US1777470A

US1777470A - Multistage-bleeder-turbine control

Info

Publication number: US1777470A
Application number: US354027A
Authority: US
Inventors: Marsland Roland
Original assignee: Westinghouse Electric Corp
Current assignee: Westinghouse Electric Corp
Priority date: 1929-04-10
Filing date: 1929-04-10
Publication date: 1930-10-07
Anticipated expiration: 1947-10-07

Description

y GB\ l Oct.`7, 1930. l R. MARSLAND 1,777,470.

MULTISTAGE BLEEDER TURBINE CONTROL Filed April` 10. 1929 INVENTOR Fs' 2 RMnrslnnd ,amm

ATTORNEY Patented Oct. 7, 1930 l UNITED STATES yPA'rENrI OFFICE ROLAND `INIIARSLAND, OF MOYLAN, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE ELECTRIC @c MANUFACTURING COMPANY, A CORPORATION F PENNSYLVANIA MULTISTAGE-BLEEDER-TURBINE CONTROL Application filed April 10,

My invention relates to a governing system, more particularly to a governing or cont-rol system for a double or multiple extraction turbine, and it has for its object to -pro- '5 vide improved regulation.

A specific object is to regulate the flow at each extraction opening in response to the pressure of the extracted steam, and to compensate the admission of motive fluid to the turbinein accordance with the amount of steam extracted at each of the extraction openings.

These and other objects areeffected by m e invention, as will be apparent from the fo lowing description and claims taken in connection with the accompanying drawin s,

forming a part of thisapplication, in whic Fig. 1 'is a diagrammatic representation vof my governing system; and, 2o

Fig. 2 is a sectional view ofl a detail.

Referring n'ow to the drawing more in detail, I show a turbine 10 having an admission valve 11, andextraction openings 12 and 13 communicating with intermediate pressure stages in the turbine'indicated at 14 and 15, respectively. Diaphragms 16 and 17 are interposed between the pressure stages 14 and 15 and the succeeding turbine stages, and conduits 18 and 19'provide by-passes around the diaphragms, through which the motive fluid not extracted may be conveyed to continue its expansion in a lower pressure stage' or stages of the turbine.

Valves 21 andv 22y are provided in the bypass conduits 18 and 19 to control the flow` of motive fluid therethrough. By controlling the amount of fluid held back'from the lower pressure stages, these valves regulate the flow throughthe extraction openings 12 and 13. It will be apparent to those skilled in the art that any other construction which regulates the distribution of fluid between the bleeder opening and the succeeding turbine stages may be used as the equivalent of the by-pass valve.

The admission valve 11 and the by-pass valves 21 and 22 are controlled by governors 23, 24 and 25, respectively, wh1ch may be and are shown as similar in construction; Each governor includes a piston 26 operat- 1929. Serial No. 854,027.

' The variable lfluid pressure is admitted to the lower end of the cylinder to bias the piston upwardly, and a spring 28 biases the piston 26 downwardly in opposition to smid fluid pressure. The iston 26 isy rovided with a restricted ori ce 29, throug y which some of the fluid underpressure beneath the piston flows tothe upper side of the piston. A back pressure is imposed on the fluid flowing through the orifice by controlling its escapev from the u per end of the cylinder, and this pressure iases the piston 26 in cooperation with the spring 2,8 and in oppos1- tion to the variable fluid pressure beneath the piston.' Each piston is connected to its valve in any suitable manner known to the art, as through a fulcrumed lever 31.

The back pressure in the governor 24 is controlled in response to pressure at the extraction opening 12, that 1n the governor 25 in response to pressure at the opemng 13, and that in the governor 23 in response to both` of saidpressures. The mechanism for accomplishing this will now be descr1bed. The pressure ofthe fluid flowing through the extraction opening 12 and the condult ling a ever 38 fulcrumed intermediate its ends, as at 39. An adjustable srring 41 biases t-he lever 38 in opposition to the diaphragm and gives it a position corresponding to the pressure imposed on the dlaphragm 37.

Connected to the lever 38 on the other side of the fulcrum 39 is a stem 42 controlling a relief or back-pressure Valve 43. The valve 43 communicates4 with the up er end of the cylinder of the governor 24 t rough a conduit 44, and controls the pressure therein by controlling the escape of fluid therefrom. Referring now to Fig. 2, the stem 42 extends through the cylindrical valve casing 45 and through a piston 46 operating therein.

The piston 46 abuts the upper end of a spring 47, which biases the valve 43 to closed position. A passage 48 is formed in the lower end ofthe stem 42 andr extends from a point. which is normally just above the top face of the piston 46 to the lower end thereof. A drain conduit 49 communicates with the valve. casing between the'piston 46 and'the valve 43.

Fluid pressure from y,the impeller 32 is supplied to the valve casing 45 above the piston 46 through a conduit 51, in which an orifice 52 is interposed to restrict the flow to the valve casing. This pressure is im' osed o n the piston 46 and moves the same ownwardly until the upper end of the passage 48 is uncovered suiciently to permit the escape of as much fluid as flows into the casing.

When the stem 42 is moved downwardly, the esca e of the fluid flowing into the casing is cut o and the piston 46 moves downwardly untilthe passage 48 is again slightly luncovered to permit suilicient escape, and when the stem moves upwardly, the passage 48 permits a greater amount of fluid to escape until the spring 47 moves the piston 46 upwardly to restore' the required escape openlt will thus be seen that the piston 46 is moved to follow the stem 42 without any substantial resistance to movement of the stem, thereby applying a spring pressure on the valve 43 in accordance with the position ot the stem 42.

The pressure of the fluid flowing through the extraction opening 13 to the conduit-53 is communicated tov a similar diaphragm 54, which acts on a lever fulcrumed at 56 and biased by an adjustable spring 57. The oth.-

` er end of the lever 55 actuates a stem 58 controlling a back pressure valve 59 in the same manner that the stem 42 controls the valve 43. The valve 59 communicates through a conduit 61 with the upper end of the cylinder of the governor 25, and controls the back pressure therein.

A floating lever 62 is connected at its'ends to the levers 38 and 55, and intermediate its ends is connected to a link 63. y The link 63, in turn,is connected to a stem 64 by a lever 65 pivoted to a fulcrum at 66. The stem 64 controls, in the manner in which valve 43 is controlled, a back-pressure valve 67, which communicates with the admission valve gov# ernor 23.through a conduit 68'and controls the back pressure therein. Y

The fulcrum 66 is vertically adjustable, by means of a screw-threaded stem 66', tovary the back pressure imposed by the valve 67 relative to the link 63, thereby controlling the speed setting of the governing system.

The operation of this embodiment of my invention is as follows;

The admission valve 11 andthe by-pass valves 21 'and 22 all move in response to changes in speed of the turbine by reason of the impeller pressure imposed on the under side of each governor p1ston 26. Upon an increase in speed, the impeller pressure increases, moving the pistons 26 upwardly against the-spring 28 and closing the valves. The flow of fluid is thus decreased through the length of the turbine. The pressure at each extraction opening, however, remains substantially the same.

Upon decrease in speed and decrease in fluid pressure, the springs 28 move the pistons 26 to increase the valve openings.

The correct extraction pressures are maintained in the following manner: Assume that v the demand for steam from the pressure stage 14 increases, resulting in a decreased pressure. The decreased pressure is communicated to the diaphragm 37, permitting the spring 41 to act on the lever 38 to raise the stem 42.. Raising of the stem 42, as explained above, causes upward movement of the piston 46, which decreases the compression of the spring l47 and thereby decreases the back pressure which the valve 43 imposes on the fluid escaping from the upper end of the cylinder in the governor 24. The impeller pressure below the piston 26 in the governor 24 now preponderates and moves thepiston upwardly to* decrease the opening of the by-pass valve 21. 'More fluid 1s thus held back from the `lower pressure stages to supply the bleeder takes place, as will be apparent, increasing the by-pass valve opening to pass the' excess steam to the lower pressure stages of the turbine.

Changes in bleeder pressure in the conduit 53 are likewise communicated to the diaphragm 54, moving the lever 55 and the stem 58 to vary the back pressure in the governor 25 and vcontrolling the by-pass valve 22 to hold back sufficient steam for bleeder demand.

The changes in bleeder demand at either opening affect the amount of work done by the fluid in carrying the turbine load, since, as will be apparent, the fluid extracted does not complete its expansion in the lower pressure stage or stages. sarv to compensate the admission valve for the amount of fluid extracted through the It is, therefore, necesmovement of the lever 62 results in upward movement of the link 63 and downward i movement of the stem 64. The spring 47 is further com ressed and the valve 67 imposes an increase back' pressure, whlch 1s communicated to the governor 23. The piston 26 is, therefore, moved downwardly to increase the. admission valve opening. Addi- I tional-motive fluid is thus supplied to carry the turbine load and to supply a part of the increased demand for steam at the extraction opening 12.

Upon decrease 1n demand for extraction steam, the reverse operation taken place.

Upon an increase 1n demand for extractlon -steam at the opening 13, the pressure'drops,

and, as explained above', the end of the lever to which the stem 58 and the lever 62 are connected, is moved upwardly` moving the lever (S2-and the stem 63 upwardly. The admission valve opcning is increased, as before explained, thus admitting more steam to compensate for the increased amount of bleedlng.

It will thus be seen that. I have devised a novel fluid pressure governing system for a multiple extraction turbine wherein the admission valve governor is compensated for the amount of partially expanded steam extracted from the turbine at a plurality of pressure stages.

' 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 yvarious changes and modifica-y extraction at two of said openings and means responsive to said `Huid pressure for controlling the admission valve.

2. The combination with a turbine having an admission valve and a plurality of extraction openings, of governing means" for the admission valve comprising means providing` a fluid pressure varying in accordance with the extraction at two of said openlngs and means responsive to said fluid pressure and to speed of the turbine for controlling the admission valve.

3. The combination with a turbine having an admission valve and a plurality of extraction openings, of governing` means for the admission valve comprising means providing a iiuid pressure varying in accordance with the extraction at two of said openings, means providing'a fluid pressure varying as a function of the speed. the turbine, and

means responsive to bothof said fluid pres sures for controlling said admission valve.

4. The combination with an elastic uid turbine havin an admission valve yand o eninvs communicating with two' interme iate pressure stages therein, of means providing ak fluid pressure variable in response to the pressures at both of said pressure stages, and means responsive to said variable fluid pressure and to the speed of the turbine for controlling said admission valve.

5. lThe combination with an elastic uid turbine having an admission valve and openings communicating with a plurality of pressure sta-ges therein, of a governing system therefor including means associated with each of said openings for controlling the flow of fluid therethrough in accordance with the pressure thereof, means providing a luid pressure varying with the pressures at a plurality of said openings, and means responsive to said variable fluid pressure forcontrolling said admission valve.

6. The`combination with an elastic fluid turbine having an admission valve and openings communicating with two pressure stages therein, of a governing system therefor comat each of said openings in response to the pressure thereof, means `providing a fluid pressure variable in response to the Ypressures at both of said pressure stages, and means responsive to said variable :fluid pressure and to the speed of the turbine for controlling said admission valve.

7. The combinationwith a turbine having openings communicating with a plurality of pressure stages therein, a valve regulating the flow of fluid at each of said stages and an admission valve, of means controlling the valve at each stage in response to the pressure therein and to the speed of the` turbine, means providing a fluid pressure varying in response to the pressures in a plurality of said stages, and a governor responsive to the speed of the turbine and to said variable iluid pressure for controlling the admission valve.

8. The combination with an elastic fluid turbine having an admission valve and o nings communicating with two interme iate pressure stages therein, of a governing system prising means for regulating the flow of fluid los therefor comprising meansl associated with each of said pressure stages for providing a fluid pressure varying in response to the pressure at the pressure stage and regulating the flow of Huid at the pressure stage in response to said variable fluid pressure, means-operated b both of said means and providing a variab e vfluid pressure, and means responsive to said last-mentioned Ifluid pressure for controlling said admission valv l 9. The -combination with an elastic fluid turbine having an admission valve and openings communicating with two intermediate pressure stages therein, of a governing systern therefor 'comprising means associated with each of said pressure stages for providing a fluid pressure varying in response to the pressure at the pressure stage and for regulating the flow of fluid at the pressure stage in response to said variable fluid pressure, means operated by both of said means and providing a variable Huid pressure, and means responsive to said last-mentioned fluid Y pressure and to the speed of the turbine for controlling said admission valve.

10. The combination with a turbine having a plurality of extraction openin an admission valve, and a valve regulatmg the flow at each of said openings, of means for controllinglsaid valves comprising means providing a Huid pressure varying as a function of the speed of the turbine, a governor for each valve,.each governor having a pressureresponsive element subjected to said uid pressure, means associated with each extraction opening providing a fluid pressure varying wlth the pressure of the extracted fluid,

means for subjecting said variable fluid pressure to the pressure-responsive elements of the associated governor, means providing a Huid pressure varyingwith the pressures of the extracted uid at a'plurality of saidI extraction openings, and means for applying said lastmentioned fluid pressure to the pressure-responsive element in the admission valve governor.

In testimony whereof, I have hereunto 'subscribed my name this 27 th da of March, 1929.

ROLAND ARSLAND.