US1876531A - Turbine control mechanism - Google Patents

Description

Sept. 6, 1932. o. B RYANT TURBINE C ONTROL MECHANISM Filed Aug. 50, 1930 INVENTOR Ozro IV. Bryant ATTORNEY ESE All

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Patented Sept. 6, 1932 ,uuiren STATES PATENT: oF- ic ozrto N. BRYANT, or MOORES, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE nLEc TRIO a MANUFACTURING COMPANY, A CORPORATION or PENNSYLVANIA TURBINE CONTROL MECHANISM Application filed August 30, 1930. Serial No, 473,929.

My invention relates to a control mechanlsm for a prlme mover, more particularly to a control mechanism for a multistage elas- I tie fluid prime mover having openings at two or more intermediate-pressure stages for extracting partially expanded motive fluid from the prime mover or for admitting motive fluid thereto, and it has for its object to provide an improved construction of such mechanism;

A specific object is to provide an improved control mechanism operative to regulate the flow at each extraction opening in response tothepressure of the extracted motive fluid, and to compensate the admission of motive fluid to the prime mover in accordance with the amount of motive fluid extracted at each of said openings.

In accordance with the present invention, I provide a control mechanism ncludlng means associated with each extraction opening for providing a regulating fluid pressure which varies with the extraction pressure and which regulates the flowof fluid at the Another variable fluid pressure responsive to the regulating fluid pressures compensates the admission of motive fluid to the prime mover.

These and other objects are effected by my invention, as will be apparent from the 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 representation of the control mechanism appliedto an elastic fluid turbine.

Referring now to the drawing more in detail, I show a turbine having an admission valve 11, and openings 12 and 13-communieating with intermediate-pressure stages in the turbine indicated at 14 and 15, respectively. The openings 12 and 13 communicate with conduits 12' and 13, respectively, and partially expanded motive fluid may be ex tracted from the intermediate pressure stages through the respective openings and conduits. Diaphragms 16 and 17 are interposed.

between the pressure stages 14 and and r the succeeding turbine stages, and conduits 18 and 19 provide lay-passes around the diaphragms, through which the motive fluid not extracted maybe conveyed to continue its expansion in'a lower pressure stage or stages of the turbine;

Valves 21 and 22 are provided in the by pass conduits l8'and'l9, respectively, to reg- I ulate the flow of motive fluid therethrough; By controlling the amount of fluid held back from the lower pressure stages, these valves regulate the flow through the openings 12 and 13 and maintain the pressures at the extraction stages. It will be apparent to those skilledin the art that any other'construc-- tion which regulates thedistribution of fluid between the extraction opening and the succeeding turbine stages may be used as the equivalent of the by-pass valve.

The admission valve 11 and the bypass valves 21 and 22 are controlled by governors- 23, 24 and 25, respectively, which may be and are shown as similar in construction. Each governor includes a'piston 26, which operates in a cylinder 27 and is connected to the associated valve in anyv suitable manner, as through a fulcrum lever 84:. Fluid pressure preferably in the piston 26, through which a restricted flow of fluid'under pressure provided by the impeller 28 is admitted to the upper end of the cylinder 27 above the piston 26.

A back pressure is imposed on the fluid flowing through the orifice by controlling its escape from the upper end of the cylinder, and this pressure biases the piston 26 in cooperation with the springs 32 and in opposition to the variable fluid pressure beneath the piston; The back pressure in the governor 24 is controlled in responseto pressure at the extraction opening 12, that in the governor inresponse to-pressure at the opening 13, and that in the governor 23 in response to both of said pressures. The mechanism for accomplishing this function will now be described.

The upper end of the cylinder of the governor 24 communicates, through a conduit 35, with a pressure relief valve 36 which controls the pressure in the upper end of said cylinder. The pressure reli f valve is biased to closed position by a compression spring 37 interposed between the valve and a spring abutment 38. The latter is connected to a lever 39 fulcrumed at 41.

A diaphragm 42 is subjected to the pressure of the fluid extracted through the opening 12 and the conduit 12, communicating thereto through a conduit 43. The diaphragm transmits the force of the fluid pressure thereon to the lever 39 in opposition to the force of the spring 37. A group of weights 44 further bias the lever 39 against the force of the fluid pressure on the diaphragm 42.

The upper end of the cylinder of the governor 25 communicates, through a conduit 45, with a pressure relief valve 46, which controls the back pressure in said governor. The valve 46 is likewise biased to closed position by a compression spring 47 interposed between the valve and a spring-holding member 48. The latter is connected to a lever 4 fulcrumed at 51.

The diaphragm 52 is subjected to the pressure of the fluid flowing through the opening .13 and the conduit 13, communicated thereto through a conduit 53. The force of the fluid pressure on the diaphragm 52 is transmitted to the lever 49 in opposition to the force of the spring 47. A. group of weights 54 biases the lever 49 in opposition to the force of the fluid pressure.

The back pressure in the governor 23 iscontrolled by a device which may be termed a compensator, and which is indicated by the numeral 55. The latter includes a pressure relief valve 56 which communicates, through a conduit 57, with the upper end of the cylinder of the governor 23 and controls the back pressure therein. The pressure relief valve is biased to closed position by a spring 58, the bias being transmitted to the valve through a stem 59 abutting the valve and having a collar 61 contacting with the spring 58. The stem 59 is formed at its upper end with a downwardly-facing knife edge 62.

The control device further includes levers 63 and 64, abutting against knife edge fulcrums 65 and 66, respectively. The knife edges 65 and 66 are carried by a stationary plate 67. The latter is formed with longitudinal slots 68, and the knife edges 65 and 66 are secured to the plate by screws 69 which extend through the slots 68.

The levers 63 and 64, at their adjacent ends, engage the knife edge 62. Intermediate their ends, the levers 63 and 64 are engaged by pressure-responsive elements 71 and 72, subjected to the back pressures provided by the pressure relief valves 36 and 46, respectively, communicated through extensions of the conduits 35 and 45. g

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

The admission valve 11 and the 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 underside of each governor piston 26. Upon increase in speed, the impeller pressure increases, moving the pistons 26 upwardly against the spring 32 to move the valves in closing direction by amounts in accordance with the increase in impeller pressure. The flow of fluid is thus decreased throughout 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 32 move the pistons 26 to increase the valve openings.

The desired pressures of the fluid at the extraction stages 14 and 15 are maintained in the following manner:

Assume that the demand for motive fluid from the pressure stage 14 increases, resulting in a decreased pressure in the conduit 12. The decreased pressure is communicated to the diaphragm 42, decreasing the compression of the spring 37. The closing force on the pressure relief valve 36 is decreased, and

the latter decreases the back pressure in the governor 24.

The impeller pressure below the piston 26 in the governor now preponderates and moves the piston upwardly to decrease the opening of the by-pass valve 21. More fluid is thus held back from the lower pressure stages to supply the demand for extracted fluid and to maintain the pressure thereof.

Upon decrease in demand and increase in extraction pressure, the reverse operation takes place. The compression of the spring 37 is increased, and the valve 36 provides an increased back pressure in the governor 24. The piston thereof thereupon moves the bypass valve in opening direction to pass the excess motive fluid to the lower pressure stages of the turbine.

Changes in extraction pressure in the conduit 13 are communicated in a similar manner to the diaphragm 52, moving the lever 49 to vary the compression of the spring 47 and the pressure provided by the relief valve 46 in the governor 25. The governor 25 controls the by-pass valve 22 to hold back sufflcient motive fluid for supplying the required amount of extracted fluid to the conduit 13 and for maintaining the pressure thereof.

The changes in demand for extracted fluid 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 stage or stages. It is, therefore, necessary to compensate the admission valve for the amount of fluid extracted to the openings and, in accordance with the present invention, this is accomplished by the compensator 55. As the demand for fluid from the pressure stage 14 decreases, for example, the pressure increases and the pressure relief valve 36 increases the back pressure in the governor 24, effecting opening movement of the bypass valve 21. The increased back pressure is conveyed through the conduit 35 to the pressure-responsive element 71, which transmits an increased upward force to the lever 63.

The latter, by reason of its engagement with the knife edge 62, transmits the increased upward bias to the stem 59 in opposition to the force of the spring 58. The resultant or net closing force on the pressure relief valve. 56 is thereby decreased, providing a decreased back pressure in the governor 23. The impeller pressure in the governor 23 preponderates and moves the piston 26 in valve closing direction for decreasing the admission of motive fluid to the turbine. The decrease in load thus carried by the highpressure end of the turbine compensates for the increase of load carried by the lower pressure stages upon opening movement of the by-pass valve 21.

Upon increase in demand for extracted fluid at the opening 12, the reverse operation takes place, as will be apparent.

Upon change in demand and pressure at the opening 13, the corresponding change in back pressure in the conduit 45 acts upon the pressure-responsive element 72 to vary the upward bias transmitted by the lever 64 to the stem 59. The closing force on the pressure relief valve 56 is varied in'the same manner to vary the back pressure in the governor 23, which effects the required compensation of the admission to the turbine.

In order to provide the desired increment of compensating movement of the valve 11 upon a given increment of movement of either of the by-pass valves, an adjustment is provided in the compensator. Such adjustment may be eflected by moving the corresponding knife edge 65 or 66 to vary the lever arm ratios of the corresponding lever 63 or 64.

It will be apparent that the pressure within the region enclosed by an extraction pressure stage and the opening and extraction conduit communicating therewith is substantially the same, or at least varies similarly with changes 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 an elastic fluid prime mover having an admission valve and extraction or admission openings communicating with two intermediate-pressure stages therein, of a governing system therefor comprising means associated with each of said pressure stages for providing a fluid pressure varying in response to the pressure at said stage and for regulating the flow of fluid at the pressure stage in response to said variable fluid pressure, means responsive to both of said variable fluid pressures for providing a third variable fluid pressure, and means responsive to said third variable fluid pressure for regulating said admission valve.

2. The combination defined in claim 1 and further comprising means providing a fluid pressure varying as a function of the speed of the prime mover, each of the regulating means being further responsive to the lastmentioned fluid pressure.

3. The combination with an elastic fluid prime mover having an admission valve and extraction or admission openings communicating with two intermediate pressure stages therein, of a governing mechanism therefor comprising means providing a fluid pres sure varying as a function of the speed of the prime mover, a control device associated with each opening and providing a fluid pressure varying in response to change in pressure at the opening and in the same direction as such change, a compensator providing a fluid pressure varying in response to change in either of the last-named fluid pressures and in the direction opposite to such change, means responsive to the first mentioned fluid pressure and to the fluid pressure provided by the compensator for controllingthe admission valve, and means for controlling the flow at each opening in response to the first mentioned fluid pressure and to the fluid pressure provided by the associated control device.

In testimony whereof, I have hereunto subscribed my name this 29th day of August,

OZRO N. BRYANT.

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