Centrifugal impellers and centrifugal pumps

Abstract

By improving the shape of the centrifugal impeller, the pumping efficiency of centrifugal pumps can be increased. [Solution] The centrifugal impeller 2 comprises at least one centrifugal blade 21, the centrifugal blade having a negative pressure surface 23 extending from the center of the impeller to the outer edge, a pressure surface 24 positioned away from the negative pressure surface so that the centrifugal blade has a predetermined thickness and extending from the center of the impeller towards the outer edge, and a second pressure surface 25 located on the outer edge side of the impeller and inside the outer edge, closer to the negative pressure surface than a hypothetical surface 241 which is a continuous extension of the pressure surface to the outer edge, and connected to the pressure surface.

Description

TECHNICAL FIELD

[0001] The technology disclosed herein relates to a centrifugal impeller and a centrifugal pump.

BACKGROUND ART

[0002] Patent Document 1 describes a conventional centrifugal impeller and a conventional centrifugal pump. This centrifugal impeller is an impeller used in so-called vortex pumps. The centrifugal impeller has a shroud and a plurality of centrifugal blades provided upright on the shroud surface. The centrifugal impeller is disposed so as to be retracted relative to a volute portion inside a casing. In the vortex pump, a relatively large space is left between the centrifugal impeller and the inner wall surface of the casing, and foreign matter sucked into the casing is directly discharged to the outside without passing through the impeller.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0004] As described above, since the vortex pump has a large space inside the casing, the pump efficiency is relatively lowered. For this reason, there is a demand for increasing the pump efficiency of the vortex pump as much as possible.

[0005] Not limited to vortex pumps, for example, centrifugal pumps provided with non-clog type impellers are also required to have improved pump efficiency. The non-clog type impeller is an impeller having a large space for foreign matter to pass through inside the impeller, and in the case of a closed impeller, the centrifugal impeller has an internal flow path that connects the suction port and the discharge port of the impeller inside the impeller.

[0006] The technology disclosed herein improves the pumping efficiency of a centrifugal pump by modifying the shape of the centrifugal impeller. [Means for solving the problem]

[0007] The technology disclosed herein relates to a centrifugal impeller. A centrifugal impeller is, It is equipped with at least one centrifugal blade extending from the center of the impeller towards the outer edge, The aforementioned centrifugal vanes are, The negative pressure surface of the impeller extends from the central part to the outer edge, The centrifugal blades are positioned away from the negative pressure surface so as to have a predetermined thickness, and the pressure surface extends from the center of the impeller toward the outer edge, On the outer peripheral edge side of the impeller and inward from the outer peripheral edge, a second pressure surface is located closer to the negative pressure surface than a hypothetical surface that extends the pressure surface continuously to the outer peripheral edge, and is connected to the pressure surface. It holds.

[0008] The centrifugal impeller's blades have a negative pressure surface and a pressure surface. The negative pressure surface extends from the center of the impeller to the outer edge. The negative pressure surface extends from the center outward in the radial direction of the impeller and curves in the counter-rotation direction of the impeller.

[0009] The pressure surface extends from the center of the impeller towards the outer edge. The centrifugal blades have a predetermined thickness because the negative pressure surface and the pressure surface are located apart from each other. The pressure surface also extends from the center, curving outward in the radial direction of the impeller and in the counter-rotation direction of the impeller.

[0010] The centrifugal vanes have a second pressure surface. The second pressure surface is located on the outer edge side of the impeller and inside of the outer edge, and connects to the pressure surface. The outer edge side of the impeller may be defined as being on the outer edge side of the midpoint of the centrifugal vanes extending from the center of the impeller to the outer edge.

[0011] The second pressure surface is located closer to the negative pressure surface than a hypothetical surface that would be created by continuously extending the pressure surface to its outer edge. The blade thickness between the second pressure surface and the negative pressure surface is thinner than the blade thickness between the pressure surface and the negative pressure surface. The second pressure surface can be formed by cutting out a portion of the pressure surface side of the centrifugal blade.

[0012] A centrifugal impeller with a second pressure surface on its blades exhibits an improvement in flow velocity at the outer edge of the impeller. This is thought to be because the thin blade thickness between the second pressure surface and the negative pressure surface promotes flow along the second pressure surface due to the influence of the low pressure on the negative pressure side. As a result of this promotion of flow along the second pressure surface, the centrifugal impeller is thought to exhibit an improvement in flow velocity at the outer edge of the impeller. This improvement in flow velocity leads to an increase in the flow rate of the centrifugal blades.

[0013] A centrifugal impeller having a second pressure surface can reduce the shaft power of the centrifugal pump and increase the total head, thereby improving pump efficiency, compared to a conventional centrifugal impeller without a second pressure surface.

[0014] Furthermore, since the second pressure surface deviates from the hypothetical surface that extends continuously from the pressure surface to its outer edge, it is thought that vortices are generated around the second pressure surface. These vortices draw the flow that would otherwise move away from the pressure surface towards the pressure surface and the second pressure surface on the outer edge side of the impeller. This suppresses flow separation, resulting in a flow that follows the centrifugal blades, and thus the flow velocity increases.

[0015] The second pressure surface may be located between the outer edge of the impeller and the pressure surface, along the direction in which the centrifugal blade extends.

[0016] If the second pressure surface is formed, for example, in contact with the outer edge of the impeller, the aforementioned effect of improving the flow velocity on the outer edge side of the impeller is enhanced, which is advantageous for improving pump efficiency. However, the second pressure surface is not limited to being in contact with the outer edge of the impeller.

[0017] The second pressure surface may extend from an end of the pressure surface to the outer peripheral edge of the impeller at an angle different from the virtual surface.

[0018] The angle referred to herein means an angle in a direction along the pressure surface or the second pressure surface of the centrifugal blade extending from the central portion toward the outer peripheral edge.

[0019] The second pressure surface may be a surface extending from the end of the pressure surface in a direction approaching the suction surface. When viewed with the line of sight parallel to the rotation axis of the impeller, the second pressure surface is formed by cutting out the portion on the outer peripheral edge side of the pressure surface of the centrifugal blade into a roughly triangular shape. Since the blade thickness between the second pressure surface and the suction surface is relatively narrow, the flow velocity is improved.

[0020] The second pressure surface may include a first portion extending from the end of the pressure surface at an angle different from the virtual surface, and a second portion that is continuous with the first portion and extends to the outer peripheral edge of the impeller at an angle different from the first portion.

[0021] The angle of the second portion may be, for example, the same as or substantially the same as the angle of the virtual surface. If the angle of the second portion is the same as or substantially the same as the angle of the virtual surface, when viewed with the line of sight parallel to the rotation axis of the impeller, the second pressure surface is formed by cutting out the portion on the outer peripheral edge side of the pressure surface of the centrifugal blade into a roughly parallelogram shape.

[0022] The angle of the second portion may be, for example, the same as or substantially the same as the angle of the suction surface.

[0023] Since the blade thickness between the second pressure surface and the suction surface is relatively narrow, the flow velocity increases. Furthermore, on the outer peripheral edge side of the centrifugal blade, a step recessed from the pressure surface is formed, which is considered to promote the generation of vortices around the second pressure surface. As described above, the vortices draw the flow that tends to separate from the pressure surface on the outer peripheral edge side of the impeller toward the pressure surface and the second pressure surface. Since the substantial flow passage area of the centrifugal impeller is enlarged, the flow rate is improved. The aforementioned shape of the second pressure surface contributes to the increase in the flow velocity as well as the increase in the passage flow rate of the impeller. The pump efficiency of the centrifugal pump equipped with the centrifugal impeller is improved.

[0024] The second pressure surface may include a first portion extending at the same angle as the virtual surface and at a position closer to the suction surface than the virtual surface, and a second portion located between the first portion and the outer peripheral edge of the impeller, extending at the same angle as the virtual surface and at a position closer to the suction surface than the first portion.

[0025] Furthermore, the second pressure surface may include a first portion extending at the same angle as the suction surface and at a position closer to the suction surface than the virtual surface, and a second portion located between the first portion and the outer peripheral edge of the impeller, extending at the same angle as the suction surface and at a position closer to the suction surface than the first portion.

[0026] The second pressure surface may have a shape that gradually approaches the suction surface via two steps formed by the first portion and the second portion. This shape is advantageous for the aforementioned generation of vortices around the second pressure surface.

[0027] At least one recessed portion recessed from the pressure surface toward the suction surface may be formed in the portion of the pressure surface on the outer peripheral edge side of the impeller.

[0028] The recessed portion formed on the pressure surface in the vicinity of the second pressure surface further promotes the generation of vortices around the second pressure surface.

[0029] The centrifugal impeller may be an impeller for a vortex pump in which the centrifugal blades are erected on the shroud and arranged to retract from the volute portion within the casing so as to ensure a predetermined particle size can pass through.

[0030] The aforementioned centrifugal impeller is suitable for improving the pumping efficiency of vortex pumps.

[0031] The centrifugal impeller may be a non-clogging type impeller in which the centrifugal blades form a primary flow path connecting an intake port formed at one end and a discharge port formed on the side, and a secondary flow path that is continuous with the primary flow path and extends along the outer surface.

[0032] The aforementioned centrifugal impeller is suitable for improving the pump efficiency of pumps equipped with non-clogging centrifugal impellers.

[0033] The centrifugal pump disclosed herein is equipped with the aforementioned centrifugal impeller. Because the centrifugal pump is equipped with the aforementioned centrifugal impeller, the pump efficiency is improved. [Effects of the Invention]

[0034] The aforementioned centrifugal impeller and centrifugal pump can improve pump efficiency. [Brief explanation of the drawing]

[0035] [Figure 1] Figure 1 is a cross-sectional view of a centrifugal pump equipped with a centrifugal impeller. [Figure 2] Figure 2 is a perspective view of a centrifugal impeller. [Figure 3] Figure 3 shows a plan view and a partially enlarged view of the centrifugal impeller. [Figure 4] Figure 4 shows the performance curve of a centrifugal pump. [Figure 5] Figure 5 shows a plan view and a partially enlarged view of a modified centrifugal impeller. [Figure 6] Figure 6 shows a plan view and a partially enlarged view of a centrifugal impeller relating to a modified example. [Figure 7] Figure 7 shows a plan view and a partially enlarged view of a centrifugal impeller relating to a modified example. [Figure 8] Figure 8 is a plan view of a modified centrifugal impeller. [Figure 9] Figure 9 is a plan view of a modified centrifugal impeller. [Figure 10] Figure 10 is a plan view of a modified centrifugal impeller. [Figure 11] Figure 11 is a plan view of a modified centrifugal impeller. [Figure 12] Figure 12 shows a side view and an AA cross-sectional view of a non-clogged centrifugal impeller. [Modes for carrying out the invention]

[0036] The following describes embodiments of centrifugal impellers and centrifugal pumps with reference to the drawings. The centrifugal impellers and centrifugal pumps described herein are illustrative examples.

[0037] (Overall structure of a centrifugal pump) Figure 1 shows a centrifugal pump 1 equipped with a centrifugal impeller 2. The centrifugal pump 1 is a submersible pump for wastewater treatment and is a vortex pump with good ability to pass foreign matter.

[0038] The centrifugal pump 1 comprises a pump section 3 having a centrifugal impeller 2 and a motor section 4 having a motor 41 that drives the centrifugal impeller 2. The pump section 3 is located on the lower side of the oil casing 11, and the motor section 4 is located on the upper side of the oil casing 11. Inside the oil casing 11, the shaft 42 of the motor 41, which will be described later, is sealed by a mechanical seal 12.

[0039] The motor unit 4 includes a motor 41 and a motor casing 43 that covers the motor 41. The shaft 42 of the motor 41 extends in the vertical direction.

[0040] The centrifugal impeller 2 of the pump unit 3 is mounted on the lower end of the shaft 42 of the motor 41. The pump unit 3 has a pump casing 31.

[0041] The pump casing 31 is attached to the lower part of the oil casing 11. The centrifugal impeller 2 is positioned in the upper part of the pump casing 31. The lower part of the pump casing 31 is the volute section 34. The centrifugal impeller 2 is positioned retracted from the volute section 34. A relatively large space is formed between the centrifugal impeller 2 and the inner wall surface of the pump casing 31.

[0042] A suction port 32 opening downwards is formed at the bottom of the pump casing 31. A discharge port 33 protruding laterally is formed on the side of the pump casing 31. The discharge port 33 is connected to a discharge pipe.

[0043] (Structure of a centrifugal impeller) Figure 2 is a perspective view of the centrifugal impeller 2. Figure 3 is a plan view of the centrifugal impeller 2 with the line of sight parallel to the rotation axis X of the centrifugal impeller 2. Note that Figure 2 shows the centrifugal impeller 2 inverted compared to the state in which the centrifugal impeller 2 is attached to the shaft 42 of the motor 41.

[0044] The centrifugal impeller 2 is a semi-open type impeller and has a shroud 20 and centrifugal blades 21. The shroud 20 is roughly disc-shaped. The centrifugal blades 21 are erected in the direction of the rotation axis X relative to the surface of the shroud 20. The centrifugal impeller 2 in Figure 3 has six centrifugal blades 21. The six centrifugal blades 21 are arranged at equal intervals in the circumferential direction of the shroud 20, thereby forming the blade row of the centrifugal impeller 2.

[0045] A hub 22 is formed in the center of the shroud 20. The hub 22 is fixed to the lower end of the shaft 42 of the motor 41.

[0046] The centrifugal vanes 21 extend from the hub 22 radially outward from the shroud 20 and in the counter-rotational direction of the centrifugal impeller 2, in a predetermined curved shape. The leading edge of each centrifugal vane 21 is connected to the hub 22. The trailing edge of each centrifugal vane 21 is located on the outer edge of the shroud 20.

[0047] The centrifugal vane 21 has a negative pressure surface 23 and a pressure surface 24. The negative pressure surface 23 extends from the hub 22 to the outer edge of the shroud 20.

[0048] The pressure surface 24 extends from the hub 22 toward the outer edge of the shroud 20. The pressure surface 24 is positioned at a predetermined distance from the negative pressure surface 23. The separation of the negative pressure surface 23 and the pressure surface 24 gives the centrifugal vane 21 a predetermined thickness. The blade thickness T1 of the centrifugal vane 21 is substantially constant throughout the centrifugal vane 21, except for a portion of the trailing edge of the centrifugal vane 21, which will be described later.

[0049] The centrifugal impeller 21 has a second pressure surface 25. The second pressure surface 25 is located on the outer peripheral edge side of the centrifugal impeller 2 and inside the outer peripheral edge of the shroud 20. More specifically, as shown in the enlarged view of Figure 3, the second pressure surface 25 is located between the outer peripheral edge of the shroud 20 and the pressure surface 24, along the direction in which the centrifugal impeller 21 extends. In the enlarged view of Figure 3, the centrifugal impeller 21 is shaded for clarity.

[0050] The second pressure surface 25 is located closer to the negative pressure surface 23 than the hypothetical surface 241 (see dashed line in Figure 3), which is a continuous extension of the pressure surface 24 to its outer edge.

[0051] More specifically, the second pressure surface 25 has a first portion 251 and a second portion 252. The first portion 251 extends from the edge of the pressure surface 24 at a different angle from the imaginary surface 241, approaching the negative pressure surface 23.

[0052] The second portion 252 is continuous with the first portion 251 and extends to the outer edge of the shroud 20. The second portion 252 extends at a different angle than the first portion 251. The second portion 252 extends at the same or approximately the same angle as the hypothetical surface 241. In the second portion 252, the negative pressure surface 23 and the second pressure surface 25 are approximately parallel. The blade thickness T2 between the negative pressure surface 23 and the second pressure surface 25 is thinner than the blade thickness T1 between the negative pressure surface 23 and the second pressure surface 25.

[0053] The negative pressure surface 23 and the virtual surface 241 do not have to be parallel to each other, and the second portion 251 is not limited to extending at approximately the same angle as the negative pressure surface 23 and / or the virtual surface 241.

[0054] When viewed with a line of sight parallel to the rotation axis X of the centrifugal impeller 2, the second pressure surface 25 is formed by cutting out the outer peripheral edge of the pressure surface 24 of the centrifugal blade 21 in an approximately parallelogram shape. The second pressure surface 25 creates a step on the outer peripheral edge of the centrifugal blade 21 that is recessed from the pressure surface 24.

[0055] Note that the reference numeral 29 shown in the enlarged view of Figure 3 represents the trailing edge of the centrifugal vane 21. The trailing edge 29 is the portion that runs along the outer edge of the shroud 20. Since the trailing edge 29 coincides with the outer edge of the shroud 20, it is not referred to as the pressure surface or second pressure surface in this context.

[0056] A centrifugal impeller 2 having a second pressure surface 25 can improve the flow velocity on the outer edge of the shroud 20. This is thought to be because the blade thickness T2 between the second pressure surface 25 and the negative pressure surface 23 is thin, and the flow along the second pressure surface 25 is promoted by the influence of the low pressure on the negative pressure surface 23 side. As a result of the promoted flow, the centrifugal impeller 2 can improve the flow velocity on the outer edge of the shroud 20. The increase in flow velocity increases the flow rate of the centrifugal impeller 2.

[0057] Furthermore, it is thought that a vortex is generated around the second pressure surface 25, as shown in the enlarged view of Figure 3, due to the step on the outer edge of the pressure surface 24 of the centrifugal blade 21. The vortex draws the flow that is trying to move away from the pressure surface 24 (see the white dashed arrow) towards the pressure surface 24 or the second pressure surface 25 (see the white solid arrow) on the outer edge of the centrifugal impeller 2. As the effective passage area between adjacent centrifugal blades 21 of the centrifugal impeller 2 is increased, this contributes to an increase in the flow rate passing through the centrifugal impeller 2, along with an increase in flow velocity.

[0058] Figure 4 shows the performance curve of a centrifugal pump 1 equipped with the centrifugal impeller 2 shown in Figure 3. The solid line in Figure 4 represents an embodiment, in which the centrifugal impeller 2 has a second pressure surface 25. The dashed line in Figure 4 represents a conventional example, in which the centrifugal impeller does not have a second pressure surface.

[0059] Comparing the embodiment with the conventional example, the embodiment shows a reduction in shaft power and an improvement in total head compared to the conventional example. The pump efficiency of the embodiment is higher than that of the conventional pump. The centrifugal impeller 2 having a second pressure surface 25 can improve the pump efficiency of the centrifugal pump 1.

[0060] It should be noted that the technology disclosed herein is not limited to the case where all centrifugal blades 21 have a second pressure surface 25. It is not excluded that some centrifugal blades 21 have a second pressure surface 25. The centrifugal blades 21 having a second pressure surface 25 may be evenly distributed in the circumferential direction in the centrifugal impeller 2.

[0061] (modified version) Figure 5 shows a modified centrifugal impeller 2. The centrifugal impeller 2 in Figure 5 differs from the centrifugal impeller 2 in Figure 3 in the shape of the second pressure surface 26.

[0062] The second pressure surface 26 extends from the edge of the pressure surface 24 to the outer edge of the shroud at a different angle from the virtual surface 241. When viewed with a line of sight parallel to the rotation axis X of the centrifugal impeller 2, the second pressure surface 26 is formed by cutting out a roughly triangular shape from the outer edge side of the centrifugal blade 21.

[0063] In the centrifugal impeller 2 shown in Figure 5, the flow velocity is improved because the blade thickness between the second pressure surface 26 and the negative pressure surface 23 is relatively narrow. As a result, the centrifugal pump 1 equipped with the centrifugal impeller 2 shown in Figure 5 can also achieve improved pump efficiency.

[0064] The centrifugal impeller 2 in Figure 6 differs from the centrifugal impeller 2 in Figure 3 or Figure 5 in the shape of the second pressure surface 28.

[0065] The second pressure surface 28 includes a first portion 281 and a second portion 282. The first portion 281 extends at the same angle as the virtual surface 241 or the negative pressure surface 23, at a position closer to the negative pressure surface 23 than the virtual surface 241. The second portion 282 is located between the first portion 281 and the outer edge of the shroud 20, along the direction in which the centrifugal vane 21 extends. The second portion 282 extends at the same angle as the virtual surface 241 or the negative pressure surface 23, at a position closer to the negative pressure surface 23 than the first portion 281. The second pressure surface 28 has a shape that approaches the negative pressure surface 23 in steps due to the two steps between the first portion 281 and the second portion 282. The centrifugal impeller 2 having two steps is advantageous for vortex generation around the second pressure surface 28.

[0066] Figure 7 shows a centrifugal impeller 2 according to another modified example. The centrifugal impeller 2 in Figure 7 has a recessed portion 27 added to the centrifugal impeller 2 in Figure 3.

[0067] The recessed portion 27 is formed on the pressure surface 24. The recessed portion 27 is formed on the pressure surface 24 at the outer peripheral edge of the centrifugal impeller 2, in other words, at a location near the second pressure surface 25. The recessed portion 27 is recessed from the pressure surface 24 toward the negative pressure surface 23.

[0068] The recessed portion 27 in Figure 7 has a semicircular shape when viewed with the line of sight parallel to the rotation axis X of the centrifugal impeller 2. However, the shape of the recessed portion 27 is not limited to a semicircle; it could also be triangular or square, for example.

[0069] The centrifugal impeller 2 in Figure 7 has four recesses 27 for each centrifugal blade 21. The four recesses 27 are arranged at equal intervals from the center side to the outer edge side of the pressure surface 24. The number of recesses 27 can be set as appropriate.

[0070] The recess 27 formed in the pressure surface 24 near the second pressure surface 25 promotes the generation of vortices around the second pressure surface 25. The centrifugal pump 1 equipped with the centrifugal impeller 2 shown in Figure 7 further improves pump efficiency.

[0071] Furthermore, the recessed portion 27 is not limited to being formed on all of the centrifugal blades 21 of the centrifugal impeller 2. The recessed portion 27 may be formed on some of the centrifugal blades 21.

[0072] Furthermore, the recessed portion 27 may be formed on the centrifugal blade 21 of the centrifugal impeller 2 shown in Figure 5, or on the centrifugal blade 21 of the centrifugal impeller 2 shown in Figure 6.

[0073] Figure 8 shows centrifugal impellers 2 with different numbers of centrifugal blades 21. The centrifugal impeller 2 may have, for example, four centrifugal blades 21. The centrifugal blades 21 have a second pressure surface 25, similar to the centrifugal blades 21 of the centrifugal impeller 2 in Figure 3.

[0074] Figure 9 shows yet another centrifugal impeller 2 having four centrifugal blades 21. The centrifugal blades 21 in Figure 9 have a second pressure surface 26, similar to the centrifugal blades 21 of the centrifugal impeller 2 in Figure 5.

[0075] Furthermore, a centrifugal impeller 2 having four centrifugal blades 21 may have a second pressure surface 28 including two steps, as shown in the centrifugal impeller 2 of Figure 6. Also, a centrifugal impeller 2 having four centrifugal blades 21 may have a recessed portion 27, as shown in the centrifugal impeller 2 of Figure 7.

[0076] Figure 10 shows a centrifugal impeller 2 having eight centrifugal blades 21. The centrifugal blades 21 in Figure 10 have a second pressure surface 25, similar to the centrifugal blades 21 of the centrifugal impeller 2 in Figure 3.

[0077] Figure 11 shows yet another centrifugal impeller 2 having eight centrifugal blades 21. The centrifugal blades 21 in Figure 11 have a second pressure surface 26, similar to the centrifugal blades 21 of the centrifugal impeller 2 in Figure 5.

[0078] Furthermore, the centrifugal impeller 2 having eight centrifugal blades 21 may have a second pressure surface 28 including two steps, as shown in the centrifugal impeller 2 of Figure 6. Also, the centrifugal impeller 2 having eight centrifugal blades 21 may have a recessed portion 27, as shown in the centrifugal impeller 2 of Figure 7.

[0079] Figure 12 shows a non-clogging centrifugal impeller 5. The lower part of Figure 12 is a side view of the centrifugal impeller 5, and the upper part of Figure 12 is a cross-sectional view AA of the lower part.

[0080] The centrifugal blades 51 of the non-clogging type centrifugal impeller 5 form a primary channel 52 and a secondary channel 53.

[0081] The primary flow path 52 connects the suction port 54 and the discharge port 55 of the centrifugal impeller 5. The suction port 54 opens downward at the lower end of the centrifugal impeller 5. The discharge port 55 opens laterally on the side of the centrifugal impeller 5 above the flange portion 56.

[0082] The secondary flow path 53 is formed in a shape that resembles a portion of the outer circumference of the centrifugal impeller 5 being cut inward. The secondary flow path 53 is continuous with the discharge port 55 and extends in the circumferential direction of the centrifugal impeller 5.

[0083] The centrifugal impeller 5 has two centrifugal blades 51. As shown in the upper diagram of Figure 12, the centrifugal blades 51 extend from the center of the centrifugal impeller 5 toward the outer edge.

[0084] The centrifugal impeller 51 has a negative pressure surface 57. The negative pressure surface 57 extends from the center to the outer edge of the centrifugal impeller 5.

[0085] The centrifugal blade 51 has a pressure surface 58. The pressure surface 58 is positioned away from the negative pressure surface 57 so that the centrifugal blade 51 has a predetermined thickness, and extends from the center of the centrifugal impeller 5 towards the outer edge. Note that the blade thickness of the centrifugal blade 51 is not constant.

[0086] The centrifugal blade 51 has a second pressure surface 59. The second pressure surface 59 is located between the outer edge of the centrifugal impeller 5 and the pressure surface 58, along the direction in which the centrifugal blade 51 extends.

[0087] The second pressure surface 59 has a first portion 591 and a second portion 592. The first portion 591 extends from the end of the pressure surface 58 towards the negative pressure surface 57 at a different angle from a hypothetical surface 581 which is a continuous extension of the pressure surface 58 to its outer edge.

[0088] The second portion 592 is continuous with the first portion 591 and extends to the outer edge of the centrifugal impeller 5. The second portion 592 extends at a different angle from the first portion 591, more specifically at the same or approximately the same angle as the negative pressure surface 57.

[0089] The centrifugal impeller 5 has a second pressure surface 59, which improves pump efficiency.

[0090] In the non-clogging type centrifugal impeller 5, the centrifugal blades 51 may have a second pressure surface 26 as shown in Figure 5, or a two-stage second pressure surface 28 as shown in Figure 6. The centrifugal blades 51 may also have a recessed portion 27 as shown in Figure 7. [Explanation of Symbols]

[0091] 1. Centrifugal pump 2. Centrifugal impeller 20 Shroud 21 Centrifugal blades 23 Suction surface 24 Pressure surface 241 Virtual surface 25 Second pressure surface 251 Part 1 252 Part 2 26 Second pressure surface 27 Recessed area 28 Second pressure surface 281 Part 1 282 Part 2 31 Pump Casing 5. Centrifugal impeller 51 Centrifugal blades 52 Primary channel 53 Secondary channel 54 Inlet 55 Discharge port 57 Suction surface 58 Pressure surface 581 Virtual surface 59 Second pressure surface 591 Part 1 592 Part 2

Claims

1. It is equipped with at least one centrifugal blade extending from the center of the impeller towards the outer edge, The aforementioned centrifugal vanes are, The negative pressure surface of the impeller extends from the central part to the outer edge, The centrifugal blades are positioned away from the negative pressure surface so as to have a predetermined thickness, and the pressure surface extends from the center of the impeller toward the outer edge, On the outer peripheral edge side of the impeller and inward from the outer peripheral edge, a second pressure surface is located closer to the negative pressure surface than a hypothetical surface that extends the pressure surface continuously to the outer peripheral edge, and is connected to the pressure surface. Having, Centrifugal impeller.

2. In the centrifugal impeller according to claim 1, The second pressure surface is located between the outer edge of the impeller and the pressure surface, along the direction in which the centrifugal blade extends. Centrifugal impeller.

3. In the centrifugal impeller according to claim 2, The second pressure surface extends from the edge of the pressure surface to the outer edge of the impeller at an angle different from that of the hypothetical surface. Centrifugal impeller.

4. In the centrifugal impeller according to claim 2, The second pressure surface includes a first portion extending from the edge of the pressure surface at an angle different from that of the virtual surface, and a second portion continuous with the first portion and extending to the outer peripheral edge of the impeller at an angle different from that of the first portion. Centrifugal impeller.

5. In the centrifugal impeller according to claim 2, The second pressure surface includes a first portion extending at the same angle as the virtual surface and closer to the negative pressure surface than the virtual surface, and a second portion located between the first portion and the outer edge of the impeller and extending at the same angle as the virtual surface and closer to the negative pressure surface than the first portion. Centrifugal impeller.

6. In the centrifugal impeller according to claim 2, At least one recessed portion is formed on the outer peripheral edge side of the impeller on the pressure surface, which is recessed from the pressure surface toward the negative pressure surface. Centrifugal impeller.

7. In the centrifugal impeller according to claim 1, The centrifugal blades are erected on the shroud and positioned to retract from the volute portion within the casing to ensure a predetermined particle size can pass through, in this impeller for a vortex pump. Centrifugal impeller.

8. In the centrifugal impeller according to claim 1, The centrifugal vanes form a non-clogging type impeller, which has a primary flow path connecting an intake port formed at one end and a discharge port formed on the side, and a secondary flow path that is continuous with the primary flow path and extends along the outer surface. Centrifugal impeller.

9. A centrifugal pump comprising a centrifugal impeller according to any one of claims 1 to 8.

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