Rotary kinetic fluid motors or pumps – With means for re-entry of working fluid to blade set – Turbine regenerative pump
Reexamination Certificate
1999-11-12
2002-07-23
Kwon, John (Department: 3747)
Rotary kinetic fluid motors or pumps
With means for re-entry of working fluid to blade set
Turbine regenerative pump
Reexamination Certificate
active
06422808
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a regenerative pump, sometimes referred to as a toric pump, especially designed for economical mass production which is capable of developing higher pressures and flow rates at higher efficiencies than other pumps of comparable design and operating speed, by modifications made to the impeller and/or housing.
BACKGROUND OF THE INVENTION
In an automotive emission control system, a pump supplies air as required to the exhaust system between the manifold and the catalytic converter. In conventional regenerative pumps intended for use in an automotive emission control system, the impeller has straight radially extending blades at its outer periphery and is driven in rotation between a pump housing and a cover formed with a pump chamber. The pump chamber is formed symmetrical with respect to the rotatable impeller, and the surfaces of the housing and the cover. Further descriptions of toric pumps of this construction can be obtained from U.S. Pat. Nos. 5,302,081; 5,205,707 and 5,163,810.
Over time, industry needs have changed as restrictions on emissions have changed. It is now desirable to provide more air to an automotive emission control system than was previously required. Currently, it is desirable to provide at least between 19 and 20 cubic feet per minute (cfm). It is also desirable to meet the minimum fluid flow requirements while maintaining the same size housing. To meet these new fluid flow requirements, it has been necessary to double, and in some instances quadruple, the currently existing fluid flow rates of regenerative single stage pumps. Up to this point in time, the typical regenerative pump used in automotive emission control system applications has been capable of achieving a fluid flow rate of only 4 cubic feet per minute (cfm) at approximately 40 inches (H
2
O) head, and therefore, it is desirable in the present invention to provide a greater fluid flow output at the same or greater pressure for a given size housing configuration. It is further desirable in the present invention to reduce the electrical current or power requirements for a motor used in an electric motor driven pump for a given pressure and/or flow output. It is also desirable in the present invention to reduce the rotational speed of the motor required for a given pressure and/or flow rate output. Additionally, it is desirable in the present invention to increase overall efficiency and to provide for longer life and enhance reliability of regenerative pumps, and in particular, single stage, double channel, electrical air pumps or compressors.
SUMMARY OF THE INVENTION
In a regenerative pump according to the present invention, the rotor vanes of the peripheral regenerative pump are arcuate when viewed from the side, with the upper and lower portions curved forward in the direction of rotation. Preferably, a chamfer, or similar relief is formed on the convex side of the inner portion of all vanes. Bending the root portion of the vane to face forward and the addition of the chamfer are aimed at reducing pressure energy losses in the fluid entry region. Energy losses in the fluid entry region are the dominant loss in this type of regenerative pump. Prototypes of an impeller according to the present invention have been produced and tested. The test results have indicated a pressure increase, for the same rotational speed, of no less than 60% over the whole operating range and no less than 100% over a substantial portion of the whole operating range. In the tests, flow also increases over the operating range. Such dramatic increases in pressure and flow were unexpected.
The present invention also concerns double channel regenerative pumps of the type embodying a central rotor with vanes extending generally radially, either in a straight radial fashion, or in an arcuate fashion. Previously, it has been difficult to achieve a proper matching of the output of such a regenerative pump or compressor to the requirements of a particular application. Although some matching could be achieved by judicial choice of shaft rotational speed, pump efficiency can suffer in the process. Typically, a pump of this type includes a housing means for mounting a drive motor and one of the side channels, a rotor with generally radially extending vanes at its outer region on one or more axial sides of the rotor, and a cover sealingly engaged with the housing and a second side channel. The present invention allows matching of a pump's capacity to the requirements of a particular application without changing shaft rotational speed. Previously the channels and the housing and cover have been equal, or symmetrical in cross-section, and differ only at the channel ends where it is common to place transfer inlet and delivery passages from the housing channel to ducts in the cover or housing. In the present invention, the channels of the housing and cover are formed in a manner which is not symmetrical. The cover, which is freely accessible, can be replaced by alternative covers having channels of various depths, or the cover can be spaced axially outwardly from the impeller by insertable spacers of various depths to change the effective depth of the channel in the cover. Thereby, the specific output of the pump may be varied to suit different fluid flow requirements by providing the appropriate asymmetrical depth of channel. Prototypes of asymmetrical side channels have been constructed and tested. These tests show that a change in capacity of at least 20% can be achieved by varying the axial depth of the channel without loss in the overall efficiency of the regenerative pump. The prototype of the present invention that was tested included a spacer plate inserted between the housing and the cover. The plate increased one of the side channels by a depth according to the thickness of the plate. Thus, a deeper channel can be provided without requiring the costly and time consuming measure of manufacturing a new cover. The magnitude of enhancement to pump performance was unexpected.
A regenerative pump for adding energy to a fluid, according to the present invention, includes an impeller having an axis of rotation and axially spaced, radially extending first and second surfaces. A radially split casing encloses the impeller and has a fluid inlet and a fluid outlet separated by a stripper. The stripper generally has a close clearance to a periphery of the impeller. The casing has axially spaced, radially extending first and second side walls facing the first and second surfaces respectively. Axially and radially extending blade means is formed on an outer radial periphery of the pump for driving fluid from the inlet toward the outlet as the impeller rotates about the axis of rotation. Means, formed in at least one side wall of the casing, directs fluid back toward the impeller.
The blade means preferably includes a plurality of vanes spaced circumferentially around the outer radial periphery of the impeller. Each vane has a radially inward base portion extending in a generally trailing direction with respect to rotation of the impeller and a radially outward tip portion extending in a generally leading direction with respect to rotation of the impeller.
Chamfer means is preferably formed on the base portion of each vane for deflecting fluid from the inlet toward the pocket defined between two adjacent vanes and the casing. Preferably, the chamfer means is formed on a trailing edge of the base portion of each vane. The chamfer means may be formed at an angle with respect to a radially extending plane normal to the axis of rotation of the impeller at a range selected from between 10° and 45° inclusive. Alternatively, the chamfer means may be formed as a curved surface having a predetermined radius connecting a generally radially extending surface of each vane to a generally axially extending surface of the respective vane along a trailing edge.
The blade means may include a plurality of vanes spaced circumferentially around the outer radial periphery of the impeller, where e
Czarnowski Robert S.
Moss Norman
Borg-Warner Inc.
Dziegielewski Greg
Kwon John
Warn, Burgess & Hoffmann, P.C.
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