Abstract:
A pump apparatus comprising a series of stacked impellers rotating about a common axis, for pumping a viscous fluid mixture upwardly from an underground location. The pump apparatus comprises a generally cylindrical housing having an intake at or near its suction end. A plurality of impellers are mounted in the housing to rotate about a shaft, which each induce flow of the mixture toward the discharge end of the pump. Each impeller has a series of radially outwardly extending vanes, one or more of such vanes having a radially-extending horizontal slot and arranged to generate an upwardly moving column of fluid. Without being limited to the theory of operation, the horizontal slot in the vanes assists in creating laminar flow and reducing turbulent flow.

Description:
FIELD OF INVENTION 
       [0001]    This invention relates to centrifugal pumps, and in particular to a modified centrifugal pump consisting of a series of stages for pumping viscous fluids, with improved impeller configuration to modify the flow of fluid to thereby reduce wear due to abrasion caused by such viscous fluids. 
       BACKGROUND OF INVENTION AND DESCRIPTION OF THE PRIOR ART 
       [0002]    The extraction of heavy oil and/or bitumen from an underground hydrocarbon reservoir via the pumping of viscous hydrocarbon-containing mixtures to surface presents significant problems with respect to the erosion of mechanical equipment (such as the pumps) which are used to pump such viscous mixtures to surface. 
         [0003]    The cause of the erosion is due largely in part to the high abrasiveness of the viscous pumped substance, and the presence of solid particles in the mixture, such as sand, silicates, and tailings. 
         [0004]    In making its way through the pump mechanism, the viscous fluid particularly causes erosion of the impeller blades, which ultimately leads to wear and loss of performance, and indeed subsequent inoperability of the pump. The result of the ongoing wear on the apparatus causes significant downtime for repairs and replacements, increasing inefficiencies and ultimately increasing maintenance costs and pump failures. 
         [0005]    Pump apparatus with impeller blades used in the handling of viscous fluids are found in the prior art, such as those disclosed in Canadian Patents 2,543,970, 2,185,176, 2,229,018 and 2,235,045. 
         [0006]    Canadian Patent 2,543,970 teaches a centrifugal pump, having a wear plate coupled with a centrifugal pump and impeller apparatus. Wear plates add additional cost, and may in some cases reduce performance. 
         [0007]    CA 2,185,176 discloses a pump/separator apparatus that utilizes an inner impeller with a stack of radially and concentrically extending circular disks. 
         [0008]    Likewise, CA 2,229,018 discloses a pump/separator apparatus with impellers mounted within a cylindrical housing. The impellers found in CA 2,185,176 are in a diverging upwardly external shape. In CA 2,185,176 there are also internal pumping components located at each stack. 
         [0009]    CA 2,235,045 teaches an impeller assembly with asymmetric concave blades. 
         [0010]    However, there exists a real need in the industry for an pump apparatus that will provide substantial pressure and volumetric output, and be able to survive for an extended period of time without repair or replacement. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention provides an improved staged pump apparatus for handling viscous fluids, which reduces the limitations of conventional pumps being prone to erosion and frequent issues with maintenance. 
         [0012]    According to the invention, the improved impellers within the pump apparatus allow the pumping of viscous fluid upwardly in a laminar flow. By keeping the fluid in the laminar flow regime there is a decrease in the erosion of the impellers. 
         [0013]    The pump apparatus of the present is stackable, which allows for a series of impellers whose respective inlets and outlets are arranged in series to incrementally boost pressures within a narrow well borehole of limited diameter. 
         [0014]    Accordingly, in order to reduce the disadvantages of prior art centrifugal pumps being highly susceptible to erosion and wear when pumping viscous fluids having abrasive and wear-causing materials suspended therewithin, in a first broad embodiment of the present invention such invention provides a pump apparatus for pumping a viscous fluid upwardly, comprising: 
         [0015]    a hollow, cylindrical body disposed about a central longitudinal vertical axis, having aperture means proximate a lower extremity thereof to allow ingress of said viscous fluid about an exterior periphery thereof and to direct said viscous fluid upwardly along said longitudinal axis and within said cylindrical body; said hollow cylindrical body comprising therewithin:
       (i) a plurality of rotatable arcuate vane members, situated within said hollow cylindrical body and above said lower extremity and symmetrically radially disposed about said longitudinal axis, adapted for rotation about said longitudinal axis, each of said vane members extending radially outwardly from a position proximate said longitudinal axis to a position proximate an inner periphery of said hollow cylindrical body;   (ii) a flat, horizontally disposed disc member, disposed immediately above said vane members, perpendicularly disposed to said longitudinal axis;   (iii) a viscous fluid egress area proximate a radial extremity of said vane members and said disc member and situated about said periphery of said hollow cylindrical body; and   (iv) each of said vane members possessing a radially-extending horizontal slot, extending from proximate a mid-section of each of said vane members radially outwardly to a position proximate a radial extremity of each of said vane members.       
 
         [0020]    In a further broad aspect of the pump apparatus of the present invention, such pump apparatus is adapted to be coupled in series with at least one other pump apparatus along a vertical longitudinal axis thereof to provide a staged pump apparatus, for pumping a viscous fluid upwardly, comprising: 
         [0021]    (a) a hollow, cylindrical body disposed about said longitudinal vertical axis, having aperture means proximate a lower extremity thereof to allow ingress of said viscous fluid about an exterior periphery thereof and to direct said viscous fluid inwardly and upwardly along said longitudinal axis and within said cylindrical body; 
         [0022]    (b) a plurality of arcuate vane members, situated within said cylindrical body and above said lower extremity, adapted for rotation about said longitudinal axis, each of said vane members and extending radially outwardly from a position proximate said longitudinal axis to a position proximate an inner periphery of said hollow cylindrical body; 
         [0023]    (c) a flat, horizontally disposed rotatable disc member, rotatable within said hollow cylindrical body about said longitudinal axis, perpendicularly disposed to said longitudinal axis; 
         [0024]    (d) a viscous fluid egress area disposed above said vane members and situated about said periphery of said hollow cylindrical body: and 
         [0025]    (e) each of said vane members possessing a radially-extending horizontal slot, extending from proximate a mid-section of each of said vane members radially outwardly to a radial extremity of each of said vane members. 
         [0026]    In a third broad aspect of the invention, a centrifugal pump apparatus is provided which is, adapted to be coupled in series with other similar centrifugal pump apparatus along a vertical longitudinal axis thereof to provide a staged pump apparatus, for pumping a viscous fluid upwardly, comprising: 
         [0027]    (a) a hollow, cylindrical body disposed about said longitudinal vertical axis, having a lower horizontal wall perpendicularly disposed to said horizontal axis with a circular aperture therein co-axial with said longitudinal axis; 
         [0028]    (b) a horizontal circular disc at a lowermost extremity of said hollow cylindrical body, perpendicularly disposed to said longitudinal axis and of lesser diameter than said cylindrical body, having an upwardly-extending cylindrical tubular member situated co-axial with said vertical longitudinal axis, adapted to receive a rotatable cylindrical shaft therein, said disc affixed to said lower horizontal wall and beneath said lower wall but spaced apart therefrom thereby forming aperture means beneath a lower extremity of said cylindrical body adapted to allow ingress of said viscous fluid about an exterior periphery of said cylindrical body and to direct said viscous fluid inwardly and upwardly along an exterior of said cylindrical member and within said cylindrical body; 
         [0029]    (c) a plurality of rotatable vertically-extending vane members, situated within said cylindrical body and above said lower extremity, disposed about said longitudinal axis adapted for rotation about said longitudinal axis, each of said vane members extending radially outwardly from a position proximate said longitudinal axis to a position proximate an inner periphery of said cylindrical body and each adapted to propel said viscous fluid directed upwardly within said cylindrical body via said cylindrical member radially outwardly; 
         [0030]    (d) a flat, horizontally disposed rotatable disc member, of lesser diameter than said cylindrical body, rotatable within said hollow cylindrical body about said longitudinal axis; and 
         [0031]    (e) each of said vane members possessing a radially-extending horizontal slot, extending from proximate a mid-section of each of said vane members radially outwardly to a radial extremity of each of said vane members. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    Additional advantages will become readily apparent to those skilled in the art from the following detailed description, wherein only preferred examples of the present concepts are shown and described. 
           [0033]    Specifically, as will be realized, the disclosed concepts are capable of other and different embodiments, and Us several details are capable of modifications in various obvious respects, all without departing from the spirit thereof. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive. Further advantages and permutations will appear from the following detailed description of various non-limiting embodiments of the invention, taken together with the accompanying drawings, in which: 
           [0034]      FIG. 1  is a perspective, exploded view of a single centrifugal pump stage of the present invention; 
           [0035]      FIG. 2  is a cross-sectional depiction of a staged centrifugal pump apparatus of the present invention, comprising a series of stacked and nested impeller stages; 
           [0036]      FIG. 3  is an enlarged view of the lower (ie suction) portion of the centrifugal staged pump apparatus shown in cross-section in  FIG. 2 ; 
           [0037]      FIG. 4   a  is a side cross-sectional view of the upper portion of the hollow cylindrical pump body of the present invention; 
           [0038]      FIG. 4   b  is a view on arrow “A” of  FIG. 4   a;    
           [0039]      FIG. 5   a  is a side cross-sectional view of the entire cylindrical pump body of the present invention, showing the manner of attachment of the hollow circular disk to the lower horizontal wall of the cylindrical body shown in  FIG. 4   a;    
           [0040]      FIG. 5   b  is a view on arrow “A” of  FIG. 5   a;    
           [0041]      FIG. 6   a  is a side cross-sectional view on the impeller and rotatable vanes which form part of the pump apparatus of the present invention; 
           [0042]      FIG. 7   a  is a side cross-sectional view of the rotatable disc member of the present invention; 
           [0043]      FIG. 7   b  is a view on arrow “A” of  FIG. 7   a;    
           [0044]      FIG. 8   a  is a side cross-sectional view of the impeller, rotatable disc, and flange member which are contained in the cylindrical body of the pump apparatus of the present invention; 
           [0045]      FIG. 8   b  is a view on arrow “A” of  FIG. 8   a;    
           [0046]      FIG. 8   c  is a cross-sectional view of the flange member shown in  FIG. 8   a;    
           [0047]      FIG. 9   a  is a top view of a series of stacked nested centrifugal impellers which comprise part of the pump apparatus of the present invention; 
           [0048]      FIG. 9   b  is a side cross-sectional view of a series of stacked, nested centrifugal impellers which comprise part of the pump apparatus of the present invention; 
           [0049]      FIG. 9   c  Is a view on arrow “A” of  FIG. 9   b;    
           [0050]      FIG. 10  is a side cross-sectional view of a series of stacked, nested centrifugal impellers which comprise part of the pump apparatus of the present invention, similar to the view shown in  FIG. 9   b , but showing a different embodiment for the series of nested stacked impellers and the manner of nesting them; 
           [0051]      FIG. 11  is an enlarged view of the upper discharge end of the centrifugal pump apparatus of the present invention, as shown in  FIG. 2 ; and 
           [0052]      FIG. 12  is a graph of flow rate vs. head from an experimental test result using a 15-stage centrifugal pump apparatus of the present invention, using liquid silicone as the viscous medium. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0053]    In all drawings figures, for consistency, identical components are identified with identical reference numerals. 
         [0054]      FIG. 1  shows a perspective, exploded view of a single centrifugal pump stage  10  of the present invention. 
         [0055]      FIG. 2  shows an assembled cross-sectional view of the pump apparatus  100  of the present invention, comprising a plurality of pump stages  10  assembled end to end in series. 
         [0056]    Generally speaking, for a pump apparatus  100  of the present invention, with each additional pump stage, the pressure head output is incrementally increased by the addition of successive numbers of pump stages  10 . For example, if at a certain pump rpm (eg 3500 rpm—see Example 1, below) each pump stage  10  has an incremental pressure head of 8.4 psi, by combining each in series a combined pump apparatus  100  pressure head of 126 psi (15×8.5) can be achieved. 
         [0057]    With reference to the exploded view shown in  FIG. 1 ,  FIG. 1  shows an exploded view of a single pump stage  10  of the present invention comprising a hollow cylindrical body  12  disposed about a central longitudinal vertical axis  14 . Cylindrical body  12  has a lower horizontal wall  15 , having a circular aperture  16  therein which is co-axial with the longitudinal axis  14 . 
         [0058]    A horizontal disc  18  is provided at a lowermost extremity of cylindrical body  12 , perpendicularly disposed to longitudinal axis  14 , of a lesser diameter than an outer uppermost periphery  21  of cylindrical body  12 . Extending upwardly from horizontal disk  18  is a cylindrical tubular member  22 , which is situated co-axial on longitudinal axis  14 . Cylindrical tubular member  22  is adapted to receive a rotatable cylindrical shaft  23  therein (see  FIGS. 2 ,  3  &amp;  11 ) 
         [0059]    Horizontal disc  18  is affixed to lower horizontal wall  15  by means of a series of struts  24  (best view shown in  FIG. 5   b ), so as to be spaced apart from horizontal wall  15 . Accordingly, and as seen from  FIG. 1 , by horizontal disc  18  being spaced apart from horizontal wall  15  an annular space  25  through which a viscous medium (not shown) can enter pump stage  10  is thereby created. 
         [0060]    As best shown in  FIGS. 5   a  &amp;  5   b , horizontal disc  18  and integral cylindrical tubular member  22  may be affixed to cylindrical body  12  by way of a series of steel dowel pins  31 , as shown in  FIGS. 5   a  and  5   b . Alternatively horizontal disc  18  may be affixed to cylindrical body  12  by any one of a number of means known to persons of skill in the art, such as by welding, threadable coupling, brazing, or being integrally formed with cylindrical body  12 . 
         [0061]    The viscous medium desired to be pumped enters annular area  25  as shown in  FIG. 1  and is drawn upwardly through aperture  16  via the impeller assembly  26  as hereinafter explained. In the nested, end-to-end series of pump stages  10  shown in  FIGS. 2 &amp; 3  which together comprise the pump apparatus  100  of the present invention, the viscous fluid medium being pumped enters the pump apparatus  100  via suction end  30 , and is discharged at discharge end  40 . 
         [0062]    Immediately above horizontal wall  16  the impeller assembly  26  is positioned. Impeller assembly  26  comprises a plurality of rotatable arcuate vane members  27 , situated within hollow cylindrical body and above a lower extremity  32  thereof, namely above horizontal wall  15 . Each of vane members  27  are symmetrically radially disposed about longitudinal axis  14  as best shown in  FIG. 1  and are adapted for rotation about said longitudinal axis  14 . Each of said vane members  27  extend radially outwardly from a position proximate said longitudinal axis  14  to a position proximate an inner periphery  33  of hollow cylindrical body  12 , as again shown in  FIG. 1  and also  FIG. 2 . 
         [0063]    Importantly, each of vane members  27  possess a radially-outwardly extending horizontal slot  41 , extending from proximate a mid-section of each of said vane members  27  radially outwardly to a position proximate a radial extremity  42  of each of said vane members  27 . 
         [0064]    Without being held to a definite explanation as to why the incorporation of horizontal slots or apertures  41  proximate the extremity  42  of an impeller vane  27  as best shown in  FIG. 1  and  FIG. 8   a  assists in reducing wear on impeller components when viscous fluids (containing abrasive wear-inducing suspended particles) are pumped, it is theorized that in viscous fluids, due to the large increase in speed that occurs as such fluid is pushed by the impeller vanes radially outwardly, that flow in the area of the vanes  27  in which the horizontal slots  41  are situated becomes extremely turbulent, thereby causing greater circulation and contact of abrasive components against pump components. By providing an aperture or horizontal slot  41  proximate the radially-most outward portion  42  of the vane  27 , preferably in the area midsection of the vane  27  where the exit speeds of the fluid are normally highest, the speed of the pumped fluid in this localized area can be reduced, thereby allowing fluid which may be in a boundary layer proximate to pump equipment to be entrained as approximately the same speed. It is theorized that the resultant effect is that laminar flow is able to be maintained over a greater portion of the fluid flow within each pump stage  10 , thereby increasing the speed of fluid through each pump stage  10  and the increasing the efficiency of the pump apparatus  100  for the horsepower expended. 
         [0065]    Above vanes  27  a flat horizontally disposed disc member  50  is provided, disposed immediately above said vane members  27  and perpendicularly disposed to longitudinal axis  14 . In a preferred embodiment, disc member  50  is fixedly coupled to each of vanes  27  by means of steel dowel pins  60  inserted in apertures  61  in disc member  50 , as shown in  FIGS. 8   a ,  8   b,  and disc member  50  is rotatable with the vanes  27 . Of course, other means of affixing disc member  50  to vanes  27  may be used as are known to persons of skill in the art, such as by welding or brazing. Alternatively, the vanes and disc member  50  may be milled from a single billet of material. 
         [0066]    A cylindrical annular member  61  integral with disc member  50  extends perpendicularly vertically upwardly from horizontal disc member  50 . Annular member  61  and disc member  50  are adapted to be positioned co-axially along longitudinal axis  14 . As seen in  FIG. 1 , the diameter of disc member  50  is less than the inner diameter of inner periphery  33  of pump body  12 , while the outer diameter of annular ring member  71  on which vanes  27  in a preferred embodiment are situate is substantially equal to the inner diameter of inner periphery  33  of pump body  12 , to allow formation of an annular aperture  73  where fluid being expelled radially outwardly from vanes  27  can be forced into the resulting annular aperture  73  and hence upwardly in pump stage  10  into the inlet area  26  of a further pump stage  12  which is stackably nested within the upper portion  21  of pump body  12 , as shown in  FIGS. 2 ,  3 ,  9   b ,  10  &amp;  11 . 
         [0067]    Disc member  50 , on the underside thereof and opposite annular member  61  thereof, has a downwardly extending curvilinear member  90 , as shown in  FIG. 1  and also in  FIG. 9   b  and  FIG. 10 . Curvilinear member  91  possesses a smooth curved surface, to introduce uniformly viscous fluid which is drawn upwardly into rotating vanes  27 , which thereafter expel such viscous fluid radially outwardly against inner periphery  33  of outer body  12  and into annular aperture member  61  and curvilinear member  90  co-operate to together form a vertical tubular aperture  57  through the entirety of disc member  50 , through which rotatable shaft  23  may be inserted. Notably, tubular aperture  67  possesses a keyed shaft or female spline  98 , which is adapted to matingly engage a similar male keyed spline  99  on shaft  23 , so that shaft  23  may turn impeller assembly  26  and vanes  27 . Rotatable shaft at each of its opposite ends  101   a ,  101   b,  possesses a series of splines, to allow mating engagement with a motor shaft to power pump apparatus  100 . 
         [0068]    Notably,  FIG. 9   b  and  FIG. 10  show two alternative configuration for cylindrical tubular member  22  on circular disc  18 , which has circular aperture  51  therein for receiving rotatable shaft  23 . In a first embodiment shown in  FIG. 9   b,  cylindrical tubular member  22  has a greater inner diameter than the outer diameter of curvilinear member  90 , and curvilinear member  90  is nestably inserted within tubular member  22 , as shown in  FIG. 9   b.    
         [0069]    In an alternative configuration for tubular member  22  shown in  FIG. 10 , tubular member is of a lesser height, and in such configuration a lower portion  91  of curvilinear member  90  abuts upper portion  62  of annular member  61 . 
       EXAMPLE 1  
       [0070]    The pump apparatus  100  of the present invention was tested on the 100 hp test bench with silicone oil. Due to the horsepower limitation of the test bed, the pump apparatus was only used with fifteen pump stages  10 , and thus only had a lift of 150-200 m of the viscous fluid (described below)in order to keep the hydraulic torque manageable. 
         [0071]    The prototype pump apparatus  100  of the present invention was tested with fifteen stages, with a design of approximately  20  of lift per pump state  10 . 
         [0072]    Each pump apparatus comprised an impeller assembly  26  having eight vanes, arcuate as shown in the attached Figures, of approximate 90 mm in height, with an outer portion of each vane  42  forming a circular periphery of approximately 82 mm. 
         [0073]    Importantly, horizontal slots  41  in the outer periphery of each vane  27  were of approximately 2 mm in height, and covered an arcuate length on each vane  27  of approximately 28 mm of an approximate 50 mm (mid vane) arcuate length. 
         [0074]    The pump apparatus  100  was tested at various speeds to determine the impact on performance and efficiency. In addition to the standard 3500 RPM, tests at speeds of 500, 1000, 1750, and 3000 RPM were completed. 
         [0075]    The viscous fluid medium used was silicon oil having a viscosity of 5,000 cP at the measured operating temperature of 20° C. In the silicone oil test setup, the motor (not shown) used to power rotatable shaft  23  of pump apparatus  100  was coupled via spline coupling  80  to pump apparatus  100 . Pump apparatus  100  drew directly via suction end  30  thereof from a tank of silicone in an open loop system. There was only 1-2′ of fluid level above the suction end  30  when immersed in silicone oil. 
         [0076]    Data was collected for speed, reactive motor torque, flow rate, and discharge pressure. 
       (i) Test Results 
       [0077]    The pump apparatus  100  was tested at 500, 1000, 1750, 3000, and 3500 RPM. The test results are shown in  FIG. 12 . 
         [0078]    Pump head of pump apparatus  100  gradually declined as flow rate increased, with a maximum pump efficiency being reached at a flow rate of approximately 20 m 3 /Day. The no-load flow rates varied from 40 m 3 /D at 1000 RPM, to 100 m 3 /D at 1750 RPM, to as high as 170 m 3 /D at 3500 RPM. The maximum lift achieved was 89 m (127 psi, 292 feet) when running at 3500 RPM. With 15 stages in pump apparatus, this equates to 19 feet of lift per stage, which is very close to the stated design lift of 20′ per stage. 
         [0079]    The pump apparatus  100  efficiency curve for 3500 RPM is overlaid on the performance chart in  FIG. 12 . 
         [0080]    Although the disclosure describes and illustrates preferred embodiments of the invention, it is to be understood that the invention is not limited to these particular embodiments. Many variations and modifications will now occur to those skilled in the art. For a complete definition of the invention and its intended scope, reference is to be made to the summary of the invention and the appended claims read together with and considered with the disclosure and drawings herein.