JP7086802B2 - Maintenance method, design method, and pumping equipment of pumping equipment - Google Patents

Description

The present invention relates to a maintenance method, a design method, and a pump device of a pump device provided with an impeller having a plurality of blades.

In various applications such as industrial use, agricultural use, and rainwater drainage, a mixed flow impeller that can be operated in a wide range other than the highest efficiency point and a pump device equipped with an axial flow impeller are used.

Patent Document 1 discloses a pump device including a mixed flow impeller having a plurality of blades and a rotating shaft of a vertical shaft connected to the mixed flow impeller.

In such a pump device, it is known that cavitation occurs around the blades in an operating environment in which the suction pressure is lowered due to a drop in the suction water level or the like. Cavitation is a phenomenon in which bubbles are generated in a liquid flow where the pressure becomes lower than the saturated vapor pressure of the liquid.

Bubbles generated by cavitation gradually become smaller and disappear as the pressure of the liquid rises, and when the bubbles disappear, the very high pressure generated on the bubble part impacts the surface of the blade, and as a result, the impact causes dents on the surface of the blade. Scratches occur. This is called cavitation erosion (hereinafter referred to as erosion).

Therefore, erosion does not occur at the position where cavitation occurs, but on the metal surface (that is, the surface of the blade) in the vicinity where the bubbles collapse. When erosion occurs, especially on the surface of the blade, there is a problem that the performance of the pump device is greatly deteriorated.

Japanese Unexamined Patent Publication No. 2010-12146

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a maintenance method for a pump device capable of preventing performance deterioration of an impeller where erosion has occurred.

The characteristic configuration of the maintenance method of the pump device according to the present invention for achieving the above-mentioned object is the maintenance method of the pump device provided with the impeller having a plurality of blades, and among the above-mentioned blades. In the confirmation step of confirming whether or not there is a sign of erosion or erosion on the trailing edge of at least one of the blades, and in the confirmation step, it is confirmed that a sign of erosion or erosion has occurred. When this is done, the point is that the negative pressure surface side of each trailing edge of each of the blades is scraped toward the leading edge of each of the blades, or the trailing edge of each of the blades is scraped so as to be rounded.

In the pump device, if both pump efficiency and improvement of suction performance are achieved and the overall compactness is achieved, the load per unit area of the blade surface of the impeller will be reduced. At this time, the blade is greatly twisted three-dimensionally, and the trailing edge has a sharpened shape in the cross-sectional view of the blade.

Due to the rotation of the impeller, the positive pressure surface side of the blade is basically high pressure, but a low pressure region is generated slightly upstream of the sharpened trailing edge. Cavitation occurs in this low pressure region, or cavitation generated on the upstream side increases, and the bubbles collapse in the high pressure region near the trailing edge, so that the trailing edge is eroded and the performance of the impeller deteriorates. ..

Therefore, the confirmation process is executed during the periodic inspection of the pump device, it is confirmed whether or not the trailing edge of the blade is eroded, and if it is confirmed that the erosion has occurred, the processing process is performed. Do it.

As a result of diligent research by the inventors, the pressure in the low pressure region on the positive pressure surface side of the trailing edge of the blade is increased by changing the shape of the negative pressure surface of the trailing edge of the blade by the machining process. It turned out that it could be done. As a result, the pressure difference between the pressure in the low pressure region on the positive pressure surface side of the trailing edge of the blade and the pressure in the high pressure region near the trailing edge of the blade becomes small. Therefore, cavitation itself is unlikely to occur, and even if bubbles are generated by cavitation, their collapse is unlikely to occur. As a result, new erosion is suppressed and the performance deterioration of the impeller is improved.

The processing step is not limited to the case where it is confirmed that the trailing edge of the blade is actually eroded in the confirmation step, and even if the trailing edge is not confirmed to be eroded, it is a sign. Is executed when is confirmed.

In addition, when the impeller is equipped with a plurality of blades, erosion is evenly distributed to all the blades due to the drift of suction and the slight difference in the mounting angle of each blade when the impeller is manufactured. It does not always occur. Therefore, if it is confirmed that at least one of the multiple blades has erosion on the trailing edge or signs of erosion, the trailing edge of the erosion or its signs. Even if the blades have not been confirmed to be generated, corrosion may occur over time. Therefore, the processing step is executed for all the blades including the blades. At this time, it is preferable that the balance of the impeller is adjusted at the same time.

In the maintenance method, the pressure in the space from each trailing edge to the rectifying vane provided on the downstream side of each trailing edge locally in the vicinity of the trailing edge of the blade (hereinafter referred to as “)”. It is effective in a pump device having a high pressure region where the pressure is about 20% or more (in many cases 50% or less) higher than the average of ambient pressure). At that time, it is more effective when the pump device has a low pressure region extremely lower than the ambient pressure, such as a negative pressure, on the positive pressure surface side of the trailing edge of the blade.
As long as the pump device has such a condition, the impeller may be a mixed flow impeller, an axial flow impeller, or a centrifugal impeller.

Further, the maintenance method is effective in a pump device in which the impeller is an impeller configured so that the blade angle of the blade can be changed. This is because erosion is likely to occur when there is a problem that the blade angle is not changed as designed. Even with a fixed-wing impeller designed to prevent erosion, erosion can occur because the discharge pressure changes due to fluctuations in the suction water level. Therefore, the maintenance method is also effective for a fixed-wing impeller.

Further, the maintenance method is performed in a pump device in which the blade of the impeller is a blade having a cross-sectional shape (that is, the thickness is not constant) of the blade having the maximum wall thickness in the middle of the blade length from the leading edge to the trailing edge. It is valid.

Furthermore, the maintenance method is particularly effective in a pump device having a specific speed _ns of about 500 or more, that is, a mixed flow impeller or an axial flow impeller.

In the present invention, in the confirmation step, even if cavitation is not confirmed on the trailing edge of any of the blades, the pump device is placed on the positive pressure surface of any of the blades. When it is confirmed that cavitation has occurred or has occurred during operation, the impeller has a fluid analysis step of performing fluid analysis, and as a result of the fluid analysis step, among the blades, It was confirmed that a low pressure region was generated on the positive pressure surface side of the trailing edge of at least one of the blades, and a local high pressure region was generated in the vicinity of the trailing edge. When the pressure difference between the two and the above exceeds a predetermined threshold value, it is preferable to determine that a sign of cavitation has occurred at the trailing edge.

Even if the trailing edge of the blade is not eroded, cavitation is directly confirmed on the positive pressure surface of any of the blades, for example, during the operation of the pump device, or the paint is scratched or peeled off. If traces of cavitation occurring during the operation of the pump device are confirmed, the fluid analysis step is executed. By the fluid analysis process, it was confirmed that a low pressure region was generated on the positive pressure surface side of the trailing edge and a local high pressure region was generated near the trailing edge, and the pressure difference between the pressure in the low pressure region and the pressure in the high pressure region was large. If the predetermined threshold is exceeded, erosion may occur over time even if the blades have not been confirmed to have erosion or signs of erosion at the trailing edge. Therefore, all the blades including the blades. The processing process is executed in advance. This makes it possible to suppress erosion at the trailing edge of the blade. The predetermined threshold value is a value individually determined according to the design of the pump device.

In the present invention, when the negative pressure surface side of the trailing edge is shaved toward the leading edge of each blade in the processing step, the direction from the inside to the outside of the rotation axis of the impeller is toward the leading edge. It is preferable to process so that the processing range is widened.

As a result of diligent research by the inventors, it was found that erosion is more likely to occur from the inside to the outside with respect to the axis of rotation of the impeller. According to the above configuration, it is possible to more effectively suppress erosion in a portion where erosion is likely to occur.

In the present invention, when the trailing edge is rounded in the machining step, it is preferable to process the trailing edge so that the trailing edge is closer to the leading edge than the inside to the rotation axis of the impeller. ..

As a result of diligent research by the inventors, it was found that erosion is more likely to occur from the inside to the outside with respect to the axis of rotation of the impeller. According to the above configuration, it is possible to more effectively suppress erosion in a portion where erosion is likely to occur.

The characteristic configuration of the design method of the pump device according to the present invention for achieving the above-mentioned object is the design method of the pump device provided with the impeller having a plurality of blades, and is formed in a predetermined shape. In the fluid analysis step of performing the fluid analysis on the impeller and the fluid analysis step, a low pressure region is generated on the positive pressure surface side of the trailing edge of at least one of the blades, and the rear It is confirmed that a local high pressure region is generated in the vicinity of the edge, and when the pressure difference between the pressure in the low pressure region and the pressure in the high pressure region exceeds a predetermined threshold value, each trailing edge of each blade. Approaches the leading edge and the positive pressure surface of each of the blades, thereby changing the shape of the negative pressure surface of each of the blades so that a convex shape is formed on the negative pressure surface of each of the blades, or each of the above. The point is that it has an adjustment step of changing the shape so that the trailing edge is rounded.

In the pump device, if both pump efficiency and improvement of suction performance are achieved and the overall compactness is achieved, the load per unit area of the blade surface of the impeller will be reduced. At this time, the blade is greatly twisted three-dimensionally, and the trailing edge has a sharpened shape in the cross-sectional view of the blade. The shape at this time is called a predetermined shape.

An impeller formed in such a predetermined shape tends to generate a low pressure region on the positive pressure surface side of the trailing edge, and when the bubbles generated by cavitation collapse in the high pressure region near the sharpened trailing edge, the trailing edge Is easily eroded. Therefore, if a fluid analysis step is executed during the manufacturing of the pump device and it is confirmed that a low pressure region is generated on the positive pressure surface side of the trailing edge of the blade and a local high pressure region is generated in the vicinity of the trailing edge. The adjustment process is carried out.

As a result of diligent research by the inventors, the pressure in the low pressure region on the positive pressure surface side of the trailing edge of the blade is increased by changing the shape of the negative pressure surface of the trailing edge of the blade by the adjustment process. It turned out that it could be done. As a result, the pressure difference between the pressure in the low pressure region on the positive pressure surface side of the trailing edge of the blade and the pressure in the high pressure region near the trailing edge of the blade becomes small. Therefore, cavitation itself is unlikely to occur, and even if bubbles are generated by cavitation, their collapse is unlikely to occur. As a result, erosion is suppressed and the performance deterioration of the impeller is improved.

In the present invention, the blades are arranged so that the trailing edge approaches the leading edge and the positive pressure surface of the blades in the adjustment step, whereby a convex shape is formed on the negative pressure surface of the blades . When changing the shape of the negative pressure surface, the range defined by the trailing edge and the convex shape of the negative pressure surface is changed so as to extend from the inside to the outside with respect to the rotation axis of the impeller. At the point.

As a result of diligent research by the inventors, it was found that erosion is more likely to occur from the inside to the outside with respect to the axis of rotation of the impeller. According to the above configuration, it is possible to more effectively suppress erosion in a portion where erosion is likely to occur.

In the present invention, when the shape is changed so that the trailing edge is rounded in the adjusting step, the trailing edge is changed so as to be closer to the leading edge than the inside with respect to the rotation axis of the impeller. Suitable.

As a result of diligent research by the inventors, it was found that erosion is more likely to occur from the inside to the outside with respect to the axis of rotation of the impeller. According to the above configuration, it is possible to more effectively suppress erosion in a portion where erosion is likely to occur.

A characteristic configuration of the pump device according to the present invention for achieving the above object is a pump provided with a mixed flow impeller having a plurality of blades and a rotating shaft of a vertical shaft connected to the mixed flow impeller. The blade is a device, and the cross section orthogonal to the fluid transport direction of the blade has a convex shape on a positive pressure surface, a concave shape on a negative pressure surface, and a convex shape on a negative pressure surface near the trailing edge of the blade. The convex shape of the negative pressure surface overlaps with the outer peripheral surface of the rotation range of the blade when the oblique flow impeller is rotated, and the rotation outer peripheral surface which is a surface continuous with the positive pressure surface is projected onto the negative pressure surface. It is located at a point located on the front edge side of the blade beyond the projection plane generated at the time of rotation .

Normally, in a pump device, if both pump efficiency and improvement of suction performance are achieved and the overall size is reduced, the design is such that the load per unit area of the blade surface of the impeller is reduced. At this time, the blade is greatly twisted three-dimensionally, and the trailing edge has a sharpened shape in the cross-sectional view of the blade.

An impeller having such a shape tends to generate a low pressure region on the positive pressure surface side of the trailing edge, and when bubbles generated by cavitation collapse in the high pressure region near the sharpened trailing edge, the trailing edge is likely to be eroded. ..

As a result of diligent research by the inventors, the cross section of the blade orthogonal to the fluid transport direction of the blade is convex on the positive pressure surface and concave on the negative pressure surface, and the negative pressure surface near the trailing edge of the blade. The convex shape of the negative pressure surface overlaps with the outer peripheral surface of the rotation range of the blade when the oblique flow impeller is rotated, and the rotation outer peripheral surface which is a surface continuous with the positive pressure surface is negative. When configured to be located on the front edge side of the blade beyond the projection surface generated when projected onto the pressure surface, the pressure in the low pressure region on the positive pressure surface side of the trailing edge of the blade has a convex shape on the negative pressure surface of the trailing edge. It turned out to be higher than the blades that did not.

In such a blade, the pressure difference between the pressure in the low pressure region on the positive pressure surface side of the trailing edge of the blade and the pressure in the high pressure region near the trailing edge of the blade becomes small. Therefore, cavitation itself is unlikely to occur, and even if bubbles are generated by cavitation, their collapse is unlikely to occur. As a result, erosion is suppressed and the performance deterioration of the impeller is improved.

In the present invention, the range defined by the convex shape of the trailing edge and the negative pressure surface has a shape that extends from the inside to the outside with respect to the rotation axis of the mixed flow impeller. ..

As a result of diligent research by the inventors, it was found that erosion is more likely to occur from the inside to the outside with respect to the axis of rotation of the impeller. According to the above configuration, it is possible to more effectively suppress erosion in a portion where erosion is likely to occur.

In the present invention, it is preferable that the trailing edge has a shape rounded so that the trailing edge approaches the leading edge of the blade toward the outside from the inside with respect to the rotation axis of the oblique impeller.

As a result of diligent research by the inventors, it was found that erosion is more likely to occur from the inside to the outside with respect to the axis of rotation of the impeller. According to the above configuration, it is possible to more effectively suppress erosion in a portion where erosion is likely to occur.

Schematic diagram of the pump device Front view of impeller Cross section of the blade Cross section of the blade Explanatory drawing of the pressure region around the blade based on the analysis Explanatory drawing of the pressure region around the blade based on the analysis

Hereinafter, the maintenance method, the design method, and the pump device according to the embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the pump device 10. The pump device 10 includes a rotary shaft 12 of a vertical shaft rotatably arranged in the casing 11, a mixed flow impeller 13 provided at the lower end of the rotary shaft 12 and rotating integrally with the rotary shaft 12, and an upper side of the casing 11. A pumping pipe 14 connected to the above, a discharge curved pipe 15 connected to the upper side of the pumping pipe 14, and a suction casing 16 connected to the lower side of the casing 11 are provided. The discharge pipe 17 is continuously provided on the downstream side of the discharge curved pipe 15.

The casing 11 is provided with a rectifying blade 18 on the downstream side of the mixed flow impeller 13. The rectifying blade 18 is provided to rectify the fluid discharged from the mixed flow impeller 13 in the axial direction and smoothly guide the fluid to the pumping pipe 14.

A motor 30 is provided on the upper portion of the discharge curved pipe 15, and the rotary shaft 12 and the output shaft 31 of the motor 30 are connected via a coupling 29.

As shown in FIG. 2, the mixed flow impeller 13 includes a boss portion 32 fixedly supported by the rotating shaft 12 and four blades 33 fixedly arranged around the boss portion 32. .. The number of blades 33 is an example. The boss portion 32 and the blade 33 are made of a material having strength and corrosion resistance against a fluid, such as stainless steel and gray cast iron.

The blade 33 has a cross section orthogonal to the fluid transport direction of the blade 33 having a convex shape on the positive pressure surface 33c and a concave shape on the negative pressure surface 33d, and has a maximum wall thickness in the middle of the blade length from the leading edge 33a to the trailing edge 33b. It has a shape having a cross-sectional shape of a blade (that is, the thickness is not constant).

The pump device 10 is a pressure in the space from each trailing edge 33b to the straightening vane 18 provided on the downstream side of each trailing edge 33b locally in the vicinity of the trailing edge 33b of the blade 33 (hereinafter referred to as “)”. It has a high pressure region HP whose pressure is about 20% or more (in many cases 50% or less) higher than the average of ambient pressure), and negative pressure is applied to the positive pressure surface 33c side of the trailing edge 33b of the blade 33. In addition, it may be in a state of having a low pressure region LP extremely lower than the ambient pressure (see FIG. 5).

In that case, although the pump device 10 is designed so that cavitation does not easily occur in the blade 33, for example, the suction pressure changes due to the fluctuation of the suction water level, so that the pressure state around the blade 33 becomes more than acceptable. It is lowered, which makes it easy for cavitation to occur, and there is a possibility that cavitation-induced erosion may occur especially on the trailing edge 33b of the blade 33.

If the trailing edge 33b of the blade 33 is eroded, the performance of the pump device 10 is significantly deteriorated. Therefore, the maintenance method according to the present invention is executed at regular intervals, for example, annual maintenance and inspection.

The maintenance method includes a confirmation step of confirming whether or not a sign of erosion or erosion has occurred on the trailing edge 33b of at least one of the four blades 33, and the blade 33 in the confirmation step. 4 When it is confirmed that erosion is actually occurring at the trailing edge 33b, or even if the occurrence of erosion is not confirmed at the trailing edge 33b, it is confirmed that the sign is occurring. It has a processing step of scraping each trailing edge 33b of a single blade.

Further, in the maintenance method, even if cavitation is not confirmed on the trailing edge 33b of any of the four blades 33, the pump is applied to the positive pressure surface 33c of any of the blades 33. When it was directly confirmed visually or the like that cavitation had occurred during the operation of the device 10, or there were traces of cavitation occurring during the operation of the pump device 10, such as scratches or peeling of the paint, were confirmed. If so, the mixed flow impeller 13 has a fluid analysis step of performing the fluid analysis.

As a result of the fluid analysis step, a low pressure region is generated on the positive pressure surface 33c side of the trailing edge 33b of at least one of the four blades 33, and a local high pressure region is generated in the vicinity of the trailing edge 33b. It was confirmed that when the pressure difference between the pressure in the low pressure region LP (see FIG. 5) and the pressure in the high pressure region HP (see FIG. 5) exceeds a predetermined threshold, there is a sign of erosion on the trailing edge 33b. Judge that it has occurred. The predetermined threshold value is a value individually determined according to the design of the pump device 10.

As shown in FIG. 3, when it is confirmed that erosion has occurred or a sign of erosion has occurred on the trailing edge 33b of at least one of the four blades 33. Even if the blade 33 for which the occurrence of erosion or its sign has not been confirmed at the trailing edge 33b, erosion may occur over time. Therefore, the processing step is performed on all the blades 33 including the blade 33. Will be executed. In FIG. 3, the contour of the blade 33 before processing is represented by a two-dot chain line, and the contour of the blade 33 after processing is represented by a solid line. This makes it possible to suppress erosion at the trailing edges 33b of all the blades 33. In the processing process, the balance of the mixed flow impeller 13 is adjusted at the same time.

In the processing process, in the range where the performance change (HQ, efficiency, cavitation) is not adversely affected, that is, in the range of the rotating outer peripheral surface 33e where the positive pressure surface 33c is not cut, the negative pressure surface 33d side of each trailing edge 33b of the four blades. Is scraped toward the leading edge 33a of each blade 33. The rotation outer peripheral surface 33e overlaps with the outer peripheral surface of the rotation range of the blade 33 when the impeller 13 is rotated, and is a continuous surface between the positive pressure surface 33c and the leading edge 33a side of the blade 33. This is an area that is not considered when designing.

Specifically, it is cut within a depth range of several times, for example, about 3 times the thickness of the blade 33 in the vicinity of the trailing edge 33b. At that time, processing is performed so that the processing range is widened toward the leading edge 33a side from the inside to the outside with respect to the rotation axis of the mixed flow impeller 13 (in FIG. 2, the contour of the blade 33 before processing is represented by a solid line. , The contour of the blade 33 after processing is represented by a alternate long and short dash line.) As a result, the negative pressure surface 33d of each trailing edge 33b of the four blades 33 has a convex shape as if it were shaved toward the leading edge 33a of each blade 33.

By changing the shape of the negative pressure surface 33d of the trailing edge 33b of the blade 33 by the machining process, the pressure in the low pressure region LP (see FIG. 6) on the positive pressure surface 33c side of the trailing edge 33b of the blade 33 is reduced before the machining. Can be raised in comparison.

As a result, the pressure difference between the pressure in the low pressure region LP (see FIG. 6) on the positive pressure surface 33c side of the trailing edge 33b of the blade 33 and the pressure in the high pressure region HP (see FIG. 6) near the trailing edge 33b of the blade 33 is reduced. It gets smaller. Therefore, cavitation itself is unlikely to occur, and even if bubbles are generated by cavitation, their collapse is unlikely to occur. As a result, new erosion is suppressed, and the performance deterioration of the mixed flow impeller 13 is improved.

Note that FIG. 5 shows the blade 33 before the negative pressure surface 33d side of the trailing edge 33b is machined. According to the analysis, the pressure difference between the low pressure region LP of the positive pressure surface 33c of the trailing edge 33b and the local high pressure region HP in the vicinity of the trailing edge 33b of the blade 33 is about 1.7 times the total head of the pump. As described above, when the pressure difference is high, there is a high possibility that cavitation-induced erosion will occur.

FIG. 6 shows the blade 33 after the maintenance method has been executed for the blade 33, that is, after the negative pressure surface 33d side of the trailing edge 33b has been machined. According to the analysis, after executing the maintenance method, the pressure difference of the mixed flow impeller 13 decreased to about 0.5 times the total head of the pump. Then, it was confirmed that the trailing edge 33b did not corrode in the blade 33 after such processing.

In the above description, in the processing step of the maintenance method, the case where the negative pressure surface 33d side of each trailing edge 33b of the blade 33 is shaved toward the leading edge 33a of each blade 33 has been described, but the present invention is not limited to this. .. In the processing step, each trailing edge 33b may be rounded in a range where the performance change (HQ, efficiency, cavitation) is not adversely affected, that is, in the range of the rotary outer peripheral surface 33e where the positive pressure surface 33c is not cut.

Specifically, as shown in FIG. 4, the trailing edge 33b is cut into a semicircle having the thickness of the blade 33 in the vicinity of the trailing edge 33b as the diameter. In FIG. 4, the contour of the blade 33 before processing is represented by a two-dot chain line, and the contour of the blade 33 after processing is represented by a solid line. At that time, the blade 33 is processed so as to be closer to the leading edge 33a side than the inner side with respect to the rotation axis of the mixed flow impeller 13 (in FIG. 2, the contour of the blade 33 before processing is represented by a solid line, and after processing. The contour of the blade 33 is represented by a alternate long and short dash line.) As a result, each trailing edge 33b of the four blades 33 is rounded to form a convex shape on the negative pressure surface 33d side.

The maintenance method according to the present invention is executed for the existing pump device 10 provided with the mixed flow impeller 13, but a newly manufactured mixed flow impeller, that is, a plurality of blades 33. It can also be applied to the design method of the pump device 10 provided with the mixed flow impeller 13 having the above.

That is, the design method includes a fluid analysis step of performing a fluid analysis on a mixed flow impeller 13 formed in a predetermined shape, and a blade 33 of at least one of a plurality of blades 33 in the fluid analysis step. When it is confirmed that a low-pressure region LP is generated on the positive pressure surface 33c side of the trailing edge 33b and a local high-pressure region HP is generated in the vicinity of the trailing edge 33b, each trailing edge 33b of the plurality of blades 33 It has an adjustment step of changing the shape so that the negative pressure surface 33d side of the blade 33 approaches the leading edge 33a of each blade 33, or changing the shape so that each trailing edge 33b is rounded.

At that time, when changing the shape so that the negative pressure surface 33d side of the trailing edge 33b approaches the leading edge 33a of each blade 33 in the adjustment step, the front side of the rotation shaft 12 of the impeller 13 is closer to the outside than the inside. It is preferable to change the shape so that the range closer to the edge 33a is widened, and when the shape is changed so that the trailing edge 33b is rounded in the adjustment step, the trailing edge 33b is rearward from the inside to the outside of the rotating shaft 12 of the impeller 13. It is preferable to change the edge 33b so as to approach the leading edge 33a.

The maintenance method according to the present invention can also be executed for the pump device 10 provided with the mixed flow impeller 13 manufactured by such a design method.

Further, the pump device 10 itself provided with the mixed flow impeller 13 manufactured by the design method as described above is also within the scope of the present invention. That is, the pump device 10 is a pump device 10 provided with a mixed flow impeller 13 having a plurality of blades 33 and a rotary shaft 12 of a vertical shaft connected to the mixed flow impeller 13, and the blades 33 are. The cross section of the blade 33 orthogonal to the fluid transport direction has a convex shape on the positive pressure surface 33c, a concave shape on the negative pressure surface 33d, and a convex shape on the negative pressure surface 33d of the trailing edge 33b of the blade 33. At that time, the negative pressure surface 33d side of the trailing edge 33b has a shape so that the range closer to the leading edge 33a of the blade 33 becomes wider than the inside to the rotation shaft 12 of the mixed flow impeller 13. The trailing edge 33b has a shape rounded so as to approach the leading edge 33a of the blade 33.

Instead of the fluid analysis process for the mixed flow impeller 13, for example, by incorporating it into the experimental pump device 10 provided in the experimental equipment and operating it, the actual state of cavitation is visually confirmed. May be good. However, when cavitation occurs, erosion does not always occur.

In the above-described embodiment, the case where the blade 33 of the mixed flow impeller 13 is fixedly provided with respect to the boss portion 32 has been described, but the present invention is not limited to this. The oblique impeller 13 may be configured such that the blade angle of the blade 33 can be changed. If a defect occurs in which the blade angle of the blade 33 is not changed as designed, erosion is likely to occur. Therefore, according to the maintenance method, design method, and pump device of the pump device according to the present invention. This is because such erosion can be effectively suppressed.

In the above-described embodiment, the case where the pump device 10 is provided with the mixed flow impeller 13 has been described, but the present invention is not limited to this. The pump device 10 may be provided with an axial flow impeller or a centrifugal impeller instead of the mixed flow impeller 13.

The above-described embodiments are all examples of the present invention, and the description thereof does not limit the present invention, and the specific configuration of each part can be appropriately modified and designed within the range in which the effects of the present invention are exhibited. be.

10: Pump device 12: Rotating shaft 13: Diagonal flow impeller (impeller)
18: Rectifying blade 33: Blade 33a: Leading edge 33b: Trailing edge 33c: Positive pressure surface 33d: Negative pressure surface HP: High pressure region LP: Low pressure region

Claims (9)

It is a maintenance method of a pump device equipped with an impeller having multiple blades.
A confirmation step for confirming whether or not erosion or signs of erosion have occurred on the trailing edge of at least one of the blades.
When it is confirmed that erosion or a sign of erosion has occurred in the confirmation step, the negative pressure surface side of each trailing edge of each blade is scraped toward the leading edge of each blade, or the above. A maintenance method for a pump device, which comprises a processing step of shaving each trailing edge so as to be rounded. In the confirmation step, even if no erosion is confirmed on the trailing edge of any of the blades, cavitation is generated on the positive pressure surface of any of the blades during the operation of the pump device. If it has occurred or has been confirmed to have occurred, the impeller has a fluid analysis step to perform fluid analysis.
As a result of the fluid analysis step, it was confirmed that a low pressure region was generated on the positive pressure surface side of the trailing edge of at least one of the blades, and a local high pressure region was generated in the vicinity of the trailing edge. The pump according to claim 1, wherein when the pressure difference between the pressure in the low pressure region and the pressure in the high pressure region exceeds a predetermined threshold value, it is determined that a sign of erosion has occurred at the trailing edge. Equipment maintenance method. When the negative pressure surface side of the trailing edge is shaved toward the leading edge of each blade in the machining step, the machining range is widened toward the leading edge from the inside to the outside with respect to the rotation axis of the impeller. The maintenance method of the pump device according to claim 1 or 2. The invention according to claim 1 or 2, wherein when the trailing edge is rounded in the machining step, the trailing edge is machined so as to be closer to the leading edge from the inside to the outside with respect to the rotation axis of the impeller. Maintenance method of pump equipment. A method of designing a pump device equipped with an impeller with multiple blades.
A fluid analysis step of performing fluid analysis on the impeller formed in a predetermined shape, and
In the fluid analysis step, it was confirmed that a low pressure region was generated on the positive pressure surface side of the trailing edge of at least one of the blades, and a local high pressure region was generated in the vicinity of the trailing edge. When the pressure difference between the pressure in the low pressure region and the pressure in the high pressure region exceeds a predetermined threshold value, each trailing edge of each blade approaches the leading edge and positive pressure surface of each blade. The present invention includes an adjustment step of changing the shape of the negative pressure surface of each blade so that a convex shape is formed on the negative pressure surface of each blade, or changing the shape so that the trailing edge of each blade is rounded. How to design a featured pumping device. The shape of the negative pressure surface of each blade so that the trailing edge approaches the leading edge and the positive pressure surface of each blade in the adjustment step, whereby a convex shape is formed on the negative pressure surface of each blade. 5. The fifth aspect of the present invention is to change the range defined by the trailing edge and the convex shape of the negative pressure surface so as to extend from the inside to the outside with respect to the rotation axis of the impeller. How to design a pumping device. The fifth aspect of claim 5 is that when the shape is changed so that the trailing edge is rounded in the adjusting step, the trailing edge is changed so as to be closer to the leading edge than the inside to the rotation axis of the impeller. How to design a pumping device. A pump device provided with a mixed flow impeller having a plurality of blades and a rotating shaft of a vertical shaft connected to the mixed flow impeller.
The blade has a cross section orthogonal to the fluid transport direction of the blade having a convex shape on the positive pressure surface, a concave shape on the negative pressure surface, and a convex shape on the negative pressure surface near the trailing edge of the blade .
The convex shape of the negative pressure surface overlaps with the outer peripheral surface of the rotation range of the blade when the oblique flow impeller is rotated, and occurs when the rotation outer peripheral surface which is a surface continuous with the positive pressure surface is projected onto the negative pressure surface. A pump device characterized by being located on the front edge side of the blade beyond the projection plane . The pump device according to claim 8, wherein the range defined by the convex shape of the trailing edge and the negative pressure surface has a shape that extends from the inside to the outside with respect to the rotation axis of the mixed flow impeller. ..

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