Patent Publication Number: US-2003231959-A1

Title: Impeller assembly for centrifugal pumps

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates, in general, to pump assemblies and, in particular, to impeller assemblies for centrifugal pumps.  
       [0003] 2. Description of the Related Art  
       [0004] Centrifugal pumps are widely used in chemical, food, irrigation and other industries to pump a variety of liquids (e.g., water) and liquid-solid mixtures. Centrifugal pumps are a type of kinetic energy pump that imparts energy to a liquid through centrifugal force produced by a rotating impeller. The energy is used to increase the pressure of the liquid and move the liquid from one point to another.  
       [0005]FIG. 1 is a simplified cross-sectional depiction of a conventional centrifugal pump  10  that includes a stationary casing  12  and an impeller  14  with curved vanes  16  (also referred to as “blades” and shown as lines for simplicity) and an axially-disposed eye opening  18 . Rotation of impeller  14 , and thus curved vanes  16 , (e.g., by a motor [not shown] operatively coupled to impeller  14 ) within stationary casing  12  reduces the pressure at eye opening  18  of the impeller, causing liquid to flow into eye opening  18  from a suction inlet (e.g., an intake pipe, not shown).  
       [0006] Curved vanes  16  are configured to accelerate and direct the liquid away from eye opening  18 . Rotating curved vanes  16  of impeller  14  direct the liquid outward by centrifugal force, into stationary casing  12  and subsequently out a discharge exit  20 . The accelerated outward flow of the liquid (i.e., from eye opening  18  towards stationary casing  12 ) reduces the pressure at eye opening  18 , allowing more liquid to enter eye opening  18 .  
       [0007] A drawback of centrifugal pumps is that they must be “primed” prior to use. “Priming” is the addition of liquid to the casing in order to displace (i.e., evacuate) any entrained air, create a liquid seal within the casing and, thereby, prepare the pump for the initiation of liquid flow therethrough. Although self-priming centrifugal pumps (i.e., a centrifugal pump that is configured to automatically remove [evacuate] air from the suction inlet and that may handle liquids, gases and liquid-gas mixtures) are known, the time period required to complete a self-priming process in such self-priming centrifugal pumps may be undesirably long.  
       [0008] Still needed in the field, therefore, is a self-priming centrifugal pump that may complete a self-priming process in a relatively short time period. In addition, the self-priming centrifugal pump should be or a relatively simple and easily manufactured structure.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009] The present invention provides an impeller assembly for centrifugal pumps that enables self-priming in a relatively short time period. In addition, the impeller assembly is of a relatively simple and thus easily manufactured construction.  
       [0010] An impeller assembly for a centrifugal pump according to one exemplary embodiment of the present invention includes an impeller and at least one winglet. The impeller includes an impeller body with an eye opening therein. The eye opening is configured for the passage of a fluid (e.g., water) therethrough when the impeller assembly is in use. The impeller body also includes at least one vane, with a leading end, disposed about the eye opening. The winglet(s) are positioned to protrude into the eye opening of the impeller body and may, for example, be coupled to the leading end of the vane.  
       [0011] The provision of winglet(s) in the eye opening of impeller assemblies according to one exemplary embodiment of the present invention has been demonstrated to significantly reduce the time period required for a self-priming process when such impeller assemblies are used in centrifugal pumps. It is postulated, without being limiting, that this reduction is due to two effects. First, when in motion during use of the impeller assembly, the winglet(s) provide an air-foil-like dynamic with the eye opening that creates a vacuum-differential (also referred to as “lift”) effect. The vacuum differential (“lift”) effect enhances the evacuation of gas (e.g., air) from the centrifugal pump during a self-priming process. Second, moving winglet(s) serve to divide any gas bubbles (e.g., air bubbles) with which they come into contact into smaller gas bubbles. The smaller gas bubbles are more readily entrained in liquid passing through the centrifugal pump and, therefore, quickly evacuated from the centrifugal pump.  
       [0012] Furthermore, the inclusion of winglets in an impeller assembly according to one exemplary embodiment of the present invention results in simple and easily manufactured impeller assembly.  
       [0013] A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0014]FIG. 1 is a simplified cross-sectional depiction of a conventional centrifugal pump;  
     [0015]FIG. 2A is a simplified cross-sectional depiction of an impeller assembly according to one exemplary embodiment of the present invention;  
     [0016]FIG. 2B is a simplified cross-sectional depiction of the impeller assembly of FIG. 2A along line A-A.  
     [0017]FIG. 3 is a drawing depicting the cross-sectional shape of a winglet included in one embodiment of the present invention; and  
     [0018]FIGS. 4A, 4B and  4 C are simplified left-side, edge and right-side depictions, respectively, of an impeller body included in one embodiment of the present invention. 
    
    
     DESCRIPTION OF PREFFERED EXEMPLARY EMBODIMENTS  
     [0019]FIGS. 2A and 2B are simplified depictions of an impeller assembly  100  for use in a centrifugal pump in accordance with one exemplary embodiment of the present invention. Impeller assembly  100  includes an impeller  102  and six winglets  104  (shown in cross-section in FIG. 3). Impeller  102  includes a first impeller body  106  with an eye opening  108  therein, a second impeller body  110  (through which eye opening  108  also passes) and a keyway  112 . Eye opening  108  is configured for the passage of fluid (e.g., water) therethrough when impeller assembly  100  is in use in a centrifugal pump.  
     [0020] Winglets  104  are configured to protrude within eye opening  108  (see, for example, FIG. 2B) of impeller  102  and are also configured for movement in a predetermined pattern (e.g., the circular pattern indicated by arrow A of FIGS. 2B and 3) when impeller assembly  100  is in use in a centrifugal pump.  
     [0021] Referring to FIGS.  4 A- 4 C, first impeller body  106  includes six curved vanes  114  disposed within eye opening  108 . Each of the curved vanes  114  has a leading edge  116  that is located proximal to eye opening  108 . First impeller body  106 , curved vanes  114  and winglets  104  may be formed of any suitable material known to one skilled in the art including, but not limited to, PET white plastic.  
     [0022] In the embodiment of FIGS. 2A, 2B, and  4 A- 4 C, a winglet  104  is coupled to the leading edge  116  of each curved vane  114  by, for example, being formed as a unitary whole with curved vanes  114  of first impeller body  106 . Preferably, each winglet  104  is machine or molded as a solid part of a corresponding impeller vane but may also be a separate piece coupled appropriately, as one skilled in the art will understand, to a corresponding leading edge. Therefore, when first impeller body  106  and curved vanes  114  are rotated (e.g., at a rotation speed in the range of 10 rpm to 3,500 rpm), winglets  104  move in a circular pattern within eye opening  108 .  
     [0023] Preferably, entrance vane angles are selected from a chart provided in various engineering books, such as, for example, “The Pump Hand Book.” Such a chart allows one skilled in the art to select a preferred vane entrance angle using desired impeller efficiency and impeller specific speed.  
     [0024] Winglets  104  are configured to operate as rudimentary wings (i.e., airfoils) during movement in the predetermined pattern. This airfoil characteristic of winglets  104  is illustrated in FIG. 3. Winglets  104  have a trapezium (either quadrilateral or trapezoidal) cross-sectional shape and may be considered to possess a “top” side  200  and a “bottom” side  202 . Thus, winglets  104  substantially fill corresponding vanes  114  as may be seen in FIG. 4C and therefore the trapezium shape is preferable. The dimensions of sides  200 ,  202  are likewise selected to substantially fill vanes  114 . Once apprised of the present disclosure, one skilled in the art will recognize that other winglets of other cross-sectional shapes may be employed such as, for example, triangular or oblong cross-sectional shapes.  
     [0025] When a fluid (e.g., water or air) flows past winglet  104  it travels farther along top side  200  than over bottom side  202  (as illustrated by the dashed arrows of FIG. 3) creating a vacuum differential or lift effect within eye opening  108 . This effect facilitates evacuation of gas from a centrifugal pump during a self-priming process. In addition, the movement of winglet  104  serves to divide (i.e., break-up) large air bubbles into smaller gas bubbles that are more readily mixed with liquid and evacuated during a self-priming process.  
     [0026] The provision of winglet(s) that protrude into the eye opening of impeller assemblies according to one exemplary embodiment of the present invention has been demonstrated to significantly reduce the time period required for self-priming processes. For example, test results indicate that a conventional self-priming centrifugal pump that required five minutes to complete self-priming when pumping water required only thirty seconds when winglets were provided in the eye opening of the centrifugal pump.  
     [0027] It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that structures within the scope of these claims and their equivalents be covered thereby.