JP2015010566A - Centrifugal pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize at least one of providing a centrifugal pump realizing its capability more stably, preferably a centrifugal pump for restricting a reduction in capability of the pump, and restricting the amount of gas dissolved in liquid.SOLUTION: This invention relates to a centrifugal pump 1 comprising a suction port 13 for sucking fluid; an impeller 5 having a plurality of vanes 51 at least on the side of the suction port 13, sucking fluid through the suction port 13 through the rotation around a prescribed shaft 3 passing through the suction port 13 and discharging the fluid in a direction crossing at a right angle with the shaft 3; a pump head 6 having the suction port 13 and storing the impeller 5; the first opening part 10 opened at the location of the pump head 6 oppositely facing against the plurality of vanes 51 at the side of the suction port 13; the second opening part 11 opened at a location of the pump head 6 present in at least one of a direction crossing at a right angle with the shaft 3 and a direction opposite to the side of the suction port 13; and a passage 12 connecting the first opening part 10 with the second opening part 11.

Description

  The present invention relates to a centrifugal pump.

  Generally, a centrifugal pump is used to circulate a liquid such as a coolant liquid necessary for cooling a machine tool. The centrifugal pump sucks liquid by a differential pressure between the inside and outside of the pump generated by rotation of the impeller, and discharges the liquid by applying centrifugal force to the liquid by rotation of the impeller. That is, the centrifugal pump enables suction and discharge of liquid by the rotation of the impeller and the centrifugal force generated by the rotation.

  However, in the centrifugal pump, when a gas is mixed into the liquid, the liquid moves to the outside of the impeller inside, and centrifugal separation in which the gas stays at the center of the impeller occurs. Therefore, in the centrifugal pump, if gas continues to be mixed into the liquid, the gas staying in the center grows as the operation time elapses due to the influence of centrifugal separation, and the grown gas closes the suction port and near the center of the impeller. As a result, the capacity of the pump is reduced.

  As a method for solving this problem, it is known that a through hole is formed in the central portion of the impeller, gas is retained on the back side of the impeller, and discharged by a vacuum device. In addition, in the tank type solid centrifugal pump, there is known a method of discharging gas to the outside of the pump chamber by setting the gas staying portion to a positive pressure as a two-stage impeller structure equipped with an impeller that pressurizes the pump suction port. It has been. However, these methods necessitate the addition of new devices or parts, leading to an increase in cost.

  On the other hand, in recent years, the machine tool industry has tended to reduce the amount of coolant used for the purpose of environmental consideration and cost reduction, and the capacity of a tank in which a centrifugal pump is installed is becoming smaller. Therefore, the number of circulations of the coolant liquid increases in the tank, the gas generated by the circulation of the coolant liquid increases, and the gas sucked into the centrifugal pump increases. As a result, many bubbles stay inside the centrifugal pump, and as described above, it is more important to discharge the gas staying at the center of the impeller to the outside of the pump chamber.

  Environmental considerations and cost reductions are common objectives not only in the machine tool industry, but in all industries. Especially, machine tools need cooling with coolant liquid, and the pump's ability by the retention of gas inside the pump. It is necessary to suppress the decrease.

  As a method for solving this problem, Patent Document 1 includes an impeller, an inner region of a pump chamber formed by a suction sleeve that covers the periphery of the impeller, and an exhaust pipe that leads from the inner region to the outside on the suction port side. And a centrifugal pump with a suction sleeve. According to the centrifugal pump, it is described that the gas in the gas and liquid sucked from the suction port can be discharged from the inner region to the outside by the exhaust pipe provided in the suction sleeve.

German Patent Application No. 4325549

  With the centrifugal pump described in Patent Document 1, it is possible to discharge gas from the internal region of the pump to the outside without incurring an increase in cost, and to suppress a decrease in pump capacity. However, since the discharge port of the discharge pipe is only on the suction port side, a large amount of discharged gas is caught in the suction of the pump and flows into the internal region again. As a result, since the gas accumulates in the internal region of the pump, the frequency of occurrence of poor suction increases. That is, the pump often does not exhibit its capacity stably. In the recent machine tool industry, a centrifugal pump that suppresses a decrease in capacity is desired, but a centrifugal pump that exhibits its capacity more stably is strongly desired. In addition, depending on the type of liquid handled by the centrifugal pump, it may be necessary to suppress the amount of gas (for example, oxygen) dissolved in the liquid.

  Therefore, the present invention provides a centrifugal pump that exhibits its ability more stably, and preferably provides a centrifugal pump that suppresses a reduction in pump capacity, and suppresses the amount of gas dissolved in the liquid. The purpose is to realize at least one of the above.

  In order to solve the above-described problems and achieve the object, the centrifugal pump of the present invention has a suction port for sucking fluid, a plurality of blades at least on the suction port side, and a predetermined axis passing through the suction port. An impeller that sucks fluid from the suction port by rotating as a center and discharges the fluid in a direction orthogonal to the axis; a pump head that has the suction port and houses the impeller; and a plurality of blades on the suction port side; A first opening that opens to a portion of the opposing pump head, a second opening that opens to a portion of the pump head that exists in at least one of a direction orthogonal to the axis and a direction opposite to the suction port side, and a first opening And a passage connecting the part and the second opening.

  The centrifugal pump of the present invention has a suction port for sucking fluid, a plurality of blades at least on the suction port side, and sucks fluid from the suction port by rotating around a predetermined axis passing through the suction port. An impeller that discharges fluid in a direction perpendicular to the axis; a pump head that has a suction port and that houses the impeller; and a first opening that opens at a portion of the pump head that faces the plurality of blades on the suction port side And a second opening that opens to a portion of the pump head that exists in a direction perpendicular to the axis, and a passage that connects the first opening and the second opening.

  The number of passages is preferably 2 or more and 10 or less.

  When the diameter of the circle connecting the inner diameter side ends of the impeller blades is Ds and the diameter of the impeller is D, the first opening is 1.0 · Ds to 1.0 · D around the axis. It is preferable to open in the range.

  The passage has a circular cross section perpendicular to the extending direction, and the diameter of the cross section is preferably 10% or more and 50% or less with respect to the diameter of the discharge port from which the fluid is discharged.

  The centrifugal pump of the present invention exerts its ability more stably, and preferably achieves at least one of suppressing the reduction in pump capacity and suppressing the amount of gas dissolved in the liquid. be able to.

FIG. 1 is an external view including a partial cross section of a centrifugal pump according to an embodiment of the present invention. FIG. 2 is a plan view of the impeller shown from the suction surface side according to the embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a pump head portion according to the embodiment of the present invention. FIG. 4 is a plan view of the suction cover according to the embodiment of the present invention. FIG. 5 is a plan view seen from the convex portion side showing the area of the suction cover with respect to the diameter of the impeller according to the embodiment of the present invention. FIG. 6 is a cross-sectional view schematically showing a first modification of the pump head unit according to the embodiment of the present invention. FIG. 7 is a cross-sectional view schematically showing a second modification of the pump head unit according to the embodiment of the present invention. FIG. 8 is a cross-sectional view schematically showing a third modification of the pump head portion according to the embodiment of the present invention. FIG. 9 is a cross-sectional view schematically showing a fourth modification of the pump head portion according to the embodiment of the present invention. FIG. 10 is an external view showing a test facility for the centrifugal pump according to the embodiment of the present invention. FIG. 11 is a chart showing the results of the first performance test of the centrifugal pump according to the embodiment of the present invention. FIG. 12 is a cross-sectional view showing an outline of a pump head portion applied to the second performance test of the centrifugal pump according to the embodiment of the present invention. FIG. 13 is a chart showing the results of the second performance test of the centrifugal pump according to the embodiment of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

  FIG. 1 is an external view including a partial cross section of a centrifugal pump according to an embodiment of the present invention. FIG. 2 is a plan view of the impeller according to the embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a pump head portion according to the embodiment of the present invention. FIG. 4 is a plan view of the suction cover according to the embodiment of the present invention. FIG. 5 is a plan view seen from the convex portion side showing the area of the suction cover with respect to the diameter of the impeller according to the embodiment of the present invention. In the present embodiment, an electric motor is described as an example of the prime mover of the centrifugal pump 1, but the prime mover of the centrifugal pump is not limited to this. For example, the centrifugal pump can be applied with an engine as a prime mover.

  The centrifugal pump 1 includes an electric motor 2, a shaft 3 connected to the electric motor 2, an impeller 5 connected to an end 3 c of the shaft 3, and a pump head 6 that houses the impeller 5. The centrifugal pump 1 includes a protective cover 4 that is disposed on the outer periphery of the shaft 3, protects the shaft 3, is connected to the protective cover 4 and the electric motor 2, and has a support member 15 that supports the electric motor 2. The protective cover 4 is connected to the support member 15 and the pump head 6. The pump head 6 has a casing 60 and a suction cover 61, and is formed with a suction port 13 for sucking fluid and a discharge port 14 for discharging fluid. The casing 60 and the suction cover 61 are fixed with bolts 19b and nuts 20b. In the pump head 6, the first opening 10 is formed in a portion 65 </ b> A of the suction cover 61. In the pump head 6, the second opening 11 is formed in a portion 65 </ b> B of the suction cover 61. A passage 12 connecting the first opening 10 and the second opening 11 is formed in the suction cover 61 of the pump head 6. An L-shaped pipe 16 is connected to the discharge port 14 toward the drive side of the pump. A pipe 17 and a connection member 18 are connected to the L-shaped pipe 16.

  The centrifugal pump 1 has a center line in which the motor 2 is driven by power supplied from the outside to rotate the shaft 3, and the impeller 5 fixed to the end 3 c of the shaft 3 is a predetermined shaft passing through the suction port 13. By rotating around CL, fluid is sucked and discharged in a direction perpendicular to the center line CL.

  The electric motor 2 is a prime mover (drive source) that rotates the shaft 3. In the electric motor 2, a flange 2 a is provided on the support member 15 (the suction port 13 side of the centrifugal pump 1). The flange 2a is fixed to the support member 15 with bolts 19a and nuts 20a.

  The shaft 3 includes a metal round bar main body 3b extending from the electric motor 2 toward the pump head 6 and an end 3c fixed to one end of the main body 3b. The main body 3 b is connected to the electric motor 2 and is protected by a protective cover 4. A key 3e is attached to the end portion 3c, and a screw portion 3d is formed in front of the end portion 3c. The protective cover 4 is fixed to the support member 15 by welding, for example, and supports the support member 15.

  The impeller 5 has a plurality of blades and has a diameter D. Specifically, the impeller 5 has a disk 50 and a plurality of blades 51 as shown in FIG. In the impeller 5, six blades 51 are integrally formed on a resin disk 50 having a diameter D. Although not shown, six blades are similarly integrally formed on the back side of the disk 50. A boss portion 52 is formed at the center portion 50 a of the disk 50. The boss portion 52 is formed with a through hole 50c including a key groove 50b. As shown in FIG. 1, the impeller 5 is fixed to the end portion 3 c of the shaft 3 by fitting the key 3 e in the key groove 50 b and screwing the impeller nut 21 into the screw portion 3 d of the shaft 3.

  The impeller 5 is a central region CP between the boss portion 52 and a circumference 53 having a diameter Ds connecting the end portions on the inner diameter side of the blades 51 of the impeller 5. In the impeller 5, six blades 51 are arranged on the radially outer side of the central region CP. The blades 51 are curved in the counter-rotating direction of the impeller 5 from the circumference 53 toward the outer edge 50 d of the disk 50, and are arranged at equal intervals in the circumferential direction of the disk 50. The disk 50 is not limited to resin, but may be made of metal such as stainless steel. Here, the impeller 5 does not need to integrally mold the disk 50 and the blades 51. For example, the impeller 5 can be formed by attaching blades 51 on the disk 50.

  As shown in FIG. 3, the pump head 6 has a cylindrical shape, has a through hole 3 a centered on the center line CL, and a suction port 13, and houses the impeller 5. The pump head 6 includes a cylindrical casing 60, a flange-shaped suction cover 61, and a bolt 19 b and a nut 20 b that fix the casing 60 and the suction cover 61.

  The casing 60 has a first end surface 7 a that is an end surface 7 in the direction of the central axis CL of the pump head 6 (a surface that is an end in the direction of the central axis CL) 7. The casing 60 has a through hole 3a centered on the center line CL from the first end surface 7a toward the recess 62a. The shaft 3 is inserted into the through hole 3a.

  The casing 60 has a through hole 3a, a recess 62, and a recess 62a with the center line CL as the center. The recess 62 is formed on the surface on the suction cover 61 side (surface on the suction port 13 side) so as to protrude toward the through hole 3a. The recess 62 is formed by an inner surface 60d that intersects the plane 61d and is parallel to the center line CL, and an inner surface 60c that is perpendicular to the center line CL. The depth of the recess 62 from the surface on the suction cover 61 side (surface on the suction port 13 side) to the inner surface 60c is dp. The recess 62 is formed on the through hole 3a side of the recess 62, that is, on the inner surface 60c. The recess 62a is formed by an inner surface 60b parallel to the center line CL and an inner surface 60a perpendicular to the center line CL. In the recess 62a, the distance between the inner surfaces 60b is shorter than the distance between the inner surfaces 60a in the cross section passing through the central axis CL.

  The casing 60 is formed with a first side surface 8 a that becomes a side surface (an end surface in a direction orthogonal to the central axis CL of the pump head 6) 8 of the pump head 6. The casing 60 has a discharge port 14 that opens from the first side surface 8a to the inner surface 60b of the recess 62a. As for the discharge port 14, the diameter of the edge part by the side of the inner surface 60a becomes D3. That is, the diameter of the opening at the position where the discharge port 14 and the space inside the recess 62a are connected is D3. The casing 60 is recessed at the discharge port 14 from the first side surface 8a toward the recess 62, and a counterbore portion 14b to which a pipe is connected is formed. The counterbore 14b is provided to facilitate the insertion of the pipe, but is not limited thereto. For example, as long as piping can be connected to the discharge port 14, the counterbore part 14b does not need to be provided.

  As shown in FIG. 3, the suction cover 61 includes a plane 60e perpendicular to the center line CL, a second side surface 8b parallel to the center line CL and serving as the side surface 8 of the pump head 6, and the center line CL. A curved surface portion 64 that is vertical and includes a second end surface 7 b that becomes the end surface 7 of the pump head 6 is formed. Further, the suction cover 61 is formed of a curved surface 61 c parallel to the center line CL and a flat surface 61 a perpendicular to the center line CL, and a convex portion 63 having a height H protruding from the curved surface portion 64 toward the casing 61. Is provided. The suction cover 61 is formed with a through hole that penetrates from the second end surface 7b toward the flat surface 61a and becomes the suction port 13 with the center line CL as the center.

  In the pump head 6, the first opening 10 is opened at a portion 65 </ b> A that is on the suction port 13 side of the suction cover 61 and faces the plurality of blades 51 of the impeller 5. The first opening 10 is on the suction port 13 side of the suction cover 61 and opens to a plane 61 a that faces the plurality of blades 51 of the impeller 5 having a diameter D.

  Further, the pump head 6 has the second opening 11 opened in a portion 65B existing in a direction orthogonal to the center line CL. Specifically, the second opening 11 is opened in the second side surface 8b in a direction orthogonal to the center line CL. That is, in the present embodiment, the second side surface 8b corresponds to a portion 65B of the pump head 6 that exists in a direction orthogonal to the center line CL. The center C1 of the first opening 10 is formed on the circumference of the diameter D1 with the center line CL as the center. The first opening 10 is opened near the center region CP of the impeller 5. The second opening 11 opens in a direction orthogonal to the center line CL. The center C2 of the second opening 11 is formed at a distance R from the second end surface 7b. In addition, a screw portion 31 is formed in the second opening portion 11.

  The suction cover 61 has an exhaust hole 12a and an exhaust hole 12b. The exhaust hole 12a and the exhaust hole 12b have a circular cross section perpendicular to the extending direction. The suction cover 61 forms a passage 12 by connecting the exhaust hole 12a and the exhaust hole 12b. The exhaust hole 12a is a hole having a length L1 and a diameter d1 extending from the first opening 10 toward the second end face 7b. The exhaust hole 12b is a hole having a length L2 and a diameter d1 extending from the second opening 11 toward the suction port 13. An end of the exhaust hole 12a opposite to the first opening 10 and an end of the exhaust hole 12b opposite to the second opening 11 are connected within the suction cover 61 at an angle α1. Thereby, the exhaust hole 12a and the exhaust hole 12b become the connected channel | path 12, and the 1st opening part 10 exposed to the recessed part 62a and the 2nd opening part 11 exposed to the side surface 8b are connected. The length L1 of the exhaust hole 12a is shorter than the length LH from the flat surface 61a to the second end surface 7b, and the length L2 of the exhaust hole 12b is shorter than the length LW from the second side surface 8b to the inner surface 61b. In the present embodiment, the diameter d1 of the exhaust hole 12a and the exhaust hole 12b is the same size, but is not limited to this, and may be different diameters. Furthermore, the angle α1 is connected at 90 °, but is not limited thereto, and may be an acute angle or an obtuse angle, for example.

  As shown in FIG. 4, the suction cover 61 is formed with eight through holes 22 and suction ports 13 for the bolts 19b to pass therethrough. Furthermore, the first opening 10, the second opening 11, the exhaust holes 12a, and the exhaust holes 12b are each formed in four and at intervals of an angle α2. Here, the angle α2 is a center angle with respect to the center line CL1, and is an angle formed by the adjacent exhaust holes 12b. In the present embodiment, the angle α2 is 90 °, but is not limited thereto. For example, the number of the first openings 10, the second openings 11, the exhaust holes 12a, and the exhaust holes 12b may be one to three. Furthermore, the first opening 10, the second opening 11, the exhaust holes 12a, and the exhaust holes 12b are five or more, and the angle α2 can be formed at 60 ° or 30 °.

  As shown in FIG. 3, the pump head 6 is formed by inserting the convex portion 63 of the suction cover 61 into the concave portion 62 of the casing 60. Specifically, the concave portion 62 and the convex portion 63 are in contact with the inner surface 60d of the concave portion 62 and the curved surface 61c of the convex portion 63, and the flat surface 61d of the concave portion 62 and the flat surface 60e of the curved surface portion 64 are in contact with each other. The height H of the convex portion 63 of the suction cover 61 is formed to be lower than the depth dp of the concave portion 62 of the casing 60. Accordingly, when the pump head 6 is formed by inserting the convex portion 63 of the suction cover 61 into the concave portion 62 of the casing 60, the pump chamber 9 which is an internal space is formed.

  The pump chamber 9 is formed by a suction port 13, a region 9 a and a discharge port 14. The region 9a is a space surrounded by the inner surface 60a, the inner surface 60b, the inner surface 60c and the inner surface 60d of the casing 60, and the flat surface 61a of the convex portion 63 of the suction cover. In the region 9 a, a part of the flat surface 61 a is connected to the suction port 13, and a part of the inner surface 60 d is connected to the discharge port 14. That is, the pump chamber 9 is a region from the suction port 13 to the discharge port 14 via the region 9a. As shown in FIG. 1, the fluid discharged from the discharge port 14 passes through an L-shaped pipe 16, a pipe 17 connected to the L-shaped pipe 16, and a connecting member 18 connected via a support member 15. It passes through and is discharged outside. In addition, although the pump chamber 9 is an internal area | region which combined the casing 60 and the suction cover 61, it is not restricted to this. For example, even if the pump head 6 is a single processed product or a molded product, the pump chamber 9 only needs to have a region serving as a flow path.

  The centrifugal pump 1 is based on the principle that the impeller 5 is rotated to generate a negative pressure at the inlet portion of the impeller 5 to suck fluid from the suction port 13. The centrifugal pump 1 requires a passage 12 connected to the pressure side lower than the pressure in the central region CP of the impeller 5 in order to discharge the gas accumulated in the inner region to the outside of the pump chamber 9. For example, in the centrifugal pump 1 immersed in the water tank, there is no place where a pressure lower than the pressure generated in the central region CP of the impeller 5 is generated when the pump alone is used, and it cannot be generated. Therefore, since the blade 51 portion of the impeller 5 has a pressurizing action, the pump chamber 9 exits from the pump chamber 9 to the portion 65A of the pump head 6 that is close to the central region CP of the impeller 5 and faces the blade 51 of the impeller 5. The passage 12 leading to is opened. Therefore, the gas can be discharged to the outside of the pump chamber 9 by the differential pressure between the central region CP of the impeller 5 and the outside of the pump chamber 9. And by providing the 2nd opening part 11 to the site | part 65B of the pump head 6 which exists in the direction orthogonal to the centerline CL, the discharged | emitted gas turns into the fragmented bubble by the pressurization effect | action of the impeller 5. To float the fluid in the tank. And it can suppress that a bubble enters through the suction inlet 13 again. That is, when the gas accumulated in the central region CP is discharged as bubbles only on the suction port 13 side, many bubbles are sucked from the suction port 13. The sucked bubbles are discharged again into the water tank. That is, the bubbles circulate in the water tank and the pump. In the present embodiment, many bubbles are discharged in a direction perpendicular to the center line CL and float in the water tank. Therefore, the centrifugal pump 1 can suppress the bubbles from entering through the suction port 13 again. As a result, since the amount of gas accumulated in the central region CP is reduced, the centrifugal pump 1 can suppress the occurrence of defective suction and defective discharge, and can stably exhibit its ability. Furthermore, the centrifugal pump 1 can suppress a decrease in capacity because the amount of gas accumulated in the central region CP decreases.

  When the bubbles and the liquid come into contact, the gas forming the bubbles may be dissolved in the liquid. In this case, the amount of gas dissolved in the liquid increases as the time for which the bubbles stay in the liquid is longer. In the present embodiment, the distance at which the bubbles are discharged in the direction perpendicular to the center line CL and rise to the water surface in the water tank is shorter than the distance from which the bubbles are discharged from the suction port 13 side and rise to the water surface in the water tank. Therefore, the bubbles stay in the liquid for a shorter time than when the bubbles are discharged only from the suction port 13 side. As a result, the centrifugal pump 1 can suppress the amount of gas dissolved in the liquid.

  The number of passages 12 is preferably 2 or more and 10 or less. Here, the number of passages 12 means the number of paths for discharging bubbles. By setting the number of the passages 12 to be equal to or more than two, the bubbles can be discharged in a well-balanced manner if they are equally arranged with respect to the center line CL. On the other hand, by setting the number of passages 12 to 10 or less, efficient exhaust can be performed without discharging an amount of liquid that causes a reduction in pump performance. More preferably, the number of the passages 12 is 4 or more and 8 or less.

  When the diameter of the impeller 5 at the beginning of the blade 51 (a circle connecting the ends on the center line CL side) is Ds and the diameter of the impeller 5 is D, the first opening 10 is 1. It is preferable to open in the range S of 0 · Ds or more and 1.0 · D or less. That is, the first opening 10 is formed in a range S surrounded by a circle having a diameter of 1.0 · Ds centered on the center line CL and a circle of 1.0 · D centered on the center line CL. It is preferable. Here, as shown in FIG. 5, the range S indicates a portion surrounded by a dotted line P2 indicating 1.0 · Ds and a dotted line P1 indicating 1.0 · D in the suction cover 61, and the dotted lines P1, P2 including.

  Centrifugal pump 1 pressurizes impeller 5 with gas in central region CP by opening first opening 10 outside (including the boundary) a circle having a diameter of 1.0 · Ds centered on centerline CL. It can be discharged from the first opening 10 by the action. On the other hand, the centrifugal pump 1 forms the first opening 10 inside the circle (including the boundary) having a diameter of 1.0 · D with the center line CL as the center, so that the first pressure due to the impeller 5 is pressurized. The outflow of the liquid from the opening part 10 can be suppressed, and the capability fall of a pump can be suppressed.

  In addition, it is more preferable that the first opening 10 opens outside a small circle out of a circle having a diameter of 1.05 · Ds and a circle having a diameter of 1.0 · Ds + 7 mm centered on the center line CL. Here, 1.0 · Ds + 7 mm means the length LW and the length L2 shown in FIG. 3 in addition to the diameter Ds of the beginning of the blade 51 of the impeller 5 (a circle connecting the ends on the center line CL side). This is a value in consideration of the minimum wall thickness, which is the difference between the two, and the minimum diameter of the passage 12. The minimum wall thickness is 1 mm (2 mm in diameter), and the minimum diameter of the passage is preferably 5 mm. If the first opening 10 is outside of a circle having a diameter of 1.05 · Ds or outside of a circle having a diameter of 1.0 · Ds + 7 mm, the minimum thickness can be secured, so that the processing of the first opening 10 is easy. Become. On the other hand, the first opening 10 is more preferably opened inside a circle having a diameter (D−Ds) / 2 + Ds. Here, the circle of diameter (D−Ds) / 2 + Ds is a circle passing through the center of the range S. If the first opening 10 is inside a circle having a diameter (D−Ds) / 2 + Ds, it is advantageous to discharge bubbles by pressurizing the impeller 5.

  The diameter d1 of the passage 12 is preferably 10% or more and 50% or less with respect to the diameter D3 of the discharge port 14. By setting the diameter d1 to 10% or more with respect to the diameter D3 of the discharge port 14, it is possible to discharge bubbles that are substantially equivalent to the gas that is continuously sucked. On the other hand, by setting the diameter d1 to 50% or less with respect to the diameter D3 of the discharge port 14, it is possible to suppress the discharge to the liquid transferred to the discharge port 14. Specifically, the diameter d1 is preferably 5 mm or more and 20 mm or less. More preferably, they are 8 mm or more and 12 mm or less.

  FIG. 6 is a cross-sectional view schematically showing a first modification of the pump head unit according to the embodiment of the present invention. The first modified example is the same as the above-described embodiment, but the second opening 11 is opened to the part 65B of the pump head 6A, and the second discharge port 70 is also opened to the part 65C of the pump head 6A. Is different. In the description of the first modification, the description of the same configuration as that of the above-described embodiment will be omitted in principle, and the description will focus on the different configuration.

  The pump head 6 </ b> A has the first opening 10 at a portion 65 </ b> A on the suction port 13 side of the suction cover 61 and facing the plurality of blades 51 of the impeller 5. The first opening 10 is on the suction port 13 side of the suction cover 61 and opens on a flat surface 61 a that faces the plurality of blades 51 of the impeller 5.

  Further, in the pump head 6A, the second opening 11 is opened in a portion 65B existing in a direction orthogonal to the center line CL. Specifically, the second opening 11 is opened in the second side surface 8b in a direction orthogonal to the center line CL. Further, the pump head 6 </ b> A has a second discharge port 70 opened at a portion 65 </ b> C of the suction cover 61. That is, in the present modification, the second side surface 8b corresponds to the portion 65B of the pump head 6A that exists in the direction orthogonal to the center line CL. The second end surface 7b corresponds to the portion 65C of the pump head 6A.

  The center C1 of the first opening 10 is formed on the circumference of the diameter D1 with the center line CL as the center. The first opening 10 is opened near the center region CP of the impeller 5. The second opening 11 opens in a direction orthogonal to the center line CL. The center C2 of the second opening 11 is formed at a distance R from the second end surface 7b. Furthermore, the 2nd discharge port 70 is concentric with the 1st opening part 10, Comprising: It opens on the circumference of the diameter D1. Further, a threaded portion 31 is formed in the second opening 11 and the second discharge port 70.

  The suction cover 61 has an exhaust hole 12c and an exhaust hole 12b. The exhaust holes 12c and 12b have a circular cross section perpendicular to the extending direction. The suction cover 61 forms a passage 12 by connecting the exhaust hole 12b and the exhaust hole 12c. The exhaust hole 12c is a hole having a length LH and a diameter d1 extending from the first opening 10 toward the second end face 7b. Further, the exhaust hole 12c penetrates from the first opening 10 to the second end surface 7b. The exhaust hole 12 b is a hole having a length L <b> 2 and a diameter d <b> 1 extending from the second opening 11 toward the suction port 13. The end of the exhaust hole 12 b opposite to the second opening 11 and the width of the exhaust hole 12 c are connected within the suction cover 61 at an angle α1. Thus, the exhaust hole 12b and the exhaust hole 12c become a connected passage 12, and the first opening 10 exposed in the recess 62a, the second discharge port 70 exposed in the second end surface 7b, and the second side surface 8b. The exposed second opening 11 is connected. The length L2 of the exhaust hole 12b is shorter than the length LW from the second side surface 8b to the inner surface 61b. In the present embodiment, the diameters d1 of the exhaust holes 12b and the exhaust holes 12c are the same size, but are not limited to this, and may have different diameters. Furthermore, the angle α1 is connected at 90 °, but is not limited thereto, and may be an acute angle or an obtuse angle, for example.

  In the first modified example of the present invention, the centrifugal pump 1 is provided at the center of the impeller 5 by forming the passage 12 connecting the second opening 11 and the second discharge port 70 from the first opening 10 to the pump head 6A. The gas accumulated in the region CP is discharged from the pump chamber 9 to the outside of the pump head 6A through the exhaust holes 12b and 12c. In the centrifugal pump 1 according to the first modification, a discharge port is also formed on the suction port 13 side that is the portion 65C of the pump head 6A. And a bubble is discharged | emitted from the direction orthogonal to the centerline CL, and the suction inlet side. Therefore, as compared with the case where the bubbles are discharged only to the suction port side, the first modification can discharge the bubbles from the direction orthogonal to the center line CL, so that the amount of bubbles rising in the water tank is small. To increase. And the 1st modification can also suppress the quantity which suck | inhales a bubble again from a suction inlet. As a result, the centrifugal pump 1 according to the first modification can suppress the occurrence of suction failure and discharge failure, and can stably exhibit its ability. Moreover, since the amount of the gas which accumulates in the center region CP is reduced in the first modified example, it is possible to suppress a reduction in pump performance.

  Moreover, compared with the case where bubbles are discharged only from the suction port side, since the bubbles are discharged from the second opening 11 and the second discharge port 70, the amount of bubbles rising to the water surface in the water tank increases. . As a result, the first modification can suppress the amount of gas dissolved in the liquid as compared with the case where bubbles are discharged only from the suction port side.

  FIG. 7 is a cross-sectional view schematically showing a second modification of the pump head unit according to the embodiment of the present invention. The second modified example is the same as the embodiment shown in FIG. 3 except that the second opening 11b is opened to the portion 65D of the pump head 6B. In the description of the second modified example, the description of the configuration shown in FIG.

  The pump head 6 </ b> B is on the suction port 13 side of the suction cover 61, and a first opening 10 is opened at a portion 65 </ b> A facing the plurality of blades 51 of the impeller 5. The first opening 10 is on the suction port 13 side of the suction cover 61 and opens on a flat surface 61 a that faces the plurality of blades 51 of the impeller 5.

  In the pump head 6B, the second opening 11 is opened in a portion 65B that exists in a direction orthogonal to the center line CL. Specifically, the second opening 11 is opened in the second side surface 8b in a direction orthogonal to the center line CL. Further, in the pump head 6B, the second opening portion 11b is opened in a portion 65D of the casing 60. That is, in the present modification, the second side surface 8b corresponds to a portion 65B of the pump head 6B that exists in a direction orthogonal to the center line CL. The first end surface 7a corresponds to the portion 65D of the pump head 6B.

  The center C1 of the first opening 10 is formed on the circumference of the diameter D1 with the center line CL as the center. The first opening 10 is opened near the center region CP of the impeller 5. The second opening 11 is opened in a direction orthogonal to the center line CL, and the center C2 of the second opening 11 is formed at a position of a distance R from the second end surface 7b. Further, the center C3 of the second opening 11b is formed on a circumference having a diameter D2 with the center line CL as the center. Moreover, the thread part 31 is formed in the 2nd opening part 11 and the 2nd opening part 11b.

  The suction cover 61 has an exhaust hole 12a, an exhaust hole 12b, an exhaust hole 12d, and an exhaust hole 12e. The exhaust hole 12a, the exhaust hole 12b, the exhaust hole 12d, and the exhaust hole 12e have a circular cross section perpendicular to the extending direction. The suction cover 61 forms a passage 12 by connecting the exhaust hole 12a, the exhaust hole 12b, the exhaust hole 12d, and the exhaust hole 12e. The exhaust hole 12a is a hole having a length L1 and a diameter d1 extending from the first opening 10 toward the second end face 7b. The exhaust hole 12b is a hole having a length L2 and a diameter d1 extending from the second opening 11 toward the suction port 13. The exhaust hole 12d is a hole having a length L3 and a diameter d1 extending from the second opening 11b toward the plane 61d. Further, the exhaust hole 12d passes through the flat surface 61d from the second opening 11b. The exhaust hole 12e is a hole having a length L4 and a diameter d1 extending from the flat surface 60e toward the second end surface 7b. An end of the exhaust hole 12a opposite to the first opening 10 and an end of the exhaust hole 12b opposite to the second opening 11 are connected within the suction cover 61 at an angle α1. Further, the end of the exhaust hole 12d opposite to the second opening 11b is connected to the end of the exhaust hole 12e opposite to the second end surface 7b. Further, the second end face 7b side of the exhaust hole 12e is connected to the exhaust hole 12b at an angle α1 in the suction cover 61. As a result, the exhaust hole 12a, the exhaust hole 12b, the exhaust hole 12d, and the exhaust hole 12e form a connected passage 12. And the 1st opening part 10 exposed to the recessed part 62a, the 2nd opening part 11b exposed to the 1st end surface 7a, and the 2nd opening part 11 exposed to the 2nd side surface 8b are connected. In the present embodiment, the diameters d1 of the exhaust holes 12a, the exhaust holes 12b, the exhaust holes 12d, and the exhaust holes 12e are the same, but are not limited thereto, and may be different from each other. Furthermore, the angle α1 is connected at 90 °, but is not limited thereto, and may be an acute angle or an obtuse angle, for example.

  In the second modification of the present invention, the first opening 10, the second opening 11, the second opening 11b, the exhaust hole 12a, the exhaust hole 12b, the exhaust hole 12d, and the exhaust hole 12e are formed in the pump head 6B. Thus, the centrifugal pump 1 can discharge the gas accumulated in the central region CP of the impeller 5 from the pump chamber 9 to the outside of the pump head 6B through the exhaust hole 12a, the exhaust hole 12b, the exhaust hole 12d, and the exhaust hole 12e. it can. In the pump according to the second modification, the second opening 11b is formed on the side opposite to the suction port that is the portion 65D of the pump head 6B. The bubbles are discharged from a direction orthogonal to the center line CL and a direction opposite to the suction port. Therefore, as compared with the case where the bubbles are discharged only to the suction port side, the second modification can more suitably suppress the amount that the centrifugal pump 1 sucks the bubbles again. As a result, the pump including the second modified example can suppress the occurrence of suction failure and discharge failure, and can exhibit its ability more stably. Moreover, since the amount of the gas which accumulates in the center region CP is reduced in the first modified example, it is possible to suppress a reduction in pump performance.

  Further, in the second modification, the distance from when the bubbles are discharged from the second opening 11b to rise to the water surface is shorter than the distance from which the bubbles are discharged from the suction port side to rise to the water surface. Furthermore, the distance from when the bubbles are discharged from the second opening 11b to the surface of the water is shorter than the distance from when the bubbles are discharged from the second opening 11 to the surface of the water. Therefore, the centrifugal pump 1 according to the second modified example can shorten the time that bubbles stay in the liquid, so that the time that bubbles stay in the liquid can be reduced. Therefore, the second modified example can more suitably suppress the amount of gas dissolved in the liquid as compared with the case where the bubbles are discharged only from the direction orthogonal to the center line CL.

  Here, although the 2nd modification showed the example which discharges bubbles from the direction orthogonal to the center line CL and the direction opposite to the suction port side, the bubble discharge port is only in the direction opposite to the suction port side. May be formed. That is, in this example, the second opening 11b is formed only in the portion 65D of the pump head 6B.

  By forming the second opening 11b, which is a bubble discharge port, only in the direction opposite to the suction port side, the bubble is discharged only from the second opening 11b. That is, the bubbles are discharged from a direction closer to the water surface in the water tank. And compared with the example from which the bubble is discharged | emitted only from the direction orthogonal to the centerline CL, the distance which floats on a water surface also becomes short and the time which stays in a liquid also becomes short. As a result, the second modification can more suitably suppress the amount of gas dissolved in the liquid. In addition, since the amount of gas dissolved in the liquid can be more suitably suppressed, it is particularly preferable when handling a liquid for which the gas dissolution is to be reduced.

  FIG. 8 is a cross-sectional view schematically showing a third modification of the pump head portion according to the embodiment of the present invention. The third modified example is the same as the embodiment shown in FIG. 3 except that the second opening 11c is opened to the portion 65E of the pump head 6C. In the description of the third modification, the description of the configuration shown in FIG. 3 will be omitted in principle, and the description will focus on the different configuration.

  The pump head 6 </ b> C has the first opening 10 at a portion 65 </ b> A on the side of the suction port 13 of the suction cover 61 and facing the plurality of blades 51 of the impeller 5. Specifically, the first opening 10 is open to the plane 61 a facing the plurality of blades 51 of the impeller 5 on the suction port 13 side of the suction cover 61.

  In the pump head 6C, the second opening 11c is opened in a portion 65E that exists in a direction orthogonal to the center line CL. Specifically, the second opening 11c is opened in the first side surface 8a in a direction orthogonal to the center line CL. In the present modification, the first side surface 8a corresponds to a portion 65E of the pump head 6C that exists in a direction orthogonal to the center line CL.

  The center C1 of the first opening 10 is formed on the circumference of the diameter D1 with the center line CL as the center. The first opening 10 is opened near the center region CP of the impeller 5. The second opening portion 11c is opened in a direction orthogonal to the center line CL, and the center C4 of the second opening portion 11c is formed at a distance R1 from the first end surface 7a. Moreover, the thread part 31 is formed in the 2nd opening part 11c.

  An exhaust hole 12 f is formed in the casing 60. Further, the suction cover 61 is formed with an exhaust hole 12g and an exhaust hole 12h. The exhaust hole 12f, the exhaust hole 12g, and the exhaust hole 12h have a circular cross section perpendicular to the extending direction. The casing 60 and the suction cover 61 are connected to the exhaust hole 12f, the exhaust hole 12g, and the exhaust hole 12h to form the passage 12. The exhaust hole 12f is a hole having a length L6 and a diameter d1 extending from the second opening 11c toward the inner surface 60d. Further, the exhaust hole 12f penetrates from the second opening portion 11c to the inner surface 60d. The exhaust hole 12g is a hole having a length L5 and a diameter d1 extending from the first opening 10 toward the second end face 7b. The exhaust hole 12h is a hole having a length L7 and a diameter d1 extending from the curved surface 61c toward the suction port 13. The end of the exhaust hole 12f opposite to the second opening 11c and the end of the exhaust hole 12h opposite to the suction port 13 are connected. An end of the exhaust hole 12g opposite to the first opening 10 and an end of the exhaust hole 12h opposite to the curved surface 61c are connected at an angle α1 in the suction cover 61. Thereby, the exhaust hole 12f, the exhaust hole 12g, and the exhaust hole 12h become the connected passage 12, and the first opening 10 exposed in the recess 62a and the second opening 11c exposed in the first side surface 8a are connected.

  The length L5 of the exhaust hole 12g is shorter than the length LH from the flat surface 61a to the second end surface 7b, and the length L7 of the exhaust hole 12h is shorter than the length LW from the second side surface 8b to the inner surface 61b. The length L5 of the exhaust hole 12g is shorter than the length L1 of the exhaust hole 12a shown in FIG. Further, the total length L6 of the exhaust hole 12f and the length L7 of the exhaust hole 12h is the same as the length L2 of the exhaust hole 12b shown in FIG. In the present modification, the diameters d1 of the exhaust holes 12f, the exhaust holes 12g, and the exhaust holes 12h are the same size, but are not limited thereto, and may have different diameters. Furthermore, the angle α1 is connected at 90 °, but is not limited thereto, and may be an acute angle or an obtuse angle, for example.

  By forming the first opening 10, the second opening 11c, the exhaust hole 12f, the exhaust hole 12g, and the exhaust hole 12h in the pump head 6C, the centrifugal pump 1 pumps the gas accumulated in the central region CP of the impeller 5 The air is discharged from the chamber 9 to the outside of the pump head 6C through the exhaust hole 12f, the exhaust hole 12g, and the exhaust hole 12h. In the third modification, the length L5 of the exhaust hole 12g is shorter than the length L1 of the exhaust hole 12a shown in FIG. For this reason, bubbles are discharged at a shorter distance, and resistance when discharged is reduced. Therefore, the bubbles are more easily discharged. And the 3rd modification can suppress the quantity which suck | inhales a bubble again compared with the case where a bubble is discharged | emitted only to the suction inlet 13 side. As a result, the centrifugal pump 1 according to the third modification can suppress the occurrence of suction failure and discharge failure, and can exhibit its ability stably. Furthermore, the third modification can reduce the amount of gas accumulated in the central region CP, and therefore can suppress a reduction in pump performance.

  FIG. 9 is a cross-sectional view schematically showing a fourth modification of the pump head portion according to the embodiment of the present invention. The fourth modified example is the same as the above-described embodiment, except that a plurality of first openings 10 and 10a are provided. In the description of the fourth modification, a description of the same configuration as that of the above-described embodiment will be omitted in principle, and a description will be given focusing on a different configuration.

  In the pump head 6D, the first opening 10 and the first opening 10a are opened at a portion 65A on the side of the suction port 13 of the suction cover 61 and facing the plurality of blades 51 of the impeller 5. The first opening 10 and the first opening 10 a are open to a plane 61 a facing the plurality of blades 51 of the impeller 5 on the suction port 13 side of the suction cover 61.

  In the pump head 6D, the second opening 11 is opened at a portion 65B that exists in a direction orthogonal to the center line CL. Specifically, the second opening 11 is opened in the second side surface 8b in a direction orthogonal to the center line CL. That is, in the present modification, the second side surface 8b corresponds to the portion 65B of the pump head 6D that exists in a direction orthogonal to the center line CL.

  The center C1 of the first opening 10 is formed on the circumference of the diameter D1 with the center line CL as the center. The center C5 of the first opening 10a is formed on a circumference having a diameter D4 with the center line CL as the center. The first opening 10 is opened near the center region CP of the impeller 5. The second opening 11 is opened in a direction orthogonal to the center line CL, and the center C2 of the second opening 11 is formed at a position of a distance R from the second end surface 7b. In addition, a screw portion 31 is formed in the second opening portion 11.

  The suction cover 61 is formed with an exhaust hole 12a, an exhaust hole 12b, and an exhaust hole 12i. The exhaust hole 12a, the exhaust hole 12b, and the exhaust hole 12i have a circular cross section perpendicular to the extending direction. The suction cover 61 forms a passage 12 by connecting the exhaust hole 12a, the exhaust hole 12b, and the exhaust hole 12i. The exhaust hole 12a is a hole having a length L1 and a diameter d1 extending from the first opening 10 toward the second end face 7b. The exhaust hole 12b is a hole having a length L2 and a diameter d1 extending from the second opening 11 toward the suction port 13. The exhaust hole 12i is a hole having a length L1 and a diameter d1 extending from the first opening 10a toward the second end surface 7b. The end of the exhaust hole 12a opposite to the first opening 10 and the end of the exhaust hole 12b opposite to the second opening 11 are connected within the suction cover 61 at an angle α1. . Further, the end of the exhaust hole 12 i opposite to the first opening 10 a and the exhaust hole 12 b are connected at an angle α1 in the suction cover 61. Thus, the exhaust hole 12a, the exhaust hole 12b, and the exhaust hole 12i become a connected passage 12, and the first opening 10 and the first opening 10a exposed in the recess 62a and the second exposed in the second side surface 8b. The opening 11 is connected.

  The length L1 of the exhaust hole 12a and the exhaust hole 12i is shorter than the length LH from the flat surface 61a to the second end surface 7b. The length L2 of the exhaust hole 12b is shorter than the length LW from the second side surface 8b to the inner surface 61b. In the present embodiment, the diameters d1 of the exhaust holes 12a, the exhaust holes 12b, and the exhaust holes 12i are the same size, but are not limited thereto, and may have different diameters. Furthermore, the angle α1 is connected at 90 °, but is not limited thereto, and may be an acute angle or an obtuse angle, for example.

  By forming the first opening 10, the first opening 10a, the exhaust hole 12a, the exhaust hole 12b, and the exhaust hole 12i in the pump head 6D, the centrifugal pump 1 pumps the gas accumulated in the central region CP of the impeller 5 The air is discharged from the chamber 9 to the outside of the pump head 6D through the exhaust hole 12a, the exhaust hole 12b, and the exhaust hole 12i. And it can suppress that the bubble discharged | emitted from the 2nd opening part 11 enters from the suction inlet 13 again. As a result, the centrifugal pump 1 according to the fourth modification can suppress the suction failure and the discharge failure, and can stably exhibit the ability. Further, in the fourth modified example, it is possible to increase the discharge amount of bubbles as compared with the case where only one first opening is opened. As a result, the fourth modified example can reduce the amount of gas accumulated in the central region CP, and thus can more suitably suppress a reduction in pump performance. Further, in the fourth modified example, the amount of bubbles that rise to the water surface increases as compared with the case where the bubbles are discharged only from the suction port side. Therefore, since the amount of bubbles staying in the liquid can be reduced in the fourth modification, the amount of gas dissolved in the liquid can be suppressed.

In order to evaluate the performance of the centrifugal pump of the present invention, an air injection test was performed as a first performance test and a second performance test. FIG. 10 shows the external appearance of the equipment when the first and second performance tests of the centrifugal pump according to the present invention are carried out. As shown in FIG. 10, the performance test of the centrifugal pump 1 </ b> A is performed by submerging the pump head 6 </ b> E of the centrifugal pump 1 </ b> A in the fluid (fresh water) 25 stored in the acrylic water tank 24. Then, the fluid 25 was circulated and the air (air) was forcibly injected into the centrifugal pump 1A to measure the decrease in the capacity of the centrifugal pump 1A. The centrifugal pump 1A has a performance of a discharge amount of 250 L / min, a total head of 23 m, a rotational speed of 2900 min ⁻¹ and an electric motor output of 3.7 kW. The aquarium tank 24 has a tank diameter Db of 780 mm and a tank height Hb of 470 mm. Furthermore, air (air) was made to infiltrate into the centrifugal pump 1A from water by connecting a hose to an air compressor (not shown) capable of adjusting the amount of air.

  The positional relationship between the aquarium tank 24 and the centrifugal pump 1A is such that the height h1 from the bottom of the tank to the liquid level is 370 mm, the height h2 from the second end surface 7b of the pump head 6E to the liquid level is 170 mm, from the liquid level. The height h3 to the upper end of the tank is 100 mm, the height h4 from the bottom of the tank to the pump head 6E is 200 mm, and the height h5 from the second end surface 7b of the pump head 6E to the upper end of the tank is 270 mm. The fluid 25 was circulated by connecting the pipe 26 to the connecting member 18 of the centrifugal pump 1A and returning it to the water tank 24 again. In addition, a pressure gauge 27 was attached to the pipe 26 in order to measure the discharge pressure of the pump, and a valve 28 was attached in order to adjust the flow rate of the pump. Further, when returning the pipe 26 to the fluid 25, the return port of the pipe 26 was separated from the suction port so as not to affect the pump performance as much as possible, thereby eliminating air intrusion due to the influence of circulation as much as possible.

  The shape and structure of the suction cover 61 used in the first performance test are the same as those of the suction cover 61 shown in FIG. Therefore, the description is omitted. In the suction cover 61, there are four passages through which bubbles are discharged from the first opening 10 to the second opening 11, and passages through which bubbles are discharged from the first opening 10 to the second discharge port 70. There are four. The diameter D1 of the center C1 of the first opening 10 is 90 mm, and the diameter d1 of the passage 12 is 11 mm. The diameter D of the impeller 5 is 166 mm, and the diameter Ds of the beginning of the blade 51 of the impeller 5 (a circle connecting the ends on the center line CL side) is 70 mm. The first embodiment is an example in which the second discharge port 70 is closed and bubbles are discharged only from the second opening 11. The second embodiment is an example in which bubbles are discharged from both the second opening 11 and the second discharge port 70. In the comparative example, the second opening 11 and the second discharge port 70 are closed. In carrying out the first embodiment, the second embodiment, and the comparative example, the second opening portion 11 and the second discharge port 70 were blocked by screwing the plug 30 into the screw portion 31.

  In the air injection test, the centrifugal pump 1A is operated at 50 Hz, adjusted to have a flow rate of 50 L / min with the valve 28, the valve 28 is fixed, and the motor is operated at intervals of 5 Hz from 30 Hz to 50 Hz with an inverter. The rotation was adjusted by injecting air with an air compressor via an air flow meter. The result is shown in FIG. The discharge pressure (m) in the figure indicates before air is injected and after the maximum air injection amount (L / min) is injected. The discharge pressure (m) is a numerical value obtained by dividing the reading of the pressure gauge 27 by the specific gravity of the fresh water used at the time of the test and converting it into meters.

  In the first performance test, since the centrifugal pump 1A is operated based on the frequency (rotational speed), the discharge pressure (m) varies depending on the presence or absence of a passage. Therefore, the performance evaluation of the centrifugal pump of the present invention was conducted by investigating the decrease in the discharge pressure (m) with respect to the maximum air injection amount (L / min). That is, the larger the maximum air injection amount (L / min) and the smaller the decrease in the discharge pressure (m), the more effective, and the lower the discharge pressure (m) is 1.0 (m) or less. It shows that there is. In Example 1 and Example 2 which are embodiments of the present invention, even when the maximum air injection amount (L / min) is 10.0 (L / min), which is the largest, the discharge pressure (m) is reduced. 1.0 (m) or less. On the other hand, in the comparative example in which all of the second openings are closed, the discharge pressure (m) decreases by 1.0 (m) even though the maximum air injection amount (L / min) is 0.4 (L / min). There is an example that exceeds. Therefore, it turns out that Example 1 and Example 2 have an effect compared with a comparative example.

  Moreover, in Example 1, when a bubble was discharged | emitted from the 2nd opening part 11, a mode that it rose to a liquid level has been confirmed visually. In Example 2, when air bubbles were discharged from the second discharge port 70, it was possible to visually confirm the state of rising to the liquid level and the state of being sucked from the suction port 13. That is, in Example 1 and Example 2, bubbles are discharged in a direction orthogonal to the center line CL, and the bubbles rise in the water tank, so that the amount of gas that is sucked and dissolved from the suction port 13 is suppressed. ing. Therefore, the suction failure was suppressed and the pump capacity could be stably exhibited. In the comparative example, all of the second openings 11 are closed, so that some of the bubbles are discharged from the discharge port 14. In addition, it can be seen that in Example 1, even when air is injected about 10 times as compared with the comparative example, a decrease in pump performance is suppressed. In the comparative example, when the maximum air injection amount (L / min) exceeds 0.8 (L / min), the discharge pressure (m) is greatly reduced.

Next, the second performance test will be described. In the second performance test, the above-described air injection test was performed with a centrifugal pump having a discharge rate of 100 L / min, a total lift of 10 m, a rotational speed of 2900 min- ¹ and an electric motor output of 3.7 kW. The result is shown in FIG. In conducting the air injection test, the size of the aquarium tank, the arrangement of the aquarium tank and the centrifugal pump, and the method of connecting the pipes are the same as in the example shown in FIG.

  FIG. 12 is a cross-sectional view showing a half cross section in the pump width direction showing an outline of the pump head portion used in the second performance test. As shown in FIG. 12, the pump head 6 </ b> F is formed by combining a casing 600 and a suction cover 610. The casing 600 has a second opening 11b and an exhaust hole 12d. The suction cover 610 is formed with a first opening 10, a second opening 11, a second discharge port 70, an exhaust hole 12b, an exhaust hole 12c, and an exhaust hole 12e. The diameters of the exhaust hole 12b, the exhaust hole 12c, the exhaust hole 12d, and the exhaust hole 12e are all d1. As shown in FIG. 12, a pipe 17a and an L-shaped pipe 16a are attached to the second opening 11b, and air bubbles are discharged from the discharge port 29 of the L-shaped pipe 16a into the atmosphere. The blockage of the second outlet 70 was dealt with by screwing the plug 30. The first openings 10 are formed at four locations on the plane 61a, and are formed at intervals of 90 ° on the circumference of the diameter D1 with the center line CL of the shaft 3 as the center. Four exhaust holes 12b, exhaust holes 12c, exhaust holes 12d, and exhaust holes 12e are formed. In the suction cover 610, there are four passages 12 through which bubbles are discharged from the first opening 10 to the second opening 11, and the bubbles are discharged from the first opening 10 to the discharge port 29 via the second opening 11b. There are four passages 12. The number of passages 12 through which bubbles are discharged from the first opening 10 to the second discharge port 70 is four. The diameter D1 of the center C1 of the first opening 10 is 90 mm, and the diameter d1 of the passage is 11 mm. The diameter D of the impeller 5 is 135 mm, and the diameter Ds of the beginning of the blade 51 of the impeller 5 (a circle connecting the ends on the center line CL side) is 70 mm.

  The first embodiment is an example in which bubbles are discharged only from the discharge port 29 of the L-shaped pipe 16a. Example 2 is an example in which bubbles are discharged only from the second opening 11. In the comparative example, the second opening 11, the discharge port 29, and the second discharge port 70 are closed. In the conventional example, only the second discharge port 70 is opened. In carrying out the conventional example, the comparative example, the first embodiment, and the second embodiment, the second opening 11, the discharge port 29, and the second discharge port 70 were blocked by attaching the plug 30.

  The air injection test in the second performance test is the same as the air injection test in the first performance test, after operating the centrifugal pump 1A at 50 Hz and adjusting the flow rate to 50 L / min with the valve 28, The valve 28 was fixed, the number of rotations of the motor was adjusted at intervals of 5 Hz from 30 Hz to 50 Hz by an inverter, and air was injected by an air compressor through an air flow meter. The discharge pressure (m) is measured in the same manner as the method measured in the first performance test. The result is shown in FIG.

  In the second performance test, as in the first performance test, since the centrifugal pump 1A is operated based on the frequency (rotational speed), the discharge pressure (m) varies depending on the presence or absence of the passage. Therefore, in the second performance test, as in the first performance test, the performance evaluation of the centrifugal pump is evaluated by investigating the decrease in the discharge pressure (m) with respect to the maximum air injection amount (L / min). did. That is, the larger the maximum air injection amount (L / min) and the smaller the decrease in the discharge pressure (m), the more effective, and the lower the discharge pressure (m) is 1.0 (m) or less. It shows that there is. In Example 1 and Example 2, which are embodiments of the present invention, even when the maximum air injection amount (L / min) is 13.0 (L / min), the decrease in the discharge pressure (m) is as follows. 1.0 (m) or less.

  Further, in Example 1, it was confirmed visually that the bubbles were discharged from the discharge port 29 as liquid. In Example 2, when air bubbles were discharged from the second opening 11, it was confirmed visually that the liquid level was rising. In the comparative example, since the discharge port 29, the second opening 11 and the second discharge port 70 are all closed, some of the bubbles are discharged from the discharge port. Comparing the results of Example 1, Example 2, and Comparative Example, it can be seen that the results of Example 1 and Example 2 are better than the results of Comparative Example. In addition, it can be seen that in Example 1, even if the air is injected about twice as much as in the comparative example, the reduction in pump performance is suppressed. Furthermore, compared with the prior art example, in Example 1, the discharged air bubbles were suppressed from flowing again from the suction port. Moreover, the amount of dissolved gas is reduced because it floats on the water surface and is released to the atmosphere. As a result, poor suction was suppressed, and the pump capacity could be stably demonstrated. In the comparative example, when the maximum air injection amount (L / min) exceeds 3.0 (L / min), the discharge pressure (m) is greatly reduced.

  1, 1A centrifugal pump, 2 electric motor, 2a flange, 3 shaft, 3a through hole, 3b main body, 3c end, 3d screw, 3e key, 4 protective cover, 5 impeller, 6, 6A, 6B, 6C, 6D, 6E Pump head, 7 end surface, 7a 1st end surface, 7b 2nd end surface, 8 side surface, 8a 1st side surface, 8b 2nd side surface, 9 pump chamber, 9a area | region, 10, 10a 1st opening part, 11, 11b 2nd opening, 12 passage, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i exhaust hole, 13 suction port, 14 discharge port, 14b counterbore part, 15 support member, 16, 16a L-type piping 17, 17a Piping, 18 Connection member, 19a, 19b Bolt, 20a, 20b Nut, 21 Impeller nut, 22 Through hole, 24 Water tank, 25 Fluid, 26 Piping (for circulation), 27 Pressure gauge, 28 Valve, 29 Outlet, 30 Plug, 50 Disc, 50a Center, 50b Key groove, 50c Through hole, 50d Outer edge, 51 Blade, 52 Boss, 53 yen Circumference, 60, 600 Casing, 61, 610 Suction cover, 62 Recess, 63 Protrusion, 64 Curved surface, 60a, 60b, 61b Inner surface, 61a Plane, 70 Second discharge port, C1, C2, C3, C4, C5 Center , CL center line, CP center region, dp depth, D, D1, D2, D3, D4 diameter, Db tank diameter, H, Hb, h1, h2, h3, h4, h5 height, L1, L2, L3, L4, L5, L6, L7 Length, P1, P2 Dotted line, S range, α1, α2 Angle

Claims (5)

A suction port for sucking fluid;
Having at least a plurality of blades on the suction port side and rotating about a predetermined axis passing through the suction port, the fluid is sucked from the suction port, and the fluid is discharged in a direction perpendicular to the axis Impeller to
A pump head having the suction port and accommodating the impeller;
A first opening that opens to a portion of the pump head facing the plurality of blades on the suction port side;
A second opening that opens in a portion of the pump head that exists in at least one of the direction orthogonal to the axis and the direction opposite to the suction port side;
A passage connecting the first opening and the second opening;
Including centrifugal pump. A suction port for sucking fluid;
Having at least a plurality of blades on the suction port side and rotating about a predetermined axis passing through the suction port, the fluid is sucked from the suction port, and the fluid is discharged in a direction perpendicular to the axis Impeller to
A pump head having the suction port and accommodating the impeller;
A first opening that opens to a portion of the pump head facing the plurality of blades on the suction port side;
A second opening that opens to a portion of the pump head that exists in a direction perpendicular to the axis;
A passage connecting the first opening and the second opening;
Including centrifugal pump.   The centrifugal pump according to claim 1 or 2, wherein the number of the passages is 2 or more and 10 or less.   When the diameter of a circle connecting the end portions on the inner diameter side of the impeller of the impeller is Ds, and the diameter of the impeller is D, the first opening is 1.0 · Ds or more around the axis 1 The centrifugal pump according to any one of claims 1 to 3, wherein the centrifugal pump opens in a range of 0.0 · D or less.   The cross-section orthogonal to the extending direction of the passage is circular, and the diameter of the cross-section is 10% or more and 50% or less with respect to the diameter of the discharge port for discharging the fluid. Item 5. The centrifugal pump according to any one of items 4 to 5.

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