Patent Publication Number: US-9410548-B2

Title: Pumping device

Description:
FIELD OF THE INVENTION 
     The present invention relates to centrifugal pumping devices. More particularly, the present invention relates to mixed flow pumps. 
     BACKGROUND OF THE INVENTION 
     Centrifugal pumping devices are rotodynamic pumping devices which use a rotating impeller within a casing for increasing the pressure and flow rate of a fluid within a fluid conveying network. In centrifugal pumps, a fluid is fed, from an upstream piping system, into the pump casing along or near to the rotating axis of the impeller and is accelerated by the impeller, flowing radially or axially outward into a diffuser or volute chamber, which the fluid exits into a downstream piping system. Rotodynamic pumping devices are typically used for large discharge through smaller heads, and several different types of centrifugal pumps are known, which include radial flow pumps, axial flow pumps and mixed flow pumps. 
     Mixed flow pumps combine the characteristics of radial and axial flow pumps, wherein the fluid is fed, from an upstream piping system, into the pump casing in which it is radially accelerated and lifted and which it exits at an angle, typically of 0 to 90 degrees relative to the axial direction. Mixed flow pumps operate at higher pressures than axial flow pumps, yet output higher discharges than radial flow pumps. 
     Several different types of impellers are known for use with rotodynamic pumping devices. Open impellers comprise a series of vanes attached to a central hub for mounting on a shaft, without any form of sidewall or shroud. Semi-open impellers incorporate a single shroud at the back of the impeller. Closed impellers incorporate a shroud on either side of the vanes. The type of impeller varies in accordance with the intended use, the pump characteristics, or a combination of both, and may influence the casing design. For instance, a casing for use with radial flow impellers is typically concentric with the impeller, as opposed to the volute-type casings. 
     Impellers used in centrifugal pumps may be further classified as single-suction or double-suction impellers, depending on the configuration in which liquid enters the eye of the impeller. A single-suction impeller allows liquid to enter the impeller eye from one side only, whereas a double-suction impeller allows liquid to enter the impeller eye from both sides. The double-suction arrangement has the advantage of balancing the end thrust in both respective directions. However, small capacity centrifugal pumps are usually of a single-suction design, which imposes an unbalanced thrust of the shaft thrust bearing that has to be taken into account, as well as unbalanced forces on the pump which may cause vibrations. 
     An improved design is required for a centrifugal pump with a double-suction impeller, having an easily scalable capacity and which is economical to manufacture. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, there is provided a casing for a pump comprising a circular body having at least two radial inlets, at least one peripheral outlet and at least one transversal aperture, a substantially circular impeller mounted within the body for rotation about the aperture, wherein the impeller has a substantially sinusoidal profile. 
     This casing and the sinusoidal impeller within advantageously maintain a stable flow output of a mix of at least two fluids fed into the body via the radial inlets. 
     The main axis of the peripheral outlet is preferably offset relative to the diameter of the body. The main axis of the peripheral outlet is preferably not tangential relative to the body periphery, i.e. the peripheral outlet preferably exits the body at an angle relative to the radial direction. 
     The body preferably comprises two opposed sides, wherein each radial inlet is located on a respective side of the pump body. In this configuration, the impeller is advantageously a double-suction impeller, wherein one or more fluids enter the impeller eye from both sides. 
     In a preferred embodiment, at least two peripheral outlets are transversally aligned with one another. In an alternative embodiment, at least two peripheral outlets are transversally offset relative to one another. The positioning of the at least two peripheral outlets may depend upon the fluid properties, casing size and impeller speeds, among other considerations. 
     The body is preferably made of a substantially non-resilient material. More preferably, the body is made of a substantially metallic material impervious to corrosion. More preferably still, the body is made of a chromium-titanium alloy. The choice of material for the body may depend upon the fluid properties, casing size and impeller speeds, among other considerations. 
     The body preferably comprises two sections releasably attached to one another. In a preferred embodiment, the transversal aperture is central relative to the body, each of the two sections is substantially frusto-conical about the aperture and has a peripheral wall substantially parallel to a main axis of the aperture. In this configuration, the two sections effectively define a substantially toroidal chamber when attached to one another. 
     The impeller shaft is supported on both sides between the two sections by a bearing, which is located within a groove in the external wall of each of the frusto-conial sections about the aperture. This configuration reduces vibrations of the shaft and the impeller and maintains the equilibrium of the impeller, resulting is increased efficiency and quieter operation. 
     The shape of the wall of each frusto-conical section corresponds closely to the rotating profile of the sinusoidal impeller. This configuration reduces turbulence and interferences within currents in the fluids, that may result from the movement of the impeller. This configuration also maximises power transfer from the rotating impeller to the fluids. The impeller is designed to occupy as little volume as possible, whilst still providing a high power-to-size ratio. 
     The impeller is preferably made of a substantially non-resilient material. More preferably, the impeller is made of a substantially metallic material impervious to corrosion. More preferably still, the impeller is made of a chromium-titanium alloy. The choice of material for the impeller may depend upon the fluid properties, casing size and impeller speeds, among other considerations. 
     Preferably, the impeller is continuously sinusoidal about its periphery. The amplitude of the sinusoid is substantially greatest at the periphery of the impeller and substantially minimal to non-existent nearest the eye of the impeller, uniformly about the impeller. That is, the amplitude of the sinusoid decreases in a radial direction, towards the eye of the impeller, uniformly about the impeller. 
     The angular frequency of the sinusoid defines the number of vanes of the impeller, on both sides of the impeller. The sinusoid is preferably a sine curve. Alternatively, the sinusoid may be a stepped sine curve, wherein a plurality of square steps combines to define substantially a sine over a cycle of the curve. The choice of sinusoid type for the impeller may depend upon the fluid properties, casing size and impeller speeds, among other considerations. 
     According to a second aspect of the present invention, there is provided a pump comprising a casing substantially as described above, a shaft engaging the impeller through the aperture, and means to power the shaft. 
     According to a third aspect of the present invention, there is provided a pumping system comprising at least two casings substantially as described above, a shaft for engaging the respective impellers of the at least two casings, and means to power the shaft, wherein the casings are disposed substantially adjacent one another and their respective impellers are co-axially mounted on the shaft. 
     According to a fourth aspect of the present invention, there is provided a method of pumping at least two fluids, comprising the steps of disposing at least two casings as described above substantially adjacent to and co-axially with one another, engaging the respective impellers of the at least two casings with a shaft, rotating the shaft with shaft powering means, feeding at least a first fluid in the first radial inlet of each casing, and feeding at least a second fluid in the second radial inlet of each casing. 
     Other aspects are as set out in the claims herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: 
         FIG. 1  is a top view of a first side of a casing for a pump according to a first embodiment of the present invention. 
         FIG. 2  is a top view of the second side of the casing of  FIG. 1 . 
         FIG. 3  is a lateral exploded view of the casing of  FIGS. 1 and 2 . 
         FIG. 4  is a lateral view of a section of the casing of  FIGS. 1 to 3 . 
         FIG. 5  is a top view of an impeller for use in the casing of  FIGS. 1 to 4  according to a first embodiment of the present invention. 
         FIG. 6  is a lateral view of the impeller of  FIG. 5 . 
         FIG. 7  is a top view of an impeller for use in the casing of  FIGS. 1 to 4  according to a second embodiment of the present invention. 
         FIG. 8  is a lateral view of the impeller of  FIG. 7 . 
         FIG. 9  is a lateral view of a pump having the casing of  FIGS. 1 to 4  configured with the sinusoidal impeller of any of  FIGS. 5 to 8 . 
         FIG. 10  is a lateral view of a pumping system having a plurality of casings of  FIGS. 1 to 4 , each configured with the sinusoidal impeller of any of  FIGS. 5 to 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description. 
     With reference to  FIG. 1 , there is shown a top view of a first side  101  of a casing  100  for a pump according to a first embodiment of the present invention. The casing  100  comprises a substantially circular body  102  having a first radial inlet  103  therein, which is located proximate a transversal aperture  104 . The aperture  104  is co-axial with the geometrical centre  105  of the body  102  and extends through both sides of the casing  100 . 
     With reference to  FIG. 2 , there is shown a top view of the second side  201  of the casing  100 , opposed to the first side  101 . The substantially circular body  102  has a second radial inlet  203  therein, which is also located proximate the transversal aperture  104 . In this embodiment, the first and second radial inlets  103 ,  203  are transversally aligned with one another. 
     With reference to  FIGS. 3 and 4 , the body  102  comprises two sections  301 ,  302  releasably attached to one another with suitable fastening means. Each section  301 ,  302  is substantially circular and of a same overall diameter. At least the first section  301  has a substantially cylindrical outer shape with an open end, which the second section  302  closes in use when the sections are secured to one another. The casing  100  is therefore substantially cylindrical itself. 
     In a preferred embodiment, nuts and bolts are used for releasably attaching the sections to one another. Through apertures are located about the periphery of the first section  301  within its cylindrical wall and corresponding through apertures about the periphery of the substantially disc-like second section  302 . In use, the second section  302  is centered relative to, and located against, the first section  301 , and bolts are threaded through their respective apertures aligned with one another, then releasably secured by threading nuts thereon. 
     The two sections  301 ,  302  are adapted to define a substantially toroidal chamber  303  within the body  102  when secured to one another, wherein the chamber  303  is bounded by the respective inner configurations of the two sections  301 ,  302  and a peripheral wall  304  extending from the first section  301  between the two sides  101 ,  201 , parallel to the main transversal axis of the body  102 . 
     The first section  301  comprises the peripheral wall  304  extending away from the first side  101  and a frusto-cone  305 A having at least a portion of the first body side  101  as its base, having a height equal to substantially half the width of the body  102  minus half the width of the impeller, and having a uniformly decreasing diameter between its base and its truncated extremity  306 A. The main transversal axis  307 A of the frusto-cone  305 A is co-axial with the main transversal axis of the body  102  and parallel to the peripheral wall  304 , thus the aperture  104  extends centrally through the first section  301  and the frusto-cone  305 A. 
     The wall of the aperture  104  adjacent the truncated extremity  306 A comprises a groove (not shown) suitable for accommodating a bearing which supports the impeller shaft on a first side. 
     In this embodiment, the base of the frusto-cone  305 A is substantially the entire diameter of the first body side  101 , minus the width of the peripheral wall  304 . A first portion of the chamber  303  is therefore defined by the tapered wall of the frusto-cone  305 A and the peripheral wall  304  of the body  102 . In alternative embodiments, the first portion of the chamber  303  may be further defined by a substantially planar inner wall of the first section  301  extending between the frusto-cone  305 A and the peripheral wall  304 . 
     The first section  301  further comprises the first inlet  103 , which is a through aperture extending between the first side  101  and the tapered wall of the frusto-cone  305 A. A first extremity  309 A of the first inlet  103  is located adjacent the aperture  104  on the first side  101  and the second extremity  310 A of the first inlet  103  is located adjacent the truncated extremity  306 A of the frusto-cone  305 A. The through aperture  309 A,  310 A is substantially rectilinear and parallel to the main transversal axes of the body  102  and the frusto-cone  305 A, therefore substantially parallel to the central aperture  104 . 
     The second section  302  comprises a frusto-cone  305 B having at least a portion of the second body side  201  as its base, having a height equal to substantially half the width of the body  102  minus half the width of the impeller, and having a uniformly decreasing diameter between its base and its truncated extremity  306 B. The main transversal axis  307 B of the frusto-cone  305 B is also co-axial with the main transversal axis of the body  102  and parallel to the peripheral wall  304  of the first section  301 , thus the aperture  104  extends centrally through the second section  302  and the frusto-cone  305 B. 
     The wall of the aperture  104  adjacent the truncated extremity  306 B also comprises a groove (not shown) suitable for accommodating a bearing which supports the impeller shaft on a second side. 
     In this embodiment, the base of the frusto-cone  305 B is substantially the entire diameter of the second body side  201 , minus the width of the peripheral wall  304 . A second portion of the chamber  303  is therefore defined by the tapered wall of the frusto-cone  305 B and the portion of peripheral wall  304  of the first section  301  which projects beyond the truncated extremity  306 A of its frusto-cone  305 A. In alternative embodiments, the second portion of the chamber  303  may be further defined by a substantially planar inner wall of the second section  302  extending between the frusto-cone  305 B and the same portion of peripheral wall  304 . 
     The second section  302  further comprises the second inlet  203 , which is a through aperture extending between the second side  201  and the tapered wall of the frusto-cone  305 B. A first extremity  309 B of the second inlet  203  is located adjacent the aperture  104  on the second side  201  and the second extremity  3108  of the second inlet  203  is located adjacent the truncated extremity  306 B of the frusto-cone  305 B. The through aperture  309 B,  310 B is substantially rectilinear and parallel to the main transversal axes of the body  102  and the frusto-cone  305 B, therefore substantially parallel to the central aperture  104 . 
     The peripheral wall  304  of the first section  301  comprises a peripheral outlet  314 , having a first extremity  315  substantially co-planar with the inner surface of the peripheral wall  304  and opening onto the chamber  303  and a second extremity  316  substantially co-planar with the outer surface of the peripheral wall  304  and opening to the outside of the casing  100 . The peripheral outlet  314  is substantially rectilinear between its two extremities  315 ,  316 . The peripheral outlet  314  has a main axis  317 , which is not tangential with the outer surface of the peripheral wall  304 , however at least a portion  318  of the surface of the peripheral outlet  314  is tangential with the inner surface of the peripheral wall  304 . The peripheral outlet  314  is therefore offset relative to the diameter of the body  102 . 
     With reference to  FIGS. 5 and 6 , an impeller  500  for use in the casing  100  is shown as a substantially circular, disc-like member, having a substantially sinusoidal periphery  501 . The amplitude of the sinusoid increases uniformly across the member in a radial direction, between the geometrical center  502  or impeller eye, which is substantially planar, and the sinusoidal periphery  501 , such that a plurality of radial volutes  503  are formed adjacent to one another about the member, each having an increasing dimension and volume towards the periphery  501 . 
     The increase in amplitude between the geometrical center  502  and the sinusoidal periphery  501  corresponds substantially to the acute angle between the frusto-cones  305 A,  305 B when the first and sections  301 ,  302  are secured to one another, so that volutes  503  of the impeller  500  occupy substantially the transversal height and radial length of the chamber  303 . 
     The shape of the wall of each frusto-conical section  305 A,  305 B corresponds closely to the rotating profile of the sinusoidal impeller  500 . This configuration reduces turbulence and interference within currents in the fluids in the chamber  303 , that may result from the rotation of the impeller  500 . This configuration also maximises power transfer from the rotating impeller  500  to the fluids. The impeller  500  is designed to occupy as little volume as possible, whilst still providing a high power-to-size ratio. 
     With reference to  FIGS. 7 and 8 , an alternative impeller  700  for use in the casing  100  is shown as a substantially circular, disc-like member, having a substantially sinusoidal periphery  701 . The amplitude of the sinusoid increases uniformly in discrete steps  704  across the member in a radial direction, between the geometrical center  702  or impeller eye, which is substantially planar, and the sinusoidal periphery  701 , such that a plurality of radial stepped volutes  704  are formed adjacent to one another about the member, each having an increasing dimension and volume towards the periphery  701 . 
     The increase in amplitude between the geometrical center  702  and the sinusoidal periphery  701  corresponds substantially to the acute angle between the frusto-cones  305 A,  305 B when the first and sections  301 ,  302  are secured to one another, so that stepped volutes  704  of the impeller  700  occupy substantially the transversal height and radial length of the chamber  303 . 
     With reference to  FIG. 9 , a pump  901  is shown wherein the impeller  500 ,  700  within a casing  100  is mated to a rotary shaft  902  driven by a power source  903 , for instance an electric or hydraulic engine. A first fluid enters the casing  100  on its first side  101  via suitable upstream piping  905  connected to the first inlet  103 , adjacent the impeller eye  502 ,  702 . A second fluid enters the casing  101  on its second side  201  via suitable upstream piping  906  connected to the second inlet  203 , adjacent the impeller eye  502 ,  702  and on its opposite side. Within the casing  100 , specifically the chamber  303 , the impeller  500 ,  700  is rotated by the shaft  902  whereby the fluids are channeled and driven by the volutes  503 ,  704  and mixed substantially peripherally. The mixed fluids exit the chamber  303  via the peripheral outlet  314  at a substantially constant flow rate. This pump advantageously provides a simple and economical double-suction impeller solution for relevant applications, which have hitherto considered double-suction impeller solutions impractical or uneconomical. 
     With reference to  FIG. 10 , a pumping system  1001  is shown wherein a plurality of impellers  500 ,  700  each within a respective casing  100 , are mated to a same rotary shaft  1002  driven by a power source  1003 , for instance an electric or hydraulic engine. A first fluid enters each casing  100  on its first side  101  via suitable upstream piping  1005  connected to the first inlet  103 , adjacent the impeller eye  502 ,  702 . A second fluid enters each casing  100  on its second side  201  via suitable upstream piping  1006  connected to the second inlet  203 , adjacent the impeller eye  502 ,  702  and on its opposite side. Within each casing  100 , specifically each chamber  303 , the impeller  500 ,  700  is rotated by the shaft  1002  whereby the fluids are channeled and driven by the volutes  503 ,  704  and mixed substantially peripherally. The mixed fluids exit each chamber  303  via its peripheral outlet  314  at a substantially constant flow rate. This system advantageously reduces the power and drive train requirements for applications which require several pumps. 
     Various aspects of the casing, impellers, pumps, pumping system and methods of installation and/or use of the present invention have been described. It will be appreciated that other embodiments of the invention which fall within the overall scope and spirit of the invention, but which differ in various detailed aspects, are conceivable. Improvements and modifications may therefore be incorporated herein without deviating from the scope of the invention. 
     The words “comprises”, “comprising”, “having” and “including” when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 
     The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.