elliptical, eccentric annular space
The centrifugal pump, manufactured using an elliptical eccentric annular space shell design and deep-drawing process, solves the problem of low efficiency of annular space shells made of sheet metal in unrestricted operating ranges, achieving efficient fluid flow and cost-effective manufacturing, reaching the efficiency level of a volute shell.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KSB SE & CO KGAA
- Filing Date
- 2024-12-11
- Publication Date
- 2026-07-14
AI Technical Summary
Existing centrifugal pumps with annular shells made of sheet metal are difficult to achieve a minimum efficiency index (MEI) of 0.4 or higher in an unrestricted operating range. They are also expensive to manufacture and cannot be manufactured with a volute shell through tensile or compressive deformation.
The design adopts an elliptical eccentric annular space shell, combined with deep drawing process to manufacture the shell. It utilizes eccentrically arranged impellers and elliptical base surface to construct a constant swirling flow path. By using the eccentricity and elliptical shape to approximate the profile of a volute shell, it achieves efficient flow guidance and reduces manufacturing costs through deep drawing process.
It achieves efficient fluid flow under main constant swirling flow, reaching the efficiency level of a volute, while reducing manufacturing costs and making it suitable for mass production.
Smart Images
Figure CN122396867A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a centrifugal pump having a shell in the form of a plate structure, wherein the shell is constructed as a deep-drawn component, wherein the shell has a pressure-side shell wall with an opening for fixing a pressure connector, and an impeller located inside the shell is arranged in the plane of the pressure connector opening, wherein the axis of rotation of the impeller is arranged eccentrically offset relative to the centerline of the shell, and wherein the leading edge is formed by the shell wall and the pressure connector. Background Technology
[0002] Since 2013, the Minimum Efficiency Index (MEI) in the EU has stipulated environmentally friendly design requirements for water pumps. Since 2015, an MEI of 0.4 has applied. This means that since 2015, only pumps with efficiencies better than a reference value, which is formed from the then-worst 40% of pumps available on the market, are allowed to enter the market. This suggests, and logically in the context of the energy transition, that the EU will raise the MEI in the near future, and therefore only pumps with the corresponding minimum efficiency will have a market.
[0003] From a hydraulic perspective, the volute casing of a centrifugal pump represents the most efficient geometry currently available for collecting fluid after the impeller outlet and supplying the fluid to the pump's pressure connection. Here, a simple volute is characterized by a continuously increasing cross-sectional orientation at the impeller periphery, typically designed so that the swirling flow does not change direction at the periphery.
[0004] The annular casing differs from the volute casing primarily in that its cross-sectional orientation is constant along the impeller circumference. Therefore, the annular space is also called a "tank." The geometry of the annular space results in the inability to achieve constant swirling flow due to the constant cross-section along the impeller circumference. Within the annular space, there exists a region where the cross-section is either too large or too small for the volume of fluid to be transported, leading to lower pump efficiency due to separation and turbulence.
[0005] However, annular space shells remain popular in practice because, unlike classic spiral shells, they can be fabricated cost-effectively in sheet metal implementations. Annular space shells constructed from sheet metal typically have smoother and higher-quality surfaces. This higher-quality surface is advantageous, for example, for applications with stringent hygienic requirements. Simultaneously, from a hydraulic point of view, the smoother surface, in principle, reduces wall friction losses.
[0006] DE 199 47 720 A1 discloses a centrifugal pump having a shell in the form of a plate structure, wherein the shell is constructed as a deep-drawn rotationally symmetrical component, in which the impeller is eccentrically arranged relative to the central axis of the shell.
[0007] Currently known pumps with annular space casings made of plate material can achieve a minimum efficiency index (MEI) greater than 0.4 only within limited or restricted operating ranges. If a plate-structured casing is still required for hygiene reasons, a volute casing with a plate structure can achieve the future requirement of an MEI greater than 0.4 for a virtually unrestricted operating range.
[0008] The volute casing made of sheet metal combines the hydraulic advantages of a volute with the good surface area of a toroidal space, thus achieving good efficiency. However, unlike traditional toroidal casings, the volute casing made of sheet metal cannot be manufactured by tensile or compressive deformation. To manufacture it, more expensive methods, such as hydroforming, must be used instead. Therefore, while the use of volute casings made of sheet metal improves efficiency, it also increases the manufacturing cost of the pump. Summary of the Invention
[0009] The objective of this invention is to provide a centrifugal pump with a shell having a plate-like structure, which has an advantageous minimum efficiency index (MEI). Simultaneously, the pump shell should be manufactured in large quantities with high quality and at a reasonable cost. Here, the centrifugal pump with a plate-like shell should be able to achieve fluid flow under predominantly constant swirling conditions.
[0010] According to the invention, this task is accomplished by a centrifugal pump having a shell in the form of a plate structure, as described in claim 1. Preferred variations can be found in the parallel independent claims, dependent claims, description, and drawings.
[0011] According to the present invention, the shell wall is constructed as the circumferential surface of a cylinder, wherein the cylinder has a base surface having a long axis with a long extension and a short axis with a short extension perpendicular to the long axis.
[0012] The circumferential surface of the cylinder is the total surface area of the cylinder, excluding the two top surfaces. It consists of the side surfaces of the cylinder, which are typically rectangular in shape. Therefore, the circumferential surface of the cylinder is part of the casing wall, to which the fluid flows after leaving the impeller and which restricts the fluid flow. In this respect, the casing wall of the cylinder is also fundamentally different from the design of a volute, which typically has a defined circular portion and radius.
[0013] In this regard, the definition of a cylinder used as a basis here is the general mathematical definition of a cylinder.
[0014] For example, the base of a cylinder is constructed to be elliptical. The elliptical shape of the base results in the casing of a centrifugal pump, which supports a fluid flow with constant swirl along the flow path inside the centrifugal pump.
[0015] An ellipse is a closed, curved geometric shape that differs from a circle in that it has two foci, and the sum of the distances from every point on the ellipse to these two foci is constant.
[0016] The major axis of an ellipse is one of the two axes that characterize the ellipse. It is the longer of the two axes and extends from one end of the ellipse to the other through the center of the ellipse. The major axis determines the maximum extension of the ellipse in a particular direction, thus the basal surface of the shell wall has a long extension along the major axis.
[0017] The minor axis of an ellipse is one of the two axes that characterize the ellipse. Unlike the major axis, which is the longer of the two axes, the minor axis is the shorter of the two axes. The minor axis extends perpendicularly to the major axis and extends through the center of the ellipse. It determines the minimum extension of the ellipse in a particular direction, thus the basal surface of the shell wall has a short extension along the minor axis. The minor axis, together with the major axis, forms the coordinate system of the ellipse.
[0018] In one variant of the invention, the sum of the distances between a point on the shell wall and two preset points is the same for all points on the shell wall.
[0019] For example, the preset points are implemented as foci. The foci of an ellipse are two defined points inside the ellipse, which characterize the following important geometric properties of the ellipse. The sum of the distances from every point on the ellipse to these two foci is constant and equal to the length of the major axis of the ellipse.
[0020] The position of the foci relative to the major and minor axes of the ellipse depends on the ellipse's eccentricity. When the eccentricity is zero, the foci are at the center of the major axis and coincide with the center of the ellipse. The larger the eccentricity, the farther the foci are from the center of the major axis.
[0021] In one variation of the invention, the cross-section of the space formed between the trailing edge of the impeller and the casing wall is configured to increase almost continuously in the flow direction between the sporn and the pressure pipe opening. The special elliptical shape of the centrifugal pump casing, combined with the eccentrically arranged impeller, achieves a fluid flow that is almost identical to that in a volute casing and thus enables particularly high and advantageous efficiency.
[0022] For example, in the space formed between the trailing edge of the impeller and the casing wall, the cross-section of the space is configured to continuously increase in the flow direction between the leading edge or boss and the pressure pipe opening in a region up to 270°.
[0023] In an advantageous variation of the invention, the region of continuous cross-sectional increase between the leading edge and the pressure nozzle opening is 270° in the flow direction.
[0024] In an alternative variation of the invention, the region of continuous increase in space begins after the boss, offset by about 10° in the flow direction, and ends at the transition to the pressure nozzle.
[0025] In one variation of the invention, the cross-section can be constructed without increasing at the transition to the pressure nozzle, structurally determined by the design. For example, the reduction in cross-section is implemented to a minimum, allowing the flow to proceed in an almost constant swirling manner.
[0026] However, the centrifugal pump casing does not need to be manufactured by expensive methods (such as hydraulic forming), but can be implemented as a deep-drawn sheet metal component, thereby the casing can be manufactured cost-effectively and in large quantities.
[0027] Deep drawing is a metalworking method used to stretch flat sheet metal into three-dimensional, hollow, or deep shapes. According to DIN 8584, deep drawing is the stretching and deformation of sheet metal blanks into hollow bodies with one open side. First, a flat sheet of metal is cut to the correct size and shape. A forming tool has the desired shape of the final product, while a die has a notch for the sheet metal. The sheet metal is placed between the forming tool and the die. Using a hydraulic or mechanical press, the flat sheet metal is drawn into the forming tool. Pressure and speed are carefully controlled to ensure the sheet metal is drawn evenly into the die. The sheet metal is pressed into the desired shape and deformed by pressure. It takes the outline of the forming tool and thus forms the finished part. After the deep drawing process is complete, the deformed part is removed from the forming tool.
[0028] Deep drawing offers the advantage of creating complex and precise shapes that are lightweight yet stable. It is a cost-effective method for mass production of parts because it minimizes material waste.
[0029] The elliptical eccentric annular space housing of the centrifugal pump represents a prominent solution for the task of manufacturing a housing in the form of a plate structure while simultaneously achieving a high Minimum Efficiency Index (MEI). On the one hand, the eccentricity and elliptical shape approximate the profile of a volute, thus significantly improving flow guidance; on the other hand, tensile and compressive deformation also provides suitable manufacturability for mass production.
[0030] For example, the fluid flowing through a centrifugal pump has a swirling flow, wherein the swirling flow is configured to be as constant as possible in the flow direction between the boss and the pressure pipe opening.
[0031] In one embodiment of the invention, a flattened portion of the housing wall with a pressure connector opening is provided. At this location, the pressure connector member can be inserted and, for example, welded to the housing wall.
[0032] For example, the pressure pipe opening is positioned in the casing wall such that a cross-section for fluid flow with constant swirl, originating from the elliptical base of the pump casing, is introduced into the pressure pipe such that the cross-section continuously increases until the pressure pipe is constructed. The flow-optimized casing design, combined with the eccentric arrangement of the impeller, almost perfectly suits the advantages of the volute casing, namely its ability to promote an increased flow cross-section for pressure buildup. Due to the flattened portion of the casing wall, a leading edge is formed in the pressure pipe opening, which approaches the boss of the volute casing.
[0033] The described shell construction does not compromise the advantages of a shell made from deep-drawn sheet metal in any way in terms of manufacturing and rigidity. At the same time, by combining it with the eccentric arrangement of the impeller, it significantly approximates the advantages of a volute shell in terms of efficiency and radial force orientation.
[0034] Swirling or swirling flow is a flow with a circumferential component that rotates about an axis. Here, the flow vector can have not only an axial component but also a radial component. The particles in the flow then move along helical trajectories. The swirling of a fluid is associated with its angular momentum. Angular momentum is a measure of the rotational motion of an object. In flow, swirling helps to maintain angular momentum.
[0035] The vortex flow is stabilized in the region of the boss by the eccentricity of the impeller within the casing. In an elliptical eccentric annular space casing, the vortex distribution almost perfectly approximates the constant vortex direction of a volute casing.
[0036] In one variation of the invention, the long axis is oriented by an angle α relative to the horizontal line (which extends, for example, from the impeller axis to the opening of the pressure nozzle). This further supports the construction of a continuously increasing cross-sectional area of the space between the impeller and the housing wall, and thus enables fluid flow under constant swirling conditions.
[0037] For example, the angle α is greater than 5°, preferably greater than 7.5°, especially greater than 10°, and / or less than 25°, preferably less than 20°, especially less than 15°.
[0038] In one variant, the pressure nozzle opening extends across a complete quadrant of the shell wall, originating from the boss. Thus, the pressure nozzle opening is constructed large enough that the continuously increasing flow cross-section does not taper within the opening, and does not unduly affect the flow with constant swirl in terms of efficiency.
[0039] For example, the impeller's axis of rotation is arranged in an eccentric region with a radial value e = 0.05 - 0.40. Here, the value e = 0 when the impeller center point coincides with the housing center point, and the value e = 1 when the impeller has a contact point with the housing wall.
[0040] In some variations of the invention, the rotation axis of the impeller is arranged in an eccentric region having a value of 0.10 to 0.35, preferably 0.15 to 0.30, and especially 0.20 to 0.25 in the radial direction.
[0041] For example, between the impeller and the casing, the clearance ring is eccentrically arranged at the casing.
[0042] Determined by the pressure difference between the front and rear of the impeller, a portion of the conveying medium, already under a higher static pressure, flows back through the gap between the stationary and rotating parts of the pump. The arrangement of the gap ring significantly minimizes losses through this gap. In one embodiment of the invention, a narrow gap for sealing can be achieved between the rotating impeller and the stationary, elliptically eccentric annular housing using an eccentrically arranged or constructed gap ring carrier.
[0043] Matching the eccentrically arranged impeller, the suction inlet is concentrically positioned on the casing along the impeller's axis of rotation. Thus, even when the impeller is positioned outside the center of the casing, the fluid ideally flows axially into the centrifugal pump's impeller.
[0044] According to the present invention, a centrifugal pump having a shell in the form of a plate structure, an eccentrically arranged impeller, and a shell having an elliptical base surface is used to achieve high energy efficiency during fluid transport.
[0045] Centrifugal pumps with elliptical eccentric annular space casings achieve the efficiency levels of smooth volute casings, and thus represent a cost-effective and efficient alternative to volute casings made of sheet metal. Attached Figure Description
[0046] Further features and advantages of the invention will become apparent from the description of embodiments according to the accompanying drawings and from the drawings themselves. Hereinafter: Figure 1 A top view of the elliptical eccentric casing facing the centrifugal pump is shown. Figure 2 The image shows a longitudinal section passing through the casing of the centrifugal pump. Detailed Implementation
[0047] Figure 1 The diagram shows a top view of the housing 1, which has an elliptical base surface 2 and an eccentrically arranged impeller 3. The housing 1 is constructed as a deep-drawn component. The elliptical base surface 2 has a long axis 4 with a long extension and a short axis 5 perpendicular to the long axis 4 with a short extension.
[0048] In the space 6 formed between the trailing edge of the impeller 3 and the casing wall 14 of the housing 1, the cross-section of the space 6 is configured to increase almost continuously in the flow direction between the leading edge 7, which is configured as a boss, and the pressure inlet opening 8. As a result, the swirling flow of the fluid flowing through the centrifugal pump is configured to be as constant as possible in the flow direction between the leading edge 7 and the pressure inlet opening 8.
[0049] In this variant, the centerline of housing 1 corresponds to the major axis 4. The major axis 4 of housing 1 is oriented with respect to the horizontal line 9, which is rotated by an angle α, 12° in the shown embodiment. The rotation axis 10 of impeller 3 is arranged in an eccentric region having a value of e = 0.2 in the radial direction. Here, the rotation axis 10 of impeller 3 moves radially from the intersection 12 of the major axis 4 and the minor axis 5.
[0050] The region of the space 6 formed between the trailing edge of the impeller 3 and the casing wall 14 of the housing 1, with a continuously increasing cross-section, begins in the flow direction at an angle α. During the transition to the pressure nozzle 15, structurally, this continuous increase in cross-section of the space 6 cannot be achieved over its entire circumference. However, through a specific embodiment of the centrifugal pump, the swirling of the fluid is achieved as constantly as possible.
[0051] The pressure inlet opening 8 extends clockwise from its leading edge 7 across one quadrant of the housing wall 14 of the housing 1. Thus, the pressure inlet opening 8 is constructed large enough that the continuously increasing cross-section of the space 6 does not taper within it. This promotes a flow with constant swirling properties and advantageously improves the efficiency of the centrifugal pump.
[0052] The centrifugal pump presented has achieved the efficiency level of a smooth volute casing, thus representing a cost-effective and efficient alternative to a volute casing made of sheet metal.
[0053] Figure 2 One embodiment is shown in which the suction pipe opening 11 is arranged concentrically with the rotation axis 10 of the impeller 3 at the housing 1.
[0054] A clearance ring 13 is eccentrically positioned on the housing 1 between the impeller 3 and the housing 1. The clearance ring 13 creates a sealing clearance between the internal space of the impeller 3 and the housing 1. This prevents fluid leaving the impeller 3 from flowing back to the suction inlet 11.
[0055] The housing 1 is constructed as a deep-drawn component and has a housing wall 14 on the pressure side. An opening 8 for fixing a pressure connector 15 is formed in the housing wall 14, wherein the pressure connector 15 is welded to the housing wall 14. Here, the housing wall 14 is constructed as the circumference of a cylinder.
[0056] Reference number list 1. Shell 2 Base plane 3 Impeller 4 Long axis 5. Short axis 6 spaces 7. Front Edge 8. Pressure pipe opening 9 Horizontal lines 10 Rotation axis 11. Suction pipe opening 12 intersections 13 Gap Ring 14 Shell wall 15 Pressure Take-off
Claims
1. A centrifugal pump having a housing (1) in the form of a plate structure, - in, The housing (1) is constructed as a deep-drawn component. - The housing (1) has a housing wall (14) on the pressure side, where an opening (8) is formed for fixing the pressure connector (15). - And the impeller (3) located inside the housing (1) is arranged in the plane of the pressure pipe opening (8), - Wherein, the rotation axis (10) of the impeller (3) is arranged to be offset eccentrically relative to the center line of the housing (1), - Wherein, the leading edge (7) is formed by the housing wall (14) and the pressure pipe (15), Its features are, The shell wall (14) is constructed as the circumferential surface of a cylinder, wherein the cylinder has a base surface (2), the base surface having a long axis (4) with a long extension and a short axis (5) with a short extension perpendicular to the long axis (4).
2. The centrifugal pump according to claim 1, characterized in that, The base plane (2) is elliptical in shape.
3. The centrifugal pump according to claim 1 or 2, characterized in that, In the space (6) formed between the trailing edge of the impeller (3) and the housing wall (14), the cross-section of the space (6) is configured to continuously increase in the flow direction between the leading edge (7) and the pressure pipe opening (8) in a region up to 270°.
4. The centrifugal pump according to any one of claims 1 to 3, characterized in that, The fluid flowing through the centrifugal pump has a swirling flow, wherein the swirling flow is configured to be as constant as possible in the flow direction between the leading edge (7) and the pressure pipe opening (8).
5. The centrifugal pump according to any one of claims 1 to 4, characterized in that, The long axis (4) is oriented in such a way that it is rotated by an angle α relative to the horizontal line (9).
6. The centrifugal pump according to any one of claims 1 to 5, characterized in that, The pressure pipe opening (8) extends from the leading edge (7) across a complete quadrant of the housing wall (14).
7. The centrifugal pump according to any one of claims 1 to 6, characterized in that, The rotation axis (10) of the impeller (3) is arranged in an eccentric region having a value e of 0.05 to 0.40 in the radial direction.
8. The centrifugal pump according to any one of claims 1 to 7, characterized in that, Between the impeller (3) and the housing (1), a gap ring (13) is eccentrically arranged at the housing (1).
9. The centrifugal pump according to any one of claims 1 to 8, characterized in that, The suction pipe opening (11) is arranged concentrically with the rotation axis (10) of the impeller (3) at the housing (1).
10. Use of a centrifugal pump according to any one of claims 1 to 9 for achieving high energy efficiency in fluid transport, the centrifugal pump having a housing (1) in the form of a plate structure, an eccentrically arranged impeller (3) and a housing (1) having an elliptical base surface (2).