US2165175A - Control system - Google Patents

Description

July 4, 1939. P. s. DlCKEY El AL CONTROL SYSTEM Filed July 31, 1936 2 Sheets-Sheet 1 m F 3 2W4 2 m 2 z z k w 2 3 0 3 2 Z M w 4 7 WW 3 a W 3 w W M a 4 v M M m 2 2 4 m A 3 ,hEEHW\\ m F.

INVENTORS PAUL 8. D/CKEY JAcK F SHANNON ATTO Y July 4, 1939.

P. S. DICKEY ET AL CONTROL SYSTEM Filed July 31, 1956 2 Sheets-Sheet 2 FIG. 6

INVENTORS PAUL \SI D/CKEY JACK F SHANNON Patented July 4, 1939 PATENT OFFICE 2,165,175 CONTROL SYSTEM Paul S. Dickey and Jack F.

Ohio, assignors to Bailey.

Shannon, Cleveland, Meter Company, a

corporation of Delaware Application July 31, 1936, Serial No. 93,688

21 Claims.

This invention relates to control systems for prime movers, and more particularly to control systems for high pressure non-condensing prime movers. Our invention, for example, is particularly applicable in connection with dual-pressure power plants wherein high pressure vapor after passing through a prime mover is exhausted into a low pressure system. In such plants it is necessary and desirable to control the rate of flow of high pressure vapor so that the pressure of the vapor exhausted will be in accordance with that preferably carried on the low pressure system. In other words, the load on the prime mover is varied to maintain a predetermined exhaust vapor pressure.

It is accordingly one object of our invention to provide a control system which will continuously maintain the exhaust pressure at a desired magnitude through regulation of the rate of fiow oi the high pressure vapor, without overtravel or hunting.

It is a further object to provide acontrol systern whereinthe control, of-- the high T pressure vapor in accordance with the exhaust vapor pressure may be modified in accordance with the power output of the prime mover.

It is another object of our invention to provide a control-system wherein the control of. the high pressure vapor may be further modified in ac- 30 cordance with the pressure differential existing across a portion of the prime mover.

It is a further object to provide a control system wherein the control of the low pressure vapor may be modified in accordance with the magnitude of a conditionproduced or maintained by the exhaust vapor.

It is in general a further object to provide a control system which will prevent the establishment of conditions harmful either to the prime mover or the apparatus driven thereby.

Further objects will be apparent from the description to follow and from the drawings in which:

Fig, 1 is an illustrative embodiment of our invention in diagrammatic form.

Fig. 2 is a cross section to an enlarged scale of a typical pilot valve used with our invention.

Fig. 3 is a further illustrative embodiment of our invention.

, Fig. 4 is a modification of a part of the arrangement shown in Fig. 3.

Fig. 5 represents a modification of our invention as illustrated in Figs. 1 and 3.

Fig. 6 is a modification of a part 0! the arrangement shown in Fig. 5.

, an enlarged scale in Fig.

Fig. '1 illustrates a further embodiment of invention.

In Fig. 1, reference character l indicates a prime mover such as a turbine to which vapor at a relatively high pressure and temperature is supplied through a conduit 2.

The vapor after passing through the prime mover is exhausted and temperature system (not shown). The

' through a conduit 3 into a relatively low pressure SYS- tem to which the conduit 3 leads may be made up of one or more low pressure prime movers or other vapor utilizers, such as evaporators, heating tanks, etc.-

Mechanically connected to the turbine l and driven thereby is a generator 4, the electrical output of which is transmitted through conductors 5, B and I to an electrical system comprising,

for example, other generators and current consumers such as motors, etc.

In the embodiment shown in Fig. 1 variations in electrical load on the system are preferably varied to maintain takenby the other gen-- erators, that carried by the prime-mover i being the pressure of theexhaust vapor at a predetermined desired value as hereinafter more fully explained.

Connected to the exhaust conduit 3 is a pres- I Bourdon tube 4A pivotally con= nected through a link 9 to a horizontal member iii. A pilot valve generally indicated at H sure sensitive and having a movable valve member I? pivotally connected to the member in is arranged to establish a fluid loading pressure within a pipe !3 in accordance with the vertical positioning of the valve member l2.

The pilot valve ii is shown in cross section to 2 and is of the type forming the subject matter of the patent to Johnson 2,054,464. Suitable fiuid under pressure, suc compressed air, is admitted through an inlet h as port It to a cylindrical passageway IE5, longitudinal of the valve body, and is exhausted to the atmosphere at either end. The movable valve member I2 is provided with lands is and ii of slightly less diameter than the passageway I5 so that a pressure gradient is established by the pressure fluid in going past them.

Located substantially adjacent the lands l6 and H are outlet ports l8 and I9 respectively. Upward positioning of the valve member l2 increases the fiuid pressure available at the port l8 and decreases that available at the port l9. At one position of the movable valve member, which we for convenience term the neutral position, the pressure existing at the port l8 will be same as that existin the port l8. If it is desired to establish a loa g at ding pressure varying directly with upward positioning of the valve member 6? connection is made to the outlet port I 8, whereas if it is desired to establish a fluid pressure varying inversely with the upward positioning of the valve member l2 connection is made to the lower port l9. In practice the outlet port not in use is blocked by a suittable plug or stopper. I

In Fig. 1 it is desired that the loadmgpressure established by the pilot valve ll vary in direct proportion to upward positioning of the valve member l2. Accordingly the pipe l3 connects to the upper outlet port and transmits the loading pressure to a chamber 20 of a standardizing relay 2|, of the type forming the subject matter of a patent to Harvard H. Gorrie No. 2,098,91

One side of the chamber 20 is formed by a movable pressure sensitive diaphragm 22, to which is attached a vertical member 23, the lower end of which engages a horizontal fulcrumed member 24 operating a fluid pressure supply valve 25 when tilted in one direction and an exhaust valve 26 when tilted in the opposite direction. The fluid pressure supply valve 25 which may be connected to any suitable source of fluid pressure (not shown) and the exhaust valve 26 control the pressure within a chamber 21 formed by a pressure sensitive diaphragm 28. Also iormed by the diaphragm 28 and a partition 29 is a chamber 30 connected to the chamber 21 by a passageway 3|, in which is located an adjustable bleed orifice 32.

Increases in fluid pressure within the chamber 20 eflect a downward positioning oi the member 23 opening the supply valve 25, thereby increasing the pressure within the chamber 21. When the increase in pressure within the chamber 21 is proportional to the increase in pressure within the chamber 20 the force created thereby against the diaphragm 28 will be suflicient to restore the member 23 to the neutral position, closing the supply valve 25. Conversely, upon a decrease in pressure-within the chamber 20 the exhaust valve 26 will open until the pressure within the chamber 21 is decreased a proportionate amount. A manually adjustable spring 33 is provided so that the absolute value of the pressure existing within the chamber 21 may bear any relation desired to the absolute values of the pressure existing within the chamber 20.

Whenever a pressure differential exists between the chambers 21 and 3D pressure fluid will be transmitted through the passageway 3| at a rate dependent upon the adjustment of the bleed oriflce 32. Such transmittal of pressure fluid and consequent momentary change in existing pressure difference will produce a further actuation of the valve 25 or 26 to restore the diflerential to the initial magnitude. Thus upon an increase in pressure within the chamber 21 above that existing within the chamber 30 pressure fluid will pass through the passageway 3| from the former to the latter, tending to increase the force acting downwardly upon the diaphragm 28 which will position the member 24 to open the supply valve 25 until the difference in pressure is restored to the initial value. It is apparent that only when the pressure within the chamber 30 is equal to the pressure within the chamber 21 and the force produced by the loading pressure within the chamber 20 upon the diaphragm 22 equal to that produced by the spring 33 will the device be in stable equilibrium and the valves 25 and 28 remain closed. If the loading pressure within the chamber 20 increases, an immediate and propor- I tionate increase in the pressure within the chamber 21 will-occur and thereafter a continuing increase in pressure within the chamber 21 will be sustained until the loading pressure within the chamber 20 is restored to the predetermined value. Conversely upon a decrease in loading pressure within the chamber 20 an immediate and proportionate decrease in pressure within the chamber 21 will occur, and thereafter a continuing decrease until the loading pressure is restored to the predetermined value.

Connected to the chamber 21 by a pipe 34 is a chamber 35 of an averaging relay 33. The relay 36 is somewhat similar to the standardizing relay 2|, but serves merely to produce changes in a control pressure within a chamber 31, provided with supply and exhaust valves 38 and 33 respectively, proportional to pressure changes within the chamber 35 or a chamber 40. Control pressures established within the chamber 31 are transmitted through a pipe 4| to a spring loaded pressure sensitive diaphragm motor 42 operating a valve 43 located in the supply conduit 2. The arrangement is such that as the fluid pressure within the diaphragm motor 42 increases, the valve 43 is positioned a proportionate amount in a closing direction decreasing the rate of flow of high pressure vapor through the conduit 2 to the prime mover In operation, the spring 33 (relay 2|) is initially adjusted so that when the predetermined or desired vapor pressure exists within the exhaust conduit 3 the relay 2| will be in stable equilibrium. If now the pressure within the exhaust conduit 3 should increase, for example, a proportionate increase in loading pressure established by the pilot would occur, producing an immediate and proportionate change in pressure within the chamber 21 and transmitted to the diaphragm motor 42 through the relay 36. Thereafter inasmuch as a pressure differential had now been established between the chambers 21 and 30 the pressure transmitted to the diaphragm motor 42 would continue to increase. The increasing pressure within the diaphragm motor 42 would serve to position the valve 43 in a closing direction, thereby reducing the rate of flow of high pressure vapor to the prime mover and accordingly reducing the pressure of the vapor within the exhaust conduit 3. When the pressure of the exhaust vapor has again been restored to the desired value the loading pressure established by the pilot I I would again be that necessary to maintain the standardizing relay 2| in stable equilibrium. In general, it is apparent that the control system acts, upon a change in the exhaust pressure, to produce an initial and proportionate change in the rate of flow of high pressure vapor to the prime mover I in a direction tending to restore the pressure of the exhaust vapor to the desired value and thereafter produces a continuing change in the rate of flow of high pressure fluid until the pressure of the exhaust vapor is restored to the desired value.

To prevent the overloading of the generator 4 regardless of the demand for low pressure vapor our control system provides means for modifying the control of rate of flow of high pressure vapor in accordance with the load on the generator 4. Connected in the conductor 1 is the primary of a current transformer 44, the secondary of which is connected to a solenoid 45. When the current output of the generator 4 reaches a predetermined value the solenoid 45 is arranged to move upwardly, closing a finger 46. Closure of 48 serves to energize a field 41 or a self-starting motor 48 from a suitable source 48.

Energization or the field 41 effects an upward positioning of a member 58 by the motor 48 which is pivotally connected through a link 5I to the member ID. The motor 48 may be provided as known with suitable reducing gears so that the upward positioning 'of the member 58 will occur at any desired rate.

Upward positioning of themember 40 serves to produce proportionate increases in the loading pressure established by the pilot valve II and proportionate movements of the valve 43 in a closing direction. When the load upon the generator 4 has decreased below the predetermined value the finger 45 will open and further upward positioning of the To prevent the member 58 from being positioned upwardly too rapidly a suitable interrupter, such as indicated at 52, may be connected in circuit with the field 41 so that the motor 48 will be periodically stopped and the effect of the positioning of the valve 43 in a closing direction upon the current output of the generator 4 determined before a further positioning of the valve in a closing direction is made.

After the load upon the generator 4 has been reduced below the predetermined value, the member 58 may be restored to its normal position through closure of a push button 53 which serves to energize a field 54A, causing operation of the motor 48 in reverse direction to that produced by energization of the field 41. After the member 58 has been restored to the normal position the movable valve member I2 of the pilot I I will be positioned solely by changes in pressure of the exhaust vapor within the conduit 3. A manually operated switch 54 may likewise be provided connected in parallel with the finger 46 to provide manually controlled positioning of the member 58 in an upward direction so that the valve 43 may be positioned in a closing direction if desired. It will be understood that the operation of the motor 48 from excessively high generator load is in the nature of an emergency precaution.

To insure efficient operation of the prime mover I the pressure difference across any given number of stages should be maintained below a predetermined maximum, otherwise an excessive amount of vapor will by-pass the wheels and not be available for useful work. In some cases it may be desirable, upon this differential reaching a predetermined maximum, to completely close the valve controlling the admission of vapor to the turbine. In other cases it may be desirable to position the valve in a closing direction an amount proportional to the increase in the differential above the desired value.

To provide for the desired closure of the valve 43 upon an increase in differential existing across predetermined points of the prime mover I above a predetermined amount we show connected to an intermediate stage a pressure sensitive Bourdon tube 55 and connected to the exhaust stage a pressure sensitive Bourdon tube 56. The points of the prime mover I to which the Bourdon tubes 55 and 56 are connected may be selected to include any critical section of the prime mover I as will be understood by those familiar with the art, those shown in Fig. 1 being merely illustrative.

Pivotally connected to the Bourdon tubes 55 and 55 is a differential link 51, to the mid point of which is connected a movable valve member member 58 will cease 58 of a pilot valve 58 similar to the pilot valve II. The pilot valve 58 establishes a loading pressure varying inversely with the difference in pressures within the Bourdon tubes 55 and 56 and which is transmitted through a pipe to the chamber 48 of the averaging relay 36. It will be apparent that, assuming the pressure within the Bourdon tube 55 remains constant, if the pressure within the Bourdon tube 55 increases, the movable valve member 58 will be moved upwardly, decreasing the loading pressure established within the chamber 40. This will serve to produce an increase in pressure within the chamber 31 which will position the valve 53 in a closing direction to decrease the pressure to which the Bourdon'tube 55 is subjected.

In general, it is usually desired that the difference in pressure between the points of the prime mover I to which the Bourdon tubes 55 and 5B are connected be permitted to vary in accordance with the rate of flow of vapor through the prime mover I without modifying the position of the valve 43, and only at times when the differential exceeds a predetermined maximum limit will the valve 43 be positioned in a closing direction through the agency of the pilot 59. Accordingly the movable valve member 58 may be arranged so that throughout the range in difierential pressures experienced in normal operation of the prime mover I the lower land of the movable valve member 58 will be below the outlet port, so that a loading pressure substantially equal to the pressure of the fluid admitted to the pilot valve is efiective within the chamber 48. When the differential pressure reaches the predetermined value the lower land of-the movable valve member 58 may be arranged to move adjacent the lower outlet port and accordingly decrease the loading pressure effective within the chamber 40 and produce a positioning of the valve 43 in a closing direction. Itwill be apparent, however, that if desired the lower land of the movable valve member 58 may be arranged to move adjacent the lower outlet port within the normal range of differential pressures experienced, so that increases in this differential effect a proportionate positioning of the valve 43 in a closing direction, and decreases in the differential effect a proportionate opening of the valve 43.

In Fig. 3 we show a further embodiment of our invention vidierein the prime mover I exhausts into a low pressure header BI to which are connected heating coils, indicated at 62 and 63, of heat exchangers 64 and respectively. Condensate from the coils 62 and 63 is discharged through a drain 85 and vapor liberated is transmitted through a header 5? to a point of usage (not shown). In the arrangement shown changes in load upon the prime mover I will affect the pressure within the exhaust conduit M which in turn afiects the rate of liberation of vapor from the heat exchangers 84 and 65, thereby causing a variation in pressure within the header 6?. Likewise changes in pressure within the conduit 5? will ocur if the demand for vapor therefrom increases or if for example due to an accumultion of dirt or sediment within the heat'exchangers B4 and 85 the rate of heat transfer decreases. Accordingly, it is a further object of the apparatus shown in Fig. 3 to modify the pressure of the vapor within the exhaust conduit BI through positioning of the valve 43 to maintain the pressure within the header 6'! constant at all times.

Sensitive to the vapor pressure within the exhaust conduit BI 'is a Bourdon tube 88 pivotally connected to a movable valve member 88 of a pilot valve 10 similar to the pilot valve ii. Loading pressures established by the pilot 18 are transmitted through a pipe 1| to the chamber 48 of the averaging relay 36. Upon a change in pressure within the exhaust header 6|, for example an increase, the loading pressure established by the pilot 18 will decrease a proportionate amount of effecting, through the agency of the relay 35,'a proportionate increase in the fluid pressure transmitted through the pipe 4| to the diaphragm motor 42. The valve 43 will be positioned a proportionate amount in a closing direction, thereby changing the rate of flow of high pressure vapor to the prime mover i-in a direction to restore the pressure within the exhaust conduit 8| to the original value. Complete restoration will not occur, however, for it is apparent that for every position of the Bourdon tube 68 there is a definite rate of flow of high pressure vapor through the conduit 2, and accordingly to produce a change in the rate of flow through said conduit it is inherently necessary that the pressure within the exhaust conduit 6| vary in accordance therewith. The range in pressures within the exhaust conduit 6| necessary to produce a positioning of the valve 43 from one extreme position to the other may be varied to suit the individual characteristics of the system through proper design and arrangement of linkages, valve members, etc., as readily understood by those familiar with the art.

Connected to the header 61 and sensitive to the pressures therein is a Bourdon tube 12 pivotally connected to a movable valve member 13 of a pilot valve 14 similar to the pilot Loading pressures established by the pilot valve 14 varying in direct proportion to changes in pressure within the conduit 61 are transmitted through a pipe 15 to the standardizing relay 2|. Connected to the chamber 21 of the standardizing relay 2| is the pipe 34 for transmitting pressures to the chamber 35 of the averaging relay 36.

Upon a change in the vapor pressure within the header 61 from the desired value, for example a decrease, the valve member 13 will move downwardly effecting a proportionate decrease in the loading pressure established by the pilot valve 14. An immediate and proportional decrease in the pressure established by the standardizing relay 2| will result, which will be transmitted through pipe 34 to the chamber 35 of relay 36 causing a proportionate decrease in the pressure transmitted to the diaphragm motor 42 and effecting a positioning of the valve 43 in an opening direction an amount proportional to the decrease in pressure within the header 61. The resulting increase in rate of flow of high pressure vapor to the prime mover i will increase the pressure withinthe header 6|, thus producing a greater rate of heat liberation within the heat exchangers 64 and 65 which will in turn effect an increase in vapor pressure within the header 61. While the increase in pressure within the conduit 6| will effect a reverse positioning of the valve 43 through the agency of the Bourdon tube 68 and pilot valve 10, the pressure therein notwithstanding will progressively increase until the pressure within the header 61 is restored to the desired value due to the action of the standardizing relay 2| which, as hereinbefore explained, will upon a departure of the loading pressure within the chamber 28 from that corresponding to the desired vapor pressure effect a continuing change in the pressure transmitted to the diaphragm motor 42 until the desired value of pressure within the header 61 is restored.

In Fig. 4 we illustrate a modified form of a part of the apparatus shown in Fig. 3. Therein the pipe 34 is connected to a Bourdon tube 16, which is pivotally connected to the Bourdon tube 68 through a differential link 11. Pivotally connected to the mid point of the link 11 is a movable member 18 of a pilot 18. Loading pressures established by the pilot 18 are transmitted through the pipe 4| to the diaphragm motor 42. It is apparent that changes in pressure established by the standardizing relay 2| and transmitted through the pipe 34 will effect a positioning of the Bourdon tube 16 which will be effective for varying the fluid pressure transmitted to the diaphragm motor 42. Thus upon an increase in pressure within the pipe 34 in response to an increase in pressure within the header 61 the Bourdon tube 16 will be positioned in a counterclockwise direction increasing the loading pressure established by the pilot 18, which will position the valve 43 in a closing direction. Similarly increases in pressure within the Bourdon tube 68 will act to increase the loading pressure established by the pilot 19 and effect a positioning of the valve 48 in a closing direction. The arrangement of apparatus disclosed in Fig. 4 may, it is apparent, be substituted for the averaging relay 36 without affecting the functioning of the apparatus as a whole in any way whatsoever.

While in the embodiments of our invention shown in Figs. 1 and 3 the prime mover I may be provided with the usual governor to maintain the speed thereof below a predetermined limit, as will be apparent to those familiar with the art, it is sometimes advantageous to provide an arrangement wherein the diaphragm motor 42 will act to vary the governor setting. In this manner, through proper correlation of the various instrumentalities, the speed of the prime mover may be maintained within any desired range.

Referring to Fig. 5 we have shown a speed governor which may be of any desired construction arranged to vary the flow of vapor to the prime mover I. The governor 88 shown in the drawings is of the well known centrifugal type and comprises a worm 88A which through any suitable mechanism (not shown) is driven by the shaft of the prime mover I. Meshing with the worm 88A is a gear 8| secured to a vertical rotatable shaft 82 bifurcated at its upper end and pivotally supporting weighted members 83 and 84 urged inwardly at their lower ends by springs 85 and 86.

Carried by the upper ends of the members 83 and 84 through a suitable end bearing 81 is a shaft 88 pivotally connected to a lever 89 fulcrumed at 88 and operatng a valve 43A located in the conduit 2 supplying steam to the primemover The foregoing construction, which is old and well known and forms no part of our present invention operates as follows: The lower end of the weighted members 83 and 84 are positioned outwardly from the shaft 82 against the tension of the springs 85 and 86 proportional to the speed of the prime mover positioning their upper ends downwardly.

Such vertical positioning is transmitted to the valve 43A so that as the speed of the prime mover increases the valve 43A is progressively moved in a closing direction, decreasing the flow of vapor to the prime mover. To vary the ratio between speed changes and resulting changes in the rate of vapor flow, the lever 89, as shown,

maybe provided with a slot ill to any point or which the fulcrum 90 may be moved.

In accordance with our invention control the valve 43A by the speed governor is modified in accordance with the pressure of the vapor exhausted from the prime mover i. To this end we show in Fig. the diaphragm motor 42 pivottlly connected to the lever 89. As described, with reference to Fig. 1, the pressure transmitted to the diaphragm motor 2 increases upon an increasein exhaust vapor pressure or increase in diflerential pressure across selected stages of the prime mover i above predetermined values. With reference now to Fig. 5, such increases in pressure within the diaphragm motor 4! will act to position the valve 43A in a closing direction, thereby restoring the diflerential or the exhaust pressure, as the case may be, to the desired value. Conversely, upon a decrease in exhaust vapor pressure the diaphragm motor 42 will position the valve 43A in an opening direction, thereby increasing the flow of vapor to the prime mover .l.

Simultaneously with the control exercised by the diaphragm motor 12 the speed governor will likewise exercise control over movements 01' the valve 43A, so that changes in speed will be properly compensated for. It will be noted with re!- erenoe to Fig. 5 that movements of the diaphragm motor 42 in eflect act to vary the governor setting of the prime mover, rather than as shown in Fig. 1 to vary the rate of vapor flow independently of movements of the governor.

As shown in Fig. 6, if desired the shaft 88 may be provided with a slot 92 through which extends a pin 93 secured to the lever 89. with this arrangement so long as the speed 0! the prime mover i is within predetermined limits the speed governor will exercise no control over the rate of vapor flow to the prime mover. However, upon an increase in speed of the prime mover a predetermined amount above the desired value, or upon decrease in speed of predetermined amount below the desired value, the speed governor will exercise control over the rate of vapor flow. As will be apparent to those familiar with the art, by proper correlation of the various instrumentalities making up the mechanism, upon the predetermined maximum or minimum speed being reached the control exercised by the speed governor may, if desired, predominate over that exercised by the diaphragm motor 42 so that at all times the speed of the prime mover will be maintained within a predetermined range.

Ordinarily prime movers of the type described have their speed fixed by external means, such as the electric generator 4 shown in Fig. l driven by the turbine and connected to a line of constant frequency, that is, in parallel with other generators. Under these conditions the speed of the turbine cannot vary and the addition of vapor is then controlled directly to maintain the back pressure, or other condition of the exhaust vapor at the desired value. The prime mover carries only such load as is available from the vapor admitted thereto in accordance with the demand for exhaust vapor. In some instances, however, an external means for fixing the speed of the prime mover is not available and it is desirable to control the prime mover in terms of both load and exhaust pressure. In such instances our invention comprehends an apparatus whereby the prime mover may be controlled in terms of bothload and exhaust pressure. This enables such a prime mover to operate as an independent unit.

The total energy delivered to a prime mover in the form 01' vapor is partially transformed into mechanical energy and the remainder of the energy exists in the exhaust vapor in the form or heat energy. The part or the vapor which is transformed into mechanical energy within the prime mover may be termed "available energy and in an ideal turbine, having no losses, is equal to the mechanical load output of the prime mover. The total transformed energy is proportional to the total amount of steam passing through the prime mover and is a function or the pressure drop between inlet and outlet oi' the prime mover.

It is accordingly possible to change the mechanical load output oi! a prime mover by changing the pressure drop of the vapor while maintaining the amount constant; by changing the amount of vapor while maintaining the pressure drop constant; or by changing both the pressure drop and the amount 01' vapor.

There are in the present instance two variable factors, namely, variable demand for exhaust vapor and variable demand of mechanical load output. The first oi these-can be satisfied only by changing the amount of admitted vapor. The latter variable factor which normally can be satisfied by any of the above mentioned possibilities is in the present case satisfied by changing the pressure drop or the vapor in the prime mover, more particularly by changing the pressure of the admitted vapor. It is apparent that a change oi the amount of admitted vapor, owing to a change in demand for exhaust vapor, would aiIect the mechanical load output of the prime mover. This, however, is prevented by producing a corresponding change in the pressure drop through the prime mover to the end that the mechanical load output of the prime mover remains constant. This change in pressure drop is obtained by changing the vapor pressure in the inlet to the turbine.

In general, our apparatus acts therefore upon an increase in demand for exhaust vapor, for example, to increase the rate of vapor flow through the prime mover to satisfy the increase in demand and simultaneously to decrease the pressure drop across the prime mover to maintain the mechanical load output at the established value.

Conversely, upon an increase in mechanical load the apparatus acts to increase the pressure drop across the prime mover, to increase the mechanical output of the prime mover and simultaneously acts to maintain the how of vapor therethrough constant so that no increase in exhaust pressure is occasioned.

In Fig. 'l' we have shown a modified form of our invention whereby the flow of vapor to the prime mover i and the pressure drop therethrough is so regulated as to maintain any desired mechanical load output and any predetermined exhaust vapor pressure within limits of operation.

According to the embodiment of our invention illustrated the prime mover i is provided with a steam chest 95 to which vapor is supplied through the conduit 2 and in which is located a sectional type valve 96 for primarily regulating the amount of vapor admitted to the prime mover. The valve 43 is shown located in the conduit 2 and is primarily arranged to regulate pressure in chest 95 and accordingly the available energy of the vapor,

that is the energy available for conversion to mechanical energy.

An increase in demand for exhaust vapor with no change in mechanical load necessitates an opening of the valve 96. However, to avoid a change in the mechanical output of the prime mover the valve 43 must be positioned in a closing direction to decrease the heat energy available for transformation into mechanical energy. Similarly upon an increase in load, causing a decrease in speed 01' the prime mover without change in exhaust vapor demand the valve 43 must be positioned in an opening direction to increase the available energy and the valve 98 must be positioned in a closing direction to maintain constant the flow of vapor to the exhaust.

To provide for proper correlation of the movements of the sectional valve 96 with thoseof the valve 43 we show the former arranged to be positioned by a spring loaded diaphragm pressure sensitive motor 91. The diaphragm motor 42 actuating the valve 43 and thediaphragm motor 9i are sensitive to fluid pressures established within a pipe 98 to which they are connected. Upon an increase in pressure within the pipe 99 the sectional valve 96 is positioned in a closing direction, whereas the valve 43 is positioned in an opening direction.

Fluid pressures established within the pipe 98 are regulated to properly position the valves 43 and 96 in accordance with changes in exhaust vapor pressure through the agency of a pilot valve 99 positioned in accordance with changes in vapor pressure Within the exhaust conduit 3 and acting through a standardizing relay I00 and an averaging relay l 0|. Upon an increase in exhaust vapor pressure, for example, the loading pressure established by the pilot valve 99 will increase, causing an immediate and proportionate increase in the pressure transmitted to the diaphragm motors 42 and 91. As a result the valve 43 will be positioned in an opening direction whereas the valve 96 will be positioned in a closing direction. Closure of the valve 96 will serve to decrease the rate of flow of vapor through the turbine I and accordingly the amount discharged to the exhaust 3, thereby tending to restore the pressure therein to the desired value. Opening of the valve 43 will serve to increase the energy available in the vapor admitted to the turbine l, thereby compensating for the decrease in flow therethrough so that the mechanical output of the prime mover will remain constant.

After the immediate and proportionate change in position of the valves 43 and 96 they will continue to be positioned in a direction to restore the pressure within the exhaust 3 to the desired value through the action of the standardizing relay I00. That is the apparatus shown will first act to position the valves 43 and 96 and amount proportionate to the change in vapor pressure within the exhaust 3. Thereafter the valves 43 and 96 will continue to be positioned at a rate proportional to the amount of deviation of the vapor pressure within the exhaust 3 from that desired.

The valves 43 and 96 are likewise properly positioned in accordance with changes in mechanical load on the prime mover I through the agency of the governor arranged to position the movable valve member of a pilot valve I 02 establishing a loading pressure effective through the averaging relay l0! to vary the pressure within the pipe 98. When, for example, the speed oi. the prime mover l decreases, indicating an increase in mechanical load, the loading pressure established by the pilot valve I02 increases acting to open the valve 43, thereby increasing the energy available and closing the valve 93 to properly compensate for the otherwise increase in rate of vapor flow through the prime mover l which would affect the pressure in the exhaust 3.

Due to the action of the standardizing relay I00 it is apparent that ultimately the control from exhaust vapor pressure will predominate over that from mechanical load, and that it due to the divergence in demand for exhaust vapor and mechanical load a point of equilibrium cannot be establised the control system will operate to satisfy the demand for exhaust vapor at the expense of the mechanical load. It is apparent, however, that if desired the control system can be arranged so that ultimately any requirement for mechanical load will be satisfied regardless and at the expense of accurate control of the exhaust vapor pressure. In this arrangement the loading pressure established by the pliot I02 would operate the valves 43 and 96 through the standardizing relay I09, whereas the pilot valve 99 would operate solely through the averaging relay I0 I. The condition wherein it is impossible to satisfy both the demand for exhaust vapor and mechanical load is, of course, exceptional and under ordinary operating conditions the control system illustrated in Fig. 7 will operate so that a predetermined exhaust pressure is maintained and the speed of the prime mover regulated so that any desired mechanical load may be carried thereby.

It will, of course, be understood that the action of the pilot valves and other parts of the control system may be so reversed that upon failure of the supply of control pressure the spring of the valve 43 would cause the valve to go to a closed or minimum position, thus preventing overloading the turbine or preventing raising the pressure in the exhaust header unduly. This refers particularly to the embodiments of Figs. 1, 3 and 4. Furthermore, a protection arrangement employing the pilot 59 of Fig. 1 may be included in the showing of Fig, 3 with the pilot valve action reversed so that its control pressure couldbe applied to the relay 36 of Fig. 3 in the chamber below chamber 40.

While we have described certain particular embodiments of our invention, it is obvious that various modifications and rearrangements may be made without departing from the spirit and scope of the invention. Accordingly reference should be had to the appended claims rather than to the description to determine the scope of the invention.

What we claim as new, and desire to secure by Letters Patent of the United States, is:

1. In combination with a power producing or utilizing apparatus to which a fluid of relatively high energy is admitted and from which a fluid of relatively low energy is exhausted, means positioned in accordance with the pressure of said exhaust fluid, a pilot valve actuated by said last named means for establishing a fluid pressure proportional to the magnitude of said exhaust fluid, a standardizing relay for establishing initial changes in a second fluid pressure proportional -to changes in said flrst fluid pressure and there after a continuing change untilthe first fluid pressure attains a predetermined value, means sensitive to the pressure of the energy fluid at a point in said apparatus, means actuated by said last named means for establishing a third fluid pressure, a diflerential relay for establishing a fourth fluid pressure in accordance with the magnitude of the second and third fluid pressures,

and regulating means of the high energy fluid positioned by the fourth fluid pressure.

2. In combination with a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, means for establishing a first fluid pressure in accordance with the exhaust pressure, means for establishing a second fluid pressure in accordance with the dlflerence in vapor pressure at I a plurality of points in said prime mover, means for establishing a third fluid pressure in accordance with the first and second fluid pressures, and regulating means of the rate of flow of the high pressure fluid to the prime mover under the control of the third fluid pressure.

3. In combination with an electric generator driven by a prime mover to which vapor is ad-- mitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, means positioned in accordance with the exhaust pressure, a pilot valve having a movable member for establishing a fluid pressure proportional to the position of said movable member, a member connecting said movable member to said first named means whereby a fluid pressure is produced proportional to the exhaust pressure, means sensitive to the power output of said generator, means actuated by said last named means for modifying the position of said movable member when the power output attains a predetermined magnitude and regulating means of the high pressure vapor under pressure.

4. In combination with an electric generator driven by a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, means sensitive to the exhaust pressure, a first member positioned by said means, means sensitive to the power output of said generator, a second member periodically positioned by said last named means when the power output attains a predetermined value, means for establishing a first fluid pressure in accordance with the position of the first and second members, and regulating means of the high pressure vapor under the control of the fluid pressure.

5. In combination with an electric generator driven by a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, means positioned in accordance with the exhaust pressure, a pilot valve having a movable member positioned by said means for establishing a. fluid pressure in accordance with the exhaust pressure, regulating means of the rate of flow of the high pressure vapor to said prime mover positioned by said fluid pressure to maintain said exhaust pressure at a predetermined value, means sensitive to the power output of said generator, and means under the control of said last named means for periodically positioning said movable member a predetermined amount when the power output attains a predetermined value.

6. In combination with an electric generator driven by a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, means for normally regulating the rate of flow of high pressure vapor to the prime mover to maintain said exhaust pressure at a predetermined value, and means for periodically decreasing the rate of flow of high pressure vapor when the power output of said generator attains a predetermined value.

the control of said fluid 7. In combination with an electric generator driven by a prime mover to which vapor is admltted at a relatively high pressureand exhausted therefrom at a relatively low pressure, means for establishing a first fluid pressure in accordance with the exhaust pressure of the vapor, means for modifying said first fluid pressure when the power output of the generator attains a predetermined value, means for establishing asecond fluid pressure when the difference in pressure of the vapor at predetermined points in said prime mover attains a predetermined value, a differential relay for producing a third fluid pressure proportional to the sum of said first and second fluid pressures, and regulating means of the rate of flow of high pressure vapor to the prime mover actuated by the third fluid pressure.

8. In combination with a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, an evaporator heated by said exhaust vapor and generating a second vapor, means for establishing a first fluid pressure in accordance with the pressure of said second vapor, means for establishing a second fluid pressure in accordance with the pressure of the exhaust vapor, means for establishing a third fluid pressure in accordance with the relationship between the flrst and second fluid pressures, and regulating means of the high pressure vapor actuated by the third fluid pressure.

9. In combination with a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, an evaporator heated by said exhaust vapor and generating a second vapor, means for establishing a first fluid pressure in accordance with the pressure of said second vapor, a standardizing relay sensitive to said first fluid pressure for initially establishing changes in the second fluid pressure proportional to changes in the first fluid pressure and thereafter producing a continuing change in the second fluid pressure until the first fluid pressure is restored to a predetermined value, means for establishing a second fluid pressure in accordance with the pressure of the exhaust vapor, means for establishing a third fluid pressure in accordance with the algebraic sum of the first and second fluid pressures, and regulating means of the rate of flow of the high pressure vapor under the control of the third fluid pressure.

10. In combination with a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, an evaporator heated by said exhaust vapor and generating a second vapor, means sensitive to the pressure of the second vapor, means under the control of said last named means for producing initial changes in the rate of flow of the high pressure vapor to the prime mover proportional to changes in the exhaust pressure, and in a direction tending to restore said exhaust pressure to a predetermined value and for thereafter producing a continuing change in the rate of flow of the high pressure fluid until said exhaust vapor pressure is restored to the predetermined value; and means for modifying the control of the rate of flow of high pressure vapor in accordance with the pressure of the exhaust vapor.

11. In combination with a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively iow pressure, a governor therefor, means for establishing a first fluid pressure in accordance with the exhaust vapor pressure, means sensitive to said first fluid pressure for establishing changes in a second fluid pressure proportional to changes in the first fluid pressure and for continuously modifying said second fluid pressure upon departure of the exhaust pressure from a predetermined value; and means actuated by said second fluid pressure to adjust the speed setting of said governor.

12. In combination with a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, a governor therefor, means for establishing a first fluid pressure in accordance with the exhaust vapor pressure, means for establishing a second fluid pressure in accordance with the difference in vapor pressure across a predetermined portion oi said prime mover, means for producing a third fluid pressure proportional to the algebraic sum or the flrst and second fluid pressures, and means actuated by the third fluid pressure to adjust the speed setting of said governor.

13. The combination with a prime mover of two valve means for primarily regulating the pressure and the amount respectively of vapor supplied the prime mover, means for producing a first fluid pressure in accordance with the mechanical load on the prime mover, means for producing a second fluid pressure in accordance with the pressure of the vapor exhausted from the prime mover, means for producing a third fluid pressure in accordance with the sum of the first two fluid pressures, and means for simultaneously positioning the two valve means actuated by said third fluid pressure.

14. In combination with a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, means for establishing a first fluid pressure in accordance with the exhaust pressure, means for establishing a second fluid pressure in accordance with the pressure of the vapor at a point in said apparatus, means for establishing a third fiuid pressure in accordance with the algebraic sum of the first and second fluid pressures, and regulating means of the rate of flow of the high pressure vapor to the prime mover under the control of the third fluid pressure.

15. In combination with an electric generator driven by a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, means for normally regulating the rate of flow of high pressure vapor to the prime mover to maintain said exhaust pressure at a predetermined value, and means for decreasing the rate of flow of high pressure vapor only when the power output of the generator attains or exceeds a predetermined maximum value.

16. In combination with an electric generator driven by a prime mover to which vapor is admitted at a relatively high pressure and exhausted therefrom at a relatively low pressure, means sensitive to the exhaust pressure, a first member positioned by said means, means sensitive to the power output of said generator, a second member periodically positioned by said last named means, means for establishing a first fluid pressure in accordance with the position of the first and second I members, and regulating means of the high pressure vapor under the control of the fluid pressure.

17. The combination with a prime mover of two valve means for primarily regulating the pressure and the amount respectively of vapor supplied the prime mover, means for producing a fluid pressure in accordance with the mechanical load on the prime-mover, and'means for simultaneously positioning the two valve means actuated by said fluid pressure.

18. The combination with a prime mover of two valve means for primarily regulating the pressure and the amount respectively of vapor supplied the prime mover, means sensitive to the mechanical load on the prime mover, and means for simultaneously positioning the two valve means under the control of said last named means.

19. The combination with a prime mover of two valve means for primarily regulating the pressure and amount respectively of vapor supplied the prime mover, means for producing a fluid pressure in accordance with the pressure of the vapor exhausted from said prime mover, and means for simultaneously positioning the two valve means actuated by said fluid pressure.

20. The combination with a prime mover of two valve means for primarily regulating the pressure and the amount respectively of vapor supplied the prime mover, means sensitive to the pressure of the vapor exhausted from said prime mover, and means for simultaneously positioning the two valve means under the control of said last named means.

21. In combination with a prime mover to which vapor is admitted at a relatively high pres sure and exhausted therefrom at a relatively low pressure, a governor therefor, means for establishing a first fluid pressure in accordance with the exhaust vapor pressure, means for establishing a second fluid pressure in accordance with the pressure of the vapor at a point intermediate the supply and exhaust, and means under the joint control of the first and second fluid pressures for adjusting the speed setting of said governor.

PAUL S. DICKEY. JACK F. SHANNON.

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