centrifugal pump

Abstract

In a centrifugal pump equipped with an inducer, the occurrence of cavitation downstream of the inducer is suppressed. [Solution] A centrifugal pump (1) according to the present invention includes a motor (3), a rotating shaft (4), an impeller (6), an inducer (5), a housing (2), and a flow straightening member (7) disposed between the inducer and the impeller. The direction in which the inducer is disposed relative to the impeller is a first direction, and the opposite direction to the first direction is a second direction. The housing houses the inducer and includes an introduction section (22) that introduces pumped fluid toward the impeller. The introduction section has a cylindrical inner circumferential surface (22a). The flow straightening member has a first end (7c) on the first direction side and a second end (7d) on the second direction side. In the radial direction of the rotating shaft, the flow straightening member is disposed so as to protrude inward from the inner circumferential surface. In the axial direction, a first length (L1) between the first end and the inducer is equal to or greater than a second length (L2) between the second end and the impeller.

Description

[Technical Field]

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

[0002] Centrifugal pumps (hereinafter referred to as "conventional pumps") equipped with inducers to improve the suction performance of centrifugal pumps are known (see, for example, Patent Document 1). The inducer is located upstream of the impeller in the flow of the pumped liquid inside the centrifugal pump. The inducer is attached to the rotating shaft and rotates together with the impeller to pressurize the pumped liquid and send the pressurized pumped liquid to the impeller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 4,150,916 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional pumps, cavitation occurring around the inducer causes problems such as pressure fluctuations and reduced suction performance. The inventors of the present invention focused on cavitation occurring downstream of the inducer (between the impeller and inducer) and analyzed the causes of this cavitation. As a result, the inventors discovered that this cavitation is caused by so-called leakage flow.

[0005] Leakage flow is a flow of pumped fluid that leaks (reverse flows) from the gap between the impeller and the housing (wearing) toward the upstream side of the impeller. The leakage flow swirls along the inner surface of the housing (suction pipe) and reaches the inducer, blocking the flow path downstream of the inducer on the inner surface side of the housing. As a result, the flow of pumped fluid sent from the inducer is biased toward the flow path on the rotating shaft side. This promotes separation of the pumped fluid at the trailing edge of the inducer, increases the axial velocity of the pumped fluid, and reduces its pressure. As a result, cavitation occurs near the trailing edge of the inducer, and the cavitation extends toward the impeller along the rotating shaft.

[0006] An object of the present invention is to suppress the occurrence of cavitation downstream of an inducer in a centrifugal pump equipped with an inducer. [Means for solving the problem]

[0007] A centrifugal pump in one embodiment of the present invention includes a motor, a rotating shaft driven by the motor to rotate, an impeller attached to the rotating shaft and configured to suck in and discharge pumped fluid, an inducer attached to the rotating shaft and positioned upstream of the impeller in the flow of the pumped fluid, a housing accommodating the impeller and the inducer, and at least one flow straightening member positioned between the inducer and the impeller, wherein, in the axial direction of the rotating shaft, a direction in which the inducer is positioned relative to the impeller is a first direction, and a direction opposite to the first direction is a second direction, the housing accommodates a part of the rotating shaft on the first direction side and the inducer, and includes an introduction section that introduces the pumped fluid toward the impeller, the introduction section having a cylindrical inner circumferential surface, and the flow straightening member having a first end portion on the first direction side and a second end portion on the second direction side, the inner circumferential surface includes an inclined surface disposed between the flow straightening member and the impeller in the axial direction, the impeller includes a cylindrical suction port along the axial direction, and a cylindrical gap along the axial direction is defined between the housing and the suction port, a first length between the first end and the inducer in the axial direction is equal to or greater than a second length between the second end and the impeller. the law of nature , When the impeller rotates, a portion of the treated fluid discharged from the impeller flows through the gap in the first direction, causing a backflow of the treated fluid in the first direction of the impeller. The backflow is a swirling flow that flows in the rotational direction of the rotary shaft and along the inner circumferential surface from the second direction toward the first direction. The straightening member is arranged to protrude inward from the inner circumferential surface in the radial direction of the rotary shaft and to overlap with the gap as viewed in the first direction, so as to cross a portion of the virtual backflow that would occur if the straightening member were not arranged on the inner circumferential surface. The gap is arranged to pass through a center of the straightening member in the radial direction as viewed in the first direction. . [Effects of the Invention]

[0008] The present invention can suppress the occurrence of cavitation downstream of an inducer in a centrifugal pump equipped with an inducer. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of a centrifugal pump according to an embodiment of the present invention; [Figure 2] FIG. 2 is a partially enlarged cross-sectional view of the centrifugal pump at a portion A in FIG. 1. [Figure 3] 3 is a partially enlarged cross-sectional view of the centrifugal pump taken along line BB in FIG. 2. [Figure 4] FIG. 2 is a schematic development view of a small diameter portion and a flow straightening member of the centrifugal pump as viewed from the inside. [Figure 5] FIG. 1 is a schematic diagram illustrating the principle of cavitation generation. [Figure 6] FIG. 1 is an analytical diagram illustrating the principle of cavitation generation. [Figure 7] 2 is a schematic diagram showing the flow of pumped liquid inside the suction pipe portion of the centrifugal pump when the centrifugal pump is operating. FIG. [Figure 8] FIG. 2 is a schematic diagram showing analysis conditions and analysis results according to an embodiment of the present invention. [Figure 9] FIG. 10 is an isosurface analysis diagram of saturated water vapor pressure of each example. [Figure 10] FIG. 10 is a velocity vector analysis diagram of some embodiments. [Figure 11] FIG. 10 is an absolute pressure distribution analysis diagram for some examples. [Figure 12] FIG. 10 is a velocity vector analysis diagram of some alternative embodiments. [Figure 13] FIG. 10 is an absolute pressure distribution analysis diagram of some other examples. [Figure 14] FIG. 10 is a velocity vector analysis diagram of some alternative embodiments. [Figure 15]FIG. 10 is an absolute pressure distribution analysis diagram of some other examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 descriptions 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.

[0011] ●Centrifugal pump● ●Configuration of centrifugal pump 1 is a schematic cross-sectional view of a centrifugal pump according to an embodiment of the present invention, in which a portion of the centrifugal pump 1 is omitted for ease of explanation.

[0012] Centrifugal pump 1 sucks and discharges pumped liquid. Centrifugal pump 1 includes a housing 2, a motor 3, a rotating shaft 4, an inducer 5, an impeller 6, and three flow straightening members 7 (see also Figure 3). Centrifugal pump 1 is a so-called horizontal pump, in which rotating shaft 4 is arranged horizontally.

[0013] The "handled liquid" is a liquid that is handled (transported) by the centrifugal pump 1. The handled liquid is, for example, liquid fuel.

[0014] In the present invention, the handled liquid is not limited to liquid fuel, and may be, for example, water.

[0015] In the following description, the "forward direction" refers to the direction in which the inducer 5 is disposed relative to the impeller 6, and the "rearward direction" refers to the direction in which the impeller 6 is disposed relative to the inducer 5. The "axial direction" refers to the direction along the axial centerline of the rotating shaft 4 (front-rear direction). The "radial direction" refers to the radial direction of the rotating shaft 4, and the "circumferential direction" refers to the circumferential direction of the rotating shaft 4. The "inward direction" refers to the direction toward the center of the rotating shaft 4 in the radial direction, and the "outward direction" refers to the direction opposite the inward direction. The "upstream side" refers to the upstream side in the flow of the treated fluid inside the casing 2, and the "downstream side" refers to the downstream side in the flow of the treated fluid inside the casing 2. The "rotation direction RD (see Figure 3; the same applies below)" refers to the direction in which the rotating shaft 4 rotates, and in this embodiment, it is the counterclockwise direction when viewed from the front. The forward direction is an example of the first direction in the present invention, and the rearward direction is an example of the second direction in the present invention.

[0016] The housing 2 accommodates the motor 3, the rotary shaft 4, the inducer 5, the impeller 6, and three straightening members 7. The housing 2 includes a pump chamber 21, a suction pipe section 22, a discharge pipe section 23, and a wear ring 24.

[0017] FIG. 2 is a partially enlarged cross-sectional view of the centrifugal pump 1 at a portion A in FIG. In the following description, FIG. 1 will be referred to together with FIG. 2 as appropriate.

[0018] The pump chamber 21 accommodates the impeller 6. The pump chamber 21 includes a first inner surface 21a and a second inner surface 21b.

[0019] The first inner surface 21a is a surface facing rearward among the inner surfaces of the pump chamber 21. The first inner surface 21a is disposed in front of the impeller 6 (a front shroud 62 described later) and faces the impeller 6 (front shroud 62). The shape of the first inner surface 21a is, for example, a curved surface that is recessed in a substantially truncated cone shape facing forward so as to follow the shape of the impeller 6.

[0020] The second inner surface 21b is a surface facing inward among the inner surfaces of the pump chamber 21. The second inner surface 21b is disposed adjacent to the first inner surface 21a and in front of the first inner surface 21a. The shape of the second inner surface 21b is, for example, cylindrical.

[0021] The suction pipe section 22 guides the pumped liquid to the impeller 6. The front end of the housing 2 extends forward in a generally cylindrical shape so as to be coaxial with the rotary shaft 4, thereby forming the suction pipe section 22. The suction pipe section 22 has an inner circumferential surface 22a. The suction pipe section 22 is an example of an introduction section according to the present invention.

[0022] The inner circumferential surface 22a is disposed adjacent to the pump chamber 21 and in front of the pump chamber 21. The inner circumferential surface 22a has a generally two-stage cylindrical shape along the axial direction. The inner circumferential surface 22a includes a large diameter portion 22b, a small diameter portion 22c, a first inclined portion 22d, and a second inclined portion 22e.

[0023] The large diameter portion 22b and the small diameter portion 22c are cylindrical in shape. The inner diameter of the large diameter portion 22b is larger than the inner diameter of the small diameter portion 22c. The large diameter portion 22b is disposed forward of the small diameter portion 22c. The first inclined portion 22d is shaped like a truncated cone. That is, the first inclined portion 22d is an inclined surface whose inner diameter decreases from the front end to the rear end of the first inclined portion 22d. The first inclined portion 22d is disposed between the large diameter portion 22b and the small diameter portion 22c, adjacent to each of the large diameter portion 22b and the small diameter portion 22c. The second inclined portion 22e is shaped like a truncated cone. That is, the second inclined portion 22e is an inclined surface whose inner diameter decreases from the front end to the rear end of the second inclined portion 22e. The second inclined portion 22e is disposed between the small diameter portion 22c and the pump chamber 21 (the second inner surface 21b) and adjacent to the small diameter portion 22c and the pump chamber 21.

[0024] The discharge pipe section 23 guides the handled fluid discharged from the impeller 6 to the outside of the centrifugal pump 1. A part of the housing 2 located outward from the impeller 6 extends in the tangential direction of the impeller 6 when viewed in the axial direction, forming the discharge pipe section 23.

[0025] The wear ring 24 protects the housing 2 (second inner surface 21b). The shape of the wear ring 24 is cylindrical. The inner diameter of the wear ring 24 is the same as the inner diameter of the rear end of the second inclined portion 22e. The wear ring 24 is attached to the second inner surface 21b.

[0026] The motor 3 is driven at a predetermined drive voltage and drive frequency to rotate the rotary shaft 4 and the impeller 6. The motor 3 is a known motor that includes a rotor (not shown) attached to the rotary shaft 4 and a stator (not shown) that rotates the rotor.

[0027] The rotating shaft 4 is attached to the motor 3 and rotates when driven by the motor 3. The rotating shaft 4 transmits rotational power to the inducer 5 and the impeller 6, causing them to rotate. The rotating shaft 4 is cylindrical in shape. A front portion 4a of the rotating shaft 4 protrudes into the pump chamber 21 and the suction pipe portion 22.

[0028] The inducer 5 pressurizes the pumped liquid to assist the impeller 6 in suctioning the pumped liquid. The inducer 5 is, for example, a known inducer. The inducer 5 includes a hub portion 51 attached to the rotating shaft 4 and inducer blades 52 arranged on the outer peripheral surface of the hub portion 51. The inducer 5 is attached to the front portion 4a (front end portion) of the rotating shaft 4. The inducer 5 is housed in the large diameter portion 22b and the first inclined portion 22d (suction pipe portion 22). In other words, the inducer 5 is arranged upstream of the impeller 6. In other words, the inducer 5 is arranged axially forward of the impeller 6.

[0029] The impeller 6 sucks in and discharges the pumped liquid. The impeller 6 is attached to the front part 4a of the rotary shaft 4 and is housed in the pump chamber 21. The impeller 6 is a known closed-type impeller. The impeller 6 includes a plurality of blades 61, a front shroud 62, a rear shroud 63, a suction port 64, and a discharge port 65.

[0030] The vanes 61 rotate together with the rotary shaft 4, and guide the treated fluid sucked from the suction port 64 to the discharge port 65. The vanes 61 are disposed between a front shroud 62 and a rear shroud 63.

[0031] The front shroud 62 is a plate (so-called side plate) that covers the front of the blades 61. The front shroud 62 is shaped like a ring plate, with the inner edge being more convex forward than the outer edge. In the axial direction, the front shroud 62 faces the first inner surface 21a.

[0032] The rear shroud 63 is a plate (so-called main plate) that covers the rear side of the blades 61. The rear shroud 63 has a ring-shaped plate shape.

[0033] The suction port 64 is an inlet for the treated liquid to flow into the inside of the impeller 6. The inner edge of the front shroud 62 extends cylindrically forward so as to be coaxial with the rotary shaft 4, thereby forming the suction port 64. That is, the suction port 64 is disposed adjacent to the front shroud 62 in the forward direction of the front shroud 62. The shape of the suction port 64 is cylindrical and extends along the axial direction. The suction port 64 faces the wear ring 24 in the radial direction.

[0034] The discharge port 65 is an outlet for the handled liquid flowing inside the impeller 6. The discharge port 65 is disposed on the outer edge of the impeller 6.

[0035] FIG. 3 is a partially enlarged cross-sectional view of the centrifugal pump 1 taken along line BB in FIG.

[0036] FIG. 4 is a schematic development view of the small diameter portion 22c and the flow regulating member 7 as viewed in the inward direction. In the figure, for ease of explanation, the inducer 5 and the impeller 6 (suction port 64) are also shown by two-dot chain lines. Also, in the figure, for ease of explanation, a virtual leakage flow VFL in the case where the flow straightening member 7 is not disposed on the inner circumferential surface 22a is also shown by a thick two-dot chain arrow. Furthermore, in the figure, the flow straightening member 7 is shown colored gray. In the following description, Figures 1 to 3 will be referred to, along with Figure 4, as appropriate.

[0037] The flow straightening member 7 straightens the flow of the treated liquid inside the suction pipe 22 (disturbing the leakage flow FL (see FIG. 7; the same applies below) described later), thereby suppressing the occurrence of cavitation CB (see FIG. 5; the same applies below) downstream of the inducer 5. The flow straightening member 7 has an arc shape that follows the inner circumferential surface 22a (small diameter portion 22c) when viewed from the front, and a flat plate shape when viewed from the radial direction. A portion of the small diameter portion 22c (inner circumferential surface 22a) extends inward in a flat plate shape to form the flow straightening member 7. That is, the flow straightening member 7 protrudes inward from the small diameter portion 22c (inner circumferential surface 22a). That is, the flow straightening member 7 is housed in the small diameter portion 22c and is disposed between the inducer 5 and the impeller 6. The flow straightening member 7 has a first surface 7a, a second surface 7b, a third surface 7c, a fourth surface 7d, and a fifth surface 7e. In the following description, when the flow rectifying members 7 are to be particularly distinguished from one another, the reference numerals "1" to "3" are added after the reference numeral "7" attached to each flow rectifying member 7.

[0038] The "leakage flow FL" is a backflow of the handled fluid that occurs when a portion of the handled fluid discharged from the impeller 6 flows into the gap S1 between the first inner surface 21a and the front shroud 62 and flows forward from the gap S2 between the wear ring 24 and the suction port 64. The leakage flow FL is a swirling flow that flows in the rotation direction RD, from the rearward direction to the forward direction, along the inner circumferential surface 22a.

[0039] The flow regulating members 71 to 73 have the same shape.

[0040] The first surface 7a is a surface that faces the rotation direction RD of the rotary shaft 4. The first surface 7a has a flat shape.

[0041] The second surface 7b is a surface that faces in the opposite direction to the rotation direction RD of the rotary shaft 4. The second surface 7b has a planar shape that is parallel to the first surface 7a.

[0042] The third surface 7c is a surface facing forward. The third surface 7c has a planar shape extending along the radial direction. The third surface 7c is disposed on the most forward side of the flow straightening member 7. That is, in the axial direction, the third surface 7c is disposed at the same position as the front end of the small diameter portion 22c. The third surface 7c is an example of a first end portion according to the present invention.

[0043] The fourth surface 7d is a surface facing rearward. The shape of the fourth surface 7d is a flat surface along the radial direction. The fourth surface 7d is located at the rearmost side of the flow straightening member 7. That is, in the axial direction, the fourth surface 7d is located at the same position as the rear end of the small diameter portion 22c. The fourth surface 7d is an example of a second end portion according to the present invention.

[0044] The fifth surface 7e is a surface facing inward and has a curved shape along the axial and circumferential directions.

[0045] The flow straightening members 7 are arranged evenly in the circumferential direction. Specifically, in the rotational direction RD, the flow straightening members 7 are arranged in the order of flow straightening member 71, flow straightening member 72, and flow straightening member 73. The flow straightening members 7 are arranged so as to cross (disturb) a virtual leakage flow VFL, which will be described later.

[0046] In the present invention, the number of rectifying members 7 is not limited to three, as will be explained in the embodiments described later.

[0047] In the axial direction, the length between the third surface 7c of the flow straightening member 7 and the trailing edge 52a of the inducer vane 52 (hereinafter referred to as the "first length L1") is longer than the length between the fourth surface 7d of the flow straightening member 7 and the front end 64a of the suction port 64 of the impeller 6 (hereinafter referred to as the "second length L2"). In other words, in the axial direction, the flow straightening member 7 is disposed so as to be closer to the impeller 6 than to the inducer 5. In this embodiment, the first length L1 is approximately twice the second length L2. The second length L2 is the same as the length of the second inclined portion 22e in the axial direction.

[0048] In the present invention, the first length L1 may be equal to or greater than the second length L2, and preferably may be greater than the second length L2. As the first length L1 becomes larger than the second length L2, the rectifying member 7 moves closer to the impeller 6. As will be described later, the rectifying member 7 is disposed to disturb the leakage flow FL. Therefore, as the first length L1 becomes larger than the second length L2, the rectifying member 7 becomes more likely to disturb the leakage flow FL.

[0049] The angle θ between the first surface 7a of the rectifying member 7 and an imaginary plane VF that passes through the third surface 7c (front end portion) of the rectifying member 7 and is perpendicular to the rotation shaft 4 is 20°.

[0050] In the present invention, the angle θ is not limited to 20°, as will be explained in the examples described later.

[0051] In the radial direction, the ratio of the protrusion amount LP of the flow straightening member 7 inward from the inner circumferential surface 22a to the flow path width WF of the treated fluid on a radial line of the inner circumferential surface 22a (protrusion amount LP / flow path width WF: hereinafter referred to as the "protrusion ratio") is 50%. The flow path width WF is the width (distance) in the radial direction (when viewed from the front) between the rotating shaft 4 and the inner circumferential surface 22a.

[0052] In the present invention, the protrusion ratio is not limited to 50%, as will be explained in the examples below.

[0053] The ratio (width W1 / circumference LC) of the width W1 of the straightening member 7 (the length between the first surface 7a and the second surface 7b in a direction perpendicular to the first surface 7a) to the circumference LC of the small diameter portion 22c when viewed from the front is preferably 0.5% or more and 2% or less, and more preferably 0.5% or more and 1% or less.

[0054] In the present invention, the ratio of the width W1 of the rectifying member 7 to the circumference LC of the small diameter portion 22c is not limited to this embodiment as long as the necessary width W2 of the inter-member flow path FP described below is ensured.

[0055] The ratio of the length L3 of the flow straightening member 7 in the axial direction to the circumference LC of the small diameter portion (length L3 / circumference LC) is approximately 7.0%. Here, the ratio of the length L3 to the circumference LC is preferably 1.4% or more, more preferably 2.8% or more, and even more preferably 5.6% or more.

[0056] In the axial direction, the length L3 of the rectifying member 7 is the same as the length L4 of the small diameter portion 22c. That is, the rectifying member 7 is disposed from the front end to the rear end of the small diameter portion 22c. Here, in the axial direction, the ratio of the length L4 of the small diameter portion 22c to the length L5 of the inner circumferential surface 22a (length L4 / length L5) is approximately 27%. That is, the ratio (L3 / L5) of the length L3 of the rectifying member 7 to the length L5 of the inner circumferential surface 22a is approximately 27%.

[0057] In the present invention, the length L3 of the rectifying member 7 is not limited to being the same as the length L4 of the small diameter portion 22c, as long as the rectifying member 7 can suppress the occurrence of cavitation CB. That is, for example, the length L3 of the rectifying member 7 may be different from the length L4 of the small diameter portion 22c.

[0058] Furthermore, in the present invention, the ratio (L3 / L5) of the length L3 of the straightening member 7 to the length L5 of the inner circumferential surface 22a is not limited to this embodiment as long as the straightening member 7 is positioned so that it is closer to the impeller 6 than the inducer 5.

[0059] As described above, the rectifying member 7 is disposed in the small diameter portion 22c. Therefore, when viewed from the front, the rectifying member 7 is disposed so as to overlap the gap S2 (so as to cover the gap S2 from the front). When viewed from the front, the gap S2 is disposed so as to pass through the center of the rectifying member 7 in the radial direction. That is, the position of the gap S2 in the radial direction is the same as the position of the center of the rectifying member 7. In other words, in the radial direction, the gap S2 is disposed at a position where the protrusion ratio of the rectifying member 7 is 25%.

[0060] Between adjacent rectifying members 7 in the circumferential direction, an inter-component flow path FP is formed, which guides the treated fluid sent from the inducer 5 to the impeller 6. In other words, the inter-component flow path FP is defined by the inner circumferential surface 22a (small diameter portion 22c) and two circumferentially adjacent rectifying members 7. In this manner, the centrifugal pump 1 has three inter-component flow paths FP. The width W2 of the inter-component flow path FP in the direction perpendicular to the first surface 7a is, for example, equal to or greater than the width W1 of the rectifying member 7.

[0061] ●The principle behind cavitation The cavitation CB to be suppressed in the present invention is cavitation CB that occurs between the inducer 5 and the impeller 6, i.e., on the downstream side of the inducer 5. In the following explanation, the principle of generation of the cavitation CB will be explained using as an example a conventional centrifugal pump (hereinafter referred to as the "conventional pump") that does not have a flow straightening member 7. In the following explanation of the generation principle, for convenience of explanation, the names of the components provided in the centrifugal pump 1 and the reference numerals assigned to those components will be used. The handled liquid is water. Figures 1 to 4 will be referenced as appropriate.

[0062] FIG. 5 is a schematic diagram illustrating the principle of cavitation CB generation. In the figure, an inducer flow FI, which will be described later, is indicated by a solid arrow, and a leakage flow FL is indicated by a dashed arrow.

[0063] FIG. 6 is an analytical diagram explaining the principle of cavitation CB generation. The figure shows a streamline analysis diagram of the leakage flow FL in a conventional pump, a velocity vector analysis diagram of the handled liquid, an absolute pressure distribution analysis diagram of the handled liquid, a velocity vector analysis diagram of the handled liquid near the trailing edge 52a of the inducer vane 52, and an isosurface analysis diagram at the saturated vapor pressure of water (3,170 Pa).

[0064] When a conventional pump starts operating, the inducer 5 pressurizes the pumped fluid and sends it to the impeller 6. The impeller 6 then sucks in and discharges the pumped fluid. A portion of the pumped fluid discharged from the impeller 6 flows into the gaps S1 and S2 between the impeller 6 and the pump chamber 21, generating a leakage flow FL that flows forward from the gap S2. The leakage flow FL swirls forward along the inner circumferential surface 22a and reaches the inducer 5, blocking the flow path P1 on the inner circumferential surface 22a side (the radially outward side) of the downstream flow path of the inducer 5. As a result, the flow of pumped fluid sent from the inducer 5 (hereinafter referred to as the "inducer flow FI") is biased toward the flow path P2 on the rotating shaft 4 side (the radially inward side). At this time, separation of the pumped fluid is promoted at the trailing edge 52a of the inducer vane 52, and the axial velocity of the pumped fluid in the flow path P2 increases, resulting in a decrease in the pressure of the pumped fluid. Therefore, the pressure of the handled liquid in the flow path P2 decreases. As a result, cavitation CB occurs near the trailing edge 52a of the inducer vane 52, and a phenomenon occurs in which the cavitation CB extends toward the impeller 6 along the rotating shaft 4. In other words, on the downstream side of the inducer 5, the cavitation CB occurs so as to cylindrically cover the rotating shaft 4. In the present invention, the leakage flow FL is disturbed using the straightening member 7, thereby straightening the flow of the handled liquid downstream of the inducer 5 and suppressing the generation of the cavitation CB.

[0065] ●Operation of centrifugal pump Next, the following describes the operation of the centrifugal pump 1. In the following description of the operation, reference will be made to FIGS. 1 to 5 as appropriate.

[0066] FIG. 7 is a schematic diagram showing the flow of the pumped liquid inside the suction pipe portion 22 when the centrifugal pump 1 is operating.

[0067] When the centrifugal pump 1 is operating, the inducer 5 pressurizes the pumped fluid and sends it to the impeller 6. The impeller 6 sucks the pumped fluid sent from the inducer 5 and discharges it into the pump chamber 21. The pumped fluid discharged into the pump chamber 21 is sent to the outside of the centrifugal pump 1 via the discharge pipe 23. A portion of the pumped fluid discharged into the pump chamber 21 flows into the gap S1 and generates a leakage flow FL that flows forward from the gap S2. The leakage flow FL flows forward while swirling along the inner circumferential surface 22a and reaches the straightening member 7.

[0068] As described above, the rectifying member 7 is disposed so as to cross (disturb) the virtual leakage flow VFL. Therefore, when the leakage flow FL flows into the small-diameter portion 22c, it is disturbed by the rectifying member 7. Specifically, as described below, a portion of the leakage flow FL is blocked by the rectifying member 7, and the flow direction of the leakage flow FL is changed inward so as to be guided by the rectifying member 7. Meanwhile, another portion of the leakage flow FL passes through the inter-component flow path FP and flows toward the inducer 5. At this time, the rectifying member 7 provides strong resistance to the leakage flow, attenuating the flow. Therefore, the leakage flow FL reaching the flow path P1 is suppressed compared to the conventional pump. Therefore, among the flow paths downstream of the inducer 5, blockage of the flow path P1 by the leakage flow FL is suppressed (eliminated) compared to the conventional pump. Therefore, bias of the inducer flow FI toward the flow path P2 is also suppressed. Therefore, the pressure of the treated liquid in the flow path P2 downstream of the inducer 5 increases (to be higher than the pressure at which cavitation CB occurs) compared to a conventional pump. In this way, the turbulence of the inducer flow FI caused by the leakage flow FL is suppressed by the flow straightening member 7. In other words, the flow straightening member 7 straightens the flow downstream of the inducer 5, particularly between the inducer 5 and the impeller 6, so that it approaches a state where the leakage flow FL does not occur. As a result, the generation of cavitation CB caused by the leakage flow FL downstream of the inducer 5 is suppressed compared to a conventional pump. Furthermore, even if separation of the treated liquid occurs at the trailing edge 52a of the inducer vane 52 and cavitation CB occurs near the trailing edge 52a, the pressure in the flow path P2 is high, so that the cavitation CB does not extend toward the impeller 6 along the rotation shaft 4. In this way, the present invention uses a straightening member 7 located downstream of the inducer 5 near the impeller 6 to disrupt the leakage flow FL, thereby straightening the flow of the handled liquid downstream of the inducer 5 and suppressing the occurrence of cavitation CB downstream of the inducer 5.

[0069] A portion of the inducer flow FI flows into the inter-component flow passage FP. The flow of the treated fluid that has flowed into the inter-component flow passage FP is guided to the inter-component flow passage FP. Therefore, the flow of the treated fluid immediately after leaving the inter-component flow passage FP becomes a swirling flow that is strongly influenced by the shape of the inter-component flow passage FP. If this treated fluid is sucked into the impeller 6, the performance of the impeller 6 will deteriorate. In this embodiment, a space (second inclined portion 22e) with a second axial length L2 exists between the straightening member 7 and the impeller 6. In this space, a portion of the swirling component of the swirling flow is reduced. In other words, the influence of the inter-component flow passage FP is reduced (eliminated) in the flow passage (space) between the straightening member 7 and the impeller 6. As a result, deterioration in the performance of the impeller 6 is suppressed.

[0070] ●Example● Next, simulation analysis results for the flow path from the suction pipe 22 to the pump chamber 21 of the centrifugal pump 1, when the angle θ, number, and protrusion ratio of the flow straightening members 7 are changed, are described as examples of the present invention. In the following description of the examples, the analysis software is "Ansys CFX 2023R2." The turbulence model is "SST: Shear Stress Transport." The fluid (handled liquid) is "water." The flow rate is "30%" of the rated flow rate. The rotation speed of the rotating shaft 4 is "3,000 rpm." The input pressure of the inducer 5 is "-0.083 MPa." The circumference LC is approximately 356.3 mm. In the axial direction, the length L4 is 25.0 mm, and the length L5 is 93.5 mm. In the axial direction, the length of the first inclined portion 22d is 24.5 mm, and the length of the second inclined portion 22e is 10.0 mm.

[0071] In the following description of the embodiments, reference will be made as appropriate to Figures 1 to 5. In the following description, for convenience of explanation, the same names and symbols are used for elements having the same functions as those in the previously described embodiments.

[0072] FIG. 8 is a schematic diagram showing the analysis conditions and analysis results of an example of the present invention.

[0073] FIG. 9 is an isosurface analysis diagram of the saturated water vapor pressure of water in each example. In the figure, some of the analysis results of each example are excerpted and shown.

[0074] (Analysis conditions) First, the analysis conditions shown in FIG. 8 will be explained. As mentioned above, "angle θ" is the angle between the first surface 7a and the imaginary plane VF. "Number" is the number of straightening members 7. As mentioned above, "protrusion ratio" is the ratio of the protrusion amount LP of the straightening member 7 to the flow path width WF. "Length ratio" is the ratio of the length L3 to the length L4 in the axial direction. In this example, for convenience of analysis, the position of the fourth surface 7d in the axial direction is fixed, and the position of the third surface 7c varies rearward from the front end of the small diameter portion 22c. Here, the length L4 is 25 mm, and the lengths L3 are 20 mm, 15 mm, 10 mm, and 5 mm. The "volume ratio" is the ratio ((target volume / reference volume) x 100) of the volume of cavitation CB generated in each example (hereinafter referred to as the "target volume") to the reference volume, where the volume of cavitation CB generated in the centrifugal pump 1 without the straightening member 7 is 100%. In other words, the generation of cavitation CB is more suppressed as the volume ratio approaches 0%, and is not suppressed as the volume ratio approaches 100%. Here, the "volume of cavitation CB" is shown as the volume of a mesh that is located rearward of a position 0.0079 m rearward from the trailing edge 52a of the inducer vane 52 and has a water vapor volume fraction greater than 10%. The "efficiency ratio" is the ratio ((target efficiency / reference efficiency) × 100) of the efficiency when the centrifugal pump 1 corresponding to each example is operated at its rated capacity (hereinafter referred to as the "target efficiency") to the standard efficiency, where the efficiency when the centrifugal pump 1 without the straightening member 7 is operated at its rated capacity (hereinafter referred to as the "standard efficiency") is set to 100%. In other words, the efficiency of the centrifugal pump 1 is improved when the efficiency ratio exceeds 100%, and is reduced when the efficiency ratio is below 100%. In the "Results," "◎" indicates that the volume ratio is 0% or close to 0%, and the occurrence of cavitation CB is almost completely suppressed. "◯" indicates that the volume ratio is several percent, and the occurrence of cavitation CB is sufficiently suppressed. "△" indicates that the volume ratio is several tens of percent, and the occurrence of cavitation CB is suppressed, but the suppression effect is small.

[0075] In Examples 1 to 21, the protrusion ratio was set to 50%, and the length ratio was set to 80% (20 mm). In Example 1, the angle θ was set to 5°, and the number of rectifying members 7 was set to 3. In Examples 2 to 5, the angle θ was set to 10°, and the number of rectifying members 7 was set to 1, 2, 3, and 6, respectively. In Examples 6 to 8, the angle θ was set to 20°, and the number of rectifying members 7 was set to 3, 6, and 12, respectively. In Examples 9 to 13, the angle θ was set to 30°, and the number of rectifying members 7 was set to 1, 2, 3, 6, and 12, respectively. In Example 14, the angle θ was set to 60°, and the number of rectifying members 7 was set to 12. In Examples 15 to 19, the angle θ was set to 90°, and the number of rectifying members 7 was set to 1, 2, 12, 36, and 60, respectively. In Examples 20 and 21, the angle θ is set to 120° and 150°, respectively, and the number of rectifying members 7 is set to 12.

[0076] In Examples 22 to 24, the protrusion ratio was set to 25% and the length ratio was set to 80%. In Example 22, the angle θ was set to 10° and the number of rectifying members 7 was set to 3. In Examples 23 and 24, the angle θ was set to 30° and 90°, respectively, and the number of rectifying members 7 was set to 12.

[0077] In Examples 25 to 27, the protrusion ratio was set to 75% and the length ratio was set to 80%. In Example 25, the angle θ was set to 10° and the number of rectifying members 7 was set to 3. In Examples 26 and 27, the angle θ was set to 30° and 90°, respectively, and the number of rectifying members 7 was set to 12.

[0078] In Examples 28 to 36, the protrusion ratio was set to 50%. In Examples 28 and 29, the angle θ was set to 10°, the number of rectifying members 7 was set to 1 and 2, respectively, and the length ratio was set to 60% (15 mm). In Examples 30 and 31, the angle θ was set to 30° and 90°, respectively, the number of rectifying members 7 was set to 1, and the length ratio was set to 40% (10 mm). In Examples 32 to 34, the angle θ was set to 30°, the number of rectifying members 7 was set to 1, 2, and 3, respectively, and the length ratio was set to 20% (5 mm). In Examples 35 and 36, the angle θ was set to 90°, the number of rectifying members 7 was set to 1 and 2, respectively, and the length ratio was set to 20%.

[0079] ● Changing the angle First, the analysis results when only the angle θ is changed will be explained using Examples 1, 4, 6, and 11, Examples 8, 13, 14, 17, 20, and 21, and Examples 2, 9, and 15 as examples.

[0080] FIG. 10 is a velocity vector analysis diagram of some of Examples 2, 6, 13, and 15.

[0081] FIG. 11 is an absolute pressure distribution analysis diagram of some of Examples 1, 2, 6, 13, 15, and 21.

[0082] As shown in FIGS. 8 and 9 , in these examples, except for Example 2, the volume ratio was approximately 0%, and the occurrence of cavitation CB was almost completely suppressed. This is because, as representatively shown in Examples 6, 13, and 15 in FIG. 10 , a portion of the leakage flow FL was blocked by the rectifying member 7, and the flow direction of the leakage flow FL was guided inward by the rectifying member 7 (the leakage flow FL was disturbed). Another portion of the leakage flow FL passed through the inter-component flow path FP and flowed toward the inducer 5. At this time, the rectifying member 7 provided strong resistance to the leakage flow, attenuating it. Therefore, the leakage flow FL reaching the flow path P1 was suppressed. Therefore, blockage of the flow path P1 due to the leakage flow FL was suppressed (does not occur). As a result, as shown in FIG. 11 , the pressure of the treated liquid in the flow path P2 was greater than the pressure (3,170 Pa) at which cavitation CB occurred. As a result, the occurrence of cavitation CB due to the leakage flow FL was suppressed downstream of the inducer 5.

[0083] In Example 2, the volume ratio was approximately 2%, and the effect of suppressing the occurrence of cavitation CB was slightly lower than in the other Examples. This is presumably because the inflow angle of the leakage flow FL relative to the rectifying member 7 was small, and a portion of the leakage flow FL that collided with the rectifying member 7 passed over the rectifying member 7 while moving along the longitudinal direction (approximately the circumferential direction) of the rectifying member 7. As a result, as shown in FIG. 10 , a portion of the leakage flow FL reached the flow path P1 while maintaining a relatively high flow velocity. However, the occurrence of cavitation CB was suppressed to approximately 1 / 50 of that in the conventional pump, and the occurrence of cavitation CB was sufficiently suppressed. On the other hand, in Examples 9 and 15, the occurrence of cavitation CB was almost completely suppressed. This is because, as representatively shown in FIG. 10 by Example 15, the inflow angle of the leakage flow FL relative to the rectifying member 7 was large (close to 90°), and more of the leakage flow FL was blocked by the rectifying member 7 than in Example 2.

[0084] Here, the volume ratio of Example 14 (angle θ: 60°, number: 12) is approximately the same as the volume ratio of Example 20 (angle θ: 120°, number: 12), and the volume ratio of Example 13 (angle θ: 30°, number: 12) is approximately the same as the volume ratio of Example 21 (angle θ: 150°, number: 12). Therefore, when the number of straightening members 7 is the same, it is estimated that the volume ratio when the angle θ is 175° will be approximately the same as the volume ratio when the angle θ is 5°, or will differ by about a few percent.

[0085] From these results, it can be seen that, as long as the width W2 of the inter-component flow path FP is secured to an extent that allows the inducer flow FI to flow in, the angle θ and the number of straightening members 7 do not have a significant effect on the effect of suppressing the occurrence of cavitation CB. Therefore, when the effect of suppressing the occurrence of cavitation CB is important, the angle θ is preferably 5° or more and 175° or less, more preferably 10° or more and 150° or less, and more preferably 20° or more and 90° or less.

[0086] Furthermore, as shown in FIG. 8 , in these examples, the efficiency ratio exceeded 100% in Examples 1, 2, 4, 6, 8, 9, 13, and 14, in which the angle θ was set to less than 90° (an acute angle), and fell below 100% in Examples 17, 20, and 21, in which the angle θ was set to 90° or greater (a right angle or an obtuse angle). This is because the inducer flow FI is a swirling flow in which the angle between the inducer flow FI and the imaginary plane VF, as viewed in the radial direction, is an acute angle (e.g., approximately 20° to 40°). That is, the straightening member 7, which is arranged so that the angle θ is an acute angle, does not provide resistance to the inducer flow FI, and the inducer flow FI passes through the inter-component flow path FP without losing its swirling velocity component and is sent to the impeller 6. On the other hand, the straightening member 7, which is arranged so that the angle θ is an obtuse angle, provides resistance to the inducer flow FI, and the inducer flow FI passes through the inter-component flow path FP while losing its swirling velocity component and is sent to the impeller 6. Furthermore, in the case of the rectifying members 7 arranged so that the angle θ is a right angle, the resistance to the inducer flow FI increases as the number of rectifying members 7 increases. Therefore, the efficiency ratio of Example 15 increases, while the efficiency ratios of Examples 17 to 19 decrease. Thus, when efficiency is emphasized, the angle θ is preferably an acute angle, more preferably 5° or more and 60° or less, more preferably 10° or more and 30° or less, and more preferably 20°. Furthermore, the number of rectifying members 7 is preferably 10 or less, more preferably 3.

[0087] From the above results, when both the suppression of the occurrence of cavitation CB and efficiency are important, the angle θ is preferably between 5° and 90°, more preferably an angle that is unlikely to provide resistance to the inducer flow FI and likely to provide resistance to the leakage flow FL, i.e., between 5° and less than 90° (acute angle), more preferably between 5° and 60°, and more preferably between 10° and 30°.

[0088] ● Change in the number of straightening members Next, analytical results when only the number of rectifying members 7 is changed will be explained using Examples 2 to 5, 6 to 8, 9 to 13, and 15 to 19 as examples.

[0089] As shown in Figures 8 and 9, in these examples, except for Examples 2 and 5, the volume ratio was approximately 0%, and the occurrence of cavitation CB was almost completely suppressed. The cause of the decrease in the effect of suppressing the occurrence of cavitation CB in Example 2 is as described above. Also, as shown in Figure 8, in these examples, the efficiency ratio exceeded 100% regardless of whether the number increased or decreased. This is because, as described above, the efficiency ratio is affected by the angle θ.

[0090] In Example 5, the volume ratio was approximately 2%, and the occurrence of cavitation CB was slightly less suppressed than in the other Examples. This was because the distance between adjacent flow straightening members 7 in the circumferential direction (i.e., the width of the inter-component flow path FP) was too narrow, and the inducer flow FI was not sufficiently guided to the inter-component flow path FP, which deteriorated the flow in flow path P1 of the flow paths downstream of the inducer 5, causing the inducer flow FI to be slightly biased toward flow path P2. However, the occurrence of cavitation CB was suppressed to approximately 1 / 50 of that in the conventional pump, and the occurrence of cavitation CB was sufficiently suppressed.

[0091] Similarly, analytical results when only the number of rectifying members 7 is changed will be explained using Examples 28 and 29, Examples 32 to 34, and Examples 35 and 36 as examples.

[0092] As shown in Figures 8 and 9, in these Examples, except for Examples 29 and 36, the volume ratio was several tens of percent, and the effect of suppressing the occurrence of cavitation CB was significantly lower than in the other Examples. This is because the length ratio was small, at 60% or less, as will be described later. Also, unlike the Examples with a length ratio of 80%, in Examples with a length ratio of 60% or less, the volume ratio decreased as the number of straightening members 7 increased. This is presumably because, as the number of straightening members 7 increased, the amount of leakage flow FL blocked (having its flow direction changed or disturbed) by the straightening members 7 increased.

[0093] From these results, it can be seen that, at least when the length ratio is 80% or more, the number of rectifying members 7 should be such that the width W2 of the inter-component flow path FP is sufficient to allow the inducer flow FI to flow in. It can also be seen that the number of rectifying members 7 does not significantly affect the effect of suppressing the generation of cavitation CB, except when the angle θ is extremely small (e.g., 10° or less) or extremely large (e.g., 170° or more). Therefore, the number of rectifying members 7 should be one or more and not more than the maximum number that can be arranged depending on the angle θ. On the other hand, when the angle θ is extremely small or extremely large, it can be seen that the number of rectifying members 7 affects the effect of suppressing the generation of cavitation CB. In this case, it is preferable that the number of rectifying members 7 is more than one (e.g., three). On the other hand, it can be seen that the number of rectifying members 7 significantly affects the effect of suppressing the generation of cavitation CB when the length ratio is 60% or less.

[0094] In the present invention, when the number of rectifying members 7 is one, the rectifying members 7 are adjacent to each other in the circumferential direction. In this case, the inter-member flow path FP is formed between the first surface 7a and the second surface 7b in the circumferential direction.

[0095] ●Change in protruding ratio Next, analytical results when only the protrusion ratio of the flow rectifying member 7 is changed will be explained using Examples 4, 22, 25, 13, 23, 26, and 17, 24, 27 as examples.

[0096] FIG. 12 is a velocity vector analysis diagram of some other examples 22 and 23.

[0097] FIG. 13 is an analysis diagram of absolute pressure distribution in some other Examples 22 and 23.

[0098] As shown in FIGS. 8 and 9, in these examples, except for Example 22, the volume ratio was about 0%, and the occurrence of cavitation CB was almost completely suppressed.

[0099] In Example 22, the volume ratio was approximately 54%, and the effect of suppressing the occurrence of cavitation CB was significantly lower than in the other Examples. This is presumably because the protrusion ratio was small (25%), the number of straightening members 7 was small, and, similar to Example 2, the inflow angle of the leakage flow FL relative to the straightening members 7 was small, allowing the leakage flow FL to easily overcome the straightening members 7. Therefore, as shown in FIG. 12, most of the leakage flow FL reached flow path P1 while maintaining a relatively high flow velocity. Furthermore, the inducer flow FI was biased toward flow path P2. As a result, as shown in FIG. 13, the pressure of the handled liquid in flow path P2 was lower than in Example 4 but higher than in the conventional pump. As a result, the occurrence of cavitation CB was suppressed to approximately half that of the conventional pump.

[0100] 8 and 9, in Examples 23 and 24, the volume ratio was approximately 0%, and the occurrence of cavitation CB was almost completely suppressed. This is presumably because the angle θ, i.e., the inflow angle of the leakage flow FL with respect to the straightening member 7, was large (close to 90°), the number of straightening members 7 was large, and the straightening members 7 were arranged so as to cross (disturb) the virtual leakage flow VFL multiple times. As a result, the straightening members 7 acted as a resistance to the leakage flow FL, and more of the leakage flow FL was blocked (disturbed) by the straightening members 7 than in Example 22. Therefore, even if the protrusion ratio is 25%, it is presumed that the occurrence of cavitation CB can be sufficiently suppressed when the angle θ is large (specifically, approximately 20° or more and 160° or less).

[0101] In Examples 25 to 27, the volume ratio was approximately 0%, and the occurrence of cavitation CB was almost completely suppressed. This is because, as in Examples 1, 3 to 21, 23, and 24, part of the leakage flow FL was blocked by the rectifying member 7, and the direction of the flow was guided to change inward by the rectifying member 7 (the leakage flow FL was disturbed).

[0102] From these results, it can be seen that the protrusion ratio has a relatively large effect on the effect of suppressing the occurrence of cavitation CB. The protrusion ratio should be a certain size that enables the rectifying members 7 to block part of the leakage flow FL and change the direction of that flow inward by the rectifying members 7, and is preferably 25% or more and 75% or less, more preferably 50% or more and 75% or less, and more preferably 50%. Here, in view of the above results, it is estimated that when the angle θ is 30° or more and 90° or less and / or when there are multiple rectifying members 7 (for example, around 12), the occurrence of cavitation CB can be suppressed even when the protrusion ratio is less than 25% (for example, 20%).

[0103] ● Change in length ratio Next, analysis results when only the length ratio of the flow straightening member 7 is changed will be described using examples 2, 28, 9, 30, 32, and 15, 31, 35. In the following description, the analysis results of example 15 in Figs. 10 and 11 will be referred to as appropriate.

[0104] FIG. 14 is a velocity vector analysis diagram of some other examples 31 and 35.

[0105] FIG. 15 is an absolute pressure distribution analysis diagram of some other Examples 31 and 35.

[0106] As shown in FIGS. 8 and 9 , in these examples, as the length ratio decreased, the volume ratio increased and the cavitation suppression effect tended to deteriorate. In particular, in the example with a length ratio of 20%, the cavitation suppression effect deteriorated significantly. This is presumably because, since the leakage flow FL flows along the inner circumferential surface 22a, as the length ratio decreased, the amount of leakage flow FL blocked (changed its flow direction or disturbed) by the flow straightening member 7 decreased. Therefore, as shown representatively in FIGS. 10 and 14 by Examples 15, 31, and 35, as the length ratio decreased, much of the leakage flow FL reached flow path P1 while maintaining a relatively high flow velocity. As a result, as shown representatively in FIGS. 11 and 15 by Examples 15, 31, and 35, as the length ratio decreased, the pressure of the treated liquid in flow path P2 decreased. However, in all examples, the occurrence of cavitation CB was suppressed. In particular, in the examples where the length ratio was 40% or more, the occurrence of cavitation CB was suppressed to about 1 / 3 or less of that in the conventional pump.

[0107] These results demonstrate that the length ratio significantly affects the suppression effect of cavitation CB. The length ratio should be large enough to allow the rectifying member 7 to block a portion of the leakage flow FL and change the direction of that flow inward, and is preferably 40% or more (length L3 / circumference LC: 2.8% or more), more preferably 60% or more (length L3 / circumference LC: 5.6% or more), and even more preferably 80% or more (length L3 / circumference LC: 7.0% or more). Considering the above results, it can be understood that the rectifying member 7 may extend at least to the center of the first inclined portion 22d. In this case, the upper limit of the length ratio is 150% (length L3 / circumference LC: approximately 10.5%).

[0108] Summary In the above description, the centrifugal pump 1 includes a housing 2, a motor 3, a rotating shaft 4, an inducer 5, an impeller 6, and a flow straightening member 7. The housing 2 includes a suction pipe section 22. The flow straightening member 7 is disposed between the inducer 5 and the impeller 6. The flow straightening member 7 is disposed so as to protrude inward from an inner peripheral surface 22a of the suction pipe section 22. In the axial direction, the first length L1 is longer than the second length L2. L2 According to this configuration, a portion of the leakage flow FL is blocked by the rectifying member 7, and the direction of the leakage flow FL is guided by the rectifying member 7 to change inward (the leakage flow FL is disturbed). Therefore, the leakage flow FL reaching the flow path P1 is suppressed. As a result, the occurrence of cavitation CB downstream of the inducer 5 is suppressed.

[0109] In the above description, the flow straightening member 7 is disposed so as to cross (disturb) the virtual leakage flow VFL. According to this configuration, the effect of suppressing the occurrence of cavitation CB downstream of the inducer 5 is improved.

[0110] In the above description, the centrifugal pump 1 includes three (a plurality of) straightening members 7. The straightening members 7 are arranged evenly in the circumferential direction. An inter-member flow path FP is formed between adjacent straightening members 7 in the circumferential direction. The inter-member flow path FP guides a portion of the inducer flow FI to the impeller 6. With this configuration, the inducer flow FI is less likely to be biased toward the flow path P2, and the effect of suppressing the occurrence of cavitation CB downstream of the inducer 5 is improved.

[0111] In the above description, the protrusion ratio is 50%. With this configuration, regardless of the angle θ and the number of straightening members 7, the occurrence of cavitation CB downstream of the inducer 5 is reliably suppressed.

[0112] In the above description, the angle θ is 20°. According to this configuration, regardless of the number of straightening members 7, the occurrence of cavitation CB downstream of the inducer 5 is reliably suppressed, and the efficiency of the centrifugal pump 1 is also improved.

[0113] In the above description, the flow straightening member 7 is arranged to cause the leakage flow FL to flow inward. With this configuration, the occurrence of cavitation CB downstream of the inducer 5 is reliably suppressed.

[0114] In the above description, the ratio of the length L3 to the circumference LC is approximately 7.0%. According to this configuration, the occurrence of cavitation CB downstream of the inducer 5 is reliably suppressed.

[0115] Other embodiments In the present invention, the centrifugal pump 1 may be a so-called vertically-mounted pump in which the rotary shaft 4 is arranged along the vertical direction.

[0116] In the present invention, the centrifugal pump 1 may include a plurality of impellers 6 .

[0117] Furthermore, in the present invention, the impeller 6 may be a so-called open-type impeller.

[0118] Furthermore, in the present invention, a part of pump chamber 21 may constitute the introduction part of the present invention together with suction pipe section 22. That is, for example, a part (front part) of the part of pump chamber 21 that includes second inner surface 21b and suction pipe section 22 may constitute the introduction part of the present invention.

[0119] Furthermore, in the present invention, the shape of the inner circumferential surface 22a is not limited to this embodiment. That is, for example, the inner circumferential surface 22a does not have to include the first inclined portion 22d and / or the second inclined portion 22e. If the inner circumferential surface 22a does not include the second inclined portion 22e, the inner diameter of the small diameter portion 22c will be the same as the inner diameter of the wear ring 24.

[0120] Furthermore, in the present invention, the shape of the rectifying member 7 is not limited to this embodiment. That is, for example, the shape of the rectifying member 7 does not have to be plate-like. Also, for example, the first surface 7a and / or the second surface 7b may be curved. Furthermore, for example, the third surface 7c may be curved. Furthermore, for example, the second surface 7b does not have to be parallel to the first surface 7a (may be non-parallel). Furthermore, for example, the rectifying member 7 does not have to include the third surface 7c, the fourth surface 7d, or the fifth surface 7e. Furthermore, for example, the first surface 7a and / or the second surface 7b may be parallel to the radial direction when viewed from the front, or may be non-parallel to the radial direction.

[0121] Furthermore, in the present invention, the first length L1 may be the same as the second length L2.

[0122] Furthermore, in the present invention, the protrusion ratios of the plurality of rectifying members 7 may be different from each other. That is, for example, the protrusion ratio of rectifying member 71 may be 25%, and the protrusion ratios of rectifying members 72 and 73 may be 50%.

[0123] Furthermore, in the present invention, the shapes of the respective rectifying members 7 may be different from one another. That is, for example, the rectifying member 71 may be flat, and the rectifying members 72 and 73 may be curved.

[0124] Furthermore, in the present invention, the angle θ of each of the rectifying members 7 may be different. That is, for example, the angle θ of the rectifying member 71 may be 20°, and the angles of the rectifying members 72 and 73 may be 30°.

[0125] Furthermore, in the present invention, the arrangement of the flow guide members 7 in the circumferential direction does not have to be uniform.

[0126] Furthermore, in the present invention, the flow regulating member 7 may also be disposed on the first inclined portion 22d and / or the second inclined portion 22e.

[0127] Furthermore, in the present invention, the lengths L3 of the flow regulating members 7 may be different from each other.

[0128] Furthermore, in the present invention, the third surface 7c does not have to be located at the same position as the front end of the small diameter portion 22c.

[0129] Furthermore, in the present invention, the fourth surface 7d does not have to be located at the same position as the rear end of the small diameter portion 22c.

[0130] Furthermore, in the present invention, the second length L2 in the axial direction is not limited to that of the present embodiment. That is, for example, the second length L2 may be set to be shorter than that of the present embodiment, or may be 0 (the length at which the fourth surface 7d of the flow straightening member 7 and the front end 64a of the suction port 64 of the impeller 6 come into contact).

[0131] ●Embodiments of the present invention● Next, embodiments of the present invention that can be understood from the above-described embodiment will be described below, using the terms and symbols described in the embodiment.

[0132] A first embodiment of the present invention includes a motor (e.g., motor 3), a rotating shaft (e.g., rotating shaft 4) rotated by the drive of the motor, an impeller (e.g., impeller 6) attached to the rotating shaft and suctioning and discharging the treated fluid, an inducer (e.g., inducer 5) attached to the rotating shaft and arranged upstream of the impeller in the flow of the treated fluid, a housing (e.g., housing 2) accommodating the impeller and the inducer, and at least one straightening member (e.g., straightening member 7) arranged between the inducer and the impeller, and in the axial direction of the rotating shaft, a direction in which the inducer is arranged relative to the impeller is a first direction (e.g., forward direction), and a direction opposite to the first direction is a second direction (e.g., rearward direction), The housing accommodates a portion of the rotating shaft on the first direction side (e.g., front portion 4a) and the inducer, and includes an introduction section (e.g., suction pipe section 22) that introduces the treated fluid toward the impeller, the introduction section having a cylindrical inner circumferential surface (e.g., inner circumferential surface 22a), the straightening member having a first end portion on the first direction side (e.g., third surface 7c) and a second end portion on the second direction side (e.g., fourth surface 7d), the straightening member being arranged to protrude inward from the inner circumferential surface in the radial direction of the rotating shaft, and a first length (e.g., first length L1) between the first end portion and the inducer in the axial direction being equal to or longer than a second length (e.g., second length L2) between the second end portion and the impeller. According to this configuration, the occurrence of cavitation due to leakage flow downstream of the inducer is suppressed.

[0133] A second embodiment of the present invention is the centrifugal pump of the first embodiment, wherein the first length is greater than the second length. With this configuration, the occurrence of cavitation due to leakage flow downstream of the inducer is further suppressed.

[0134] A third embodiment of the present invention is a centrifugal pump in which, in the first embodiment, when the impeller is rotating, a portion of the handled fluid discharged from the impeller flows toward the first direction from a gap (e.g., gap S2) between the impeller and the housing, causing a backflow (e.g., leakage flow FL) of the handled fluid in the first direction of the impeller, and the backflow is a swirling flow that flows in the rotational direction of the rotating shaft (e.g., rotational direction RD) and along the inner circumferential surface from the second direction toward the first direction, and the straightening member is arranged so as to cross a portion of the virtual backflow (e.g., virtual leakage flow VFL) that would occur if the straightening member were not arranged on the inner circumferential surface. According to this configuration, the effect of suppressing the occurrence of cavitation downstream of the inducer is improved.

[0135] A fourth embodiment of the present invention is a centrifugal pump which is any one of the first to third embodiments and which comprises a plurality of straightening members, the straightening members being arranged in a line in the circumferential direction of the rotating shaft, and an inter-component flow path (e.g., an inter-component flow path FP) being formed between adjacent straightening members in the circumferential direction to guide the handled fluid sent from the inducer to the impeller. According to this configuration, the effect of suppressing the occurrence of cavitation downstream of the inducer is improved.

[0136] A fifth embodiment of the present invention is a centrifugal pump in which, in the fourth embodiment, the ratio (e.g., protrusion ratio) of the amount of protrusion (e.g., protrusion amount LP) of the straightening member inward from the inner circumferential surface to the flow path width (e.g., flow path width WF) of the handled liquid on the radial line of the inner circumferential surface is 25% or more and 75% or less. According to this configuration, regardless of the angle and the number of discharge members, the occurrence of cavitation downstream of the inducer is more reliably suppressed.

[0137] A sixth embodiment of the present invention is the centrifugal pump of the fifth embodiment, wherein the ratio of the protrusion amount to the flow path width is not less than 50% and not more than 75%. According to this configuration, regardless of the angle and the number of straightening members, the occurrence of cavitation downstream of the inducer is more reliably suppressed.

[0138] A seventh embodiment of the present invention is a centrifugal pump according to the fourth embodiment, wherein the straightening member has a first surface (e.g., first surface 7a) facing the rotational direction of the rotation shaft and a second surface (e.g., second surface 7b) facing the opposite direction to the rotational direction, and the angle between the first surface and an imaginary plane (e.g., imaginary plane VF) passing through the first end of the straightening member and perpendicular to the rotation shaft is greater than or equal to 5° and less than or equal to 175°. According to this configuration, regardless of the number of straightening members, the occurrence of cavitation downstream of the inducer is reliably suppressed.

[0139] An eighth embodiment of the present invention is the centrifugal pump of the seventh embodiment, wherein the angle is equal to or greater than 5° and equal to or less than 90°. According to this configuration, regardless of the number of straightening members, the occurrence of cavitation downstream of the inducer is more reliably suppressed.

[0140] A 9th embodiment of the present invention is the centrifugal pump of the 8th embodiment, wherein the angle is equal to or greater than 5° and equal to or less than 60°. According to this configuration, regardless of the number of straightening members, the occurrence of cavitation downstream of the inducer is more reliably suppressed, and the efficiency of the centrifugal pump is also improved.

[0141] A tenth embodiment of the present invention is a centrifugal pump in the fourth embodiment, wherein the ratio of the length of the straightening member in the axial direction (e.g., length L3) to the circumference of the inner circumferential surface (e.g., circumference LC) is 5.6% or more. According to this configuration, the occurrence of cavitation downstream of the inducer is suppressed.

[0142] An eleventh embodiment of the present invention is the centrifugal pump of the tenth embodiment, wherein the ratio of the length to the circumference is 7.0% or more. According to this configuration, the occurrence of cavitation downstream of the inducer is reliably suppressed.

[0143] A twelfth embodiment of the present invention is a centrifugal pump in which, in the first embodiment, the straightening member is arranged so as to generate a flow toward the inward side against a backflow of the handled fluid caused by a portion of the handled fluid discharged from the impeller flowing toward the first direction through a gap between the impeller and the housing (e.g., gap S2). According to this configuration, the occurrence of cavitation downstream of the inducer is reliably suppressed. [Explanation of symbols]

[0144] 1. Centrifugal pump 2. Case 3 motors 4 rotation axes 4a Front part (part of the rotation axis) 5. Inducer 6 impeller 7 Straightening member 7a 1st page 7b 2nd side 7c Third surface (end on the first direction side) CL Inner circumference of small diameter part (inner circumference of inner surface) FL Leakage flow (backflow) FP inter-component flow path L1 First length L2 Second length L3 Length of straightening member LP protrusion amount RD rotation direction VF Virtual Plane VFL Virtual leakage flow (virtual backflow) WF Flow path width

Claims

1. A motor; a rotating shaft that rotates when driven by the motor; an impeller attached to the rotary shaft for sucking and discharging pumped fluid; an inducer attached to the rotary shaft and disposed upstream of the impeller in the flow of the treated fluid; a housing that houses the impeller and the inducer; At least one flow straightening member disposed between the inducer and the impeller; and a first direction in which the inducer is disposed relative to the impeller in an axial direction of the rotation shaft, and a second direction opposite to the first direction, The housing includes: an introduction section that accommodates a portion of the rotary shaft on the first direction side and the inducer and introduces the pumped fluid toward the impeller; With The introduction section A cylindrical inner surface, With The flow rectifying member is a first end portion on the first direction side; a second end portion on the second direction side; With The inner circumferential surface is an inclined surface disposed between the flow straightening member and the impeller in the axial direction; With The impeller is a cylindrical suction port along the axial direction; With A cylindrical gap is defined between the housing and the suction port along the axial direction, a first length between the first end and the inducer in the axial direction is equal to or greater than a second length between the second end and the impeller; When the impeller is rotating, a portion of the pumped fluid discharged from the impeller flows through the gap in the first direction, causing a backflow of the pumped fluid in the first direction of the impeller, the reverse flow is a swirling flow that flows in the rotation direction of the rotation shaft and along the inner circumferential surface from the second direction toward the first direction, The flow rectifying member is so as to cross a part of the virtual backflow when the flow straightening member is not disposed on the inner circumferential surface, In the radial direction of the rotary shaft, the inner peripheral surface is protruded inward. When viewed in the first direction, the gap is overlapped with the gap. Placed, When viewed in the first direction, the gap is disposed so as to pass through a center of the flow straightening member in the radial direction. Centrifugal pump.

2. The first length is greater than the second length.

2. The centrifugal pump of claim 1.

3. A plurality of the flow straightening members; and The flow straightening members are arranged side by side in the circumferential direction of the rotation shaft, An inter-member flow path is formed between adjacent flow straightening members in the circumferential direction, through which the pumped fluid sent from the inducer is guided to the impeller.

3. The centrifugal pump according to claim 1 or 2.

4. In the radial direction, a ratio of a protrusion amount of the flow straightening member inward from the inner circumferential surface to a flow path width of the treated fluid on a radial line of the inner circumferential surface is 25% or more and 75% or less.

4. The centrifugal pump according to claim 3.

5. the ratio of the protrusion amount to the flow path width is 50% or more and 75% or less; 5. The centrifugal pump according to claim 4.

6. The flow rectifying member is a first surface facing in the rotation direction of the rotation shaft; a second surface facing in a direction opposite to the rotation direction; With an angle between the first surface and an imaginary plane that passes through the first end of the rectifying member and is perpendicular to the rotation axis is equal to or greater than 5° and equal to or less than 175°; 4. The centrifugal pump according to claim 3.

7. The angle is greater than or equal to 5° and less than or equal to 90°.

7. The centrifugal pump according to claim 6.

8. The angle is greater than or equal to 5° and less than or equal to 60°.

8. The centrifugal pump according to claim 7.

9. a ratio of the length of the flow straightening member in the axial direction to the circumference of the inner circumferential surface is 5.6% or more; 4. The centrifugal pump according to claim 3.

10. The ratio of the length to the circumference is 7.0% or more.

10. The centrifugal pump of claim 9.

11. The rectifying member is arranged to generate a flow toward the inward direction against a backflow of the treated fluid that occurs when a portion of the treated fluid discharged from the impeller flows toward the first direction through a gap between the impeller and the housing.

2. The centrifugal pump of claim 1.

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