US2345297A - Hydraulic governing system for prime movers - Google Patents

Description

March 28, 1944. A. F. scHwENDER 2,345,297

HYDRAULIC GOVERNING SYSTEM FOR PRIME MOVERS liled Dec. 5, i941 INVENTOR RNTHoNyEScHweNoNH Patented Mar. 28, 1455?@4 HYDRAULIC GOVERNING SYSTEM FOR PRIME MOVERS Anthony F. Schwendner, Ridley Park, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 5, 1941, Serial No. 421,726

10 Claims.

The invention relates to hydraulic governing of prime movers, for example, elastic-huid turbines, and it has for an object to provide improvements in apparatus of this character wherein speed-responsive forces are transformed into iiuid pressure such that an increase in force is accompanied by a decrease in transformed iiuid pressure and vice versa.

In accordanceA with the present invention, the transformer is designed to give a pressure which changes in inverse relation to the governing force, each servmotor moving its valve in a closing direction in response to decrease in transformed pressure, to provide for safer operation and for simplification of certain of the protective or controlling devices. If reduction in transformed pressure is accompanied by movement of the admission valve in a closing direction, it will be apparent that the turbine will be inherently safer and certain of the protective or controlling devices may be substantially simplified. The extent to which the admission valve opens may be controlled by limiting the maximum transformed pressure, and reduction in transformed pressure due to leakage or to a controlling device results in movement oi the admission valve in a closing direction. Consequently, the controlling devices, such as the load limit, emergency governing, and discharge or back pressure devices, may be largely ycomprised by simple valves associated with the transformed fluid pressure space.

A further object of the invention is to provide means deiining a space wherein fluid under pressure is maintained in such a manner that the pressure varies in inverse relation to the speed, the pressure being used to control the admission valve or valves of a turbine, together with one or more valves operative in response to characteristics, other than speed, for controlling the admission of steam to the turbine.

These and other objects are eiected by the 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:

Fig. 1 is a side elevational View of a turbine having the improved governing system applied thereto;

Fig. 2 is an enlarged detail View of the transformer cup valve;

Fig. 3 shows a-modifiedv form ofthe governing system; and,

Fig. i is an enlarged detail view of the leak-off device for varying the extent of speed correction.

Referring to the drawing, there is shown a turbine 1 provided with a motive fluid supply passage 8 and .an admission valve or valves 9 (one being shown by way of example) and a throttle valve I0 arranged in series in the passage. The admission valve 9 is moved in opening and closing directions by means of the servomotor, at I l. The throttle valve is normally held open by the pressure-responsive device, at I2.

Movement of the pilot valve of the servomotor, at II, is initiated by a pressure-responsive device, at i3, including a pressure abutment or piston area I4 and a housing I5 providing a pressure chamber I5 for the area. The servomotor is so arranged.l and connected to the admissionfvalve 9 that decline in pressure in the chamber I6 brings about movement of the valve in a closing direction and vice versa.

Fluid under transformed pressure is supplied by the transformer, at I8, to the space, generally indicated at I9, defined by the pressure chamber I6 and the conduit system 2i! connected thereto. The transformer also includes an oriiice 2| for supplying fluid from a suitable pressure source to the space, at I9, and means, at 22, for controlling the escape of fluid from the space and, therefore, determining the magnitude of pressure in the space.

The escape means, at 22, is subject to a speedresponsive or governing' force and to a fluid pressure force dependent upon the pressure in the space, at I9, acting together in opposition to the force of the spring 23 to control escape of fluid from the space. WithY this arrangement, if the turbine load changes, the speed-responsive force changes, thereby upsetting the balance of forces acting on the means, at 22, and, in consequence the transformed pressure in the space, at I9, changes in the opposite sense until the balance is restored.

While the means, at 22, may be embodied in diiferent structural arrangements, as shown, it is constituted by one of the cup valve type, it embody-ing a cup valve 25 in covering relation with respect to an escape port 26 for the transformed pressure space, at I9. The cup valve has a rim 21 whose sharp edges 28 cooperates with the surface 29 bounding the discharge end of the port 26 to define the escape orice.

Governing or speed-responsive force is applied to the cup valve 25 in suchv a direction as to tend to increase the escapel ofD fluid to reduce the pressuren the space, at I9; the opposing y force of the spring 234 tends to increase such pressure; and the force of pressure in the space is applied to the cup valve in the same direction as the governing or speed-responsive force. Hence, if balance of these forces is disturbed, due to change in the speed responsive force pursuant to change in load, the transformed pressure will change until the force thereof acting on the cup valve restores balance.

The area of the cup valve subject to transformed fluid pressure may consist; of an area. 30 bounded by the flange 21 or by that area and an additional area at 3l formed on structure attached to the cup valve, the provision of the additional area being necessary where speed compensation is effected, as hereinafter described.

The speed-responsive or governing force may be provided in any suitable manner. For example, in Fig. l, the turbine drives impeller apparatus, at 32, for developing iluid pressure which varies substantially as the square of the speed of the turbine, this fluid under pressure being supplied to the space, at 33, including the chamber 34 bounded in part by the abutment 35 supported by the bellows 36 and presenting a pressure area 31 to the chamber. The impeller fluid pressure, therefore, exerts force on the abutment 35 in opposition to that of the load spring 38. The force of the load spring may be adjusted by means of a speed changer, at 39.

Speed-responsive force is transmitted mechanically from the abutment 35 to the cup valve 25 in any suitable manner. To this end, there is provided a thrust rod construction 40 connected to the cup valve, the arrangement being such that the thrust force of the rod is opposed by that of the spring 23.

In Fig. 3, there is shown a modified form wherein, instead of the force varying as a square of the speed being derived from fluid pressure, such force is obtained from flyweights.

With the arrangements so far described, an increase in load is accompanied by an increase in transformed pressure in the space, at I9, and vice versa. Therefore, the servo-motor, at II, is arranged to move the admission valve 9 in an opening direction in response to increase in transformed pressure and vice versa. As the steam admission valve 9 is moved in an opening direction by increase in transformed pressure pursuant to increase in load and vice versa, it becomes a relatively simple matter to associate other controlling and protective devices with the transformed pressure space, at I9. The load carried by the turbine may be limited by limiting the pressure which may be attained in the space; the transformed pressure may be controlledV in response to some other operating characteristic such as a discharge or back pressure; failure of transformed pressure for any reason results in closing of the admission valve; and an emergency or overspeed governor is readily associated with the system, such a governor responding directly to overspeed to close the throttle valve and causing the transformed pressure to drop to close the admission valve.

To limit the load carried by the turbine, there is provided a load limit device, at 43, in the form of a loaded relief valve which opens in response to pressure in the transformed pressure space at I9. Accordingly, such space has an escape port 44 covered by a cup valve 45 having an area 46 exposed to transformed pressure, and a spring 41 exerts force on the valve to close it against the force of transformed pressure exerted thereon. The closing force of the spring may be varied by any suitable adjusting means 48.

Assuming that the speed changer, at 39, is adjusted for a pressure of 15 pounds in the transformed pressure space, at I9, for synchronizing and that the pressure in such space is 55 pounds for full load, then there is involved a pressure difference of 40 pounds for the load range. If the spring 41 holds a pressure of 35 pounds in the space, at I 9, it will be apparent that the transformed pressure cannot be increased beyond this value by adjustment of the speed changer, at 39. In other words, the apparatus, at 43, serves to limit the lo-ad carried by the turbine.

A discharge pressure regulating valve is shown, at 50, this apparatus including an escape port 5| for the transformed pressure space, at I9, and a valve 52 in covering relation with respect to the port. A spring 53 exerts closing force on the valve against opening force exerted thereon by a transformed fluid pressure acting on the cup valve area 54. A turbine discharge passage, for example, a back pressure pipe or conduit 55 connected to the turbine exhaust 56, communicates with the pressure chamber 51 enclosed in part by the diaphragm 58. While the pipe 55 is shown as being the usual turbine exhaust one, so far as the present invention in its broader aspects is concerned, this pipe may be any suitable pipe for discharging steam from the turbine, and the word "discharge is used to give this significance. A spring 59 exerts force on the diaphragm in opposed relation to that of the force due to steam pressure applied thereto. A stem construction 6I carried by the diaphragm cooperates with suitable structure 62 unitary With the valve 52. A threaded follower 63 provides for adjustment of the spring 59.

If the turbine discharge or back pressure should increase, the load of the spring 53 on the cup valve 52 would be reduced to relieve pressure in the space, at I 9, and the servo-motor would operate in consequence of such pressure reduction to move the admission va1ve'9 in a closing direction to restrict the supply of steam to the turbine.

On the other hand, if the discharge or back pressure should decrease, then the load of the spring 53 would be increased and the contrary operation would take place, the turbine admission valve being opened Wider to provide for increased steam flow to limit the decrease in back pressure.

Overspeed or emergency protection is secured by operation of the usual trip device 65 carried by the turbine rotor, operation of the trip device resulting in opening of the spill valve 56 vand release of pressure in the space, at 61, supplied with fluid from a suitable source by means of an orifice 68. The space 61 includes a pressure chamber 69 of the pressure-responsive device, at I2, the chamber being dened by a cylinder 10 and a piston 1I connected to the throttle valve I 0, the arrangement being such that pressure acting on the piston is normally effective to hold the valve open. Upon operation of the trip device 65, pressure in the space 61 is released and biasing means, for example, the spring 12, effects quick closing of the throttle valve.

In addition to closing the throttle valve, operation of the overspeed-responsive means brings about closing of the admission valve 9. Hence, the space, at 61, also includes the chamber 14 defined by the cylinder 15 andthe piston 16.

Normally, pressure in the space, at 6l, acts on the piston 'I6 to keep the valve 'II closed in relation to the escape port I8 of the transformed pressure space, at I9; however, withV release of pressure in said space, the spring l, aided by the force of transformed fluid pressure applied to the cupvalve area 89, opens the valve and the pressure in the space, at i9, drops and the servo-motor, atII, operates in consequence to close the admission valve 9.

Thus, it will be seen that the devices for exerting controlling effects in response to op-erating characteristics, other than speed or load, operate to supersede the governor in controlling or modifying the pressure in the space, at I9. Limitation of load carried by the turbine is effected by adjustment of the valve 45 to open at a desired pressure regardless of any tendency of the governor to increase the pressure beyond that point. Within the setting of the load limit device, at 43, the discharge or back pressure regulator, at 50, operates to keep the turbine discharge or back pressure within a narrow range of variation; and, in so doing, it supersedes the governor to control the pressure in the space, at I9, such that the admission of steam to the turbine is increased or decreased to limit back pressure variation. This means that the governor is effective to control the steam admission as long as the load carried does not exceed the amount nxed, as long as the turbine does not overspeed to a predetermined extent, and as long as the discharge or back pressure is Within the limits of its regulation; but, whenever the load carried tends to exceed the predetermined amount, the turbine overspeeds, r

or the discharge or back pressure tends to change, devices responsive to these operating characteristics become effective and supersede the governor in controlling the pressure in the space, at I9.

As hereinbefore indicated, the transformer cup valve 25 has an additional pressure area 3| to provide for speed compensation due to load change. Accordingly, in Fig. 1, the cup valve has a stem 82 to which is attached the disc B3, which, with the bellows element 8d, define the pressure chamber 85 to which the area 3l is exposed. A passage 8l connects the space, at I9, to the chamber 86 and an airbell or accumulator 88 is connected to the chamber. A suitable orifice, at SQ, preferably of the viscous type, is arranged in the passage 8l and it preferably acts in conjunction with the accumulator 88 to provide a lagging of change in pressure acting on the area di in relation to the change in pressure acting on the cup valve area Sil. As a result, with change in load, the gradual increase or decrease in pressure in the chamber 86 is responsible for speed correction. If correction is complete then the governor system is, in effect, isochronous.

For speed-compensated operation, assuming an increase in load, there is a temporary decrease in speed and decrease in the speed-responsive force, with the result that the transformed fluid pressure must increase to secure equilibrium of forces acting on the cup valve. The increase in transformed fluid pressure, due to the effect of the orifice, at 99, and the accumulator 88, is gradually applied to the pressure area 3I to increase further the transformed fluid pressure to Aincrease the steam admission and turbine speed to compensate for speed change due to the increase in load. For full compensation, the area -3I'is so chosen and the orifice, at 90, is adjusted for such a pressure in the chamber 8B that the speed-correcting process continues until thefluid pressure forces acting on the cup valve are balanced with the resultant of the spring forces in balance with the governing force, at Which time,l the turbine will be operating at the increased load Yand at the-same speed it had before the change in load. Preferably, as shown, the pressure areas 39 and 3l are equal, in which event, for full compensation, the orifice, at 90, would be adjusted such that the pressure in the chamber 86 may reach the same value as the transformed fluid pressure.

If there is a decrease in load, the contrary operation takes place, the governing force increasing and the transformed fluid pressure decreasing with a temporary increase in speed due to the change in load. The pressure applied to the area 3I gradually decreases to secure full or partial correction of the speed due to change in load.

I prefer to use an orifice, at 90, of the viscous type and arranged as shown to avoid inaccuracies in operation because of viscosity changes and to provide for easier, accurate, and more .certain adjustment. Flow through `a viscous orice varies directly with the pressure drop, whereas, with the ordinary orice it varies as the square root ofthe pressure drop, Therefore, because of this difference, construction and adjustment are simplified. The arrangement comprises a cylinder ill-.having its lower end connected to the transformed pressure-space, at I9, and having its upper end connected to the drain space 92. The conduit Aor passage 8l connects an intermediate point, of the cylinder 9| with the pressure chamber 8B. Within the cylinder, there is disposed a loosely-fitting cylindrical plug 93 having a peripheral spiral groove 9H. The plug is adjustable lengthwise of the cylinder by any suitable means, for example, the threaded connection 95,

to vary the relative lengths of the portions of the grooves 94 between the space, at I9, and the point of connection of the passage 81 and between the latter and the drain space 92. The operation is somewhat like that of a potentiometer. The resistance between the space, at I9,

and the drain' space 92 is constant irrespective of adjustment of the plug and so is the pressure drop for any given pressure in the space, at I9, and the resistance between the space and Ythe connection 81 and between the latter and the drain space 92 are proportional to the intervening lengths of the spiral groove. Hence, the pressure in the bellows chamber 88 may be easily adjusted in relation to the transformed pressure 'to vary the extent of compensation.

While the invention has been shown in several forms, it will be obvious to those skilled rin the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and it is desired, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims. i

What is claimed is:

l. The combination with a prime mover having a motive fluid valve, of means providing an enclosed space and including a pressure-responsive device controlling the valve so that, with a reduction in liquid pressure in the space, the valve is moved in a closing direction and vice versa; means providing an escape port for the space; anescape valve in covering relation with respect' to the escape 'port and presenting an area subject tospace pressure; means for biasing the escape valve against the force of liquid pressure -move the escape valve in an opening direction against the force of said biasing means; a pressure-limiting valve for the space; ,means for exerting closing force on the last-named valve; and 4means for varying the closing force to vary the maximum pressure in said space.

2.. The .combination with a prime mover hav.- ing a motive fluidvalve, of means providing an enclosed space andincluding a pressure-respon- -sive device controlling the valve so that, with, a reduction in liquid pressure in the space,l the valve is moved in a Vclosing direction andvice versa; means providing an escape port for the space; an escape valve in covering relation with respect to the port and presenting an area subject to space pressure; means for biasing the escape valve against the force of liquid pressure applied thereto from the space to restrict the escape of liquid from the latter; a speed governor operated by the prime mover and cooperating with said escape vvalve to move the latter in an .opening direction with an increase in speed; a pressure-limiting valve for the space; means for openingvand closing the last-named valve and including a pressure area subject to space pressure and a spring for opposing the force of fluid Apressure applied to the area; and means for varying the spring force to vary the maximum space pressure. -3. In a prime mover having a motive iluid valve, means providing an enclosed space and in- .'cluding a pressure-responsive device for controlfling the valve so that, with a reduction in liquid pressure, the valve is moved in a closing direction and Yvice versa; means including an orifice for supplying liquid from a suitable pressure source to said space; the means providing the enclosed space having an escape port; a valve member in covering relation with respect to the port and cooperating With the latter to provide an escape oriiice; the valve member presenting an area subject to space pressure; biasing means for exerting force on the valve member in opposition to the force of space pressure exerted on the pressure area thereof; a speed governor responsive to increase in speed of the prime mover for moving said valve member in an opening direction against the force of said biasing means; a pressure-limiting valve for said space; means for opening and closing the last-named valve and including a pressure area subject to space pressure and a spring for opposing the force of iluid vpressure applied to the area; and means for vary- -ing the spring force to vary the maximum space pressure.

. 4. In a prime mover having a motive uid valve, means providing an enclosed space and including a pressure-responsive device for controlling'the valve so that, with a reduction in liquid pressure, the valve is moved in a closing direction and vice versa; means including an orice for supplying liquid from a suitable pressure source to said space; the means providing the enclosed space having an escape port; a valve member in covering relation with respect to the port-and cooperating with the latter to provide an escape orice; the valve member presenting an area subject to space pressure; biasing means for exerting force on the valve member in opposition to the force of space pressure exerted on the pres- ,sureY area thereof; means responsive to increase in speed of the prime mover for exerting force on the valve member to move the latter iny an opening direction against the force of the biasing means; means providing a second pressure area for the valve member facing oppositely to the rstpressure area thereof; means providing `a pressure chamber for the second pressure area;'

a passage connecting said space and saidpressure chamber and including an orifice; said presnsure chamber and the portion of the passage between the latter and the passage orifice providing a second pressure space; and an accumulator communicating with said second pressure space.

5. In a prime mover having a motive Afluid valve, means providing an enclosed space and including a pressure-responsive device for controlling the valve so that, With a reduction in liquid pressure, the valve is moved in a closing direction and vice versa; means including an orice for supplying liquid from a suitable pressure source to said space; the means providing the enclosed space having an escape port; a valve member in covering relation with respect to the vport and cooperating With the latter to provide an escape orice; the valve member presenting an area subject to space pressure; biasing means for exerting force on the valve member in opposition to the force of space pressure exerted on the pressure area thereof; means responsive to increase in speed of the prime mover for exerting force on the valve member to move the latter in an opening direction against the force of the biasing means; means providing a second pressure area for the valve member facing oppositely to the first pressure area thereof; means providing a pressure chamber for the second pressure area; a passage connecting said space and said pressure chamber and including an oriiice; said pressure chamber and the portion of the passage between the latter and the passage orifice providing a second pressure space; an accumulator communicating with said second pressure space; and means providing a variable leakoff orifice communicating With said second pressure space. y

6. 'I'he combination with a prime mover having an admission valve and a discharge connection for motive iluid, or" means providing an enclosed space and including a pressure-responsive device controlling the valve so that, with a reduction in fluid pressure in the space, the valve is moved in a closing direction and vice versa; means responsive to prime mover speed for maintaining fluid under pressure in said space such that, as the load is increased, the pressure is increased and vice versa; means providing an escape port for said space; a cup valve arranged in covering relation with respect to the discharge end of the port; an abutment having a pressure area; means providing for the application of discharge connection pressure to the pressure area; means for utilizing movement of the abutment in response to increasing discharge connection pressure to open the cup valve; and biasing means opposing opening of the cup valve and the force of discharge connection pressure applied to said abutment.

7. The combination With a prime mover having an admission valve and a discharge connection for motive iluid, of means providing an enclosed space and including a pressure-responsive device .controlling the valve so that, with a reduction in uid pressure in the space, the valve is moved in a closing direction and vice versa; means responsive to prime mover speed for maintaining fluid under pressure in said space such that, as the load is increased, the pressure is increased and vice versa; means providing an escape port for said space; a cup valve arranged in covering relation with respect to the discharge end of the port; a first spring for exerting closing force on the cup valve; a pressure regulator including an abutment having a pressure area, a second spring for exerting force on the abutment, means providing for the application of discharge connection pressure to the pressure area to apply force to the abutment in opposition to said second spring; means for utilizing movement of the abutment in response to increasing discharge connection pressure to open the cup valve against the force of its spring; and means for adjusting the force exerted by the second spring on the abutment in order to vary the pressure maintained in the discharge connection.

8. The combination with a prime mover having a motive fluid supply passage and a throttle valve and an admission valve arranged in series in the latter, of means providing a rst enclosed space and including a pressure-responsive device controlling the admission valve so that, with a reduction in fluid pressure in the space, the valve is moved in a closing direction and vice versa; means responsive to prime mover speed for maintaining fluid under pressure in said space such that, as the load is increased, the pressure .is increased and vice versa; biasing means for exerting closing force on the throttle valve; an escape valve for the iirst enclosed space; biasing means for exerting opening force on the escape valve; means providing a second enclosed space and including devices for maintaining the throttle valve open and the escape valve closed against the forces of the biasing means; means including an orifice for Supplying fluid from a suitable pressure source to said second space; and means responsive to overspeeding of the prime mover to relieve the pressure in said second space to bring about closing of the throttle valve by its biasing means and opening of the escape valve by the biasing means of the latter.

9. The combination as claimed in claim 3 wherein the governor includes a spring and means is provided for adjusting the latter.

l0. The combination as claimed in claim 3 with means responsive to change in space pressure pursuant to speed change due to load change to effect further adjustment of the space pressure in order to correct to a desired extent the prime mover speed for load change.

ANTHONY F. SCHWENDNER.

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