JP2017082658A - Centrifugal Pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal pump that has a simpler structure compared to conventional pumps and can reduce axial thrust while maintaining good pump efficiency.SOLUTION: A centrifugal pump 100 includes: a side chamber 30 that is formed between a side plate 13 of an impeller 10 and a first opposing surface 20a of a casing 20 opposing to the side plate 13; and a clearance S1 that is formed between an outer peripheral end surface of the side plate 13 and a second opposing surface 20b of the casing 20 opposing to the outer peripheral end surface to surround its whole circumference and communicates the side chamber 30 and a main flow passage 22 with each other. A groove portion 33 is formed on the second opposing surface 20b of the casing 20 forming the clearance S1 to extend between the side chamber 13 and the main flow passage 22.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a centrifugal pump.

Conventionally, in a centrifugal pump having a closed type impeller in a casing, as a measure to reduce shaft thrust generated in the impeller, radially from the impeller rotating shaft side to the inner wall surface of the casing facing the impeller side plate in a radial direction. Those having extended grooves and fixed blades are known (see, for example, Patent Documents 1 and 2).
In such a centrifugal pump, the speed of the swirling flow of the fluid flowing in the gap (leakage flow path) formed between the side plate of the impeller and the inner wall surface of the casing is reduced by the groove and the fixed blade. As a result, the centrifugal pump reduces the axial thrust by increasing the pressure in the gap and reduces the load on the thrust bearing.

Japanese Patent Laid-Open No. 9-317685 US Pat. No. 5,320,482

However, in the axial thrust countermeasure in the conventional centrifugal pump (for example, refer to Patent Documents 1 and 2), the groove and the fixed blade increase the frictional resistance between the fluid in the gap (leakage flow path) and the rotating impeller. Let In other words, since the shaft power of the impeller increases in the conventional shaft thrust countermeasure, the pump efficiency obtained by dividing the product of the fluid flow rate and the head by the shaft power is reduced.
Further, in the conventional centrifugal pump (for example, see Patent Documents 1 and 2), the manufacturing process is complicated due to the formation of radial grooves and the attachment of fixed blades.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a centrifugal pump that has a simple structure as compared with the prior art and can reduce axial thrust while maintaining good pump efficiency.

  The present invention that has solved the above problems includes an impeller having a fluid pressure increasing channel between a main plate and a side plate, a casing that houses the impeller inside, and a fluid discharge port of the pressure increasing channel on the outer peripheral side of the impeller. A centrifugal pump having a fluid main flow path formed in the casing so as to face, and formed between a plate surface of the side plate and a first opposed surface of the casing facing the plate surface. Formed between the outer side end surface of the side plate and the second opposing surface of the casing facing the outer peripheral end surface so as to surround the outer peripheral end surface, and communicating the side chamber and the main channel. And a groove portion is formed on the second facing surface of the casing forming the gap so as to extend between the side chamber and the main flow path.

  ADVANTAGE OF THE INVENTION According to this invention, it has a simple structure compared with the past, and can provide the centrifugal pump which can reduce a shaft thrust, maintaining pump efficiency favorable.

1 is a cross-sectional view schematically showing an overall configuration of a centrifugal pump according to an embodiment of the present invention. It is the partial expansion longitudinal cross-sectional view which expanded partially the impeller vicinity of the centrifugal pump which concerns on embodiment of this invention. FIG. 3 is a partial sectional view taken along line III-III in FIG. 2. It is a graph which shows the relationship between the position of the axial direction from the entrance of the 1st clearance gap of the centrifugal pump shown in FIG. 2 to the exit of the 1st clearance gap, and the turning speed of the leakage flow in a 1st clearance gap. It is a graph which shows the relationship between the radial position from the entrance of the 1st side chamber of the centrifugal pump shown in FIG. 2 to the exit of the 1st side chamber, and the pressure of a 1st side chamber. It is the elements on larger scale which expanded partially the impeller vicinity of the multistage centrifugal diffuser pump which concerns on other embodiment of this invention. It is a VII-VII partial sectional view of FIG. It is a graph which shows the relationship between the position of the axial direction from the entrance of the 1st clearance gap of the centrifugal pump shown in FIG. 6 to the exit of the 1st clearance gap, and the turning speed of the leakage flow in a 1st clearance gap. It is composition explanatory drawing of the centrifugal pump in which a groove | channel inclines. It is composition explanatory drawing which shows the modification of a groove | channel. It is composition explanatory drawing which shows the modification of a groove | channel. It is a structure explanatory view showing other modifications of a groove, and is a figure corresponding to a partial expanded sectional view near a groove in the centrifugal pump of FIG. FIG. 13 is a partial sectional view taken along line XIII-XIII in FIG. 12. FIG. 14 is a configuration explanatory view showing another modified example of the groove, corresponding to FIG. 13.

Embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
The centrifugal pump according to the present embodiment is different from the axial thrust countermeasure of the conventional centrifugal pump (for example, see Patent Documents 1 and 2), and the fluid in the leakage flow path is not provided with the radial grooves and fixed blades. It was set as the structure which suppresses turning. That is, the axial thrust countermeasure of the centrifugal pump according to the present embodiment is performed between the leakage flow path (first side chamber to be described later) and the main flow path (hereinafter simply referred to as “main flow path”) facing the discharge port of the impeller fluid. The main feature is that a groove is formed on the inner wall surface of the casing so as to extend at the same time.

  In this embodiment, an example in which the present invention is applied to a centrifugal pump having a spiral volute (spiral casing) will be described. In addition, about the diffuser pump which has a guide blade, it demonstrates taking the case of a multistage centrifugal diffuser pump in the column of other embodiment.

FIG. 1 is a cross-sectional view schematically showing an overall configuration of a centrifugal pump 100 according to an embodiment of the present invention. In FIG. 1, the side plate 13 (see FIG. 2) of the impeller 10 is omitted for convenience of drawing.
FIG. 2 is a partially enlarged longitudinal sectional view in which the vicinity of the impeller 10 of the centrifugal pump 100 according to the present embodiment is partially enlarged, and shows the upper half side with the center line of the main shaft 17 as a boundary.
In the following description, the front-rear direction corresponds to a later-described side plate 13 (refer to FIG. 2) also referred to as a front shroud and a later-described main plate 11 (refer to FIG. 2) also referred to as a rear shroud. The forward and backward directions indicated by the arrows are used as a reference.

As shown in FIG. 1, a centrifugal pump 100 according to the present embodiment includes a main shaft 17 that is rotated by a prime mover (not shown), an impeller (centrifugal impeller) 10 that is driven to rotate by the main shaft 17, and an impeller 10 that is disposed inside. And a casing 20 housed in the housing.
In FIG. 1, reference numeral 11 denotes a main plate of the impeller 10, reference numeral 12 denotes a blade of the impeller 10, reference numeral 23 denotes a fluid inlet in the centrifugal pump 100, and reference numeral 25 denotes a fluid in the centrifugal pump 100. The reference numeral 24 denotes an outlet, the reference numeral 24 denotes a volute, and the reference numeral R denotes a rotation direction of the impeller 10.

  As shown in FIG. 2, the impeller 10 in this embodiment is a closed type, and includes a main plate 11, a blade 12, and a side plate 13 (not shown in FIG. 1).

  The main plate 11 is composed of a substantially disk-shaped disk arranged concentrically with the main shaft 17, and is formed to rotate in synchronization with the main shaft 17. The main plate 11 is also referred to as a rear shroud as described above. The main plate 11 is disposed so as to face a side plate 13 which will be described later, and a pressurizing passage 14 for fluid to be pumped is formed between the main plate 11 and the side plate 13.

The main plate 11 in the present embodiment partitions the inlet of the pressure increasing flow path 14 opening in the extending direction of the main shaft 17, that is, the fluid suction port 15 of the impeller 10 together with the main shaft 17 and the side plate 13, and opens in the centrifugal direction. The outlet of the pressure increasing flow path 14, that is, the fluid discharge port 16 of the impeller 10 is defined. The fluid discharge port 16 corresponds to a “fluid discharge port” in the claims.
The surface on the side plate 13 side of the main plate 11 of the present embodiment is a curved surface that gradually approaches the centrifugal direction of the impeller 10 as it goes rearward from the front suction port 15.

The side plate 13 is composed of a substantially annular member arranged concentrically with the main shaft 17, and is arranged concentrically with the main shaft 17 so as to face the main plate 11 as described above.
The opposing surface of the side plate 13 to the main plate 11 is a curved surface that gradually approaches the centrifugal direction of the impeller 10 toward the rear from the suction port 15 so as to correspond to the curved surface of the main plate 11.
As described above, the side plate 13 forms the fluid pressure increasing flow path 14 in the impeller 10 with the main plate 11. Further, as described above, the side plate 13 forms the fluid suction port 15 between the main shaft 17 and the main plate 11 on the front side of the impeller 10, and the fluid discharge port 16 between the main plate 11 on the outer peripheral side of the impeller 10. Is forming. As described above, the side plate 13 is also referred to as a front shroud, and sandwiches the blade 12 between the side plate 13 and the main plate 11.

As shown in FIG. 1, the blades 12 are formed of a plate body extending from the axial side toward the radially outer side, and a plurality of blades 12 are arranged at equal intervals in the circumferential direction.
The impeller 10 in this embodiment assumes that six blades 12 curved in the length direction are arranged in a spiral shape, but the number of blades 12 is not limited to this, It can be 5 sheets or less and 7 sheets or more. Incidentally, although the blade | wing 12 assumes what curves so that the middle may become convex toward the rotation direction of the impeller 10 shown by the arrow of the code | symbol R of FIG. 1, the blade | wing 12 which does not curve can also be used. .
The blades 12 form a pressure increasing flow path 14 by dividing the space between the main plate 11 (see FIG. 2) and the side plate 13 at equal intervals in the circumferential direction.

  The casing 20 rotatably supports the main shaft 17 via a plurality of bearings (not shown). A seal member (not shown) such as a mechanical seal is provided between the casing 20 and the main shaft 17 in order to prevent fluid leakage.

  The casing 20 is also formed with a supply path 21 for supplying fluid to the impeller 10 via the suction port 15 and the main flow path 22 for delivering the fluid discharged from the discharge port 16 of the impeller 10. . Incidentally, in the centrifugal pump 100 (vortex pump) in the present embodiment, the supply path 21 communicates with the inlet 23 (see FIG. 1) of the centrifugal pump 100. The main flow path 22 communicates with the outlet 25 (see FIG. 1) via the volute 24 of the centrifugal pump 100.

The casing 20 has a facing surface 20 a that faces the plate surface of the side plate 13 of the impeller 10. The facing surface 20a corresponds to a “first facing surface” in the claims.
The facing surface 20 a forms a first side chamber 30 between the opposing surface 20 a and the plate surface of the side plate 13 of the impeller 10. The first side chamber 30 corresponds to a “side chamber” in the claims.
The casing 20 forms a second side chamber 31 between the main plate 11 of the impeller 10 and the plate surface.

Further, the casing 20 has a facing surface 20 b that faces the outer peripheral end surface of the side plate 13 of the impeller 10. The facing surface 20b corresponds to a “second facing surface” in the claims.
The facing surface 20b forms a first gap S1 with the outer peripheral end surface of the side plate 13 of the impeller 10.
The first side chamber 30 communicates with the main flow path 22 through the first gap S1. The casing 20 has a cylindrical portion 36 that surrounds the suction port 15 around the main shaft 17 and that fits the front outer peripheral portion of the side plate 13 therein. The first side chamber 30 communicates with the supply path 21 via a second gap S <b> 2 formed between the front outer peripheral portion of the side plate 13 and the cylindrical portion 36 of the casing 20.

  The second side chamber 31 communicates with the main flow path 22 via a third gap S3 formed between the outer peripheral end surface of the main plate 11 of the impeller 10 and the casing 20.

And the centrifugal pump 100 of this embodiment has the groove part 33 in the opposing surface 20b of the casing 20 so that it may extend between the 1st side chamber 30 and the main flow path 22 as mentioned above. The groove part 33 in this embodiment is formed in the opposing surface 20b so that the extension direction of the main axis | shaft 17 may be followed.
In FIG. 2, the arrow indicated by reference numeral 34 a represents the flow of fluid from the supply passage 21 to the suction port 15, and the arrow indicated by reference numeral 34 b represents the flow of fluid from the boosting flow path 14 to the main flow path 22. The arrow indicated by reference numeral 34 c represents a “leakage flow” to be described later that flows through the first side chamber 30.

3 is a partial cross-sectional view taken along line III-III in FIG. In FIG. 3, the code | symbol 12 is the blade | wing of the impeller 10, the code | symbol 13 is a side plate, and the code | symbol 20 is a casing.
As shown in FIG. 3, the groove part 33 in the present embodiment has a rectangular shape in a sectional view, and the groove width is set longer than the depth of the groove part 33.
A plurality of groove portions 33 are formed at equal intervals along the circumferential direction of the facing surface 20b (second facing surface) of the casing 20 that is separated from the end surface of the outer peripheral portion of the side plate 13 via the first gap S1. In the present embodiment, it is assumed that the casing 20 has nine groove portions 33, but the present invention may be configured to have eight or less or ten or more groove portions 33.

  The centrifugal pump 100 as described above can be manufactured by assembling the impeller 10 to the casing 20 having the groove 33. At this time, for example, the groove 33 can be formed integrally with the casing 20 by casting or the like, or the groove 33 can be formed in a predetermined casing base by cutting or the like.

Next, the effect which the centrifugal pump 100 which concerns on this embodiment has is demonstrated mainly with reference to FIG.
In the centrifugal pump 100, when the impeller 10 is rotationally driven by a prime mover (not shown) through the main shaft 17, the fluid in the pressure increasing flow path 14 is pressurized by being given energy. The main flow path 22 is a static flow path and reduces the speed of the fluid applied by the impeller 10 to recover the pressure.

  Unlike the centrifugal pump 100 according to this embodiment shown in FIG. 2, the centrifugal pump (not shown) of Comparative Example 1 that does not have the groove 33 is assumed here. The centrifugal pump of Comparative Example 1 is configured in the same manner as the centrifugal pump 100 according to this embodiment except that the groove portion 33 is not provided. The centrifugal pump of Comparative Example 1 described below will be described with reference to FIG. 2 in which the groove 33 is not provided.

  In the centrifugal pump of the comparative example 1, the fluid sucked from the suction port 15 is discharged from the discharge port 16 to the main flow channel 22 through the boosting flow channel 14 by the impeller 10 that is driven to rotate. At this time, a part of the discharged fluid flows into the first side chamber 30 through the first gap S1 as a leakage flow 34c.

  Then, the leakage flow 34c is directed to the main shaft 17 side through the first side chamber 30, and then flows into the supply path 21 through the second gap S2, and is again sucked into the impeller 10 through the suction port 15. That is, the first gap S1, the first side chamber 30, and the second gap S2 form a fluid leakage path from the main path 22 to the supply path 21. In the centrifugal pump of Comparative Example 1 as described above, the fluid having a high swirling flow velocity in the vicinity of the discharge port 16 of the impeller 10 flows into the first side chamber 30 as described above. In the first side chamber 30, the swirling speed of the fluid (leakage flow 34c) is remarkably increased, and the pressure in the first side chamber 30 is decreased.

  On the other hand, in the centrifugal pump 100 according to the present embodiment, after the fluid having a large swirling flow velocity in the vicinity of the discharge port 16 flows into the first gap S1, a part of the fluid flows in the groove 33, and the other Some fluid flows across the groove 33. As a result, the groove 33 acts as a resistance against turning, so that the turning of the fluid flowing into the first gap S1 is suppressed. As a result, the turning speed of the fluid (leakage flow 34c) in the first side chamber 30 is reduced, and the pressure in the first side chamber 30 is increased.

Next, verification of the effect performed with respect to the centrifugal pump 100 of Example 1 and Comparative Example 1 will be described.
In this verification, in the axial direction of the first gap S1 shown in FIG. 2, the rotation speed of the leakage flow 34c from the inlet _{A IN} of the leak flow 34c to the outlet _{A OUT,} obtained by performing fluid analysis. The result is shown in FIG.
FIG. 4 shows the flow from the inlet A _IN (denoted as the gap inlet A _{IN in} FIG. 4) to the outlet A _OUT (denoted as the gap outlet A _{OUT in} FIG. 4) of the first gap S1 of the centrifugal pump 100 shown in FIG. It is a graph which shows the relationship between the position of an axial direction, and the turning speed (it describes in FIG. 4 as the turning speed) of the leakage flow 34c in 1st clearance gap S1.

In the fluid analysis, the pressure of the first side chamber 30 from the inlet B _IN to the outlet B _OUT of the leakage flow 34c was obtained in the radial direction of the first side chamber 30 shown in FIG. The result is shown in FIG.
Figure 5 (in FIG. 5, referred to as side chamber inlet _{B IN)} inlet _{B IN} of the first side chamber 30 of the centrifugal pump 100 shown in FIG. 2 in outlet _{B OUT} (FIG. 5 of the first side chamber 30 from side chamber outlet _{B OUT} It is a graph which shows the relationship between the position of the radial direction until it describes and the pressure of the 1st side chamber 30 (it is described as the pressure of a side chamber in FIG. 5).

As shown in FIG. 4, in the comparative example shown by the broken line 1 (no groove), the rotation speed of the leakage flow 34c from the inlet _{A IN} of the first gap S1 toward the outlet _{A OUT} of the first gap S1 is faster. Further, the turning speed tends to increase as it goes toward the first side chamber 30 (as it goes toward the outlet A _OUT ).
On the other hand, in Example 1 (with a groove) indicated by a solid line, the turning speed of the leakage flow 34c is slower than in Comparative Example 1 (without a groove). Specifically, the turning speed of Example 1 near the first side chamber 30 (near the outlet A _OUT ) is 65% or less of that of Comparative Example 1.

Further, as shown in FIG. 5, the pressure in the first side chamber 30 in Example 1 (with grooves) indicated by the solid line is larger than that in the first side chamber 30 from the inlet B _IN in comparison with Comparative Example 1 (without grooves). It has been verified that it increases over _OUT .
That is, the centrifugal pump 100 of the present embodiment increases the pressure of the first side chamber 30 by having the groove portion 33 on the inner wall surface of the casing 20 that forms the first gap S1, and the impeller 10 is on the suction port 15 side (front side). The axial thrust that is biased by is reduced.
According to the centrifugal pump 100 of this embodiment, the load on the thrust bearing can be reduced.

  Moreover, the centrifugal pump 100 of this embodiment can be manufactured by forming the groove part 33 with respect to the basic structure centrifugal pump (for example, the centrifugal pump of the comparative example 1). Therefore, the centrifugal pump 100 of this embodiment can be manufactured without adding a significant design change to the centrifugal pump having the basic structure.

  Moreover, since the groove part 33 of the centrifugal pump 100 is formed in the opposing surface 20b of the casing 20 so that the extension direction of the main axis | shaft 17 may be followed, unlike the radial groove | channel of the conventional centrifugal pump 100, a simple cutting tool is used. It can be easily formed. Therefore, according to the centrifugal pump 100 of this embodiment, a manufacturing process can be simplified and manufacturing cost can be reduced.

  Of the manufacturing methods of the centrifugal pump 100 described above, those in which the groove 33 is formed by additional machining can also be applied as a method for adjusting the axial thrust. In other words, the centrifugal pump 100 of the present embodiment has a structure capable of adjusting the axial thrust.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It can implement with a various form.
In the above embodiment, the spiral pump having the spiral volute (spiral casing) has been described. Next, the diffuser pump having the guide vanes will be described. Here, a multistage centrifugal diffuser pump will be described as an example. In the following other embodiments, the same components as those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

FIG. 6 is a partially enlarged longitudinal sectional view in which the vicinity of the impeller 10 of a centrifugal pump 100 (multistage centrifugal diffuser pump) according to another embodiment of the present invention is partially enlarged.
As shown in FIG. 6, the centrifugal pump 100 includes an outer casing (not shown) in which an inlet and an outlet for fluid are provided, and an inner casing 20 disposed inside the outer casing. The inner casing 20 corresponds to a “casing” in the claims. Hereinafter, the inner casing 20 is simply referred to as “casing 20”.

  The centrifugal pump 100 includes a main shaft 17 disposed so as to penetrate the casing 20 and a plurality of impellers 10 fixed to the main shaft 17. In FIG. 6, only a part of the impeller 10 is partially shown, and the impeller 10 in this embodiment is assumed to have about six stages, but is not limited to this. Absent.

The casing 20 is provided with an internal space that repeats the diameter reduction and the diameter expansion according to the arrangement of the impeller 10.
The casing 20 is formed with a communication path 40 that connects the discharge port 16 and the suction port 15 of the adjacent impeller 10. Incidentally, among the impellers 10 having a plurality of stages, the suction port 15 of the impeller 10 located on the most upstream side communicates with the fluid inlet (not shown) of the fluid in the centrifugal pump 100 and discharges the impeller 10 located on the most downstream side. The outlet 16 communicates with the fluid outlet (not shown) in the centrifugal pump 100.

  The communication path 40 includes a supply path 21 that introduces a fluid into the pressure increasing flow path 14 formed between the side plate 13 and the main plate 11 of the impeller 10, a diffuser flow path 41 into which the fluid is introduced from the pressure increasing flow path 14, It has a return channel 42 that allows fluid to flow from the diffuser channel 41 side to the supply channel 21 side, and a water return blade 50 provided in the return channel 42.

The supply path 21 is a flow path that changes the direction of the fluid in the axial direction immediately before the impeller 10 after flowing the fluid from the radially outer side toward the radially inner side.
The diffuser channel 41 communicates with the boost channel 14 on the radially inner side, and allows the fluid pressurized by the impeller 10 to flow outward in the radial direction. In the diffuser channel 41, a plurality of guide blades 43 are arranged at equal intervals in the circumferential direction around the main shaft 17. The guide vanes 43 are so-called diffuser vanes and constitute a diffuser. Incidentally, the inclination of the guide blades 43 arranged in the circumferential direction is opposite to the inclination of the blades 12 of the impeller 10 as described later (see FIG. 7).
One end side of the return channel 42 communicates with the diffuser channel 41, and the other end side communicates with the supply channel 21 via the water return blade 50.

The impeller 10 is of a closed type and includes a main plate 11, blades 12, and side plates 13.
The first side chamber 30 communicates with the main flow path 22 via a first gap S <b> 1 formed between the outer peripheral end surface of the side plate 13 of the impeller 10 and the casing 20. The first side chamber 30 communicates with the supply path 21 via a second gap S <b> 2 formed between the front outer peripheral portion of the side plate 13 and the cylindrical portion 36 of the casing 20.
As described above, the centrifugal pump 100 has the groove 33 on the facing surface 20b (second facing surface) of the casing 20 so as to extend between the first side chamber 30 and the main flow path 22.
The groove 33 is formed on the facing surface 20 b of the casing 20 so as to extend along the extending direction of the main shaft 17.
In FIG. 6, the arrow indicated by reference numeral 34 a represents the flow of fluid from the supply path 21 to the suction port 15, and the arrow indicated by reference numeral 34 c represents “leakage” described later flowing from the main flow path 22 to the first side chamber 30. "Flow".

7 is a partial sectional view taken along line VII-VII in FIG. In FIG. 7, reference numeral 12 denotes a blade of the impeller 10, reference numeral 13 denotes a side plate, reference numeral 20 denotes a casing, and reference numeral 43 denotes a guide blade.
As shown in FIG. 7, the groove part 33 in the present embodiment has a rectangular shape in a sectional view, and the groove width is set longer than the depth of the groove part 33.
A plurality of the groove portions 33 are formed at equal intervals along the circumferential direction of the inner peripheral surface of the casing 20 that is separated from the end surface of the outer peripheral portion of the side plate 13 via the first gap S1. In the present embodiment, it is assumed that the casing 20 has nine groove portions 33, but the present invention may be configured to have eight or less or ten or more groove portions 33.

In addition, regarding the relationship between the position of the guide blade 43 and the position of the groove portion 33, it is desirable that the groove portion 33 is formed so as to be close to the radially inner end 43 a of the guide blade 43.
In particular, it is desirable that the end portion 33a on the front side in the rotation direction R of the impeller 10 is formed so as to be close to the inner front end 43a of the guide blade 43 among both end portions in the circumferential direction of the groove portion 33.

The circumferential position of the front end portion 33a of the groove 33 is θ, where θ is the opening angle of the inner tip 43a of the guide vanes 43 adjacent to each other in the circumferential direction with the rotation center (not shown) of the impeller 10 as an axis. Is more preferably within a range of ± θ / 4 with respect to the position of the inner tip 43a of the guide vane 43. Further, a desirable position in the circumferential direction of the front end portion 33 a of the groove portion 33 is on a line connecting the rotation center of the impeller 10 and the inner front end 43 a of the guide blade 43.
Further, in the relationship between the positions of the guide blades 43 adjacent to each other in the circumferential direction and the circumferential width W of the groove 33, the width W of the groove 33 is preferably equal to or less than half of the angle θ (W ≦ θ / 2). .

  In such a centrifugal pump 100 (multistage centrifugal diffuser pump), the pressure of the fluid is increased stepwise by the impellers 10 (see FIG. 6) provided in multiple stages via the communication passage 40 and the water return blade 50 (see FIG. 6). The At this time, the centrifugal pump 100 has the groove portion 33 (see FIG. 7), thereby providing the same operational effects as the centrifugal pump 100 according to the above embodiment, and also having the guide blades 43 as follows. There are various effects.

As shown in FIG. 6, in this centrifugal pump 100, fluid is discharged from the pressure increasing flow path 14 of the rotating impeller 10 to the diffuser flow path 41 of the casing 20. Thereafter, when the operation is performed in the small flow rate region, the fluid collides with the guide vane 43, thereby causing a back flow of the fluid whose rotation is suppressed.
And this reverse flow with a slow turning speed forms the leak flow 34c with the flow which goes to the 1st clearance gap S1 from the main flow path 22. FIG. According to such a centrifugal pump 100, the swirling speed of the fluid (leakage flow 34 c) in the first side chamber 30 is efficiently reduced by causing the slow flow generated by the guide vanes 43 to flow into the groove 33. be able to.

  In addition, the centrifugal pump 100 causes the reverse flow generated by the guide vanes 43 and having a low turning speed to flow into the groove portion 33. Thereby, the centrifugal pump 100 can improve the axial thrust reduction effect in the operation in the small flow rate region where the backflow is generated, compared to the centrifugal pump 100 that does not have the guide vanes 43. Moreover, the centrifugal pump 100 suppresses the axial thrust reduction effect in the vicinity of the maximum efficiency point flow rate while ensuring a sufficient axial thrust reduction effect in the small flow rate region. According to such a centrifugal pump 100, the friction between the fluid in the first side chamber 30 and the impeller 10 in the vicinity of the maximum efficiency point flow rate can be reduced, so that a design that suppresses a decrease in pump efficiency due to a reduction in axial thrust is possible. Become.

Next, the effect | action performed with respect to Example 2 which is the centrifugal pump 100 (refer FIG. 6) which has the guide blade 43, and the comparative example 2 which assumed the structure similar to Example 2 except not having the groove part 33. FIG. Verification of the effect by fluid analysis will be described. For the centrifugal pump of Comparative Example 2, reference is made to FIG.
In this verification, in the axial direction of the first gap S1 shown in FIG. 6, to measure the turning speed of the leakage flow 34c from the inlet _{C IN} of the leak flow 34c to the outlet _{C OUT.} The result is shown in FIG.
8 shows an outlet C _OUT (in FIG. 8, a gap outlet C _OUT ) from an inlet C _IN (referred to as a gap inlet C _{IN in} FIG. 8) of the first gap S 1 of the centrifugal pump 100 shown in FIG. 6. It is a graph which shows the relationship between the position of the axial direction until it describes and the turning speed of the leakage flow 34c in 1st clearance gap S1 (it describes as turning speed in FIG. 8).

8, in Comparative Examples are shown by the broken line 2 (no groove), the turning speed of the leakage flow 34c from the inlet _{C IN} of the first gap S1 toward the outlet _{C OUT} of the first gap S1 is faster. Further, the turning speed tends to increase as it goes toward the first side chamber 30 (as it goes toward the outlet C _OUT ). That is, the leakage flow 34c whose turning speed is suppressed by the guide vanes 43 has a fast turn again while passing through the first gap S1.
On the other hand, in Example 2 (with a groove) indicated by a solid line, it was verified that the leakage flow 34c reached the outlet C _OUT while the swirling speed of the leakage flow 34c was lower than that in the comparative example 2 (without a groove).

  In the above-described embodiment, the centrifugal pump 100 in which the groove portion 33 extends along the axial direction has been described. However, the present invention has a configuration in which the groove portion 33 extends so as to be inclined with respect to the axial direction. You can also.

FIG. 9 is an explanatory diagram of the configuration of the centrifugal pump 100 in which the groove 33 is inclined. 9 is a partial cross-sectional view corresponding to the IX-IX cross section of FIG.
In FIG. 9, reference numeral 20 denotes a casing, reference numeral 33 denotes a groove, and reference numeral R denotes a rotation direction of the impeller 10.
As shown in FIG. 9, the centrifugal pump 100 is configured such that the extending direction of the groove 33 is inclined with respect to the axial direction (not shown) of the centrifugal pump 100, so that the groove 33 has a rotational direction R of the impeller 10. The extending direction is inclined. More specifically, the groove 33 is formed such that the extending direction of the groove 33 forms an acute angle with respect to the rotation direction R of the impeller 10.

  According to the centrifugal pump 100 as described above, the leakage flow with small swirl can be efficiently introduced into the first side chamber 30 (see FIG. 6) through the groove 33, so that the axial thrust reduction effect is more remarkable. Appear in

9 is inclined such that the extending direction of the groove 33 forms an acute angle with respect to the rotation direction R of the impeller 10, but the groove 33 may be inclined so as to form an obtuse angle. .
According to the groove portion 33 inclined at such an obtuse angle, the angle formed by the vector direction of the leakage flow and the extending direction of the groove portion 33 is closer to a right angle than that forming an acute angle. The turning speed possessed can be further reduced. Thereby, the centrifugal pump 100 can further reduce the axial thrust.

  Moreover, although the cross-sectional shape of the groove part 33 demonstrated the rectangular pump 100 in the said embodiment, the cross-sectional shape of the groove part 33 may be made into polygonal shapes other than a rectangle, or circular arc shape, such as a semicircle or a semi-ellipse. it can.

10 and 11 are explanatory views showing a modification of the groove 33, and are partial cross-sectional views corresponding to the VII-VII cross section of FIG.
10 and 11, reference numeral 20 is a casing, reference numeral 33 is a groove, reference numeral 12 is a blade of the impeller 10, reference numeral 13 is a side plate of the impeller 10, and reference numeral 43 is a guide blade.

The cross-sectional shape of the groove part 33 in the centrifugal pump 100 shown in FIG. 10 has a triangular shape, and the cross-sectional shape of the groove part 33 in the centrifugal pump 100 shown in FIG. 11 has a semicircular shape.
According to the centrifugal pump 100 having such a groove portion 33, the groove portion 33 can be easily formed by cutting the casing base (not shown) with a simple cutting tool. Incidentally, examples of the cutting tool include a file and a drill.

FIG. 12 is a configuration explanatory view showing another modified example of the groove portion 33, and corresponds to a partially enlarged sectional view in the vicinity of the groove in the centrifugal pump of FIG. 13 is a partial sectional view taken along line XIII-XIII in FIG.
As shown in FIG.12 and FIG.13, the casing 20 (refer FIG. 12) has the groove part formation member 38 in which the groove part 33 was formed. The groove forming member 38 is fitted into the casing 20. In FIG. 12, reference numeral 30 denotes a first side chamber. 12 and 13, reference numeral 12 denotes a blade of the impeller 10, reference numeral 13 denotes a side plate of the impeller 10, and reference numeral 43 denotes a guide blade.

  More specifically, as shown in FIG. 12, the casing 20 includes a casing body 20c, a ring member 20d disposed so as to surround the outer peripheral end of the side plate 13 of the impeller 10 with a first gap S1, and It is comprised.

  And the groove part formation member 38 is engage | inserted and arrange | positioned at the inner peripheral side of the ring member 20d. The groove forming member 38 is formed in an L shape in a sectional view so as to prevent the ring member 20d from coming off.

  As shown in FIG. 13, a plurality of the groove forming members 38 are arranged along the circumferential direction on the inner peripheral side of the casing 20, and the groove forming members 38 having the grooves 33 are fitted into each other independently.

FIG. 14 is a configuration explanatory view showing a further modification of the groove 33, and corresponds to FIG.
As shown in FIG. 14, the groove 33 is formed in the groove part forming member 39. Unlike the groove forming member 38 formed separately for each of the plurality of grooves 33 shown in FIG. 13, the groove forming member 39 exhibits an integral ring shape along the circumferential direction on the inner peripheral side of the casing 20. Yes. Each groove 33 is formed at a predetermined position on the inner circumferential side of the groove forming member 39. Incidentally, although not shown, the groove forming member 39 is fitted and arranged on the inner peripheral side of the ring member 20d in the same manner as the groove forming member 38 shown in FIG. Further, the groove forming member 39 is formed in an L shape in sectional view so as to prevent the ring member 20d from coming off.

  In the centrifugal pump 100 having the groove 33 in the groove forming members 38 and 39, for example, a solid such as sand is contained in the fluid to be pumped, and the groove 33 is formed when the groove 33 is worn by the solid. The members 38 and 39 can be replaced.

DESCRIPTION OF SYMBOLS 10 Impeller 11 Main plate 11a Step part 12 Blade 13 Side plate 14 Boosting flow path 15 Suction port 16 Discharge port (fluid discharge port)
17 Spindle 20 Inner casing (casing)
20a 1st opposing surface 20b 2nd opposing surface 21 Supply path 22 Main flow path 24 Volute 30 1st side chamber (side chamber)
31 Second side chamber 33 Groove portion 33a End portion 38 Groove portion forming member 39 Groove portion forming member 40 Communication passage 41 Diffuser flow passage 42 Return flow passage 43 Guide vane 43a Inner tip 50 Water return vane 100 Centrifugal pump S1 First gap S2 Second gap S3 3rd gap

Claims (6)

An impeller having a fluid pressure increasing channel between the main plate and the side plate;
A casing that houses the impeller inside;
A main flow path of fluid formed in the casing so that the fluid discharge port of the boost flow path faces the outer periphery of the impeller;
A centrifugal pump having
A side chamber formed between the plate surface of the side plate and the first facing surface of the casing facing the plate surface;
Formed between the outer peripheral end surface of the side plate and the second opposing surface of the casing facing so as to surround the outer peripheral end surface over the entire circumference, and a gap communicating the side chamber and the main flow path;
With
A centrifugal pump, wherein a groove portion is formed on a second facing surface of the casing forming the gap so as to extend between the side chamber and the main flow path. The centrifugal pump according to claim 1,
A plurality of the groove portions are formed at equal intervals along the circumferential direction of the second facing surface. The centrifugal pump according to claim 2,
A centrifugal pump comprising a diffuser having a plurality of guide vanes on an outer side in the radial direction of the impeller, wherein the groove is formed so as to be close to an inner end in the radial direction of the guide vanes. The centrifugal pump according to claim 1,
The centrifugal pump is characterized in that the groove portion is formed so as to be inclined with respect to the rotation direction of the impeller in a plan view seen from the radially outer side to the radially inner side. The centrifugal pump according to claim 1,
The cross-sectional shape of the groove is a polygonal shape or a circular arc shape. The centrifugal pump according to claim 1,
The centrifugal pump is characterized in that the groove is formed by fitting a groove forming member separate from the casing into the casing.

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