Submerged semi-axial flow centrifugal pump and impeller for such a pump

Abstract

The invention relates to a submersible semi-axial flow centrifugal pump (1) for installation in a column (2), comprising an outer pump casing (7) and an inner pump core device (14), the impeller comprising a hub (28) and at least two helically swept blades (29), the hub being substantially conical tapering towards an inlet opening (12) of the pump casing, the leading edge of each blade being swept back from an inner end located at the hub towards an outer end (37) located at the inner surface of the pump casing, the central axis (A) of the impeller being located at a relative radius R* equal to 0, the outer end of the leading edge of each blade of the impeller being located at a relative radius R* equal to 1, and the sweep angle (a) of the leading edge being in the range 32-45 degrees at a first relative radius R*1 equal to 0.5, in the range 47-60 degrees at a second relative radius R*2 equal to 0.95, and continuously increasing from the first relative radius R*1 to the second relative radius R*2. The invention also relates to a semi-axial flow open centrifugal impeller for the aforementioned submersible semi-axial flow centrifugal pump.

Description

Technical Field

[0001] This invention generally relates to the field of submersible semi-axial flow centrifugal pumps configured for pumping liquids comprising solid / fibrous materials. Submersible semi-axial flow centrifugal pumps are typically used to transport large volumes of filtered sewage / wastewater, rainwater, drainage, etc., at rated / nominal operating speeds over relatively limited heights (e.g., approximately 2000 liters / second, approximately 20 meters). Submersible semi-axial flow centrifugal pumps are typically arranged to descend into a rigid column extending from a first / lower pool / volume to a second / upper pool / volume.

[0002] In particular, the present invention relates to a submersible semi-axial flow centrifugal pump for mounting in a column and configured for pumping a liquid comprising solid substances. The pump includes:

[0003] - An external pump housing having an axial inlet and an axial outlet; and

[0004] - An internal pump core assembly, comprising:

[0005] - A stationary drive unit, which is at least partially surrounded by a pump housing;

[0006] - A semi-axial flow open-type centrifugal impeller, which is suspended on the drive unit and located near the inlet of the pump casing; and

[0007] - Multiple guide vanes extend between the pump housing and the drive unit of the pump core assembly, connecting the pump housing and the drive unit.

[0008] The impeller includes a hub and at least two helical swept blades connected to and extending radially from the hub. The hub is generally a conical shape that tapers towards the inlet of the pump housing. Each blade includes a front edge facing the inlet of the pump housing, a rear edge facing the outlet of the pump housing, and a lower edge extending from the front edge to the rear edge and located near the inner surface of the pump housing.

[0009] The present invention also relates to a semi-axial flow open centrifugal impeller suitable for a semi-axial flow centrifugal pump according to the above. Background Technology

[0010] In some types of liquid handling, such as transporting large volumes of contaminated water containing solids (i.e., sewage / wastewater, rainwater, drainage, etc.), submersible semi-axial centrifugal pumps offer many advantages over conventional axial propeller pumps, which are typically used for clean or lightly contaminated water.

[0011] Traditional semi-axial flow centrifugal pumps are designed to combine the advantages of centrifugal pumps in terms of efficiency, pressure, and pumping capacity for contaminated water, while allowing for axial discharge flow similar to axial propeller pumps. Therefore, the pump is designed to guide liquid in an outward spiral, radially / axially mixed manner from the impeller towards the pump housing to increase pressure through centrifugal force. Guide vanes then redirect the liquid flow from rotation to the axial direction to restore the static pressure of the liquid leaving the pump housing. The inlet and outlet of the semi-axial flow centrifugal pump face axially. This type of semi-axial flow centrifugal pump can also be called a mixed-flow pump.

[0012] Semi-axial flow centrifugal pumps are arranged to descend into the column and are typically installed downstream of a screen, thus protecting them from fibrous materials, wet wipes, textiles, masks, etc., which can easily clog the pump and impeller by adhering to the leading edge of the impeller. Traditional semi-axial flow centrifugal pumps include either closed or open impellers with straight leading edges, where the impeller is designed / optimized solely for pumping performance. Therefore, traditional semi-axial flow centrifugal pumps do not have a direct risk of clogging because the worst solids are removed before the liquid reaches the pump, allowing the pump to be designed / optimized only for pumping performance. However, when different screens are used upstream of the pump to prevent solids from reaching it, these screens must be cleaned regularly, which is a tedious and laborious task.

[0013] Therefore, there is a need in this technical field for a semi-axial flow centrifugal pump configured to pump unfiltered liquids including fibrous solids (e.g., wet wipes, textiles, masks, etc.).

[0014] Purpose of the invention

[0015] The purpose of this invention is to eliminate the aforementioned disadvantages and defects of previously known semi-axial flow centrifugal pumps and semi-axial flow open centrifugal impellers, and to provide an improved semi-axial flow centrifugal pump and an improved semi-axial flow open centrifugal impeller.

[0016] The primary objective of this invention is to provide an improved semi-axial flow centrifugal pump and an improved semi-axial flow open centrifugal impeller, configured to pump unfiltered liquids comprising fibrous solids. Another objective of this invention is to provide an improved semi-axial flow centrifugal pump and an improved semi-axial flow open centrifugal impeller, wherein solids are guided outward along the radial / tangential direction of the pump inlet without significantly negatively impacting pumping performance. Summary of the Invention

[0017] According to the invention, at least the primary objective is achieved by a pump and impeller having the features defined in the independent claims. Preferred embodiments of the invention are further defined in the dependent claims.

[0018] According to the present invention, the leading edge of each blade of the impeller sweeps backward from the inner end located at the hub toward the outer end located at the inner surface of the pump housing, and the outer end of the leading edge is located upstream of the inner end of the leading edge.

[0019] -The central axis (A) of the impeller is located at a relative radius R* equal to 0, and the outer ends of the leading edges of each blade of the impeller are located at a relative radius R* equal to 1.

[0020] - The sweep angle (α) of the leading edge is in the range of 32-45 degrees at the first relative radius R*1 equal to 0.5, and in the range of 47-60 degrees at the second relative radius R*2 equal to 0.95, and increases continuously from the first relative radius R*1 to the second relative radius R*2.

[0021] - The sweep angle (α) at ​​any given relative radius R* at the leading edge lies in a first geometric plane (P1) determined by the following:

[0022] - A first vector (V1) that is tangent to the average line of the blade at a given relative radius R* at the leading edge, and

[0023] - A second vector (V2) that is tangent to the front edge at a given relative radius R*, and

[0024] - The sweep angle (α) is determined between the following:

[0025] - A first vector (V1) that is tangent to the average line of the blade at a given relative radius R* at the leading edge, and

[0026] - The third vector (V3) is perpendicular to the front edge at a given relative radius R*.

[0027] Therefore, this invention is based on the understanding that when the leading edge of the impeller is designed based on the optimal value of the sweep angle (α) along the leading edge, a self-cleaning effect of the impeller / pump is achieved without negatively impacting the pumped flow (pumping performance). The sweep angle (α) should increase continuously from the first relative radius R*1 to the second relative radius R*2, but this increase does not necessarily have to be linear, and the increase is preferably slightly accelerated in the outward direction. By positioning the outer end of the leading edge upstream of the inner end of the leading edge, the pressure side extension of the impeller blades near the leading edge can be designed in a way that further optimizes the pumping performance of the pump.

[0028] According to various embodiments of the invention, the sweep angle (α) of the leading edge is in the range of 32-40 degrees at a first relative radius R*1 equal to 0.5, and in the range of 47-55 degrees at a second relative radius R*2 equal to 0.95, and increases continuously from the first relative radius R*1 to the second relative radius R*2. By reducing the upper limits of the sweep angle (α) at ​​the first relative radius R*1 and the second relative radius R*2, respectively, any negative impact on pumping performance is also reduced. The lower limits of the sweep angle (α) at ​​the first relative radius R*1 and the second relative radius R*2 remain unchanged because these are found to provide sufficient self-cleaning of the impeller's leading edge over a wide range of operating speeds (i.e., pump rpm).

[0029] According to various embodiments of the present invention, the inner end of the leading edge of each blade of the impeller is located at a third relative radius R*3 in the range of 0.25 to 0.45.

[0030] Moving the inner end of the leading edge closer to the impeller's central axis (A) reduces liquid flow within the inner portion of the leading edge and diminishes the self-cleaning effect near the top of the hub. Therefore, the top of the impeller hub should preferably have the smallest diameter to prevent fibrous solids from tangling around the hub. Conversely, moving the inner end of the leading edge too far from the central axis (A) increases the risk of tissues, fabrics, etc., sticking to the top of the hub. Therefore, the top of the impeller hub should preferably have the largest diameter.

[0031] According to various embodiments of the invention, the local sector angle (θ-part) projected by the leading edge onto the transverse plane (P2) of the pump is obtained between the following:

[0032] - A first line, which extends from the impeller's central axis (A) to the intersection between the leading edge and the first relative radius R*1, and

[0033] - The second line extends from the impeller's central axis (A) to the intersection between the leading edge and the second relative radius R*2.

[0034] The local sector angle (θ-part) is in the range of 25-55 degrees.

[0035] Having too small a local sector angle (θ-part) impairs the impeller's self-cleaning effect and increases the tilt / angle of the impeller's leading edge, causing the inner end of the impeller's leading edge to be upstream of the outer end of the impeller's leading edge. Having too large a local sector angle (θ-part) reduces the width between adjacent blades of the impeller and increases the risk of clogging.

[0036] According to various embodiments of the invention, the tilt angle (β) of the leading edge lies in an axial plane (P3) parallel to the central axis (A) of the impeller, wherein the tilt angle (β) is determined between the following:

[0037] - A sloping line that extends between the inner and outer ends of the front edge, and

[0038] - The horizontal plane of the pump (P2).

[0039] The tilt angle (β) is in the range of 0-35 degrees, and the outer end of the front edge is located upstream of the inner end of the front edge.

[0040] By positioning the outer end of the leading edge upstream of the inner end of the leading edge, the pressure side extension of the impeller blades near the leading edge can be designed in a way that promotes more optimized pumping performance.

[0041] Other advantages and features of the invention will become clear from the other dependent claims and from the following detailed description of preferred embodiments. Attached Figure Description

[0042] The above and other features and advantages of the present invention will be more fully understood from the following detailed description of preferred embodiments in conjunction with the accompanying drawings, in which:

[0043] Figure 1 This is a schematic perspective view of a semi-axial flow centrifugal pump as seen from above.

[0044] Figure 2 It includes according to Figure 1 A schematic side sectional view of a pumping station for a semi-axial flow centrifugal pump.

[0045] Figure 3 It is based on Figure 1 A schematic side sectional view of a portion of a semi-axial flow centrifugal pump.

[0046] Figure 4 This is a schematic perspective cross-sectional view taken from below a portion of a semi-axial flow centrifugal pump.

[0047] Figure 5 From the basis Figure 1 A schematic perspective view of the hydraulic unit of a semi-axial flow centrifugal pump from below.

[0048] Figure 6 From the basis Figure 1 A schematic diagram showing the top view of a semi-axial flow centrifugal pump.

[0049] Figure 7 This is a schematic diagram of the leading edge of the impeller blades.

[0050] Figure 8This is a schematic diagram showing the leading edge of the impeller as seen from below, and

[0051] Figure 9 This is a schematic diagram showing the sweep angle of an example impeller at different relative radii, and also shows the sweep angle interval at the first and second relative radii. Detailed Implementation

[0052] First refer to Figure 1 and 2 This invention generally relates to a submersible semi-axial flow centrifugal pump, generally designated 1, configured for pumping liquids comprising solid / fibrous materials, such as sewage / wastewater, rainwater, drainage, etc. The semi-axial flow centrifugal pump 1 is typically arranged to deliver large volumes of liquid at a fairly limited height at its rated / nominal operating speed, for example, approximately 2000 liters / second at approximately 20 meters. The semi-axial flow pump 1 according to the invention is designed to have a specific velocity n in the range of 80-160. q Preferably, the range is 100-120. Specific speed n q Determined to be n q =n*Q （1 / 2） / H （3 / 4） Where n = nominal rotational speed of the propeller pump (rpm), Q = pumped liquid flow rate (m2 / sec), and H = pumped liquid head (m).

[0053] exist Figure 1 The image disclosed is a perspective view taken from above of the semi-axial flow pump 1 according to the present invention. Figure 2 A portion of a schematic pumping station is disclosed, comprising one or more semi-axial flow pumps 1, each pump 1 arranged at the lower end of a column 2. According to the disclosed embodiment, the column 2 extends from a lower pool 3 to an upper pool 4, with the purpose of conveying liquid from the lower pool 3 to the upper pool 4. It should be noted that the axial length of the column 2 is typically several times greater than the axial height of the pump 1, and the pump 1 and the column 2 are arranged concentrically relative to each other. The pump 1 is connected to one or more cables 5 for power supply and possibly signal transmission, which extend from the pump 1 through the interior of the column 2 to a power supply and / or control unit (not shown).

[0054] The following also refers to Figure 3 , Figure 3 A schematic side sectional view of the lower portion of the semi-axial flow centrifugal pump 1 and the lower end of the column 2 is disclosed, showing the pump 1 and a portion of the column 2 removed. Thus, the pump 1 is typically arranged within the column 2, which is partially lowered into the pumping medium. During installation, the semi-axial flow centrifugal pump 1 descends into the column 2 until it stands upright on the bottom flange 6 within the column 2, thereby tightly sealing the column 2. Therefore, the pump 1 is completely or partially submerged in the medium when it reaches its operating position. During operation, the column 2 also serves as the outlet pipe for the pumped liquid. Before any maintenance is performed on the pump 1, it is raised and removed from the column 2.

[0055] The semi-axial centrifugal pump 1 of the present invention includes an axially extending outer pump housing, generally designated 7. The outer pump housing 7 is substantially tubular and, in the disclosed embodiments, includes an inlet funnel 8 and a diffuser 9, which are axially connected to each other. According to various embodiments, the inlet funnel 8 and the diffuser 9 are fixedly connected to each other by a plurality of axially extending connecting screws 10. Thus, the inlet funnel 8 can be detached from the diffuser 9 by loosening the connecting screws 10, but when the pump 1 is assembled, the inlet funnel 8 and the diffuser 9 are in direct and fixed contact with each other. Therefore, the pump 1 always has the same height. The pump housing 7 has an inner surface 11 and also includes an axial inlet opening 12 located at the lower / upstream end of the inlet funnel 8 and an axial outlet opening 13 located at the upper / downstream end of the diffuser 9. Thus, the inner surface 11 of the pump housing 7 extends from the inlet 12 to the outlet 13. The pump 1 is arranged to descend into a column 2, thus the pump 1 has an outer diameter slightly smaller than the inner diameter of the column 2. This creates a gap between the outer surface of the pump housing 7 and the inner surface of the column 2. To prevent the pumped liquid from flowing back down through this gap (i.e., through the space between the inner surface of the column 2 and the outer surface of the pump housing 7), the pump housing 7 rests on and is tightly sealed against a radially inwardly extending bottom flange 6 located at the lower end of the column 2. The space between the column 2 and the pump 1 can be filled with water and solids without negatively affecting the operation of the pump 1. According to various embodiments, the lower surface of the pump 1 abuts against the flange 6. However, other flanges of the pump 1 can be used as abutment surfaces, such as the flange at the interface between the diffuser 9 and the inlet funnel 8.

[0056] Furthermore, the semi-axial centrifugal pump 1 according to the invention includes an axially extending internal pump core assembly, generally designated 14. When the pump 1 is installed in the column 2, the lower portion of the pump core assembly 14 is surrounded by the pump housing 7, i.e., by the diffuser 9, and the upper portion of the pump core assembly 14 is surrounded by the column 2. Therefore, the axial height of the pump core assembly 14 is greater than the axial height of the pump housing 7. Preferably, the axial height of the pump core assembly 14 is at least twice the axial height of the pump housing 7. In other words, the pump housing 7 and the pump core assembly 14 are arranged to overlap each other in the axial direction, while the pump core assembly 14 is located at a certain distance from the inner surface 11 of the pump housing 7 in the radial direction. Preferably, the pump core assembly 14 and the pump housing 7 are arranged concentrically relative to each other. In addition, the pump 1 according to the invention includes a plurality of radially extending guide vanes 15, which are connected to the inner surface 11 of the pump housing 7 and the envelope surface of the pump core assembly 14. Preferably, the pump 1 includes ten or more such guide vanes 15, which are arranged equidistantly along the circumference of the pump core assembly 14. See also... Figure 6 , Figure 6A view taken from above the pump 1 according to the invention is disclosed.

[0057] The internal pump core assembly 14 includes a drive unit (generally designated 16) comprising an electric motor 17 and a drive shaft 18 extending axially from the motor. The motor 17 is directly or indirectly connected to a power supply cable 5 extending from an external power source. Preferably, the drive unit 16 includes an axially extending tubular motor housing 19. Guide vanes 15 extend between the motor housing 19 and the pump housing 7 of the drive unit 16. Furthermore, the pump core assembly 14 includes a semi-axial open-circuit centrifugal impeller 20 suspended from the drive unit 16, i.e., suspended from the lower end of the drive shaft 18. The impeller 20 is located near the inlet 12 of the pump housing 7. The impeller 20 is located radially inward of the diffuser 9.

[0058] The pump core assembly 14 also includes a liquid sealing unit 21 configured such that the volume housing the impeller 20 and the liquid-sealed motor compartment housing the motor 17 are liquid-sealed apart, i.e., to protect the motor 17 from the pumped liquid. The liquid sealing unit 21 is surrounded by a motor housing 19, an upper wall 22 (referred to as the oil housing cover), and a lower wall 23 (referred to as the oil housing bottom), which together define a chamber 24 for containing liquid (preferably oil). The liquid sealing unit 21 forms a seat for a drive shaft sealing assembly 25, also referred to as a sealing cylinder, which is schematically disclosed and includes an external mechanical face seal to prevent pumped liquid leakage into the chamber 24 and an internal mechanical face seal to prevent liquid leakage in the chamber 24 into the motor compartment. Instead of the mechanical face seal, the drive shaft sealing assembly 25 may include other suitable types of seals; alternatively, the liquid sealing unit 21 may include other types of sealing solutions besides the drive shaft sealing assembly.

[0059] Furthermore, in the illustrated embodiment, the pump core assembly 14 includes a pump top, generally designated 26, wherein an internal power supply to the motor 17 and an external power supply are interconnected via a power supply cable 5. The pump top 26 includes a liquid-sealed lead 27 for receiving the cable 5. Preferably, the pump top 26 has a truncated conical shape to minimize the area with backward-directing / negative flow velocity appearing directly downstream of the pump top 26 in the column 2.

[0060] According to various embodiments, pump 1 (more precisely, electric motor 17) is operatively connected to a control unit, which may include, for example, an intelligent drive comprising a variable frequency drive (VFD). Thus, pump 1 is configured to operate at a variable operating speed (rpm) via the control unit. According to various embodiments, the control unit is located in the electronic chamber of pump top 26, i.e., preferably, the control unit is integrated into pump 1. Pump top 26 (i.e., the electronic / connection chamber) is liquid-sealed away from the motor chamber. The control unit is configured to control the operating speed of pump 1. According to alternative embodiments, the control unit is an external control unit, or the control unit is divided into external and internal sub-units. More precisely, the operating speed of pump 1 is the rpm of electric motor 17 and impeller 20, corresponding to the output frequency of the control unit.

[0061] The components of pump 1 are cooled by the liquid / water surrounding pump 1.

[0062] The semi-axial open-type centrifugal impeller 20 includes a hub 28 and at least two helical swept blades / vanes 29 connected to and extending radially from the hub 28. The hub 28 is generally conical and tapers gradually toward the inlet 12 of the pump housing 7. At the downstream end of the impeller 20, the envelope surface of the hub 28 is aligned with the envelope surface of the motor housing 19 of the drive unit 16. At the upstream end of the impeller 20, the hub 28 includes a spherical top 30 without blades 29. The spherical top 30 of the hub is preferably removable to allow access to the drive shaft 18, i.e., to allow the impeller 20 to be connected to the lower end of the drive shaft 18 in a conventional manner (e.g., by screws).

[0063] Each blade 29 includes a leading edge 31 facing the inlet 12 of the pump housing 7, a trailing edge 32 facing the outlet 13 of the pump housing 7, and a lower edge 33, wherein the lower edge 33 extends from the leading edge 31 to the trailing edge 32 and is located near the inner surface 11 of the pump housing 7. The lower edge 33 separates the pressure side 34 and the suction side 35 of the blade 29 from each other.

[0064] Each blade 29 extends toward the inner surface 11 of the pump housing 7, and the narrow gap separates the blade 29 from the inner surface 11 of the pump housing 7. The gap is preferably equal to or greater than 0.05 mm and equal to or less than 2 mm. Preferably, the impeller 20 includes three or four blades 29 equidistantly arranged along the circumference of the hub 28. See also... Figure 4 and 5 , Figure 4 and 5The diffuser 9 is disclosed, wherein the inlet funnel 8 is removed for clarity. The blades 29 sweep spirally from the leading edge 31 to the trailing edge 32, that is, sweep in the opposite direction of rotation of the impeller 20 during normal (liquid pumping) operation of the pump 1.

[0065] According to the present invention, the leading edge 31 of each blade 29 of the impeller 20 sweeps backward from the inner end 36 located at the hub 28 toward the outer end 37 located at the inner surface 11 of the pump housing 7. The central axis (A) of the impeller 20 is located at a relative radius R* equal to 0, and the outer end 37 of the leading edge 31 of each blade 29 of the impeller 20 is located at a relative radius R* equal to 1. The leading edge 31 has a sweep angle (α), which determines the design / construction of the upstream region of the blade 29 and can be considered a trade-off between pumping performance and self-cleaning. The present invention focuses on designing the leading edge 31 of the blade 29 such that any solid material trapped on the leading edge 31 is automatically guided / delivered outward toward the outer end 37 of the leading edge 31. The rotational speed at the outer end 37 of the leading edge 31 is greater than the rotational speed at the inner end 36 of the leading edge 31, so solid material is more likely to slip off the leading edge 31 during outward guidance.

[0066] The inventors have realized that the optimal self-cleaning function is achieved when the sweep angle (α) of the current edge 31 is in the range of 32-45 degrees at the first relative radius R*1 equal to 0.5, and in the range of 47-60 degrees at the second relative radius R*2 equal to 0.95, and increases continuously from the first relative radius R*1 to the second relative radius R*2.

[0067] Therefore, at the first relative radius R*1, the sweep angle (α) is equal to or greater than 32 degrees and equal to or less than 45 degrees. A smaller sweep angle (α) at ​​the first relative radius R*1 makes the self-cleaning of the leading edge 31 unsatisfactory and increases the risk of the impeller becoming softly clogged (i.e., solid matter will adhere to the leading edge 31), while a larger sweep angle (α) at ​​the first relative radius R*1 results in an excessively negative impact on pumping performance. Preferably, the sweep angle (α) at ​​the first relative radius R*1 is equal to or less than 40 degrees. Therefore, any negative impact on pumping performance is further reduced.

[0068] Furthermore, at the second relative radius R*2, the sweep angle (α) is equal to or greater than 47 degrees and equal to or less than 60 degrees. A smaller sweep angle (α) at ​​the second relative radius R*2 makes the self-cleaning of the leading edge 31 unsatisfactory and increases the risk of the impeller becoming softly clogged (i.e., solid matter will adhere to the leading edge 31), while a larger sweep angle (α) at ​​the second relative radius R*2 results in an excessively negative impact on pumping performance. Preferably, the sweep angle (α) at ​​the second relative radius R*2 is equal to or less than 55 degrees. Therefore, any negative impact on pumping performance is further reduced.

[0069] The first relative radius R*1 is equal to 0.5 because the design / construction of the front edge 31 closer to the hub 28 has a small or negligible influence, and the actual shape of the front edge 31 radially inward of the first relative radius R*1 depends more on having a smooth transition to the hub 28. The second relative radius R*2 is equal to 0.95 because the design / construction of the front edge 31 at the outer end 37 is based on having a smooth transition to the lower edge 33 of the front edge 31.

[0070] The inner end 36 of the leading edge 31 of each blade 29 of the impeller 20 is located at a third relative radius R*3, which is equal to or greater than 0.25 and equal to or less than 0.45, preferably equal to or less than 0.35. A smaller value of the third relative radius R*3 makes the attachment of the impeller 20 to the drive shaft 18 more complicated, and extending the leading edge 31 further inward will have a limited or negligible impact on the overall pumping performance. A larger value of the third relative radius R*3 risks making the top of the hub 28 too large and increases the risk of solid material being trapped on the top of the hub 28.

[0071] The following is a special reference Figure 7 , Figure 7 A schematic diagram of the leading edge 31 of the blade 29 of the impeller 20 is disclosed. Only a portion of the blade 29 is disclosed, and the blade 29 is shown as partially transparent.

[0072] The sweep angle (α) at ​​any given relative radius R* at the leading edge 31 (i.e., within the limits of the aforementioned relative radius R*) lies in / is measured in the first geometric plane (P1). The extent of the first geometric plane P1 varies for each given relative radius R* and is determined by:

[0073] - A first vector (V1) that is tangent to the average line 38 of the blade 29 at a given relative radius R* at the leading edge 31, and

[0074] - Second vector (V2), which is tangent to the front edge 31 at a given relative radius R*.

[0075] The first vector (V1) represents the theoretically optimal flow vector when observed locally at the leading edge region 31 of the blade, and V1 is parallel to the direction of the flow path.

[0076] Viewed between the pressure side 34 and the suction side 35 of blade 29, the average line 38 of blade 29 is the middle of blade 29, and the first vector V1 (i.e., the extension of the average line 38) tangent to the average line 38 represents the design / construction of the leading edge 31 viewed along the flow path direction. The second vector V2 tangent to the leading edge 31 represents the design / construction of the leading edge 31 viewed across the flow path direction. Therefore, the average line 38 of the blade extends from the leading edge 31 to the trailing edge 32, and the ratio between the distance from the average line 38 to the envelope surface of the hub 28 and the distance from the average line 38 to the inner surface 11 of the pump housing 7 is constant.

[0077] The sweep angle (α) lies in the first geometric plane (P1) and is determined / measured between the following:

[0078] - A first vector (V1) that is tangent to the average line 38 of the blade 29 at a given relative radius R* at the leading edge 31, and

[0079] - The third vector (V3) is perpendicular to the front edge 31 at a given relative radius R*.

[0080] The third vector (V3) represents the normal to the leading edge 31 when viewed locally at the leading edge 31 of the blade, and its deviation from the optimal first vector (V1) is determined by the sweep angle (α). Therefore, the deviation between the third vector (V3) and the optimal first vector (V1) provides the radial force acting radially outward along the leading edge 31 on and transporting the solid material.

[0081] The following is for reference. Figure 8 , Figure 8 A schematic diagram of the leading edge 31 of the impeller 20 as viewed from below through the inlet 12 of the pump 1 is disclosed. The disclosed impeller 20 includes four blades 29. According to various embodiments, the leading edge 31 sweeps backward from the inner end 36 to the outer end 37, which can be determined / measured by projecting the leading edge 31 onto the transverse plane (P2) of the pump 1. The full sector angle (θ-full) of the projection of the leading edge 31 onto the transverse plane (P2) of the pump 1 is obtained between the following:

[0082] - Inner end line 39, which extends from the central axis (A) of the impeller 20 to the inner end 36 of the leading edge 31, and

[0083] - Outer end line 40, which extends from the central axis (A) of the impeller 20 to the outer end 37 of the leading edge 31.

[0084] The full sector angle (θ-full) is in the range of 30-70 degrees.

[0085] A smaller full sector angle (θ-full) impairs the self-cleaning effect of the impeller 20 and necessitates an increase in the tilt / angle of the leading edge 31 of the impeller 20 so that the inner end 36 of the leading edge 31 of the impeller 20 is upstream of the outer end 37 of the leading edge 31 of the impeller 20. A larger full sector angle (θ-full) reduces the width between adjacent blades 29 of the impeller 20 and increases the risk of clogging.

[0086] According to various embodiments, the local sector angle (θ-part) projected by the leading edge 31 onto the transverse plane (P2) of the pump 1 is obtained between the following:

[0087] - A first line 41 extends from the central axis (A) of the impeller 20 to the intersection between the leading edge 31 and the first relative radius R*1, and

[0088] - Second line 42, which extends from the central axis (A) of the impeller 20 to the intersection between the leading edge 31 and the second relative radius R*2.

[0089] The local sector angle (θ-part) is in the range of 25-55 degrees.

[0090] A smaller local sector angle (θ-part) impairs the self-cleaning effect of the impeller 20 and necessitates an increase in the tilt / angle of the leading edge 31 of the impeller 20 so that the inner end 36 of the leading edge 31 is upstream of the outer end 37 of the leading edge 31. A larger local sector angle (θ-part) reduces the width between adjacent blades 29 of the impeller 20 and increases the risk of clogging.

[0091] According to various embodiments of the present invention, the leading edge 31 has a tilt / inclination degree along the axial direction, i.e., a tilt angle (β). The tilt angle (β) of the leading edge 31 lies in an axial plane (P3) parallel to the central axis (A) of the impeller 20. The axial plane (P3) typically does not include the central axis (A). The tilt angle (β) is determined between the following:

[0092] - An inclined line extending between the inner end 36 and the outer end 37 of the front edge 31, and

[0093] - The transverse plane of pump 1 (P2).

[0094] The tilt angle (β) is in the range of 0-35 degrees, and the outer end 37 of the front edge 31 is located upstream of the inner end 36 of the front edge 31.

[0095] It should be noted that in some embodiments, the tilt angle (β) can be negative, i.e., in the range of -15 to 0 degrees, wherein the outer end 37 of the front edge 31 is located downstream of the inner end 36 of the front edge 31.

[0096] According to various embodiments of the present invention, reference is made to Figure 1-2 Line 43 connects to a lifting handle 44, which in turn connects to the pump top 26. Line 43 extends through the interior of the column 2 to a fixed point located above the column 2; preferably, the extension of line 43 coincides with the extension of the centerline of the pump 1. Furthermore, at least one power cable 5 of the pump 1 exits from the pump top 26, is attached to line 43, and extends along line 43 to a horizontal position above the column 2. The purpose of attaching the power cable 5 to line 43 is that a freely suspending power cable would be affected by the rotational component of the velocity in the liquid flow within the column 2, thus risking rotation around the inner surface of the column 2 and abrasion against the inner surface of the column 2, potentially resulting in fragmentation.

[0097] The following is for reference. Figure 9 , Figure 9 A schematic diagram showing the sweep angle (α) of an example impeller at different relative radii R* is disclosed, and the intervals of the sweep angle (α) at ​​the first relative radius R*1 and the second relative radius R*2 are also disclosed.

[0098] Possible variations of the invention

[0099] This invention is not limited to the embodiments described above and shown in the accompanying drawings, which are primarily illustrative and exemplary. This patent application will cover all modifications and variations of the preferred embodiments described herein, and therefore the invention is defined by the wording of the appended claims and their equivalents. Thus, the apparatus can vary in various ways within the scope of the appended claims. Any subject matter falling outside the scope of the claims is provided for informational purposes and to place the invention within its relevant context.

[0100] It should also be noted that all information regarding terms such as above, below, upper, lower, etc., should be interpreted / read as referring to a device oriented according to the accompanying drawings, which are oriented to enable proper reading of the references. Therefore, these terms only indicate the relationships in the illustrated embodiments, and these relationships may change when the device of the present invention is provided with another structure / design.

[0101] It should also be noted that even if it is not explicitly stated that a feature from a particular embodiment can be combined with a feature from another embodiment, such combination should be considered obvious when feasible.

[0102] Throughout this specification and the following claims, unless the context otherwise requires, the word “comprising” and its variations shall be construed as implying the inclusion of the stated integer or step or group of integers or steps, but not excluding any other integer or step or group of integers or steps.

Claims

1. A submersible semi-axial flow centrifugal pump (1), the submersible semi-axial flow centrifugal pump being mounted in a column (2) and configured for pumping a liquid comprising solid matter, the submersible semi-axial flow centrifugal pump comprising: - An external pump housing (7), the pump housing (7) having an axial inlet opening (12) and an axial outlet opening (13), and - An internal pump core assembly (14), the internal pump core assembly (14) comprising: - Drive unit (16), said drive unit (16) being at least partially surrounded by pump housing (7), - A semi-axial flow open centrifugal impeller (20), which is suspended on the drive unit (16) and located near the inlet opening (12) of the pump housing (7), and - Multiple guide vanes (15) extend between the pump housing (7) and the drive unit (16) of the pump core assembly (14) and connect the pump housing (7) and the drive unit (16). The impeller (20) includes a hub (28) and at least two helical swept blades (29), which are connected to the hub (28) and extend radially from the hub (28). The hub (28) is a generally conical shape that tapers towards the inlet opening (12) of the pump housing (7). Each helical swept blade (29) includes a front edge (31) facing the inlet opening (12) of the pump housing (7), a rear edge (32) facing the outlet opening (13) of the pump housing (7), and a lower edge (33). The lower edge (33) extends from the front edge (31) to the rear edge (32), and the lower edge (33) is located near the inner surface (11) of the pump housing (7). The impeller (20) is characterized in that the leading edge (31) of each spiral sweeping blade (29) sweeps backward from the inner end (36) located at the hub (28) toward the outer end (37) located at the inner surface (11) of the pump housing (7), and the outer end (37) of the leading edge (31) is located upstream of the inner end (36) of the leading edge (31). -In this case, the central axis (A) of the impeller (20) is located at a relative radius R* equal to 0, and the outer end (37) of the leading edge (31) of each spiral sweeping blade (29) of the impeller (20) is located at a relative radius R* equal to 1. - The sweep angle (α) of the leading edge (31) is in the range of 32-45 degrees at the first relative radius R*1 equal to 0.5, and in the range of 47-60 degrees at the second relative radius R*2 equal to 0.95, and increases continuously from the first relative radius R*1 to the second relative radius R*2. - The sweep angle (α) at ​​any given relative radius R* of the leading edge (31) lies in the first geometric plane (P1) determined by the following: - A first vector (V1), which is tangent to the average line (38) of the helical sweep blade (29) at a given relative radius R* of the leading edge (31), and - The second vector (V2), which is tangent to the front edge (31) at a given relative radius R*, and - The sweep angle (α) is determined between the following: - A first vector (V1), which is tangent to the average line (38) of the helical sweep blade (29) at a given relative radius R* of the leading edge (31), and - Third vector (V3), which is perpendicular to the front edge (31) at a given relative radius R*.

2. The submersible semi-axial flow centrifugal pump (1) according to claim 1, wherein: The sweep angle (α) of the leading edge (31) is in the range of 32-40 degrees at the first relative radius R*1 equal to 0.5, and in the range of 47-55 degrees at the second relative radius R*2 equal to 0.95, and increases continuously from the first relative radius R*1 to the second relative radius R*2.

3. The submersible semi-axial flow centrifugal pump (1) according to claim 1 or 2, wherein: The inner end (36) of the leading edge (31) of each spiral sweep blade (29) of the impeller (20) is located at a third relative radius R*3 in the range of 0.25 to 0.45, preferably in the range of 0.25 to 0.

35.

4. The submersible semi-axial flow centrifugal pump (1) according to any one of the preceding claims, wherein: The local sector angle (θ-part) of the projection of the leading edge (31) onto the transverse plane (P2) of the pump (1) is obtained between the following: - First line (41), the first line (41) extends from the central axis (A) of the impeller (20) to the intersection between the leading edge (31) and the first relative radius R*1, and - Second line (42), the second line (42) extends from the central axis (A) of the impeller (20) to the intersection between the leading edge (31) and the second relative radius R*2, The local sector angle (θ-part) is in the range of 25-55 degrees.

5. The submersible semi-axial flow centrifugal pump (1) according to any one of the preceding claims, wherein: The full sector angle (θ-full) projected by the leading edge (31) onto the transverse plane (P2) of the pump (1) is obtained between the following: - Inner end line (39), said inner end line (39) extends from the central axis (A) of the impeller (20) to the inner end (36) of the leading edge (31), and - Outer end line (40), which extends from the central axis (A) of the impeller (20) to the outer end (37) of the leading edge (31). The full sector angle (θ-full) is in the range of 30-70 degrees.

6. The submersible semi-axial flow centrifugal pump (1) according to any one of the preceding claims, wherein: The tilt angle (β) of the leading edge (31) lies in an axial plane (P3) parallel to the central axis (A) of the impeller (20), and the tilt angle (β) is determined between the following: - An inclined line extending between the inner end (36) and the outer end (37) of the front edge (31), and - The transverse plane (P2) of the pump (1). The tilt angle (β) is in the range of 0-35 degrees, and the outer end (37) of the front edge (31) is located upstream of the inner end (36) of the front edge (31).

7. A semi-axial flow open centrifugal impeller (20), said semi-axial flow open centrifugal impeller (20) is used in the submersible semi-axial flow centrifugal pump (1) according to any one of claims 1-6, wherein: The semi-axial flow open centrifugal impeller (20) includes a hub (28) and at least two helical swept blades (29), which are connected to and extend radially from the hub (28). The hub (28) is a generally conical shape that tapers towards the inlet opening (12) of the pump housing (7). Each helical swept blade (29) includes a front edge (31) facing the inlet opening (12) of the pump housing (7), a rear edge (32) facing the outlet opening (13) of the pump housing (7), and a lower edge (33) extending from the front edge (31) to the rear edge (32). The lower edge (33) is located near the inner surface (11) of the pump housing (7). The impeller (20) is characterized in that the leading edge (31) of each spiral sweeping blade (29) sweeps backward from the inner end (36) located at the hub (28) toward the outer end (37) located at the inner surface (11) of the pump housing (7), and the outer end (37) of the leading edge (31) is located upstream of the inner end (36) of the leading edge (31). -In this case, the central axis (A) of the impeller (20) is located at a relative radius R* equal to 0, and the outer end (37) of the leading edge (31) of each spiral sweeping blade (29) of the impeller (20) is located at a relative radius R* equal to 1. - The sweep angle (α) of the leading edge (31) is in the range of 32-45 degrees at the first relative radius R*1 equal to 0.5, and in the range of 47-60 degrees at the second relative radius R*2 equal to 0.95, and increases continuously from the first relative radius R*1 to the second relative radius R*2. - The sweep angle (α) at ​​any given relative radius R* of the leading edge (31) lies in the first geometric plane (P1) determined by the following: - A first vector (V1), which is tangent to the average line (38) of the helical sweep blade (29) at a given relative radius R* of the leading edge (31), and - The second vector (V2), which is tangent to the front edge (31) at a given relative radius R*, and - The sweep angle (α) is determined between the following: - A first vector (V1), which is tangent to the average line (38) of the helical sweep blade (29) at a given relative radius R* of the leading edge (31), and - Third vector (V3), which is perpendicular to the front edge (31) at a given relative radius R*.

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