US1875327A

US1875327A - Tttrbine control mechanism

Info

Publication number: US1875327A
Authority: US
Publication date: 1932-09-06
Anticipated expiration: 1949-09-06

Description

sfipt. 6, 1932. Q CAMPBELL 1&2532? TURBINE CONTROL MECHANISM Filed Aug. 30, 1950 VOL-M65 0540K an (6 ATTORNEY Patented Sept. 6, 1932 1 A E orrica criaanivcn B. CAMP-BELL, or Moonns, raivivsirtveurh, nssreuonazo swimmer: 1v

ntncrnio & MANUFACTURING CQMPANY, A conroan zrron or BENNSYLVANIA 'runnrun common MECHANiSM Application filed August 30, 1930. Serial No. 478,962.

My invention relates to a control mechanism for a prime mover, more particularly to a control mechanism for a multi-stage elastic fluid prime mover having an exhaust opening through. which partially expanded '10 admitting motive fluid to said stage.

The object of the invention is to provide an improved control mechanism ofthe character set forth. p

A more particular object is to provide, for

5' a prime mover of the character set forth having suitable valve means regulatingthe flow therethrough, an improved control mechanism which will, upon-change indemand for partially expanded fluid at either 3 opening, effect the. desired change in flow and maintain the desired pressure thereof, and simultaneously maintainthe desired flow and pressure of fluid at the other opening.

In accordance With my invention, I pr0 g5 vide one fluid pressure which" varies upon change in exhaustpressure anda swond fluid pressure which varies upon change in pressure at the intermediate pressure stage. I provide a third variable fluid pressure responsive to 3 the first and second fluid pressures. I also provide a regulating mechanism responsive to said third fluid pressure fo'rcontrolling the admission ofmotive fluid to the prime mover, and a regulating. mechanism .respon-.

.85 sive to saidfirstfluid pressurefor controlling the flow of fluid at the intermediate pressure sta e. I i

The above and. other objects are effected by my invention, as Will be apparent from the .40 following description and claims,"taken in connection With the accompanying drawing, forming a part of this application, in which: The single figure is a diagrammatic view of the control mechanism 'appliedto an elas- 45. tic fluid turbine. I r

Referring novvto the. drawing more in detail, I show an elastic fluid turbine -hav-,

ing a casing 11 and a rotor12. The turbine is supplied with motive fluid from any suit- 50 able source through a'conduit'13. The motively high pressure,

- It is conveyed through a conduit 34 to the tive fluid may beany suitable elastic fluid,

such as steam, and is preferably at a rel-afor example, 400 lbs. per square inch. 7 V I p The :motivefl-uid first fiowsthrough a high pressure section 15 to an intermediate pressure stage 16. A portion of the partially expanded motive fluidis extnactedfrom the turbine at the stage 16, an opening 17 communicating vvithan extraction conduit 18 being provided for this purpose. This fluid may be. at a pressure of 1 lbs. per square inch,for example, and is used for industrial or. heating purposes.

From the intermediate pressure stage 16, motive fluid passes to a low-pressure section 19through 'a passage 20 in which aninterstage valve 21 is interposed. In-the lowpressure section 19,'the motive fluid is still further but not completely expandethfor example, to a pressure of 8 lbs. per square inch, andIit then passes through the exhaust chamber 22 and the exhaust opening 23. to a. conduit 24;,from which it is suppliedtoany demand for'fluid of this pressure.

As the turbine does not completely expand the motive fluid, theadmission valve regulates the admission to the turbine in accordance with the demands for extracted and exhausted fluid. The interstage valve raga lates the flow to the low-pressure section 19 En accordance with the demand for exhausted The valves .14, and 21 are connected to fluid pressure governors 25 and 26, respectively. Each governorinciudes a cylinder 27, and a piston 28 operating therein, thelatter being connected to the associated valve through a lever 29 pivoted to. a stationary fulcrum at 30. A spring 21 biases the piston 28in valve-opening direction.

Fluid pressure varying as the square of the speed of the turbine is developed by an impeller 32 mounted on the rotor. shaft cylinder 27 "of each governor and imposed on.

the piston 28 in valve-closing direction and in opposition tothe spring 3 Inorder to control the action of the sev-- eral governors in accordance'withthe variton 28, of fluid under pressure delivered by impeller 32. It is controlled by regulating the escape of fluid from the upper end of the governor cylinder 27. I 7 The opposing fluid pressure applied to the governor 25 is controlled by a device, which may be termed a compensator, indicated at 36. The compensator 36, is in turn, controlled by regulators 37 and 38; the regulator 37 being associated with the intermediate pressure or extraction stage of the turbine and the regulator 38 bemg associated w th the exhaust stage. The opposing fluid pressurein the governor 26 is controlled by the regulator 38. r Y

The compensator 36 includes a pressure relief valve 39 communicating with the governor 25 through conduits 40 and 41. It

further includes pressure-responsive elements 42 and 43 whichbias the pressure relief valve inclosing direction, each element being connected thereto by a lever .44 bearing on a knife edge fulcrum 45. The fullcrum is mounted on a stationary supporting plate 46 and is secured thereto'by a screw 47 passing through a longitudinal slot 48 in the supportingiplate. The fulcrum may be moved longitudinally of the lever to vary the lever arm ratio. The regulator 37 includes a lever 49 bearing ona knifeedge fulcrum 50. A diaphragm 51 is connected to the lever 49, and is subjected to the pressure of the fluid in the conduit 18, which is communicated to the diaphragm through a conduit '52. A spring 53 biases the lever 49 in opposition to the fluid pressure on the diaphragm 51. An adjustment 54 for the spring is provided for varying the setting of the regulator.

.The regulator 37 further includes a pressure relief valve 55 biased to closed position by'a spring 56, the latter being a compression spring interposed between the relief valve and a-spring-holding-member 57 carried by thelever 49. The pressure relief valve 55 controls the escape of fluid from a conduit 58 which is supplied through an orifice 59 With a restricted flow of fluid under pressure from the conduit 34. The pressure in the conduit 58 is communicated by the conduit and applied to the pressure-responsive element 42 of the compensator 36. i

The regulator 38 is of the same construe tion as the regulator 37, and the corresponding parts thereof bear the same reference numerals with the prime mark added. The diaphragm 51 is subjected to the pressure in the exhaust conduit 24, communicated thereto through a conduit 60.

The pressure relief valve 55 of the regulator 38 controls the opposing fluid pressure in the governor 26, communication therebetween being provided by

conduits

61 and 62. The pressure controlled by the valve 55 is also communicated by the conduit 62 to the pressure-responsive element 43 and applied thereto. 7

The turbine drives a synchronous alternating current generator 63 which is e1ectrically connected with the line 64- of an electric power system. Leads 65 connect the generator 63 to a local bus 66, which in turn is connected to the line 64 through a connection 67. A switch 68 is interposed in the connection 67 and is operated by any suitable mechanism 69, such as a reverse current relay or a lowvoltage relay, or. preferably a compound reverse current low voltage relay.

A cut-out device 7 0 is adapted, upon opening of the switch 68, to discontinue the pressure regulation and to render the control mechanism operative to govern the turbine in response to speed only. The device includes a stationary structure 71 having a cylindrical bore 72 in which a valve. member 7 3 is disposed. The latter has a portion of re duced diameter at 74 which provides communication between the conduits 40 and 41 when the valve member is in its normal position shown on the drawing, and a second portion of reduced diameter at 7 5 which provides communication between the

conduits

61 and 62. The stationary structure of the cut-out device is formed with a passage 7 6 communicating with a constant pressure relief valve 7 7.

A spring 78 biases the valve member 73 upwardly, but it is normally held in the position shown on the drawing by a trigger 79. The trigger is actuated to unlatch the valve member 73 by the plunger of a solenoid 80, which is energized by a circuit 81. The latter includes a switch 82 which is closed Whenthe switch 68 is opened;

The operation of the above-described mechanism is as follows:

In normal operation, the speed of the unit, comprising the turbine 10 and the generator 63, is fixed by the frequency of the alternating current in the system, and the valve member 73 is in the position shown in the drawing, placingthe conduit 61 in communication with the conduit 62 and the conduit 40 in communication with the conduit 41.

Upon an increase in demand for extracted fluid in. the conduit 18, the pressure in the conduit 18 decreases, whereupon the spring 53 of the regulator 37 moves the lever 49 downwardly. The compression of the spring 56 is increased and the pressure relief valve '55.imposes' an increased pressure on the-fluid in the conduit 58. The pressureresponsive element 42 accordingly transmits an increased force through the lever 44 to the pressure relief valve 39, which in turn, imposes an increased pressure on the fluid in the upper end of the cylinder of the. governor 25.

The piston 28 of the governor 25 is movedv valve 55 provides decreased pressure in the conduit 58. Accordingly, a decreased force is transmitted from the pressure responsive element 42 to the pressure relief valve 39, and a decreased opposing fluid pressure is provided in the governor 25. The piston 28 moves upwardly to provide decreased opening of the admission valve 14.

Upon increase in demand for fluid in the exhaust conduit 24, the pressure therein decreases and the lever 49 of the regulator 38 is moved downwardly by the spring 53. The spring 56 is further compressed and imposes a greater closing force on the pressure relief valve 55'. The latter imposes a greater pressure on the fluid in the conduit 62 and above the piston 28 of the governor 26. The latter moves the interstage valve 21 in opening direction to provide increased admission to the low pressure section 19. The

.bine is now controlled solely in response to increased pressure transmitted through the conduit 62 to the pressure responsive element 43 causes an increased force to be transmitted through the lever 44 to the pressure relief valve 39. The latter increases the opposing fluid pressure in the governor 25, and causes increased opening of the admission valve 14.

Upon decrease in demand and increase of pressure of the fluid in the conduit 24, the opposing fluid pressure in the governor 26 and the pressure in the conduit 62 isdecreased. The governor 26 moves the interstage valve 21 in closing direction to decrease the flow to the low pressure section 19. The decreased opposing fluid pressure in the governor 25 effected by the pressure relief valve 89, causes the governor to move the admission valve 14 in closing direction.

By the above described control mechanism, therefore, the interstage valve 21 is regulated to admit that amount of partially expanded fluid to the low pressure section 19 which is required in the conduit 24, and the admission valve 14 is regulated to supply the fluid required by the conduit 24 and flowing through both sections of the turbine and the fluid required in the conduit 18 and flowing throughthehigh pressure section 15 onl o I fi rmally, the turbine and generator unit vdelivers to the system only so much power as. is produced by the-motive fluid flowing through the turbine to supply the demand for extracted and exhausted fluid. However, when the supply of power from the system fails and the switch 68 is opened, the

load connected with thelocal bus 66 must be;

carried by the unit comprising the turbine 10, and the generator 68, the speed of the unit is no longerfixed by the frequency in the system.

In thisevent, the circuit 81 is closed by the #3 switch 82 and energizes the solenoid 80. The plunger of the solenoid moves the trigger 79 out of engagement with the valve member 7 3 and the spring 7 8 moves the latter upwardly. The valve member 7 3 cuts off communication between the conduits 40 and 41, and places the conduit 40 in communication with the passage 7 6. The escape of fluid from the upper end of the cylinder of the governor 25 is controlled by the valve 9 77, which maintains a constant pressure therein.

The upward movement of the valve member 78 also cuts off escape of fluid from the conduit 61. The fluid in the upper end of the cylinder of the .governor 26 thereupon, attains the pressure in the lower end of the cylinder, and the piston 28 is moved downwardly by the spring 31 and brings the interstage valve 21 to full open position.

The admission of motive fluid to the turvalve-opening direction.

7 The opening of the interstage valve 21 permits maximum amount of fluid to flow to the low pressure section 19, in order that maximum power may be developed by the turbine.

7 When the admission is controlled in response to the speed only, the discrepancy between the amounts of partially expanded fluid required in the conduits 1 8 and 24 and that supplied by the turbine, is takencare of by means well known in the art.

It willbe apparent that the pressure within the region enclosed by an extraction pressure or exhaust pressure stage and the opening and extraction conduit communicating therewith is substantially the same, or at least varies similarly withchanges in demand, and that the pressure for controlling the associated pressure-responsive diaphragm may be taken at any point-within that region.

' 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. The combination with amulti-stage elastic fluid prnne'mover exhausting at a back pressure and havmg an opening providlng j communication between an intermediatepressure stagetherein and a region external to the Working passages of the prime mover, an admission valve for the prime mover, and a second valve controlling the flow of fluid at said opening, of a control mechanism there- 7 for comprising means providing a first fluid pressure varying in response to changes in pressure at said opening, means providing a second fluid pressure varying in response to changes in pressure of the exhaust fluid, means responsive to said first and second fluid pressures for providing a third fluid pressure, means responsive to the thirdfluid pressure for controlling said admission valve, and means responsive to the second fluid pressure for controlling said second valve.

2. The combination defined in'olaim 1 and further including means providing a fourth fluid pressure varying as a function of the speed of the prime mover, the means for controlling said admission and second valves being also responsive to said fourth fluid pressure.

3. The combination'with a multistage elasticfluid prime mover exhausting at a back pressure and having an extraction opening communicating 'Wltll an "intermediate-pres sure stage therein, an admission valve for the prime mover, and a second valve controlling the flov'v of fluid at said extraction opening, of a control mechanism therefor comprising means providing a first fluid pressure varying in response to changes in'demand for extracted fluid, means providing a second fluid pressure varying in response to changes in demand for exhausted fluid, means responsive to said first and second fluid pressures for providing a third fluid pressure, means responsive to the third fluid pressure for controlling said admission valve, and means responsive to the second fluid pressure for con trolling said second valve. A

4. The combination defined in claim 3 and further including means providing a fourth fluid pressure varying as a function of the speed of the prime mover, the means for con trolling said admission and second valves being also responsive to said fourth fluid pressure.

In testimony whereof, I have hereunto subscribed my name this'27th day of August, 1930.

CLARENCE B. CAMPBELL.