US2866620A - Means for counterbalancing starting thrust in turbine driven pump units - Google Patents

Description

Dec. 30, 1958 J. G. WILLIAMS 2,866,620 MEANS FOR COUNTERBALANCING STARTING THRUST IN TURBINE DRIVEN PUMP UNITS Filed Oct. 3, 1957 JOHN G. WILLIAMS INVENTOR.

MEANS FOR COUNTERBALANCING STARTING THRUST IN TUINE DRIVEN PUMP UNITS John G. Williams, Springfield, N. J., assignor to Worthington Corporation, Harrison, N. J., a corporation of Delaware Application October 3, 1957, Serial No. 688,041

1 Claim. (Cl. 25365) This invention generally relates to improvements for turbine-driven pump units, and more particularly relates to means for counterbalancing the starting thrust load of these units caused by static fluid pressure in the pump, to thereby eliminate considering this factor in the selection of a thrust bearing appropriate for the unit.

It is the common practice today to use a large and expensive bearing whenever a large thrust load must be overcome in starting the pumping unit. This practice, however, creates waste because in subsequent operations, a hydrodynamic oil film will be developed by rotation under the bearing pads or bearing surfaces, and the load-carrying capacity of the bearing increased to a greater extent than is needed, whereby the bearing is more expensive than one that could efiectively handle the normal thrust load requirements of the unit.

Accordingly, to eliminate this waste, it is an object of the present invention to provide the pumping unit with suitable means to counterbalance the starting thrust load, thereby permitting the thrust bearing to be selected independently of this factor, and thus in accordance with its expected normal operational thrust load requirements.

It is a further object to provide the means for counterbalancing the starting thrust load by adapting the usual elements of the turbine to this purpose, whereby no additional expense is incurred.

More specifically, as is usual in steam turbines, running clearance is provided between the sides of the turbine wheel and the walls of the steam chamber, and at the periphery of the running clearance on one side of the turbine wheel, the flow directing nozzles mounted about the steam chamber wall are positioned within close proximity of the steam buckets carried about the periphery of the turbine wheel. The close proximity between the buckets and nozzles is required for eflicient operation of the turbine and has been found to constitute a natural restriction to any radially outwardly flowing steam from the running clearance space between the turbine wheel and steam chamber wall. Thus, this said running clearance space effectively serves as a steam chamber, and to accomplish the objects of the present invention, high pressure steam is admitted through a suitable inlet to this chamber prior to starting of the pumping unit, and this steam exerts a force against the turbine wheel to effectively counterbalance the starting thrust load of the pumping unit.

The novel adaptation of the turbine elements to counterbalance starting thrust load of the pumping unit as described above will be better understood when considered in connection with the accompanying specification and the drawing forming a part thereof.

In the drawing, a partly broken away longitudinal section of a steam turbine driven pump unit is shown which embodies the present invention.

More particularly, in the drawing, the pump designated 1, and the steam turbine designated 2, are shown suitably mounted on a common rotatable shaft 3 so that the turbine wheel when driven by steam will in turn drive the pump impeller 5. The fluid to be pumped enters the pump 1 through its inlet 6, and prior to starting of the pumping unit, this fluid contained in the inlet 6 will cause a thrust load on the shaft Sin the direction of the arrow A. More specifically, this thrust load at starting is due to the static pressure of the fluid, which pressure may be about 2000 p. s. i. (pounds per square inch) and cause a thrust load of between 20,000 to 30,000 pounds on the shaft 3.

Situated to the right of the turbine 2, and suitably mounted about the shaft 3 to provide support to the shaft 3 against thrust, is a suitable type thrust bearing, generally designated 7 and shown only diagrammatically in the drawing. This bearing 7 is of the well known Kingsbury type and thus its construction and operation does not need to be more fully described herein, and is selected solely in accordance with its thrust load carrying capacity during operation of the pumping unit. In other words, the selection of the bearing is made independent of the consideration that it must overcome the large starting thrust load as hereinbefore mentioned, and therefore the bearing 7 is not larger in size or more expensive than is needed for normal operational thrust load requirements of the pumping unit.

To accomplish this economy in the selection of the bearing 7, suitable means, to be fully described, are provided in the pumping unit to counterbalance and thus efiectively eliminate the starting thrust load that would ordinarily be imposed on the said bearing prior to starting of the pumping unit.

These means generally consist of the usual elements of the turbine 2, arranged in their usual functional positions within the said turbine, and specifically adapted to the purpose of counterbalancing axial thrust in accordance with the teachings of the present invention. Thus, it will be noted that the turbine wheel 4 is disposed to rotate within the steam chamber 8 formed by the bell-shaped turbine casing 9 and the end plate 10 mounted to this said casing by the bolt means 11, and so of necessity the turbine wheel 4 has running clearance on either side, between it and the steam chamber walls.

Suitably mounted about the periphery of the turbine wheel 4 are two rows of steam buckets 12, between which is an intervening row of redirecting blades 13 carried on a ring element l lmounted to the end plate 10 by the bolt means 15. Axially adjacent the right row of steam buckets 12 are the flow directing nozzles 16 which are circumferentially spaced within a ring element 17 connected to the end plate 10 by the bolt means 18. Thus, steam enters the turbine 2 through an inlet conduit 19, fills an annular chamber 20, and then is directed through the nozzles 16 along a 360 degree arc of steam admission to the steam buckets 12, the steam then expands in the said buckets to drive the turbine wheel 4, and finally is exhausted through the turbine steam outlet conduit 21. It will be appreciated that in order to obtain maximum efficiency from the steam turbine 2, the flow directing nozzles 16 must be in close proximity to the right row i of steam buckets 12 along the 360 degree are of steam admission. For this reason, the clearance space between this row of buckets 12 and the nozzles 16 usually does not exceed .030 inch.

It has been found that this small clearance space between the right row of buckets 12 and the nozzles 16 constitutes a natural restriction to any steam that attempts to fiow radially outwardly from the running clearance space on the right side of the turbine wheel 4. Thus, this clearance space is in effect a usable steam chamber, being herein designated 22, and defined on one side by the right side 23 of the turbine wheel 4, on the other side by the Wall section 24 of the end plate 10, and on the end generally by the right row of buckets 12 and the nozzles 16, or more particularly by the circular rim 25 formed in the end .of .the turbine wheel 4 carrying the right row of buckets 12 and the ring element 17 containing the nozzles 16.

As clearly shown in the drawings, a suitable inlet 26 is provided to the steam "chamber ,22, which inlet in practice is connected to atsuitable source of .high pres sure steam ,(notrshown). Thus, prior to starting of the pumping innit, high pressure steam is admitted through therinlet '26 to the steam chamber 122, and in thischamber the said steamcxerts aforce against ,theturbine wheel 4 in the directionof the arrow B. 'l'hisforce exerted by the said steam against the turbine wheel 4 thus counterbalances the starting axial thrust load caused by thestatic pressure of the fluid within the pump .inlet 6 and :thus accomplishes the objects of the gpresent invention.

It will be ,underst00d1that the invention is :not to be limited to the specific construction or arrangement ,of partsshown, butthat they maybe widely modified within the invention, as rdefined byythel claim.

"Whatjs claimed is: I

:In a steam turbine including, a casing rhaving L3- steam chamber formed therein, :a turbine wheel disposed for rotation 'within said steam :chamber, a row :of steam bucketscarried about the periphery of said turbine wheel,

and circumferentially spaced flow directing nozzles in proximate spaced relation to the steam buckets mounted about the interior of the wall of said steam chamber, the combination with said turbine of means for counterbalancing an axial force exerted against the side of the turbine wheel remote from the flow directing nozzles, said means comprising an annular chamber formed in the steam chamber on the side of the turbine wheel nearest the flow directing nozzles, said annular chamber defined on oneside bythe side of the turbine wheel, on the other side .by the ,wall of the steam chamber, and on the end by the buckets and .fiow directing nozzles in proximate spaced relation to each other, and an inlet to said annular chamber communicating with a suitable source of pressurized steam, whereby steam admitted to said annular chamber will exertra ,counterbalancing force against the said turbine wheel.

References Cited in the file of this patent UNITED STATES PATENTS 892,559 'Pfau Sept. 29, 1908 1,030,153 :Barbezat June 18, 1912 1,610,454 Lawaczeck Aug. 29, 1921 2,746,671 Newcomb May 22, 1956

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