US3459133A - Controllable flow pump - Google Patents

Description

Aug. 5, 1969 P. H. scHl-:FFLER CONTROLLABLE FLOW PUMP 2 Sheets-Sheet 1 l Filed Jan. 23, 1967 mvENToR Paul H. Scheffler BY 7 zg M v `n.\\\

FIG. l

W ITNESSES ATTORNEY Aug. 5, 1 969 P. H. scHr-:FFLER N CONTROLLABLE FLOW PUMP 2 Sheets-Sheet 2 Filed Jan. 23, 1967 United States Patent Ofce 3,459,133 Patented Aug. 5, 1969 3,459,133 CONTROLLABLE FLOW PUMP Paul H. Scheffler, Lima, Ohio, assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporationof Pennsylvania Filed Jan. 23, 1967, Ser. No.610,935 Int. Cl. F04d 3/00 U.S. Cl. 103-88 8 Claims ABSTRACT oF THE DlscLosURE the effective head by producing a forced vortex of liquid mathematically described by the classical formula expressing the parabolic surface of revolution for solid body rotation about a vertical axis. The first stage rotor extends into the second or discharge stage (as an impeller) which includes a volute collector housing having an outlet port connected to an entrance portion of the diffuser. In the second stage, the impeller is essentially a flanged portion of the rotor having a surface for radially and tangentially directing the liquid received from the first stage against the volute collector. The volute collector redirects the tangential flow of liquid to a linear flow for introduction and into the second stage where the molten metal is rotor in accordance with the classical expression describing the parabolic surface of revolution for solid body rotation about a vertical axis.

The present invention relates generally to a pump for pumping liquids, and particularly to ceramic pumps or pumps with ceramic sub structures for pumping liquid molten metal in an economical manner yet affording precise control of the liquid Iflow rate.

In processes involving high temperature and/or corrosive fluids, it is frequently desirable to circulate the fluids through a process vessel in order to obtain more uniform temperature distribution, for example, or to effect more uniform mixing of additives, and generally to effect a more proficient processing operation. It is further often desirable to pump the fluids to another process site or location in order to reduce the manual labor required, and to speed the transfer operation. Such processes include the melting of aluminum bars or copper stock for preparation of aluminum alloys and copper products. Because of the high temperature and corrosive characteristics of such fluids, it is imperative that no leakage 0ccur in the circulating and transferring apparatus. In addition, these characteristics usually require that ceramics or other chemically inert materials be used to contain -the fluids. This in turn requires that the -flow path be relatively simple to avoid costly tooling and/ or Ifinal grinding of the very hard ceramic. A further concern with transferring the molten metal from say a furnace to molds or cooling containers is the control of the rate of fluid flow; it is desirable to precisely control the transfer flow rate.

In accordance with the broad principles of the invention, a pump especially adapted for handling high temperature, corrosive metal liquids, comprises a ceramic rotor having two principal stages or sections and a diffuser, made of a ceramic material, connected in dluid communicationwith the second stage of the rotor. The Ifirst stage or flow control section includes an inlet opening located in a bottom portion of a housing with the ceramic rotor extending into the first stage housing and disposed over the housing opening for drawing liquid to be pumped into the rotor. The rate of flow of the liquid is controlled by the effective head of liquid producing inlet flow to the flow control section in which the rotor is rotated to modify into the diffuser which provides the proper discharge pressure. The second stage impeller and the volute collector are dimensioned to provide a droplet flow of liquid into the diffuser to prevent an increase in pressure in the area of the drive shaft thereby eliminating the need for a shaft seal to prevent pump leakage.

Accordingly, an object of the invention is to provide an economical and versatile pump capable of handling a variety of types of liquids in a leakage free manner Without the need of lfinished component surfaces, close tolerances and costly seals between fixed and moving parts.

A more particular object of the invention is to provide an economical pump made of ceramic components including a ceramic housing, diffuser, drive shaft, rotor and irnpeller designed and dimensioned to transfer or circulate molten metal in a leakage free manner without the use of a seal or seals disposed between the drive shaft and the pump housing.

v Another object of the invention is to provide an economical pump capable of transferring or circulating high temperature, corrosive liquids in a controlled manner dependent upon the speed of a rotating impeller and the relationship of the impeller speed of rotation to the depth of the liquid being pumped.

These and other objects and advantages of the invention will become more apparent from the following detailed description taken in connection with the accompanying drawings in which:

FIGURE 1 is a cross sectional view of a pump constructed in accordance with the principles of the present invention;

FIG. 2 is another cross sectional view of the pump taken along line II-II in FIG. 1 which shows the impeller thereof in top plan view and the wall structure of a diffuser in cross section, and

FIG. 3 is a perspective view of a rotor employed in the pump of FIGS. 1 and 2.

Specifically, there is shown in FIGURE 1, a pump 10 having a lower housing portion 12, an upper housing portion 13, a first stage rotor 16 coaxially disposed within the housing portions, and an elongated drive shaft structure 18 coaxially disposed within the first stage rotor 16 and extending vertically through a central opening 13 provided in the upper housing portion. The housing portions, rotor and drive shaft are made from a hard ceramic material, such as silicon carbide or other suitable materials that are heat and corrosion resistant.

The housing portions 12 and 13 are provided with flanged mating extension 14 and 15 respectively for joining and sealing the portion together to form an overall housing unit. The flange structure of FIG. 1 is shown only for purposes of illustration and other suitable congurations may be employed in place thereof or in conjunction therewith. A gasket 17 may be disposed between shown) may be disposed over the flanges and bolted or otherwise secured together. In this manner the mechanical pressure and stress needed to secure the housing portions together are exerted on and evenly dis-- tributed about the iianges.

The lower housing portion 12 forms generally a first or fiow control stage or section 20, and the upper housing portion 13 forms generally a second or discharge stage 21 in the form of a volute collector. The bottom wall portion of the lower housing is provided with an inlet port 23 for admitting the liquid to be pumped into the first stage rotor 16. The upper housing portion or volute collecter is provided with an outlet port 2S which places the volute collector in fiuid communication with the entrance portion 26 of a ceramic diffusing structure 27. The volute collector 13 may be further provided with a standpipe portion 28 for preventing possible splashing of the liquid through the volute collector opening 13' during transient conditions. No seal however is needed in the opening 13 for reasons to be explained hereinafter.

The elongated drive shaft 18 is preferably a hollow tube structure having a cylindrically shaped wall 30 extending axially between the inlet port 23 and the uppermost portion of the pump housing. The drive shaft may, however, be a solid structure, and it may be suitably attached to other portions of the rotor than those described above, or the first stage rotor may be designed and driven so as to eliminate the need of the elongated drive shaft. In the present showing (FIG. 1), the lower hollow portion of the shaft wall 30 is provided with openings 31 which place the inner portions of the first stage rotor 16 in fluid communication with the inlet port 23. Immediately above the openings 31 in the shaft 18 is disposed a plug means 32 and a projection 33 for respectively preventing the flow of liquid up the interior of the shaft and directing the liquid through the openings 31. The elongated portion of the drive shaft disposed within the first stage rotor 16 is further provided with a reduced outside diameter so that an inner, narrow space 34 is provided between the shaft and the first stage rotor wall presently to be described. The lowermost portion of the drive shaft is provided with a rotor engaging end portion 35 attached to the rotor.

The first stage rotor 1-6, as shown in FIG. 2, is provided with four inwardly extending ribs or projections 36 (shown in elevation in the figures which extend the length of the first stage rotor and define the inner space 34 with the drive shaft as seen in FIG. 1. The ribs 36 further form longitudinally extending open areas 37 forming inner passageways adjacent the drive shaft 18 as best seen in FIGS. 2 and 3.

The upper portion of the ribs 36 contact the periphery of the drive shaft 18 at locations 38 so that the shaft and rotor may be suitably cemented or otherwise attached together at said locations. A bore 39A (FIG. 3) is provided in a bottom wall portion 39 of the first stage rotor for receiving the end 3S of the drive shaft as shown in FIG. 2. The first stage rotor and drive shaft are thoroughly secured together, for example, by cementing the end 35 to the end wall 39 with a suitable cement.

The upper portion of the first stage rotor 16 is provided with an outwardly projecting impeller portion 40 housed within the second stage 21 by the volute collector 13. The upper surfaces of the impeller 40 is provided with a plurality of raised vanes 41 extending in radial directions from the center of the impeller, as best seen in FIG. 2, for directing the liquid to be pumped against the voluted surface of the volute collector with rotation of the impeller.

The pump may be placed in a pool (not shown) of molten metal for operation as an immersible unit or it can be operated outside a process vessel or a furnace (not shown) containing the liquid or molten metal.

In the latter case, a conduit would be connected between the inlet port 23 of the pump and an outlet port provided in the vessel containing the liquid.

In operation, the liquid to be pumped by the pump 10 enters the port 23 and travels through the opening 39A (FIG 3) provided in the rotor and through the openings 31 provided in the shaft 18. With rotation of the rotor 16, the liquid is conducted and forced up through the open areas or inner passageways 37 between the ribs 36 to the impeller 40 in the second stage 21 as indicated by appropriate arrows. The rate of liquid flow into the first of flow control section 20 of the pump 10 is first governed by the head or height of the liquid in the process vessel above the level of the pump inlet port 23. If the axial length of the first section 20 is made equal to the depth of the liquid in the process vessel, and a column of liquid is contained within the first section equal to the liquid depth in the process vessel, the inlet fiow through the port 23 is of course zero. With an empty pump, i.e., no liquid column in the pump above the port 23, the inlet flow rate is maximum, or at least the maximum permitted by the inlet 23 diameter, piping length (if any), surface roughness and similar factors. Any flow rate between maximum and zero can therefore be provided by adjusting the depth or head of liquid above the inlet port as indicated by the formula:

Flow=K(D1-D2)/ where: K is the fiow coefficient for the particular inlet conduit configuration, inlet 23 diameter, fiuid properties, etc. D1 is the liquid depth in say the process vessel, and D2 is the liquid depth in the first stage 20 above the inlet port 23 From the equation, it is seen that if only a small range of fiow control is required for a particular application, a range of nine tenths (0.9) between maximum and minimum flow, for example, the D2 depth, and consequently the axial length of the first stage 20, need only be 0.81 of the D1 depth. If, however, very precise control is required over a large range with very low ow rates involved, or if it is desired to completely empty the process vessel, it is advisable to make the length of stage 20 larger than the head or depth of the liquid in the process vessel.

The effective head for producing the inlet flow (D1-D2) can be varied by rotating the rotor 16 in the first stage 20 to effect a. forced vortex in the liquid such that:

where R1, is the inside radius of the first stage rotor 16 at its discharge end in the first stage 20 as shown in FIG. 1:

w is the angular velocity of the impeller in the first stage in radians per second, and g is the gravitational constant, 32.2 feet per second This equation is a direct derivation of the classical expression describing the parabolic surface of revolution for solid body rotation about a vertical axis, usually known as:

Since the impeller portion in the second stage or discharge section 21 is merely an extension yof the rotor portion in the first stage 20, both portions will rotate at the same speed when driven by the shaft 18. The discharge (angular) velocity. required to provide the discharge pressure must thus be attained by adjusting the radius or diameter of the impeller in the second stage. For very low discharge pressures, the second stage mpeller can approach the diameter (2K1) of the rotor in the first stage. For higher discharge pressures, the second stage irnpeller diameter must be larger than the firststage, since yay-:R201 where:

VD is the discharge velocity in feet per second,

R2 is the second stage impeller radius in feet as shown in IFIG. l, and

w is the irnpeller angular velocity in radians per second The discharge Velocity and liquid flow on the impeller 40, are tangential in direction in the second stage 21. The voluted inside surface of the collector 13 (see FIG. 2) collects the tangential liquid flow and redirects it into a linear flow for discharge through the outlet port 25 to and through the entrance portion26 ofthe diffuser 27 and into the main diffusing section of the diffuser where the liquid pressure is reduced to a required value. From the diffuser, the liquid can be returned to the process vessel or directed to another vessel by use of a simple plug valve (not shown) connected in fluid communication with suitable conduit means and providing a simple flow path for the liquid.

In the diffuser 27, the liquid iiow undergoes an exchange of energy that can be expressed by the following formulas V 2 (2 ZVD2)17=2gE 'i-PE PE (Vea. V32) where:

The discharge velocity of the second stage 21 to provide the required exit pressure and velocity can thus be deter- -minded by these last two equations, and the diameter of the impeller portion within the second stage required to provide this discharge velocity can be determined by the equation given immediately before these last two.

The volute collector 13 and the entrance portion 26 of the diffuser 27 are dimensioned to provide a droplet or slug flow of liquid from the second stage rather than a full or sheet flow in order to prevent the generation of pressure in the area of the volute collector opening 13.

This eliminates the necessity of closing the space between in which the flow will be zero. Any foreign material with a density greater than that of the liquid being pumped will be centrifuged into this annular space and held there until removed by mechanical scraping. Thus an effective centrifugal filter can easily be incorporated into the first stage rotor.

In FIG. l, a ceramic cover 50 is provided for mounting and securing suitable rotor driving means to the pump housing. The cover S0 may be secured to the volute housing 13 in the manner described above in connection with the housing flanges 15 and 16.

It should now be apparent from the foregoing description that a novel pump has been disclosed which is particularly suitable for pumping high temperature and corrosive molten metals in an economical manner. This is accomplished by use of a ceramic housing and impeller having generally unfinished surfaces and substantially no close tolerances. The pump is further leak-proof Without the use of seals disposed between a rotating drive shaft and a fixed housing. The flow rate of the liquid through the novel pump is effectively controlled by the effective head of liquid producing inlet flow to a first flow control section in which the rotor can be rotated to modify the effective head by producing a forced vortex of liquid mathematically described by the classical formula expressing the parabolic surfaces of revolution for solid body rotation. A volute collector forms the housing of a second, discharge stage in which a portion of the impeller is designed and dimensioned to produce a desired discharge pressure to a diffuser input, the diffuser providing the ydesired discharge pressure to a receiving vessel or conduit.

While the invention has been described in connection with a preferred embodiment, it will be understood that it is not intended to be limited to the particular embodiment illustrated but is intended to cover all alternative and equivalent constructions falling within the spirit and scope of the appended claims.

What is claimed is:

1. A pump for pumping and transferring liquids, said pump comprising:

a housing including an elongated flow control section and a relatively short discharge section, said flow control section having an inlet opening for admitting liquid into the pump, rotor means having an elongated portion disposed within the ow control section and an irnpeller portion disposed within the discharge section, the elongated portion having axially extending passageways for conducting a flow of liquid therethrough and means defining a restricted inlet opening for admitting liquid into said rotor and passageways,

said rotor means further having a discharge radius and length dimension in the flow control section adapted to produce a forced vortex of liquid when rotated which varies an effective head of liquid producing a flow of liquid into the flow control section, and

a drive shaft extending into said rotor along the axis thereof,

said shaft being secured in the lower end of said rotor for rotating same.

2. The pump recited in claim 1 in which the vortex of liquid produced by the rotor means when rotated is expressed by the formula Where D1 is the depth or head of liquid in a vessel containing the liquid to be pumped,

D2 is the depth of liquid in the ow control section above an inlet port provided therein and in uid communication with the vessel,

R1 is the inside discharge radius of the impeller in feet,

w is the impeller angular velocity in the first stage in radians per second, and

g is the gravitational constant 32.2 feet per second per second.

3. The pump recited in claim 1 in which an inlet port is provided in a bottom wall portion of the flow control section.

4. The pump recited in claim 1 in which the discharge section includes a volute collector provided with an outlet port.

5. The pump recited in claim 1 in which the discharge section includes a volute collector having an outlet port, a diffuser having an entrance portion connected in uid communication with the outlet port,

the volute collector and diffuser entrance portion being dimensioned to provide a droplet flow type of liquid discharge from the discharge section when the impeller means is rotated therein.

6. The pump recited in claim 1 in which the impeller portion within the discharge section of the pump is adapted to produce a desired discharge velocity and pressure therein in accordance with the formula VD=R2L0 where:

VD is the discharge velocity of the impeller portion in feet per second,

`R2 is 4the radius of the impeller portion in feet, and

w is the angular velocity of the impeller in radius per second.

7. The pump recited in claim y1 in which the impeller portion disposed within the discharge section has an upper surface provided with radially extending vane portions.

8. A pump for pumping and transferring liquids, said pump comprising:

a housing structure,

an inlet port provided in the bottom of said housing and an outlet port provided adjacent the top of said housing a rotor disposed in said housing, said rotor having an elongated portion vertically disposed above said inlet port,

axially extending vanes provided in said rotor, said vanes forming elongated, axially extending passageways for conducting a flow of liquid therethrough,

an impeller portion provided at the top of said rotor adjacent said outlet port and in fluid communication with said passageways, and

a drive shaft extending into said housing and along the axial center of said rotor, said shaft being secured to said rotor for rotating same,

said rotor being capable of producing a forced vortex of liquid within said rotor when said rotor is rotated, said vortex being capable of producing a ow of liquid into said housing through said inlet port,

the drive shaft having at least a hollow, tubular end portion extending into said rotor inlet port and secured therein, and

openings provided in the walls of said tubular end portion for admitting the liquid into the rotor from the inlet ports.

References Cited UNITED STATES PATENTS 895,604 8/1908 UdstOOl 103-88 2,060,899 11/1936 IRussell 103-114 2,347,386 4/1944 Adams 103-114 2,984,189 5/1961 Jekat 103-88 3,162,135 12/1'964 Nichols et al 103-114 3,255,702 6/ 1966 Gehrm.

FOREIGN PATENTS 303,192 11/1932 Italy. 686,102 1/ 1953 Great Britain.

HENRY F. RADUAZO, Primary Examiner U.S. C1. X.R.

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