US2388975A - Multistage high pressure elastic fluid turbine - Google Patents

Description

Nov. 13, 1945. JEFFERSON 2,388,975

MULTISTAGE HIGH PRESSURE ELASTIC FLUID TURBINE Filed Ndv. 10, 1943 Ihvehtor: James F JeFFer'son,

gun... I 5

MW Attqrney.

Patented Nov. 13, 1945 James F. Jefferson, Lynn, Mass, assignor to General Electric Company, a corporation of New 1 York ApplicationNovember 10, 1943, Serial No. stasis ll'Ulaims. (c1. 253-76) The present invention relates to multi-stage high pressure elastic fluid turbines of the type disclosed in the copending application of Francis H. Van Nest, Serial No. 509,692, filed on the same date and assigned to the same assignee as the present application. High pressure turbines arranged to receive elastic fluid directly from a boiler or elastic fluid generator are often subject to liquid slugs such as water slugs when operated with steam. These liquid slugs may be du to the peculiar design and operation of the elastic fluid generator or boiler means for supplying elastic fluid to the turbine and due to the fact that many installations, such as marine installations, do not permit of the provision of special liquid vapor separators connected between the boiler and the turbine. Liquid slugs when permitted to pass through all turbine stages create a considerable momentary thrust load, requiring the provision of special thrust bearings. In ad-- dition, the liquid produces a severe counter torque on the turbine rotor which causes a sudden drop in speed and may impair the operation of the turbine. e v p v The object of my invention is to provide an improved construction and arrangement of turbines whereby water slugs are removed from the high pressure turbine stages, preferably the first turbine stage, and the danger of excessive thrust loads is materially reduced.

For a consideration of what, I believe to'be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing.

In the accompanying drawing Fig. 1 illustrates a turbine arrangement embodying my invention, and Fig. 2 is a modification according to my invention.

The turbine arrangement of Fig. 1 comprises a casing l having an inletchest II with a'control valve 12 for controlling the-flow offluid from an elastic fluid generator to the turbine; A rotor l3, disposed in the casing, includes-ashaft M with a plurality of bucket wheels I5, l6, l1, l8, I9, 2|], 2| secured to it. The turbine is of the partial admission type, elastic fluid being conducted to the first stage bucket wheel l by means of a nozzle plate 22 extending'over an-arc of-the bucket wheel 15. The remaining are of the bucket wheel I5 is covered by shields 23' on the inlet and outlet sides of the wheel to reduce windage loss during operation. The nozzleplate I 22 is supported on the casing. Elastic fiuidis-- directed to the succeeding bucket 'wheels by means of diaphragms 24 supported on'the turbine casing. The opening '25 leads to a chamber 26 from which stream or like fluid may be extracted through an outlet 2! for external use. The diaphragms adjacent the bucket wheel have outer rings with adjacent surfaces forming a circumferentially extending groove 28 with a drain 29 in the bottom for receiving and discharging water or like liquid-formed during operation and 10 discharged from the bucket wheel 20. The rotor is supported by journal bearing means 30 and thrust bearing means 3|. Packings 32 and 33 are provided to seal the rotor shaft to the casing I0 in order to reduce leakage of fluid from the turbine along the turbine shaft.

The inlet end of the turbine casing has an opening 34 in the bottom of the first stage casing for receiving and dischargin water or like liquid conducted from the first stage of the turbine through cut away portions 34a of the shield 23. The discharge of the water or like liquid is controlled by means of a valve member 35 disposed in a cylindrical casing 36 with a drain 3! and biased towards its seat by means of a compression spring 38 engaging a piston 39 attached to the lower end of the stem of the'valve 35. The lower end of the casing forms a pressure chamber connected by a pipe 40 to the turbine casing, preferably ata point radially inward from the outlet near the turbine shaft, that is, the diametrical center of the turbine casing near the inlet end thereof. The pipe 40 includes a flow limiting meansin the form of a restriction M.

i A spring biased relief valve 42 is associated with due to the sudden reduction in steam flow into the stage,-as well as the condensing of steam in the stage produced by the cold water. At the sametime'that the static pressure drops a pronounced difference in pressure occurs between the center and the outer periphery of the casing. It has been well established that this difference in pressure is caused by the centrifugal action of liquid rotated by the turbine wheel. When such a pressure condition exists, the pressure actcry of the casing, but the static pressure in the;

stage quickly rises to a value considerably above the maximum which can occur while operating side of the pilot valve 65 i subject to the pressure in the peripheral outlet 56. This pressure is communicated to the inlet side of the pilot valve through the clearance formed between the main valve member 54 and the cylinder 6 I, a space between the cover 51 and the main valve member 64, and openings 16 in the right-hand part ofthe mainvalve member. Q j

.During normal operation when there are no water slugs in the turbine the axial pressure at .the opening 51 is substantially the same as the peripheral pressurein the opening 56 so that the .pressures on opposite sides of the piston 69 balon dry steam. The relief valve whichis set to open at a pressure slightlyabove themaximum operating steam pressure prevents .thepressure on the lower side of piston 39 from reaching the pressure occurring in the turbine stage, thus the. pressure exerted against valve 35 is sufficiently above that exerted on the lower side of piston. to effect opening of valve 35 which drain liquid from the stage of theturbine. The stem of the valve 3 5 is guided bymeans of webs 41 having openings 48. Upon the discharge of liquid through the valve 35 and the drain 3'! the valve is relieved of the peripheral pressure created by the liquid and subsequently closed by action of thespring 38. V

The arrangement of Fig. 2 comprises a turbine casing corresponding to the casing H) of Fig. l and a rotor with a pluralityof bucket wheel 5!, 52, 53, 54, corresponding to the bucket wheels l5, I6, I! of Fig. l and diaphragms associated with the bucket wheels 5|, 52, 53 54-and corresponding to the diaphragms 24 of Fig. 1. The turbine cas ing 50 has a peripheral outlet opening 56 in the bottom and an axial opening 51 radially inward from the opening 56 near the diametrical center of the casing inlet end. Shields 58 are provided o oDpO ite sides of the first stage bucket wheel 5| corresponding to the shields 23 of Fig. l to reduce windage losses. Portions of the shields 58' near the opening 56 are cut away to form openings 59 through which liquid may pass to theperiph eral outlet 56. I i Y The discharge of liquid such as water slugsthrough the peripheral outlet 56 is controlled'by means including avalve 60. The valve 60 has a casing lil flanged to the outlet 5Bof the turbine casing and forming a drain 32. The casing'60 has ance each other and the pilot valve and main valve members are held closed by action of the spring 14 and the forces due to the differential pressures on the inlet and outlet sides of the valve members. If a slug of liquid such as water is conducted to the first turbine stage at a temperature substantially below saturation temperature, the water by centrifugal action forms a ring in the turbine casing. With this condition the peripheral pressurein' the outlet 56 will be greater than the axial pressure through the outlet 51. Hence, a greater force will be created on the left-hand side of the piston 69 than on the rightpilot valve cause opening of the main valve mem- -ber 64, thus permitting the discharge of liquid sure at the axial outlet 51.

a seat 63 fora main cylindrical valve member 64' which in turn forms a seat for a pilot or auxiliary j valve member 65 attached to a stem 66. The right-hand end of the valve casing 6! is closed by a cover or bottom 61 which also forms part of a differential pressure responsive device comprising a cylindrical casing 68 flanged to the cover 61 and including a piston 59 attached to an extension of the'valve stem 66. The left-hand portion of the casing 68 is connected by a pipe 10 to the from the peripheral outlet 56 through'the drain 62 of th valve casing The discharge of liquid from the turbine casing reduces the peripheral 5 pressure and thuspermits the piston 69 to re turn to its normal position by action of the spring 14, resulting in closing movement of the valve.

in the case described in connection with Fig. 1', the operation is different when the liquid I slugs are such as to produce no differential press sure but an abnormally high static pressure in the turbine casing. I that case the peripheral pres- I sure in the first turbine stage doe not rise at a rate much greater than that of the axial pres- Inorder toeffec t valve opening under such circumstances the relief valve 13 is provided which functions similarly to the relief valve l2. I The relief valve'13is set for a certain pressure above normal operating pressure in the first turbine stage.

towards the right and opening movement of the peripheral outlet 56 and the right-hand end of I the casing 68 is connected throughia pipe H to the axial outlet 51 of the turbine casing. The pipe H has a restrictio or orifice l2-corresponding to the orifice 4| of Fig. 1. A spring loaded relief valve 13 corresponding to the relief valve 42 in Fig. 1 is connected to the pipe H at a point between the orifice 12 and the cylinder 68. The pilot valve'stem 66 is biased towards the left, that is towards valve closing position, by: mean of a spring 14. In addition, the valve is biased towards closing position by the difierential pressure exertedon the pilot valve 65. i The outlet side of the pilot valve 65 is subject to the'pre's sure in the dischargeopening 62 while the inlet normal operating pressure in the first turbine movable valve members 65, B4. u u

with my invention lihave accomplished an improved construction and arrangement-of elastic fluid turbines subject to liquid slugs in the high pressure turbine stage or stages during v operation. These liquid slugs according to my invention 'areremoved from the high pressure turbine stages. preferablythe first turbine stage, by means including a valve and amechanism for operating the'valve;whichamechanism is responsive tothe difference between .the'peripheral I and axialpressures or the radial pressure rise near the peripheral outlet of the turbine and also responsiveto a'predetermined pressure above the stage. The elements of this mechanism respon-v sive to the difference between the peripheraland axialfpressures in the firstturbine stage effect .positive opening of the valve as long as the liquid T slugs are of such a nature as to produce a difference in pressur between the center and periphery of the casing while the elements of the mechanism including, a relief valve responsive to a certainaxial pressure in the turbine, effect operation of the mechanism in case the liquid slugs are'such as to produce only an abnormally high static pressure in the turbine casing.

Having described the method of operation of my invention, together with the apparatus which I now consider-to represent the best embodiment thereof, I desire to have it understood that the apparatusshown is only illustrative and that the invention maybe carried out by other means.

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

'l; Multi-stage elastic fluid turbine having a casing with an inlet and an exhaust end for elastic fluid and being subject to liquid slugs carried alongwith the elastic fluid, the casing having a peripheral opening near the first stage for discharging liquid therefrom, and means including a spring-biased valve subject to the peripheral pressure in the turbine for automatically controlling the discharge of liquid through the opening.

2. Multi-stage high pressure elastic fluid turbine comprising a casing with an inlet and an exhaust end for elastic fluid and a peripheral outlet near theinletifor discharging liquid slugs conducted through the inlet together with elastic fluid conducted thereto, a valve controlling the flow through the peripheral outlet, means normally biasing the valve towards closing position, and means responsive to diflerential pressure between the peripheral outlet and a point near the diametrical center of the turbine for actuating the valve.

3. Multi-stage high pressure elastic fluid turbine comprising a casing having an inlet and an exhaust end for elastic fluid and a peripheral outlet near the inlet end of the turbine for discharging liquid slugs carried into the turbine together with elastic fluid conducted thereto, and means for controlling the flow of liquid through said outlet comprising a pressure diflerential responsive device including an element subject on one side to the peripheral pressure in the outlet and a conduit connecting the other side of the element to the inlet end of the turbine casing at a point near the diametrical center thereof.

4. Multi-stage high pressure elastic fluid turbine comprising a casing having an inlet and an exhaust end for elastic fluid and a peripheral outlet near the inlet end of the turbine for discharging water slugs carried into the turbine together with elastic fluid conducted thereto, and means for controlling the flow of liquid through said outlet comprising a pressure difierential responsive device including an element subject on one side to the peripheral pressure in the outlet and a conduit connecting the other side of the element to the inlet end of the turbine casing at a point near the diametrical center thereof, said conduit including a pressure reducing means and a relief valve beyond the pressure reducing means as regards the flow of fluid through the conduit.

5. Multi-stage high pressure elastic fluid turbine having a casing withan inlet and an exhaust end for elastic fluid and a peripheral outlet near the inlet end of the casing for discharging liquid slugs entering the casing together with elastic fluid conducted thereto, means for controlling the flow through said outlet comprising a valve having a casing flanged to the turbine casing and having an inlet communicatingwith the peripheral outlet and a drain, amovable valve member engaging a seat in the valve casing and facing the peripheral outlet, means biasing said valve towards closing position comprising a piston connected to the valve and forming with the casing a pressure chamber, a spring in said chamber engaging the piston, a conduit connecting the'pressure chamber to the inletend of the turbine casing at a point radially inward from theperipheral outlet.

6. Multi-stage high pressure elastic. fluid turbine having'a casing with an inlet and an exhaust end for elastic. fluid and a peripheral outlet near the inlet end of the casing for dischargingliquid slugs carried into the casing together with elastic fluid supplied thereto, means for controlling the flow through said outlet comprising avalve having a-casing flanged to the turbine casing and having an inlet communicating with the peripheral outlet and a drain, a movable valve member engaging a seat in the valve casing and facing the peripheral outlet, means biasing said valve towards closing position comprising a piston connected .to the valve and forming with thecasing a pressure chamber, a spring in said chamber engaging the piston, a conduit connecting. the pressure chamber, to the inlet end of the turbine casing at a point radially in ward from the peripheral outlet, and spring biased relief valve means connected to said conduit and set to open at a certain pressure in the turbine casing above the normal operating pressure.

'7. Multi-stage high pressure elastic fluid turbine comprising a casing having an inlet and an exhaustend for elastic fluid and a peripheral outlet in the .bottom of the turbine casing near the inlet end thereof for discharging liquid slugs conducted to the turbine together with elastic fluid supplied thereto, means for controlling the flow of liquid slugs through the peripheral outlet comprising a valve having a main valve member and a pilot valve member, means biasing the valve member towards closing position, and means connected to the pilot valve member to open the valve in response to certain pressure conditions in the turbine casing.

8. Multi-stage high pressure elastic fluid turbine comprising a casing having an inlet and an exhaust. end for elastic fluid and a peripheral outlet in the bottom of the turbine casing near the inlet end thereof for discharging liquid slugs conducted to the turbine together with elastic fluid supplied thereto, means for controlling the flow of liquid slugs through the peripheral outlet comprising a valve having a main valve member and a 'pilot valve member normally closing the outlet, means biasing the valve members towards closing position, and means for operating the valve members comprising a differential pressure responsive device connected to the pilot valve and having pressure chambers connected respectively to the peripheral outlet and to a point in the turbine casing near the diametrical center thereof.

9. Multi-stage high pressure turbine comprising a casing having an inlet and an exhaust end for elastic fluid and a peripheral outlet in the bottom near the inlet end of the casing for discharging liquid slugs conducted to the turbine together with elastic fluid supplied thereto, means'for controlling the flow of liquid through the peripheral outlet comprising a valve having a casing flangedto, the outlet, a main valve mem her and a pilot valve member in the valve casing, means normally biasing the valve members into closing position, and means for automatically opening the valve members in responseto apre determined 'difierenc'e in pressure between" the peripheral outlet and a point in the inletjendjof the casing near the-:diametrical center thereof-Z 10. Multi-stage high pressure turbinebompris: ing a casing havingan inlet and-an exhaust-end for elastic fluid and a peripheral outlet inthe bottom near the inlet end of the casing for discharging liquid slugs conducted to the turbine together, with elastic fluid supplied thereto, means for controlling theflow of fluid through thegp'eripheral outlet comprising a valve having acasing flanged to the outlet, a main valve memher and :apilot. valve member'in the valve casing, means normally ibiasingxthe valve 1 members into closing? position, :and means for automatically opening :the valve members in response to' a predetermined'radial pressure drop near the peripheralioutlet-inthe inletiendlof the turbine casing, said last named means: comprising I a casing havingfiiatgpiston connected tothe pilot valve and forming two pressure chambers on opposite sides of the piston, a pipe connecting one of the chambersto the peripheral outlet and a conduit connectingthe'other. chamber to vthe inlet end of the turbine casing at a point radially inward from the peripheral outlet. a

'11. Multi-stage high pressure turbine comprising a casing having an inlet and'an exhaust end for elastic fluid and a peripheral outlet'in the bottom near'the inletend of the casing for-discharging liquid slugs conducted to the turbine together with elastic fluid supplied thereto, means for controlling the flow of fluid through the peripheral outlet comprising a valve having a casing flanged to the outlet, a main valve memberv anda pilot valve member in the valve casing, means normally biasing the-valve members into closing position, and means for automatically opening the valve members in response to a predetermined difference in pressure betweenthe peripheral outlet and a point in the inlet endof the casing radially inward fromthe outlet, said last named means comprising a cylindrical casing having a piston connected to thepilot valve and forming two pressure chambers on opposite sides of the piston, a pipe connecting one or the chambers to the peripheral outlet and-a-conduit connecting the other chamber to the inlet end of the turbine casing at a point radially inward from the peripheral outlet, said last named conduit including a pressure reducing means and a spring biased pressure relief valve connected-to the conduit between the pressure reducing means and the respective pressure chamber. 7

JAMES F, JEFFERSON.

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