Regenerative pump with improved suction

Poor inlet suction characteristics in regenerative pumps may be avoided in a construction including a housing (10) having an impeller receiving cavity (20) with a circular impeller (22) therein. Channel-like annular grooves (32, 34) are disposed in the housing (10) and open to the cavity (20) at sides (36, 38) of the impeller (22). An outlet seal (63) is located in each of the grooves (32, 34) and outlet ports (62) opening to the grooves (32, 34) are located just upstream of the outlet seal (63). Peripheral recesses (42, 44) are located in the impeller sides (36, 38) and have radially inner extremities (59) located radially inward of the channels (32, 34). A plurality of blades (52) are mounted to the impeller (22) within the recesses (42, 44) around the periphery thereof and have radially inner edges (54) spaced from the radially inner recess extremities (59) while being isolated from recirculation within the channels ( 32, 34). An inlet port (70) is disposed in the housing (10) and is located between the radially inner extremity of the grooves (42, 44) and the radially inner edges (54) of the blades (52).

FIELD OF THE INVENTION 
This invention relates to regenerative pumps, and more particularly, to a 
regenerative pump with improved suction performance at its inlet. 
BACKGROUND OF THE INVENTION 
Regenerative pumps have found favor in a number of environments where 
moderate flow rates at relatively high pressures are desired. A typical 
regenerative pump is capable of delivering fluid at a head two or three 
times greater than that of a conventional, single stage centrifugal pump. 
Because of this, where simplicity is desired, resort has been to 
regenerative pumps to avoid having to utilize multiple stage pumping 
systems to achieve the desired pressures. 
Unfortunately, regenerative pumps heretofore known have had rather poor 
suction characteristics, particularly when operating upon a liquid near 
its boiling point. As the pump attempts to draw liquid into the pumping 
mechanism, the inlet pressure at the pump is reduced and the overall 
pressure rise and associated volumetric flow delivery of the pump falls 
off sharply as a consequence of cavitation. And, of course, as the 
temperature of the liquid being pumped approaches its boiling point, even 
a small reduction of pressure at the inlet increases the flash off of 
liquid to vapor, further complicating the cavitation problem. 
The present invention is directed to overcoming one or more of the above 
difficulties. 
SUMMARY OF THE INVENTION 
It is the principal object of the invention to provide a new and improved 
regenerative pump. More specifically, it is an object of the invention to 
provide such a pump with improved inlet suction characteristics. 
An exemplary embodiment of the invention achieves the foregoing object in a 
regenerative pump construction including an impeller mounted for rotation 
about an axis, a housing containing the impeller within an impeller 
cavity, and an annular recirculation channel in the housing which opens to 
the cavity at a side of the impeller. The housing includes an outlet from 
the channel and a seal blocking the channel just downstream of the outlet. 
A peripheral recess is located on the impeller on the side thereof facing 
the channel. The recess extends radially from a location well radially 
inward of the channel to a location having a substantial radial overlap 
with the channel. A series of blades are disposed on the side of the 
impeller within the recess and have radially inner edges located no 
further radially outward than the radially inner extremity of the channel. 
The radially inner edges further are radially outward of the radially 
innermost part of the recess so that an open annulus exists at the 
radially innermost part of the recess. An inlet is radially aligned with 
the annulus and an inlet seal extends from the housing into the annulus 
about the cavity except at the inlet. 
As a consequence of the foregoing construction, an inlet for a liquid to be 
pumped is located at the radially innermost edges of the impeller blade. 
At this location, of course, for any given annular velocity of the 
impeller, relative motion between the liquid to be pumped and the blades 
is the least, thereby minimizing difficulties due to cavitation. 
In a highly preferred embodiment, the radially inner edges of the blades 
are also leading edges for the blades in the direction of impeller 
rotation and are at a low inlet angle to further improve suction at the 
inlet. 
In a highly preferred embodiment, the radially inner edges or leading edges 
of the blades are located well radially inward of the radially inner 
extremity of the channel. This preferred form of the invention provides 
isolation between occurrences at the inlet and occurrences within the 
recirculation channel. 
In a highly preferred embodiment, the low inlet angle is measured 
tangentially of the inlet port and is about 20.degree. or less. Even more 
preferably, the low inlet angle is about 15.degree. or less. 
A highly preferred embodiment further contemplates that the blades be 
curved so as to be concave in the direction of rotor rotation. 
The curve is part of a spiral in a highly preferred embodiment. 
Additionally, the invention contemplates the provision of splitter blades 
between the first mentioned blades. 
Generally, but not always, the radially inner edges of the blades are 
parallel to the rotational axis of the impeller. Generally, but not 
always, the blades have a uniform height across their length. 
Other objects and advantages will become apparent from the following 
specification taken in connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An exemplary embodiment of a regenerative pump made according to the 
invention is illustrated in FIG. 1 and is seen to include a pump housing, 
generally designated 10. The housing 10 is made up of two sections 12 and 
14 clamped together on a parting line 16 by a plurality of cap screws 18 
(only one of which is shown). 
The sections 12 and 14 together define an impeller cavity, generally 
designated 20, which is substantially filled by a circular, disk-like 
impeller, generally designated 22 mounted on a shaft 24. A key 26 secures 
the impeller 22 to the shaft 24 for rotation therewith about an axis 25. 
The housing 10 may mount one or more sets of bearings for the shaft 24. 
Also included is a shaft seal 28. 
An annular groove 30 in the housing section 12 is adapted to receive an 
O-ring 31 to seal the inner face of the housing sections 12 and 14 at the 
parting line 16 and radially outward of the cavity 20. 
As can be seen in FIG. 1, the cavity 20 includes a pair of groove-like 
recirculation channels 32 and 34. The channels 32 and 34 are generally 
annular about the axis of the shaft 24 except for a so-called outlet seal 
to be described hereinafter. They both open to the cavity 20 in the axial 
direction and toward a respective side 36 or 38 of the impeller 22 at a 
location near its periphery 40. The impeller 22, in turn, includes 
respective peripheral recesses 42 and 44 on opposite sides. The recesses 
42 and 44 have their radially outermost extremity which will be at or near 
the periphery 40 at or near the radially outermost extremity 46 or 48 of 
the corresponding channel 32 or 34. As illustrated in FIG. 1, typically 
the channels 32 and 34 will be of semi-circular cross section to 
facilitate regenerative flow of fluid as illustrated by arrows 50. Other 
shapes may be used if desired. 
A plurality of blades 52 is located in each of the recesses 42 and 44. The 
blades 52 have radially inner edges 54 that are located no further 
radially outward from the axis of the shaft 24 than the radially inner 
extremity 56 of the channel 32 or the radially inner extremity 58 of the 
channel 34. As will be seen, in a highly preferred embodiment, it is 
preferred that the radially inner edges 54 of the blades 52 actually be 
located substantially radially inwardly of the radially inner extremities 
56, 58 of the channels 32 and 34. The radially innermost extremities 59 of 
the recesses 42, 44 are located well radially inward of the inner 
extremities 56, 58 of the channels 32, 34. 
It will be observed that each of the housing sections 12 and 14 includes a 
substantially peripheral, annular lip 60, 61 which forms part of an inlet 
seal (to be described in greater detail hereinafter) and underlies the 
radially inner edges 54 of the blades 52 at a relatively close clearance. 
As a consequence of this construction, recirculation within the channels 
32 and 34 is essentially forced to take place radially outward of the 
inner edges 54. 
Turning now to FIG. 2, other structural aspects of the embodiment of FIG. 1 
will be disclosed in connection with the right hand side of the pump 
illustrated in FIG. 1, it being understood that the left hand side will be 
a mirror image of that about to be described. 
At any desired location about the channel 34, an outlet port 62 may be 
located within the housing section 14. Immediately downstream of the 
outlet port 62 is a so-called outlet seal 63 in the form of an 
interruption of the channel 34. That is to say, one side 64 of the outlet 
seal blocks the channel 34 on the downstream side of the outlet port 62 
while an opposite side 66 is located a short angular distance away from 
the side 64 in the direction of rotation of the impeller 22, which 
direction is illustrated by an arrow 68. 
At or about the same angular location as occupied by the side 66 of the 
outlet seal 63, but radially inward of the radially inner edges 54 of the 
blades 52 is an inlet port 70. As illustrated, the inlet port 70 has an 
arcuate extent of approximately 90.degree., but a greater or lesser 
angular extent is contemplated depending upon desired design parameters. 
Extending from one side 72 of the inlet port approximately three-quarters 
of the way about the rotational axis of the shaft 24 to the opposite side 
74 of the inlet port 70 is a so-called inlet seal 76. The inlet seal 76 
may have the configuration closely similar to that of the annulus in the 
recess 42 or 44 defined by the radially inner extremity 78 or 79 of the 
recess 42 or 44 and the radially inner extremity 54 of the blades 52 as 
illustrated in FIG. 4, in connection with the recess 42. Alternatively, 
the inlet seal 76 may have the configuration of the lip 60 or 61 as 
illustrated in FIG. 1. 
Returning to FIG. 2, the blades 52 are seen to be curved and more 
specifically, curved to be concave in the direction of impeller rotation 
68. However, the blades could be straight if desired. The angle of each 
blade 52 to the tangential increases in the radial direction. That is, as 
the distance from the axis 25 increases, the angle .THETA. will increase. 
Generally, in choosing blade configuration, it is desirable that the angle 
.THETA. be selected so that loading of the blades 52 at their leading 
edges (or radially inner edges 54) is relatively low. Preferably, but not 
always, splitter blades 80 will be located between pairs of the blades 52. 
As is well-known, splitter blades have their radially inner ends 82 well 
radially outward of the radially inner ends 54 of the main blades 52. The 
splitter blades keep blockage of the inlet down while maintaining enough 
blade surface at the radially outer tips to obtain good pressurizing of 
the fluid being pumped. 
According to the invention, the radially inner edges 54 of the blades 52 
are the leading edges of the blades 52 considering the direction of 
impeller rotation as shown by the arrow 68. Preferably, the leading edges 
are at a low inlet angle for improved suction performance. A low inlet 
angle will be measured between a line tangent to the surface of the blade 
52 at the leading edge 54 and a line tangent to a circle centered on the 
shaft axis and passing through the leading edge 54, the line also passing 
through the leading edge 54. That is to say, the last named line will 
essentially be tangential to the inlet 70. The angle .THETA. is indicated 
in FIG. 2 and typically will be about 20.degree. or less. In a preferred 
embodiment, the angle will be about 15.degree. or less. 
A highly preferred embodiment of the invention is illustrated in FIG. 3. In 
this embodiment, where like structure is employed, like reference numerals 
are utilized and those components will not be redescribed. 
Of particular note in the embodiment of FIG. 3 is the location 58 of the 
radially inner extremity of the channel 34 in relation to the radially 
inner edges 54 of the blades 52. It will be observed in both FIGS. 3 and 4 
that the recirculation channels 32 and 34 are spaced radially outward of 
the leading edges 54 by a substantial distance because the radially inner 
extremities 56 and 58 of the channels 32 and 34 are located well radially 
outward of the leading edges 54. By so locating the leading edges 54, 
during pump operation, their relative movement with respect to the 
incoming fluid at the inlet 70 is reduced because they may be closer to 
the axis 25 of the shaft 24. As suction performance is inversely 
proportional to circumferential velocity, lowering such velocity by moving 
the leading edges 54 radially inward improves suction performance. 
In some cases, it may be desirable to close off the recesses 42 and 44 in 
the side of the impeller 22 near its periphery 40. Thus, as shown in FIG. 
4, a web 90 separating the recesses 42 and 44 flares axially as at 92 and 
94 to the periphery 40. In general, a generous curve 96 or 98 at both 
extremities of the recesses 42 and 44 will be desired to reduce turning 
losses at the inlet 70 and reduce losses in recirculation within the 
recirculation channels 32 and 34 and the aligned part of the recesses 42 
and 44. 
From the foregoing, it should be appreciated that a regenerative pump made 
according to the invention will attain enhanced performance because of 
improved suction performance. Importantly, as compared to many prior art 
pumps, the leading edges of the impeller blades are not perpendicular to 
the axis of rotation. The same are illustrated as parallel to the axis of 
rotation, but may be of an intermediate value between perpendicular and 
parallel. This configuration simplifies manufacture of blades with leading 
edges at relatively low blade angles to enhance suction performance. 
The arrangement of components also allows the leading edge of the blades to 
be located closer to the rotational axis of the impeller to further 
enhance suction performance. 
While the impeller blade height (the length of each blade measured in the 
axial direction) at the leading edge 54 is illustrated as being the same 
from the leading edges to the radially outer tips, those skilled in the 
art will appreciate that such blade height may be varied along the length 
of the blade as desired. This flexibility allows the designer to optimize 
the inlet flow angle for best suction performance without significantly 
affecting the overall head flow characteristic of the pump, particularly 
when good isolation is maintained between the impeller tips and the 
recirculation chambers as in the embodiment of FIGS. 3 and 4.