Centrifugal pump for conveying fluid

Abstract

The invention proposes a centrifugal pump for conveying a fluid, comprising: a pump housing (2) having a central axis (C) defining an axial direction (A); a pump chamber (3); an impeller (4) arranged within the pump chamber (3) and configured for rotation about an axial direction (A); at least one discharge channel (5) for discharging fluid from the pump chamber (3); and at least one tongue (6) for guiding a fluid to the discharge channel (5) wherein the tongue (6) comprises an inner surface (61) facing the central axis (C), an outer surface (62) facing away from the central axis (C), and a leading edge (63) joining the inner surface (61) and the outer surface (62). The tongue (6) comprises at least one flow channel (7) extending through the tongue (6) from the inner surface (61) to the outer surface (62).

Description

Technical Field

[0001] The invention relates to a centrifugal pump for conveying fluids according to the preamble of the independent claim. Background Art

[0002] Centrifugal pumps for conveying fluids, for example liquids such as water, are used in many different industries. Examples are the oil and gas industry, the power generation industry, the chemical industry, the water industry or the pulp and paper industry. A centrifugal pump has at least one impeller and a pump shaft for rotating the impeller. The at least one impeller may, for example, be configured as a radial impeller, or as an axial or semi-axial impeller, or as a helical axial impeller.

[0003] A centrifugal pump may be designed as a single-stage pump with only one impeller mounted to the shaft, or as a multistage pump comprising a plurality of impellers arranged one behind the other on the shaft. Each of these impellers is arranged in a pump chamber. The pump chamber is that part of the pump in which the impeller rotates. The impellers may be arranged in an in-line arrangement, in which the axial thrust generated by a single impeller is directed in the same direction for all impellers, or in a back-to-back arrangement, in which the axial thrust generated by a first set of impellers is directed in the opposite direction to the axial thrust generated by a second set of impellers.

[0004] The centrifugal pump may be configured as a volute-type pump in which a pump chamber is configured as a volute chamber, or as a diffuser-type pump in which a pump casing includes a diffuser that surrounds the pump chamber and has a plurality of fixed diffuser vanes.

[0005] When the pump chamber is configured as a volute chamber, the distance between the inner wall delimiting the volute chamber and the central axis of the pump housing increases when viewed in the flow direction towards the discharge channel through which the fluid leaves the volute chamber. The tongue separates the start of the discharge channel from the volute chamber. At the tongue, the radial distance of the impeller from the inner wall delimiting the volute chamber is minimal. The tongue in a volute pump is also referred to as a cutwater, a cutwater tongue or a separator rib. It is also known to design a volute pump with two cutwaters which are displaced by approximately 180° relative to each other when viewed in the circumferential direction of the volute chamber.

[0006] In a diffuser pump, the pump chamber is usually constructed as a circular pump chamber. A plurality of discharge channels are provided, each of which is arranged between and limited by two adjacent fixed diffuser blades. Thus, the leading edge of each diffuser blade constitutes a tongue that separates the start of the discharge channel from the pump chamber.

[0007] Thus, volute pumps and diffuser pumps have in common the provision of at least one tongue at which the discharge channel leaves the pump chamber. Within the framework of the present application, the term tongue is used both to refer to the water divider in a volute pump and to refer to the leading edge of a fixed diffuser vane in a diffuser pump.

[0008] Nowadays, in many applications, efforts are made to utilize pumps most efficiently. It is desirable to have the highest possible ratio of power delivered by the pump (especially hydraulic power) to the power required to drive the pump. This desire is mainly based on an increased awareness of environmental protection and responsible handling of available resources and on the basis of increasing energy costs. Therefore, all pumps, regardless of their embodiment, are sized and optimized to operate at or near the best efficiency point (BEP). The BEP is the point in the pump head curve at which the pump efficiency is highest.

[0009] Figure 1 The diagram in FIG. 1 shows three different pump head curves H1, H2 and H3 for the relationship between the pump head H and the flow rate Q delivered by the pump, namely Figure 1 In the diagram, the flow rate Q is plotted against the head H. Figure 1 Three different curves are shown in Figure 1. Curve H1 indicates a well-defined relationship, where each head belongs to exactly one flow rate and vice versa. Curve H1 starts at a point with no flow (also called shut-off head) and gradually decreases until it reaches a point with maximum flow (also called runout point). The BEP (not shown) is typically located at 80% of the maximum flow rate of curve H1.

[0010] Curves H2 and H3 show pump head curves with instability at part load flow. The relationship between head H and flow Q is no longer one-to-one. There are multiple values ​​of head H for which there are at least two or even three different values ​​of flow Q.

[0011] This can lead to instabilities such as saddle instability or drop to shut-off instability. Curve H2 shows the pump head curve with saddle instability. Curve H3 shows drop to shut-off instability.

[0012] This pump head curve instability has been observed for a variety of centrifugal pumps. The modifications or redesigns required to avoid this behavior are difficult to determine and will vary depending on the type of pump. Performance instabilities will only become apparent once the pump has been tested. Any changes made at this stage may result in significant increases in cost and lead time.

[0013] When the pump is operated at or near the BEP, the absolute inlet flow angle, commonly referred to as α3, is at an optimum. This angle α3 describes the flow direction of the fluid to be pumped against the leading edge of the tongue. During normal operation of the pump at or near the BEP, the angle α3 has an optimum value, so that the incident fluid is smoothly or insufficiently directed around the tongue into the discharge channel.

[0014] In everyday use of the pump, it is possible that the pump is not operated at the BEP, due to, for example, a reduction in flow rate (due to the gradual development of unfavorable inlet conditions or, for example, intentionally caused by the user because the demand for the fluid to be pumped is low). Therefore, the pump can operate in the low flow region of the pump head curve. At reduced flow rates (i.e., away from the BEP), the absolute inlet flow angle α3 changes and generally decreases with decreasing flow. This leads to stagnation and turbulence, especially in the discharge channel. The kinetic energy of the fluid leaving the volute chamber or diffuser through the discharge channel is greatly reduced, especially in those areas of the discharge channel adjacent to the tongue. This reduction in boundary layer flow can lead to stagnation and turbulence, causing the overall performance of the pump to be reduced. This problem exists in a similar manner in both volute pumps and diffuser pumps. Summary of the invention

[0015] Starting from this state of the art, the object of the present invention is therefore to propose a centrifugal pump with increased stability of the pump head curve at low flow rates.

[0016] The subject matter of the invention which meets these objects is characterized by the features of the independent claims.

[0017] Therefore, according to the present invention, a centrifugal pump for conveying fluid is proposed, the centrifugal pump comprising: a pump housing having a central axis defining an axial direction; a pump chamber; an impeller arranged in the pump chamber and configured to rotate about the axial direction; at least one discharge channel for discharging fluid from the pump chamber; and at least one tongue for guiding the fluid to the discharge channel, wherein the tongue comprises an inner surface facing the central axis, an outer surface facing away from the central axis, and a leading edge connecting the inner surface and the outer surface. The tongue comprises at least one flow channel, and the at least one flow channel extends from the inner surface through the tongue to the outer surface.

[0018] Providing the at least one flow channel in the tongue causes the fluid to flow from the inner surface across the tongue to the outer surface of the tongue. The flow supplies additional kinetic energy to the fluid in the discharge channel. In particular, this additional kinetic energy is delivered to the fluid boundary layer adjacent to the outer surface of the tongue. This at least partially compensates for the energy losses in the fluid boundary layer in the discharge channel at low flows. The fluid injected through one or more flow channels in particular re-energizes the fluid in the boundary layer at the outer surface of the tongue (i.e., in the discharge channel where stagnation may occur). By injecting the fluid through the (multiple) flow channels, the occurrence of stagnation is at least greatly suppressed, so that instabilities in the pump performance are strongly reduced or avoided. Qualitatively speaking, the pump head curve looks like Figure 1 Curve H1 in .

[0019] Thus, part of the fluid flowing through the flow channel(s) in the tongue (also referred to as bypass flow) passes through the flow channel(s) without major energy losses and subsequently releases energy to the fluid in the discharge channel (also referred to as the main flow), in particular to the boundary layer at the outer surface of the main flow. This results in an increase in kinetic energy in the main flow and at the same time suppresses stagnation in the discharge channel. Thus, by stimulating the boundary layer flow, the overall pump performance is improved.

[0020] An important advantage of the at least one flow channel is that the pattern, shape and number of flow channels can be adjusted depending on the specific pump or specific operating parameters or specific application or observed type of instability. It is thus possible to construct the tongue with or adapt the tongue with one or more such flow channels for different applications. Instabilities can be easily removed without major construction work, even after the pump has been tested. As a further advantage of the flow channel(s), it has been noted that the flow channel(s) can be provided without affecting the pump performance at or near the BEP, i.e. at partial load or low flow, the at least one flow channel reliably prevents or at least greatly reduces instabilities, but at or near the BEP, the one or more flow channels have no effect or at most a negligible effect on the pump performance. This is very advantageous since in most cases the pump is mainly operated at or near the BEP.

[0021] Another important advantage of implementing at least one flow channel in the tongue is that in the event of instabilities in the pump head curve at low flows, an improvement in pump performance at low flows can be obtained without major modifications to the pump, compared to other solutions such as replacing pump parts. This not only avoids pump downtime, but also eliminates the need for a technician to rebuild the pump. This of course saves considerable costs. From a cost perspective, there are significant savings compared to redesigning the components.

[0022] The configuration with the at least one flow channel in the tongue can be used for all types of centrifugal pumps, for example in single-stage pumps or multi-stage pumps. In particular, the configuration can be used not only for both diffuser pumps and volute pumps, but also for other types of pumps having at least one tongue for guiding the fluid from the pump chamber to the discharge channel.

[0023] In some embodiments, the pump housing includes a plurality of tongues and a plurality of discharge channels, wherein each tongue is configured to direct fluid into one of the discharge channels, and wherein each tongue includes at least one flow channel extending from an inner surface of the tongue through the tongue to an outer surface.

[0024] In some embodiments, the pump chamber is configured as a volute chamber. This includes the possibility that the volute chamber is configured with exactly one tongue (water distributor) and one discharge channel or with more than one tongue (water distributor) and more than one discharge channel. In particular, the volute chamber can be configured with exactly two tongues (water distributors) and two discharge channels. When viewed in the circumferential direction of the volute chamber, the two tongues are preferably displaced by about 180° relative to each other.

[0025] In other embodiments, the pump housing includes a diffuser surrounding the pump chamber and having a plurality of fixed diffuser vanes, each of the plurality of fixed diffuser vanes including one of the tongues for directing fluid into one of the discharge passages.

[0026] An advantageous measure is that each tongue comprises a plurality of flow channels, each of the plurality of flow channels extending from an inner surface of the tongue through the tongue to an outer surface.

[0027] Preferably, each discharge channel has an inlet area, which is the cross-sectional area of ​​the discharge channel at the leading edge of the tongue-shaped piece that defines the discharge channel, wherein the total flow cross-section of all flow channels provided in the corresponding tongue-shaped piece is at least 8% and at most 45% of the inlet area, preferably at most 30% and particularly preferably at most 20% of the inlet area.

[0028] In addition, it is preferred that for each tongue-shaped element, all flow channels are arranged in an angular area, which is bounded by a leading edge tangent from the center axis to the leading edge and a straight boundary line from the center axis to the tongue-shaped element, wherein the leading edge tangent and the boundary line include an angle from 2° to 20°. In a particularly preferred embodiment, the angle is between 10° and 20°. The boundary line and the leading edge tangent are located in a common plane, which is perpendicular to the axial direction. When the (multiple) flow channels of the corresponding tongue-shaped element are arranged adjacent to the leading edge of the tongue-shaped element in the angular area, the pressure drop on each flow channel (i.e., the pressure difference between the pressure prevailing at the inner surface of the tongue-shaped element and the pressure prevailing at the outer surface) is in any case large enough to generate a strong fluid flow through the flow channel and inject the fluid into the discharge channel at the outer surface of the tongue-shaped element.

[0029] Furthermore, it is advantageous when each flow channel is constructed as a straight channel extending obliquely relative to the leading edge tangent of the corresponding tongue. The advantage of the oblique design is that the energy input from the bypass flow to the main flow is better. The straight channel design is easier to produce and is therefore more cost-effective.

[0030] Preferably, each flow channel is configured to have an inclination angle, which is the angle between the flow channel and the inner surface of the tongue at a position where the inner surface is at a minimum distance from the central axis, wherein the inclination angle is preferably between -45° and 45°.

[0031] The optimum inclination angle depends on the specific pump or the specific application, respectively. Depending on the angle at which the fluid flows against the leading edge of the tongue, the flow channel(s) can be adjusted in advance for the specific conditions to ensure efficient performance of the pump.

[0032] In some embodiments, at least one flow channel is configured as a closed channel (e.g., a channel) extending inside the tongue. The term "closed channel" is to be understood as a channel that is completely closed on all sides or along the entire circumference, respectively, so that the inlet of the channel and the outlet of the channel are the only openings through which a fluid can enter or leave the channel. In contrast, an "open channel" designates a channel that is not limited by walls in a direction perpendicular to its main flow direction (and therefore in a direction perpendicular to its longitudinal extension), but it is open. Thus, for example, a channel with U-shaped or V-shaped walls is an open channel. If the open side of the U-shaped profile or the V-shaped profile is covered with a plate, the channel will be a closed channel.

[0033] It is also possible that at least one flow channel is configured as an open channel, preferably as a groove.

[0034] These two configurations, open flow channels and closed channels respectively, can be produced, for example, by machining methods such as drilling or milling. It is also possible to chemically etch the channels into the tongue.

[0035] According to a preferred embodiment, at least two flow channels are arranged in a first row extending in the axial direction, wherein the first row comprises at most six flow channels.

[0036] Furthermore, it is preferred that at least two flow channels are arranged in a second row extending perpendicularly to the axial direction, wherein the second row includes at most six flow channels.

[0037] According to a further preferred configuration, each tongue comprises a plurality of flow channels, wherein the flow channels are arranged in the form of a matrix. Preferably, the maximum number of the matrix is ​​three rows and three columns, so that the matrix is ​​at most a 6x6 matrix.

[0038] Further advantageous measures and embodiments of the invention are apparent from the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention will be explained in more detail below with reference to embodiments of the invention and with reference to the accompanying drawings. The accompanying drawings are shown in schematic representation:

[0040] Figure 1 is a chart with three different pump head curves,

[0041] Figure 2 is a cross-sectional view of a first embodiment of a centrifugal pump according to the present invention,

[0042] Figure 3 is a cross-sectional view of the first embodiment in a section perpendicular to the axial direction,

[0043] Figure 4 is with Figure 3 Similar but cross-sectional view of a second embodiment of a centrifugal pump according to the invention,

[0044] Figure 5 is a cross-sectional view of a section of the tongue-shaped member of the first embodiment,

[0045] Figure 6 yes Figure 5 An enlarged view of the tongue shown in

[0046] Figure 7 is a perspective view of a first variant of the tongue, and

[0047] Figure 8 is a schematic diagram of a second variant of the tongue. DETAILED DESCRIPTION

[0048] A diagram showing three pump head curves H1, H2, H3 Figure 1 This has already been discussed in the introduction, so there is no need to dwell on Figure 1 Make further comments.

[0049] Figure 2 is a cross-sectional view of a first embodiment of a centrifugal pump according to the present invention, which is indicated as a whole by reference numeral 1 and comprises a pump housing 2. The centrifugal pump 1 comprises: an inlet 101, through which a fluid (in particular a liquid, such as water) can enter the pump 1; and an outlet 102, which is used to discharge the fluid. The pump 1 further comprises at least one impeller 4 for acting on the fluid. The impeller 4 is arranged in a pump chamber 3 of the pump housing 2. During operation, the impeller 4 rotates around an axis of rotation defined in an axial direction A. The pump housing 2 comprises a central axis C coinciding with the axis of rotation of the pump 1. Therefore, the axial direction A is defined by the central axis C of the pump housing 2 or, equivalently, by the axis of rotation (around which the impeller 4 rotates during operation).

[0050] In the following, two different pump types are mentioned, namely volute pumps and diffuser pumps. Volute refers to pumps 1 in which the pump chamber 3 is designed as a volute chamber 8 . Figure 2 and Figure 3 Such a design is shown in . In a diffuser pump, the pump chamber 3 is surrounded by a diffuser 9 . Figure 4 Such a configuration is shown in .

[0051] The direction perpendicular to the axial direction A is referred to as the 'radial direction'. The term 'axial' or 'axially' is used in the ordinary sense of 'in the axial direction' or 'relative to the axial direction'. In a similar manner, the term 'radial' or 'radially' is used in the ordinary sense of 'in the radial direction' or 'relative to the radial direction'.

[0052] Figure 2 The pump 1 is shown in a cross section parallel to the axial direction A, more precisely the center axis C lies in the plane of the cross section. The impeller 4 is mounted on the shaft 103 in a torque-proof manner. By means of the shaft 103 extending in the axial direction A, the impeller 4 is driven during operation of the pump 1 so as to rotate about the axial direction A. The shaft 103 is driven by means of a drive unit (not shown) to which the shaft 103 is coupled, such as an electric motor or any other type of motor. In a manner known per se, the shaft 103 and the impeller 4 are supported by a bearing unit 104. A sealing unit 105 is provided for sealing the shaft 103 against leakage of fluid along the shaft 103.

[0053] Figure 3 The first embodiment of the pump 1 is shown in a cross section perpendicular to the axial direction A (as shown by Figure 21-1). A cross-sectional view in FIG. 1 (indicated by the cutting line III-III in FIG. 1 ). Here, the pump chamber 3 is configured as a volute chamber 8. The pump housing 2 includes a volute chamber 8 for receiving an impeller 4 and a discharge channel 5 for guiding the fluid to the outlet 102. The liquid flow from the inlet 101 enters the volute chamber 8 generally in the axial direction A, and is then turned in the circumferential direction by the impeller 4. As a characteristic of the volute chamber 8, when viewed in the flow direction toward the discharge channel 5, the distance between the inner wall defining the volute chamber 8 and the central axis C of the pump housing 2 increases, thereby constructing a flow channel for the fluid, which widens in the flow direction. The pump housing 2 further includes at least one tongue-shaped member 6 for guiding the liquid into the discharge channel 5, that is, the tongue-shaped member 6 divides the flow channel so that the liquid flows along both sides of the tongue-shaped member 6. The tongue-shaped member 6 is also called a separator rib or a water-dividing tongue-shaped member or a water-dividing member.

[0054] Figure 3 The first embodiment shown in FIG. 1 is configured with two tongues 6. The tongues 6 are arranged at positions displaced 180° relative to each other when viewed in the circumferential direction of the volute chamber 8. The design with two tongues 6 is known in the art per se and therefore does not require a more detailed explanation. The main reason for providing two tongues 6 in the pump housing 2 is to balance the radial thrust acting on the impeller 4.

[0055] Although the embodiment described here comprises two tongues 6 , it must be understood that the invention also comprises embodiments in which the pump housing 2 is designed with only one tongue 6 .

[0056] Each tongue 6 comprises an inner surface 61 facing the central axis C, an outer surface 62 facing away from the central axis C, and a leading edge 63, which is an axially extending edge of the tongue 6 facing the fluid flow, i.e., at the leading edge 63 the fluid flow is separated. The leading edge 63 constitutes the upstream end of the tongue 6. Therefore, the inner surface 61 of the respective tongue 6 is the lateral surface of the tongue 6 closer to the central axis C, and the outer surface 62 of the respective tongue 6 is the lateral surface of the tongue 6 further away from the central axis C. The leading edge 63 connects the inner surface 61 and the outer surface 62. Each of the discharge channels 5 has an inlet area 51, which is the cross-sectional area of ​​the discharge channel 5 at the leading edge 63 of the tongue 6 delimiting the discharge channel 5. The inlet area 51 is also called the throat area or the narrowest area of ​​the channel 5. The inlet area 51 is the area of ​​the discharge channel 5 adjacent to the leading edge, at which the flow cross section of the discharge channel 5 has its minimum value.

[0057] Figure 4 Shown with Figure 3A cross-sectional view of a second embodiment of a centrifugal pump 1 similar but according to the invention. The second embodiment is constructed as a diffuser pump 1 comprising a diffuser 9, which surrounds a pump chamber 3 and has a plurality of fixed diffuser blades 91, each of which comprises a tongue or leading edge 6 for directing the fluid into one of the discharge channels 5. Each discharge channel 5 is arranged between two adjacent diffuser blades 91 and has an inlet area 51, which is the cross-sectional area of ​​the discharge channel 5 at the leading edge 63 of the tongue 6 that delimits the discharge channel 5. Likewise, each of the tongues 6 has an inner surface 61 and an outer surface 62, as already described and explained with respect to the first embodiment. Unlike the volute chamber 8 of the first embodiment, the pump chamber 3 of the second embodiment (i.e., the diffuser pump 1) has a circular cross-section perpendicular to the axial direction A. In the center of the diffuser 9, the impeller 4 is schematically shown by two circles.

[0058] It goes without saying that the reference numerals apply to Figure 4 Each diffuser vane 91 or tongue 6 is shown in FIG.

[0059] Figure 5 A cross-sectional view showing a section of a tongue 6, which is a volute pump (first embodiment, Figure 3 ) of the tongue 6 or the diffuser pump (second embodiment, Figure 4 ) is one of the tongues 6 of the volute pump. The configuration of the tongue 6 of the volute pump can be the same as or similar to the configuration of the tongue 6 of the diffuser pump.

[0060] Therefore, the following description of the configuration of the tongue 6 , which is made by way of example with reference to the volute pump according to the first embodiment, applies analogously to the diffuser pump according to the second embodiment.

[0061] For better understanding, Figure 6 Shows Figure 5 An enlarged view of the tongue 6 is shown in FIG.

[0062] According to the invention, the tongue 6 comprises at least one flow channel 7 extending through the tongue 6 from an inner surface 61 of the tongue 6 to an outer surface 62 . Figure 5 and Figure 6 The embodiment of the tongue 6 in is provided with five flow channels 7, each of which extends across the tongue 6 and constitutes a flow connection between an inner surface 61 and an outer surface 62 arranged in the tongue 6. The flow channels 7 are arranged parallel to each other.

[0063] The number of five flow channels is merely exemplary. In other embodiments, the tongue 6 may be provided with fewer flow channels 7, for example only one flow channel 7 or only two flow channels 7. In other embodiments, the tongue 6 may be configured with more than five flow channels 7, such as in Figure 7 As shown in .

[0064] During operation of the pump 1, at least in the region adjacent to the leading edge 6 of the tongue 6, the pressure prevailing at the inner surface 61 is generally higher than the pressure prevailing at the outer surface 62. Due to the pressure difference, the fluid flows from the inner surface 61 of the tongue 6 through the flow channel 7 to the outer surface 62. As a result, fluid jets are generated, which transport energy, in particular kinetic energy, from the inner surface 61 of the tongue 6 to the outer surface 62. In particular, the energy is delivered to the boundary layer of the fluid at or in the immediate vicinity of the outer surface 62. As a result, said boundary layer of the fluid is re-energized by the fluid jets leaving the flow channel 7. As a result of this re-energization, stagnation, turbulence or eddy accumulation is reliably prevented or at least greatly reduced.

[0065] Of course, the appropriate number of flow channels 7, the appropriate configuration of the flow channels 7 and the appropriate arrangement of the flow channel(s) 7 depend on the specific centrifugal pump 1 or pumping system or the specific application for which the pump 1 is used. It is no problem for the skilled person to provide the appropriate flow channel(s) 7 for the specific pump 1 and / or application.

[0066] Practical experience has shown that for many applications it is advantageous when the total flow cross section of all flow channels 7 in the tongue 6 (i.e. the sum of the flow cross sections of the individual flow channels) is at least 8% and at most 45% of the inlet region 51. As already explained, the inlet region 51 (which is also referred to as the throat region) is the flow cross section of the respective discharge channel 5 at the inlet of the discharge channel (i.e. at the leading edge 63 of the tongue 6 delimiting the respective discharge channel 5).

[0067] Furthermore, practice has revealed that it is advantageous to arrange all flow channels 7 in a region adjacent to the leading edge 63 of the respective tongue 6. The preferred region of the flow channel(s) 7 can be described as an angular region bounded by two straight lines, namely the leading edge tangent line T and the straight boundary line B. The two straight lines B, T lie in a common plane, which is perpendicular to the axial direction A.

[0068] The leading edge tangent line T is a tangent line from the central axis C to the leading edge 63, and the straight boundary line B is a straight line from the central axis C to the inner surface 61 of the tongue 6. The boundary line B and the leading edge tangent line T include an angle α, which is preferably at least 2° and at most 20°.

[0069] Therefore, the preferred area (in which the flow channel 7 is arranged, more precisely, in which the openings of all flow channels 7 in the inner surface 61 of the tongue-shaped member 6 are arranged) is defined by the angular area defined by the leading edge tangent line T and the boundary line B, wherein the angle α between the two lines B and T is at least 2° and at most 20°.

[0070] Furthermore, based on practical experience and because the manufacturing is very simple, it is preferred that each flow channel 7 is constructed as a straight flow channel 7. Figure 5 and Figure 6 As shown in FIG. 6 , it is preferred that each flow channel 7 is configured as a straight channel 7 extending obliquely relative to a tangent line T of a front edge of the tongue 6 .

[0071] Preferably, each flow channel 7 is configured to have an inclination angle β, which is the angle between the straight flow channel 7 and the inner surface 61 of the tongue 6 at a position where the distance of the inner surface 61 from the central axis C has a minimum value. Figure 5 The distance R3 defines the radius of a circle C3, the center of which is located on the central axis C and is tangent to the tongue 6. The diameter of this circle C3 is also referred to by the technician as D3. D3 is the diameter of the diffuser pump (second embodiment, Figure 4 ) of the diffuser blade leading edge diameter or volute pump (first embodiment, Figure 3 ) is a common indication of the diameter of the volute water distributor.

[0072] Since the circle C3 is tangential to the tongue 6 , the circle C3 and the tongue 6 have only one common point, namely the point where the circle C3 touches the tongue 6 . Figure 5 and Figure 6 The straight line G shown in FIG. 5 is tangent to the circle C3 at this common point, wherein the circle C3 contacts the tongue 6. The inclination angle β is the angle between the straight flow channel 7 and the straight line G. Preferably, the inclination angle β is between -45° and 45°. A positive inclination angle of 0°<β≤45° means that, when viewed in the flow direction of the fluid in the discharge channel 5, the opening of the corresponding flow channel 7 in the inner surface 61 is in front of the opening of the flow channel 7 in the outer surface 62. Figure 5 and Figure 6 Such a configuration is shown in . A negative inclination angle of −45°≤β<0° means that, when viewed in the flow direction of the fluid in the discharge channel 5 , the opening of the respective flow channel 7 in the inner surface 61 is behind the opening of the flow channel 7 in the outer surface 62 .

[0073] Each of the flow channels 7 may be configured as a closed channel (e.g., a channel) extending inside the tongue 6. When configured as a closed flow channel 7, the flow channel 7 is completely closed on all sides or along its entire circumference, respectively, so that the inlet of the flow channel 7 and the outlet of the flow channel 7 are the only openings through which a fluid may enter or leave the flow channel 7. The closed flow channel 7 may, for example, be configured as a borehole drilled into the tongue.

[0074] Figure 7 Shows Figure 5 and Figure 6 0026] A perspective view of a first variant of the tongue 6 shown in FIG. According to the first variant, the tongue 6 comprises a plurality of flow channels 7. The flow channels 7 are arranged in a first row FR extending in the axial direction A. The first row FR comprises two flow channels 7. Preferably, at most six flow channels 7 are arranged in the first row FR. A second row SR extends perpendicularly to the first row FR and therefore also perpendicularly to the axial direction A, the second row comprising five flow channels 7. Preferably, at most six flow channels 7 are arranged in the second row SR. The arrangement of the flow channels 7 is in the form of a matrix. Taking into account the preferred maximum of six flow channels 7 in the rows FR and SR, the preferred maximum size of the matrix is ​​a 6x6 matrix.

[0075] It has to be noted that in other embodiments of the tongue 6, only a first row FR of flow channels 7 or only a second row SR of flow channels is provided. Furthermore, in other embodiments, the number of flow channels 7 arranged in the first row FR is different from the number of flow channels in the second row SR. Furthermore, it has to be noted that the flow channels 7 in the first row FR are not necessarily aligned (with respect to the axial direction A). Moreover, the flow channels 7 of the second row are not necessarily aligned.

[0076] Figure 8 A schematic diagram of a second variant of the tongue 6 is shown. In the second variant, the flow channels 7 are configured as open flow channels 7 (preferably grooves), which can be produced, for example, by machining (such as milling). An open flow channel 7 designates a flow channel 7 which is not defined by walls in a direction perpendicular to its main flow direction (and therefore in a direction perpendicular to its longitudinal extension), but it is open. The open flow channel 7 has, for example, a U-shaped or V-shaped profile. With regard to the flow channels 7 configured as open flow channels 7, it is preferred that the open flow channels 7 are all arranged in an upper edge 64 which delimits the tongue 6 relative to the axial direction A.

[0077] The second variant comprises two open flow channels 7 , wherein the number of two flow channels 7 must be understood as an example.

[0078] In other embodiments of the tongue 6 , the tongue 6 includes both one or more flow channels 7 configured as closed flow channels 7 and one or more flow channels 7 configured as open flow channels 7 .

Claims

1. A centrifugal pump for conveying fluid, the centrifugal pump include: a pump housing (2) having a central axis (C) defining an axial direction (A); Pump room (3); an impeller (4) arranged in the pump chamber (3) and configured to rotate about the axial direction (A); at least one discharge channel (5) for discharging the fluid from the pump chamber (3); and at least one tongue-shaped member (6) for guiding the fluid to the discharge channel (5), wherein the tongue-shaped member (6) includes an inner surface (61) facing the central axis (C), an outer surface (62) facing away from the central axis (C), and a leading edge (63) connecting the inner surface (61) and the outer surface (62), characterized in that the tongue-shaped member (6) includes at least one flow channel (7), and the at least one flow channel extends from the inner surface (61) through the tongue-shaped member (6) to the outer surface (62).

2. The centrifugal pump according to claim 1, in, The pump housing (2) comprises a plurality of tongue-shaped members (6) and a plurality of discharge channels (5), wherein each tongue-shaped member (6) is configured to guide the fluid into one of the discharge channels (5), and wherein each tongue-shaped member (6) comprises at least one flow channel (7), wherein the at least one flow channel extends from the inner surface (61) of the tongue-shaped member (6) through the tongue-shaped member (6) to the outer surface (62).

3. A centrifugal pump according to any one of the preceding claims, in, The pump chamber (3) is designed as a volute chamber.

4. The centrifugal pump according to claim 2, in, The pump housing (2) comprises a diffuser (9) which surrounds the pump chamber (3) and has a plurality of fixed diffuser blades (91), each of which comprises one of the tongues (6) for directing the fluid into one of the discharge channels (5).

5. A centrifugal pump according to any one of the preceding claims, in, Each tongue (6) comprises a plurality of flow channels (7), each of the plurality of flow channels extending through the tongue (6) from the inner surface (61) to the outer surface (62) of the tongue (6).

6. A centrifugal pump according to any one of the preceding claims, in, Each discharge channel (5) has an inlet area (51), which is the cross-sectional area of ​​the discharge channel (5) at the leading edge (63) of the tongue (6) delimiting the discharge channel (5), and wherein the total flow cross-section of all flow channels (7) provided in the respective tongue (6) is at least 8% and at most 45% of the inlet area (51).

7. A centrifugal pump according to any one of the preceding claims, in, For each tongue (6), all flow channels (7) are arranged in an angular region defined by a leading edge tangent (T) from the center axis (C) to the leading edge (63) and a straight boundary line (B) from the center axis (C) to the tongue (6), wherein the leading edge tangent (T) and the boundary line (B) comprise an angle (α) from 2° to 20°.

8. A centrifugal pump according to any one of the preceding claims, in, Each flow channel (7) is configured as a straight channel extending obliquely relative to the leading edge tangent line (T) of the corresponding tongue (6).

9. A centrifugal pump according to any one of the preceding claims, in, Each flow channel (7) is configured to have an inclination angle (β), which is the angle between the flow channel (7) and the inner surface (61) of the tongue-shaped member (6) at a position where the distance of the inner surface (61) from the central axis (C) is the smallest, wherein the inclination angle (β) is between -45° and 45°.

10. A centrifugal pump according to any one of the preceding claims, in, At least one flow channel (7) is designed as a closed channel extending inside the tongue (6).

11. A centrifugal pump according to any one of the preceding claims, in, At least one flow channel (7) is designed as an open channel, preferably as a groove.

12. A centrifugal pump according to any one of the preceding claims, in, At least two flow channels (7) are arranged in a first row (FR) extending in the axial direction (A), wherein the first row (FR) comprises at most six flow channels (7).

13. A centrifugal pump according to any one of the preceding claims, in, At least two flow channels (7) are arranged in a second row (SR) extending perpendicularly to the axial direction (A), wherein the second row (SR) comprises at most six flow channels (7).

14. A centrifugal pump according to any one of the preceding claims, in, Each tongue comprises a plurality of flow channels (7), wherein the flow channels (7) are arranged in the form of a matrix.

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