BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to pump assemblies and, in particular, to impeller assemblies for centrifugal pumps.
2. Description of the Related Art
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.
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).
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.
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.
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
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.
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.
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.
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.
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
In the embodiment of FIGS. 2A, 2B, and 4A-4C, 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.