Wesco pump

Abstract

To suppress deterioration of performance of a Wesco pump.SOLUTION: A Wesco pump 1 includes: a casing 3 having a suction flow passage 11 and a discharge flow passage 12; a casing liner 7 arranged inside the casing 3, and having an inflow flow passage 7D connected to the suction flow passage 11, an outflow flow passage 7E connected to the discharge flow passage 12, and a partition wall 7F partitioning the inflow flow passage 7D and the outflow flow passage 7E; and an impeller 6 arranged inside the casing liner 7, and forming an annular fluid flow passage 10 connected to each of the inflow flow passage 7D and the outflow flow passage 7E between the casing liner 7 and the impeller 6. A curvature radius R of a flow passage forming surface 7G of the partition wall 7F facing the inflow flow passage 7D is 15 mm or more and 25 mm or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed herein relates to Wesco pumps. [Background technology]

[0002] A Westco pump is sometimes used as a feedwater pump for a steam boiler. Patent Document 1 discloses an example of a Westco pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 04-021793 Summary of the Invention [Problem to be solved by the invention]

[0004] If cavitation occurs inside a Wesco pump, the performance of the Wesco pump may be reduced.

[0005] The technology disclosed in this specification aims to suppress deterioration in the performance of a Westco pump. [Means for solving the problem]

[0006] This specification discloses a Westco pump. The Westco pump includes a casing having a suction passage and a discharge passage, a casing liner disposed inside the casing and having an inlet passage connected to the suction passage, an outlet passage connected to the discharge passage, and a partition wall separating the inlet and outlet passages, and an impeller disposed inside the casing liner and forming annular fluid passages between the impeller and the casing liner that are connected to the inlet and outlet passages. The radius of curvature of the passage-forming surface of the partition wall facing the inlet passage is 15 mm or more and 25 mm or less. [Effects of the Invention]

[0007] According to the technology disclosed in this specification, the degradation of the performance of the Westco pump is suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a Westco pump according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing a part of the Westco pump according to the embodiment. [Figure 3] FIG. 3 is an exploded perspective view showing a part of the Westco pump according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing a Westco pump according to an embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing a casing liner according to the embodiment. [Figure 6] FIG. 6 is a diagram showing the relationship between the radius of curvature of the flow path forming surface and the net suction head according to the embodiment. [Figure 7] FIG. 7 is a diagram showing a casing liner according to an example and a casing liner according to a comparative example. [Figure 8] FIG. 8 is a diagram showing the relationship between the flow rate and the net suction head for the casing liner according to the example and the casing liner according to the comparative example. [Figure 9] FIG. 9 is a diagram showing the relationship between the flow rate and the head for the casing liner according to the example and the casing liner according to the comparative example. [Figure 10] FIG. 10 is a diagram showing the relationship between the flow rate and the shaft power for the casing liner according to the example and the casing liner according to the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. In the embodiments, a three-dimensional Cartesian coordinate system is set, and the positional relationship of each part will be described with reference to the three-dimensional Cartesian coordinate system. The direction parallel to the X axis in a horizontal plane is defined as the X-axis direction. The direction parallel to the Y axis, which is orthogonal to the X axis in a horizontal plane, is defined as the Y-axis direction. The direction parallel to the Z axis, which is orthogonal to both the X axis and the Y axis, is defined as the Z-axis direction. The +Z side (+Z direction) is the upper side (upper), and the -Z side (-Z direction) is the lower side (lower).

[0010] Fig. 1 is a perspective view showing a Westco pump 1 according to an embodiment. Figs. 2 and 3 are each an exploded perspective view showing a portion of the Westco pump 1 according to an embodiment. Fig. 2 is an exploded perspective view of a portion of the Westco pump 1 as seen from the -Y side, and Fig. 3 is an exploded perspective view of a portion of the Westco pump 1 as seen from the +Y side. Fig. 4 is a cross-sectional view showing the Westco pump 1 according to an embodiment. Fig. 4 corresponds to a cross-sectional view taken along line AA in Fig. 1.

[0011] The Wesco pump 1 comprises a body 2, a casing 3 arranged on the -Y side of the body 2, a cover 4 arranged on the -Y side of the casing 3, a casing liner 7 arranged inside the casing 3, a guide member 8 held by the casing 3 and the casing liner 7, an impeller 6 arranged inside the casing liner 7, and a drive shaft 9 fixed to the impeller 6.

[0012] The impeller 6 rotates around a rotation axis extending in the Y-axis direction. In the embodiments, the direction parallel to the rotation axis of the impeller 6 will be referred to as the axial direction, the direction circumferentially around the rotation axis of the impeller 6 will be referred to as the circumferential direction or rotation direction, and the radial direction of the rotation axis of the impeller 6 will be referred to as the radial direction. In addition, in the radial direction, a position close to or approaching the rotation axis of the impeller 6 will be referred to as the radially inner direction, and a position farther from or away from the rotation axis of the impeller 6 will be referred to as the radially outer direction.

[0013] The body 2 is substantially cylindrical. A driving machine of the Westco pump 1, such as a motor, is disposed inside the body 2. The impeller 6 rotates by the power generated by the driving machine.

[0014] The casing 3 houses the casing liner 7. The casing 3 has a cylindrical portion 3B and a plate-like portion 3C arranged at the end of the cylindrical portion 3B on the +Y side. A shaft opening 3D is provided in the center of the plate-like portion 3C. The drive shaft 9 is inserted into the shaft opening 3D. A portion of the drive shaft 9 is arranged inside the shaft opening 3D.

[0015] Cover 4 is positioned so as to close the opening on the -Y side of cylindrical portion 3B. Cover 4 and casing 3 are fixed together with a plurality of screws 5. A screw boss having a screw opening 4A is provided on the periphery of cover 4. A screw boss having a screw opening 3A is provided on the periphery of cylindrical portion 3B. A plurality of screw openings 4A are provided on the periphery of cover 4. A plurality of screw openings 3A are provided on the periphery of cylindrical portion 3B. Screw 5 is inserted into screw opening 4A from the -Y side of cover 4, and then inserted into screw opening 3A. The threaded portion at the tip of screw 5 is inserted into a screw hole provided on the end face of body 2 on the -Y side.

[0016] The casing 3 has a suction passage 11 and a discharge passage 12. The Westco pump 1 discharges the fluid sucked into the suction passage 11 from the discharge passage 12. The fluid is a liquid. An example of the fluid is water.

[0017] The casing 3 has an inlet tube portion 3E in which the inlet flow path 11 is provided, a discharge tube portion 3F in which the discharge flow path 12 is provided, and a partition wall portion 3G that separates the inlet flow path 11 from the discharge flow path 12. The inlet tube portion 3E and the discharge tube portion 3F are each disposed at the top of the cylindrical portion 3B. The inlet tube portion 3E is disposed on the -X side of the discharge tube portion 3F. The inlet flow path 11 is provided inside the inlet tube portion 3E. The discharge flow path 12 is provided inside the discharge tube portion 3F. The partition wall portion 3G separates the inlet flow path 11 from the discharge flow path 12.

[0018] 5 is a cross-sectional view showing a casing liner 7 according to an embodiment. The casing liner 7 is disposed inside the casing 3. The casing liner 7 is disposed inside the cylindrical portion 3B. The casing liner 7 fits into the cylindrical portion 3B. The casing liner 7 has a disk portion 7A, an inner cylindrical portion 7B provided on the +Y side surface of the disk portion 7A, and an outer cylindrical portion 7C provided on the +Y side surface of the disk portion 7A.

[0019] The inner cylindrical portion 7B and the outer cylindrical portion 7C are each provided to protrude in the +Y direction from the +Y side surface of the disc portion 7A. The +Y side end face of the outer cylindrical portion 7C is positioned on the +Y side of the +Y side end face of the inner cylindrical portion 7B. The outer cylindrical portion 7C is positioned around the inner cylindrical portion 7B. The inner cylindrical portion 7B is positioned radially inward of the outer cylindrical portion 7C. The outer peripheral surface of the outer cylindrical portion 7C contacts the inner peripheral surface of the cylindrical portion 3B.

[0020] The casing liner 7 has an inlet passage 7D connected to the suction passage 11 and an outlet passage 7E connected to the discharge passage 12. The inlet passage 7D and the outlet passage 7E are each provided in an upper portion of the outer cylindrical portion 7C. The inlet passage 7D is located on the -X side of the outlet passage 7E. The inlet passage 7D is formed to penetrate the outer peripheral surface and inner peripheral surface of the outer cylindrical portion 7C. The outlet passage 7E is formed to penetrate the outer peripheral surface and inner peripheral surface of the outer cylindrical portion 7C. A partition wall portion 7F is provided between the inlet passage 7D and the outlet passage 7E. The partition wall portion 7F separates the inlet passage 7D and the outlet passage 7E. The partition wall portion 7F may be considered to be part of the outer cylindrical portion 7C.

[0021] The guide member 8 has a guide portion 8A and a pair of holding portions 8B. A portion of the guide portion 8A is arranged in the suction flow path 11. A portion of the guide portion 8A is arranged in the inlet flow path 7D. The holding portions 8B protrude from the guide portion 8A to one circumferential side and the other circumferential side. The guide member 8 is held by the casing 3. The holding portions 8B are arranged in holding grooves 3H provided in the upper part of the inner circumferential surface of the cylindrical portion 3B. The guide member 8 is held by the casing 3 by placing the holding portions 8B in the holding grooves 3H.

[0022] By arranging the guide portion 8A in the inlet of the inlet flow passage 7D, the dimension of the inlet of the inlet flow passage 7D is smaller than the dimension of the outlet of the outlet flow passage 7E in the Y-axis direction parallel to the rotation axis of the impeller 6. In the circumferential direction of the rotation axis of the impeller 6, the dimension of the inlet of the inlet flow passage 7D is larger than the dimension of the outlet of the outlet flow passage 7E. The inlet of the inlet flow passage 7D refers to the opening at the upper end (end on the +Z side) of the inlet flow passage 7D. The outlet of the outlet flow passage 7E refers to the opening at the upper end (end on the +Z side) of the outlet flow passage 7E.

[0023] The impeller 6 is disposed inside the casing liner 7. The impeller 6 is disposed inside the outer cylindrical portion 7C. The impeller 6 has a disk-shaped impeller body 6A, vane grooves 6B provided on the periphery of the impeller body 6A, and a shaft connecting tube 6C provided in the center of the impeller body 6A. A drive shaft 9 is inserted inside the shaft connecting tube 6C. The drive shaft 9 and the shaft connecting tube 6C are connected via a machine key 9A.

[0024] The surface of impeller body 6A on the -Y side faces the end face of inner cylindrical portion 7B on the +Y side. As drive shaft 9 rotates, impeller 6 rotates inside outer cylindrical portion 7C. When viewed from the +Y side, impeller 6 rotates counterclockwise, as shown by the arrow in Figure 3. In the following description, the direction in which impeller 6 rotates will be referred to as the forward rotation direction, and the direction opposite to the forward rotation direction will be referred to as the reverse rotation direction.

[0025] Between the impeller 6 and the casing liner 7, an annular fluid flow path 10 is formed, which is connected to the inlet flow path 7D and the outlet flow path 7E. The fluid flow path 10 is provided between the blade grooves 6B of the impeller 6 and the inner circumferential surface of the outer cylindrical portion 7C. A portion of the fluid flow path 10 is blocked by a partition wall portion 7F. The fluid supplied from the suction flow path 11 to the inlet flow path 7D flows into the fluid flow path 10.

[0026] In the fluid flow path 10, the rotation of the impeller 6 causes the fluid to flow out from inside the blade groove 6B. The fluid flowing out from the blade groove 6B exchanges momentum with the fluid in the fluid flow path 10, causing the pressure of the fluid in the fluid flow path 10 to increase. The fluid in the fluid flow path 10 with increased pressure flows back into the blade groove 6B. This pressure increase action is repeated in multiple blade grooves 6B, causing the fluid to flow through the fluid flow path 10 while increasing in pressure. The fluid flowing out from the blade groove 6B at the end of the fluid flow path 10 flows toward the outlet flow path 7E and is discharged from the discharge flow path 12. The partition wall 7F prevents the high-pressure fluid in the outlet flow path 7E from flowing back into the inlet flow path 7D.

[0027] As shown in Figures 4 and 5, the inflow passage 7D is provided at the upper end of the outer cylindrical portion 7C. The inflow passage 7D is defined by a passage-forming surface 7G of the partition wall portion 7F facing the inflow passage 7D. In a cross section perpendicular to the rotation axis of the impeller 6, the passage-forming surface 7G is provided to connect a first portion 7Ga of the outer peripheral surface of the partition wall portion 7F to a second portion 7Gb of the outer peripheral surface of the inner cylindrical portion 7B. The passage-forming surface 7G guides the fluid that has flowed into the inflow passage 7D to the fluid passage 10. The inflow passage 7D is defined between the first portion 7Ga and the second portion 7Gb in the radial direction. The pressure increase effect of the fluid due to the blade grooves 6B does not occur in the inflow passage 7D.

[0028] As described above, the impeller 6 rotates inside the outer cylindrical portion 7C. The surface of the impeller body 6A on the -Y side faces the end face of the inner cylindrical portion 7B on the +Y side. In the radial direction of the rotation axis of the impeller 6, the blade grooves 6B on the periphery of the impeller 6 are positioned outside the second portion 7Gb. The blade grooves 6B on the periphery of the impeller 6 are positioned outside the second portion 7Gb and inside the first portion 7Ga.

[0029] The flow path forming surface 7G is arc-shaped in a cross section perpendicular to the rotation axis of the drive shaft 9. The second portion 7Gb is disposed on the forward rotation side of the first portion 7Ga. The flow path forming surface 7G is arc-shaped and recessed inward in the reverse rotation direction or radially inward from the inflow flow path 7D.

[0030] The radius of curvature R of the flow path forming surface 7G facing the inflow flow path 7D is 15 mm or more and 25 mm or less. The radius of curvature R of the flow path forming surface 7G may be 16 mm or more and 24 mm or less, 17 mm or more and 23 mm or less, 18 mm or more and 22 mm or less, or 19 mm or more and 21 mm or less. In this embodiment, the radius of curvature R of the flow path forming surface 7G is 20 mm.

[0031] 6 is a diagram showing the relationship between the radius of curvature R of the flow path forming surface 7G and the net positive suction head according to the embodiment. The net positive suction head (NPSH) is a parameter that indicates the likelihood of cavitation occurring in the Westco pump 1. The smaller the NPSH, the less likely cavitation is to occur.

[0032] As shown in Figure 6, when the curvature radius R of the flow path forming surface 7G is 4 mm, the NPSH is 6.36 m. When the curvature radius R of the flow path forming surface 7G is 40 mm, the NPSH is 5.96 m. When the curvature radius R of the flow path forming surface 7G is 20 mm, the NPSH is 5.22 m. When the curvature radius R of the flow path forming surface 7G is in the range of 4 mm to 40 mm, the NPSH is minimized when the curvature radius R of the flow path forming surface 7G is 20 mm. Therefore, when the curvature radius R of the flow path forming surface 7G is 20 mm, cavitation is less likely to occur in the Westco pump 1.

[0033] If the radius of curvature R of the flow path forming surface 7G is less than 15 mm or more than 25 mm, there is a high possibility that the inflow flow path 7D will become negative pressure, and as a result, there is a high possibility that cavitation will occur in the inflow flow path 7D. If cavitation occurs in the inflow flow path 7D, the performance of the Westco pump 1 will deteriorate. If the radius of curvature R of the flow path forming surface 7G is 15 mm or more and 25 mm or less, the occurrence of cavitation in the inflow flow path 7D will be suppressed. By suppressing the occurrence of cavitation, the deterioration of the performance of the Westco pump 1 will be suppressed.

[0034] FIG. 7 is a diagram showing a casing liner 7 according to an embodiment and a casing liner according to a comparative example. The radius of curvature of the flow path forming surface 7G of the casing liner 7 according to the embodiment is 20 mm. The radius of curvature of the flow path forming surface of the casing liner according to the comparative example is 4 mm. FIG. 8 is a diagram showing the relationship between the flow rate and the net suction head for the casing liner 7 according to the embodiment and the casing liner according to the comparative example. FIG. 9 is a diagram showing the relationship between the flow rate and the head for the casing liner 7 according to the embodiment and the casing liner according to the comparative example. FIG. 10 is a diagram showing the relationship between the flow rate and the shaft power for the casing liner 7 according to the embodiment and the casing liner according to the comparative example.

[0035] 8, 9, and 10, the flow rate [L / h] refers to the flow rate of fluid per unit time flowing into the inlet passage 7D via the suction passage 11. In FIG. 9, the head [m] refers to the capacity of the Westco pump 1 to pump water. In FIG. 10, the shaft power [kW] refers to the power given to the Westco pump 1 by the driver to drive the Westco pump 1. The larger the head [m], the higher the performance of the Westco pump 1. The smaller the shaft power [kW], the less energy is required to drive the Westco pump 1.

[0036] As shown in Figure 8, in the Westco pump 1 according to the embodiment, the NPSH is small when the flow rate is low and when the flow rate is high. On the other hand, in the Westco pump according to the comparative example, the NPSH is small when the flow rate is low, but is large when the flow rate is high.

[0037] As shown in Figure 9, the difference between the head of the Westco pump 1 according to the embodiment and the head of the Westco pump according to the comparative example is small. In other words, even if the radius of curvature R of the flow path forming surface changes, the head does not change. Even if the radius of curvature R of the flow path forming surface changes, the performance related to the head of the Westco pump is maintained.

[0038] 10, the shaft power of the Westco pump 1 according to the embodiment is smaller than that of the Westco pump according to the comparative example. The Westco pump 1 according to the embodiment can be operated with a smaller shaft power than the Westco pump according to the comparative example.

[0039] As described above, the Westco pump 1 according to the embodiment comprises a casing 3 having an inlet flow path 11 and a discharge flow path 12, a casing liner 7 arranged inside the casing 3 and having an inlet flow path 7D connected to the inlet flow path 11, an outlet flow path 7E connected to the discharge flow path 12, and a partition wall portion 7F separating the inlet flow path 7D and the outlet flow path 7E, and an impeller 6 arranged inside the casing liner 7 and forming an annular fluid flow path 10 connected to each of the inlet flow path 7D and the outlet flow path 7E between the impeller 6 and the casing liner 7. The radius of curvature R of a flow path forming surface 7G of the partition wall portion 7F facing the inlet flow path 7D is 15 mm or more and 25 mm or less.

[0040] According to the embodiment, the radius of curvature R of the flow path forming surface 7G of the partition wall portion 7F facing the inflow flow path 7D is 15 mm or more and 25 mm or less, so that the occurrence of cavitation is suppressed in the inflow flow path 7D. Since the occurrence of cavitation is suppressed, the deterioration of the performance of the Westco pump 1 is suppressed.

[0041] When the curvature radius R of the flow passage forming surface 7G is 20 mm, the NPSH reaches a minimum value when the curvature radius R of the flow passage forming surface 7G is in the range of at least 4 mm to 40 mm.

[0042] The casing 3 has a cylindrical portion 3B. The casing liner 7 has an outer cylindrical portion 7C that contacts the inner peripheral surface of the cylindrical portion 3B, and an inner cylindrical portion 7B that is disposed radially inward of the outer cylindrical portion 7C. The partition wall portion 7F may be considered to be part of the outer cylindrical portion 7C. In a cross section perpendicular to the rotation axis of the impeller 6, the flow path forming surface 7G is provided so as to connect a first portion 7Ga of the outer peripheral surface of the partition wall portion 7F to a second portion 7Gb of the outer peripheral surface of the inner cylindrical portion 7B. The flow path forming surface 7G, whose curvature radius R is 15 mm or more and 25 mm or less, is provided between the first portion 7Ga and the second portion 7Gb, thereby suppressing the occurrence of cavitation in the inlet flow path 7D.

[0043] The impeller 6 rotates inside the outer cylindrical portion 7C. The blade grooves 6B on the periphery of the impeller 6 are positioned outside the second portion 7Gb in the radial direction of the rotation axis of the impeller 6. This allows the fluid in the inlet flow path 7D to smoothly flow into the fluid flow path 10 with the occurrence of cavitation suppressed.

[0044] The Westco pump 1 is provided with a guide member 8 that is held in the casing 3 and has a guide portion 8A that is disposed in the inlet passage 7D. In the Y-axis direction that is parallel to the rotational axis of the impeller 6, the size of the inlet of the inlet passage 7D is smaller than the size of the outlet of the outlet passage 7E. Because the fluid is guided by the guide portion 8A in the inlet passage 7D and the size of the inlet of the inlet passage 7D is smaller than the size of the outlet of the outlet passage 7E in the Y-axis direction, the occurrence of cavitation in the inlet passage 7D is suppressed. [Explanation of symbols]

[0045] 1...Wesco pump, 2...body, 3...casing, 3A...screw opening, 3B...cylindrical portion, 3C...plate-shaped portion, 3D...shaft opening, 3E...suction tube portion, 3F...discharge tube portion, 3G...partition wall portion, 3H...retaining groove, 4...cover, 4A...screw opening, 5...screw, 6...impeller, 6A...impeller body, 6B...blade groove, 6C...shaft connecting tube, 7...casing liner, 7A...disk portion, 7B...inner tube portion, 7C...outer tube portion, 7D...inflow passage, 7E...outflow passage, 7F...partition wall portion, 7G...passage forming surface, 7Ga...first portion, 7Gb...second portion, 8...guide member, 8A...guide portion, 8B...retaining portion, 9...drive shaft, 9A...machine key, 10...fluid passage, 11...suction passage, 12...discharge passage.

Claims

1. a casing having a suction passage and a discharge passage; a casing liner disposed inside the casing, the casing having an inlet passage connected to the suction passage, an outlet passage connected to the discharge passage, and a partition wall portion separating the inlet passage and the outlet passage; an impeller disposed inside the casing liner and defining an annular fluid flow path between the impeller and the casing liner, the annular fluid flow path being connected to the inlet flow path and the outlet flow path; The radius of curvature of the flow path forming surface of the partition wall portion facing the inflow flow path is 15 mm or more and 25 mm or less. Wesco pump.

2. The radius of curvature of the flow path forming surface is 20 mm.

2. The Wesco pump of claim 1.

3. the casing has a cylindrical portion, the casing liner has an outer cylindrical portion in contact with an inner circumferential surface of the cylindrical portion, and an inner cylindrical portion disposed radially inward of the outer cylindrical portion, the partition wall portion is a part of the outer cylindrical portion, In a cross section perpendicular to the rotation axis of the impeller, the flow path forming surface is provided to connect a first portion of an outer peripheral surface of the partition wall portion and a second portion of an outer peripheral surface of the inner cylindrical portion.

2. The Wesco pump of claim 1.

4. The impeller rotates inside the outer cylindrical portion, a peripheral portion of the impeller is disposed outward from the second portion in a radial direction of the rotation axis of the impeller; 4. The Wesco pump of claim 3.

5. a guide member that is held by the casing and has a guide portion that is disposed in the inlet flow path; In a direction parallel to the rotation axis of the impeller, a dimension of an inlet of the inlet passage is smaller than a dimension of an outlet of the outlet passage.

2. The Wesco pump of claim 1.

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