-pressure section is added the admission of motive fluid tothe highpressure section should, therefore, be decreased in proportion tothe amount of power developed by the low-pressure section. To accomplish this, Iutiliz'e the pressure at the inlet or high-pressure end of the low-pres sure section, inasmuch as this pressure is substantially proportional to the power developed by the low-pressure section; or, as commonly expressed in the art, it; is a straight line function thereof; In this 1929. Serial No. 356,177.

invention, as willbe apparent from the following description and claims taken in connection with the accompanying drawings, forming pa'rtof this application, in which: The single figure is a diagrammatic view of my improved controlmechanism ap'pliedto an elastic fluid turbine; s t

Referringto the drawing more indetail, I show an elastic fluid turbineindicated generally at 10, for driving any driven machine (not shown), and including a high-pressure section 11; and a low-pressure section 12. A

diaphragm 13 or other suitable means is provided for separating thehigh-pressure and low-pr ssure sections, and suitablevalve controlled means is provlded for conveying partially expanded motive fluid from the highpressure sectionto the low-pressure section,

'suchas a by-pass conduit j14; having a valve 15ldisposed therein; A fconduit16 also communicateswith the discharge or low-pressure end of thehigh pressure section, as at the opening 17, through which partially expanded motive fluid is conveyed to the apparatus in which it isddesir ed to be used.

The amountof fluid extracted through the conduit 16 may be controlled, inanysuitable manner to supply the demand for the same, for example, thevalve 15 maybe actuated by 'aipis'ton 18 The piston 18 isdisposedin a cylinder 19' and biased in a direction for closing the valve 15 by a spring 20. It is biased in opening direction by the fluid pressure in the conduit 16, communicated thereto A throng-h a conduit 21. to that of the high-pressure section and that As, will be readily apparent, upon an increasein' demand for extraction fluid,the

pressure in the conduit 16 decreases, whereupon the spring 20 moves the'piston 18 and in the conduit 16 increases, actuating the piston 18 in the directionfor opening the valve 15 and conveying a greater amount of fluid to the low prcssure $661510;

High-pressure motive fluid is admitted to the turbine, that is, to the high-pressure or inlet end of the high-pressure section 11, through an admission valve 22, controlled by any suitable governor, preferably a speedresponsive governor. I show, for-example,-a fluid pressure governor including a centrifugal pump 23 operated directly by the rotor 24 providing a fluid pressure varying as a functionof-the speed of th'e'prime mover. A

piston -25 i s-connected to'the valve 22 for operating the same and is disposed in a cylinder 26. A spring 27 biases thepiston 25in the direction for opening the .valve ,13 and the fluid pressure developed bythepump 24 is conveyed through a conduit-28 to the cylinder 26 to bias the piston 25 in closing direction. 1

The operation of this, form of fluid pressure governor -will be readily understood. Upon increase in speed of the prime'mover, fluid pressure developed by the pump 23 increases and moves'the piston 25 in the direction for decreasing the opening of the admission valve 22. Upon decrease in speed, the fluid pressure is decreased and the spring 27 moves the piston 25 'toprovide increased opening of the valve 22.'- v

The apparatus so far described is known in the art and in order to compensate the speed-responsive governor, I impose a back pressure on the piston 25. Thepiston 25fis provided with a restricted orifice 29through which a small amount of fluid flows for providing the fluid pressure. A pressure relief valve 30 controls said back pressure through a passage, 31. The valve 30 is biased to closed position by a: spring 32 interposed between the valve and a spring abutment 33 movable by a lever 34. The lever 34 is pivoted to a stationary fulcrum at 35 and is actuated by a diaphragm 36. A conduitx37 vcommuni cates the pressure at the inlet or-high-pressureend of the low-pressure section 12 to the chamber 38 provided on .the lower-sideof the diaphragm 36rfor controlling the movements of the lever. 34. A spring 39'biases the lever 34in opposition to. the force of the dia- My novel controlmechanism operates in the following manneri Upon an increase in thedemand for extraction fluid, the valve 15 is moved in-closing directiomand'admits a decreased amount of fluid to the low-pressure section,resulting-in a decrease, in power developed by said section.- The 'decreasein admission of motive fluid tothe low-pressure section also results in a decrease in pressure in the high-pressure or inlet end thereof, proportional to the decrease in power, which reduced pressure is communicated to the diaphragm 36 and results in downward movement of the lever 34.

The downward movement of the lever 34 provides increased pressure of the spring 32 and an increase in the back pressure on the piston 25. Hence the piston 25 moves the valve 22 in opening direction to provide increased admission of motive fluid to the high-pressure section to compensate for the decrease in power developed by the low-pressure section.

Upon a decrease in demand for extraction fluid, the valve 15 is moved in opening direction as above described and increases the flow of-fluid to the low-pressure section; -An-increased pressure 'is thus communicated through the conduit 37 to the diaphragm 36, and an upward movement of the lever 34 is effected. ;The compression of the spring 32 is decreasedand the relief valve 30 effects a decreased back pressure on the piston 25. The piston 25 is thereupon moved in-the direction for moving the admission valve 13 in closing direction to decrease the admission of motivefluid to the high pressure section to compensate for the increase of power de-' veloped by the low pressure section.

- The advantage of my novel control or compensating mechanism is that the pressure in the low-pressure section is substantially essary motive fluid' admission.

While I have described the turbine as discharging fluid through the opening 17 it will be apparent that low-pressure motive fluid may be admitted therethrough. The control mechanism operates in exactly the same manner'as described above, an increase in pressure and power of the low pressure section resulting in a decreased admission to the high-pressure sectionjand vice versa.

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 theappended claims.

What I claim is:

1. In a control mechanism, the combination with a prime mover having .a highpressure section, a low-pressure section and an opening communicating with the discharge end of the high-pressure section, of a control mechanism therefor comprising means responsive to the speed of the prime mover for controlling the admission of motive fluid to the high-pressure section, means 7 for controlling the distribution of partially expanded motive fluid discharged from the high-pressure section between the low-pressure section and said opening in response to an operating condition, and means responsive to the pressure at the inlet end of the low-pressure section for modifying the action of the speed-responsive means.

2. The combination with a prime mover having a high-pressure section, a low-pressure section, and an opening providing communication between the exterior of the turbine and the interior of the prime mover at the discharge endof the high pressure section, a valve controlling communication between the high-pressure and low-pressure sections, means responsive to an operating condition of the prime mover for controlling the admission of motive fluid thereto, and means responsive to the pressure in the inlet end of the low-pressure section for modify ing the action of the means controlling the admission of motive fluid to the prime mover. V

3. In combination, an elastic fluid multistage turbine, said turbine having a diaphragm between two successive pressure stages thereof and an extraction opening before the diaphragm in the direction of mo tive fluid flow, means for controlling the dis tribution of fluid between the extraction opening and the pressure stage beyond the diaphragm, means responsive to the speed of the turbine for controlling the admission valve, and means responsive to the pres sure of fluid within the turbine immediately beyond the diaphragm for modifying the action of the speed-responsive means.

4. The combination with a prime mover having a high-pressure section, a low-pressure section, and an opening providing communication between the exterior of the turbine and the interior of the prime mover at the discharge end of the high-pressure section, means responsive to an operating condition of the prime mover for controlling the admission of motive fluid thereto, and means responsive to the pressure in the in let end of the low-pressure section for modifying the action of the means controlling the admission of motive fluid to the prime mover.

5. The combination with a prime mover having a high-pressure section, a low-pres sure section, and an opening providing communication between the exterior of the turbine and the interior of the prime mover at the discharge end of the high-pressure section, means responsive to an operating condition of the prime mover for controlling the admission of motive fluid thereto, and means responsive to the variable pressure of the motive fluid in the low-pressure section for modifying the action of the means controlling the admission of motive fluid to the prime mover. V

In testimony whereof, I have hereunto subscribed my name this 12th day of April,

CLARENCE B. CAMPBELL.

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