Impeller capable of improving cavitation resistance of centrifugal pump

Abstract

The impeller capable of improving the cavitation resistance of the centrifugal pump comprises a front cover plate, a rear cover plate and a plurality of blades, the blades are evenly distributed between the front cover plate and the rear cover plate, a plurality of miniature vortex generator sets are evenly distributed on the front edge of the suction face of each blade, the number z of the blades ranges from 3 to 7, and the number z of the blades ranges from 3 to 7. The inlet placing angle beta 1 of the blades ranges from 35 degrees to 70 degrees, the outlet placing angle beta 2 of the blades ranges from 30 degrees to 50 degrees, the wrap angle theta of the blades ranges from 40 degrees to 100 degrees, and the miniature vortex flow generator sets are evenly arranged on the front edges of the suction faces of the blades in the axial direction of the impeller. Through the arrangement of the multiple micro vortex flow generator sets, laminar flow boundary layer separation can be restrained or delayed, cavitation inception can be delayed, and propulsion of back jet flow can be slowed down in the serious cavitation stage, so that the cavitation evolution period is weakened, and the anti-cavitation performance of the impeller is improved.

Description

Technical Field

[0001] The present application relates to the technical field of impellers, and in particular to an impeller capable of improving the anti-cavitation performance of a centrifugal pump. Background Art

[0002] With the development of science and technology, the importance of fluid machinery has become increasingly prominent, and centrifugal pumps, as the core power equipment for fluid transportation, are widely used in various fields such as chemical industry, domestic water supply, agricultural irrigation, etc. The process of the generation, development and collapse of cavitation bubbles is called cavitation. Cavitation is a common but very harmful phenomenon in centrifugal pump applications. It not only causes the decline of the hydraulic performance of the pump and the corrosion of the flow-through components, but also causes severe vibration and noise of the unit, which has a great impact on the safe and stable operation of the entire unit. When cavitation develops to a certain extent, the pump can completely fail to work normally.

[0003] The anti-cavitation performance of a centrifugal pump refers to its ability to effectively prevent gas aggregation and cavitation when there are gas or bubbles in the liquid. As one of the key components of a centrifugal pump, the impeller has an important influence on the anti-cavitation performance of the centrifugal pump. Optimizing the structural design of the impeller is crucial to improving its anti-cavitation performance. Summary of the invention

[0004] In order to improve the anti-cavitation performance, the present application provides an impeller that can improve the anti-cavitation performance of a centrifugal pump.

[0005] The present application provides an impeller that can improve the anti-cavitation performance of a centrifugal pump by adopting the following technical solution: An impeller capable of improving the anti-cavitation performance of a centrifugal pump comprises a front cover plate, a rear cover plate and a plurality of blades, wherein the blades are evenly distributed between the front cover plate and the rear cover plate, and a plurality of micro vortex flow generator groups are evenly distributed on the front edge of the suction face of each blade.

[0006] Preferably, the number of blades z=3~7, the inlet placement angle β1 of the blades is 35°~70°, the outlet placement angle β2 is 30°~50°, and the wrap angle θ is 40°~100°.

[0007] Preferably, a plurality of the micro vortex flow generator groups are evenly arranged along the axial direction of the impeller in front of the suction surface of the blade.

[0008] Preferably, each of the micro vortex flow generator groups includes two micro vortex flow generators arranged at intervals, the two micro vortex flow generators are arranged in an eight-shaped shape, and the angles between the two micro vortex flow generators and the water flow direction are a and b respectively, wherein a=b.

[0009] Preferably, the micro vortex flow generator is in the shape of a triangular prism and has a front end and a tail end. The front end of the micro vortex flow generator is close to the front edge of the suction face of the blade, and the front end thickness of the micro vortex flow generator is smaller than the tail end thickness.

[0010] Preferably, the length L1 of the micro vortex flow generator is 0.004X~0.007X, and the width W1 is 0.001X~0.003X, wherein X is the length of the blade; The tail end height of the micro vortex generator is H=0.1 δ ~0.5 δ ,in δ is the boundary layer thickness at the tail end of the micro vortex flow generator.

[0011] Preferably, the angle α between the upper surface of the micro vortex flow generator and the tangent line of the contact point between its front end and the suction surface of the blade is 25°~90°.

[0012] Preferably, the distance between two adjacent micro vortex flow generators is W2=0.0035X~0.0065X, and the distance between two identically arranged micro vortex flow generators in two adjacent micro vortex flow generator groups is L2=0.0025X~0.0045X, wherein X is the length of the blade.

[0013] Preferably, the micro vortex generator is located at the front end of the laminar separation point of the blade suction surface, and the distance between the micro vortex generator and the laminar separation point is L3=0.01X~0.1X, where X is the length of the blade; The position of the laminar separation point is determined by formula ①, when the friction coefficient c f = 0, the point closest to the front edge of the blade suction surface is the laminar separation point; Formula ① is as follows: ①; in, c f is the friction coefficient, τ w is the blade wall shear stress, ρ l is the liquid density, u ∞ is the inlet flow rate, liquid density ρ l and inlet flow rate u ∞ Defined as a constant.

[0014] Preferably, in the calculation of the position of the laminar separation point: The internal flow field of the impeller is simulated and calculated by CFD software to determine the distribution of the shear stress on the blade wall; The distribution of friction coefficient on the blade surface is obtained through formula ①; When the friction coefficient c f =0, the point closest to the front edge of the blade suction surface is the laminar separation point.

[0015] In summary, the present application includes at least one of the following beneficial technical effects: The present application can suppress or postpone laminar boundary layer separation and delay cavitation initiation by setting up several micro vortex flow generator groups. In the severe cavitation stage, the propulsion of the back jet flow is slowed down, thereby weakening the cavitation evolution cycle to improve the anti-cavitation performance of the impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the three-dimensional structure of the impeller according to the present invention that can improve the anti-cavitation performance of the centrifugal pump.

[0017] Figure 2 This is a cross-sectional view of the impeller described in the present invention.

[0018] Figure 3 This is a schematic diagram of the three-dimensional structure of the blade described in the present invention.

[0019] Figure 4 This is an enlarged view of the three-dimensional structure of the leading edge of the blade described in the present invention.

[0020] Figure 5 This is a top view of the leading edge of the blade according to the present invention.

[0021] Figure 6 This is a local detail diagram of the micro vortex flow generator described in the present invention.

[0022] Figure 7 It is a comparison diagram of the cavitation margin of the original model and the embodiment.

[0023] Explanation of the reference numerals: 1. front cover plate; 2. blades; 3. rear cover plate; 21, 22. micro vortex generator. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0025] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] An impeller capable of improving the anti-cavitation performance of a centrifugal pump, referring to Figure 1 and Figure 2 As shown, it includes a front cover plate 1, a rear cover plate 3 and a plurality of blades 2, wherein the plurality of blades 2 are evenly distributed between the front cover plate 1 and the rear cover plate 3, and the number of blades 2 is z=3-7. In one embodiment, the number of blades 2 is z=6.

[0029] A mounting shaft hole is provided at the center of the impeller, and six blades 2 are evenly distributed in a vortex shape around the mounting shaft hole between the front cover plate 1 and the rear cover plate 3. A flow channel is formed between adjacent blades 2. A water inlet is provided on the front cover plate 1, and the flow channel is communicated with the water inlet. The end of the blade 2 close to the mounting shaft hole is the suction surface, and the end of the blade 2 away from the mounting shaft hole is the water outlet surface.

[0030] The inlet placement angle β1 of the blade 2 is 35°~70°, the outlet placement angle β2 is 30°~50°, and the wrap angle θ is 40°~100°. In one embodiment, the inlet placement angle β1 of the blade 2 is 60°, the outlet placement angle β2 is 30°, and the wrap angle θ is 60°.

[0031] A plurality of micro vortex flow generator groups 21, 22 are evenly distributed on the front edge of the suction face of each blade 2, and the plurality of micro vortex flow generator groups are evenly arranged on the front edge of the suction face of the blade 2 along the axial direction of the impeller.

[0032] Reference Figure 3 , Figure 4 and Figure 5 As shown, each micro vortex generator group 21, 22 includes two micro vortex generators arranged at intervals, and the two micro vortex generators are arranged in an eight-shaped shape. The angles between the two micro vortex generators and the flow direction of the water body are a and b respectively, wherein a=b=18°, and the flow direction of the water body is the flow direction of the water body after entering the flow channel of the blade 2.

[0033] Specifically, the micro vortex flow generator has a front end and a tail end. The front end of the micro vortex flow generator is close to the front edge of the suction surface of the blade 2. Two adjacent micro vortex flow generators are arranged in an eight-shaped shape. The front ends of the two micro vortex flow generators are far away from each other, and the tail ends of the two micro vortex flow generators are close to each other.

[0034] Reference Figure 6 As shown, the micro vortex generator is in the shape of a triangular prism, the front end thickness of the micro vortex generator is smaller than the rear end thickness, and the angle α between the upper surface of the micro vortex generator and the tangent line of the contact point between its front end and the suction surface of the blade 2 is 25°~90°. In one embodiment, α=58°.

[0035] The length L1 of the micro vortex flow generator is 0.004X~0.007X, and the width W1 is 0.001X~0.003X, wherein X is the length of the blade 2.

[0036] The tail height of the micro vortex generator is H = 0.1 δ ~0.5 δ ,in δ is the boundary layer thickness at the tail end of the micro vortex flow generator. The boundary layer thickness can be obtained by CFD software simulation calculation. By calculating the internal flow field of the impeller with CFD software, the velocity distribution inside the impeller can be obtained, starting from the front edge wall of the suction surface of blade 2, and the flow velocity along the tangential direction of the wall of blade 2 reaches the inlet flow velocity. u ∞ The height of the 99% position perpendicular to the wall of blade 2 is δ .

[0037] The distance W2 between two adjacent micro vortex flow generators is 0.0035X~0.0065X, and the distance W2 is the distance W2 between the tail ends of two adjacent micro vortex flow generators.

[0038] The distance L2 between two identically arranged micro-vortex flow generators in two adjacent micro-vortex flow generator groups 21 and 22 is 0.0025X to 0.0045X, where X is the length of the blade 2. It is worth noting that the identically arranged two micro-vortex flow generators refer to two micro-vortex flow generators facing the same direction. Figure 5 As a reference direction, the micro vortex generators on the left / right sides of two adjacent micro vortex generator groups 21, 22 are arranged in the same way, and the distance L2 can be the distance L2 between the head ends of two micro vortex generators of the same arrangement, or the distance L2 between the tail ends of two micro vortex generators of the same arrangement.

[0039] In one embodiment, the length X of the blade 2 refers to the actual arc length of the blade 2. In another embodiment, the length X of the blade 2 refers to the length of the line between the head end and the tail end of the blade 2. The length X of the blade 2 can be selected according to actual needs and is not specifically limited in this embodiment.

[0040] The installation position of the micro vortex flow generator is described below.

[0041] Reference Figure 5 As shown, the micro vortex generator is located at the front end of the laminar separation point LFSP on the suction surface of the blade 2, and the distance L3 between the micro vortex generator and the laminar separation point LFSP is 0.01X~0.1X, where X is the length of the blade 2; The position of the laminar separation point LFSP is determined by formula ①, when the friction coefficient c f = 0, the point closest to the front edge of the suction surface of blade 2 is the laminar separation point LFSP; Formula ① is as follows: ①; in, c f is the friction coefficient, τ w is the shear stress on the blade 2 wall, ρ l is the liquid density, u ∞ is the inlet flow rate, liquid density ρ l and inlet flow rate u ∞ Defined as a constant.

[0042] The position of the laminar separation point LFSP is calculated: The internal flow field of the impeller is simulated and calculated by CFD software to determine the distribution of the shear stress on the wall of blade 2, that is, the relationship between the shear stress on the wall of blade 2 and the spatial position of blade 2 can be determined; The distribution of the friction coefficient on the surface of the blade 2 is obtained by formula ①, that is, the relationship between the friction coefficient and the spatial position of the blade 2 is obtained; When the friction coefficient c f =0, the point closest to the front edge of the suction surface of blade 2 is the laminar separation point LFSP.

[0043] The distance L3 between the micro vortex flow generator and the laminar flow separation point LFSP is the distance L3 between the tail end of the micro vortex flow generator and the laminar flow separation point LFSP.

[0044] In one embodiment, the specific values ​​of the micro vortex flow generator are: micro vortex flow generator length L1=1mm, width W1=0.4mm, tail end height H=0.3mm, distance between two adjacent micro vortex flow generators W2=1mm, distance between two identically arranged micro vortex flow generators in two adjacent micro vortex flow generator groups 21, 22 L2=2.5mm, distance between the micro vortex flow generator and the laminar separation point LFSP L3=2mm.

[0045] Reference Figure 7 As shown in the figure, the NPSH curves obtained by numerical simulation of the original impeller and the embodiment impeller are given, where the design flow rate of the centrifugal pump is 20m 3 / h, the design head is 70m, and the speed is 2900rpm. It can be found that the head of the original model decreases by about 3% when the NPSH is about 4m, which is regarded as the initiation of cavitation. Compared with the original model, the head of the impeller of this embodiment first rises abnormally and then decreases after the NPSH decreases to 6m, and the NPSH corresponding to the 3% decrease in head is lower than that of the original model, indicating that the micro vortex generator can improve the anti-cavitation performance of the centrifugal pump.

[0046] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0047] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. An impeller capable of improving the anti-cavitation performance of a centrifugal pump, characterized in that: It comprises a front cover plate (1), a rear cover plate (3) and a plurality of blades (2), wherein the plurality of blades (2) are evenly distributed between the front cover plate (1) and the rear cover plate (3), and a plurality of micro vortex flow generator groups (21, 22) are evenly distributed on the front edge of the suction surface of each blade (2).

2. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 1, characterized in that: The number of blades (2) is z=3-7, the inlet placement angle β1 of the blades (2) is 35°-70°, the outlet placement angle β2 is 30°-50°, and the wrap angle θ is 40°-100°.

3. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 1, characterized in that: A plurality of the micro vortex flow generator groups are evenly arranged along the axial direction of the impeller on the suction front edge of the blade (2).

4. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 1, characterized in that: Each of the micro vortex flow generator groups (21, 22) comprises two micro vortex flow generators arranged at intervals, the two micro vortex flow generators are arranged in an eight-shaped shape, and the angles between the two micro vortex flow generators and the flow direction of the water body are respectively a and b, wherein a=b.

5. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 4, characterized in that: The micro vortex flow generator is in the shape of a triangular prism and has a front end and a rear end. The front end of the micro vortex flow generator is close to the front edge of the suction face of the blade (2), and the thickness of the front end of the micro vortex flow generator is less than the thickness of the rear end.

6. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 5, characterized in that: The micro vortex generator has a length L1=0.004X~0.007X and a width W1=0.001X~0.003X, wherein X is the length of the blade (2); The tail end height of the micro vortex generator is H=0.1 δ ~0.5 δ ,in δ is the boundary layer thickness at the tail end of the micro vortex flow generator.

7. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 5, characterized in that: The angle α between the upper surface of the micro vortex generator and the tangent line of the contact point between its front end and the suction surface of the blade (2) is 25° to 90°.

8. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 4, characterized in that: The distance between two adjacent micro vortex flow generators is W2=0.0035X~0.0065X, and the distance between two identically arranged micro vortex flow generators in two adjacent micro vortex flow generator groups (21, 22) is L2=0.0025X~0.0045X, wherein X is the length of the blade (2).

9. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 1, characterized in that: The micro vortex generator is located at the front end of the laminar flow separation point (LFSP) of the suction surface of the blade (2), and the distance L3 between the micro vortex generator and the laminar flow separation point (LFSP) is 0.01X~0.1X, where X is the length of the blade (2); The position of the laminar flow separation point (LFSP) is determined by formula ①, when the friction coefficient c f = 0, the point closest to the suction front edge of blade (2) is the laminar flow separation point (LFSP); Formula ① is as follows: ①； in, c f is the friction coefficient, τ w is the shear stress on the blade (2) wall, ρ l is the liquid density, u ∞ is the inlet flow rate, liquid density ρ l and inlet flow rate u ∞ Defined as a constant.

10. The impeller capable of improving the anti-cavitation performance of a centrifugal pump according to claim 9, characterized in that: The position of the laminar flow separation point (LFSP) is calculated as: The flow field inside the impeller is simulated and calculated by CFD software to determine the distribution of the shear stress on the wall of the blade (2); The distribution of the friction coefficient on the surface of the blade (2) is obtained by formula ①; When the friction coefficient c f = 0, the point closest to the front edge of the suction surface of the blade (2) is the laminar flow separation point (LFSP).

Images