US2949122A

US2949122A - Hydraulic system for steam turbine

Info

Publication number: US2949122A
Application number: US390472A
Authority: US
Inventors: Clarence E Kenney
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1953-11-06
Filing date: 1953-11-06
Publication date: 1960-08-16
Anticipated expiration: 1977-08-16

Description

Aug. 16, 1960 c. E. KENNEY 2,949,122

HYDRAULIC SYSTEM FOR STEAM TURBINE 2 Sheets-Sheet 1 Filed Nov. 6, 1953 klirilla, 5 ll- Aug. 16, 1960 Q KENNEY 2,949,122

HYDRAULIC SYSTEM FOR STEAM TURBINE Filed Nov. 6, 1953 2 Sheets-Sheet 2 HYDRAULIC SYSTEM FOR STEAM TURBINE Clarence E. Kenney, Hartland, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Nov. 6, 19-53, Ser. No. 390,472 2' Claims. Cl. 137-17 This invention relates generally to a hydraulic system for supplying liquid under pressure to a machine and more specifically to an improved system in a steam turbine for supplying high pressure oil for operating auxiliary hydraulic systems such as a governing system, :and low pressure oil for lubrication.

It has heretofore been proposed to supply high and low pressure oil to a prime mover such as a steam turbine by providing a main centrifugal pump directly coupled to the prime mover shaft. A portion of the discharge from the main pump which is at a high pressure is supplied to the governing system of the turbine and to a hydraulic turbine; the remainder of the discharge of the main pump is bypassed around the hydraulic turbine and passes through pressure reducing means to an oil cooler and then supplied to bearings of the prime mover. The hydraulic turbine derives its energy from the pressure differential between the high pressure in take from the main pump and low pressure discharge of oil from the hydraulic turbine. A low pressure pump is directly connected to and driven by the hydraulic turbine. The low pressure pump takes suction from a reservoir and dischargesto the intake of the main pump.

The nature of the present invention resides in the provision of an improved hydraulic system for steam turbines whereby none of the high pressure fluid supplied by the main pump to the hydraulic turbine bypasses the hydraulic turbine to pass through pressure reducing means for low pressure bearing lubrication. Instead, the dischange of the low pressure pump is utilized for bearing lubrication with the hydraulic turbine discharging to the intake of the main pump. Therefore, more of the energy derived from the drop in pressure from the high pressure produced by the main pump to the low pressure required for lubrication, is utilized to operate the hydraulic turbine and low pressure pump, and none of this energy is wastefully dissipated by bypassing the hydraulic turbine and throttling for lubrication purposes as has heretofore been done.

It is therefore an object of the present invention to :more efficiently utilize the available energy represented by the pressure drop between the high value required for the governing system and hydraulic turbine and the low value required for lubrication.

Another object of the invention is to provide a sys-.

'tem for supplying liquid to a machine 'at two different pressures that is more economical than prior known ;systems.

Another object of the invention is to permit the use of smaller piping to and from the main turbine pedestal than has heretofore been used in prior known systems. Another object of the invention is to provide an improved dual fluid system for supplying liquid to a :machine at two different pressures.

Objects and advantages other than those set forth above Will be apparent from the following description ice when read in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic view partly vin section of a system embodying the invention; and

Fig. 2 is a view similar to Fig. 1 showing a second embodiment.

Referring to the drawings, and first to Fig. 1, this invention is illustrated as applied to amachine such as a steam turbine indicated generally at 1 and having a shaft 2, a lubrication system to which oil is supplied under pressure, and a servomotor indicated generally at 4 in the governing system to which oil 'is' supplied under pressure through-a conduit 5. As is well known, the governor is arranged to control a servomotor which may be in the form of a piston 6 slidably arranged in cylinder 7, for positioning a turbine inlet control valve 8. Motive fluid is supplied to the turbine 1 through an inlet conduit and the speed and output of the turbine are controlled by regulation of the valve 8 through the servomotor '4. Any other suitable known type of governing system for turbines may be substituted for the governor and servomotor 4.

Oil for lubricating the turbine and actuating the governing system is supplied from a reservoir 12, which is customarily located at a level below the turbine 1 so that the oil supplied to the bearings and other components may conveniently be drained back to the reservoir 12 by gravity. The oil may be a petroleum product or any other suitable known liquid having lubricating properties. The turbine lubricating system is drained by means of a conduit 13. i

In accordance with the invention, a main oil pump, indicated generally at 14, may be driven by any suitable prime mover but is preferably directly coupled to an extension 15 of the turbine shaft 2. As shown, this main oil pump -14 comprises a centrifugal impeller .15 mounted directly on the turbine shaft extension 16. The impeller is surrounded by a casing 17 which defines an annular pump inlet chamber is and a discharge scroll 21. Any suitable type of pump other than a centrifugal ump may also be employed. 7

The discharge scroll 21 of the oil pump 14 communicates with a discharge pipe 22, to which is connected the servomotor supply conduit 5. A suitable pressure regulating valve 23 may be incorporated in the conduit 5 to maintain the pressure of the oil supplied to the servomotor 4 constant at a preselected value. Spent liquid from the servomotor 4 returns through conduit 24 to the inlet 18 of pump 14, as noted hereinafter. A suitable check valve 25 is provided in conduit 22 to prevent flow of liquid in a reverse direction through pump 14. I

Arranged in the oil reservoir 12. or in any other suitable location is a hydraulic turbine 26 consisting of a housing 27, an impeller 28, and an inlet scroll 31. A conduit 32 supplies oil under pressure from the discharge scroll 21 of pump 14 to the inlet scroll 31 of turbine 26. Oil discharge from the turbine 26 is led by -a conduit 33 to the inlet chamber 18 of the main oil pump 14. The impeller 28 of the hydraulic turbine 26 is directly connected by a shaft 34 to a pump impeller 35 of a hydraulic pump 36. The hydraulic pump 36 is located below the level of the oil in reservoir 12 and may be placed within the reservoir as shown. It defines an inlet opening 37 for admitting oil from the reservoir 12 to the pump impeller 35 and a pump discharge scroll 38. A conduit 41 containing a check valve 42 delivers low pressure oil from the discharge scroll 38 to the inlet of trio generator (not shown) driven by steam turbine and through a reducer 44 and conduit 45, to the lubrication system of the steam turbine and through conduit '46 to the inlet chamber of the main oil Pump 14.

'52 similar to pump 36 located below the oil level in reservoir 12. An inlet opening 53 is arranged to admit oil from reservoir 12 to the pump 52. A conduit 54 supplies oil under pressure from the pump 52 through a suitable check valve 55 to the conduit where the oil is supplied to the servomotor 4. Another conduit 56 connects the high pressure conduit 54 to a reducer 57 that reduces the pressure of incoming oil to a value suitable for lubrication by throttling the flow of oil passing through the reducer. The low pressure oil from the reducer 57 is led by a conduit 58 to the conduit 41 leading into the oil cooler 43. From the oil cooler 43, the low pressure oil is supplied through reducer 44 and conduit 45 to the lubrication system of the turbine, and through conduit 46 and orifice 47 to the main pump 14 to prime the pump 14. The orifice 47 also allows discharge oil from servomotor 4 to flow into the bearing system and to return through conduit 13 to reservoir 12 so that the servomotor can be operated when the main pump 14 is not running. The reducer 57 is equipped with a valve 61 which is designed to close when the oil pressure generated by the hydraulic pump 36 after the turbine 1 has been started exceeds the predetermined value of the biasing spring 62 of the reducer 57.

To start the system, the motor 51 is energized and liquid is supplied by the starting pump 52 through conduit 54 to conduit 5 to the servomotor 4. Check valve 25 in conduit 22 prevents this priming liquid from flowing backwards through the main pump 14.

When the pressure in the oil system rises to the proper value for actuating the servomotor 4, turbine 1 may be started and brought up to speed, during which the discharge pressure of the main oil pump 14 will increase to its normal operating value so that check valve 25 is caused to open. When the pressure in

conduits

22, 32, produced by the rotation of the main oil pump impeller 15, rises above the pressure produced in conduit 54 by the starting pump 52, the check valve 55 will act to prevent any leakage of oil from conduit 22 backwards through conduit 54.

Suitable control means indicated generally at 71 may be provided for the starting motor 51, and so arranged that the motor is automatically deenergized when the pressure in conduit'32 rises to a value in excess of the preselected value determined by a spring 72 in the control system 71. The control system 71 comprises a toggle switch 73 which is well known in the art coupled to a piston 75, so that the switch 73 breaks the circuit to motor 51 when liquid pressure in conduit 32 exceeds the preselected value determined by the spring 72 forcing the piston 75 inward. The spring 72 biases the piston 75 so that the switch 73 is in a closed position so that motor 51 will be energized whenever the pressure in conduit 32 falls below the preselected value of spring 72.

From the above description of the apparatus, it will be apparent that the hydraulic system for the steam t-urbine 1 in effect comprises a high pressure circuit and a low pressure circuit interconnected by the conduit 46. The high pressure circuit comprises the main oil pump 14 in series with the parallel connected servomoter 4 of the steam turbine 1, and the hydraulic turbine 26. The low pressure circuit comprises the hydraulic pump 36, the

a pressure suitable for operation of the servomotor 4. This pressure may be of the order of 200 pounds per square inch, which is considerably higher than is ordinarily used for lubrication purposes. Therefore it becomes necessary to reduce the pressure in some manner to a value suitable for the turbine lubrication system, which may be of the order of only 15 pounds per square inch. The prior art has accomplished this by means of a throttling valve, but the resulting throttling process wastefully dissipates an appreciable amount of the power abstracted from the turbine shaft 2 for driving the oil supply system.

An important feature of the invention is that the reduction of the oil pressure from the value required for operation of the servomotor 4 to that required for the turbine lubrication system is accomplished in a manner which makes use of the energy represented by this pressure drop. This is effected by causing the pressure drop to occur across the hydraulic turbine 26 which serves to drive the hydaulic pump 36. This method of conserving the energy in the oil is found to make an important contribution to the overall efiiciency of the prime mover by reducing the power needed to drive the oil supply pump 14.

This improved liquid supply system provides oil at a comparatively high pressure for operating hydraulic devices such as a servomotor 4, and also supplies oil at a much lower pressure for lubrication. This is accomplished by the high speed main oil pump 14 coupled directly to the shaft 2 of the prime mover 1 without intermediate gearing and having the hydraulic turbine 26 arranged to positively prime the main pump 14 when the steam turbine 1 is at its operating speed. The hydraulic turbine 26 is driven by energy derived from the drop in pressure from the high value required for the servomotor 4 to the lower value required for lubrication. With this improved arrangement, a minimum quantity of oil need be handled by the main oil pump 14, so that the power required for operating the system is kept to a minimum. By using the pressure drop inherent in the system to furnish energy for driving the hydraulic pump 36, a further important improvement in the power consumption of the system is obtained. With this invention, a very much smaller quantity of oil need be pumped, than in other previously suggested systems. By thus reducing the volume flow in the system, the piping to and from the main oil pump may be smaller than in other systems. The main pump 14, the hydraulic turbine 26 and the pump 36 are designed for maximum efiiciency with the main pump 14 delivering just enough pressure to operate the turbine 26, pump 36 and to provide the required quantity of oil to the bearings and back to the main pump 14. There is no wastage of the energy available from the aforementioned pressure drop since all of the oil from the main pump 14 passes through the hydraulic turbine 26.

In the alternative embodiment shown in Fig. 2, a system is shown for supplying two different liquids to a steam turbine at two different pressures. The reservoir 12 is divided by means of a plate 10 into two hydraulically independent reservoirs or compartments, one for the high pressure system utilizing a noninflammable liquid oil cooler 43 and the lubrication system of the steam V turbine connected in series.

. During normal operation of the steam turbine 1, oil is delivered by the main pump 14 to the conduit 22 at and the other for the low pressure system utilizing oil.

Elements of the apparatus shown in Fig. 2 which are similar to the apparatus described in Fig. 1 are designated by the same numerals used in Fig. 1. The high pressure circuit of Fig. 2 is similar to the high pressure circuit of Fig. 1 comprising the main pump 14, hydraulic turbine 26 and an auxiliary starting motor 51 and pump 48, none of which are shown in section. The low pressure circuit is similar to that of Fig. 1 comprising a hydraulic pump 36, not shown in section, and oil cooler 43. The shaft 34 drivingly connecting the impeller of hydraulic turbine 26 to the impeller of hydraulic pump 36 passes through an opening in the plate 10. A suitable sealing means surrounds the shaft 34 and the opening in the plate 10 to hydraulically isolate the compartments from one another.

Instead of using a reducer 57 to provide low pressure oil to the steam turbine 1 during starting of the turbine 1, an auxiliary starting pump 65 driven by a motor 64, is used to perform the same function. The starting

pump motors

51, 64 may be of any suitable type such as an electric motor or 'a small steam turbine. The

motors

51, 64 have control means 71 similar to that of Fig. 1.

The difference between the hydraulic systems shown in Fig. 1 and Fig. 2 is that in Fig. 2 the high pressure cir-v cuit may utilize water or any other noninflammable liquid since it is completely separate from the low pressure circuit utilizing lubricating oil whereas in Fig. 1, a common liquid is used in both the high pressure circuit and the low pressure circuit. In Fig. 1,

conduits

45, 46 connect the low pressure outlet of the reducer 44 with the inlet conduit 24 leading into the inlet of the main pump 14 of the high pressure system to prime the main pump 14 when the steam turbine is started. In Fig. 2, an auxiliary pump 77 directly connected to the shaft 34 of the hydraulic turbine 36 may be used to insure adequately priming the main pump 14. It also serves as a discharge for liquid from the main servomotor 4 when the main pump 14 is not running.

Although but two embodiments have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a hydraulic system for supplying a liquid at a high pressure and a liquid at a lower pressure to a machine, the combination of: a first pump driven by said machine, said first pump discharging liquid at a high pressure; a hydraulic turbine; a first conduit connecting said first pump with said hydraulic turbine so high pressure liquid discharged from said first pump drives said hydraulic turbine; a second conduit connecting said hydraulic turbine and said first pump so liquid discharged from said hydraulic turbine returns to said first pump; a third conduit connecting said first pump with said machine to supply said high pressure liquid to said machine; a fourth conduit connecting said machine and said first pump so liquid supplied by said third conduit that is discharged from said machine returns to said first pump; said first, second, third and fourth conduits forming a first hydraulic circuit including said first pump and said hydraulic turbine; a liquid reservoir, a second pump located in said reservoir and driven by said hydraulic turbine, said second pump taking liquid from said reservoir and discharging said liquid at a pressure lower than said high pressure; a fifth conduit connecting said second pump with said machine to supply liquid at said lower pressure to said machine, a sixth conduit connected between said machine and said reservoir so liquid supplied by said fifth conduit that is discharged from said machine returns to said reservoir; said fifth and sixth conduits forming a second hydraulic circuit including said reservoir and said second pump; an auxiliary means operable when starting said machine for providing said high and said lower pressure liquid including a third pump and a pressure reducing valve, said auxiliary means arranged to automatically deenergize when said first pump delivers liquid at said high pressure, and a seventh conduit having an orifice, said seventh conduit connecting the suction of said first pump to said second circuit to maintain the primed condition of said first hydraulic circuit.

2. In a hydraulic system for supplying a liquid at a high pressure and a liquid at a lower pressure to a machine, the combination of: a first pump driven by said machine, said first pump discharging liquid at a high pressure; a hydraulic turbine; a first conduit connecting .said first pump with said hydraulic turbine so high pressure liquid discharged from said first pump drives said hydraulic turbine; a second conduit connecting said hydraulic turbine and said first pump so liquid discharged from said hydraulic turbine returns to said first pump; a third conduit connecting said first pump with said machine to supply said high pressure liquid to said machine; a fourth conduit connecting said machine and said first pump so liquid supplied by said third conduit that is discharged from said machine returns to said first pump; saidfirst, second, third and fourth conduits forming a first hydraulic circuit including said first pump and said hydraulic turbine; a liquid reservoir, a second pump located in said reservoir and driven by said hydraulic turbine, said second pump taking liquid from said reservoir and discharging said liquid at a pressure lower than said high pressure; a fifth conduit connecting said second pump with said machine to supply liquid at said lower pressure to said machine; a sixth conduit connected between said machine and said reservoir so liquid supplied by said fifth conduit that is discharged from said machine returns to said reservoir; said fifth and sixth conduits forming a second hydraulic circuit including said reservoir and said second pump; a third pump operable when starting said machine for providing said high and said lower pressure, a seventh conduit having an orifice, said seventh conduit connecting the suction of said first pump to said second circuit to maintain the primed condition of said first hydraulic circuit, and for initially priming said first hydraulic circuit; an eighth conduit arranged to convey liquid discharged by said third pump to said first conduit to supply liquid at high pressure to said machine, said first conduit having a check valve to prevent reverse flow of liquid through said first pump; a ninth conduit having pressure reducing means and arranged to convey liquid from said third pump to said fifth conduit to supply liquid at lower pressure to said machine, said fifth conduit having a check valve to prevent reverse flow of liquid through said second pump.

References Cited in the file of this patent UNITED STATES PATENTS 1,617,460 Schmidt Feb. 15, 1927 2,126,533 Coughey Aug. 9, 1938 2,277,569 Vickers Mar. 24, 1942 2,440,980 Sheppard May 4, 1948