JP2015175278A - Centrifugal pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain initial performance of a semi-open type impeller for a long time and extend the life in a centrifugal pump having the semi-open type impeller.SOLUTION: An impeller 10 includes multiple blades 11 which face a suction cover inner wall surface 7 of a casing 2. The multiple blades 11 respectively have protrusion parts 20 formed at the pressure surface 11f side facing in a rotation direction R of the blades. Each protrusion part 20 protrudes in the rotation direction R and is formed along a front surface side edge part 12.

Description

  The present invention relates to a centrifugal pump, and more particularly to a centrifugal pump impeller suitable for transferring a fluid containing fine particles or solid particles such as coarse sand and gravel.

  An important issue for a centrifugal pump that transports a fluid containing solid particles is to prevent or suppress performance degradation by minimizing wear on the impeller and casing inner surface that are in contact with the fluid. In addition, when the performance of the pump such as impellers and casings wears down due to long-term operation of the pump, the initial performance is not reached, but there is an adjustment mechanism that should restore a certain level of performance. It is also an important task to prolong the life of the plant.

This type of pump is commonly referred to as a slurry pump. In the slurry pump, the metal material for the impeller and casing, which are parts that are in direct contact with the liquid, is generally low-cost high-chromium cast iron, ni-hard cast iron, etc. in consideration of cost and wear resistance. Life is extended by using materials.
By the way, impellers used for this type of centrifugal pump include a closed type (for example, see Patent Document 1) and a semi-open type (for example, see Patent Document 2).

  As shown in FIG. 3, the closed-type impeller 210 includes a main plate 213 and a plurality of blades 211 provided on the surface of the main plate 213 facing the suction port side. It has a front side plate (also referred to as a “shroud”) 214. The front side plate 214 is formed integrally with the front edge portion of the blade 211, and the front side plate 214 rotates to face the suction cover inner wall surface 207 of the stationary (fixed) casing (see FIG. 4C). ).

On the other hand, as shown in FIG. 4, the semi-open impeller 110 includes a main plate 113 and a plurality of blades 111 provided on a surface facing the suction port side of the main plate 113. The front edge portion 112 of the plurality of blades 111 rotates opposite to the stationary (fixed) inner wall surface 107 of the suction cover (see FIG. 3C).
Here, when solid particles lump in the fluid to be transferred form a group and flow from the inlet to the outlet of the impeller blades, the closed impeller is separated from the adjacent blades by the difference in the presence or absence of the front side plate. In the flow channel between them, a group of solid particles in the fluid becomes wedge-shaped and the blockage of the flow channel frequently occurs.

  On the other hand, in the semi-open impeller, the flow path is hardly blocked as compared with the closed impeller. The reason why the flow path of the semi-open impeller is difficult to block is that the rotational force of the impeller blades releases the wedge action with respect to the stationary (fixed) inner wall surface of the suction cover because there is no front side plate. Therefore, whether or not a large lump of solid particles is mixed in the fluid is a decisive factor for selecting the impeller type. That is, a spiral pump having a semi-open impeller is suitable for transferring a fluid containing fine particles or solid particles such as rough sand and gravel.

JP 2011-32983 A JP-A-7-243398

However, semi-open type impellers promote the wear of the blades because relatively small solid particles in the fluid flow or bite through the gap formed by the suction cover inner wall surface and the impeller blade front surface. There is a problem that pump performance (flow rate, pressure, efficiency) gradually decreases due to wear.
As shown in FIG. 4 by the two-dot chain line, the blade wear spot is generated on the pressure surface side Pf particularly facing the rotation direction R, and the outlet side (the outer circumference side) having a high peripheral speed. ) Tend to increase in intensity as you head to. On the other hand, the closed type impeller having the front side plate has significantly less blade wear and lower performance degradation than the semi-open type impeller.

The main causes of the performance degradation of the semi-open impeller are as described above: (1) Wear near the outer peripheral portion of the blade on the pressure surface side, and (2) Wear on the inner wall surface of the suction cover and the impeller blade front surface. This is because a gap (hereinafter also referred to as “clearance”) formed by the inner wall surface and the impeller is widened. In other words, as the “clearance” increases, the flow F1 along the pressure surface of the blade 111, which is the intended flow, as shown in FIG. 5 shows an image of the fluid flow in the vicinity of the blade. The diverted flow F2 from the pressure surface side of 111 toward the adjacent flow path (non-pressure surface side) increases, and the flow rate of the fluid leaking into the adjacent flow path also increases. As a result, the performance degradation of the head and efficiency also increases.
Here, in a normal slurry pump, as a countermeasure for the above (2), a clearance adjusting mechanism for narrowing a “clearance” spread due to wear is generally provided.

  For example, in the case of a centrifugal pump having a closed impeller, the gap is narrowed at a part of the mouth ring (or wear ring) and the suction cover is moved to the drive source side to adjust the “clearance” (Patent Document) 1). In the case of a centrifugal pump having a semi-open impeller, the gaps between the suction cover inner wall surface and the main blade front surface, the casing side wall and the back blade surface, and the like are adjusted by interposing packings or the like (Patent Literature). 2). However, such a gap adjusting mechanism has a problem that it takes time to perform maintenance and management for adjusting the gap. In addition, it does not extend the life of the impeller by maintaining the performance of the impeller itself for a long time.

  Therefore, the present invention has been made paying attention to such problems, and as compared with a spiral pump having a conventional semi-open impeller, the expected performance of the impeller is maintained to extend the life. An object of the present invention is to provide a centrifugal pump having a semi-open type impeller capable of performing

  In order to achieve the above-mentioned object, the present inventors have conducted detailed investigations on the wear location of the blades of the semi-open impeller, and as shown in FIG. As shown by reference numeral 112m), the wear progresses at the pressure surface side outer peripheral portion 112m of the front edge portion 112 on the front surface of the blade 111, starting from a corner portion 112k formed by the surface in the thickness direction of the blade and the surface in the width direction. I got the knowledge to do.

  The cause of the wear of the pressure surface side outer peripheral portion 112m of the front surface of the blade is that solid particles in the fluid flow through the “clearance” formed by the suction cover inner wall surface 107 and the front surface 112 of the blade 111. This is because solid particles in the fluid collide with the vicinity of the corner 112k formed by the surface in the thickness direction and the surface in the width direction. In particular, it has been found that when the wear near the blade outer peripheral portion 112m on the pressure surface side Pf progresses, the expected performance of the impeller is significantly reduced.

  Then, as shown in the image of the state of fluid flow in the vicinity of the blade in FIG. 5, normally, the fluid flows along the shape of the pressure surface of the blade 111 as indicated by reference numeral F <b> 1. In the case of impeller blades, in addition to the flow F1 along the shape of the blade, the adjacent flow path (non-pressure) passes through the gap T (see FIG. 4C) between the blade front surface 112 and the suction cover inner wall surface 107. Therefore, when the spread of the gap T between the blade front surface 112 and the suction cover inner wall surface 107 is increased, the amount of the divided flow F2 is increased accordingly. Therefore, it was found that the wear from the corner portion 112k formed by the blade pressure side front surface and the blade width portion further proceeds. In addition, in FIG. 5, the image of a mode that abrasion increases as it goes to the outer periphery of the pressure surface side of a blade | wing is shown with the dashed-two dotted line.

  On the other hand, in the blades of the closed impeller, since the front surface of the blades is blocked by the front side plate, there is no branching toward the adjacent flow path through the gap between the front surface of the blades and the inner wall surface of the suction cover. This is the decisive reason for the closed-type impeller that reduces blade wear and does not cause performance degradation. The present invention has been completed as a result of intensive studies based on such knowledge.

  That is, in order to solve the above-described problem, a centrifugal pump according to one aspect of the present invention includes a casing and a semi-open impeller provided in the casing, and the casing is axially more front than the impeller. A suction port formed in a central portion of a suction cover provided on the side, and a discharge port provided on the radially outer side of the impeller, the impeller on a surface facing the suction port side of the main plate and the main plate A centrifugal pump having a plurality of blades provided, and a front edge portion of the plurality of blades rotating to face an inner wall surface of the suction cover, wherein the plurality of blades face a rotation direction of the blades. It has a protrusion formed on the pressure surface side, and the protrusion extends in the rotation direction and is formed along the front edge of the blade.

  According to the spiral pump according to one embodiment of the present invention, since the semi-open impeller is provided, the flow path is hardly blocked even when a fluid containing solid particles is transferred. And the several blade | wing of an impeller has the protrusion part formed in the pressure surface side which opposes the rotation direction of a blade | wing, and this protrusion part protrudes toward a rotation direction, and is on the front edge part of a blade | wing. Therefore, in the flow along the pressure surface of the blade, the flow rate toward the adjacent channel through the gap between the front surface of the blade and the inner surface of the suction cover wall can be reduced. Therefore, it is possible to suppress the progress of wear from the corner portion formed by the pressure side front surface of the blade and the blade width portion.

In addition, although the ridge part will eventually disappear due to wear, the pump can be adjusted by adjusting the clearance while the state in which the diverted flow to the adjacent flow path can be suppressed by the ridge part continues. A stable state of performance can be maintained, and the life due to wear of the impeller can be extended.
In other words, this impeller has a shape in which a part of the front side plate (shroud) of the closed type impeller is added to the edge of the blade front of the semi-open type impeller, and the advantages of the closed type and the semi-open type are obtained. It can be said that it is an impeller that has both.

Here, if the base end of the protrusion is continuous with the pressure surface of the blade by a smooth arc, it is suitable for extending the life due to wear without significantly adversely affecting the performance. is there.
The protrusion is made of a wear-resistant metal made of a member separate from the blade. If the base end of the protrusion is fitted and fixed to the pressure surface of the blade, the protrusion is resistant to the protrusion. It is suitable for improving the wearability, and only the parts of the ridges can be exchanged according to the wear of the ridges.

  As described above, according to the present invention, the performance of the impeller can be extended and the life of the impeller can be extended as compared with the conventional semi-open impeller.

It is explanatory drawing of one Embodiment of a centrifugal pump provided with the semi-open type impeller which concerns on 1 aspect of this invention, The figure has shown the cross section along an axis line. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the semi-open type impeller which concerns on 1 aspect of this invention, The same figure (a) is the front view, (b) shows a part in the cross section along an axis line in the side view in (a), (C) shows the ZZ sectional view in (a). It is a figure explaining an example of a closed type impeller, The figure (a) is the front view, (b) shows a part in the cross section along an axis in the side view in (a), (c) is ( The ZZ sectional view in a) is shown. It is a figure explaining an example of the conventional semi-open type impeller, Comprising: It is a figure explaining the knowledge leading to this invention, The figure (a) is the front view, (b) is the side view in (a) A part is shown by the cross section along an axis, (c) shows ZZ sectional drawing in (a). Further, in FIGS. 2A and 2B, the wear part is indicated by a two-dot chain line. It is a figure explaining the knowledge leading to the present invention based on an example of a conventional semi-open type impeller, and this figure is a front view of the semi-open type impeller.

Hereinafter, an embodiment of a centrifugal pump including a semi-open impeller according to an aspect of the present invention will be described with reference to the drawings as appropriate.
As shown in FIG. 1, the centrifugal pump 1 includes a casing 2 having a suction cover 6, a casing body 8, and a casing side wall portion 9 in order from the front side in the axial direction (left side in the figure). A housing (bearing box) 30 placed and fixed on the upper portion of the frame 50 is provided on the back side of the casing 2 (right side in the figure), and rotates freely by driving a motor (not shown) in the housing 30. The shaft 3 is supported. The housing 30 is fixed at a predetermined position on the frame 50 by two front and rear housing pressers 52, and the casing side wall portion 9 of the casing 2 is fixed to the front side surface of the frame 50. .

  A tip 3 s of the rotating shaft 3 protrudes from the center of the casing side wall portion 9 into the casing 2, and a semi-open impeller (impeller) 10 is cantilevered on the tip 3 s of the rotating shaft 3. On the back side in the axial direction of the impeller 10, a shaft sealing device 40 is disposed between the casing side wall portion 9 and the housing 30 so as to surround the rotary shaft 3. A suction port 4 is formed at the center of the suction cover 6 on the front side of the impeller 10 in the axial direction, and a discharge port 5 is provided above the casing body 8 in the radial direction of the impeller 10. The fluid F is sucked from the suction port 4 by the rotation of 10 and the fluid F is discharged from the discharge port 5.

  The impeller 10 uses a wear-resistant material or a corrosion-resistant material. As shown in FIG. 2, the impeller 10 has a disk-shaped main plate 13 and a surface facing the suction port 4 side of the main plate 13 (on the front side surface of the main plate 13). And it has the some blade | wing 11 provided in the surface near the suction inlet 4). The plurality of blades 11 rotate such that the front edge portion 12 faces the suction cover inner wall surface 7 (see FIG. 1). A back blade 15 for decompressing the shaft seal device 40 is provided on the back surface of the main plate 13. The gap between the back blade 15 and the casing side wall 9 can be adjusted by moving the housing 30 on the frame 50 to the drive source side using the adjustment bolt 60 and narrowing it.

  In this example, as shown to Fig.2 (a), the several blade | wing 11 is equally distributed at four places with respect to the surface of the front side of the main board 13, respectively. Each blade 11 is formed in a spiral shape from the center of the main plate 13 toward the circumferential direction, and is provided so that the distance in the facing direction from the adjacent blade 11 is increased. Between the adjacent blades 11 is a flow path of the fluid F to be transferred. In the present embodiment, the curved shape, width dimension, and thickness dimension of each blade 11 are basically the same, and the performance is the same.

  Here, the several blade | wing 11 has the protrusion part 20 formed in the pressure surface side Pf facing the rotation direction R of a blade | wing. The protruding portion 20 extends in the rotation direction R and is formed along the front edge portion 12 of the blade 11. The base end portion of the ridge portion 12 is continuous with the pressure surface 11f of the blade 11 by a smooth arc 21 as shown in FIG. In this example, the cross-sectional shape of the ridge portion 20 is a trapezoidal shape in which the width of the base end portion is the widest and the width becomes narrower toward the tip in the protruding direction. The length and thickness (projected height) of the protrusion 20 are set within a range that does not significantly adversely affect the performance and can extend the life due to wear. The ridge portion 20 may be formed integrally with the blade 11 or may be formed from a member separate from the blade 11. In the present embodiment, the protruding portion 20 and the blade 11 are integrally formed.

Next, the operation and effect of the centrifugal pump 1 will be described.
When the rotary shaft 3 is rotated by driving a motor (not shown), the centrifugal pump 1 sucks the fluid F from the suction port 4 by the action of the centrifugal force of the plurality of blades 11, and the radial pump along the circumferential direction of the blades 11. The liquid is pumped outward and discharged from the discharge port 5.
According to this centrifugal pump 1, since the impeller 10 is cantilevered on the front end side of the rotating shaft 3 in the casing 2, the structure is simple, the disassembly and assembly are easy, and the manufacturing cost can be reduced. . Further, since the wear-resistant material or the corrosion-resistant material is used for the impeller 10, it can be used over a wide range of fluids such as fluids containing fine particles, solid particles such as rough sand and gravel, and fluids of chemical liquids. . And since the impeller 10 is a semi-open type, even if it is a case where the fluid containing a solid particle is transferred, a flow path cannot be obstruct | occluded easily.

  According to the centrifugal pump 1, the plurality of blades 11 of the impeller 10 have the protrusions 20 formed on the pressure surface 11 f side (Pf) facing the rotation direction R of the blades 11. Since the strip portion 20 extends in the rotation direction R and is formed along the front edge portion 12 of the blade 11, the front surface of the blade 11 and the suction cover wall in the flow along the pressure surface 11 f of the blade 11. It is possible to reduce the amount of flow toward the adjacent flow path through the gap on the inner surface 7. That is, the impeller 10 has a shape in which a part of a front side plate (shroud) of a closed type impeller is added to an edge of a blade front surface of a semi-open type impeller, and has advantages of a closed type and a semi-open type. It can be said that it is an impeller having both.

  Therefore, it is possible to suppress the progress of wear from the corner portion formed by the pressure side front surface of the blade 11 and the blade width portion (see the corner portion indicated by reference numeral 112k in FIG. 4C). Therefore, it is possible to greatly reduce the time and effort for maintenance and management for adjusting the “clearance” described above. In addition, this ridge portion 20 will eventually disappear due to wear, but the clearance adjustment should be performed while the ridge portion 20 continues to be able to suppress the partial flow rate to the adjacent flow path. Thus, the stable state of the pump performance can be maintained, and the life due to wear of the impeller 10 can be extended.

As described above, according to the centrifugal pump 1, the expected performance of the impeller can be maintained for a long time and the life can be extended. The spiral pump according to the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the said embodiment, although the example which formed the protrusion part 20 integrally with the blade | wing 11 was demonstrated, it is not limited to this, You may form the protrusion part 20 from a member different from the blade | wing 11. FIG.

  For example, it is preferable that the protruding portion 20 is formed of a wear-resistant metal made of a member separate from the blade 11 and the base end portion is fitted into the pressure surface 11 f of the blade 11 and fixed. Such a configuration is suitable for improving the wear resistance of the ridge portion 20, and only the components of the ridge portion 20 can be exchanged according to the wear of the ridge portion 20.

DESCRIPTION OF SYMBOLS 1 Centrifugal pump 2 Casing 3 Rotating shaft 4 Suction port 5 Discharge port 6 Suction cover 7 Suction cover inner wall surface 8 Casing body 9 Casing side wall 10 Impeller (impeller)
11 Blade 12 Front edge of blade 13 Main plate 15 Back blade 20 Projection 21 Arc 30 Housing (bearing box)
40 Shaft seal device 50 Frame 52 Housing presser 60 Adjustment bolt F Fluid F1 Flow along the pressure surface of the blade F2 Flow of diversion toward the next flow path R Blade rotation direction Pf Blade pressure surface side Pr Blade pressure surface side Opposite side T Clearance between the front surface of the blade and the inner wall of the suction cover

Claims (3)

A casing, and a semi-open impeller provided in the casing, wherein the casing has a suction port formed in a central portion of a suction cover provided on the front side in the axial direction from the impeller, and a diameter of the impeller The impeller includes a main plate and a plurality of blades provided on a surface of the main plate facing the suction port side, and a front edge portion of the plurality of blades includes the suction port. A centrifugal pump that rotates against the inner wall surface of the cover,
The plurality of blades have protrusions formed on the pressure surface side facing the rotation direction of the blades, the protrusions projecting in the rotation direction and along the leading edge of the blades A centrifugal pump characterized by being formed.   2. The centrifugal pump according to claim 1, wherein a base end portion of the protruding portion is continuous with a smooth arc on the pressure surface of the blade.   The said protrusion part is formed with the abrasion-resistant metal which consists of a member different from a blade | wing, The base end part of itself is fitted and fixed to the pressure surface of the blade | wing, The Claim 1 characterized by the above-mentioned. The described centrifugal pump.

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