JP4951418B2 - Multistage centrifugal pump - Google Patents

Description

  The present invention relates to a plurality of impellers arranged in parallel so as to be rotatable by the same rotating shaft, and a single or a plurality of guide vanes that form a flow path that connects an outlet of a front impeller and an inlet of a rear impeller. A multistage centrifugal pump comprising:

  Conventionally, the impeller of a multistage centrifugal pump sucks fluid from the direction of the rotation axis and discharges it in the centrifugal direction. Therefore, in the case of a uniaxial multistage configuration, a flow path that guides the fluid that has flowed in the centrifugal direction from the preceding impeller to the suction port directed in the axial direction of the subsequent impeller is necessary. A guide blade is often provided in the flow path.

  The purpose of providing the impeller here is to give pressure energy to the water, but as a characteristic of the centrifugal impeller, the velocity energy still accounts for 20-30% at the exit of the impeller. In order to convert velocity energy into pressure energy, in a multistage centrifugal pump, as a passage that connects the fluid that flows out in the centrifugal direction from the preceding impeller to a flow path that leads to the suction port facing the axial direction of the next impeller, A diffuser that expands the flow path of the fluid flowing out in the centrifugal direction is used.

  A typical one used as a diffuser of a multistage centrifugal pump is a circular blade cascade diffuser, which is called a guide vane. That is, a plurality of blades that are relatively short in length and are arranged in a spiral shape on the outer side of the impeller and arranged in a spiral shape. A flow path is formed. Further, a return vane is provided in a return flow path connecting the guide vane and the next stage impeller entrance, and the return vane is also known to have a circular blade row shape (eg, patent document). 1). In the return vane, blade rows in which the respective blades extend long in the radial direction outside and inside are arranged in the circumferential direction and spirally.

  In FIG. 8, the structure of a conventional guide vane is shown partially enlarged. In the guide vane 15, a guide vane 19 formed as a circular blade row on the outer side in the radial direction of the main plate 21 forms a diffuser flow path 16 between adjacent guide vanes 19. A return vane 20 is formed on the back side of the main plate 21 in the drawing, and the return vane 20 extends in an arc shape to the radially outermost position of the main plate 21. An opening 23 (shown by hatching) that crosses the guide vane 15 is formed in an area surrounded by the guide vane 19, the return vane 20, and the inner casing 12 in order to pass the water sent by the impeller. The opening 23 is limited by the guide vane 19 and the return vane 20.

Further, it is known that the guide vane and the return vane are configured with the same number of blades, and the guide vane and the return vane are integrated to form a guide blade (for example, see Patent Document 2). These technologies are used in large pumps where the hydraulic performance of the pump is important. On the other hand, since miniaturization is more important than hydraulic performance in a small pump, there is known one that eliminates a flow path formed by a casing and guide vanes (see, for example, Patent Document 3).
JP-A-2-301699 Japanese Patent No. 3872447 JP 2004-183486 A

  However, small pumps are required to improve hydraulic performance from the viewpoint of energy saving, and are also required to reduce vibration and noise because they are used for water supply in condominiums and the like. Particularly for vibration reduction, it is necessary to reduce the pressure pulsation of the water flow, and it is necessary to minimize the influence of the wake of the impeller blades, which is the main factor.

  An object of the present invention is to provide a multistage centrifugal pump that is small in size, low in vibration and low in noise while having high efficiency.

  In order to solve the above problems and achieve the above object, the present invention provides a plurality of impellers arranged in parallel so as to be rotatable by the same rotating shaft, and an outlet of the preceding impeller and an inlet of the rear impeller. A single or a plurality of guide vanes that form a flow path, each guide vane being a main plate that partitions between the preceding impeller and the rear impeller, outside the outlet of the preceding impeller A guide vane provided on the main plate as a cascade arranged in an annular region concentrically with the rotating shaft, and an arcuate shape arranged circumferentially in a side region on the impeller side of the main plate on the main plate. In a multistage centrifugal pump having a return vane provided as a blade row, and a flow passage between blades adjacent to the guide vane is formed in a diffuser, the number of blades in the blade row of the guide vane is the number of blades of the return vane. Number of blades in cascade Remote most, it is characterized in that the free passage area no cascade between said annular region and the side regions are formed.

  According to this multistage centrifugal pump, the guide vanes form a diffuser by arranging the circular blade rows, the return vanes are also arranged in the circular blade rows, and the number of guide vane blades is larger than the number of return vane blades. Is provided. The number of guide vane blades can be determined so that the design values of chordal ratio, divergence angle, and diffuser length are optimal, and the diffuser performance of the guide vane composed of circular blade rows is improved. In addition, the pressure pulsation of the water flow that is the cause of the vibration is caused by the influence of the blade wake behind the impeller, but in the present invention, between the annular region where the guide vane is disposed and the side region where the return vane is disposed. By forming a free flow path area that does not have a circular blade row, the pressure pulsation generated by the impeller and the wake of the guide vane blade row interferes, and flow mixing is promoted. It is done.

In the multistage centrifugal pump, the free flow path region can be formed radially outside the side region on the impeller side of the rear stage of the main plate. Further, the free flow channel region can be formed on the exit side of the guide vane on the impeller side of the front stage of the main plate. In the case where a free flow path region without a circular blade row between the guide vane and the return vane is provided on the impeller side at the rear stage of the main plate, that is, on the return vane side of the main plate of the guide vane, the free flow path region is provided. Since it is not formed on the impeller side in front of the main plate, the diffuser length of the guide vane can be sufficiently secured, and the diffuser performance can be further improved.
Further, the free flow path region can also be formed from the outlet of the guide vane through the gap left between the radial outer end of the main plate and the inner surface of the pump casing and connected to the inlet of the return vane. .

  In the multistage centrifugal pump, the main plate of the guide vane is formed with a two-sided notch-shaped opening connecting the front impeller side and the rear impeller side to form a triangle between the casing inner surface The first side of the opening is a connecting ridge line portion where the main plate is connected to the airfoil of the guide vane, and the second side is from the blade tip of the adjacent blade that forms the diffuser with the blade of the guide vane. It can be set as the notch edge part dropped to the said connection ridgeline part of the said guide vane. That is, since the triangular opening area can be increased as compared with the conventional technique (see Patent Document 3) in which the third side of the triangle is formed of a part of the airfoil of the return vane, hydraulic loss is reduced. can do.

  In the multi-stage centrifugal pump, the number of return vane blades and the number of guide vane blades are such that the number of return vane blades is one more than the number of impeller blades, and the number of guide vane blades is between the number of impeller blades. And a combination having no common divisor between the number of return vane blades. By increasing the number of return vane blades by one more than the number of impeller blades, the return vane rectifying effect is improved, and the reduction of the flow path area, which is a negative effect when the number of blades increases, is minimized, and hydraulic performance is improved. Can be improved. In addition, since there is no common divisor for the number of return vane blades and the number of impeller blades, the wake of each return vane blade row does not face each blade of the impeller at the same time. It is relaxed and vibration can be reduced.

  In the above multi-stage centrifugal pump, by combining the number of guide vane blades with the number of impeller blades so that there is no common divisor, the wake of each impeller blade is not simultaneously opposed to each of the guide vane blade rows. The fluid force is relaxed and vibration can be reduced. In addition, by using a combination in which there is no common divisor between the number of guide vane blades and the number of return vane blades, the wake of each guide vane blade row does not simultaneously face each return vane blade row, so the fluid force to the return vane is relaxed. , Vibration can be reduced.

  As described above, according to the multistage centrifugal pump of the present invention, the diffuser performance of the guide vane can be improved while being small, and a high-efficiency pump with little hydraulic loss is realized. In addition, since the fluid force acting on the impeller, guide vane, and return vane can be reduced and the pressure pulsation of the water flow can be reduced, a low vibration pump is realized. Therefore, it is possible to provide a multistage centrifugal pump with high efficiency, low vibration, and low noise.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 4 is an overall perspective view of a multistage centrifugal pump including an embodiment of the present invention, and FIG. 5 is a longitudinal sectional view of the multistage centrifugal pump shown in FIG.

  As shown in FIG. 4, the multistage centrifugal pump 1 is a pump that is driven by a motor 2 that is supplied with electric power provided on one side, and is taken from a suction port 31 provided on the outer casing 3 on the other end side. This is a pump that discharges water with pressure to a discharge port 32 formed on the outer casing 3 facing upward.

  As shown in FIG. 5, the multistage centrifugal pump 1 has a multistage structure in which centrifugal impellers 4a, 4b, and 4c are provided coaxially. When the impellers 4a, 4b, and 4c are rotated by the output of the motor 2, water flows from the suction port 31 of the outer casing 3 and flows into the first stage impeller 4a. The flow of water boosted by the first stage impeller 4a flows out in the centrifugal direction from the exit of the impeller toward the guide vane channel 6 provided outside the impeller 4a. The flow that flows out of the impeller 4a passes through the guide vane flow path 6 of the guide vane 5, the triangular opening 13, the return flow path 7, and the return vane flow path 8 toward the suction port of the second stage impeller 4b. .

  FIG. 1 is a perspective view of the guide vanes used in the multistage centrifugal pump according to the present invention as seen from the guide vane side, and FIG. 2 is a perspective view of the guide vanes used in the multistage centrifugal pump according to the present invention as seen from the return vane side. is there. FIG. 3 is a view showing a guide blade of the present invention and showing a triangular opening.

  The guide vane 5 includes a main plate 11 that partitions between a front impeller and a rear impeller, guide vanes 9 that are provided in an array of circular blade rows on the radially outer side of the main plate 11, and a next step of the main plate 11. And a return vane 10 provided in a side region on the guide blade side in an array of circular blade rows. That is, the guide vane 9 is provided on the main plate 11 as a blade row arranged in a circumferential direction in an annular region formed concentrically with the rotating shaft outside the outlet of the preceding impeller, and the return vane 10 is provided on the main plate 11. Are provided as arcuate blade rows arranged in the circumferential direction in the side region on the impeller side of the rear stage.

  By combining the inner casing 12, the front inner casing and the rear inner casing so as to sandwich the guide vane 5, a guide vane flow path 6 is formed between the adjacent guide vanes 9 and 9, and the opening across the main plate 11. A triangular opening 13 is formed, a return flow path 7 is formed as a free flow path region without a circular blade row, and a return vane flow path 8 is formed between adjacent return vanes 10 and 10. Yes.

  In the present invention, each vane of the guide vane 9 is arranged with a divergence angle, and the guide vane channel 6 formed between the adjacent vanes is formed as a diffuser having an enlarged channel area in the water flow direction. . When the number of blades decreases, the gap between adjacent blades of the guide vane flow path 6 increases and the overlap between adjacent blades decreases, so the diffuser length decreases and the performance decreases. In this embodiment, the number of blades decreases. Is set to 11 sheets, and a sufficient diffuser length is secured.

  In the case of the present invention, as shown in FIG. 3, the main plate 11 formed so as to be orthogonal to the guide vane connects the front impeller side and the rear impeller side to form a triangle between the inner casing 12. A two-sided notch-shaped opening 13 to be formed is formed. The first side of the opening 13 is a connecting ridge line portion 13 a where the main plate 11 is connected to the airfoil of the guide vane 9, and the second side is a blade of an adjacent blade that forms the diffuser flow path 6 with the blade of the guide vane 9. This is a notched edge portion 13 b that is lowered from the end to the connecting ridge line portion 13 a of the guide vane 9.

  Since the area of the opening 13 is not restricted by the return vane 10, it can be made larger than the conventional technique shown in FIG. Therefore, the approach speed to the return flow path 7 provided on the return vane 10 side of the main plate 11 and having no circular blade row can be made slower than that of the prior art. The return flow path 7 causes a decrease in performance because the flow of water in the guide vanes 5 is reversed 180 degrees from the centrifugal direction to the axial direction, and causes the speed of entry into the return flow path 7 to be slower than that of the prior art. As a result, performance degradation can be reduced. In addition, as for the shape of the main board 11, it is desirable to form between 80 degrees-100 degrees by the difference in the blade | wing shape of a guide vane.

  Further, in the case of the present invention, a return flow path 7 as a free flow path region having no circular blade row is provided between the guide vane flow channel 6 and the return vane flow channel 8, so that The pressure pulsation generated by the flow and the impeller interferes with each other and the mixing of the flow is promoted, so that the pressure pulsation is reduced, which is effective in reducing vibration and noise. In the case where the free flow path region is not provided, the pressure pulsation generated by the wake of the blade row of the guide vane 9 and the impeller is prevented from interfering with each other by the return vane 10, and as a result, the mixing of the flow is promoted. However, pressure pulsation tends to remain.

  Further, in the case of the present invention, each vane of the return vane 10 forms a return vane channel 8 whose channel area is reduced in the direction of water flow with the adjacent vane, and guides the flow of water to the next stage impeller inlet. Has been placed. By reducing the swirl component of the flow of each blade, it is possible to reduce the influence of the performance deterioration at the next stage impeller inlet. When the number of blades is increased, the swirl component of the flow is reduced, but the total thickness of the blades is increased, so that the exit area of the return vane flow path 8 is reduced, and water is present at the inlet of the next stage impeller that turns 90 degrees. The flow of water increases and hydraulic performance decreases. By restricting the number of blades of the return vane 10 to one more than the number of blades of the next stage impeller, the rectifying effect of the return vane 10 is increased, and the reduction of the flow path area, which is a harmful effect when the number of blades increases, is minimized. By improving the hydraulic performance.

  In the case of the present invention, by using a combination in which there is no common divisor for the number of guide vane 9 blades and the number of blades of the impeller, the wake of each blade of the impeller does not simultaneously face each of the guide vane 9 blade rows. The fluid force to the guide vane 9 is relaxed and vibration can be reduced. Further, by using a combination in which there is no common divisor between the number of guide vane 9 blades and the number of return vane 10 blades, the wake of each guide vane 9 blade row does not simultaneously face each of the return vane 10 blade rows. The fluid force is relaxed and vibration can be reduced.

As for the free flow path region where the blade row does not exist, instead of the one shown in FIG. 3, the guide vane 9 exit side on the front impeller side of the main plate 11 as shown in FIG. The region 7a formed in the step can be formed.
Further, as shown in FIG. 7 as the guide vane 5b, the free flow path region is returned from the outlet of the guide vane 9 through the gap left between the radially outer end of the main plate 11 and the inner casing 12. It can also be formed as a passage 7 b connected to the entrance of the vane 10. In this case, although not shown, the guide blade 5b can be fixed to the casing 3 by an appropriate means.

  According to the present invention, the outer diameter of the guide vane can be reduced, and the equivalent performance can be maintained and the size can be reduced by increasing the number of the guide vane 9 blades. Further, the material cost is reduced by downsizing, so that the cost can be reduced. Furthermore, according to the present invention, a multistage centrifugal pump having high efficiency, low vibration, low noise, and low cost can be obtained.

It is a front side perspective view of the guide blade used for the multistage centrifugal pump by this invention. It is a back | latter stage side perspective view of the guide blade | wing used for the multistage centrifugal pump by this invention. It is a figure showing the opening part formed in the guide blade used for the multistage centrifugal pump by this invention. It is a perspective view of the multistage centrifugal pump of the present invention. It is a longitudinal cross-sectional view of the multistage centrifugal pump by this invention. It is a figure which shows another example of a free flow path area | region. It is a figure which shows another example of a free flow path area | region. It is a figure showing the opening part formed in the guide blade used for the conventional multistage centrifugal pump.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Multistage centrifugal pump, 2 ... Motor, 3 ... Outer casing, 4 ... Impeller, 5, 5a, 5b ... Guide vane, 6 ... Guide vane flow path, 7, 7a, 7b ... Return flow path, 8 ... Return vane Flow path, 9 ... guide vane, 10 ... return vane, 11 ... main plate, 12 ... inner casing, 13 ... triangular opening, 13a ... connection ridge line part, 13b ... notch edge part

Claims (7)

A plurality of impellers arranged side by side so as to be rotatable by the same rotation shaft, and a single or a plurality of guide vanes that form a flow path connecting the outlet of the preceding impeller and the inlet of the subsequent impeller ,
The guide vanes are arranged in a circumferential direction in an annular region formed concentrically with the rotating shaft on the outer side of the outlet of the impeller at the front stage, a main plate that partitions the impeller at the front stage and the impeller at the rear stage. A guide vane provided on the main plate as a row of blades, and a return vane provided as an arcuate blade row arranged in the circumferential direction in a side region on the impeller side of the main plate on the main plate;
In the multistage centrifugal pump in which the flow path between adjacent blades of the guide vane is formed in the diffuser,
The number of blades in the blade row of the guide vane is larger than the number of blades in the blade row of the return vane, and a free flow path region in which no blade row exists between the annular region and the side region is formed,
A multistage centrifugal pump characterized by that. In the multistage centrifugal pump according to claim 1,
The free flow path region is formed on the radially outer side of the side surface region on the impeller side of the rear stage of the main plate.
A multistage centrifugal pump characterized by that. In the multistage centrifugal pump according to claim 1,
The free flow path region is formed from the outlet of the guide vane, through a gap left between the radial outer end of the main plate and the inner surface of the pump casing, and connected to the inlet of the return vane.
A multistage centrifugal pump characterized by that. In the multistage centrifugal pump according to claim 1,
The free flow path region is formed on the exit side of the guide vane on the impeller side of the front stage of the main plate,
A multistage centrifugal pump characterized by that. In the multistage centrifugal pump according to claim 1,
The main plate of the guide vane is formed with a two-sided notch-like opening that connects the front impeller side and the rear impeller side to form a triangle between the casing inner surface and the opening. The first side of the part is a connecting ridge line part where the main plate is connected to the airfoil of the guide vane, and the second side is the guide vane from the blade tip of the adjacent blade that forms the diffuser with the blade of the guide vane. Is a notched edge part lowered to the connecting ridge line part of
A multistage centrifugal pump characterized by that. In the multistage centrifugal pump according to any one of claims 1 to 5,
The number of blades of the return vane is different from the number of blades of the impeller.
A multistage centrifugal pump characterized by that. The multistage centrifugal pump according to claim 6,
The number of return vane blades and the number of guide vane blades are such that the number of return vane blades is one more than the number of impeller blades, the number of guide vane blades is between the number of impeller blades and the number of return vane blades. Is a combination with no common divisor between
A multistage centrifugal pump characterized by that.

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