Semi-open centrifugal pump blade

Abstract

The utility model belongs to the technical field of centrifugal pump structural design, and particularly relates to a semi-open type centrifugal pump blade. The rear cover plate at least comprises a rear cover plate body, wherein an axis hole is formed in the center of the rear cover plate body; the blade further comprises a blade body and an airfoil structure; the blade body is connected to the rear cover plate; the blade body is of an arc-shaped structure; a zigzag microstructure is arranged on the outer surface of the front edge of the water inlet end of the blade body; the wing-shaped structure is connected to the rear cover plate and corresponds to the sawtooth-shaped micro-structure on the head portion of the blade body. Through the design of the wing-shaped structure and the sawtooth-shaped microstructure, the flow stability of fluid at the front edge is improved, the surface Reynolds stress peak value is reduced, cavitation inception is effectively restrained, the streaming resistance of the head of the blade is weakened, and the vortex strength of the tail edge of the pressure surface is reduced; and meanwhile, streamlines passing through a blade runner are more uniform, and the running flow stability of the whole unit is effectively improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to centrifugal pump structure design technical field, concretely relates to a half open type centrifugal pump blade. BACKGROUND

[0002] As the core equipment in the field of fluid delivery, the performance optimization of centrifugal pump has always been the research focus in engineering field. The half open type impeller is widely used in the field of solid medium delivery such as sewage treatment and petrochemical industry due to its simple structure and low manufacturing and maintenance cost. However, the traditional half open type impeller has significant technical bottlenecks in practical application: firstly, the absence of the back cover plate of the impeller leads to the intensification of the secondary flow phenomenon in the flow passage, which significantly reduces the hydraulic efficiency; secondly, the pressure difference between the working surface and the back surface of the blade causes transverse flow, which intensifies the flow separation and energy loss; thirdly, the conventional blade design cannot meet the dual requirements of low cavitation performance and high anti-blocking capacity. The existing improvement schemes are mostly focused on the parameter optimization of macro blade type, such as the combination of long and short blades or the design of three-dimensional twisted blades, which can improve the efficiency under certain working conditions, but generally have the problems of poor design adaptability and sharp increase in processing cost.

[0003] In recent years, the bionic surface microstructure technology provides a new idea for the performance improvement of impeller machinery. It has been proved in the aviation field that the bionic groove of shark skin can effectively reduce the flow resistance by more than 10%, and the micro-pit structure on the surface of gas turbine blade can significantly suppress flow separation. However, the existing researches are mostly focused on closed flow passage machinery, and there is still a lack of systematic research on the microstructure layout scheme for the specific asymmetric flow field characteristics of half open type impeller, especially the synergistic mechanism of microstructure and macro blade type has not been broken through. This technical gap leads to the difficulty of traditional half open type centrifugal pump to meet the strict requirements of modern industry on high efficiency, energy saving, wide range operation and adaptability to complex medium. UTILITY MODEL CONTENTS

[0004] The utility model provides a half open type centrifugal pump blade, one of its purposes is to provide a centrifugal pump blade which can effectively reduce the local pressure drop rate and weaken the water flow impact effect by changing the curvature and cross section shape of the flow passage; the second purpose is to provide a centrifugal pump blade which can form a gradual flow guide field at the inlet section of the impeller, realize the smooth transition of water flow to the internal flow passage of the impeller, and control the flow velocity fluctuation amplitude within ± 5%; the third purpose is to provide a centrifugal pump blade which can prevent flow separation at the suction surface of the blade, thereby improving the operation stability of the half open type centrifugal pump impeller.

[0005] To achieve the above purpose, the technical scheme adopted by the utility model is:

[0006] A semi-open centrifugal pump blade, at least comprising a back cover plate, the center of the back cover plate is provided with a shaft hole; further comprising a blade body and an airfoil structure; the blade body is connected to the back cover plate; the blade body is an arc structure; the front edge outer surface of the water inlet end of the blade body is provided with a sawtooth microstructure; the airfoil structure is connected to the back cover plate and is correspondingly arranged with the sawtooth microstructure of the head of the blade body.

[0007] The sawtooth microstructure comprises at least 3-5 parallelly arranged continuous sawtooth protrusions; the junctions of adjacent sawtooth protrusions form strip-shaped sawtooth grooves; the two side edges of the sawtooth grooves are perpendicular to each other.

[0008] The cross section of the sawtooth groove is an isosceles triangle.

[0009] The ratio of the height h1 of the sawtooth groove to the length L1 of the blade front edge is h1 / L1=1 / 4.

[0010] The thickness direction of the sawtooth groove is perpendicular to the plate surface of the back cover plate.

[0011] The ratio of the notch width b1 of the sawtooth groove to the head width B1 of the blade body is b1 / L1=1 / 2.

[0012] The airfoil structure is a circular arc shape, and the central angle thereof is 45°-90°.

[0013] The maximum thickness of the airfoil structure is 1 / 4-1 / 2 of the maximum thickness of the blade body.

[0014] The arc length of the middle arc line B of the airfoil structure is 1 / 4-1 / 2 of the arc length of the middle arc line A of the blade body.

[0015] The ratio of the thickness b2 of the airfoil structure to the width B1 of the blade body is b2 / L1=1 / 4; the ratio of the radius r of the middle arc line B of the airfoil structure to the radius R of the middle arc line A of the blade body is r / R=1 / 4; the distance L2 between the head of the middle arc line B of the airfoil structure and the head of the middle arc line A of the blade body is 1.5*L1; and the perpendicular distance L3 between the tail of the middle arc line B of the airfoil structure and the middle arc line A of the blade body is 2*L1.

[0016] Beneficial effects:

[0017] (1) The airfoil structure and the sawtooth microstructure are designed, and a double regulation mechanism of fluid dynamics is realized.

[0018] (2) The sawtooth array in the sawtooth microstructure produces an active flow guiding effect, so that a preset velocity gradient is formed before water flow enters the flow channel, and the front edge flow field form is effectively reconstructed under the synergistic effect of the airfoil structure, thereby converting the traditional straight-inflow into a gradual flow guiding mode.

[0019] (3) The wing type structure in the utility model can reduce the velocity gradient of the main flow and the boundary layer, and significantly improve the flow separation characteristics.

[0020] (4) The wing type structure in the utility model has a restraining effect on the vortex generation, so that the turbulent intensity keeps a linear growth mode in the flow development process, the sudden increase phenomenon in the traditional structure is avoided, and the energy loss of the flow channel system can be reduced and the operation stability can be improved.

[0021] The above description is only a summary of the technical scheme of the utility model, in order to more clearly understand the technical means of the utility model, and the content of the specification can be implemented, the following will be described in detail with the preferred embodiment of the utility model and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical scheme in the embodiment or the prior art, the drawings needed in the embodiment will be briefly introduced as follows, obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can be obtained without creative labor on the premise.

[0023] Fig. 1 It is the structural schematic diagram of the utility model.

[0024] Fig. 2 It is the local enlarged structural schematic diagram of the front edge of the blade of the centrifugal pump in the utility model.

[0025] Fig. 3 It is the design structural schematic diagram of the small wing type in the utility model.

[0026] In the drawing: 1, rear cover plate; 2, blade body; 2-1, middle camber line A; 3, sawtooth groove; 4, wing type structure; 4-1, middle camber line B. DETAILED DESCRIPTION

[0027] The technical scheme in the embodiments of the utility model will be described clearly and completely in combination with the drawings in the embodiments of the utility model, obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the utility model.

[0028] Embodiment:

[0029] According to Figs. 1-3The illustrated semi-open centrifugal pump blade at least comprises a back cover plate 1, the center of the back cover plate 1 is provided with a shaft hole; further comprising a blade body 2 and a wing structure 4; the blade body 2 is connected on the back cover plate 1; the blade body 2 is an arc structure; the water inlet end front edge outer surface of the blade body 2 is provided with a sawtooth microstructure; the wing structure 4 is connected on the back cover plate 1 and is correspondingly provided with the sawtooth microstructure of the blade body 2 head.

[0030] In actual use, a plurality of blade bodies 2 are provided on the back cover plate 1, and the blade bodies 2 are correspondingly provided with the wing structure 4. The plurality of blade bodies 2 are spirally arranged with the shaft hole as the center.

[0031] In some embodiments, the sawtooth microstructure at least comprises 3-5 continuously arranged parallel sawtooth protrusions; the junction of adjacent sawtooth protrusions forms a strip-shaped sawtooth groove 3; the two side edges in the sawtooth groove 3 are perpendicular to each other. Preferably, the continuously arranged sawtooth protrusions are 4.

[0032] The working principle of the utility model is: when the centrifugal pump normally operates, fluid enters the flow channel on the back cover plate 1 along the blade 2, rotates clockwise along the blade body 2, and the fluid enters the flow channel through the wing structure 4, so that the pressure gradient of the blade body 2 head is flattened, thereby delaying the time of initial cavitation and effectively limiting the development scale of the cavitation bubble group. The water flow further passes through the sawtooth groove 3, so that the peak value of the turbulent kinetic energy in the flow channel is reduced, and the energy dissipation rate is reduced. At the same time, the internal flow field structure is optimized, the viscous resistance and Reynolds stress near the blade body 2 are reduced, the energy spectrum distribution is shifted to large-scale vortex structure, and finally the effect of reducing the flow resistance around the blade body 2 head is achieved, and the number and intensity of vortexes near the pressure surface of the rear half of the impeller blade under the small flow condition and the design flow condition are reduced, and the unsteady flow oscillation phenomenon is effectively inhibited.

[0033] The sawtooth microstructure in the utility model is the sawtooth microstructure of the bionic shark pectoral fin front edge, which effectively increases the flow stability of the fluid at the front edge, reduces the flow resistance around the blade head, and reduces the vortex intensity of the pressure surface tail edge. At the same time, the flow lines in the blade flow channel are more uniform, and the flow stability of the overall unit operation is improved.

[0034] In some embodiments, the cross section of the sawtooth groove 3 is an isosceles triangle. In specific applications, the 60° top angle design of the isosceles triangle makes the near-wall fluid produce symmetrical secondary flow, forms stable double vortex structure, effectively inhibits flow separation and improves the critical Reynolds number. At the same time, the pressure gradient field generated by the isosceles configuration presents an axial symmetric distribution, so that the critical value of the cavitation number (σ) is improved, and the probability of cavitation is reduced.

[0035] In some embodiments, the ratio of the height h1 of the sawtooth-shaped groove 3 to the length L1 of the blade leading edge is h1 / L1=1 / 4. The reason for adopting the technical solution in specific applications is that this ratio design can effectively balance the guiding effect of the sawtooth-shaped groove 3 on fluid flow and the structural strength of the blade leading edge. A larger groove height can enhance the control ability of turbulent flow. The adoption of this ratio allows the formation of a stable low-pressure micro-vortex at the groove vertex, which can improve the critical Laplace pressure of the cavitation nucleus through the vortex transport mechanism, reduce the Reynolds stress peak at the leading edge, inhibit the formation and expansion of the cavitation nucleus, and delay the occurrence of cavitation.

[0036] In some embodiments, the thickness direction of the sawtooth-shaped groove 3 is perpendicular to the plate surface of the back cover plate 1. The adoption of the technical solution can make the opening direction of the sawtooth-shaped groove 3 consistent with the main flow direction of the fluid, forming a downstream guiding effect and reducing energy loss when the fluid is impacted. When cooperating with the airfoil structure 4, the vertically arranged groove can reconstruct the flow field form of the leading edge, making the main flow and the boundary layer velocity gradient gentle, and avoiding flow separation. The vertical arrangement of the groove effectively weakens the flow resistance around the blade head, makes the fluid more smoothly enter the flow passage, and reduces the local pressure drop rate. The dispersion of fluid impact force reduces the stress concentration at the edge of the sawtooth-shaped groove 3, prolonging the fatigue resistance of the blade.

[0037] In some embodiments, the ratio of the slot width b1 of the sawtooth-shaped groove 3 to the head width L1 of the blade body 2 is b1 / L1=1 / 2. The ratio design of the technical solution can effectively balance the guiding effect of the sawtooth-shaped groove 3 on fluid flow and the structural strength of the blade leading edge. The groove width of the technical solution can enhance the control ability of turbulent flow, while avoiding the decrease in structural strength caused by the sawtooth-shaped groove 3 being too wide. The reasonable groove width ratio in the technical solution disperses the fluid impact force, reduces the stress concentration at the edge of the groove, prolongs the fatigue resistance of the blade, makes the flow velocity distribution in the flow passage more uniform, reduces the peak value of turbulent kinetic energy, reduces energy dissipation, and improves the operating stability of the unit.

[0038] In some embodiments, the airfoil structure 4 is a circular arc shape with a central angle of 45°-90°. The adoption of the circular arc-shaped airfoil structure 4 can effectively guide fluid flow and reduce flow separation and turbulent flow generation. The design of a central angle of 45°-90° can ensure smooth fluid flow while avoiding flow instability or increased energy loss caused by a central angle that is too large or too small. The adoption of the technical solution makes the flow velocity distribution in the flow passage more uniform, reduces the peak value of turbulent kinetic energy, reduces energy dissipation, and improves the operating stability of the unit. The circular arc-shaped airfoil structure disperses the fluid impact force, reduces the stress concentration at the edge of the structure, and prolongs the fatigue resistance of the blade.

[0039] Further, the maximum thickness of the airfoil structure 4 is 1 / 4-1 / 2 of the maximum thickness of the blade body 2. The technical solution can effectively weaken the flow resistance of the fluid at the leading edge of the blade, so that the fluid enters the flow passage more smoothly, and the local pressure drop rate is reduced.

[0040] Further, the arc length of the camber line B4-1 of the airfoil structure 4 is 1 / 4-1 / 2 of the arc length of the camber line A2-1 of the blade body 2. The technical solution that the arc length of the camber line B4-1 is 1 / 4-1 / 2 of the arc length of the camber line A2-1 of the blade body 2 can ensure smooth fluid flow, while avoiding flow instability or energy loss increase caused by too long or too short airfoil structure. The fluid flow is effectively guided, and flow separation and turbulence generation are reduced.

[0041] In some embodiments, the ratio of the thickness b2 of the airfoil structure 4 to the width L1 of the blade body 2 is b2 / L1=1 / 4; the ratio of the radius r of the camber line B4-1 of the airfoil structure 4 to the radius R of the camber line A2-1 of the blade body 2 is r / R=1 / 4; the distance L2 between the head of the camber line B4-1 of the airfoil structure 4 and the head of the camber line A2-1 of the blade body 2 is 1.5*L1; and the vertical distance L3 between the tail of the camber line B4-1 of the airfoil structure 4 and the camber line A2-1 of the blade body 2 is 2*L1.

[0042] In specific applications, the reasonable matching of the thickness and the curvature (b2 / L1=1 / 4, r / R=1 / 4) disperses the fluid impact load, avoids stress concentration, and enhances the fatigue resistance. The head distance L2=1.5*L1 design avoids direct inflow, and converts the impact energy into horizontal flow energy. The matching of the curvature radii of the camber lines (r / R=1 / 4) reduces the peak value of the leading edge pressure gradient, effectively inhibits the generation and expansion of the cavitation nucleus.

[0043] In the case of no conflict, those skilled in the art can combine the technical features related in the above examples according to the actual situation to achieve the corresponding technical effects. For various combinations, this will not be described one by one.

[0044] It should be noted that all directionality indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between the components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directionality indications will also change accordingly.

[0045] In addition, the description of "first", "second" and the like in the present application is only for the purpose of description and should not be understood as indicating or implying relative importance or implying the number of the indicated technical features. Therefore, the features with "first" and "second" can be explicitly or implicitly included at least one of the features.

[0046] The above is only the preferred embodiment of the present application, and the present application will not be limited to the embodiments shown herein, but will be consistent with the widest range of principles and novel characteristics disclosed herein. Any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application still belong to the scope of the technical scheme of the present application.

Claims

1. A semi-open centrifugal pump blade, comprising at least a rear cover plate (1), wherein a central hole is provided at the center of the rear cover plate (1); characterized in that: It also includes a blade body (2) and an airfoil structure (4); the blade body (2) is connected to the rear cover plate (1); the blade body (2) is an arc-shaped structure; the outer surface of the water inlet end of the blade body (2) is provided with a serrated microstructure; the airfoil structure (4) is connected to the rear cover plate (1) and is provided in correspondence with the serrated microstructure at the head of the blade body (2).

2. The semi-open centrifugal pump blade as described in claim 1, characterized in that: The serrated microstructure includes at least 3 to 5 parallel continuous serrated strip protrusions; the junction of adjacent serrated strip protrusions forms a serrated groove (3); the two sides of the serrated groove (3) are perpendicular to each other.

3. The semi-open centrifugal pump blade as described in claim 2, characterized in that: The cross-section of the strip-shaped sawtooth groove (3) is an isosceles triangle.

4. The semi-open centrifugal pump blade as described in claim 2, characterized in that: The ratio of the height h1 of the strip-shaped serrated groove (3) to the blade leading edge length L1 is h1 / L1=1 / 4.

5. A semi-open centrifugal pump blade as described in claim 2, 3, or 4, characterized in that: The thickness direction of the serrated groove (3) is perpendicular to the surface of the rear cover plate (1).

6. A semi-open centrifugal pump blade as described in claim 2, 3, or 4, characterized in that: The ratio of the groove width b1 of the strip-shaped sawtooth groove (3) to the head width L1 of the blade body (2) is b1 / L1=1 / 2.

7. The semi-open centrifugal pump blade as described in claim 1, characterized in that: The airfoil structure (4) is arc-shaped with a central angle of 45° to 90°.

8. The semi-open centrifugal pump blade as described in claim 7, characterized in that: The maximum thickness of the airfoil structure (4) is 1 / 4 to 1 / 2 of the maximum thickness of the blade body (2).

9. A semi-open centrifugal pump blade as described in claim 7 or 8, characterized in that: The arc length of the mid-arc line B (4-1) of the airfoil structure (4) is 1 / 4 to 1 / 2 of the arc length of the mid-arc line A (2-1) of the blade body (2).

10. A semi-open centrifugal pump blade as described in claim 1 or 9, characterized in that: The ratio of the thickness b2 of the airfoil structure (4) to the width L1 of the blade body (2) is b2 / L1=1 / 4; the ratio of the radius r of the mid-arc line B (4-1) of the airfoil structure (4) to the radius R of the mid-arc line A (2-1) of the blade body (2) is r / R=1 / 4; the distance L2 between the head of the mid-arc line B (4-1) of the airfoil structure (4) and the head of the mid-arc line A (2-1) of the blade body (2) is 1.5*L1; the vertical distance L3 between the tail of the mid-arc line B (4-1) of the airfoil structure (4) and the mid-arc line A (2-1) of the blade body (2) is 2*L1.

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