A method, apparatus and medium for designing impeller blades of a low specific speed centrifugal pump

Abstract

This invention discloses a design method, apparatus, and medium for impeller blades of a low specific speed centrifugal pump. The method includes obtaining the impeller's geometric parameters based on design parameters; performing three-dimensional modeling based on the geometric parameters, dividing the three-dimensional model of the impeller into a mesh, performing steady-state calculations using CFD, and combining the calculation results with pre-input back profile coordinate points to obtain the relative and absolute velocities on the profile; obtaining the axial velocity, and determining the thickness S1 from the relationship between the axial velocity and the blade thickness; recalculating the thickness, remodeling the impeller in three dimensions, and obtaining the thickness S2 at each coordinate point; determining whether the difference between the thicknesses S1 and S2 is within a set range, and if so, the design meets the requirements. This invention uses curve fitting and function fitting methods based on the relationship between blade thickness and axial velocity. The method is simple and reasonable, and the impeller efficiency is significantly improved before and after the design. It can serve as a reference process for the engineering design of low specific speed blade thickness.

Description

Technical Field

[0001] This invention relates to a design method, device, and medium for impeller blades of a low specific speed centrifugal pump, belonging to the field of centrifugal pump technology. Background Technology

[0002] The specific speed range of centrifugal pumps is typically 30–300 rpm. <n s A flow rate of less than 80 rpm constitutes a low specific speed centrifugal pump. Low specific speed centrifugal pumps are characterized by low flow rate and high head, and are widely used in many economic fields such as irrigation, urban water supply, chemical industry, and national defense. The impeller is a crucial flow-through component of a low specific speed centrifugal pump, and its design significantly impacts pump performance. Low specific speed centrifugal pump impellers typically use cylindrical blades with unidirectionally curved surfaces, narrow blade outlet width, large impeller outer diameter, and a narrow and long axial flow channel. Cylindrical blades are simple in design, low in cost, and have fewer casting defects. Blade design methods mainly include unidimensional, bidimensional, and ternary design. However, none of these methods consider blade thickness design. Many studies indicate that blade thickness design is primarily based on experience, lacking a relatively reasonable calculation method. Therefore, developing a scientific design method is essential. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a design method, device and medium for impeller blades of a low specific speed centrifugal pump. Based on the relationship between blade thickness and axial velocity, curve fitting and function fitting methods are used for design. The method is simple and reasonable, and the impeller efficiency is significantly improved before and after the design.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0005] In a first aspect, the present invention provides a method for designing impeller blades for a low specific speed centrifugal pump, comprising:

[0006] Based on the design parameters, the geometric parameters of the impeller are calculated;

[0007] Based on the geometric parameters, a three-dimensional model of the impeller is obtained.

[0008] Step A includes: dividing the three-dimensional model of the impeller into a fluid domain mesh, performing steady-state calculations using CFD, and obtaining the results of the steady-state calculations;

[0009] Step B includes: combining the results of steady-state calculations with the pre-input coordinate points of the back profile to obtain the relative and absolute velocities on the profile.

[0010] Step C includes: obtaining the axial velocity based on the relative velocity and the pairing velocity, and obtaining the thickness S1 from the relationship between the axial velocity and the blade thickness;

[0011] Recalculate the thickness and remodel the impeller in 3D. Repeat steps A, B, and C to obtain the thickness S2 at each coordinate point.

[0012] Determine whether the thickness difference between S1 and S2 is within the set range. If so, the design meets the requirements.

[0013] Furthermore, the coordinate points of the back profile are determined using the equiangular spiral method.

[0014] Furthermore, the step of performing three-dimensional modeling based on geometric parameters to obtain a three-dimensional model of the impeller includes:

[0015] The impeller is modeled using 3D modeling software. The blade model is obtained by using the back profile with equal thickness to obtain the working surface profile, and then directly extruded to obtain a blade model with equal thickness.

[0016] The flow channel is extracted from the blade model of uniform thickness using 3D modeling software, and a corresponding 3D model of the pressure chamber and inlet section is designed to form the fluid domain for CFD calculation of the centrifugal pump.

[0017] Furthermore, step B includes:

[0018] By combining the steady-state calculation results with the pre-input back profile coordinate points, we obtain...

[0019]

[0020]

[0021] Where W is the relative velocity, V is the relative velocity, and Wu, Wv, Ww, Vu, Vv and Vw are the components of W and V in the x, y and z coordinates.

[0022] Furthermore, in step C, obtaining the axial velocity based on the relative velocity and the pairing velocity includes:

[0023] In a two-dimensional plane, x and y combine to obtain the radius value R, according to the formula:

[0024]

[0025] Find the circumferential velocity U at this point, where n is the rotational speed. Then, calculate the absolute fluid angle using the formula. Finally, calculate the axial velocity corresponding to each coordinate point using the formula.

[0026] Furthermore, in step C, the thickness S1 is obtained from the relationship between the axial velocity and the blade thickness, including:

[0027] Based on the relationship between axial velocity Vm and thickness:

[0028]

[0029] A=2πRbΨ

[0030]

[0031] Where Q is the flow rate, A is the impeller cross-sectional area, b is the blade width, ψ is the impeller outlet displacement coefficient, and Z is the number of blades, a fitting curve between the relative thickness S and the relative coordinate x can be obtained. The fitting yields a polynomial function, which is...

[0032] S = 45.095x 3 -99.477x 2 +69.495x-5.3886

[0033] Then, substitute the relative coordinates into the fitting function to obtain the relative thickness S1.

[0034] Furthermore, when determining whether the thickness difference between S1 and S2 is within the set range, if the thickness difference at the same point is within 5% and the number of points meeting this requirement accounts for 80% of the total number of points, then the design meets the requirements.

[0035] Secondly, the present invention provides a design device for impeller blades of a low specific speed centrifugal pump, comprising:

[0036] The geometric parameter calculation module is used to calculate the geometric parameters of the impeller based on the design parameters;

[0037] The model building module is used to perform 3D modeling based on geometric parameters to obtain the 3D model of the impeller;

[0038] The steady-state calculation module is used to divide the three-dimensional model of the impeller into a fluid domain mesh, perform steady-state calculations using CFD, and obtain the steady-state calculation results.

[0039] The relative and absolute velocity calculation module is used to combine the results of steady-state calculations with the pre-input coordinate points of the back profile to obtain the relative and absolute velocities on the profile.

[0040] The first thickness calculation module is used to obtain the axial surface velocity based on the relative velocity and the pairing velocity, and to obtain the thickness S1 from the relationship between the axial surface velocity and the blade thickness.

[0041] The second thickness calculation module is used to recalculate the thickness and remodel the impeller in three dimensions. Steps A, B, and C are repeated to obtain the thickness S2 at each coordinate point.

[0042] The judgment module is used to determine whether the thickness difference between S1 and S2 is within the set range. If so, the design meets the requirements.

[0043] Thirdly, the present invention provides an electronic device, including a processor and a storage medium;

[0044] The storage medium is used to store instructions;

[0045] The processor is configured to operate according to the instructions to perform the steps of the method according to any of the preceding claims.

[0046] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the preceding methods.

[0047] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0048] This invention provides a design method, device, and medium for impeller blades of a low specific speed centrifugal pump. Based on the relationship between blade thickness and axial velocity, curve fitting and function fitting methods are used for design. The method is simple and reasonable. The initial impeller model and volute model are generated using unstructured meshing software ICEM. This method covers functions such as geometry creation, geometry cleanup, generation of unstructured meshes and block hexahedral meshes, and mesh editing, providing an efficient and reliable analysis model. A numerical simulation of internal flow analysis is performed using CFX software, and the absolute and relative velocities of the back profile are calculated and output. Finally, the axial velocity and blade thickness at each point are calculated. The impeller efficiency is significantly improved after the design, replacing the long-used empirical judgment method. This can serve as a reference process for the engineering design of low specific speed blade thickness. Attached Figure Description

[0049] Figure 1 This is a flowchart of a low specific speed centrifugal pump impeller blade design method provided in an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of the fitted relative coordinates and relative thickness curves provided in an embodiment of the present invention;

[0051] Figure 3 This is a comparative schematic diagram of the impeller blades before design provided in an embodiment of the present invention;

[0052] Figure 4 This is a comparative schematic diagram of the impeller blades after the design provided in the embodiment of the present invention. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0054] Example 1

[0055] This embodiment introduces a method for designing impeller blades for a low specific speed centrifugal pump, including:

[0056] Based on the design parameters, the geometric parameters of the impeller are calculated;

[0057] Based on the geometric parameters, a three-dimensional model of the impeller is obtained.

[0058] Step A includes: dividing the three-dimensional model of the impeller into a fluid domain mesh, performing steady-state calculations using CFD, and obtaining the results of the steady-state calculations;

[0059] Step B includes: combining the results of steady-state calculations with the pre-input coordinate points of the back profile to obtain the relative and absolute velocities on the profile.

[0060] Step C includes: obtaining the axial velocity based on the relative velocity and the pairing velocity, and obtaining the thickness S1 from the relationship between the axial velocity and the blade thickness;

[0061] Recalculate the thickness and remodel the impeller in 3D. Repeat steps A, B, and C to obtain the thickness S2 at each coordinate point.

[0062] Determine whether the thickness difference between S1 and S2 is within the set range. If so, the design meets the requirements.

[0063] like Figure 1 As shown in the figure, the application process of the low specific speed centrifugal pump impeller blade design method provided in this embodiment involves the following steps:

[0064] Step 1: Calculate the geometric parameters of the impeller and volute based on the design parameters.

[0065] Step 2: Determine the profile of the back of the blade using the traditional equiangular spiral method and obtain a series of coordinate points.

[0066] Step 3: Use 3D modeling software to model the impeller. The blade model is obtained by using the back profile with equal thickness to obtain the working surface profile, and then directly extruded to obtain a blade model with equal thickness.

[0067] Step 4: Extract the flow channel part from the built 3D blade structure model using 3D modeling software, and design a corresponding 3D model of the pressure chamber and inlet section to form the fluid domain for CFD calculation of the centrifugal pump.

[0068] Step 5: Perform mesh generation and boundary condition setting for the inlet section, impeller, and pressure chamber respectively, then perform CFD calculations and import the calculation results into CFD-post.

[0069] Step Six: Analyze the numerical simulation results in CFD-post, insert the polyline command to input the coordinates of the back profile, and output the relative and absolute velocity components of each coordinate point.

[0070] Step 7: Calculate the axial velocity of each point based on the relative and absolute velocities, convert the coordinate points into relative coordinates, and fit the blade thickness curve and thickness function based on the relationship between the axial velocity and the blade thickness.

[0071] Step 8: Calculate the thickness corresponding to each point again using the fitted function, keeping the blade back profile unchanged, and thicken the blade again based on the calculated values.

[0072] Step 9: Redesign the impeller water body diagram, and repeat steps 5 and 6.

[0073] Step 10: Recalculate the thickness of each point. If the number of points where the thickness difference of the same point before and after the design is within 5% accounts for 80% of the total number of points, then the design meets the requirements.

[0074] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0075] The purpose of this invention is to provide a method for designing the blade thickness of a low specific speed centrifugal pump impeller. Taking a cylindrical blade of a low specific speed centrifugal pump impeller as an example, the specific steps are as follows:

[0076] Based on the design condition of the centrifugal pump, Q = 50m 3 / s, H=53.2m, rotational speed is 2900r / min;

[0077] A low specific speed centrifugal pump was designed based on the "Modern Pump Technology Handbook" published by Aerospace Publishing House, and the initial geometric parameters of the impeller and the impeller inlet diameter d were obtained. j =86mm, hub diameter d n =23.5mm, impeller outer diameter d2=260mm, blade outlet width b2=10mm. The coordinates of the key points on the back of the blade are obtained by using an equiangular helix, as shown in Table 1.

[0078] Table 1 Geometric parameter values ​​during the design process

[0079]

[0080]

[0081] Continued table

[0082]

[0083]

[0084]

[0085] The 3D models of the volute and inlet section were obtained through calculation and 3D modeling. The main parameters are: base circle diameter d3 = 216 mm, volute inlet width b3 = 10 mm, and the diameter d of the inlet section circular pipe is 23.5 mm.

[0086] The point coordinates were input using Pro / E to obtain the blade's back profile. A uniform thickness was then applied during extrusion to obtain the blade's 3D model, as shown in the attached image. Figure 3 Draw the impeller flow channel diagram, volute, and inlet section hydraulic diagram.

[0087] The fluid domain was meshed using an unstructured mesh, resulting in an impeller mesh count of 98,559. Steady-state calculations were performed in CFX, with a velocity inlet and a free pressure outlet, and 1,500 iterations were performed.

[0088] The output results are presented in CFD-post. The Polyline command is used to import the coordinates of the back face to generate the back face profile, outputting the absolute and relative velocities in the u, v, and w directions.

[0089]

[0090]

[0091] Where W is the relative velocity, V is the relative velocity, and Wu, Wv, Ww, Vu, Vv and Vw are the components of W and V in the x, y and z coordinates;

[0092] In a two-dimensional plane, x and y combine to obtain the radius value R, according to the formula...

[0093]

[0094] The circumferential velocity U at this point can be calculated, where n is the rotational speed. Then, the absolute flow angle can be determined using the formula, and finally, the axial velocity corresponding to each coordinate point can be calculated using the formula. The overall back profile is equated to a range of 0 to 1, yielding the values ​​for the relative coordinate points. See the appendix for details. Figure 2 .

[0095] Based on the relationship between axial velocity Vm and thickness

[0096]

[0097] A=2πRbΨ

[0098]

[0099] Where Q is the flow rate, A is the impeller cross-sectional area, b is the blade width, ψ is the impeller outlet displacement coefficient, and Z is the number of blades, a fitting curve between the relative thickness S and the relative coordinate x can be obtained. The fitting yields a polynomial function, which is...

[0100] S = 45.095x 3 -99.477x 2 +69.495x-5.3886

[0101] Then, substitute the relative coordinates into the fitting function to obtain the relative thickness.

[0102] Finally, the obtained data was used to remodel the blade, keeping the blade profile unchanged on the back side and thickening it towards the working surface. A new impeller was then created, and the new impeller model was meshed. While maintaining the boundary conditions, calculations were performed in CFX, and the absolute and relative velocities on the back profile were re-output. The axial velocity was then calculated to determine the blade thickness. The thickness at each point was compared to the original blade. If the thickness difference at the same point was within 5%, and the number of points meeting this requirement accounted for 80% of the total number of points, then the design met the requirements. The final blade obtained according to this design method is shown below. Figure 4 As shown.

[0103] The final blade was modeled, meshed, and the mesh count was maintained. The volute and inlet section remained unchanged. The same boundary conditions were used in CFX to obtain the calculation results, yielding new head and efficiency. The final results showed a significant improvement in efficiency, indicating that the new design method met the requirements.

[0104] Example 2

[0105] This embodiment provides a design device for impeller blades of a low specific speed centrifugal pump, including:

[0106] The geometric parameter calculation module is used to calculate the geometric parameters of the impeller based on the design parameters;

[0107] The model building module is used to perform 3D modeling based on geometric parameters to obtain the 3D model of the impeller;

[0108] The steady-state calculation module is used to divide the three-dimensional model of the impeller into a fluid domain mesh, perform steady-state calculations using CFD, and obtain the steady-state calculation results.

[0109] The relative and absolute velocity calculation module is used to combine the results of steady-state calculations with the pre-input coordinate points of the back profile to obtain the relative and absolute velocities on the profile.

[0110] The first thickness calculation module is used to obtain the axial surface velocity based on the relative velocity and the pairing velocity, and to obtain the thickness S1 from the relationship between the axial surface velocity and the blade thickness.

[0111] The second thickness calculation module is used to recalculate the thickness and remodel the impeller in three dimensions. Steps A, B, and C are repeated to obtain the thickness S2 at each coordinate point.

[0112] The judgment module is used to determine whether the thickness difference between S1 and S2 is within the set range. If so, the design meets the requirements.

[0113] Example 3

[0114] This embodiment provides an electronic device, including a processor and a storage medium;

[0115] The storage medium is used to store instructions;

[0116] The processor is configured to operate according to the instructions to perform the steps of the method according to any one of Embodiment 1.

[0117] Example 4

[0118] This embodiment provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the methods described in Embodiment 1.

[0119] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of designing a low specific speed centrifugal pump impeller blade, characterized by, include: Based on the design parameters, the geometric parameters of the impeller are calculated; Based on the geometric parameters, a three-dimensional model of the impeller is obtained. Step A includes: dividing the three-dimensional model of the impeller into a fluid domain mesh, performing steady-state calculations using CFD, and obtaining the results of the steady-state calculations; Step B includes: combining the results of steady-state calculations with the pre-input coordinate points of the back profile to obtain the relative and absolute velocities on the profile. Step C includes: obtaining the axial velocity based on the relative velocity and the pairing velocity, and obtaining the thickness S1 from the relationship between the axial velocity and the blade thickness; Recalculate the thickness and remodel the impeller in 3D. Repeat steps A, B, and C to obtain the thickness S2 at each coordinate point. Determine whether the thickness difference between S1 and S2 is within the set range. If so, the design meets the requirements. Step B includes: By combining the steady-state calculation results with the pre-input back profile coordinate points, we obtain... Where W is the relative velocity, V is the relative velocity, and Wu, Wv, Ww, Vu, Vv and Vw are the components of W and V in the x, y and z coordinates; In step C, obtaining the axial velocity based on the relative velocity and the pairing velocity includes: In a two-dimensional plane, x and y combine to obtain the radius value R, according to the formula: Find the circumferential velocity U at this point, where n is the rotational speed. Then, calculate the absolute fluid angle using the formula. Finally, calculate the axial velocity corresponding to each coordinate point using the formula. In step C, the thickness S1 is obtained from the relationship between the axial velocity and the blade thickness, including: Based on the relationship between axial velocity Vm and thickness: Where Q is the flow rate, A is the impeller cross-sectional area, b is the blade width, ψ is the impeller outlet displacement coefficient, and Z is the number of blades, a fitting curve between the relative thickness S and the relative coordinate x can be obtained. The fitting yields a polynomial function, which is... Then, substitute the relative coordinates into the fitting function to obtain the relative thickness S1.

2. The low specific speed centrifugal pump impeller blade design method of claim 1, wherein The coordinate points of the back profile are determined using the equiangular spiral method.

3. The low specific speed centrifugal pump impeller blade design method of claim 1, wherein The process of performing three-dimensional modeling based on geometric parameters to obtain a three-dimensional model of the impeller includes: The impeller is modeled using 3D modeling software. The blade model is obtained by using the back profile with equal thickness to obtain the working surface profile, and then directly extruded to obtain a blade model with equal thickness. The flow channel is extracted from the blade model of uniform thickness using 3D modeling software, and a corresponding 3D model of the pressure chamber and inlet section is designed to form the fluid domain for CFD calculation of the centrifugal pump.

4. The low specific speed centrifugal pump impeller blade design method of claim 1, wherein When determining whether the thickness difference between S1 and S2 is within the set range, if the thickness difference at the same point is within 5% and the number of points that meet this requirement accounts for 80% of the total number of points, then the design meets the requirements.

5. A device for designing impeller blades for a low specific speed centrifugal pump, used to implement the method for designing impeller blades for a low specific speed centrifugal pump according to any one of claims 1-4, characterized in that, include: The geometric parameter calculation module is used to calculate the geometric parameters of the impeller based on the design parameters; The model building module is used to perform 3D modeling based on geometric parameters to obtain the 3D model of the impeller; The steady-state calculation module is used to divide the three-dimensional model of the impeller into a fluid domain mesh, perform steady-state calculations using CFD, and obtain the steady-state calculation results. The relative and absolute velocity calculation module is used to combine the results of steady-state calculations with the pre-input coordinate points of the back profile to obtain the relative and absolute velocities on the profile. The first thickness calculation module is used to obtain the axial velocity based on the relative velocity and the pairing velocity, and to obtain the thickness S1 from the relationship between the axial velocity and the blade thickness. The second thickness calculation module is used to recalculate the thickness and remodel the impeller in three dimensions. Steps A, B, and C are repeated to obtain the thickness S2 at each coordinate point. The judgment module is used to determine whether the thickness difference between S1 and S2 is within the set range. If so, the design meets the requirements.

6. An electronic device, characterized in that: Including processor and storage media; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When executed by a processor, the program implements the steps of the method according to any one of claims 1 to 4.

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