CN113309734B - Semi-open impeller for controlling clearance leakage of centrifugal pump - Google Patents

Abstract

The invention discloses a semi-open impeller for controlling the clearance leakage of a centrifugal pump, which is positioned between a pump shell and a pump cover and comprises a rear cover plate (1), blades (2), surface textures (4), groove parts (5), an inlet pipe (9), a pressure surface (21) and a suction surface (22), and is characterized in that: the blade top of blade includes concave part (5), first blade top (23), second blade top (24), and first blade top, second blade top are located the both sides of concave part respectively, and first blade top and/or second blade top have surface texture (4), and surface texture is bionical microstructure, and bionical microstructure includes the little protruding texture of crescent, and the arrangement in blade top surface of the little protruding texture of a plurality of crescent according to the rectangle array rule. The impeller structure has the characteristics of increasing the friction between leakage flow and the top of the impeller so as to reduce clearance leakage and improve or even eliminate reverse flow.

Description

A semi-open impeller for controlling clearance leakage of centrifugal pumps

technical field

The invention relates to the technical field of centrifugal pumps, in particular to a semi-open impeller used for controlling clearance leakage of centrifugal pumps, in particular to a semi-open impeller using surface texture and grooves to control the leakage of centrifugal pump tip clearances.

Background technique

The semi-open impeller centrifugal pump has been widely used in national defense, aerospace, civil and other fields due to its advantages of convenient maintenance, long running time and high efficiency. The blades of the impeller directly determine the performance of the centrifugal pump and play a vital role in the energy conversion process of the centrifugal pump, so the design of the centrifugal pump blades is particularly important.

Due to the existence of the blade tip clearance (tip clearance) in the semi-open impeller centrifugal pump, under the action of the pressure gradient between the blade pressure surface and the suction surface, complex flows such as tip leakage flow and leakage vortex cavitation are formed near the blade tip clearance. , will significantly change the flow regime inside the centrifugal pump impeller. The tip leakage flow near the blade tip area accelerates the formation of countercurrent, and then develops to the upstream of the impeller. A large number of cavitation bubbles appear near the center of the return vortex in the inlet pipe, resulting in low-frequency pressure pulsation, which affects the performance, service life and operation stability of the pump. .

To this end, researchers have carried out a lot of research to control the phenomenon of leakage flow and leakage backflow in the tip clearance, and initially put forward some ideas and methods with certain positive effects. For the leakage flow and loss of centrifugal pumps, under the design conditions, the reduction of efficiency is almost linear with the change of the blade tip clearance, so it is generally controlled by adjusting the clearance between the top of the blade and the pump body, but the blade tip clearance cannot be infinitely small. Small voids are more efficient than no voids. In order to reduce the influence of countercurrent on the stability of impeller operation, the groove technology proposed by people has been widely used, such as J-shaped groove and U-shaped groove, but it is suitable for mixed flow pumps and axial flow pumps, not for centrifugal pumps. structure.

Surface texture has been widely studied and is mainly used to improve surface tribological properties. It can process some regular shapes such as micro-grooves or micro-convex bodies with certain morphology on the surface of the friction pair, and it has been proved to improve the tribological properties. It is an effective means of performance, and its application in centrifugal pump impeller increase and fluid friction has development prospects. Therefore, in view of the above-mentioned problems, a semi-open impeller is proposed, which uses a surface structure and a groove portion to control the leakage of the tip clearance of a centrifugal pump.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a semi-open impeller that uses surface texture and grooves to control the leakage of the tip clearance of a centrifugal pump. The semi-open impeller structure has the advantages of increasing the leakage flow. The friction with the top of the impeller can reduce the leakage of the gap and improve or even eliminate the characteristics of reverse flow; , drainage channel, arc-shaped groove) can change the local flow structure and leakage flow direction, and prevent the liquid flow from directly rushing to the next flow channel, thereby reducing the impact of the fluid flow on the blades; The circumferential groove structure provides a channel for leakage flow to move rapidly along the axial direction. The absolute flow angle close to the rear cover plate is reduced, and the trend of reverse flow upstream is suppressed, which can improve the flow pattern at the inlet of the centrifugal pump.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A semi-open impeller for controlling clearance leakage of a centrifugal pump, the semi-open impeller is located between a pump casing (6) and a pump cover (7), and comprises a rear cover plate (1), blades (2), a surface weave structure (4), groove part (5), inlet pipe (9), pressure surface (21), suction surface (22), the rear cover plate is in the shape of a disc, and a plurality of blades are evenly distributed on the rear cover plate along the circumferential direction The blades are arranged radially extending and the blades are straight blades, the inlet pipe is located on the radial inner side of the plurality of blades, the radial inner end of the blades extends to the vicinity of the outer circumference of the inlet pipe, and the outer end of the blades extends to the outer edge of the rear cover plate. There is a blade tip gap (8) between the blade tip and the pump casing, the blade includes opposite pressure surfaces and suction surfaces, and is characterized in that: the blade tip of the blade includes a groove portion (5), a first blade tip (23), a first blade tip (23), a second blade tip Two blade tips (24), the first blade tip and the second blade tip are respectively located on both sides of the groove portion, the first blade tip and/or the second blade tip have a surface texture (4), and the surface texture is bionic micro The bionic microstructure includes a crescent-shaped micro-convex texture, and a plurality of crescent-shaped micro-convex textures are regularly arranged on the blade tip surface in a rectangular array.

Further, the crescent-shaped cusp protrusion of the surface texture (4) faces the suction surface.

Further, the groove part (5) comprises a first arc-shaped part (25) and a second arc-shaped part (26), the first arc-shaped part and the second arc-shaped part are arranged symmetrically in the center, and at the connection point Tangent, the first arc-shaped portion is arranged upwardly convex and close to the side of the pressure surface, and the second arc-shaped portion is arranged concavely downwards and is arranged close to the side of the suction surface.

Further, a drainage channel (27) is provided in or below the first arc-shaped portion (25), the drainage channel is respectively connected to the left and right ends of the first arc-shaped portion, and the drainage channel is an arc-shaped channel, and the drainage channel ( 27) It is used to guide the vortex at the right end of the first arc to flow to the left, that is, from the pressure surface of the drainage channel to the flow channel of the suction surface, so as to merge with the return flow at the second arc and follow the flow of the return flow. state and return flow.

Further, the surface of the second arc-shaped portion (26) is provided with arc-shaped grooves (28), the arc-shaped grooves respectively extend to the left and right ends of the second arc-shaped portion, and the position of the arc-shaped grooves is related to the drainage. The channels are correspondingly arranged; in the radial direction of the blade (2), a plurality of drainage channels (27) and arc grooves (28) are arranged in an array along the radial direction.

Further, 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 of the circle is parallel to the plane of the rear cover plate (1).

Further, the axial height of the blade (2) or the impeller decreases as the distance from the inlet of the impeller increases.

Further, the blade (2) is a blade of unequal thickness, and the thickness of the blade gradually decreases from the radially inner end to the radially outer end.

Further, in order to process the surface texture (4), the material of which is selected from alloy materials, or ultra-high molecular weight polyethylene; the surface texture is textured by using laser technology.

The beneficial technical effect of the present invention is:

(1) The bionic micro-texture of the blade tip surface of the present invention, the convex texture mainly produces resistance to the leakage flow by increasing the friction between the leakage flow and the blade tip surface, thereby reducing the friction between the centrifugal pump casing and the centrifugal impeller. Tip clearance leaks. The surface texture is a textured friction surface with a friction-increasing effect, which can reduce the wear rate while increasing the friction coefficient, and improve the service life of the centrifugal impeller; The process of "grooving part) - surface texture", triple obstruction to leakage flow, can produce a good effect of inhibiting leakage flow.

(2) The structure of the groove portion of the blade tip surface (the first arc portion (arc portion), the second arc portion (arc portion), the drainage channel, the arc groove) in the present invention can change the local flow structure And the leakage flow direction, do not let the liquid flow directly to the next flow channel, thereby reducing the impact of the fluid flow on the blade. The jet strength of the tip clearance jet passing through the clearance channel can be equal to or even slightly larger than that of the conventional leakage flow, which can hinder/inhibit the conventional leakage flow to a certain extent.

(3) At the same time, the circumferential groove structure set on the outside of the impeller inlet pipe provides a channel for the leakage flow to move rapidly in the axial direction, the absolute flow angle close to the rear cover plate is reduced, and the upstream trend of reverse flow is suppressed. The flow regime at the inlet of the centrifugal pump can be improved.

Description of drawings

1 is a three-dimensional structural diagram of an impeller in an embodiment of the present invention;

2 is a schematic diagram of a projection structure of an impeller axial plane in an embodiment of the present invention;

3 is an enlarged schematic view of the crescent-shaped surface texture (biomimetic microstructure) of the present invention;

4 is a schematic structural diagram of a vortex generated in a groove portion of an impeller blade tip according to an embodiment of the present invention;

5 is a schematic structural diagram of a vortex generated in a groove portion of an impeller blade tip according to another embodiment of the present invention;

6 is a streamline diagram of a vortex flow in a general impeller in the prior art;

7 is a streamline diagram of a vortex flow in an impeller according to an embodiment of the present invention;

FIG. 8 is a comparison diagram of the performance curves of the impeller of the present invention.

In the figure: rear cover plate 1 (blade plate), blade 2, circumferential groove 3, surface texture 4 (biomimetic microstructure), groove part 5, front pump casing 6, rear pump cover 7, blade tip clearance 8, Inlet pipe 9, pressure surface 21, suction surface 22, first tip 23, second tip 24, first arc part 25 (arc part), second arc part 26 (arc part), drainage channel 27. Arc groove 28.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figures 1-4, a semi-open impeller for controlling clearance leakage of a centrifugal pump, the semi-open impeller is located between the pump casing 6 and the pump cover 7, which includes a rear cover plate 1, blades 2, a surface weave Structure / bionic microstructure 4, groove part 5, inlet pipe 9, pressure surface 21, suction surface 22, the rear cover plate 1 is in the shape of a disc, and a plurality of blades 2 are evenly distributed on the rear cover plate 1 in the circumferential direction. 2. Extending along the radial direction and the blade 2 is a straight blade, the inlet pipe 9 is located on the radial inner side of the plurality of blades 2, the radial inner end of the blade 2 extends to the vicinity of the outer circumference of the inlet pipe 9, and the outer end of the blade 2 extends to the rear cover plate 1. At the outer edge, there is a tip gap 8 between the tip of the blade 2 and the pump casing 6. The blade 2 includes a pressure surface 21 and a suction surface 22 opposite to each other. It is characterized in that: the tip of the blade 2 includes a groove portion 5, a first The blade tip 23 and the second blade tip 24, the first blade tip 23 and the second blade tip 24 are respectively located on both sides of the groove portion 5, and the first blade tip 23 and/or the second blade tip 24 have a surface texture 4, The surface texture 4 is a bionic microstructure, and the bionic microstructure includes a crescent-shaped micro-convex texture, and a plurality of crescent-shaped micro-convex textures are regularly arranged on the blade tip surface in a rectangular array.

As shown in FIG. 3 , the surface texture 4 of the impeller tip adopts the principle of bionics, and the surface of the tip is designed and arranged with a bionic microtexture capable of increasing friction. The bionic microtexture 4 mainly refers to the crescent hook angle of Xanthium serrata, and the crescent cusp bulges facing the suction surface, and the structure is optimized to increase the friction coefficient. The bionic surface texture 4 is arranged in the form of micro-convex texture, and the micro-convex texture is regularly arranged on the blade tip surface in a rectangular array.

Laser technology is used for texturing treatment. Using laser, through processing steps such as processing template, transferring pattern samples, processing substrate, etc., a crescent-shaped surface texture with reasonable shape and size parameters is processed on the blade tip surface of the impeller ( crescent-shaped microprotrusions). Specifically, to manufacture the semi-open impeller of the centrifugal pump with the circumferential groove 3 and the vane tip structure of the present invention, the inlet pipe 9 is modified and processed, and then the vane of the present invention is designed according to the traditional centrifugal pump vane design. , and then modify the tip structure of the blade to process the bionic microstructure of the tip surface.

Specifically, the blade 2 in the embodiment is an unequal thickness blade. The blade inlet diameter D1 provided in the embodiment is 25mm, and the outlet diameter D2 is 130mm; in the embodiment, the width of the blade is 9mm, and the arc chord length of the blade tip groove portion 5 is 2.5mm, and the two arcs are the same and symmetrically arranged. ; The outer side of the inlet pipe 9 in the embodiment is provided with a circumferential groove 3, its raised height is 2mm, the width is 2mm, the number of circumferential grooves 3 is arranged 3, and the distance between the two grooves is 3mm.

As shown in FIG. 4 , the groove portion 5 includes a first arc-shaped portion 25 (circular arc portion) and a second arc-shaped portion 26 (circular arc portion), and the first arc-shaped portion 25 and the second arc-shaped portion 26 are centrally symmetric The first arc-shaped portion 25 is arranged convexly upwards and is close to the pressure surface 21 side, and the second arc-shaped portion 26 is concavely arranged downwards and is arranged close to the suction surface 22 side.

As shown in FIG. 4 , the leakage flow that is obstructed but still passed by the surface texture 4 flows through the pressure surface 21 and the first arc-shaped portion 25, and flows to the suction surface 22 through its buffering effect. A vortex structure is formed at the second arc-shaped portion 26, and the local flow structure and leakage flow direction of the blade are changed at the same time, so that the liquid flow does not directly rush to the flow channel of the next blade, and the impact of the fluid flow on the blade is reduced. The jet strength of the tip clearance jet passing through the clearance channel can be equal to or even slightly larger than that of the conventional leakage flow, which can hinder/inhibit the conventional leakage flow to a certain extent.

The bionic micro-texture 4 on the blade tip surface, the convex texture on the macro scale increases the friction coefficient between the leakage flow and the blade tip surface, and produces resistance to the leakage flow; The concave surface of the crescent creates tiny vortices.

The groove part 5 of the blade tip surface of the blade 2 rotates with the pump shaft of the centrifugal pump, and the leakage liquid flows through the pressure surface 21 and the arc part, and flows back to the blade wall of the suction surface 22 through its buffering effect. A vortex structure is formed at the arc portion 26, and the local flow structure and leakage flow direction of the blade are changed at the same time, so that the liquid flow does not directly rush to the flow channel of the next blade, and the impact of the fluid flow on the blade is reduced.

As shown in FIG. 5 , in another embodiment, a drainage channel 27 is provided in/under the first arc-shaped portion 25 , and the drainage channel 27 is respectively connected to the left and right ends of the first arc-shaped portion 25 , and the drainage channel 27 is The arc-shaped channel, the drainage channel 27 is used to guide the vortex at the right end of the first arc-shaped portion 25 to flow to the left end, that is, the flow channel from the pressure surface 21 side of the drainage channel 27 to the suction surface 22 side, so as to communicate with the second arc-shaped portion 26 The recirculation at the point where the recirculation converges, following the flow pattern of the recirculation to join the recirculation. The surface of the second arc-shaped portion 26 is provided with arc-shaped grooves 28, and the arc-shaped grooves 28 extend to the left and right ends of the second arc-shaped portion 26 respectively. In the radial direction of the blade 2, a plurality of drainage channels 27 and arc-shaped grooves 28 are arranged in an array in the radial direction.

Through the design of the drainage channel 27 and the arc groove 28, the local flow structure and leakage flow direction of the blade are further changed, so that the liquid flow does not directly rush to the next blade flow channel, which reduces the impact of the fluid flow on the blade; the tip clearance The intensity of the jet passing through the gap channel can be equal to or even slightly larger than that of the conventional leakage flow, which can hinder/inhibit the conventional leakage flow to a certain extent.

A plurality of circumferential grooves 3 are arranged on the outside of the inlet pipe 9 . The circumferential grooves 3 and the inlet pipe 9 are concentric circles, and the plane of the circle is parallel to the plane of the rear cover plate 1 . The number of circumferential grooves 3 is reasonably arranged according to the length of the inlet pipe, and the diameter of the protrusion of the circumferential groove 3 is larger than the diameter of the inlet pipe 9 by 2-5 mm.

In order to process the surface texture 4, an alloy material or an ultra-high molecular weight polyethylene (UHMWPE) can be selected as the material, which has excellent characteristics such as strong wear resistance and strong impact resistance.

The blade 2/impeller axial height decreases with increasing distance from the impeller inlet. The blade 2 is a blade of unequal thickness. Specifically, the thickness of the blade 2 gradually decreases from the radially inner end to the radially outer end.

Figure 6 and Figure 7 show the flow state of the impeller before and after the improvement, respectively. Under the design conditions of the impeller before the improvement, it can be observed that there are large vortices near the outlet of each flow channel, which is not only caused by the pressure and speed changes, but also the leakage of the tip clearance also affects the inner flow channel, causing it to form a large vortex. Especially in the flow channel near the volute separating tongue, the outlet area is small, the vortex is more concentrated in the center of the impeller flow channel, and the eddy current in the center of the vortex is stronger. This large eddy current seriously affects the performance of the centrifugal pump. Figure 7 In the improved flow state of the impeller inner flow channel, it can be seen that the eddy current is significantly reduced, especially the inner flow channel near the separation tongue can see obvious improvement, the large eddy flow becomes smaller and moves to the impeller outlet, which is mainly by reducing The blade tip leaks to improve the flow state of the flow channel in the impeller. At the same time, the circumferential groove structure arranged on the outside of the impeller inlet pipe provides a channel for the leakage flow to move rapidly in the axial direction, the absolute flow angle close to the rear cover plate is reduced, and the trend of reverse flow upstream is suppressed, which can also improve the centrifugal pump. flow regime at the inlet.

Fig. 8 compares the head-flow curve between the impeller of this embodiment and the general impeller, and it can be seen that the performance is improved under the test operating point. The impeller of this embodiment has a certain inhibitory effect on the countercurrent vortex, which improves the leakage flow in the gap of the impeller.

The beneficial technical effect of the present invention is:

(1) The bionic micro-texture of the blade tip surface of the present invention, the convex texture mainly produces resistance to the leakage flow by increasing the friction between the leakage flow and the blade tip surface, thereby reducing the friction between the centrifugal pump casing and the centrifugal impeller. Tip clearance leaks. The surface texture is a textured friction surface with a friction-increasing effect, which can reduce the wear rate while increasing the friction coefficient, and improve the service life of the centrifugal impeller; The process of "grooving part) - surface texture", triple obstruction to leakage flow, can produce a good effect of inhibiting leakage flow.

(2) The structure of the groove portion of the blade tip surface (the first arc portion (arc portion), the second arc portion (arc portion), the drainage channel, the arc groove) in the present invention can change the local flow structure And the leakage flow direction, do not let the liquid flow directly to the next flow channel, thereby reducing the impact of the fluid flow on the blade. The jet strength of the tip clearance jet passing through the clearance channel can be equal to or even slightly larger than that of the conventional leakage flow, which can hinder/inhibit the conventional leakage flow to a certain extent.

(3) At the same time, the circumferential groove structure set on the outside of the impeller inlet pipe provides a channel for the leakage flow to move rapidly in the axial direction, the absolute flow angle close to the rear cover plate is reduced, and the upstream trend of reverse flow is suppressed. The flow regime at the inlet of the centrifugal pump can be improved.

The above-mentioned embodiment is an illustration of the present invention, not a limitation of the present invention. It can be understood that various changes, modifications, replacements and modifications can be made to these embodiments without departing from the principle and spirit of the present invention. The protection scope of the present invention It is defined by the appended claims and their equivalents.

Claims (6)

1. The utility model provides a semi-open impeller for controlling centrifugal pump clearance leaks, semi-open impeller is located between pump case (6) and pump cover (7), it includes back shroud (1), blade (2), surface texture (4), concave part (5), import pipe (9), pressure side (21), suction surface (22), the back shroud is discoid, a plurality of blades are along circumference evenly distributed on the back shroud, the blade is along radially extending to arrange and near the blade is straight blade, import pipe is located near radial inboard and the radial inner of blade of a plurality of blades extends to import pipe periphery, the blade outer end extends to the back shroud outward flange, there is blade top clearance (8) between the blade top of blade and the pump case, the blade includes relative pressure side, the suction surface, its characterized in that: the blade top of the blade comprises a groove part (5), a first blade top (23) and a second blade top (24), the first blade top and the second blade top are respectively positioned at two sides of the groove part, the first blade top and/or the second blade top are/is provided with surface textures (4), the surface textures are bionic microstructures, the bionic microstructures comprise crescent-shaped micro-protrusion textures, and the crescent-shaped micro-protrusion textures are regularly arranged on the surface of the blade top of the blade according to a rectangular array;

The groove part (5) comprises a first arc-shaped part (25) and a second arc-shaped part (26), the first arc-shaped part and the second arc-shaped part are arranged in a centrosymmetric manner and are tangent at the joint of the first arc-shaped part and the second arc-shaped part, the first arc-shaped part is arranged in an upward protruding manner and is close to one side of the pressure surface, and the second arc-shaped part is arranged in a downward recessed manner and is close to one side of the suction surface; a drainage channel (27) is arranged in or below the first arc-shaped part (25), the drainage channels are respectively communicated with the left end and the right end of the first arc-shaped part and are arc-shaped channels, and the drainage channel is used for guiding vortex at the right end of the first arc-shaped part to flow to the left end; the surface of the second arc-shaped part (26) is provided with arc-shaped grooves (28) which respectively extend to the left end and the right end of the second arc-shaped part, and the positions of the arc-shaped grooves correspond to the drainage channel; in the radial direction of the blade (2), a plurality of flow guide channels (27) and arc-shaped grooves (28) are arranged in an array type along the radial direction.

2. A semi-open impeller for controlling clearance leakage in centrifugal pumps according to claim 1, characterised in that the crescent-shaped cusp projection of the surface texture (4) faces the suction surface.

3. A semi-open impeller for controlling the clearance leakage of centrifugal pumps according to claim 2, characterized in that the inlet pipe (9) is provided on the outside with a plurality of circumferential grooves (3) which are concentric with the inlet pipe and lie in a plane parallel to the plane of the back cover plate (1).

4. A semi-open impeller for controlling clearance leakage in centrifugal pumps according to claim 3, characterised in that the axial height of the vanes (2) or impeller decreases with increasing distance from the impeller inlet.

5. A semi-open impeller for controlling the clearance leakage of centrifugal pumps according to claim 4, characterized in that the vanes (2) are of unequal thickness and the thickness of the vanes decreases from the radially inner end to the radially outer end.

6. The semi-open impeller for controlling the clearance leakage of the centrifugal pump according to claim 5, characterized in that for machining the surface texture (4), the material is selected from alloy materials or selected from ultra-high molecular weight polyethylene; the surface texture is textured by laser technology.

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