JP2010014077A - Reverse flow prevention device in centrifugal pump suction pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit reverse flow in a suction pipe occurring in small flow rate in a centrifugal pump provided with an inducer. <P>SOLUTION: An orifice ring 34 is disposed at an upstream side of the inducer 22 in the suction pipe A straightening ring 36 is disposed between the orifice ring 34 and an inducer blades 26, keeping interval from the orifice ring 34. The straightening ring 36 includes a straightening hole 38 providing communication between the orifice side and the inducer side of the ring. Since turning component of flow reversely flowing from the inducer is reduced by the straightening hole 38, reverse flow is inhibited from getting over the orifice ring 34 and reaching the upstream thereof. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a centrifugal pump provided with an inducer, and more particularly to prevention of backflow generated in a suction pipe.

  In a centrifugal pump, a technique is known in which an axial flow impeller called an inducer is arranged upstream of an impeller in order to improve suction performance. When a centrifugal pump provided with this inducer is operated at a small flow rate, backflow may occur in the outer periphery of the inducer. This backflow causes pulsation in the suction pipe. Further, in the case of a centrifugal pump that handles liquid, the liquid whose temperature has increased in and around the impeller is sent to the upstream side of the inducer by backflow, thereby promoting the occurrence of cavitation. In addition, when the handling liquid is easily vaporized, it may vaporize in the suction pipe and the pump cannot be operated.

  In order to prevent this backflow, a technique is known in which an orifice is provided in a suction pipe upstream from an inducer (see Patent Document 1 below).

JP 51-81001 A

  The conventional orifice provided in the suction pipe may not be able to sufficiently prevent backflow.

  An object of the present invention is to effectively suppress a backflow generated in a suction pipe in a centrifugal pump provided with an inducer.

  The present invention includes an orifice ring disposed in the suction pipe and forming an orifice, and a rectifying means disposed between the orifice and the blade of the inducer and spaced from the orifice. This rectifying means reduces the swirl component of the reverse flow passing through the rectifying means, and the flow passing through the rectifying means hits the orifice ring. The rectifying means is an annular member extending along the inner wall surface of the suction pipe, has a component in the axial direction of the suction pipe, and extends through the inducer side and the orifice side of the rectifying means. It may have. The rectifying channel can be a hole or a groove.

  By reducing the swirl component of the backflow by the rectifying means, it is possible to suppress the backflow from occurring further upstream in the suction pipe beyond the orifice.

  The inner diameter of the ring member of the rectifying means is preferably equal to or larger than the inner diameter of the orifice ring. This is to prevent the minimum diameter of the suction pipe from being narrowed as compared with the case where the orifice is provided alone.

  The ring member of the rectifying means may have an annular wall member that protrudes toward the inducer at the end on the inner peripheral side. The backflow can be efficiently guided to the rectifying flow path by the wall member.

  Further, a plurality of ring members of the rectifying means can be arranged at intervals in the axial direction of the suction pipe. In addition, individual ring members may have different shapes.

  The rectifying means may include a plate-like rectifying plate arranged in the circumferential direction on the inner wall of the suction pipe, and each rectifying plate may be arranged to extend so as to have a directional component in the axial direction of the suction pipe. .

  The orifice ring may have an annular wall projecting toward the inducer side at an inner peripheral end thereof.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a centrifugal pump 10 according to the present embodiment. The impeller 14 housed in the casing 12 is coupled to the tip of a pump shaft 16 driven by a motor or the like. Connected to the casing 12 is an introduction pipe 20 that guides the handling liquid to the suction port 18 of the impeller 14. The introduction pipe 20 is arranged coaxially with the axis of the pump shaft 16, and an inducer 22 is arranged in the introduction pipe 20. The inducer 22 includes an inducer shaft 24 that extends from the pump shaft 16 and extends into the introduction pipe 20 and rotates together with the pump shaft 16, and an inducer blade 26 that is fixed to the inducer shaft 24. A suction pipe 28 that forms a suction pipe together with the introduction pipe 20 is connected to the introduction pipe 20. Further, a discharge pipe 30 for discharging the handling liquid sent out by the impeller 14 is connected to a position on the outer side in the radial direction of the impeller 14 in the casing 12.

  A backflow prevention device 32 is disposed upstream of the flow of the handling liquid, that is, in front of the introducer 22, particularly the inducer blade 26, of the introduction pipe 20. The backflow prevention device 32 includes an orifice ring 34 that forms an orifice, and a rectifying ring 36 that is disposed between the orifice ring 34 and the inducer blade 26 and spaced from the orifice ring 34. The orifice ring 34 and the rectifying ring 36 are annular members that are arranged concentrically with the introduction pipe 20 and extend along the inner wall surface of the introduction pipe 20. Further, these rings 34 and 36 can also be regarded as annular portions provided so as to project inward from the inner wall surface of the introduction pipe 20. FIG. 2 shows the rectifying ring 36 as viewed from the axial direction of the pump. The rectifying ring 36 has a plurality of rectifying holes 38 connecting the inducer side and the orifice side. The individual rectifying holes 38 have an axis parallel to the axis of the introduction pipe 20 and are arranged in the circumferential direction.

  FIG. 3 and FIG. 4 are views showing a state of the flow in the suction pipe when the flow rate is small, by a cross section including the axis of the suction pipe. FIG. 3 shows the flow when only the conventional orifice is provided, and FIG. 4 shows the flow when the backflow prevention device 32 of this embodiment is provided. 3, the same components as those of the pump of FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The orifice ring 40 forming the orifice is disposed in front of the inducer blade 26. When the flow rate is small, a backflow region is formed near the inner wall of the suction pipe. In order to prevent the backflow region from extending upstream of the suction pipe, a technique for arranging the orifice ring 40 is conventionally known, which has a certain effect. However, under a condition where the flow rate is lower, the counterflow region 42 extends upstream from the orifice ring 40 so as to get over the orifice ring 40 as shown in FIG. In the backflow region 42, the flow of the handling liquid has a swirling component, and therefore, it is considered that it has passed over the orifice ring 40. When the backflow region 42 becomes large, the flow in the pipe may become unstable and pulsation may occur. In addition, when handling a liquid that is easily vaporized, the liquid whose temperature has risen flows backward, so that this raises the temperature of the newly sucked liquid and easily causes cavitation. Further, when vaporization occurs in the suction pipe, the operation cannot be performed.

  In the backflow prevention device 32 of this embodiment, as shown in FIG. 4, the backflow prevention region 44 does not extend beyond the orifice ring 34 and upstream of the suction pipe. The swirl component of the reverse flow is reduced by the rectifying ring 36, and further, when the rectifying ring 36 strikes the orifice ring 34 and turns inward and mixes with the new liquid there, it is again sucked into the inducer side.

  FIG. 5 is a diagram comparing the temperature rise in the suction portion of the configuration including only the orifice of FIG. 3 and the configuration combining the orifice and the rectifying ring of FIG. It shows how much the temperature of the liquid immediately before the inducer increases with the flow rate, based on the temperature of the sufficiently upstream liquid. In the case of only the orifice, when the flow rate is 20 L / min or less, the temperature starts to rise, and when the flow rate is further reduced, the temperature rises rapidly. When the orifice and the rectifying ring are combined, a temperature rise is hardly seen even at 10 L / min, and the rise starts at 5 L / min or less.

  FIG. 6 is a diagram showing a main part of another embodiment according to the present invention. The configuration of the centrifugal pump according to this embodiment is common to the configuration of the centrifugal pump 10 shown in FIG. 1, and the common portions are denoted by the same reference numerals and the description thereof is omitted. The backflow prevention device 52 is a combination of an orifice and a rectifying ring, like the backflow prevention device 32 described above. A rectifying ring 56 is arranged between the orifice ring 54 and the inducer blade 26 so as to be spaced from the orifice ring 54. The rectifying ring 56 is provided with a rectifying hole 58 that communicates the inducer side and the orifice side. On the inner peripheral surfaces of the orifice ring 54 and the rectifying ring 56, irregularities are provided in the axial direction of the suction pipe to form labyrinths 60 and 62. The labyrinths 60 and 62 provide resistance to the backflow that attempts to get over the orifice ring 54 and the backflow that tries to get over the inner peripheral surface of the rectifying ring 56, thereby obtaining a backflow prevention effect.

  FIG. 7 is a diagram showing a main part of another embodiment according to the present invention. The configuration of the centrifugal pump according to this embodiment is common to the configuration of the centrifugal pump 10 shown in FIG. 1, and the common portions are denoted by the same reference numerals and the description thereof is omitted. Similar to the backflow prevention device 32, the backflow prevention device 72 is a combination of an orifice and a rectifying ring. A rectifying ring 76 is disposed between the orifice ring 74 and the inducer blade 26 so as to be spaced from the orifice ring 74. The rectifying ring 76 is provided with a rectifying hole 78 that communicates the inducer side and the orifice side. The orifice ring 74 has an annular wall 80 that protrudes toward the inducer side at the inner tip. The annular wall 80 is formed around the inner circumference of the orifice ring 74 and passes through the rectifying hole 78, and the flow directed inward by the orifice ring 74 is further directed toward the inducer. At least reduce the momentum of the flow. In FIG. 7, the inner diameter of the orifice ring 74 is smaller than the inner diameter of the rectifying ring 76, but can also be made equal.

  8 and 9 are diagrams showing a main part of another embodiment according to the present invention. The configuration of the centrifugal pump according to this embodiment is common to the configuration of the centrifugal pump 10 shown in FIG. The backflow prevention device 82 has an orifice ring 84 and a rectifying ring 86 having the same shape as the orifice ring 34 and the rectifying ring 36 described above. The backflow prevention device 82 further includes a swirl prevention plate 90 provided in the flow path inside the orifice ring 84 or the rectifying ring 86. The anti-rotation plate 90 has a plate shape, and is arranged such that the normal of the surface of the plate faces in a direction orthogonal to the axis of the introduction tube 20. In the figure, the two anti-rotation plates 90 are arranged so as to be substantially orthogonal to each other, but the number is not limited to this. The swirl prevention plate 90 also reduces the swirl component of the backflow and suppresses the development of the backflow region.

  FIG. 10 is a diagram showing a main part of another embodiment according to the present invention. The configuration of the centrifugal pump according to this embodiment is common to the configuration of the centrifugal pump 10 shown in FIG. 1, and the common portions are denoted by the same reference numerals and the description thereof is omitted. The backflow prevention device 92 has an orifice ring 94 having the same shape as the orifice ring 34 described above. A rectifying ring 96 is disposed between the orifice ring 94 and the inducer blade 26 with a space from the orifice ring 94. The rectifying ring 96 is provided with a rectifying hole 98 that communicates the inducer side and the orifice side. The rectifying ring 96 has an annular wall 100 projecting toward the inducer side at the inner tip. The annular wall 100 is formed around the inner circumference of the rectifying ring 96, and prevents the reverse flow from hitting the rectifying ring 96 and turning inward, while being guided to flow into the rectifying hole 98. To do.

  FIG. 11 is a diagram showing a main part of another embodiment according to the present invention. The configuration of the centrifugal pump according to this embodiment is common to the configuration of the centrifugal pump 10 shown in FIG. 1, and the common portions are denoted by the same reference numerals and the description thereof is omitted. The backflow prevention device 102 has an orifice ring 104 having the same shape as the orifice ring 34 described above. A rectifying ring 106 is disposed between the orifice ring 104 and the inducer blade 26 with a space from the orifice ring 104. The rectifying ring 106 is provided with a rectifying hole 108 that communicates the inducer side and the orifice side. The rectifying ring 106 has an annular wall 110 that protrudes toward the inducer at the inner tip. The annular wall 110 is formed around the inner periphery of the rectifying ring 106, and prevents the reverse flow from hitting the rectifying ring 106 and turning inward, while being guided to flow into the rectifying hole 108. To do. Further, a radial wall 112 extending in the radial direction is provided on a surface of the rectifying ring 106 facing the inducer. The radial walls 112 can be alternately arranged with the rectifying holes 108 in the circumferential direction. The radial direction wall 112 becomes resistance with respect to the swirling component of a backflow, and has an effect which suppresses this.

  FIG. 12 is a diagram showing a main part of another embodiment according to the present invention. The configuration of the centrifugal pump according to this embodiment is common to the configuration of the centrifugal pump 10 shown in FIG. 1, and the common portions are denoted by the same reference numerals and the description thereof is omitted. The backflow prevention device 122 has an orifice ring 124 having the same shape as the orifice ring 34 described above. Between the orifice ring 124 and the inducer blade 26, a plurality of rectifying rings 126a, 126b, 126c are arranged at a distance from the orifice ring 124. Each of the rectifying rings 126a, 126b, and 126c is provided with a rectifying hole similar to the rectifying hole 38 that communicates between the inducer side and the orifice side. In addition, the rectifying rings 126a, 126b, 126c are arranged at a distance from each other, and the inner diameter dimension is gradually reduced from the inducer side.

  FIG. 13 is a diagram showing a main part of another embodiment according to the present invention. The configuration of the centrifugal pump according to this embodiment is common to the configuration of the centrifugal pump 10 shown in FIG. 1, and the common portions are denoted by the same reference numerals and the description thereof is omitted. The backflow prevention device 132 has an orifice ring 134 having the same shape as the orifice ring 34 described above. Between the orifice ring 134 and the inducer blade 26, a plurality of rectifying rings 136 a, 136 b, 136 c are arranged at a distance from the orifice ring 134. Each of the rectifying rings 136a, 136b, and 136c is provided with a rectifying hole similar to the rectifying hole 38 that communicates between the inducer side and the orifice side. Further, the rectifying rings 136a, 136b, 136c are arranged with a space therebetween, and the inner diameter dimensions are common.

  FIG. 14 and FIG. 15 are diagrams showing the main part of another embodiment according to the present invention. The configuration of the centrifugal pump according to this embodiment is common to the configuration of the centrifugal pump 10 shown in FIG. 1, and the common portions are denoted by the same reference numerals and the description thereof is omitted. The backflow prevention device 142 is a combination of an orifice ring 144 and a rectifying ring 146. The rectifying ring 146 is disposed between the inducer blade 26 and the orifice ring 144 at a distance from the orifice ring 144. The state of the rectifying ring 146 as viewed from the side of FIG. 14 is shown in FIG. As shown in the drawing, the rectifying ring 146 is provided with a plurality of annular base portions 148 and a plurality of protrusions 150 protruding inward from the base portion 148 in the circumferential direction. A groove 152 that is a portion between the protrusions serves as a flow path that connects the inducer side and the orifice side of the rectifying ring 146. The inner diameter of the rectifying ring 146, that is, the diameter of the circle formed by the tips of the plurality of protrusions 150 is equal to or larger than the inner diameter of the orifice ring 144. It is also possible to reduce the circumferential thickness of the protrusion 150 and configure a rectifying ring 156 as a plate-like rectifying plate 154 as shown in FIG.

  In each of the embodiments described above, the rectifying holes and grooves of the rectifying ring extend in the direction along the axis of the suction pipe, but may extend in an oblique direction. However, with respect to the swirl flow, the swirl flow is disposed so as to extend in the intersecting direction and is disposed in a direction to reduce the swirl flow. Further, the orifice 74 having the annular wall 80 at the inner peripheral end shown in FIG. 7 can be combined with a rectifying ring shown other than this figure.

It is a figure which shows schematic structure of the centrifugal pump which concerns on this embodiment. It is the figure which looked at the rectifying ring from the side in FIG. It is a figure which shows the backflow area | region at the time of providing only an orifice. It is a figure which shows the backflow area | region at the time of providing an orifice and a rectification | straightening ring. It is the figure which compared the temperature rise of the liquid just before an inducer. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment. It is a figure which shows the principal part structure of other embodiment.

Explanation of symbols

  10 Centrifugal pump, 14 impeller, 20 introduction pipe (suction pipe), 22 inducer, 26 inducer blade, 28 suction pipe (suction pipe), 34 orifice ring, 36 rectifying ring, 38 rectifying hole.

Claims (9)

A backflow prevention device in a suction pipe of a centrifugal pump provided with an inducer,
An orifice ring disposed in the suction pipe in front of the blades of the inducer and forming an orifice;
A rectifying means disposed between the inducer blade and the orifice, spaced from the orifice, reducing a swirling component of the reverse flow passing therethrough, and the passed flow impinges on the orifice ring;
A backflow prevention device in the suction pipe of the centrifugal pump. The backflow prevention device according to claim 1,
The rectifying means includes a ring member having an inner diameter dimension equal to or larger than the inner diameter of the orifice ring, has a directional component in the axial direction of the suction pipe, and extends to communicate the inducer side and the orifice side of the rectifying means. A ring member having
Backflow prevention device.   It is a backflow prevention apparatus of Claim 2, Comprising: The said rectification flow path is a backflow prevention apparatus containing the hole provided in the rectification | straightening means.   It is a backflow prevention apparatus of Claim 3, Comprising: The said ring member is a backflow prevention apparatus which has the cyclic | annular wall which protrudes in the inducer side in the inner peripheral side edge part.   5. The backflow prevention device according to claim 4, wherein a radial wall extending in a radial direction is provided on a surface of the ring member facing the inducer.   4. The backflow prevention device according to claim 2, wherein a plurality of the ring members are arranged at intervals in the suction pipe axial direction. 5. The backflow prevention device according to claim 1,
The rectifying means includes a plate-like rectifying plate arranged in the circumferential direction on the inner wall of the suction pipe, and the individual rectifying plates are arranged to extend so as to have a directional component in the axial direction of the suction pipe.
Backflow prevention device.   The backflow prevention device according to any one of claims 1 to 7, wherein the orifice ring has an annular wall protruding toward an inducer side at an inner peripheral end thereof.   The centrifugal pump which has a backflow prevention apparatus of any one of Claims 1-8.

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