Semi-open impeller for controlling clearance leakage in centrifugal pumps

Abstract

To provide a semi-open type impeller for controlling the clearance leakage of a centrifugal pump.SOLUTION: In a semi-open type impeller for controlling the clearance leakage of a centrifugal pump including a rear cover plate (1), a blade (2), a surface texture (4), a recessed groove part (5), an inlet pipe (9), a pressure face and a suction face, a blade tip of the blade includes the recessed groove part (5), a first blade tip and a second blade tip, the first blade tip and the second blade tip are located at both sides of the recessed groove part, the surface texture (4) being a biomimetic microstructure is formed at the first blade tip and / or the second blade tip, the biomimetic microstructure includes crescent-shaped micro-protrusion textures, and a plurality of the crescent-shaped micro-protrusion textures are regularly arranged on a surface of the blade tip of the blade in a rectangular array.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the technical field of centrifugal pumps, and particularly to a semi-open impeller for controlling the clearance leakage of centrifugal pumps. Specifically, it relates to a semi-open impeller that uses surface texture and concave groove portions to control the tip clearance leakage of centrifugal pumps.

Background Art

[0002] Semi-open impeller centrifugal pumps are widely used in fields such as national defense, aerospace, and civil applications because they have the advantages of easy maintenance, long operating time, and high efficiency. The impeller blades of a centrifugal pump directly determine the performance of the pump and play an important role in the energy conversion of the centrifugal pump. Therefore, the design of centrifugal pump impellers is particularly important.

[0003] Due to the existence of the tip clearance (tip clearance) of the semi-open impeller centrifugal pump, under the action of the pressure gradients on the pressure surface and suction surface of the impeller, complex flows such as leakage flow and leakage vortex cavitation near the tip clearance of the impeller are formed, and the internal flow state of the centrifugal pump impeller changes significantly. The leakage flow at the tip of the impeller near the tip region accelerates the formation of reverse flow, further flows upstream of the impeller, a large number of cavitation bubbles appear near the center of the recirculation vortex in the inlet pipe, low-frequency pressure pulsations occur, and it affects the performance, service life, and operating stability of the pump.

[0004] Therefore, researchers have conducted extensive studies to suppress the phenomena of leakage flow and leakage return at the blade tip gap, and have rudimentary proposals for concepts and methods that have a certain positive effect. Regarding leakage flow and losses in centrifugal pumps, under design conditions, the decrease in efficiency is almost linear with the change in the blade tip gap, so it is common to control it by adjusting the gap between the top of the blade and the pump body. However, the gap at the blade tip is not infinitely small, and an appropriately small gap results in higher efficiency than when there is no gap. To reduce the impact of backflow on the operating stability of the impeller, proposed groove technologies such as J-shaped grooves and U-shaped grooves have been widely applied, but these are applicable to mixed-flow pumps and axial-flow pumps, and not to centrifugal pump structures.

[0005] Surface textures are currently being widely studied, primarily to improve the tribological properties of surfaces. Machining the surface of friction pairs with specific, regular shapes such as micro-grooves or micro-protrusions has proven to be an effective means of improving tribological properties and has potential applications in increasing friction between the impeller and fluid in centrifugal pumps. Therefore, to address the above challenges, we provide a semi-open type impeller that uses surface structure and grooves to control gap leakage at the blade tip of a centrifugal pump. [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to provide a semi-open impeller that controls gap leakage at the blade tip of a centrifugal pump using surface texture and grooves to overcome the shortcomings of the prior art. The semi-open impeller structure is characterized by reducing gap leakage and improving or eliminating backflow by increasing friction between the leak flow and the uppermost part of the impeller. The groove structure on the surface of the blade tip of the present invention (first arc-shaped part (arc part), second arc-shaped part (arc part), flow guide passage, arc-shaped groove) further changes the local flow structure and the direction of the leak flow, preventing the liquid flow from directly flowing into the next flow path, thereby reducing the impact on the blade due to fluid flow. The circumferential groove structure provided on the outside of the impeller inlet pipe provides a passage for the leak flow to move at high speed in the axial direction, reducing the absolute flow angle near the rear cover plate, suppressing the tendency for backflow to flow upward, and improving the flow condition at the inlet of the centrifugal pump. [Means for solving the problem]

[0007] To achieve the above objectives, the technical solutions used in this invention are as follows. Located between the pump case (6) and the pump cover (7), the rear cover plate (1), impeller (2), surface texture (4), groove (5), inlet pipe (9), pressure surface (21), and suction surface (22) are located. The rear cover plate is disc-shaped, and the multiple impellers are uniformly distributed on the rear cover plate along the circumferential direction. The impellers are straight and extend radially. The inlet pipe is located radially inside the multiple impellers, the radial inner ends of the impellers extend close to the outer circumference of the inlet pipe, and the outer ends of the impellers extend to the outer edge of the rear cover plate. There is an impeller tip gap (8) between the impeller tip and the pump case, and the impellers are facing each other. A semi-open impeller for controlling gap leakage of a centrifugal pump, including a pressure surface and a suction surface, wherein the blade tip of the blade includes a groove (5), a first blade tip (23), and a second blade tip (24), the first blade tip and the second blade tip are located on opposite sides of the groove, the first blade tip and / or the second blade tip have a surface texture (4) which is a biomimetic microstructure, the biomimetic microstructure includes crescent-shaped micro-protrusion textures, and a plurality of crescent-shaped micro-protrusion textures are regularly arranged in a rectangular array on the surface of the blade tip, characterized in that the semi-open impeller for controlling gap leakage of a centrifugal pump.

[0008] Furthermore, the crescent-shaped tip projection of the surface texture (4) faces the suction surface.

[0009] Furthermore, the groove portion (5) includes a first arc-shaped portion (25) and a second arc-shaped portion (26), the first and second arc-shaped portions being arranged symmetrically around the center and tangent at the connection point, the first arc-shaped portion being convex upward and closer to the pressure surface side, and the second arc-shaped portion being concave downward and closer to the suction surface side.

[0010] Furthermore, a flow guide passage (27) is provided inside or below the first arc-shaped portion (25), and the flow guide passage communicates with both the left and right ends of the first arc-shaped portion. The flow guide passage is an arc-shaped passage, and the flow guide passage (27) guides the vortex flow at the right end of the first arc-shaped portion to flow to the left end, that is, to flow from the pressure side to the suction side of the flow guide passage, thereby merging with the recirculation of the second arc-shaped portion, and merging with the recirculation according to the flow state of the recirculation.

[0011] Furthermore, arc-shaped grooves (28) are provided on the surface of the second arc-shaped portion (26), and each arc-shaped groove extends to both the left and right ends of the second arc-shaped portion. The arc-shaped grooves are provided corresponding to flow guide passages, and in the radial direction of the blade (2), multiple flow guide passages (27) and arc-shaped grooves (28) are arranged in an array along the radial direction.

[0012] Furthermore, a plurality of circumferential grooves (3) are provided on the outside of the inlet pipe (9), the circumferential grooves and the inlet pipe are concentric circles, and the plane on which the circle is located is parallel to the plane on which the rear cover plate (1) is located.

[0013] Furthermore, the axial height of the blade (2) or impeller decreases as the distance from the impeller inlet increases.

[0014] Furthermore, the blade (2) is of unequal thickness, with the thickness of the blade decreasing from the radial inner end to the radial outer end.

[0015] Furthermore, in order to process the surface texture (4), an alloy material or ultra-high molecular weight polyethylene is selected as the material, and the surface texture is processed using laser technology. [Effects of the Invention]

[0016] The beneficial technical effects of the present invention are as follows:

[0017] (1) The biomimetic microtexture on the surface of the impeller tip of the present invention reduces leakage in the gap between the impeller tip and the pump case and the centrifugal impeller by increasing the friction between the leak flow and the surface of the impeller tip and creating resistance to the leak flow. The surface texture is a textured friction surface that has a friction-increasing effect, improving the coefficient of friction and reducing the wear rate, thereby extending the service life of the centrifugal impeller. Since the leak flow flows through the "surface texture arc groove (groove portion) - surface texture", a triple barrier to the leak flow is obtained, which effectively suppresses the leak flow.

[0018] (2) The groove structure on the blade tip surface of the present invention (first arc-shaped portion (arc portion), second arc-shaped portion (arc portion), flow guide passage, arc-shaped groove) further alters the local flow structure and the direction of leakage flow, preventing the liquid flow from flowing directly into the next flow path and reducing the impact on the blade due to fluid flow. The jet in the blade tip gap flows through the gap passage, and the jet strength in the gap passage is equal to or slightly greater than the strength of the normal leakage flow, which can block / suppress the normal leakage flow to some extent.

[0019] (3) Furthermore, the circumferential groove structure provided on the outside of the impeller inlet pipe provides a passage for leakage flow to move at high speed in the axial direction, reducing the absolute flow angle near the rear cover plate, suppressing the tendency for backflow to flow upward, and improving the flow conditions at the inlet of the centrifugal pump. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a three-dimensional structural diagram of an impeller according to an embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of the projected structure of the axial surface of an impeller according to an embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram of the enlarged structure of the crescent-shaped surface texture (biomimetical microstructure) of the present invention. [Figure 4] Figure 4 is a schematic diagram of the structure in which a vortex is generated in the groove portion of the impeller blade tip according to an embodiment of the present invention. [Figure 5] FIG. 5 is a schematic diagram of a structure in which a vortex occurs in a concave groove portion at the tip of an impeller blade according to another embodiment of the present invention. [Figure 6] FIG. 6 is a streamline diagram of a vortex flow in a general impeller of the prior art. [Figure 7] FIG. 7 is a streamline diagram of a vortex flow in an impeller according to an embodiment of the present invention. [Figure 8] FIG. 8 is a curve comparison diagram of the performance of the impeller of the present invention.

Description of Reference Numerals

[0021] In the figure, rear cover plate 1 (blade plate), blade 2, circumferential groove 3, surface texture 4 (biomimetic microstructure), concave groove portion 5, front pump case 6, rear pump cover 7, blade tip clearance 8, inlet pipe 9, pressure surface 21, suction surface 22, first blade tip 23, second blade tip 24, first arc-shaped portion 25 (arc portion), second arc-shaped portion 26 (arc portion), flow guiding passage 27, arc-shaped concave groove 28.

Embodiments for Carrying Out the Invention

[0022] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, hereinafter, in conjunction with the drawings of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described. It is clear that the described embodiments are some, rather than all, of the embodiments of the present invention. According to the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present invention.

[0023] Hereinafter, the present invention will be described in more detail with reference to the drawings.

[0024] As shown in Figures 1-4, the rear cover plate 1 is located between the pump case 6 and the pump cover 7 and includes the rear cover plate 1, blades 2, surface texture / biomimetic microstructure 4, groove 5, inlet pipe 9, pressure surface 21, and suction surface 22. The rear cover plate 1 is disc-shaped, and the multiple blades 2 are uniformly distributed on the rear cover plate 1 along the circumferential direction. The blades 2 are straight blades that extend radially, and the inlet pipe 9 is located radially inside the multiple blades 2. The radial inner ends of the blades 2 extend close to the outer circumference of the inlet pipe 9, and the outer ends of the blades 2 extend to the outer edge of the rear cover plate 1. A semi-open impeller for controlling gap leakage of a centrifugal pump, wherein there is a blade tip gap 8 between the blades, and the blade 2 includes opposing pressure surfaces 21 and suction surfaces 22, the blade tip of the blade 2 includes a groove 5, a first blade tip 23, and a second blade tip 24, the first blade tip 23 and the second blade tip 24 are located on both sides of the groove 5, the first blade tip 23 and / or the second blade tip 24 have a surface texture 4 which is a biomimetic microstructure, the biomimetic microstructure includes crescent-shaped micro-protrusion textures, and a plurality of crescent-shaped micro-protrusion textures are regularly arranged in a rectangular array on the surface of the blade tip.

[0025] As shown in Figure 3, the surface texture 4 of the impeller blade tip utilizes bioengineering principles, and biomimetic microtextures that can increase friction are designed and arranged on the surface of the blade tip. The biomimetic microtextures are mainly based on the crescent-shaped hooks of burdock, and the crescent-shaped tip protrusions face the suction surface, and the structure has been optimized to be advantageous in increasing the coefficient of friction. The biomimetic microtextures on the surface are arranged in the form of microprotrusion textures, and the microprotrusion textures are regularly arranged in a rectangular array on the surface of the blade tip.

[0026] Using laser technology, a texture treatment is performed, and processing steps such as processing a template with a laser, transferring a pattern sample, and processing the substrate are carried out in sequence to process a crescent-shaped surface texture (crescent-shaped micro-protrusion structure) with rational external shape and size parameters onto the surface of the impeller blades. Specifically, in order to manufacture the semi-open type impeller of the centrifugal pump of the present invention in which the circumferential grooves 3 and the blade blade structure are arranged, first a model change processing is performed on the inlet pipe 9, then the blades of the present invention are designed according to the blades of a conventional centrifugal pump, then the blade blade structure is model changed, and the biomimetic microstructure on the surface of the blade tip is processed.

[0027] Specifically, the blade 2 of the embodiment is a blade of unequal thickness. The inlet diameter D1 of the blade provided in the embodiment is 25 mm, and the outlet diameter D2 is 130 mm. The width of the blade of the embodiment is 9 mm, and the chord length of the arc of the recessed groove portion 5 at the tip of the blade is 2.5 mm, with the two arcs having the same angle and being symmetrically arranged. A circumferential groove 3 with a projection height of 2 mm and a width of 2 mm is provided on the outside of the inlet tube 9 of the embodiment, and there are three circumferential grooves 3, with a distance of 3 mm between two circumferential grooves.

[0028] As shown in Figure 4, the groove portion 5 includes a first arc-shaped portion 25 (arc portion) and a second arc-shaped portion 26 (arc portion). The first arc-shaped portion 25 and the second arc-shaped portion 26 are arranged symmetrically around the center and are tangent at the connection point. The first arc-shaped portion 25 is convex upward and closer to the pressure surface 21 side, while the second arc-shaped portion 26 is concave downward and closer to the suction surface 22 side.

[0029] As shown in Figure 4, the leak flow that passes through despite being blocked by the surface texture 4 flows along the pressure surface 21 and the first arc-shaped portion 25, and due to their buffering effect, flows to the blade wall of the suction surface 22 and recirculates, forming a vortex structure in the downwardly recessed arc-shaped portion / second arc-shaped portion 26, and changing the local flow structure of the blade and the direction of the leak flow, thereby reducing the impact on the blade due to fluid flow by preventing the liquid flow from flowing directly into the next blade passage. The jet in the blade tip gap flows within the gap passage, and the jet strength within the gap passage is equal to or slightly greater than the strength of the normal leak flow, so that the flow of the normal leak flow can be blocked / suppressed to some extent.

[0030] Regarding the biomimetic microtextures on the blade tip surface, macroscopically, protruding textures increase the coefficient of friction between the leak flow and the blade tip surface, creating resistance to the leak flow. Microscopically, crescent-shaped protrusions can block the leak flow on the blade tip surface and generate tiny vortices in the concave surface of the crescent.

[0031] The grooves 5 on the surface of the blade tip of blade 2 rotate along the pump shaft of the centrifugal pump, and the leaky liquid flows along the pressure surface 21 and the arc section, and due to their buffering effect, flows to the blade wall of the suction surface 22 and recirculates, forming a vortex structure at the second arc section 26, and changing the local flow structure of the blade and the direction of the leaky flow, so that the liquid flow does not flow directly into the next blade passage, and reducing the impact on the blade due to the fluid flow.

[0032] As shown in Figure 5, in another embodiment, a flow guide passage 27 is provided inside / below the first arc-shaped portion 25, and the flow guide passage 27 communicates with both the left and right ends of the first arc-shaped portion 25, and the flow guide passage 27 is an arc-shaped passage, and the flow guide passage 27 guides the vortex flow at the right end of the first arc-shaped portion 25 to flow to the left end, that is, to flow from the pressure surface 21 side of the flow guide passage 27 to the flow path on the suction surface 22 side, thereby merging with the recirculation in the second arc-shaped portion 26 and merging with the recirculation according to the flow state of the recirculation. Arc-shaped grooves 28 are provided on the surface of the second arc-shaped portion 26, and each arc-shaped groove 28 extends to both the left and right ends of the second arc-shaped portion 26. The arc-shaped grooves 28 are provided in correspondence with the flow guide passages 27, and in the radial direction of the blade 2, multiple flow guide passages 27 and arc-shaped grooves 28 are arranged in an array radially.

[0033] The design of the flow guide passage 27 and the arc-shaped groove 28 further alters the local flow structure and direction of leakage flow on the blade, preventing the liquid flow from directly flowing into the next blade passage and reducing the impact on the blade due to fluid flow. The jet in the blade tip gap flows through the gap passage, and the jet strength in the gap passage is equal to or slightly greater than the strength of the normal leakage flow, thus blocking / suppressing the normal leakage flow motion to some extent.

[0034] Multiple circumferential grooves 3 are provided on the outside of the inlet pipe 9, and the circumferential grooves 3 and the inlet pipe 9 are concentric circles, with the plane on which the circle is located being parallel to the plane on which the rear cover plate 1 is located. The number of circumferential grooves 3 is rationally selected according to the length of the inlet pipe, and the diameter of the projections of the circumferential grooves 3 is 2 to 5 mm larger than the diameter of the inlet pipe 9.

[0035] To process the surface texture 4, an alloy material may be selected, or ultra-high molecular weight polyethylene (UHMWPE) may be used. This material possesses excellent characteristics such as strong wear resistance and strong impact resistance.

[0036] The axial height of blade 2 / impeller decreases as the distance from the impeller inlet increases. Blade 2 is of unequal thickness; specifically, the thickness of blade 2 decreases from the radial inner end to the radial outer end.

[0037] Figures 6 and 7 show the flow conditions of the impeller before and after modification, respectively. In the unmodified impeller, large vortices were observed near each flow path outlet under the designed operating conditions. This is because not only changes in pressure and velocity, but also leakage from the blade tip gap affects the internal flow path, forming large vortices. In particular, the flow path near the volute partition tongue has a small outlet region, causing the vortices to concentrate in the center of the impeller flow path, resulting in stronger vortex intensity at the vortex center. These large vortices have a serious impact on the performance of the centrifugal pump. As can be seen from the flow conditions of the internal flow path of the modified impeller in Figure 7, the vortices are significantly reduced, and the internal flow path near the partition tongue is particularly improved. The large vortices become smaller and move towards the impeller outlet. This is mainly because the flow conditions of the internal flow path of the impeller are improved by reducing leakage from the blade tips. Furthermore, the circumferential groove structure provided on the outside of the impeller inlet pipe gives the leak flow a passage that moves at high speed in the axial direction, reducing the absolute flow angle near the rear cover plate, suppressing the tendency for backflow to flow upward, and improving the flow conditions at the centrifugal pump inlet.

[0038] Figure 8 shows a comparison of the head-flow curves of the impeller in this embodiment and a general impeller, demonstrating improved performance at the test operation conditions. The impeller in this embodiment has a certain suppressive effect against backflow vortices and improves leakage flow in the impeller gap.

[0039] The beneficial technical effects of the present invention are as follows:

[0040] (1) The biomimetic microtexture on the surface of the impeller tip of the present invention reduces leakage in the gap between the impeller tip and the pump case and the centrifugal impeller by increasing the friction between the leak flow and the surface of the impeller tip and creating resistance to the leak flow. The surface texture is a textured friction surface that has a friction-increasing effect, improving the coefficient of friction and reducing the wear rate, thereby extending the service life of the centrifugal impeller. Since the leak flow flows through the "surface texture arc groove (groove portion) - surface texture", a triple barrier to the leak flow is obtained, which effectively suppresses the leak flow.

[0041] (2) The groove structure on the blade tip surface of the present invention (first arc-shaped portion (arc portion), second arc-shaped portion (arc portion), flow guide passage, arc-shaped groove) further alters the local flow structure and the direction of leakage flow, preventing the liquid flow from flowing directly into the next flow path and reducing the impact on the blade due to fluid flow. The jet in the blade tip gap flows through the gap passage, and the jet strength in the gap passage is equal to or slightly greater than the strength of the normal leakage flow, which can block / suppress the normal leakage flow to some extent.

[0042] (3) Furthermore, the circumferential groove structure provided on the outside of the impeller inlet pipe provides a passage for leakage flow to move at high speed in the axial direction, reducing the absolute flow angle near the rear cover plate, suppressing the tendency for backflow to flow upward, and improving the flow conditions at the inlet of the centrifugal pump.

[0043] The embodiments described above are for illustrative purposes only and not limitations on the present invention. Various modifications, alterations, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of protection of the present invention is limited by the appended claims and their equivalents.

Claims

1. Located between the pump case (6) and the pump cover (7), The invention comprises a rear cover plate (1), vanes (2), a surface texture (4), a groove (5), an inlet pipe (9), a pressure surface (21), and a suction surface (22), The rear cover plate is disk-shaped, and the plurality of blades are uniformly distributed on the rear cover plate along a circumferential direction; The blades are straight blades extending in a radial direction, and the inlet pipe is located radially inside the plurality of blades; a radially inner end of the vane extends to near an outer periphery of the inlet pipe, and an outer end of the vane extends to an outer edge of the rear cover plate; There is a blade tip gap (8) between the blade tip and the pump case, The vane is a semi-open impeller for controlling clearance leakage in a centrifugal pump, the semi-open impeller including opposing pressure and suction surfaces, The blade tip includes a groove portion (5), a first blade tip (23), and a second blade tip (24); The first blade tip and the second blade tip are located on both sides of the groove portion, respectively. the first blade tip and / or the second blade tip have a surface texture (4) that is a biomimetic microstructure; The biomimetic microstructure comprises a crescent-shaped microprojection texture; The plurality of crescent-shaped micro-projection textures are regularly arranged in a rectangular array on the surface of the blade tip. A semi-open impeller for controlling clearance leakage in a centrifugal pump, characterized by:

2. 2. The semi-open impeller for controlling clearance leakage in a centrifugal pump according to claim 1, wherein the crescent-shaped tip projection of the surface texture (4) faces the suction surface.

3. 3. The semi-open impeller for controlling clearance leakage in a centrifugal pump according to claim 2, wherein the groove portion (5) includes a first arc-shaped portion (25) and a second arc-shaped portion (26), the first arc-shaped portion and the second arc-shaped portion being arranged symmetrically about the center and tangent to each other at a connecting point, the first arc-shaped portion being convex upward and close to the pressure surface side, and the second arc-shaped portion being concave downward and close to the suction surface side.

4. 4. The semi-open impeller for controlling clearance leakage in a centrifugal pump according to claim 3, wherein a flow guide passage (27) is provided inside or below the inside of the first arc-shaped portion (25), the flow guide passages respectively communicating with both left and right ends of the first arc-shaped portion, the flow guide passages being arc-shaped passages, and the flow guide passages are used to guide the vortex flow at the right end of the first arc-shaped portion to flow to the left end.

5. 5. The semi-open impeller for controlling clearance leakage in a centrifugal pump according to claim 4, wherein arc-shaped grooves (28) are provided on the surface of the second arc-shaped portion (26), and the arc-shaped grooves extend to both left and right ends of the second arc-shaped portion, respectively, and the arc-shaped grooves are provided corresponding to the flow guide passages, and a plurality of flow guide passages (27) are provided in the radial direction of the blade (2), and the arc-shaped grooves (28) are provided in an array along the radial direction.

6. 6. The semi-open impeller for controlling clearance leakage in a centrifugal pump according to claim 5, wherein a plurality of circumferential grooves (3) are provided on the outside of the inlet pipe (9), the circumferential grooves and the inlet pipe are concentric circles, and the plane on which the circles lie is parallel to the plane on which the rear cover plate (1) is located.

7. 7. A semi-open impeller for controlling clearance leakage in a centrifugal pump according to claim 6, characterized in that the axial height of the vanes (2) or impeller decreases as the distance from the impeller inlet increases.

8. 8. The semi-open impeller for controlling clearance leakage in a centrifugal pump according to claim 7, wherein the blades (2) are blades of unequal thickness, and the thickness of the blades becomes thinner from the radially inner end to the radially outer end.

9. 9. The semi-open impeller for controlling clearance leakage in a centrifugal pump according to claim 8, characterized in that the material for processing the surface texture (4) is selected to be an alloy material or ultra-high molecular weight polyethylene, and the surface texture is processed by using laser technology.

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