Centrifugal pump

Abstract

The present invention reduces cavitation that occurs in the vicinity of a blade of an inducer provided in a centrifugal pump.　A centrifugal pump (1) according to the present invention comprises: a rotating shaft (3); an impeller (4) that is attached to the rotating shaft and sucks in a handled liquid; an inducer (6) disposed upstream of the impeller with respect to the flow of the handled liquid; and a suction pipe (7) that accommodates the inducer and introduces the handled liquid into the inducer and the impeller. The suction pipe is provided with a cylindrical inner peripheral surface (71). The inner peripheral surface is provided with at least one uneven surface (8) having a plurality of recesses and / or a plurality of protrusions. The uneven surface is disposed on an upstream-side inner peripheral surface (72), positioned upstream of the inducer with respect to the flow, of the inner peripheral surface.

Description

centrifugal pump

[0001] The present invention relates to a centrifugal pump.

[0002] A centrifugal pump includes an impeller that sucks in the pumped liquid and an inducer that is located upstream of the impeller in the flow of the pumped liquid. The inducer serves to reduce cavitation that occurs in the pumped liquid flowing through the impeller when the impeller rotates at high speed. The inducer pressurizes the pumped liquid upstream of the impeller, improving the suction performance of the centrifugal pump (see, for example, Patent Document 1).

[0003] JP 2016-37936 A

[0004] The inducer is designed to have an optimal shape to match the suction pipe diameter, which corresponds to the impeller rotation speed and discharge volume (flow rate). The flow velocity of the pumped liquid in the suction pipe is increased as the inducer rotates, causing the pumped liquid to swirl. This flow velocity is further increased near the inducer blades, causing the pumped liquid pressure to decrease. Here, a backflow of the pumped liquid occurs near the upstream end of the inducer, which rotates at high speed in the suction pipe. The backflow is a flow in the opposite direction to the main flow of the pumped liquid in the suction pipe. Near the inducer blades, the main flow and the backflow interact with each other, causing a decrease in the pressure of the pumped liquid. When the pressure of the pumped liquid decreases, cavitation can occur near the inducer blades. Cavitation reduces the suction performance of the centrifugal pump. Cavitation can cause vibration, noise, and fatigue damage to the inducer.

[0005] An object of the present invention is to reduce cavitation occurring near the blades of an inducer provided in a centrifugal pump.

[0006] In one embodiment of the present invention, a centrifugal pump comprises a rotating shaft, an impeller attached to the rotating shaft and sucking in the treated liquid, an inducer arranged upstream of the impeller in the flow of the treated liquid, and a suction pipe that houses the inducer and introduces the treated liquid to the inducer and the impeller, wherein the suction pipe has a cylindrical inner circumferential surface, and the inner circumferential surface has at least one uneven surface having a plurality of recesses and / or a plurality of protrusions, and the uneven surface is arranged on the upstream inner circumferential surface that is located upstream of the inducer in the flow.

[0007] According to the present invention, cavitation occurring near the blades of an inducer included in a centrifugal pump is reduced.

[0008] 1 is a schematic cross-sectional view of a centrifugal pump showing an embodiment of the present invention; FIG. 2 is a schematic partial cross-sectional view of the suction pipe showing an inducer provided in the centrifugal pump of FIG. 1 and an uneven surface of the suction pipe; FIG. 3 is a schematic view of cavitation occurring near the blades of the inducer provided in the centrifugal pump of FIG. 1, as viewed from the upstream side of the flow; FIG. 4 is a schematic partial cross-sectional view of the suction pipe showing the main flow of the pumped liquid generated by the rotation of the inducer provided in the centrifugal pump of FIG. 1; FIG. 5 is a schematic view showing the pressure distribution and flow of the pumped liquid generated by the rotation of the inducer provided in a conventional centrifugal pump; FIG. 6 is a schematic view showing the pressure distribution and flow of the pumped liquid generated by the rotation of the inducer provided in the centrifugal pump of FIG. 1; FIG. 7 is a list of patterns (variations) of the uneven surface of the suction pipe showing another embodiment (variations of the first embodiment) of the centrifugal pump according to the present invention; FIG. 8 is a schematic view showing the pattern shape of the uneven surface shown in FIG. 1 is a schematic diagram showing cavitation occurring near the inducer blades for each of the modified examples (No. 1 to No. 12) shown in FIG. 7, viewed from the upstream side of the flow.

[0034] FIG. 1 is a graph showing the volume of cavitation for each of the modified examples (No. 1 to No. 12) shown in FIG. 7.

[0035] FIG. 1 is a line graph showing the head capacity for each of the modified examples (No. 1 to No. 5) shown in FIG. 7.

[0036] FIG. 1 is a line graph showing the head capacity for each of the modified examples (No. 6 to No. 9) shown in FIG. 7.

[0037] FIG. 1 is a graph showing the rate of decrease in head capacity for each of the modified examples (No. 1 to No. 12) shown in FIG. 7.

[0038] FIG. 1 is a table showing patterns (modified examples) of the concave-convex surface of the suction pipe showing yet another embodiment (modified example of the second embodiment) of the centrifugal pump according to the present invention.

[0039] FIG. 15 is a schematic diagram showing the pattern arrangement of the concave-convex surface shown in FIG. 15A and 15B are schematic diagrams showing cavitation occurring near the inducer blades for each of the modified examples (No. 13 to No. 20) shown in Fig. 15, viewed from the upstream side of the flow. 15B are graphs showing the volume of cavitation for each of the modified examples (No. 13 to No. 20) shown in Fig. 15. 15C are line graphs showing the head capacity for each of the modified examples (No. 13 to No. 18) shown in Fig. 15. 15D are line graphs showing the head capacity for each of the modified examples (No. 19, No. 20) shown in Fig. 15.22. FIG. 23 is a graph showing the rate of decrease in head capacity for each of the modified examples (No. 13 to No. 20) shown in FIG. 15. FIG. 24 is a table listing patterns (modified examples) of the uneven surface of the suction pipe showing yet another embodiment (modified example of the third embodiment) of the centrifugal pump according to the present invention. FIG. 25 is a schematic diagram showing the pattern arrangement of the uneven surface shown in FIG. 22. FIG. 26 is a schematic diagram showing cavitation occurring near the inducer blades for each of the modified examples (No. 21 and No. 22) shown in FIG. 22, viewed from the upstream side of the flow. FIG. 27 is a graph showing the volume of cavitation for each of the modified examples (No. 21 and No. 22) shown in FIG. 22. FIG. 28 is a line graph showing the head capacity for each of the modified examples (No. 21 and No. 22) shown in FIG. 22. FIG. 29 is a graph showing the rate of decrease in head capacity for each of the modified examples (No. 21 and No. 22) shown in FIG.

[0009] An embodiment of a centrifugal pump according to the present invention will be described below. In the following description, reference will be made to the drawings as appropriate. In the drawings, the same members and elements are designated by the same reference numerals, and duplicated explanations will be omitted. Furthermore, the dimensional proportions of the elements may be exaggerated for the sake of convenience, and are not limited to the proportions shown in the drawings.

[0010] First Embodiment Configuration of Centrifugal Pump (1) The configuration of the centrifugal pump according to the present invention will be described below.

[0011] FIG. 1 is a schematic cross-sectional view of a centrifugal pump according to an embodiment of the present invention.

[0012] A centrifugal pump according to the present invention (hereinafter referred to as "the pump") pumps a liquid to be handled (hereinafter referred to as "handled liquid"). The pump 1 includes a motor 2, a rotating shaft 3, an impeller 4, a housing 5, an inducer 6, a suction pipe 7, a concave-convex surface 8, a discharge pipe 9, and a control device (not shown).

[0013] In the following description, the "upstream side" refers to the upstream side in the flow of the pumped liquid being pumped to the pump 1, and the "downstream side" refers to the downstream side in the flow of the pumped liquid.

[0014] The motor 2 is driven at a predetermined drive voltage and drive frequency to rotate the impeller 4 and inducer 6, which will be described later. The motor 2 is a known motor that is composed of a rotor (not shown) attached to a rotary shaft 3 and a stator (not shown) that rotates the rotor. The motor 2 is connected to a power source (not shown) that operates the motor 2. The motor 2 is connected to a control device (not shown) that controls the operation of the motor 2. The motor 2 has the rotary shaft 3 at its rotating axis.

[0015] The rotating shaft 3 is rotated by the motor 2 and transmits rotational power to the impeller 4 and inducer 6, which will be described later. The impeller 4 and the inducer 6 are arranged axially on the rotating shaft 3. The rotating shaft 3 has a cylindrical shape. The upstream end of the rotating shaft 3 protrudes into the suction pipe 7, which will be described later.

[0016] The impeller 4 is attached to the rotary shaft 3 and sucks in the pumped fluid. The impeller 4 discharges the sucked pumped fluid. The impeller 4 delivers the pumped fluid in response to the rotation of the rotary shaft 3. The impeller 4 is attached to the rotary shaft 3.

[0017] The housing 5 houses the motor 2, the rotating shaft 3, and the impeller 4. The housing 5 defines a pump chamber 51, which houses the impeller 4. The housing 5 has an inlet 52 for drawing in the pumped fluid and an outlet 53 for discharging the pumped fluid. That is, the housing 5 has the inlet 52 on the upstream side of the flow of the pumped fluid that flows as the impeller 4 rotates, and the outlet 53 on the downstream side of the flow. The inlet 52 is located on the opposite side of the motor 2 in the axial direction of the rotating shaft 3. The inlet 52 is located coaxially with the rotating shaft 3. The upstream end of the rotating shaft 3 protrudes from the inlet 52 of the housing 5. The housing 5 connects the suction pipe 7 and the discharge pipe 9, which will be described later. The suction pipe 7 is connected to the housing 5 at the opening of the inlet 52. The discharge pipe 9 is connected to the housing 5 at the opening of the outlet 53.

[0018] The inducer 6 is disposed upstream of the impeller 4 in the flow of the pumped liquid. The inducer 6 is attached to the rotating shaft 3 and sucks in the pumped liquid. The inducer 6 sends the sucked in pumped liquid toward the impeller 4. The inducer 6 pressurizes the pumped liquid upstream of the impeller 4, improving the suction performance of the pump 1. The inducer 6 is attached to the upstream end of the rotating shaft 3 that protrudes from the inlet 52 of the casing 5. The inducer 6 is disposed inside the suction pipe 7. The inducer 6 has blades 61 (see FIG. 2) that protrude radially from the rotating shaft 3.

[0019] The blades 61 generate a flow of the handled fluid by the rotation of the rotary shaft 3. The number of blades 61 is four, and the shape of the blades 61 is approximately fan-shaped (see FIG. 3).

[0020] In the present invention, the inducer 6 may have any shape as long as it can generate a flow of the pumped fluid by the rotation of the rotary shaft 3. The number of blades 61 is not limited to four. The shape of the blades 61 is not limited to a substantially fan shape.

[0021] The suction pipe 7 houses the inducer 6 and introduces the pumped liquid into the inducer 6 and the impeller 4. The suction pipe 7 is cylindrical. The suction pipe 7 is connected to the opening of the inlet 52 of the housing 5 and is arranged upstream of the flow of the pumped liquid in the pump 1. The suction pipe 7 is connected to another pipe (flow path) upstream of the suction pipe 7. The suction pipe 7 has an inner circumferential surface 71.

[0022] 2 is a schematic partial cross-sectional view of the suction pipe 7 showing the inducer 6 and the uneven surface 8 of the suction pipe 7. In the following description, FIG. 1 will be referred to as appropriate.

[0023] In the following description, the "circumferential direction" refers to the direction along the circumference of the suction pipe 7, the "radial direction" refers to the direction along the diameter (radius) of the suction pipe 7, and the "axial direction" refers to the axial direction (extension direction) of the suction pipe 7.

[0024] The inner circumferential surface 71 has a length in the axial direction of the suction pipe 7. The inner circumferential surface 71 includes an upstream inner circumferential surface 72 located upstream of the inducer 6 arranged inside the suction pipe 7 in the flow direction.

[0025] The upstream inner circumferential surface 72 includes a placement region 73 of the inner circumferential surface 71 where the uneven surface 8 is placed. The placement region 73 is the region where the uneven surface 8 is placed. The upstream inner circumferential surface 72 has the axial length of the inner circumferential surface 71 located upstream of the inducer 6 in the flow direction.

[0026] The uneven surface 8 is a region of the inner circumferential surface 71 where multiple recesses and / or multiple protrusions are arranged. The uneven surface 8 is arranged at a position that disrupts the swirling flow of treated fluid in the suction pipe 7, which swirls along the inner circumferential surface 71 toward the inducer 6 when the treated fluid is sucked into the impeller 4. The uneven surface 8 of this embodiment has multiple recesses. The uneven surface 8 is arranged on the upstream inner circumferential surface 72 of the inner circumferential surface 71, which is located upstream of the inducer 6 in the flow. The uneven surface 8 is arranged on an end 74 of the upstream inner circumferential surface 72 on the inducer 6 side. The uneven surface 8 is arranged in an annular shape in the circumferential direction of the inner circumferential surface 71 of the suction pipe 7. In other words, the uneven surface 8 is arranged in a cylindrical shape having a predetermined length from the end 74 toward the upstream side of the flow on the upstream inner circumferential surface 72. The cylindrically arranged region is the arrangement region 73. That is, the arrangement region 73 is located upstream in the flow direction from the end 74 of the inner circumferential surface 71 on the inducer 6 side.

[0027] The "predetermined length" refers to the length (region) of the flow of treated fluid in the suction pipe 7 that causes a pressure drop, as described below, when the treated fluid is being sucked into the inducer 6. In other words, the predetermined length refers to the axial length (region) of the suction pipe 7 relative to the swirling flow that causes a pressure drop, among the swirling flow that swirls along the inner circumferential surface 71. In other words, the predetermined length is set as the axial length of the suction pipe 7 in the arrangement region 73.

[0028] In this embodiment, the recesses of the uneven surface 8 are hemispherical. The recesses are hemispherical with a diameter of 4 mm and a radius (depth) of 2 mm. The recesses are arranged in an arrangement region 73 on the upstream inner circumferential surface 72. The recesses protrude in the radial direction. The recesses are arranged in three rows in the axial direction and are arranged alternately in the axial direction. The axial length of the uneven surface 8 is 20 mm. In other words, the predetermined length is set to 20 mm. The uneven surface 8 is formed by molding.

[0029] Returning to Figure 1, the discharge pipe 9 discharges the pumped fluid from the impeller 4. The discharge pipe 9 is horn-shaped, with a diameter increasing toward the downstream side (upper side) of the discharge pipe 9. The discharge pipe 9 is connected to the opening of the outlet 53 of the housing 5 and is disposed downstream in the flow of the pumped fluid. The discharge pipe 9 is connected to another pipe (flow path) downstream of the discharge pipe 9.

[0030] A control device (not shown) controls the operation of the motor 2 to control the flow rate (discharge flow rate) of the pumped fluid discharged from the pump 1. The control device includes a control unit, a memory unit, and a display unit.

[0031] The control unit controls the operation of the pump 1. The control unit acquires flow rate information of the pump 1 and rotation information of the motor 2 as sensor information via a sensor (not shown). The flow rate information is information related to the flow rate of the pumped liquid being discharged from the pump 1. The rotation information is information related to the rotation of the rotating shaft 3 of the motor 2. The control unit controls the operation of the motor 2 to obtain the flow rate of the pump 1 based on the sensor information. The control unit stores the measured sensor information and control information for controlling the rotation of the rotating shaft 3 of the motor 2 in the memory unit. The control unit transmits the sensor information and the control information to the display unit. The control unit is connected to the memory unit and the display unit.

[0032] The control unit is composed of, for example, a processor such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), or DSP (Digital Signal Processor), a volatile memory such as RAM (Random Access Memory) that functions as the processor's working area, and a non-volatile memory such as ROM (Read Only Memory) that stores various information such as control of data analysis processing.

[0033] The storage unit stores sensor information and control information. The storage unit is connected to the display unit. The storage unit may be, for example, a portable storage medium such as a hard disk drive (HDD), a solid state drive (SSD), or a flash memory, or other non-transitory storage medium, or a RAM or other temporary storage medium.

[0034] The display unit displays sensor information and control information. The display unit is a touch panel. A user of the pump 1 controls the operation of the pump 1 by operating the operation screen displayed on the display unit.

[0035] Explanation of Cavitation Next, the cavitation that occurs near the blades 61 of the inducer 6 provided in the pump 1 will be explained below.

[0036] Figure 3 is a schematic diagram showing cavitation occurring near the vanes 61 of the inducer 6 of the pump 1, as viewed from the upstream side of the flow. The figure shows a comparative example of a conventional centrifugal pump and an embodiment of the pump 1, both of which have the same operating conditions. Figure 4 is a schematic partial cross-sectional view of the suction pipe 7, showing the main flow of the pumped liquid generated by the rotation of the inducer 6 of the pump 1. The arrows in the figure indicate the swirling flow swirling within the suction pipe 7. Figure 5 is a schematic diagram showing the pressure distribution and flow of the pumped liquid generated by the rotation of the inducer 6 of a conventional centrifugal pump. The figure shows the pressure region with a dashed line, and the flow of the pumped liquid with arrows.

[0037] Cavitation is a phenomenon in which bubbles are generated when the pressure of the pumped liquid drops below its saturated vapor pressure. Bubbles are generated when the pumped liquid changes from liquid to gas. Near the blades 61 of the inducer 6, the main flow and the reverse flow interact with each other, causing a drop in the pressure of the pumped liquid. When the pressure of the pumped liquid drops, cavitation can occur near the blades 61 of the inducer 6. Cavitation reduces the suction performance of the pump 1. Cavitation can cause vibration, noise, and fatigue failure of the inducer 6. Increased cavitation can cause cavitation surge. Cavitation surge is a phenomenon that causes pulsation in the pump 1 when cavitation disappears (changing from gas to liquid).

[0038] The "vicinity" refers to the upstream surface of the blade 61 of the inducer 6 and the area around the surface of the blade 61. In other words, the vicinity of the blade 61 is the area around the blade 61 of the inducer 6 where cavitation may occur.

[0039] The "main flow" is the main flow of the handled liquid flowing inside the suction pipe 7. The main flow is generated by the rotation of the impeller 4 and the inducer 6. The main flow is the flow of the handled liquid that swirls due to the rotation of the impeller 4 and the inducer 6 and flows along the axial direction of the suction pipe 7.

[0040] "Backflow" is a flow in the opposite direction to the main flow of the pumped liquid flowing through the suction pipe 7. Backflow mainly occurs upstream of the inducer 6, along the inner circumferential surface 71. That is, backflow occurs along the upstream inner circumferential surface 72. Backflow can occur due to a pressure difference between the upstream side of the inducer 6 and the downstream side of the inducer 6. When a flow of the pumped liquid occurs due to the rotation of the inducer 6, the pressure upstream of the inducer 6 decreases and the pressure downstream of the inducer 6 increases. This pressure difference causes backflow. Backflow can mainly occur in the backflow region BA.

[0041] The backflow area BA is the main area within the suction pipe 7 where backflow can occur.

[0042] Generally, the inducer 6 is designed to have an optimal shape to match the diameter of the suction pipe 7. The optimal shape of the inducer 6 is designed depending on the rotation speed of the impeller 4, the discharge rate (flow rate) of the pumped liquid, and other factors. The flow rate of the pumped liquid flowing through the suction pipe 7 is increased as the inducer 6 rotates, causing the pumped liquid to swirl. The flow rate of the pumped liquid is further increased near the blades 61 of the inducer 6, causing the pressure of the pumped liquid to decrease. Here, a backflow occurs near the end 74 of the rotating inducer 6. Cavitation can occur when the main flow and the backflow interact with each other, causing a drop in the pressure of the pumped liquid. Cavitation is particularly likely to occur when the pump 1 is operated under conditions other than the set rotation speed and discharge rate.

[0043] 3 shows the state of cavitation occurring near the blades 61 of the inducer 6 as viewed from the upstream side of the flow under the same operating conditions. This figure compares the amount of cavitation with and without the uneven surface 8.

[0044] The comparative example in the same figure shows the state of the inducer blades of a conventional centrifugal pump. The comparative example in the same figure shows a state in which a large amount of cavitation occurs near the inducer blades. The comparative example in the same figure shows a state in which cavitation occurs, covering about two-thirds of the inducer blade surface.

[0045] 3 shows the blades 61 of the inducer 6 in which the uneven surface 8 is arranged on the upstream inner circumferential surface 72 of the suction pipe 7. The example in the figure shows a state in which a small amount of cavitation occurs near the blades 61 of the inducer 6. The example in the figure shows a state in which cavitation occurs, covering about one-sixth of the surface of the blades 61 of the inducer 6.

[0046] Relationship Between the Uneven Surface 8 and Cavitation Next, the relationship between the uneven surface 8 of the pump 1 and cavitation will be described.

[0047] 6 is a schematic diagram showing the pressure distribution and flow of the pumped fluid generated by the rotation of the inducer 6 of the pump 1. In the figure, the pressure region is indicated by a dashed line, and the flow of the pumped fluid is indicated by arrows.

[0048] This pump 1 is provided with an uneven surface 8 in an arrangement region 73 of an upstream inner circumferential surface 72 of the suction pipe 7, which is located upstream of the inducer 6 in the flow direction. The uneven surface 8 has a predetermined axial length. A main flow of the pumped liquid generated by the rotation of the inducer 6 swirls and flows along the axial direction of the suction pipe 7. The swirling flow of the pumped liquid is called a swirling flow. Part of the swirling flow flows toward the inducer 6 while swirling along the inner circumferential surface 71. That is, part of the main flow flows onto the uneven surface 8. The main flow flowing onto the uneven surface 8 forms a vortex following the shape of the uneven surface 8.

[0049] The vortex is a flow of the treated fluid that flows along the shape of the uneven surface 8. The vortex includes flows in multiple directions. The vortex collides with the backflow, thereby inhibiting the flow (growth) of the backflow. In other words, the vortex can suppress the expansion of the region where the backflow is occurring (backflow region BA) toward the upstream side.

[0050] The vortex interferes with the main flow and disturbs part of the main flow. That is, the vortex generates turbulence in part of the main flow. When a part of the main flow is disturbed by the vortex, the flow velocity of the main flow decreases. As a result, the pressure drop near the blades 61 of the inducer 6 is suppressed. That is, the uneven surface 8 suppresses the pressure drop of the handled liquid, thereby suppressing the occurrence of cavitation.

[0051] The uneven surface 8 in the pump 1 reduces cavitation that occurs near the blades 61 of the inducer 6. The reduced cavitation in the pump 1 can suppress a decrease in the suction performance of the pump 1. In other words, the pump 1 can suppress the proportion of a decrease in head among the inherent performance of the pump 1. The pump 1 can reduce vibration, noise, and fatigue damage of the inducer 6 that are caused by cavitation.

[0052] Modification (1) Next, a modification of the uneven surface 8 of the pump 1 will be described. In the modification, the shape of the uneven surface 8 differs from that of the previously described embodiment (first embodiment). In the following modification, reference will be made to Figures 1 to 6 as appropriate.

[0053] Fig. 7 is a list of patterns of the uneven surface 8. The list shows the pattern shape, diameter, depth, surface unevenness, pattern arrangement, and axial length of each of 12 types of patterns of the uneven surface 8. Fig. 8 is a schematic diagram showing the pattern shape of the uneven surface 8 shown in Fig. 7.

[0054] The 12 types of uneven surfaces 8 shown in Fig. 7 are compared with a comparative example (Base). The 12 types of uneven surfaces 8 are identified by numbers No. 1 to No. 12. The uneven surface 8 of the first embodiment corresponds to No. 4.

[0055] The main features of the uneven surface 8 of each of the modified examples (No. 1 to No. 5) are 0.5 mm, 1 mm, 2 mm, 4 mm, and 8 mm (each indicating a diameter). The main features of the uneven surface 8 of each of the modified examples (No. 6 to No. 9) are 4 mm Deep, 4 mm Protrusion, 4 mm Row, and 4 mm Wide. The main features of the uneven surface 8 of each of the modified examples (No. 10 to No. 12) are Triangle, Square, and Square B. Base is a comparative example.

[0056] The pattern shape is the shape of the recesses or protrusions of the uneven surface 8. As shown in Fig. 8, A indicates a hemispherical shape, B indicates a triangular prism shape, C indicates a diamond shape, and D indicates a quadrangular prism shape.

[0057] The diameter indicates the size of the recesses or protrusions of the uneven surface 8. The diameter is expressed in millimeters. The diameter is based on the size of a square having vertical and horizontal lengths. That is, the diameter is the vertical and horizontal size of a circle for a hemispherical shape (A), an equilateral triangle for a triangular prism shape (B), a diamond shape (C), and a rectangle for a rectangular prism shape (D). For example, a diameter of 4 mm for a circle indicates that the pattern fits exactly within a circle with a diameter of 4 mm. An equilateral triangle of 4 mm and a diamond of 4 mm indicate that the pattern fits exactly within a square with 4 mm length and width. A rectangle of 4 mm indicates that the pattern is a square with 4 mm length and width.

[0058] The depth is the depth of the recesses and / or the height of the protrusions of the uneven surface 8. That is, the depth indicates the length from the surface of the inner circumferential surface 71 of the suction pipe 7 to the bottom of the recesses or the top of the protrusions. The depth of the recesses and / or the height of the protrusions are indicated in mm.

[0059] The unevenness of the surface indicates either a concave portion or a convex portion of the uneven surface 8. In other words, the unevenness of the surface indicates whether a concave portion protruding radially from the surface of the inner circumferential surface 71 of the suction pipe 7 is formed, or a convex portion protruding radially from the surface of the inner circumferential surface 71 of the suction pipe 7 is formed.

[0060] In the present invention, the unevenness of the surface is not limited to only recesses or protrusions, and may be, for example, a mixture of recesses and protrusions.

[0061] The pattern arrangement indicates whether multiple recesses or multiple protrusions are arranged alternately or side by side in the axial direction of the suction pipe 7. The alternate arrangement indicates that multiple recesses or multiple protrusions are arranged alternately in the axial direction of the suction pipe 7. The row arrangement indicates that multiple recesses or multiple protrusions are arranged in a row (series) in the axial direction of the suction pipe 7.

[0062] The axial length indicates the axial length of the uneven surface 8. That is, the axial length is the axial length of the arrangement region 73 of the suction pipe 7. The axial length is set to 20 mm for the single length and 40 mm for the double length.

[0063] Basic operating environment of the pump 1 Next, the basic operating environment of the pump 1 will be described. In this embodiment, the diameter of the inducer 6 of the pump 1 is 125.3 mm. The inner diameter (diameter) of the suction pipe 7 in which the inducer 6 is arranged is 127 mm. The handled liquid flowing through the suction pipe 7 is water. The temperature of the water is set to 25°C. The density of water is 997 kg / m ３ The dynamic viscosity of water is 0.0008899 kg / (m·s). The rotation speed of the inducer 6 is set to 3000 rpm. The inlet condition is static pressure, and the outlet condition is set as mass flow rate.

[0064] Relationship between Modifications and Cavitation (1) Next, the relationship between modifications of the uneven surface 8 of the pump 1 and cavitation will be described.

[0065] 9 is a schematic diagram of cavitation occurring near the blades 61 of the inducer 6 for each of the modified examples shown in FIG. 7, as viewed from the upstream side of the flow. The figure shows the state of cavitation occurring near the blades 61 of the inducer 6, as viewed from the upstream side of the flow. The figure shows the difference in the amount of cavitation (plan view) between the comparative example and the case with and without the uneven surface 8.

[0066] The comparative example shown in the figure shows the state of cavitation near the vanes of the inducer provided in a conventional pump. The modified examples (No. 1 to No. 12) in the figure show the state of cavitation near the vanes 61 of the inducer 6 when operated under the same operating conditions as the conventional pump. The inlet pressure in the figure is -0.07 MPa.

[0067] The figure shows that, compared to the comparative example, the modified examples (No. 1 to No. 12) can reduce the amount of cavitation generated near the blades 61 of the inducer 6. The figure also shows that the effect of reducing the amount of cavitation by each of the modified examples (No. 1 to No. 12) of the uneven surface 8 is almost the same.

[0068] Next, the cavitation volume for each of the modified examples (No. 1 to No. 12) will be explained.

[0069] FIG. 10 is a graph showing the volume of cavitation for each of the modified examples shown in FIG. 7. The graph shows the modified examples (No. 1 to No. 12). In the graph, the horizontal axis shows each example, and the vertical axis shows the volume of generated cavitation (cm ３ The inlet pressure in this figure is -0.07 MPa.

[0070] The modified examples (No. 1 to No. 5) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example (Base). The modified examples (No. 1 to No. 3) can reduce the volume of cavitation more than the modified examples (No. 4, No. 5). That is, in the modified examples (No. 1 to No. 5), the uneven surface 8 with a small diameter can reduce the generation of cavitation more than the uneven surface 8 with a large diameter. Of the modified examples (No. 1 to No. 5), the modified examples (No. 1 to No. 3) can efficiently reduce the generation of cavitation.

[0071] The modified examples (No. 6 to No. 9) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example (Base). The modified example (No. 6) can reduce the volume of cavitation compared to the modified example (No. 7). That is, the concave portions of the uneven surface 8 can reduce the occurrence of cavitation compared to the convex portions of the uneven surface 8. There is no significant difference in the volume of cavitation between the modified example (No. 8) and the modified example (No. 9). That is, the difference in the volume of cavitation due to differences in the arrangement of the arrangement region 73 provided on the uneven surface 8 is small.

[0072] The modified examples (No. 10 to No. 12) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example (Base). There is no significant difference in the volume of cavitation among the modified examples (No. 10), (No. 11), and (No. 12). In other words, the difference in the volume of cavitation due to the pattern shape of the uneven surface 8 is slight.

[0073] As described above, the modified examples (No. 1 to No. 12) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example. That is, Fig. 10 shows that the amount of cavitation generated near the blades 61 of the inducer 6 can be reduced.

[0074] Next, the head capacity of the pump 1 for each of the modified examples (No. 1 to No. 12) will be explained.

[0075] FIG. 11 is a line graph showing the head capacity of the present pump 1 for each of the modified examples shown in FIG. 7 . This graph shows the same for modified examples (No. 1 to No. 5) among the modified examples (No. 1 to No. 12). FIG. 12 is a line graph showing the same for modified examples (No. 6 to No. 9) among the modified examples (No. 1 to No. 12). FIG. 13 is a line graph showing the same for modified examples (No. 10 to No. 12) among the modified examples (No. 1 to No. 12) among the modified examples (No. 1 to No. 12). In FIGS. 11 to 13 , the horizontal axis shows the inlet pressure (MPa) of the pumped liquid in the suction pipe 7, and the vertical axis shows the head capacity (m) of the present pump 1.

[0076] In FIG. 11, the modified examples (No. 1 to No. 5) do not cause a large reduction in the head capacity of the pump 1 in any pressure range, compared to the comparative example (Base).

[0077] In FIG. 12, the modified examples (No. 6 to No. 9) do not cause a large reduction in the head capacity of the pump 1 in any pressure range, compared to the comparative example (Base).

[0078] In FIG. 13, the modified examples (No. 10 to No. 12) do not cause a large reduction in the head capacity of the pump 1 in any pressure range, compared to the comparative example (Base).

[0079] As described above, the modified examples (No. 1 to No. 12) can suppress a decrease in the head capacity of the pump 1 in any pressure range compared to the comparative example. In other words, Figures 11 to 13 show that the head capacity of the pump 1 for each of the modified examples (No. 1 to No. 12) of the uneven surface 8 is approximately the same.

[0080] Next, the rate of decrease in the head capacity of the pump 1 for each of the modified examples (No. 1 to No. 12) will be explained.

[0081] Figure 14 is a graph showing the percentage reduction in the head capacity of the pump 1 for each of the modified examples shown in Figure 7. The graph shows the modified examples (No. 1 to No. 12). In the graph, the horizontal axis shows each example, and the vertical axis shows the percentage reduction in the head capacity of the pump 1. The inlet pressure in the graph is -0.07 MPa.

[0082] Compared to the comparative example (Base), the modified examples (No. 1 to No. 5) can reduce the rate of decrease in the head capacity of the pump 1. The difference in head capacity between the modified examples (No. 1 to No. 5) of the uneven surface 8 is small.

[0083] Compared to the comparative example (Base), the modified examples (No. 6 to No. 9) can reduce the rate of decrease in the head capacity of the pump 1. The difference in head capacity between the modified examples (No. 6 to No. 9) of the uneven surface 8 is small.

[0084] Compared to the comparative example (Base), the modified examples (No. 10 to No. 12) can reduce the rate of decrease in the head capacity of the pump 1. The difference in head capacity between the modified examples (No. 10 to No. 12) of the uneven surface 8 is slight.

[0085] As described above, the variations (No. 1 to No. 12) can reduce the rate of decrease in the head capacity of the pump 1 compared to the comparative example. The figure shows that the head capacity of the pump 1 for each of the variations (No. 1 to No. 12) of the uneven surface 8 is approximately the same.

[0086] Summary (1) According to the embodiment described above, the pump 1 includes a rotating shaft 3, an impeller 4 attached to the rotating shaft 3 to suck in pumped liquid, an inducer 6 located upstream of the impeller 4 in the flow of pumped liquid, and a suction pipe 7 that houses the inducer 6 and introduces pumped liquid into the impeller 4 and the inducer 6. The suction pipe 7 includes a cylindrical inner circumferential surface 71. The inner circumferential surface 71 includes at least one uneven surface 8 having a plurality of recesses and / or a plurality of protrusions. The uneven surface 8 is located on an upstream inner circumferential surface 72 of the inner circumferential surface 71 that is located upstream of the inducer 6 in the flow. With this configuration, a portion of the main flow flows onto the uneven surface 8. The main flow that flows onto the uneven surface 8 forms a vortex along the shape of the uneven surface 8. The vortex collides with the backflow, inhibiting the flow (growth) of the backflow. The vortex interferes with the main flow, disrupting a portion of the main flow. When a part of the main flow is disturbed by a vortex, the flow velocity of the main flow decreases, which suppresses a decrease in pressure near the blades 61 of the inducer 6. In other words, the pump 1 can reduce cavitation occurring near the blades 61.

[0087] In the embodiment described above, the uneven surface 8 is arranged in an annular shape in the circumferential direction of the inner circumferential surface 71. This configuration suppresses a decrease in pressure near the vanes 61 of the inducer 6 in the circumferential direction of the inner circumferential surface 71. In other words, the pump 1 can reduce cavitation occurring near the vanes 61.

[0088] Furthermore, according to the embodiment described above, the uneven surface 8 is disposed on the end 74 of the upstream inner circumferential surface 72 on the inducer 6 side. This configuration allows the pump 1 to reduce the backflow area BA where backflow occurs. As a result, the pump 1 can reduce cavitation occurring near the blades 61.

[0089] Furthermore, according to the embodiment described above, the uneven surface 8 is arranged on the upstream inner circumferential surface 72 in a cylindrical shape having a predetermined length from the end 74 toward the upstream side of the flow. With this configuration, the uneven surface 8 of the present pump 1 disturbs part of the flow of the mainstream, thereby reducing the flow velocity of the mainstream. As a result, a decrease in pressure near the vanes 61 of the inducer 6 is suppressed. In other words, the present pump 1 can reduce cavitation occurring near the vanes 61.

[0090] Furthermore, according to the embodiment described above, the uneven surface 8 is positioned to disrupt the swirling flow of pumped fluid in the suction pipe 7 that swirls along the inner circumferential surface 71 toward the inducer 6 when the pumped fluid is being sucked into the impeller 4. With this configuration, the vortex generated by the uneven surface 8 disrupts part of the main flow, reducing the flow velocity of the main flow. As a result, a decrease in pressure near the vanes 61 of the inducer 6 is suppressed. In other words, the pump 1 can reduce cavitation that occurs near the vanes 61.

[0091] Second Embodiment Configuration of the Pump (2) Another embodiment of the pump 1A (hereinafter referred to as the "second embodiment") will be described below, focusing on the differences from the first embodiment described above. In the following description of the second embodiment, for ease of explanation, the same components as those in the first embodiment and components having common functions are assigned the same reference numerals as those in the first embodiment. In the following description of the second embodiment, reference will be made to Figures 1 to 6 as appropriate.

[0092] The second embodiment differs from the first embodiment in that a non-convex / concave surface N is provided in the arrangement region 73 in the circumferential direction of the inner circumferential surface 71. The non-concave / convex surface N is a surface that does not have any concave or convex portions. In other words, the non-concave / convex surface N is a surface that does not have any concave or convex portions in the arrangement region 73.

[0093] In the present pump 1A, the uneven surfaces 8 and the non-uneven surfaces N are arranged in the arrangement region 73. The arrangement region 73 arranges a plurality of uneven surfaces 8 in the circumferential direction of the inner circumferential surface 71. The arrangement region 73 arranges the non-uneven surfaces N between adjacent uneven surfaces 8 in the circumferential direction of the inner circumferential surface 71. That is, the arrangement region 73 arranges the uneven surfaces 8 and the non-uneven surfaces N alternately in the circumferential direction of the inner circumferential surface 71. In other words, the plurality of uneven surfaces 8 are arranged intermittently in the circumferential direction of the inner circumferential surface 71. In the second embodiment, the uneven surfaces 8 and the non-uneven surfaces N are arranged alternately in 1 / 8 units in the circumferential direction of the arrangement region 73.

[0094] The pump 1A can suppress the rate of head reduction of the pump 1A compared to the pump 1 having the annularly arranged uneven surface 8. In other words, the pump 1A suppresses the reduction in suction performance. In addition, the pump 1A can reduce cavitation occurring near the blades 61 of the inducer 6 of the pump 1A.

[0095] Modification (2) Next, a modification of the uneven surface 8 of the pump 1A will be described. In this modification, the shape of the uneven surface 8 differs from that of the second embodiment. In the following modification, FIG. 8 will be referred to as appropriate.

[0096] Fig. 15 is a list of patterns of the uneven surface 8. The list shows the pattern arrangement, pattern shape, diameter, depth, surface unevenness, and axial length for each of eight types of patterns of the uneven surface 8. Fig. 16 is a schematic diagram showing the shape of each pattern arrangement of the uneven surface 8 shown in Fig. 15.

[0097] The eight types of uneven surfaces 8 shown in Fig. 15 are compared with a comparative example (Base). The eight types of uneven surfaces 8 are identified by numbers No. 13 to No. 20. The uneven surface 8 of the second embodiment corresponds to No. 18.

[0098] The main features of the uneven surface 8 of each of the modified examples (No. 13 to No. 18) are 1 mm Dense, 1 mm Random, 1 mm Axial, 1 mm Vertical, 1 mm Half, and 1 mm 1 / 8. The main features of the uneven surface 8 of each of the modified examples (No. 19 and No. 20) are 1 mm 1 Line, 1 mm Gap 10 mm.

[0099] The pattern arrangement differs in the arrangement of recesses on the uneven surface 8. The pattern arrangement includes eight types of arrangements. The types are 1 mm Dense (Type A), 1 mm Random (Type B), 1 mm Axial (Type C), 1 mm Vertical (Type D), 1 mm Half (Type E), 1 mm 1 / 8 (Type F), 1 mm 1 Line (Type G), and 1 mm Gap 10 mm (Type H).

[0100] The pattern shape of each type (Type A to Type H) is a hemispherical shape (A) (see FIG. 8). The diameter of the pattern shape is 1 mm. The depth of the pattern shape is 0.5 mm. The uneven surface 8 of the pattern shape is concave. The axial length of the arrangement region 73 provided on the uneven surface 8 is 20 mm (1x).

[0101] The basic operating environment of the pump 1A is the same as that of the pump 1 of the first embodiment.

[0102] Relationship between Modifications and Cavitation (2) Next, the relationship between modifications of the uneven surface 8 provided in the pump 1A according to the present invention and cavitation will be described.

[0103] Fig. 17 is a schematic diagram of cavitation occurring near the blades 61 of the inducer 6 for each of the modified examples (No. 13 to No. 20) shown in Fig. 15, as viewed from the upstream side of the flow. The figure shows the state in which cavitation occurs near the blades 61 of the inducer 6, as viewed from the upstream side of the flow. The figure shows the difference in the amount of cavitation (plan view) between the comparative example and the case with and without the uneven surface 8.

[0104] The comparative example shown in the figure shows the state of cavitation near the vanes of the inducer provided in a conventional pump. The modified examples (No. 13 to No. 20) in the figure show the state of cavitation near the vanes 61 of the inducer 6 when operated under the same operating conditions as the conventional pump. The inlet pressure in the figure is -0.07 MPa.

[0105] The figure shows that, compared to the comparative example, the modified examples (Nos. 13 to 20) can reduce the amount of cavitation generated near the blades 61 of the inducer 6. The figure also shows that the effect of reducing the amount of cavitation by each of the modified examples (Nos. 13 to 20) of the uneven surface 8 is almost the same.

[0106] Next, the cavitation volume for each of the modified examples (No. 13 to No. 20) will be explained.

[0107] Fig. 18 is a graph showing the volume of cavitation for each of the modified examples shown in Fig. 15. This graph shows the modified examples (No. 13 to No. 20). In this graph, the horizontal axis shows each example, and the vertical axis shows the volume of generated cavitation (cm ３ The inlet pressure in this figure is -0.07 MPa.

[0108] The modified examples (No. 13 to No. 18) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example (Base). There is no significant difference in the volume of cavitation between the modified example (No. 13) and the other modified examples (No. 14 to No. 18). In other words, the difference in the volume of cavitation due to the pattern arrangement of the uneven surface 8 is slight.

[0109] The modified examples (No. 19 and No. 20) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example (Base). There is no significant difference in the volume of cavitation between the modified example (No. 19) and the modified example (No. 20). In other words, the difference in the volume of cavitation due to the pattern arrangement of the uneven surface 8 is slight.

[0110] As described above, the modified examples (Nos. 13 to 20) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example. In other words, the figure shows that it is possible to reduce the amount of cavitation generated near the blades 61 of the inducer 6. The figure also shows that the effect of reducing the amount of cavitation by each of the modified examples (Nos. 13 to 20) of the uneven surface 8 is almost the same.

[0111] Next, the head capacity (suction performance) of the pump 1A of each of the modified examples (No. 13 to No. 20) will be described.

[0112] FIG. 19 is a line graph showing the head capacity of the present pump 1A of the modified examples shown in FIG. 15. This line graph shows the same for modified examples (No. 13 to No. 18) among the modified examples (No. 13 to No. 20). FIG. 20 is a line graph showing the head capacity of the present pump 1A of each modified example shown in FIG. 15. This line graph shows the same for modified examples (No. 19, No. 20) among the modified examples (No. 13 to No. 20). In FIGS. 19 and 20, the horizontal axis shows the inlet pressure (MPa) of the pumped liquid in the suction pipe 7, and the vertical axis shows the head capacity (m) of the present pump 1A.

[0113] In FIG. 19, the modified examples (No. 13 to No. 18) do not cause a large reduction in the head capacity of the pump 1A in any pressure range, compared to the comparative example (Base).

[0114] In FIG. 20, the modified examples (No. 19, No. 20) do not cause a significant reduction in the head capacity of the pump 1A in any pressure range, compared to the comparative example (Base).

[0115] As described above, the variations (Nos. 13 to 20) can suppress a decrease in the head capacity of the pump 1A in all pressure ranges compared to the comparative example. In other words, Figures 19 and 20 show that the head capacity of the pump 1A for each of the variations (Nos. 13 to 20) of the uneven surface 8 is approximately the same.

[0116] Next, the rate of decrease in the head capacity of the pump 1A for each of the modified examples (No. 13 to No. 20) will be explained.

[0117] Figure 21 is a graph showing the percentage reduction in head capacity of the present pump 1A for each of the modified examples shown in Figure 15. This graph shows the modified examples (No. 13 to No. 20). In this graph, the horizontal axis shows each example, and the vertical axis shows the percentage reduction in head capacity of the present pump 1A. The inlet pressure in this graph is -0.07 MPa.

[0118] The modified examples (No. 13 to No. 18) can reduce the rate of decrease in the head capacity of the present pump 1A compared to the comparative example (Base). The difference in head capacity between the modified examples (No. 13 to No. 18) is small. The modified example (No. 18) reduces the rate of decrease in the head capacity of the present pump 1A compared to the other modified examples. In other words, the modified example (No. 18) particularly suppresses the decrease in head capacity.

[0119] The variations (No. 19 and No. 20) can reduce the rate of decrease in the head capacity of the present pump 1A compared to the comparative example (Base). The variation (No. 20) reduces the rate of decrease in the head capacity of the present pump 1A less than the variation (No. 19).

[0120] As described above, the variations (Nos. 13 to 20) reduce the rate of decrease in the head capacity of the pump 1A compared to the comparative example. The figure shows that the variations (Nos. 13 to 17) of the uneven surface 8 of the pump 1A have approximately the same head capacity. The figure also shows that the variation (No. 18) of the uneven surface 8 has a smaller rate of decrease in head capacity compared to the other variations (Nos. 13 to 17).

[0121] Summary (2) According to the embodiment described above, the pump 1A includes a plurality of uneven surfaces 8 arranged on the inner circumferential surface 71 in the circumferential direction of the inner circumferential surface 71, and a non-uneven surface N arranged between adjacent uneven surfaces 8. The non-uneven surface N does not have a plurality of concave portions and / or a plurality of convex portions. With this configuration, the rate of decrease in the head of the pump 1A is suppressed more than the rate of decrease in the head of the pump 1A in which the uneven surfaces 8 are arranged continuously in an annular shape.

[0122] Third Embodiment Configuration of the Pump (3) Another embodiment of the pump 1B (hereinafter referred to as the "third embodiment") will be described below, focusing on differences from the previously described embodiment. In the following description of the third embodiment, for ease of explanation, the same components as those in the previously described embodiment and components having common functions are designated by the same reference numerals. In the following third embodiment, reference will be made to Figures 1 to 6 as appropriate.

[0123] The third embodiment differs from the previously described embodiments in the shape of the uneven surface 8. That is, the third embodiment differs from the first embodiment in that the inner circumferential surface 71 is provided with a spiral groove formed in a spiral shape in the arrangement region 73 in the circumferential direction.

[0124] The spiral groove is a groove formed in a spiral shape from the end 74 on the inducer 6 side toward the upstream side of the flow. The spiral groove is a groove in the shape of a female screw. The spiral groove is disposed obliquely with respect to the axial direction of the suction pipe 7.

[0125] The spiral direction of the spiral groove is opposite to the swirling direction of the swirling flow of the treated liquid in the suction pipe 7, which flows toward the inducer 6 while swirling along the inner circumferential surface 71. Therefore, the spiral groove is arranged so that the direction of the mainstream swirling flow and the spiral direction of the spiral groove intersect.

[0126] The spiral direction of the spiral groove may be the same as the swirling direction of the swirling flow that flows toward the inducer 6 while swirling along the inner circumferential surface.

[0127] This pump 1B has spiral grooves that are oriented in the opposite direction to the swirling direction of the swirling flow of the mainstream. Therefore, this pump 1B is prone to generating vortex flows. In other words, the spiral grooves are prone to generating turbulent flows. When turbulent flows occur, part of the mainstream flow is disturbed, and the flow velocity of the mainstream decreases. As a result, the drop in pressure near the vanes 61 of the inducer 6 is suppressed. In other words, the spiral grooves in this pump 1B suppress the drop in pressure of the pumped liquid, thereby suppressing the occurrence of cavitation.

[0128] Modification (3) Next, a modification of the uneven surface 8 of the pump 1B will be described. In this modification, the shape of the uneven surface 8 differs from that of the third embodiment.

[0129] Fig. 22 is a list of patterns of the uneven surface 8. The list shows the pattern arrangement, pattern shape, diameter (groove width), depth, surface unevenness, and axial length for each of the two types of patterns of the uneven surface 8. Fig. 23 is a schematic diagram showing the shape of each pattern arrangement of the uneven surface 8 shown in Fig. 22.

[0130] The two types of uneven surfaces 8 shown in Fig. 22 are compared with a comparative example (Base). The two types of uneven surfaces 8 are identified by numbers No. 21 and No. 22, respectively. The uneven surface 8 of the third embodiment corresponds to No. 21.

[0131] The main features of the uneven surface 8 of each of the modified examples (No. 21 and No. 22) are Spiral R and Spiral L.

[0132] The pattern arrangement differs in the arrangement of recesses on the uneven surface 8. The pattern arrangement includes two types of pattern shapes: a right-handed spiral Spiral R (Type R) and a left-handed spiral Spiral L (Type L).

[0133] The pattern shape of each type (Type R, Type L) is a spiral groove. The diameter of the pattern shape is 1 mm. The depth of the pattern shape is 0.5 mm. The uneven surface 8 of the pattern shape is concave. The axial length of the placement area 73 provided on the uneven surface 8 is 20 mm (1x).

[0134] The basic operating environment of the pump 1B is the same as that of the pump 1 of the first embodiment.

[0135] Relationship between Modifications and Cavitation (3) Next, the relationship between modifications of the uneven surface 8 provided in the pump 1B according to the present invention and cavitation will be described.

[0136] Fig. 24 is a schematic diagram of cavitation occurring near the blades 61 of the inducer 6 for each of the modified examples (No. 21 and No. 22) shown in Fig. 22, as viewed from the upstream side of the flow. The figure shows the state in which cavitation occurs near the blades 61 of the inducer 6, as viewed from the upstream side of the flow. The figure shows the difference in the amount of cavitation (plan view) between the comparative example and the case with and without the uneven surface 8.

[0137] The comparative example shown in the figure shows the state of cavitation near the vanes of the inducer provided in a conventional pump. The modified examples (No. 21 and No. 22) in the figure show the state of cavitation near the vanes 61 of the inducer 6 when operated under the same operating conditions as the conventional pump. The inlet pressure in the figure is -0.07 MPa.

[0138] The figure shows that, compared to the comparative example, the modified examples (No. 21 and No. 22) can reduce the amount of cavitation generated near the blades 61 of the inducer 6. The figure also shows that the effect of reducing the amount of cavitation by each of the modified examples (No. 21 and No. 22) of the uneven surface 8 is almost the same.

[0139] Next, the cavitation volume for each of the modified examples (No. 21, No. 22) will be explained.

[0140] Fig. 25 is a graph showing the volume of cavitation for each of the modified examples shown in Fig. 22. This graph shows the modified examples (No. 21, No. 22). In this graph, the horizontal axis shows each example, and the vertical axis shows the volume of generated cavitation (cm ３ The inlet pressure in this figure is -0.07 MPa.

[0141] The modified examples (No. 21 and No. 22) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example (Base). There is no significant difference in the volume of cavitation between the modified example (No. 21) and the modified example (No. 22). In other words, the difference in the volume of cavitation due to the pattern arrangement of the uneven surface 8 is slight.

[0142] As described above, the modified examples (No. 21 and No. 22) can reduce the volume of cavitation generated near the blades 61 of the inducer 6 compared to the comparative example. That is, the figure shows that it is possible to reduce the amount of cavitation generated near the blades 61 of the inducer 6. The figure also shows that the effect of reducing the amount of cavitation by each of the modified examples (No. 21 and No. 22) of the uneven surface 8 is almost the same.

[0143] Next, the head capacity of the pump 1B for each of the modified examples (No. 21, No. 22) will be explained.

[0144] Figure 26 is a line graph showing the head capacity of the pump 1B for each of the modified examples shown in Figure 22. This figure shows the line graph for modified examples (No. 21 and No. 22). In this figure, the horizontal axis represents the inlet pressure (MPa) of the pumped liquid in the suction pipe 7, and the vertical axis represents the head capacity (m) of the pump 1B.

[0145] The modified examples (No. 21 and No. 22) do not cause a significant reduction in the head capacity of the pump 1B in any pressure range, compared to the comparative example (Base).

[0146] As described above, the variations (Nos. 21 and 22) can suppress a decrease in the head capacity of the pump 1B in any pressure range compared to the comparative example. In other words, the figure shows that the head capacity of the pump 1B in each of the variations (Nos. 21 and 22) of the uneven surface 8 is approximately the same.

[0147] Next, the rate of decrease in the head capacity of the pump 1B for each of the modified examples (No. 21, No. 22) will be explained.

[0148] FIG. 27 is a graph showing the percentage reduction in head capacity of the pump 1B for each of the modified examples shown in FIG. 22. This graph shows modified examples (No. 21 and No. 22). The horizontal axis of this graph shows each example, and the vertical axis shows the percentage reduction in head capacity. The inlet pressure in this graph is −0.07 MPa.

[0149] The modified examples (No. 21 and No. 22) can reduce the rate of decrease in the head capacity of the pump 1B compared to the comparative example (Base).

[0150] As described above, the variations (No. 21 and No. 22) can reduce the rate of decrease in head capacity compared to the comparative example. The figure shows that the head capacity of the pump 1 for each of the variations (No. 21 and No. 22) of the uneven surface 8 is approximately the same.

[0151] Summary (3) According to the embodiment described above, the pump 1B has a helical groove formed in the uneven surface 8, spirally extending from the end 74 on the inducer 6 side toward the upstream side of the flow. This configuration efficiently turbulently disrupts a portion of the main flow, reducing the flow velocity of the main flow. As a result, a decrease in pressure near the vanes 61 of the inducer 6 is suppressed. In other words, the pump 1B can suppress the occurrence of cavitation near the vanes 61.

[0152] Other Embodiments In the present invention, the formation of the uneven surface 8 of the suction pipe 7 is not limited to molding, as long as it is possible to form multiple recesses and / or multiple protrusions. That is, for example, the uneven surface 8 may be formed by pressing or shot peening. In such cases, the uneven surface 8 is formed so that its depth (height) is 0.25 mm or more.

[0153] In the present invention, the shape of the recesses and / or protrusions of the uneven surface 8 may be any shape that can generate vortex flows. That is, for example, the shape of the recesses and / or protrusions may be polygonal, irregular (random uneven shape, shape with varying size), etc.

[0154] Furthermore, in the present invention, the size of the recesses and / or protrusions of the uneven surface 8 may be any size that can generate vortex flows. Preferably, for example, the average size of the recesses and / or protrusions in the axial and circumferential directions of the rotating shaft 3 is 0.5 mm or more and 8 mm or less.

[0155] Furthermore, in the present invention, the depth of the recesses and / or the height of the protrusions of the uneven surface 8 may be sufficient to generate vortex flows. Preferably, for example, the average depth of the recesses and / or the average height of the protrusions is 0.25 mm or more and 4 mm or less.

[0156] Embodiments of the Present Invention Next, embodiments of the present invention that can be understood from the embodiments described above will be described below, using the terms and symbols used in the embodiments.

[0157] A first embodiment of the present invention is a centrifugal pump (e.g., this pump 1) comprising: a rotating shaft (e.g., rotating shaft 3); an impeller (e.g., impeller 4) attached to the rotating shaft and sucking in a treated fluid; an inducer (e.g., inducer 6) arranged upstream of the impeller in the flow of the treated fluid; and a suction pipe (e.g., suction pipe 7) accommodating the inducer and introducing the treated fluid into the inducer and the impeller, wherein the suction pipe has a cylindrical inner circumferential surface (e.g., inner circumferential surface 71), and the inner circumferential surface has at least one uneven surface (e.g., uneven surface 8) having a plurality of recesses and / or a plurality of protrusions, and the uneven surface is arranged on an upstream inner circumferential surface (e.g., upstream inner circumferential surface 72) of the inner circumferential surface that is located upstream of the inducer in the flow of the treated fluid. According to this configuration, the centrifugal pump can reduce cavitation occurring near the blades (for example, the blades 61) of the inducer of the centrifugal pump.

[0158] A second aspect of the present invention is the centrifugal pump of the first aspect, wherein the uneven surface is arranged in an annular shape in the circumferential direction of the inner circumferential surface. With this configuration, the centrifugal pump can reduce cavitation occurring near the vanes of the inducer of the centrifugal pump.

[0159] A third aspect of the present invention is a centrifugal pump according to the first aspect, wherein the inner circumferential surface includes a plurality of the uneven surfaces arranged in a circumferential direction of the inner circumferential surface, and a non-uneven surface (e.g., a non-uneven surface N) arranged between adjacent uneven surfaces in the circumferential direction, and the non-uneven surface does not have a plurality of the recesses and / or a plurality of the protrusions. With this configuration, the centrifugal pump can suppress the rate of head reduction more than a centrifugal pump in which the uneven surfaces are arranged in an annular shape.

[0160] A fourth aspect of the present invention is the centrifugal pump according to any one of the first to third aspects, wherein the uneven surface is arranged at an end (e.g., end 74) of the upstream inner circumferential surface on the inducer side. With this configuration, the centrifugal pump can reduce a backflow region (e.g., backflow region BA) and reduce cavitation occurring near the blades of the inducer of the centrifugal pump.

[0161] A fifth aspect of the present invention is a centrifugal pump according to the fourth aspect, wherein the uneven surface is arranged on the upstream inner circumferential surface in a cylindrical shape having a predetermined length from the end toward the upstream side of the flow. According to this configuration, the uneven surface of the centrifugal pump disturbs a part of the flow of the main stream, thereby reducing the flow velocity of the main stream. Therefore, a decrease in pressure near the inducer vanes is suppressed. In other words, the centrifugal pump can reduce cavitation occurring near the inducer vanes of the centrifugal pump.

[0162] A sixth aspect of the present invention is the centrifugal pump of the first aspect, wherein an average size of the recessed portions and / or the protruding portions in the axial and circumferential directions of the rotating shaft is 0.5 mm or more and 8 mm or less. With this configuration, a vortex is formed along the shape of the uneven surface.

[0163] A seventh aspect of the present invention is the centrifugal pump of the first aspect, wherein the average depth of the recesses and / or the average height of the protrusions is 0.25 mm or more and 4 mm or less. With this configuration, a vortex is formed along the shape of the uneven surface.

[0164] An eighth aspect of the present invention is a centrifugal pump according to the first aspect, wherein the uneven surface is disposed at a position that disturbs a swirling flow of the pumped fluid in the suction pipe, the swirling flow of the pumped fluid swirling along the inner circumferential surface toward the inducer when the pumped fluid is sucked into the impeller. According to this configuration, a vortex generated by the uneven surface disturbs a portion of the main flow, reducing the flow velocity of the main flow. This suppresses a decrease in pressure near the inducer vanes. In other words, the centrifugal pump can reduce cavitation occurring near the inducer vanes of the centrifugal pump.

[0165] A ninth aspect of the present invention is a centrifugal pump according to the first aspect, wherein the uneven surface is formed by a spiral groove (for example, a spiral groove) formed in a spiral shape from the inducer-side end toward the upstream side of the flow. With this configuration, a part of the main flow is efficiently disturbed, and the flow velocity of the main flow is reduced. Therefore, a reduction in pressure near the inducer blades is suppressed. In other words, the centrifugal pump can reduce cavitation occurring near the inducer blades of the centrifugal pump.

[0166] REFERENCE SIGNS LIST 1 Centrifugal pump 2 Motor 3 Rotating shaft 4 Impeller 5 Housing 51 Pump chamber 52 Inlet 53 Outlet 6 Inducer 61 Blade 7 Suction pipe 71 Inner peripheral surface 72 Upstream inner peripheral surface 73 Arrangement area 74 End 8 Uneven surface 9 Discharge pipe N Non-uneven surface BA Backflow area

Claims

1. A centrifugal pump comprising: a rotating shaft; an impeller attached to the rotating shaft and sucking in a pumped liquid; an inducer arranged upstream of the impeller in the flow of the pumped liquid; and a suction pipe that houses the inducer and introduces the pumped liquid to the inducer and the impeller, wherein the suction pipe has a cylindrical inner circumferential surface, and the inner circumferential surface has at least one uneven surface having a plurality of recesses and / or a plurality of protrusions, and the uneven surface is arranged on an upstream inner circumferential surface of the inner circumferential surface that is located upstream of the inducer in the flow.

2. The centrifugal pump according to claim 1, wherein the uneven surface is arranged in an annular shape in the circumferential direction of the inner circumferential surface.

3. A centrifugal pump as claimed in claim 1, wherein the inner circumferential surface comprises: a plurality of the uneven surfaces arranged in the circumferential direction of the inner circumferential surface; and a non-uneven surface arranged between adjacent uneven surfaces in the circumferential direction, and the non-uneven surface does not have a plurality of the recesses and / or a plurality of the protrusions.

4. A centrifugal pump according to any one of claims 1 to 3, wherein the uneven surface is disposed on an end of the upstream inner circumferential surface on the inducer side.

5. The centrifugal pump according to claim 4, wherein the uneven surface is arranged on the upstream inner circumferential surface in a cylindrical shape having a predetermined length from the end toward the upstream side of the flow.

6. The centrifugal pump according to claim 1, wherein the average size of the recesses and / or the average size of the protrusions in the axial and circumferential directions of the rotating shaft is 0.5 mm or more and 8 mm or less.

7. The centrifugal pump according to claim 1, wherein the average depth of the recesses and / or the average height of the protrusions is 0.25 mm or more and 4 mm or less.

8. A centrifugal pump as described in claim 1, wherein the uneven surface is positioned to disturb the swirling flow of the treated liquid in the suction pipe that swirls along the inner circumferential surface and flows toward the inducer when the treated liquid is sucked into the impeller.

9. The centrifugal pump according to claim 1, wherein the uneven surface is formed by a spiral groove formed in a spiral shape from the inducer side end toward the upstream side of the flow.

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