US 3647314 A
A high-efficiency, low-specific speed centrifugal pump comprised of a discontinuous discharge rotor with an axial inlet and radially extending discharge passageways, a spiral collector for directly receiving the flow of fluid from the discharge passageways and a diffusor aligned with and extending substantially fully across the discharge end of said collector.
Description (OCR text may contain errors)
United States Patent Laessig 1 Mar. 7, 197 2  CENTRIFUGAL PUMP 2,472,412 6/ 1949'  Inventor: Rudolf R. Laesig, Sumneytown, Pa.  Assignee: General Electric Company 3,162,135 12/1964 Nichols et 8| ..4l5/ 196  Filed: Apr. 8, 1970 FOREIGN PATENTS OR APPLICATIONS  Appl. No.: 26,685 386,232 1/1933 Great Britain.... ..415/203 529,613 9/1921 France.... ...415/203 [52 us. Cl ..415/206, 415/213, 417/420 732407 M966 Canada "415/196  ..F04d 1/00, F04d 13/02 Prim ry Examiner-Henry F. Raduazo  Field 01 Search ..415/196, 197, 204, 206, 213, Au0rney Aen g Henry w Kaufman, wm 415/219 203 Becker, Frank L. Neuhauser, Oscar B. Waddell and Joseph B,
Forman  References Cited UNITED STATES PATENTS  RACT A high-efficiency, low-specific speed centrifugal pump com- 538,050 4/1895 Swabel ..415/204 prised of a discontinuous discharge rotor with an axial inlet 885l08 41/1908 Twin! "415/204 and radially extending discharge passageways, a spiral collecl'3379l6 4/1920 "415/173 tor for directly receiving the flow of fluid from the discharge 1,986,836 1/1935 NlacNeille ..4l5/206 passageways and a diffuser aligned with and extending 26,094 10/1966 Zlmmerman "417/420 stantially fully across the discharge end of said collector.
619,736 2/1899 Edwards ..415/204 1,046,115 12/1912 Sebald ..415/196 3 Claims, 3 Drawing Figures /6 J4 ms a W CENTRIFUGAL PUMP BACKGROUND OF THE INVENTION There are many applications for low-specific speed, high-efficiency fluid pumps. Economic and physical limits of the power supply and pump, as for example in a portable, batterypowered fluid pump, may particularly require the use of a high-efficiency pump. Generally, vane or piston pumps are used where there are low-flow rate and high pressure requirements for pumping liquids. However, relatively high-friction losses cause such pumps to be of low efficiency. Centrifugal pumps have lower friction losses, but in the past have been unable to meet low-specific speed requirements at high efficiencies; i.e., efficiencies greater than 40 percent.
SUMMARY OF THE INVENTION Therefore, it is an object of the subject invention to provide a high efficiency centrifugal pump which meets low-specific speed requirements.
The subject invention fulfills the above-stated object by providing a centrifugal pump comprised of a discontinuous discharge rotor having an extended length axial intake passageway connected to a plurality of radially extending discharge passageways of constant or slightly convergent cross section, a spiral collector for directly receiving the fluid flow from the discharge passageways including a first portion of constant radial depth to minimize friction losses, and a diffusor aligned with and extending substantially across the outlet end of the spiral collector. The innermost leading edge of the diffusor is blunt in shape. This centrifugal pump structure provides pump efficiencies of greater than 40 percent when operating with a liquid at low-flow rates. The subject matter which is regarded as the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification.
BRIEF DESCRIPTION OF THE DRAWINGS The present invention, however, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:
FIG. 1 is a longitudinal, cross-sectional view of a centrifugal pump constructed in accordance with the subject invention;
FIG. 2 is a sectional view of the apparatus shown in FIG. 1 taken along the line Il-II and FIG. 3 is a sectional view of a modified portion of a centrifugal pump constructed in accordance with the subject invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Two, cross-sectional views of a centrifugal pump constructed in accordance with the subject invention are shown in FIGS. 1 and 2.
The pump is comprised of a two-part outer casing 12a, 12b, a rotor I4 rotatable within a cavity 16 in casing 12, a spiral collector 18 in casing member 12b circumferentially located about the outer edge of rotor 14, a diffusor 20 defined in casing member 12b aligned with the discharge end of spiral collector l8 and means 22 for coupling rotor 14 to a motor 24.
Casing I2 is made in two parts which are held together by suitable fastening means extending through holes 26 to effect ease of manufacture, assembly and disassembly. Casing member 120 has an inlet portion 28 which defines an inlet passageway 30 for the flow of fluid to rotor 14.
The rotor 14 has an extended length axial inlet passageway 32 aligned with inlet passageway 30 and defined in part by an inlet collar 34. Inlet passageway 32 is connected to a plurality of substantially radially extending passageways 36. In the particular embodiment shown in FIGS. 1 and 2 five equally spaced cylindrical passageways 36 are shown. However, any reasonable number of passageways equal to or greater than two of substantially any cross-sectional shape (for example,
square or rectangular) may be used. Also, the passageways may be of constant cross section, as shown, or of a slight radial convergency. Rotor collar 34 serves to prerotate and minimize turbulence of the fluid entering rotor 14. Also, the close fitting arrangement between collar 34 and casing member 12a serves as a seal for the fluid and acts as a bearing for rotor 14. The use of separate discrete discharge passageways 36 of substantially constant cross section tends to minimize turbulence and hence minimize energy losses due to secondary flow within rotor 14 while providing a discontinuous discharge of fluid into collecting spiral 18.
As shown in FIG. 2, spiral collector I8 is basically formed of two channel portions. The first channel portion 18a is of substantially constant radial depth and extends for slightly les than 180. The second channel portion 18b is aligned with and extends from first channel portion 18a with a gradually increasing radial depth in the counterclockwise direction. The width of the second channel portion is approximately the same as the width of the discharge passageways 36 or slightly larger. This configuration allows the velocity of the discharge flow from passageways 36 to be kept at from 70-100 percent of the rotor tip speed to avoid loss of dynamic head through sudden deceleration into a slower main stream. The constant radial depth of first channel portion 180 results in losses due to incomplete recovery of the dynamic head of the fluid leaving the discharge passageways into first channel portion 180. These losses, however, are more than made up by reduced frictional losses due to the substantial depth of the first channel portion.
Diffusor 20 is aligned with the discharge portion of collector 18. The inlet of diffusor 20 is substantially of the same area as the discharge area of collector 18. The area ratio of diffusor 20 (inlet to outlet area) is preferably about one to four with an angle of divergency a of from 3l5, optimally about 7. In a preferred embodiment the lower wall of diffusor 20 is from to 96 relative to a radial line from the center of rotor 14 to diffusor inlet; and a blunt innermost leading edge portion 40 for diffusor 20 is provided.
It has been experimentally found that the use of the blunt leading edge as opposed to a sharp leading edge significantly improves the static head obtainable at a given flow rate and a give rotor speed. The higher static head obtainable and hence higher pump efficiency becomes increasingly significant as the flow rate increases within the desired operating flow rate range.
It is highly desirable to have the inlet portion of diffusor 20 extend completely across the outlet portion of the spiral collector 18. While in the embodiment shown in FIG. 2 the diffusor extends substantially across the spiral collector, the embodiment shown in FIG. 3 provides a modified diffusor leading edge portion 40' cut water which extends so as to be closely adjacent the outer edge of rotor 14 to allow the diffusor inlet to extend more completely across the spiral collector outlet. This assures that substantially all the flow from the collector 18 passes into diffusor 20. Portion 40 diminishes the circumferential length of the first channel portion 18a of collector 18, but has negligible effect on its perfonnance.
Due to the discontinuous flow of fluid through spiral collector 18 because of the rotor design, it is speculated that the build up of a boundary layer on the leading edge 40 out water of diffusor 20 is interrupted, thus helping avoid separation from the diffusor wall.
Rotor 14 may be connected to a motor 24 or any other source of rotational power by a conventional direct coupling means. However, FIG. 1 shows magnetic coupling means 22 which has the advantage that no seal for moving parts is necessary between the rotor and motor 24.
Coupling means 22 is comprised of a rotor drive shaft 42 which may be integrally connected to rotor 14, an inner, driven magnet 46 which is rigidly attached to shaft 42, a driving member 48, a driving magnet 50 which is rigidly connected to driving member 48 and is circumferentially disposed about inner driven magnet 46, and a shaft 52 from motor 24 which is connected to driving member 48. A nonferromagnetic cap member 54 extends over the end of shaft 42 and between magnets 46 and 50 to seal fluid within the pump while allowing the magnetic drive action to take place.
Magnets 46 and 50 may either be annular in shape, as shown, or may be two or more separate magnets. The arrangement of magnets 46 and 50 is such that opposite poles of the two magnets are radially aligned to provide the magnetic attractive force necessary for transmission of rotary motion from motor 24 to rotor 14. The magnets also act as a bearing for shaft 42.
Pump efficiencies of greater than 40 percent have been achieved for a centrifugal pump having a structure as described for flow rates of 1-1.5 gallons/minute and pressures from 2.5-8.5 p.s.i.
it is clear that many modifications may be made by those skilled in the art to the particular embodiments described here and which do not depart from the true scope and spirit of the subject invention.
Thus it is intended that the scope of the subject invention be limited only by the appended claims.
l. A centrifugal pump comprising: a rotor having at least two substantial closed radially extending fluid passageways connected to an annular, axially extending unobstructed coilar at the radial inner ends thereof;
a casing for said pump including a cut water of blunt,
rounded shape and a spiral collector located circumferentially about said rotor for receiving the flow of fluid from said fluid passageways, the spiral collector having a first portion starting at a spaced distance circumferentially from said out water, radially disposed outwardly a short distance from the periphery of said rotor and at a constant radial distance from the axis of said -rotor for a segment greater than and said spiral collector having a spiral second shaped portion; and a diffusor aligned with and extending across the spiral shaped portion of said collector and forming an angle of divergency with said cut water from 3 to 15.
2. A pump as in claim 1 wherein the angle of divergency of said diffusor is 7.
3. A pump as in claim 1 wherein said rotor has five substantially radially extending fluid passageways.