Patent Application
20150071774
The present disclosure relates to centrifugal pumps which include an impeller within a volute and in which fluid sucked into the volute by rotation of the impeller is sent out along the volute and the sent-out fluid is discharged to outside of the centrifugal pump.
Among the conventionally-known centrifugal pumps are ones in which a rotation shaft rotatably projects into a volute and an impeller is mounted on the projecting rotation shaft. Such centrifugal pumps are adjustable in performance by fluid being caused to flow into a flow passage defined by the volute, as disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 2012-72697 (hereinafter referred to as “the relevant patent literature”).
In the centrifugal pump disclosed in the relevant patent literature, the volute is disposed within a pump casing, and the impeller is rotatably accommodated within the volute. The volute has a surface opposed to respective one end surfaces in a rotation axis direction (i.e., respective one axial end surfaces) of vanes provided on the impeller, and a peripheral wall section extending from the outer peripheral edge of the volute's opposed surface to surround the outer periphery of the impeller. Fluid is sucked in through a suction opening formed centrally in the opposed surface, and the impeller is rotated so that, by centrifugal force, the fluid is discharged into the pump casing through a discharge opening formed in the peripheral wall section.
Although the flow passage is formed inside the volute, backward or reverse flows of the fluid are prevented by locating the axial end surfaces of the vanes and the volute's opposed surface close to each other. In order to increase a flow rate of the fluid and thereby enhance the performance of the centrifugal pump, there may be employed an approach of increasing the sectional area of the in-volute flow passage and/or increasing the diameter of the impeller. The sectional area of the in-volute flow passage can be increased by increasing a dimension of the volute in a radially outward direction so that the peripheral wall section is located more radially outward or locating the opposed surface of the volute higher in the axial direction.
If the peripheral wall section of the volute is located more radially outward and/or the opposed surface of the volute is located higher in the axial direction, however, the volute and the pump casing would interfere with each other. If the pump casing is increased in size to avoid such interference, the centrifugal pump would increase in overall size. Further, if the volute is increased in dimension in the axial direction of the rotation shaft rather than in the radially outer direction, the sectional area of the in-volute flow passage cannot be used effectively. Thus, some improvement has to be made in order to increase the flow rate while maintaining the size of the volute (i.e., without changing the size of the volute).
In view of the foregoing problems, it is preferable to provide an improved technique which permits an increased flow rate within a volute of a centrifugal pump and thereby permits enhanced self-priming of the pump while maintaining the overall size of the volute.
In order to accomplish the above, one aspect of the present disclosure provides an improved centrifugal pump which comprises: a volute provided within a pump casing; and an impeller rotatably provided within the volute, wherein fluid sucked into the volute by rotation of the impeller is sent out from the volute into the pump casing and then discharged to outside of the pump casing, and in which the impeller has a plurality of vanes provided thereon in a radial arrangement about a rotation shaft that rotates the impeller, the volute has a generally flat opposed surface that is opposed to respective axial end surfaces (i.e., end surfaces in the axial direction of the rotation shaft) of the plurality of vanes, the opposed surface having a proximate section that is proximate to the axial end surface of each of the vanes, the proximate section having an annular shape and being disposed about the rotation shaft. Further, the proximate section includes an outer peripheral portion having a tapered shape such that, within a range of a rotational trajectory of each of the vanes, the outer peripheral portion gradually spreads out in a direction axially away from the vane, i.e. with an increasing distance from the vane.
Moreover, the generally flat opposed surface of the volute is opposed to the respective axial end surfaces of the plurality of vanes, the proximate section of the opposed surface is proximate to the axial end surface of each of the vanes, and the proximate section having an annular shape is disposed about the rotation shaft. Further, the proximate section includes the outer peripheral portion has a tapered shape such that, within the range of the rotational trajectory of each of the vanes, the outer peripheral portion gradually spreads out in a direction axially away from the vane. With such arrangements, the present disclosure can provide an increased flow-passage sectional area of the outer peripheral portion. Further, with the outer peripheral portion having such a tapered shape, the flow passage can be changed in direction smoothly, not at a steep angle. As a result, the present disclosure permits efficient use of a space inside the volute and an increased flow rate within the volute while maintaining the overall size of the volute (i.e., without changing the overall size of the volute). Further, priming water can be fed through a discharge opening of the outer peripheral portion with an increased ease, so that gas-liquid agitation can be promoted to achieve enhanced self-priming.
In an embodiment of the present invention, the proximate section includes an inner peripheral portion having a tapered shape such that, within the range of the rotational trajectory of each of the vanes, the inner peripheral portion tapers in the direction axially away from the vane, and the inner peripheral portion and the outer peripheral portion are spaced apart from each other. Because the inner peripheral portion of the proximate section has a tapered shape such that, within the range of the rotational trajectory of each of the vanes, it gradually tapers in the direction axially away from the vane, the inner peripheral portion can provide an increased flow-passage sectional area. Further, with the inner peripheral portion having such a tapered shape, the flow passage can be changed in direction smoothly, not at a steep angle. As a result, the embodiment permits efficient use of the space inside the volute and an increased flow rate within the volute to thereby realize even further enhanced self-priming. Further, because the inner peripheral portion and the outer peripheral portion are spaced apart from each other, the proximate section disposed within the range of the rotational trajectory of each of the vanes can reliably prevent the fluid from flowing backward. As a result, the embodiment can prevent variation in discharge pump head.
Further, of the proximate section, the outer peripheral portion having the tapered shape has a plurality of fins provided thereon in a radial arrangement about the rotation shaft and projecting toward the impeller. Because the fins are provided in a radial arrangement about the rotation shaft, the fluid can be straightened by the fins, so that flows of the fluid can be smoothed. As a result, the present disclosure can lower resistance of the flow passage and reduce a load on a drive source that rotates the impeller.
The following will describe embodiments of the present invention, but it should be appreciated that the present invention is not limited to the described embodiments and various modifications of the invention are possible without departing from the basic principles. The scope of the present invention is therefore to be determined solely by the appended claims.
Certain preferred embodiments of the present invention will hereinafter be described in detail, by way of example only, with reference to the accompanying drawings, in which:
Now, a description will be given about a first embodiment of a centrifugal pump 20 of the present invention. As shown in
The engine 14 includes a cylinder block 15 mounted on the base 12, a pump casing 22 of the centrifugal pump 20 is mounted on the cylinder block 15, and a crankshaft 16 has an end portion 16a projecting from the cylinder block 15 into the pump casing 22.
Of the crankshaft 16, a portion 16b located near the end portion 16a (i.e., near-end portion 16b) is rotatably supported on a mechanical seal 17, and the end portion 16a is connected to an impeller 31 of the centrifugal pump 20. Thus, the impeller 31 is rotatable by the crankshaft 16 (hereinafter also referred to as “rotation shaft 16”) being rotated by activation of the engine 14.
The centrifugal pump 20 includes the pump casing 22 bolted to the cylinder block 15 via a partition member 21, the impeller 31 provided within the pump casing 22 and connected to the end portion 16a of the rotation shaft 16, and a volute 40 covering the impeller 31.
Further, the centrifugal pump 20 has a suction nozzle 35 communicating with a suction opening 25 of the pump casing 22 (i.e., casing suction opening 25), an opening/closing section 36 having an upper end portion 36a sandwiched between the pump casing 22 and the suction nozzle 35, and a discharge nozzle 37 communicating with a discharge opening 28 of the pump casing 22 (i.e., casing discharge opening 28).
The pump casing 22 has a casing opening section 23 closed with the partition member 21, and the volute 40 is provided on the partition member 21. Thus, an in-casing flow passage 38 is defined with the pump casing 22, the partition member 21 and the volute 40. Particularly, the in-casing flow passage 38 is defined in a substantially annular shape between the pump casing 22 and the volute 40.
As shown in
The suction-side wall section 24 includes a projection 51 projecting downward from a lower portion 24b of the wall section 24, i.e. a lower part 26a of the suction passage portion 26. The projection 51 projects (bulges) laterally from the lower portion 24b of the suction-side wall section 24 toward the in-casing flow passage 38. By the projection 51 formed integrally with the lower portion 24b of the suction-side wall section 24, the pump casing 22, and hence the centrifugal pump 20, can be reduced in weight and size as compared to a case where the projection 51 is formed as a separate member from the lower portion 24b of the suction-side wall section 24.
As shown in
As shown in
The upstream top portion 52a is disposed in a range H downstream of the casing discharge opening 28 and upstream of the opening 48 of the volute 40. Preferably, the upstream top portion 52a is provided on the lower part 26a of the suction passage portion 26 in the range H.
Further, the wall section 53 extends downward from an edge portion of the top section 52 and has an upper edge portion formed straight along the top section 52 and a lower edge portion curved along a lower portion of the peripheral wall section 27; thus, the wall section 53 generally has a half-moon shape. The wall section 53 also has a drain hole 55 that is closed with a drain plug 54 screwed thereto.
Further, with the projection 51 provided on the lower part 24b of the suction-side wall section 24, a flow-passage narrowing portion 39 is formed in a lower portion of the in-casing flow passage 38, and the flow-passage narrowing portion 39 has a smaller sectional area than the remaining portions of the in-casing flow passage 38. Further, the flow-passage narrowing portion 39 is located beneath the rotation axis 34 of the impeller 31, more specifically beneath a suction opening 41 of the volute 40 (i.e., volute suction opening 41), and at generally the same height as the opening 48 of the volute 40. In this manner, the opening 48 of the volute 40 is in communication with the flow-passage narrowing portion 39.
Further, the casing suction opening 25 is provided in the suction-side wall section 24, and the suction passage portion 26 is in communication with the casing suction opening 25. The suction passage portion 26 is in communication with the volute suction opening 41. Further, the volute suction opening 41 is in communication with the suction nozzle 35 by way of the suction passage portion 26 and the casing suction opening 25.
Further, the pump casing discharge opening 28 is provided in an upper portion 27c of the peripheral wall section 27, and the discharge nozzle 37 is in communication with the pump casing discharge opening 28. A fluid feed opening 61 is provided in an upper end portion of the discharge nozzle 37 and located over the volute 40, and this fluid feed opening 61 is closed with a feed plug 62.
Further, the partition member 21 has a support hole 21a formed therein concentrically with the rotation shaft 16, and the mechanical seal 17 is concentrically supported in the support hole 21a, and the rotation shaft 16 (more specifically, the near-end portion 16b) is rotatably supported on the mechanical seal 17. Further, the end portion 16a of the rotation shaft 16 projects through the mechanical seal 17 into the volute 40. Thus, the mechanical seal 17 can mechanically prevent fluid present within the volute 40 from leaking outside via the near-end portion 16b.
The impeller 31 is mounted on the rotation shaft's end portion 16a projecting into the volute 40, so that the impeller 31 is disposed inside the volute 40. The impeller 31 includes a disk-shaped hub 32 mounted on the end portion 16a, and a plurality of vanes 33 provided on the hub 32 in a radial arrangement about the rotation shaft 16. The plurality of vanes 33 are provided on a surface portion 32a of the hub 32 opposite from the mechanical seal 17. The impeller 31 is accommodated inside the volute 40 by being covered with the volute 40.
The volute 40 is fixed to the partition member 21 by means of bolts 66. The volute 40 is a case member provided within the pump casing 22 and accommodating therein the impeller 31. An in-volute flow passage 68 is defined with the volute 40 and the partition member 21. The volute 40 includes the suction opening 41 provided in communication with the suction passage portion 26 of the pump casing 22, and a volute body 42 has a spiral shape and disposed around the suction opening 41 (impeller 31).
The volute body 42 has a generally flat opposed surface 43 that is opposed to respective end surfaces 33a, in a rotation axis direction, of the vanes 33 (i.e., respective axial end surfaces 33a of the vanes 33). The volute body 42 has the opening 48 formed in a lower end portion 42a thereof, and a volute discharge opening 49 formed in a left upper portion 42b thereof. The opening 48 is provided for directing priming fluid, present in the in-casing flow passage 38, into the volute 40 (i.e., into the in-volute flow passage 68).
During self-priming of the centrifugal pump 20, the priming fluid is fed through the fluid feed opening 61 into the in-volute flow passage 68 with the feed plug 62 removed. The priming fluid thus fed into the in-casing flow passage 38 is discharged through the volute discharge opening 39 together with gases present in the in-volute flow passage 68 and then directed into the in-casing flow passage 38. Note that the “priming fluid” is fluid that performs a pump-priming action during the self-priming operation of the centrifugal pump 20.
More specifically, during the self-priming, priming fluid fed to the in-casing flow passage 38 is sucked into the in-volute flow passage 68 through the volute opening 48 by the impeller 31 being rotated as indicated by arrow A. Gases present in the in-volute flow passage 68 are incorporated as air bubbles into the fluid sucked into the in-volute flow passage 68. The fluid containing such air bubbles is discharged through the volute discharge opening 49 as indicated by arrow B and directed to an upper portion 38a of the in-casing flow passage 38, so that the gases present as the air bubbles are separated from the priming fluid and discharged to outside of the centrifugal pump 20 through the casing discharge opening 28 and the discharge nozzle 37. Further, the fluid having the gases separated therefrom as above flows as indicated by arrow C.
During steady operation of the pump 20, on the other hand, fluid directed through the volute suction opening 41 into the in-volute flow passage 68 is discharged through the volute discharge opening 39 and directed into the in-casing flow passage 38. The opening/closing section 36 has the upper end portion sandwiched between the pump casing 22 and the suction nozzle 35, as noted above. The suction nozzle 35 opens or closes in response to the opening/closing section 36 pivoting in an arrowed direction of
More specifically, during the steady operation of the pump 20, fluid is sucked through the volute suction opening 41 into the in-volute flow passage 68 by the impeller 31 being rotated in the direction of arrow A in
Further, as shown in
The proximate section 44 includes an outer peripheral portion 45 of an annular shape, a proximal opposed surface portion 43a of an annular shape disposed inward of the outer peripheral portion 45, and an inner peripheral portion 46 of an annular shape disposed inward of the opposed surface portion 43a. Thus, the proximate section 44 is constructed as a triple-ring structure as viewed in rear view.
The outer peripheral portion 45 of the proximate section 44 is formed in a tapered shape such that, within a range S1 of a rotational trajectory of each of the vanes 33, it gradually spreads out (or slants radially outward) in a direction axially away from each of the vanes 33, i.e. with an increasing distance from each of the vanes 33. Further, the inner peripheral portion 46 of the proximate section 44 is formed in a tapered shape such that, within the range S1 of the rotational trajectory of each of the vanes 33, it gradually tapers (i.e., slants radially inward) in the direction axially away from each of the vanes 33.
Further, the inner peripheral portion 46 and the outer peripheral portion 45 are spaced apart from each other with the opposed surface portion 43a disposed therebetween. The opposed surface portion 43a proximate to the tapered outer peripheral portion 45, the tapered inner peripheral portion 46 and the axial end surfaces 33a overlaps about one third of the range S1 of the rotational trajectory of each of the vanes 33.
Namely, the volute body 42 includes: the tapered inner peripheral portion 46 provided immediately adjacent to the volute suction opening 41; the opposed surface portion 43a formed continuously with the inner peripheral portion 46; the tapered outer peripheral portion 45 formed continuously with the opposed surface portion 43a; a spaced opposed surface 47a formed continuously with the outer peripheral portion 45 and spaced apart from the axial end surfaces 33a; and a peripheral wall 47b formed continuously with the spaced opposed surface 47a and surrounding the peripheral surfaces 33b of the vanes 33.
Next, a description will be given about behavior of the first embodiment of the centrifugal pump 20 constructed in the aforementioned manner.
During steady operation of the centrifugal pump 100, fluid flows through the volute suction opening 102 into an in-volute flow passage 107 as indicated by arrow D. Because the opposed surface 103 is located proximate to respective end surfaces 112, in a rotation axis direction, of individual vanes 111 (i.e., respective axial end surfaces 112 of the vanes 111) of the impeller 110, the fluid can be prevented from flowing back from the in-volute flow passage 107 to the volute suction opening 102. Although it is preferable that a flow passage from the volute suction opening 102 to the in-volute flow passage 107 be great in size, the overall size of the volute 101 has to be limited in order to avoid interference between the volute 101 and a pump casing surrounding the volute 101. In the conventionally-known example of the centrifugal pump 100, the flow rate of fluid cannot be increased because the flow passage has a small effective sectional area and has a bent shape.
Further, during the self-priming operation of the centrifugal pump 20, the outer peripheral portion 45 of the tapered shape allows priming water to flow as indicated by arrow F so that feeding of the priming water and gas-liquid agitation can be significantly promoted. Consequently, an increased self-priming speed can be achieved. Further, because the opposed surface portion 43a proximate to the axial end surfaces 33a of the impeller 31 overlaps about one third of the range S1 shown in
The following summarize the first embodiment of the centrifugal pump 10. As shown in
Further, because the inner peripheral portion 46 of the proximate section 44 has a tapered shape such that, within the range S1 of the rotational trajectory of each of the vanes 33, it gradually tapers in the direction axially away from the vane 33 as shown in
Next, a description will be given about a second embodiment of the centrifugal pump of the present invention with reference to
As shown in
As shown in (a) of
As shown in (b) of
Further, as shown in (c) of
Furthermore, the maximum pump head can be enhanced by increasing the density of the fins 56, and self-pumping performance can be enhanced by decreasing the density of the fins 56. Thus, the centrifugal pump 20 can be adjusted with ease in accordance with a desired purpose.
The following summarize the second embodiment of the centrifugal pump 20. As shown in
Whereas the outer peripheral portion 45 has been described above as having a straight sectional shape and formed in a tapered shape such that it gradually spreads out in the direction axially away from each of the vanes 33, the present invention is not so limited, and the outer peripheral portion 45 may have a curved sectional shape. Further, the inner peripheral portion 46 has been described above as having a straight sectional shape and formed in a tapered shape such that it gradually tapers in the direction axially away from each of the vanes 33, the present invention is not so limited, and the inner peripheral portion 46 may have a curved sectional shape.
The basic principles of the present disclosure are well suited for application to centrifugal pumps which include an impeller within a volute and in which fluid sucked into the volute by rotation of the impeller is sent out along the volute and the sent-out fluid is discharged to outside of the centrifugal pump.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-185083 | Sep 2013 | JP | national |
