Design method and system for blade profile and impeller system of multi-wing centrifugal fan

Abstract

The invention discloses a design method and system for a blade profile and an impeller system of a multi-blade centrifugal fan. The design method comprises the following steps that (1) basic structure parameters of an impeller are primarily selected based on target parameters; (2) according to the inner diameter D1, the outer diameter D2, the inlet angle beta1A and the outlet angle beta2A of the impeller, a basic single-arc blade molded line C is generated, and model selection is checked through numerical simulation; (3) the molded line shrinkage and expansion rate b is specified, and a logarithmic spiral line S: # imgabs0 # is generated to serve as a blade molded line; (4) the blade number Z and the blade width d are specified, the width of an impeller runner is calculated, the value of the parameter b is changed, the inward contraction or outward expansion rate of the curve is adjusted, and an impeller system containing a constant-speed blade channel or a constant-acceleration blade channel is obtained; and 5) verifying constraint conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of centrifugal fan design, and in particular relates to a design method and system for blade profiles and impeller systems of a multi-blade centrifugal fan. Background Art

[0002] Multi-blade centrifugal fans have the advantages of compact structure, low noise, and high flow and pressure coefficients, and are widely used in fields such as air conditioning and ventilation systems. Within the fan structure, the blades have a significant impact on fan performance. Traditional blade designs use a single arc profile, with a smaller number using airfoil shapes or bionic approaches, which have achieved a certain degree of optimization in aerodynamic performance through innovative design. These methods each have their own advantages and disadvantages: the traditional single arc blade design is very simple and easy to manufacture and process, but the parameters are limited. Once the basic structural parameters are determined, it is difficult to adjust the impeller channel and achieve complex flow control, which makes it difficult to produce flow separation on the blades and form secondary vortices, resulting in low impeller efficiency. While the airfoil structure and bionic shape greatly optimize the blade shape and change the structure of the impeller channel through precise adjustment, achieving complex flow control, they are difficult to design, manufacture, and process, making large-scale industrial application difficult. Summary of the Invention

[0003] The content of this application is used to briefly introduce concepts that will be described in detail in the detailed description section below. The content of this application is not intended to identify key features or essential features of the technical solution for which protection is sought, nor is it intended to limit the scope of the technical solution for which protection is sought.

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a method and system for designing blade profiles and impeller systems for a multi-blade centrifugal fan.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for designing a blade profile and an impeller system for a multi-blade centrifugal fan, comprising the following steps:

[0006] 1) Preliminary selection of impeller basic structural parameters based on target parameters: Determine the target aerodynamic performance parameters of the multi-blade centrifugal fan based on experience and design requirements; Based on the established target parameters, select appropriate impeller basic structural parameters based on the model library, design experience, etc.

[0007] 2) Generate and verify a basic single-arc blade profile: Generate a single-arc blade profile based on the basic structural parameters of the impeller to obtain the initial design impeller; preliminarily evaluate the aerodynamic performance and verify whether the initial impeller performance constructed with the selected parameters reaches 80% to 90% of the target parameters;

[0008] 3) Construct a logarithmic spiral blade profile: Specify the profile shrinkage rate b to generate a logarithmic spiral: Based on the specified five parameters and a single arc as the initial solution, a set of equations is constructed and numerically solved to obtain the initial radius a of the logarithmic spiral, the offset coordinates (x s ,y s ) and the starting and ending angles θ1 and θ2, thereby obtaining the blade profile;

[0009] 4) Determine whether the impeller channel is reasonable: calculate the width of the impeller channel, modify the blade profile, and obtain an impeller with a constant velocity channel or a constant acceleration channel; based on step 3), combine the two parameters of blade number Z and blade thickness d to calculate the width of the impeller channel formed between the pressure surface and suction surface of two adjacent blades; change b to adjust the profile to shrink inward or expand outward and its rate, thereby changing the width of the impeller channel;

[0010] 5) Verify the constraints: Check whether the flow and pressure constraints of the fan design meet the design requirements. When the constraints meet the design requirements, the design of the multi-blade centrifugal fan impeller system is completed. Otherwise, adjust the basic structural parameters of the impeller or readjust the b value.

[0011] Furthermore, in step 1), the aerodynamic performance parameters include flow rate, total pressure, shaft power, and total pressure efficiency; the basic structural parameters of the multi-blade centrifugal fan impeller include the impeller inner diameter D1, the impeller outer diameter D2, the inlet angle β 1A , outlet angle β 2A , number of blades Z, blade thickness d.

[0012] In step 2), the single arc blade profile is obtained, including the arc center (x c ,y c ) and arc radius R k , its specific geometric relationship is:

[0013]

[0014] x c =R k sin(β 2A ),y c =D2 / 2+R k cos(β 2A ).

[0015] Furthermore, after step 2), the method further comprises the following steps:

[0016] Evaluate aerodynamic performance: Check aerodynamic performance. When the aerodynamic performance is far below the requirement, readjust the basic structural parameters of the impeller to make the aerodynamic performance reach 80% to 90% of the target parameters.

[0017] Furthermore, in step 3), the parameters a,x of the logarithmic spiral s ,y sDetermined by numerically solving the following system of equations:

[0018]

[0019]

[0020] Let the initial values of a, θ1, θ2 be R k ,π / 2,π, numerically solve the above equation to obtain the numerical solution; where θ1 and θ2 are the parameters of the intersection of the logarithmic spiral with the inner diameter circle and the outer diameter circle, so x s ,y s The results are as follows:

[0021]

[0022] Furthermore, in step 4), the definition and solution method of the impeller channel width are as follows:

[0023] For a certain position i in the blade flow channel, the center of the tangent circle is C i , tangent to the pressure surface PS of blade 1 and the suction surface SS of blade 2 at A i 、B i Point, chord length

[0024] Is the impeller flow channel width; chord length Numerical solution based on approximation method;

[0025] According to the above solution method, the width of the impeller flow channel at different positions is analyzed; when the impeller flow channel forms a constant acceleration flow channel, the maximum acceleration coefficient of the flow channel is evaluated.

[0026] and the maximum acceleration coefficient position Among them, V0 is the relative velocity per unit axial length of the flow channel inlet, V max is the relative velocity per unit axial length in the flow channel, α is the deflection angle of the velocity position in the flow channel, is the deflection angle of the maximum velocity position in the flow channel;

[0027] Adjust the b<0 value given in step 3) according to the above analysis results: If it is determined that the impeller flow channel does not constitute a constant velocity or a constant acceleration flow channel, adjust the value of b until a blade profile with a constant velocity blade channel or a constant acceleration blade channel is obtained.

[0028] Furthermore, in step 5), the design verification constraint module obtains the performance parameters of the designed fan through numerical simulation methods and experimental tests, wherein the numerical simulation method includes establishing a turbulence model, and the performance parameters include fan air volume, fan total pressure and total pressure efficiency.

[0029] As another aspect of the present application, a design system for a multi-blade centrifugal fan blade profile and impeller system is disclosed, which is applied to the design method for the multi-blade centrifugal fan blade profile and impeller system, and comprises:

[0030] The impeller parameter selection module inputs the design target parameters, selects appropriate impeller basic structural parameters based on the existing fan database and relevant design experience, generates a basic single arc blade structure, and performs preliminary performance verification;

[0031] The blade profile design module generates a blade profile that constructs a logarithmic spiral based on the basic structural parameters of the blade and the given blade shrinkage and expansion ratio;

[0032] The impeller flow channel calculation module generates the impeller flow channel geometry based on the generated blade profile and the given blade thickness and number of blades. It numerically calculates the change in the radius of the tangent circle on the surfaces of two adjacent blades and determines the acceleration and deceleration of the flow channel, the maximum acceleration coefficient, and the location of the maximum acceleration coefficient.

[0033] The 3D structure generation module automatically generates a 3D model of the impeller given the span length of the blades, and automatically assembles the 3D geometric models of the collector, volute, and volute tongue into a complete 3D solid model.

[0034] The fan performance test module obtains the performance parameters of the designed fan through numerical simulation methods and experimental tests.

[0035] Furthermore, the three-dimensional structure generation module can output the three-dimensional solid model as a two-dimensional CAD model or extract the fluid domain.

[0036] Furthermore, the numerical simulation method includes extracting the fluid domain, dividing the fluid domain and the rotation domain and extending the inlet and outlet, meshing, defining domain properties, medium properties and boundary conditions, adopting a turbulence model for numerical simulation calculations, and recording and analyzing relevant performance parameters.

[0037] The benefits of the present invention lie in that, under the premise of given basic structural parameters of the impeller, the blade profile designed by the logarithmic spiral can control the curvature of the blade to change uniformly with the outlet direction, thereby improving the uniformity and stability of the airflow; by changing the relevant parameters of the logarithmic spiral, the changing trend of the impeller flow channel width can be easily changed, thereby realizing more complex fluid control, reducing flow separation and secondary flow caused by unreasonable blade channel design, and improving the aerodynamic performance of the impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings constituting a part of this application are used to provide a further understanding of this application and make other features, purposes and advantages of this application more apparent. The drawings and descriptions of the exemplary embodiments of this application are used to explain this application and do not constitute an improper limitation on this application.

[0039] In addition, throughout the drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and that the elements and components are not necessarily drawn to scale.

[0040] In the attached figure:

[0041] Figure 1 A schematic diagram of the steps of a method for designing a blade profile and an impeller system for a multi-blade centrifugal fan provided in Example 1 of the present invention;

[0042] Figure 2 A schematic diagram of the centerline structure of the blade profile in the design method provided in Example 1 of the present invention;

[0043] Figure 3 This is a schematic structural diagram of the numerical solution of the impeller flow channel tangent circle using the approximation method in the design method provided in Example 1 of the present invention;

[0044] Figure 4 A schematic diagram of the steps for calculating the impeller flow channel width in the design method provided in Example 1 of the present invention;

[0045] Figure 5 Schematic diagram of the impeller flow channel widths before and after optimization obtained by adjusting b in the design method provided in Example 1 of the present invention;

[0046] Figure 6 A schematic diagram of the structure of a multi-blade centrifugal fan blade profile and impeller system design system provided in Example 2 of the present invention;

[0047] Figure 7 Schematic diagram of optimized flow field characteristics of front and rear blades in the numerical simulation method provided in Example 2 of the present invention;

[0048] Figure 8 This is a schematic diagram of the fan performance data curve before and after optimization in the design example provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0049] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are for illustrative purposes only and are not intended to limit the scope of protection of the present disclosure.

[0050] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other.

[0051] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0052] It should be noted that the modifications of "one" and "multiple" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, they should be understood as "one or more".

[0053] The names of the messages or information exchanged between multiple devices in the embodiments of the present disclosure are only used for illustrative purposes and are not used to limit the scope of these messages or information.

[0054] The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0055] like Figure 1 As shown, a design method for a blade profile and an impeller system of a multi-blade centrifugal fan includes:

[0056] S1. Given the target parameters of the multi-blade centrifugal fan corresponding to the impeller to be designed: Determine the target aerodynamic performance parameters of the multi-blade centrifugal fan based on experience, a model library, and design requirements.

[0057] The aerodynamic performance parameters include flow rate, total pressure, shaft power, and total pressure efficiency; the basic structural parameters of the multi-blade centrifugal fan impeller include the impeller inner diameter D1, impeller outer diameter D2, inlet angle β 1A , outlet angle β 2A , number of blades Z, blade thickness d.

[0058] S2. Generate basic single arc blade profile and check: Generate single arc blade profile based on basic impeller structural parameters to obtain initial design impeller. Preliminary evaluation of aerodynamic performance, check whether the initial impeller performance constructed by the selected parameters reaches 80% to 90% of the target parameters. The single arc blade profile parameters generated include: arc center (x c ,y c ) and arc radius R k , its specific geometric relationship is:

[0059]

[0060] x c =R k sin(β 2A ),y c =D2 / 2+R k cos(β 2A ).

[0061] After obtaining the single arc blade profile, a preliminary evaluation of the aerodynamic performance is conducted: the aerodynamic performance is tested. When the aerodynamic performance is far below the requirements, the basic structural parameters of the impeller are readjusted to bring the aerodynamic performance close to the target.

[0062] S3. Construct a logarithmic spiral blade profile: Specify the profile shrinkage rate b to generate a logarithmic spiral: Based on the specified five parameters and a single arc as the initial solution, a set of equations can be constructed and numerically solved to obtain the initial radius a of the logarithmic spiral, the offset coordinates (x s ,y s ) and the starting and ending angles θ1 and θ2 to obtain the blade profile.

[0063] The corresponding blade profile centerline structure is as follows Figure 2 As shown, the parameters a,x of the logarithmic spiral are s ,y s It can be determined by numerically solving the following system of equations:

[0064]

[0065] Let the initial values of a, θ1, θ2 be R k ,π / 2,π, numerically solve the above equation to obtain the numerical solution. Among them, θ1 and θ2 are the parameters of the intersection of the logarithmic spiral with the inner diameter circle and the outer diameter circle, so x s ,y s The results are as follows:

[0066]

[0067] S4. Determine whether the impeller channel is reasonable: Calculate the width of the impeller channel and modify the blade profile to obtain an impeller with a constant velocity channel or a constant acceleration channel. Based on step 2), the width of the impeller channel formed between the pressure and suction surfaces of two adjacent blades can be calculated by combining the number of blades Z and the blade thickness d. By varying b, the profile is adjusted to contract inward or expand outward, and at what rate, thereby changing the width of the impeller channel.

[0068] like Figure 3 As shown in the figure, the definition of the impeller flow channel width and the schematic diagram of the approximation method numerical solution are as follows:

[0069] For a certain position i in the blade flow channel, the center of the tangent circle is C i , tangent to the pressure surface PS of blade 1 and the suction surface SS of blade 2 at A i 、B i point, then the chord length Is the impeller flow channel width. To find this tangent circle C i , it is necessary to make multiple tangent circles C on the SS surface ij, until it is confirmed that this tangent circle is also tangent to the PS surface.

[0070] The above chord length The Python program is used for numerical solution. The specific process is as follows Figure 4 As shown:

[0071] ---

[0072] flowchart TD

[0073] A0("Start")-->A1["Parameter theta_Ai of the curve PS corresponding to the given tangent point Ai"]

[0074] A1-->A2["Calculate the coordinates of point Ai based on the equation of curve PS"]

[0075] A2-->A3["Draw a perpendicular line through point Ai"]

[0076] A3-->B1["Assign an initial value to R_ij"]

[0077] B1-->C1["Draw a circle Cij with radius R_ij on the perpendicular line and tangent to point Ai"]

[0078] C1-->C2{"Calculate the number of intersections between circle Ci and the corresponding curve PP"}

[0079] C2--The number of intersection points is 0-->B2["Increase the value of R_ij"]

[0080] C2--The number of intersection points is 1-->F1["The radius of the tangent circle R_i=R_ij"]

[0081] C2--Number of intersection points is 2-->D1{"Calculate the distance between two intersection points"}

[0082] D1--distance d>e-->B3["reduce the value of R_ij"]

[0083] D1--distance d <e-->F1

[0084] B2-->C1

[0085] B3-->C1

[0086] F1-->F2["Calculate the coordinates of the intersection point Bi"]

[0087] F2-->F3 ["Calculate the chord length of AiBi"]

[0088] F3-->G ("End")

[0089] Here, e is the minimum value defined by the program, usually e=1e-6.

[0090] Evaluate the change in impeller channel width using the aforementioned solution. If the impeller channel is determined not to constitute a constant velocity or constant acceleration channel, adjust the value of b until a blade profile with a constant velocity or constant acceleration channel is achieved. Specifically, when b < 0, the generated blade profile contracts inward, causing the curvature of the profile to decrease linearly from the starting point to the ending point, thereby reducing the width of the impeller channel outlet and enhancing the acceleration effect of the channel. A smaller b results in a greater enhancement, and vice versa.

[0091] like Figure 5 As shown in the figure, when the shrinkage rate b = 0, that is, the single arc blade profile adopted by the traditional design method, the speed gradually decreases at 0<α<0.2, and the speed gradually increases at 0.2<α<1, forming an impeller blade path that first decelerates and then accelerates; while the logarithmic spiral designed with the parameter b = -1.0 can cause the blade profile to shift at the inlet, thereby forming an impeller blade path with an accelerating flow channel.

[0092] In addition, the maximum acceleration factor and the maximum acceleration factor position are defined as follows:

[0093]

[0094] Among them, V0 is the relative velocity per unit axial length of the flow channel inlet, V max is the relative velocity per unit axial length in the flow channel, α is the deflection angle of the velocity position in the flow channel, is the deflection angle of the maximum velocity position in the flow channel.

[0095] Depend on Figure 5 It can be seen that compared with the single arc blade profile adopted by the traditional design method, the maximum acceleration coefficient is 0.41, while the maximum acceleration coefficient of the logarithmic spiral designed under the b=-1.0 parameter is 0.71.

[0096] S5. Verify the constraints: Check whether the flow and pressure constraints of the fan design meet the design requirements. When the constraints meet the design requirements, the design of the multi-blade centrifugal fan impeller system is completed. Otherwise, adjust the basic structural parameters of the impeller or readjust the b value.

[0097] The design verification constraint condition module refers to obtaining the performance parameters of the designed fan through numerical simulation methods and experimental tests, wherein the numerical simulation method includes establishing a turbulence model, and the performance parameters include fan air volume, fan total pressure and total pressure efficiency.

[0098] Furthermore, the numerical simulation method comprises the following steps:

[0099] a. Establish a three-dimensional solid model that matches the physical model, extract the fluid domain, and divide the fluid domain and rotation domain;

[0100] b. Perform mesh division. Use polyhedron mesh for volume mesh and adopt boundary layer mesh encryption for dynamic-static coupling area and near wall surface.

[0101] c. Import fluid calculation software and define domain properties, medium properties and boundary conditions;

[0102] d. Using the RNG ke turbulence model, the momentum equation is discretized in second order, and the turbulence equation is discretized in first order;

[0103] e. Start numerical simulation calculations, monitor key physical parameters, and determine whether the calculations have converged;

[0104] f. After the calculation converges, check the result file, record the inlet and outlet flow, pressure, impeller torque and other data, and convert them into fan air volume, fan total pressure, shaft power and total pressure efficiency data;

[0105] g. Complete the performance calculation under all working conditions and obtain the fan performance parameters under all working conditions.

[0106] As another aspect of the present application, a design system for a multi-blade centrifugal fan blade profile and impeller system is also disclosed, such as Figure 6 As shown, it includes: impeller parameter selection module, blade profile design module, impeller flow channel calculation module, three-dimensional structure generation module and fan performance inspection module.

[0107] The impeller parameter selection module inputs the design target parameters, selects appropriate impeller basic structural parameters based on the existing fan database and relevant design experience, generates a basic single arc blade structure, and performs preliminary performance verification;

[0108] The blade profile design module generates a blade profile that constructs a logarithmic spiral according to the basic structural parameters of the blade and a given blade shrinkage / expansion ratio;

[0109] The impeller flow channel calculation module generates the impeller flow channel geometry according to the generated blade profile and the given blade thickness and number of blades, numerically calculates the change in the radius of the tangent circle on the surfaces of two adjacent blades, and determines the acceleration and deceleration of the flow channel, the maximum acceleration coefficient, and the position of the maximum acceleration coefficient;

[0110] The three-dimensional structure generation module automatically generates a three-dimensional model of the impeller given the span-wise length of the blades, and automatically assembles a complete three-dimensional solid model based on the existing three-dimensional geometric models of the collector, volute, and volute tongue. Furthermore, the three-dimensional solid model can be output as a two-dimensional CAD model for blanking, manufacturing, and assembly to produce test prototypes. Furthermore, the three-dimensional solid model can be used to extract the fluid domain, divide the fluid domain and the rotation domain, and extend the inlet and outlet for three-dimensional fluid simulation.

[0111] The numerical simulation method includes extracting the fluid domain, dividing the fluid domain and the rotation domain and extending the inlet and outlet, meshing, defining domain properties, medium properties and boundary conditions, adopting a turbulence model to perform numerical simulation calculations, and recording and analyzing relevant performance parameters.

[0112] In this embodiment, when performing numerical simulation calculations, the incompressible adiabatic steady flow assumption is adopted for the multi-blade centrifugal fan, and a multiple reference frame model is used, that is, a stationary coordinate system is used for the stationary domain where the volute and volute tongue are located, and a rotating coordinate system with a constant speed is used for the rotating domain where the impeller is located. During the calculation, the RNG ke turbulence model, the second-order upwind scheme, and the SIMPLEC algorithm are used to discretize the equations and perform fluid simulation on the fan. Figure 7 As shown in Figure 2, the fluid simulation results are post-processed to obtain the flow field characteristic distribution of the fan.

[0113] As another aspect of the present application, an example of designing a high-efficiency multi-blade centrifugal fan is provided, and the feasibility of the design method of the present invention is verified by numerical calculation.

[0114] This method was used to optimize a multi-blade centrifugal fan design under design condition Q. To achieve low noise performance, the fan adopted a conservative forward outlet angle design. While this achieved the desired reduction in aerodynamic noise, it resulted in a significant pressure drop in the high-flow area, impacting actual operation. Using this fan as a model, this method was iterated repeatedly. While maintaining the basic structural parameters of the impeller, a blade profile was designed that met the design requirements for aerodynamic performance while maintaining low noise levels.

[0115] After the fan is optimized and designed using this method, the profile is improved, and the total pressure in the large air volume area is increased, and the pressure drop decreases as the air volume increases. Figure 8 As shown, this method is feasible.

[0116] This paper deeply analyzes the influence of the shrinkage and expansion rate of the blade profile on the impeller blade path and the fan performance, and reveals the corresponding change rules:

[0117] The smaller the shrinkage rate b of the blade profile is, the easier it is to form an impeller blade passage with an accelerated flow path, and vice versa;

[0118] Properly improving the flow acceleration effect of the impeller blade channel can increase the wind pressure of the fan under the design working conditions, thereby improving the performance and total pressure efficiency of the fan. In this case, the shrinkage rate of the blade profile should be appropriately reduced;

[0119] The acceleration flow channel of the impeller blade channel cannot be increased indefinitely, otherwise it will affect the maximum air volume of the fan, thereby reducing the effective operating range of the fan. In this case, the contraction and expansion rate of the blade profile should be appropriately increased.

[0120] The present invention first determines the basic structural parameters of the impeller, then designs and draws the logarithmic spiral blade profile; by changing the shrinkage and expansion rate b of the blade profile, a suitable impeller blade path is formed; then, it is assembled with other components such as the volute and collector into a complete three-dimensional solid model, and the fan performance results are verified through fluid simulation.

[0121] The above description is only an illustration of some preferred embodiments of the present disclosure and the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure.

Claims

1. A method for designing a blade profile and an impeller system for a multi-blade centrifugal fan, characterized by: The following steps are involved: 1) Preliminary selection of impeller basic structural parameters based on target parameters: Determine the target aerodynamic performance parameters of the multi-blade centrifugal fan based on experience and design requirements; According to the established target parameters, select appropriate basic structural parameters of the impeller based on the model library, design experience, etc.; 2) Generate and verify a basic single-arc blade profile: Generate a single-arc blade profile based on the basic structural parameters of the impeller to obtain the initial design impeller; preliminarily evaluate the aerodynamic performance and verify whether the initial impeller performance constructed with the selected parameters reaches 80% to 90% of the target parameters; 3) Construct a logarithmic spiral blade profile: Specify the profile shrinkage rate b to generate a logarithmic spiral: Based on the specified five parameters and a single arc as the initial solution, a set of equations is constructed and numerically solved to obtain the initial radius a of the logarithmic spiral, the offset coordinates (x s ,y s ) and the starting and ending angles θ1 and θ2, thereby obtaining the blade profile; 4) Determine whether the impeller channel is reasonable: calculate the width of the impeller channel, modify the blade profile, and obtain an impeller with a constant velocity channel or a constant acceleration channel; based on step 3), combine the two parameters of blade number Z and blade thickness d to calculate the width of the impeller channel formed between the pressure surface and suction surface of two adjacent blades; change b to adjust the profile to shrink inward or expand outward and its rate, thereby changing the width of the impeller channel; 5) Verify the constraints: Check whether the flow and pressure constraints of the fan design meet the design requirements. When the constraints meet the design requirements, the design of the multi-blade centrifugal fan impeller system is completed. Otherwise, adjust the basic structural parameters of the impeller or readjust the b value.

2. The method for designing a multi-blade centrifugal fan blade profile and impeller system according to claim 1, characterized in that: In step 1), the aerodynamic performance parameters include flow rate, total pressure, shaft power, and total pressure efficiency; the basic structural parameters of the multi-blade centrifugal fan impeller include the impeller inner diameter D1, the impeller outer diameter D2, the inlet angle β 1A , outlet angle β 2A , number of blades Z, blade thickness d.

3. The method for designing a blade profile and an impeller system for a multi-blade centrifugal fan according to claim 1, wherein: In step 2), the single arc blade profile is obtained, including the arc center (x c ,y c ) and arc radius R k , its specific geometric relationship is: x c =R k sin(β 2A ),y c =D2 / 2+R k cos(β 2A )。 4. The method for designing a multi-blade centrifugal fan blade profile and impeller system according to claim 1, characterized in that: After step 2), the method further includes the following steps: Evaluate aerodynamic performance: Check aerodynamic performance. When the aerodynamic performance is far below the requirement, readjust the basic structural parameters of the impeller to make the aerodynamic performance reach 80% to 90% of the target parameters.

5. The method for designing a blade profile and an impeller system for a multi-blade centrifugal fan according to claim 1, characterized in that: In step 3), the parameters a,x of the logarithmic spiral are s ,y s Determined by numerically solving the following system of equations: Let the initial values of a, θ1, θ2 be R k ,π / 2,π, numerically solve the above equation to obtain the numerical solution; where θ1 and θ2 are the parameters of the intersection of the logarithmic spiral with the inner diameter circle and the outer diameter circle, so x s ,y s The results are as follows: x2=ae bθ2 cos(θ2)+x s ,y2=ae bθ2 sin(θ2)+y s 。 6. The method for designing a blade profile and an impeller system for a multi-blade centrifugal fan according to claim 1, wherein: In step 4), the definition and solution method of the impeller channel width are: For a certain position i in the blade flow channel, the center of the tangent circle is C i , tangent to the pressure surface PS of blade 1 and the suction surface SS of blade 2 at A i 、B i Point, chord length That is the impeller flow channel width; chord length Numerical solution based on approximation method; According to the above solution method, the width of the impeller flow channel at different positions is analyzed; when the impeller flow channel forms a constant acceleration flow channel, the maximum acceleration coefficient of the flow channel is evaluated. and the maximum acceleration coefficient position Among them, V0 is the relative velocity per unit axial length of the flow channel inlet, V max is the relative velocity per unit axial length in the flow channel, α is the deflection angle of the velocity position in the flow channel, and α Vmax is the deflection angle of the maximum velocity position in the flow channel; Adjust the b<0 value given in step 3) according to the above analysis results: If it is determined that the impeller flow channel does not constitute a constant velocity or a constant acceleration flow channel, adjust the value of b until a blade profile with a constant velocity blade channel or a constant acceleration blade channel is obtained.

7. The method for designing a blade profile and an impeller system for a multi-blade centrifugal fan according to claim 1, characterized in that: In step 5), the design verification constraint condition module obtains the performance parameters of the designed fan through numerical simulation methods and experimental tests, wherein the numerical simulation method includes establishing a turbulence model, and the performance parameters include fan air volume, fan total pressure and total pressure efficiency.

8. A system for designing a multi-blade centrifugal fan blade profile and impeller system, applied to the method for designing a multi-blade centrifugal fan blade profile and impeller system according to any one of claims 1 to 7, characterized in that: include: The impeller parameter selection module inputs the target design parameters, selects appropriate basic impeller structural parameters based on the existing fan database and relevant design experience, generates a basic single-arc blade structure, and performs preliminary performance verification; The blade profile design module generates a blade profile that constructs a logarithmic spiral based on the basic structural parameters of the blade and the given blade shrinkage and expansion ratio; The impeller flow channel calculation module generates the impeller flow channel geometry based on the generated blade profile and the given blade thickness and number of blades. It numerically calculates the change in the radius of the tangent circle on the surfaces of two adjacent blades and determines the acceleration and deceleration of the flow channel, the maximum acceleration coefficient, and the location of the maximum acceleration coefficient. The 3D structure generation module automatically generates a 3D model of the impeller given the span length of the blades, and automatically assembles the 3D geometric models of the collector, volute, and volute tongue into a complete 3D solid model. The fan performance test module obtains the performance parameters of the designed fan through numerical simulation methods and experimental tests.

9. The design system for blade profiles and impeller systems of a multi-blade centrifugal fan according to claim 8, characterized in that: The three-dimensional structure generation module can output the three-dimensional solid model as a two-dimensional CAD model or extract the fluid domain.

10. The design system for blade profiles and impeller systems of a multi-blade centrifugal fan according to claim 8, characterized in that: The numerical simulation method includes extracting the fluid domain, dividing the fluid domain and the rotation domain and extending the inlet and outlet, meshing, defining domain properties, medium properties and boundary conditions, adopting a turbulence model to perform numerical simulation calculations, and recording and analyzing relevant performance parameters.

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