Centrifugal fan binary blade molded line design method and system based on variable deceleration distribution method

Abstract

The invention discloses a centrifugal fan binary blade molded line design method and system based on a variable deceleration distribution method. The method comprises the steps that the relative speed of an inlet and an outlet is determined according to fan parameters; giving a relative velocity distribution equation; solving equations and constraint conditions are supplemented; determining a cubic polynomial; obtaining relative speeds at different radiuses; obtaining airflow angles at different radiuses; obtaining a molded line coordinate; and drawing a blade molded line. The method does not depend on the experience of optimization designers, the optimization cost is reduced, and the fan efficiency is improved while the high total pressure is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of centrifugal fan blade profile design, and in particular relates to a centrifugal fan binary blade profile design method and system based on a variable speed distribution method. Background Art

[0002] Centrifugal fans, widely used in the energy, chemical, and other industries, enjoy a significant domestic market. However, due to the widespread inefficiency of earlier fan designs, they often consume significant amounts of electricity. A centrifugal fan generally consists of an impeller, volute, and collector. The impeller, as the primary aerodynamic component, has the greatest impact on centrifugal fan performance, and the blade profile is a key factor influencing performance.

[0003] At present, in order to facilitate processing and manufacturing, centrifugal fans usually use plate blades. The main blade design methods are double arc blades and constant deceleration blades. However, both blades have certain limitations. The double arc blade profile has the characteristics of flexible profile and higher total pressure, but it does not start from the aerodynamic point of view, so the efficiency is often low. The constant deceleration blade profile, from the aerodynamic point of view, controls the relative speed in a linear decreasing form, so that the designed blade profile is extended to a certain extent, the gas flow in the blade channel is more sufficient, and the efficiency is generally higher, but it will cause a large drop in total pressure, and sometimes it is difficult to meet the original design total pressure of the fan. Moreover, due to the fixed relative velocity distribution, the blade profile is single and cannot be changed flexibly. If the design total pressure cannot be achieved after optimization, it is difficult to change. In practical applications, there is a lack of a binary blade profile optimization design method that takes into account both high efficiency and high total pressure.

[0004] Traditional blade optimization design methods rely heavily on the experience of optimization designers and require repeated optimization followed by experimentation, resulting in low efficiency, high optimization costs, and failure to produce the optimal blade. Therefore, it is very important to adopt a simple, feasible, and experience-independent high-performance wind turbine blade design method. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems in the current technology and provide a centrifugal fan binary blade profile design method and system based on the variable deceleration distribution method, which is independent of the experience of the optimization designer, reduces the optimization cost, ensures a higher total pressure and improves the fan efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method includes:

[0008] 1) Calculate the fan blade inlet and outlet meridian velocity c based on the original fan impeller structural parameters1m and c 2m Size, then solve the size of the inlet and outlet relative speeds w1 and w2;

[0009] 2) Determine the distribution equation of the relative velocity along the relative position of the blade: The distribution equations of the relative velocity w along the relative position r of the blade are respectively defined as a cubic polynomial and a linear polynomial;

[0010] 3) When the relative speeds of the inlet and outlet are known according to the cubic polynomial, the four equations required by the cubic polynomial are supplemented by setting the intersection position r0 of the cubic polynomial and the linear polynomial and the slope k0 at the intersection;

[0011] 4) Based on the four solved equations, in order to ensure the rationality of the distribution of relative velocity, two constraints are added to the slope of the inlet and outlet cubic polynomials. After the constraints are met, the cubic polynomial is obtained;

[0012] 5) According to the cubic polynomial, the relative velocity w of the blades at different relative positions from the inlet to the outlet is obtained. The airflow angle β at different relative positions of the blades is calculated based on the relative velocity w, and the corresponding center angle is calculated based on the airflow angle β. Then, the coordinate points of the blade profile are obtained, and the coordinate points are connected to obtain the blade profile;

[0013] 6) Perform numerical simulation of the whole machine based on the obtained blade profile, and preliminarily compare the performance differences of different blade profiles obtained by combining a small number of different intersection positions r0 and slopes k0 at the intersection points;

[0014] 7) Create sample points based on the intersection position r0 and the slope k0 at the intersection, obtain the total pressure and efficiency of each sample by combining the whole machine numerical simulation, and complete the construction of the Kriging proxy model;

[0015] 8) Taking the efficiency predicted by the Kriging surrogate model as the fitness function and the fan design total pressure as the constraint condition, the genetic algorithm is used to optimize the two parameters of the intersection position r0 and the slope k0 at the intersection to obtain the optimal blade profile.

[0016] A further improvement of the present invention is that in step 1), the blade inlet and outlet meridian velocity c is calculated based on the original fan impeller structural parameters. 1m and c 2m , the formula used is:

[0017]

[0018] Where Q is the volume flow rate, D1 is the blade inlet diameter, D2 is the impeller outer diameter, b1 is the blade inlet width, b2 is the blade outlet width, τ1 is the inlet blockage coefficient, τ2 is the outlet blockage coefficient, and μ is the airflow filling coefficient;

[0019] The formula used for the blade inlet and outlet blocking coefficients τ1 and τ2 is:

[0020]

[0021] Where z is the number of blades, δ1 is the blade inlet thickness, δ2 is the blade outlet thickness, β1 is the blade inlet installation angle, and β2 is the blade outlet installation angle;

[0022] According to the blade inlet and outlet meridian velocity c 1m and c 2m The formula used to calculate the relative speeds w1 and w2 of the blade inlet and outlet is:

[0023]

[0024] A further improvement of the present invention is that, in step 2), the distribution equations of the relative velocity w along the relative position r of the blade are respectively specified as a cubic polynomial and a linear polynomial, and the formula used is:

[0025] w(r)=f(r)=A1r 3 +A2r 2 +A3r+A4 (7)

[0026] Among them, A1, A2, A3, and A4 are unknowns of the cubic polynomial. To ensure that they are not affected by physical scale and to facilitate universal design analysis, the radius is dimensionless. Here, r is the relative position, and the definition formula used is:

[0027]

[0028] Among them, r' is the specific radius value of a point from the blade inlet to the blade outlet, r in is the specific value of the blade inlet radius, r out is the specific radius value of the blade outlet;

[0029] Solving the above cubic polynomial requires four equations. Since the relative velocity at the blade inlet and outlet is known, two equations need to be supplemented. Here, the relative velocity distribution equation is additionally specified as a linear polynomial. The formula used is:

[0030] w(r)=f(r)=kr+c (9)

[0031] Among them, k and c are unknown variables of the first-order polynomial, which can be directly obtained by substituting the inlet and outlet relative velocities w1 and w2.

[0032] A further improvement of the present invention is that in step 3), when the relative speeds of the inlet and outlet are known according to the cubic polynomial, the intersection position r0 of the cubic polynomial and the linear polynomial and the slope k0 at the intersection are set to complete the four equations required for the cubic polynomial:

[0033] A4=w1 (10)

[0034] A1+A2+A3+A4=w2 (11)

[0035] A1r0 3 +A2r0 2 +A3r0+A4=kr0+c (12)

[0036]

[0037] Among them, w1 is the relative velocity of the blade inlet, and w2 is the relative velocity of the blade outlet.

[0038] A further improvement of the present invention is that, in step 4), based on the four solved equations, two constraints on the slopes of the inlet and outlet cubic polynomials are added to ensure the rationality of the distribution of the relative velocity. After the constraints are satisfied, a cubic polynomial is obtained, wherein the constraints are:

[0039]

[0040] Where k1 is the slope of the cubic polynomial at the inlet, and k2 is the slope of the cubic polynomial at the outlet.

[0041] A further improvement of the present invention is that, in step 5), the airflow angle β at different blade relative positions is calculated based on the obtained relative speed, and the formula used is:

[0042]

[0043] Calculate the corresponding central angle according to the airflow angle β The size of , the formula used is:

[0044]

[0045] in, is the central angle.

[0046] A further improvement of the present invention is that in step 6), in the numerical simulation of the whole machine, a three-dimensional aerodynamic model is created by UG software, the impeller mesh is divided by Turbogrid software, the collector and volute mesh are divided by ICEM software, and the mesh is imported into CFX software for numerical simulation of the whole machine to obtain the total pressure and efficiency of the fan.

[0047] A further improvement of the present invention is that, in step 7), the Latin hypercube sampling method is used to create sample points for the intersection position r0 and the slope k0 at the intersection. The value range of the intersection position r0 is 0.2 to 0.8, and the value range of the slope k0 at the intersection is -25.4 to -30.0, which is determined by the constraints of the slopes k1 and k2 at the inlet and outlet of the cubic polynomial. The total pressure and efficiency of different sample points are obtained through numerical simulation of the whole machine and used as training data to complete the construction of the kriging proxy model.

[0048] A further improvement of the present invention is that, in step 8), the constraint condition of the genetic algorithm is the original wind turbine design full pressure of 4961Pa, the population size is set to 200, and the maximum iteration number is 100.

[0049] The centrifugal fan two-dimensional blade profile design system based on the variable speed distribution method includes:

[0050] The first solution module calculates the fan blade inlet and outlet meridian velocity c according to the original fan impeller structural parameters 1m and c 2m Size, then solve the size of the inlet and outlet relative speeds w1 and w2;

[0051] The distribution equation determination module determines the distribution equation of the relative speed along the relative position of the blade: the distribution equations of the relative speed w along the relative position r of the blade are respectively specified as a cubic polynomial and a linear polynomial;

[0052] The parameter setting module, based on the cubic polynomial, when the relative speed of the inlet and outlet is known, sets the intersection position r0 of the cubic polynomial and the linear polynomial and the slope k0 at the intersection, thereby completing the four equations required by the cubic polynomial;

[0053] The constraint condition adding module adds two constraint conditions for the slope of the inlet and outlet cubic polynomials based on the four solved equations to ensure the rationality of the distribution of relative velocity. After the constraint conditions are met, the cubic polynomial is obtained.

[0054] The second solution module obtains the relative speed w of the blades at different relative positions from the inlet to the outlet according to the cubic polynomial, calculates the airflow angle β at different blade relative positions according to the relative speed w, and then calculates the corresponding center angle according to the airflow angle β Then, the coordinate points of the blade profile are obtained, and the coordinate points are connected to obtain the blade profile;

[0055] The performance difference analysis module performs numerical simulation of the entire machine based on the obtained blade profile, and preliminarily compares the performance differences of different blade profiles obtained by combining a small number of different intersection positions r0 and slopes k0 at the intersection points;

[0056] The proxy model construction module creates sample points based on the intersection position r0 and the slope k0 at the intersection, and combines the full machine numerical simulation to obtain the total pressure and efficiency of each sample to complete the construction of the Kriging proxy model;

[0057] The optimal blade profile optimization module uses the efficiency predicted by the Kriging agent model as the fitness function and the fan design total pressure as the constraint condition. It uses the genetic algorithm to optimize the two parameters of the intersection position r0 and the slope k0 at the intersection to obtain the optimal blade profile.

[0058] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0059] The present invention proposes a blade profile design method for controlling the relative velocity distribution from an aerodynamic perspective. By changing the two control parameters of the relative velocity distribution, the blade profile can be freely transformed, which is highly flexible and has a wide range of applications. The two key parameters for controlling the relative velocity distribution are sampled, and the corresponding total pressure and efficiency are obtained based on the numerical simulation of the whole machine to construct a proxy model. The constructed proxy model is combined with a genetic algorithm to complete the search for the optimal parameters, thereby obtaining a high-performance blade profile. The blade profile designed by the present invention can fully tap the aerodynamic performance potential of the centrifugal fan and achieve higher efficiency. Compared with the traditional empirical design method, it no longer relies on the experience of the designer and reduces the repeated optimization process, shortens the optimization cycle and cost, is easy to implement, and is suitable for actual promotion and application in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0061] Figure 1 It is a schematic diagram of the design process of the present invention;

[0062] Figure 2 is the distribution diagram of the two relative velocities along the relative position of the blade;

[0063] Figure 3 Define the graph for the supplementary equations of the variable deceleration distribution form;

[0064] Figure 4 Schematic diagram of the restriction conditions for variable deceleration distribution;

[0065] Figure 5 Different profile diagrams obtained for variable deceleration distribution forms;

[0066] Figure 6 Basic flow chart for blade optimization of the present invention;

[0067] Figure 7 This is a structural block diagram of the centrifugal fan binary blade profile design system based on the variable speed distribution method of the present invention. DETAILED DESCRIPTION

[0068] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0069] In the description of the present invention, it is to be understood that when used in this specification and the appended claims, the terms “include” and “comprise” indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0070] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0071] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0072] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0073] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0074] Example 1

[0075] The present invention provides a centrifugal fan two-dimensional blade profile design method based on a variable speed distribution method, comprising:

[0076] Calculate the blade inlet and outlet meridian velocity c based on the original fan impeller structural parameters 1m and c 2m , the formula used is:

[0077]

[0078] Where Q is the volume flow rate, D1 is the blade inlet diameter, D2 is the impeller outer diameter, b1 is the blade inlet width, b2 is the blade outlet width, τ1 is the inlet blockage coefficient, τ2 is the outlet blockage coefficient, and μ is the airflow filling coefficient;

[0079] The formula used for the blade inlet and outlet blocking coefficients τ1 and τ2 is:

[0080]

[0081] Where z is the number of blades, δ1 is the blade inlet thickness, δ2 is the blade outlet thickness, β1 is the blade inlet installation angle, and β2 is the blade outlet installation angle;

[0082] According to the blade inlet and outlet meridian velocity c 1m and c 2m The formula used to calculate the relative speeds w1 and w2 of the blade inlet and outlet is:

[0083]

[0084] The distribution equations of the relative velocity along the relative position of the blade are respectively a cubic polynomial and a linear polynomial, and the formulas used are:

[0085] w(r)=f(r)=A1r 3 +A2r 2 +A3r+A4 (7)

[0086] Among them, A1, A2, A3, and A4 are unknowns of the cubic polynomial. To ensure that they are not affected by physical scale and to facilitate universal design analysis, the radius is dimensionless. Here, r is the relative position, and the definition formula used is:

[0087]

[0088] Among them, r' is the specific radius value of a point from the blade inlet to the blade outlet, r in is the specific value of the blade inlet radius, r out is the specific radius value of the blade outlet.

[0089] Solving the above cubic polynomial requires four equations. Since the relative speeds at the blade inlet and outlet are known, two equations need to be supplemented. Here, the relative speed distribution equation is additionally specified as a linear polynomial. The relative speed distribution is plotted as follows: Figure 2 As shown, the formula used is:

[0090] w(r)f(r)=kr+c (9)

[0091] Among them, k and c are unknown variables of the first-order polynomial, which can be directly obtained by substituting the inlet and outlet relative velocities w1 and w2.

[0092] According to the above cubic polynomial, when the relative speed of the inlet and outlet is known, Figure 3 It can be seen that there is an intersection between the two velocity distribution forms. The intersection position r0 of the cubic polynomial and the linear polynomial is set. Generally speaking, the flow diffusion pressure at the inlet and outlet positions is very small, while the flow diffusion pressure in the middle area of ​​the blade is relatively large. Therefore, the slow decrease in the relative velocity of the blade inlet and outlet is beneficial to the airflow. Therefore, the intersection position r0 is taken in the range of 0.2 to 0.8. Secondly, the slope k0 at the intersection is set. Here, the slope of the cubic polynomial should be smaller than the slope of the linear polynomial, thereby completing the four equations required to solve the cubic polynomial. The four equations after completion are:

[0093] A4=w1(10)

[0094] A1+A2+A3+A4=w2(11)

[0095] A1r0 3 +A2r0 2 +A3r0+A4=kr0+c(12)

[0096]

[0097] Among them, w1 is the relative velocity of the blade inlet, and w2 is the relative velocity of the blade outlet.

[0098] Based on the above four solution equations, in order to ensure the rationality of the distribution of relative velocity, the lower limit of the slope k0 at the intersection is determined, and two constraints are added to the slope of the import and export cubic polynomials as follows: Figure 4 As shown, the import and export slopes of the cubic polynomial are guaranteed to be within a reasonable range, so that the relative speed always meets the requirement of decreasing along the relative position of the blade. The constraints are:

[0099]

[0100] Where k1 is the slope of the cubic polynomial at the inlet, and k2 is the slope of the cubic polynomial at the outlet.

[0101] By solving the above four equations and the constraints, we can confirm the specific values ​​of the four unknowns A1, A2, A3, and A4, and confirm whether the values ​​of the originally given intersection position r0 and the slope k0 at the intersection match. Then, we can determine the reasonable value range of the intersection slope, and the value range of the slope k0 at the intersection is -25.4 to -30.0. According to formula (3), the relative velocity w at different relative positions from the inlet to the outlet can be obtained. Based on the relative velocity, the airflow angle β at different relative positions can be calculated. The formula used is:

[0102]

[0103] According to the airflow angle β, the corresponding central angle can be calculated The size of , the formula used is:

[0104]

[0105] in, is the central angle.

[0106] The above formula is used to obtain the coordinate points of the blade profile at each relative position, and the blade profile is obtained by connecting the various coordinate points.

[0107] Different combinations of intersection positions and slopes at the intersection within a reasonable range determine different cubic polynomial relative velocity distributions and obtain different blade profiles. Three groups of intersection positions r0 and intersection slopes k0 are initially selected for blade performance comparison. The three groups of blade profiles are as follows: Figure 5 As shown. The relative position r0 of the intersection of variable deceleration blade type A is 0.65, and the slope k0 at the intersection is -26.9. The relative position r0 of the intersection of variable deceleration blade type B is 0.44, and the slope k0 at the intersection is -29.3. The relative position r0 of the intersection of variable deceleration blade type C is 0.2, and the slope k0 at the intersection is -30. There are certain differences in the performance of different blade profiles designed within a reasonable range. A three-dimensional model of a low specific speed centrifugal fan (design total pressure is 4961Pa) is established for the different blade profiles obtained and the three-dimensional model is numerically simulated using CFX software. The blade performance obtained by combining the equal deceleration profile and some different intersection positions and slopes at the intersection is listed in the following table:

[0108] Blade profile Total pressure p / Pa Efficiency η / % Constant deceleration blade 4943.1 79.86 Variable speed blade type A 4987.9 80.28 Variable speed blade type B 5033.7 80.02 Variable speed blade C 5193.9 79.11

[0109] It can be seen that the overall efficiency of the fan blade performance initially obtained through this invention is basically consistent with that of the constant deceleration blade profile, and has the high efficiency of the constant deceleration blade profile. The use of a variable deceleration blade profile can better meet the design full pressure requirement of 4961Pa. The combination of different intersection positions and slopes at the intersection can produce blade profiles with diverse performance, better meeting more design needs, making fan blade design more flexible and efficient.

[0110] In order to obtain the optimal blade that meets the design total pressure, it is necessary to combine the agent model and genetic algorithm to further optimize. Figure 6 This is the basic flow chart of blade optimization in the present invention. Sample points are created according to the intersection position r0 and the slope k0 at the intersection. The Latin hypercube sampling method is used to create the sample points. The value range of the intersection position r0 is 0.2 to 0.8, and the value range of the slope k0 at the intersection is -25.4 to -30.0. It is determined by the constraints of the slopes k1 and k2 at the inlet and outlet of the cubic polynomial. The total pressure and efficiency of different sample points are obtained through numerical simulation of the whole machine and used as training data to complete the construction of the kriging proxy model.

[0111] The efficiency predicted by the surrogate model is used as the fitness function. To ensure that the optimized design full pressure meets the requirements, the fan design full pressure of 4961Pa is used as the constraint condition. The genetic algorithm is used to optimize the two parameters of the intersection position r0 and the slope k0 at the intersection. The population size is set to 200 and the maximum iteration generation is 100. In this way, the optimal variable speed blade profile is obtained. The relative position r0 of the intersection is 0.78, and the slope k0 at the intersection is -28.7. Numerical simulation calculations are performed. Finally, the calculated fan performance is listed in the following table:

[0112] Blade profile Total pressure p / Pa Efficiency η / % Constant deceleration blade 4943.1 79.86 Optimal blade shape 4983.0 80.47

[0113] It can be seen from the above calculation results that the blade design method of the present invention can ensure that the total pressure meets the design total pressure while fully utilizing the aerodynamic performance potential of the centrifugal fan to achieve higher efficiency. It no longer relies on the experience of designers and reduces the process of repeated optimization, shortening the optimization cycle and cost. It is easy to implement and suitable for actual promotion and application in engineering.

[0114] Example 2

[0115] like Figure 7 As shown, the centrifugal fan two-dimensional blade profile design system based on the variable deceleration distribution method provided by the present invention includes:

[0116] The first solution module calculates the fan blade inlet and outlet meridian velocity c according to the original fan impeller structural parameters 1m and c 2m Size, then solve the size of the inlet and outlet relative speeds w1 and w2;

[0117] The distribution equation determination module determines the distribution equation of the relative speed along the relative position of the blade: the distribution equations of the relative speed w along the relative position r of the blade are respectively specified as a cubic polynomial and a linear polynomial;

[0118] The parameter setting module, based on the cubic polynomial, when the relative speed of the inlet and outlet is known, sets the intersection position r0 of the cubic polynomial and the linear polynomial and the slope k0 at the intersection, thereby completing the four equations required by the cubic polynomial;

[0119] The constraint condition adding module adds two constraint conditions for the slope of the inlet and outlet cubic polynomials based on the four solved equations to ensure the rationality of the distribution of relative velocity. After the constraint conditions are met, the cubic polynomial is obtained.

[0120] The second solution module obtains the relative speed w of the blades at different relative positions from the inlet to the outlet according to the cubic polynomial, calculates the airflow angle β at different blade relative positions according to the relative speed w, and then calculates the corresponding central angle according to the airflow angle β Then, the coordinate points of the blade profile are obtained, and the coordinate points are connected to obtain the blade profile;

[0121] The performance difference analysis module performs numerical simulation of the entire machine based on the obtained blade profile, and preliminarily compares the performance differences of different blade profiles obtained by combining a small number of different intersection positions r0 and slopes k0 at the intersection points;

[0122] The proxy model construction module creates sample points based on the intersection position r0 and the slope k0 at the intersection, and combines the full machine numerical simulation to obtain the total pressure and efficiency of each sample to complete the construction of the Kriging proxy model;

[0123] The optimal blade profile optimization module uses the efficiency predicted by the Kriging agent model as the fitness function and the fan design total pressure as the constraint condition. It uses a genetic algorithm to optimize the two parameters of the intersection position r0 and the slope k0 at the intersection to obtain the optimal blade profile.

[0124] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all points of view, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and range of equivalents of the claims are included in the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0125] In addition, it should be understood that although this specification describes the embodiments, not every embodiment contains only one independent technical solution. This description is for clarity only. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for the purpose of illustrating the technical concept of the present invention and cannot be used to limit the scope of protection of the present invention. Any changes made based on the technical solution in accordance with the technical concept proposed by the present invention fall within the scope of protection of the claims of the present invention.

Claims

1. A centrifugal fan two-dimensional blade profile design method based on a variable speed distribution method, characterized in that: include: 1) Calculate the fan blade inlet and outlet meridian velocity c based on the original fan impeller structural parameters 1m and c 2m Size, then solve the size of the inlet and outlet relative speeds w1 and w2; 2) Determine the distribution equation of the relative velocity along the relative position of the blade: The distribution equations of the relative velocity w along the relative position r of the blade are respectively defined as a cubic polynomial and a linear polynomial; 3) When the relative speeds of the inlet and outlet are known according to the cubic polynomial, the four equations required by the cubic polynomial are supplemented by setting the intersection position r0 of the cubic polynomial and the linear polynomial and the slope k0 at the intersection; 4) Based on the four solved equations, in order to ensure the rationality of the distribution of relative velocity, two constraints are added to the slope of the inlet and outlet cubic polynomials. After the constraints are met, the cubic polynomial is obtained; 5) According to the cubic polynomial, the relative velocity w of the blades at different relative positions from the inlet to the outlet is obtained. The airflow angle β at different relative positions of the blades is calculated based on the relative velocity w, and the corresponding center angle is calculated based on the airflow angle β. Then, the coordinate points of the blade profile are obtained, and the coordinate points are connected to obtain the blade profile; 6) Perform numerical simulation of the whole machine based on the obtained blade profile, and preliminarily compare the performance differences of different blade profiles obtained by combining a small number of different intersection positions r0 and slopes k0 at the intersection points; 7) Create sample points based on the intersection position r0 and the slope k0 at the intersection, obtain the total pressure and efficiency of each sample by combining the whole machine numerical simulation, and complete the construction of the Kriging proxy model; 8) Taking the efficiency predicted by the Kriging surrogate model as the fitness function and the fan design total pressure as the constraint condition, the genetic algorithm is used to optimize the two parameters of the intersection position r0 and the slope k0 at the intersection to obtain the optimal blade profile.

2. The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method according to claim 1 is characterized in that: In step 1), the blade inlet and outlet meridian velocity c is calculated based on the original fan impeller structural parameters. 1m and c 2m , the formula used is: Where Q is the volume flow rate, D1 is the blade inlet diameter, D2 is the impeller outer diameter, b1 is the blade inlet width, b2 is the blade outlet width, τ1 is the inlet blockage coefficient, τ2 is the outlet blockage coefficient, and μ is the airflow filling coefficient; The formula used for the blade inlet and outlet blocking coefficients τ1 and τ2 is: Where z is the number of blades, δ1 is the blade inlet thickness, δ2 is the blade outlet thickness, β1 is the blade inlet installation angle, and β2 is the blade outlet installation angle; According to the blade inlet and outlet meridian velocity c 1m and c 2m The formula used to calculate the relative speeds w1 and w2 of the blade inlet and outlet is:

3. The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method according to claim 2 is characterized in that: In step 2), the distribution equations of the relative velocity w along the relative position r of the blade are respectively specified as a cubic polynomial and a linear polynomial, and the formulas used are: w(r)=f(r)=A1r 3 +A2r 2 +A3r+A4 (7) Among them, A1, A2, A3, and A4 are unknowns of the cubic polynomial. To ensure that they are not affected by physical scale and to facilitate universal design analysis, the radius is dimensionless. Here, r is the relative position, and the definition formula used is: Among them, r' is the specific radius value of a point from the blade inlet to the blade outlet, r in is the specific value of the blade inlet radius, r out is the specific radius value of the blade outlet; Solving the above cubic polynomial requires four equations. Since the relative velocity at the blade inlet and outlet is known, two equations need to be supplemented. Here, the relative velocity distribution equation is additionally specified as a linear polynomial. The formula used is: w(r)=f(r)=kr+c (9) Among them, k and c are unknown variables of the first-order polynomial, which can be directly obtained by substituting the inlet and outlet relative velocities w1 and w2.

4. The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method according to claim 3 is characterized in that: In step 3), when the relative speeds of the inlet and outlet are known according to the cubic polynomial, the four equations required to complete the cubic polynomial are set by setting the intersection position r0 of the cubic polynomial and the linear polynomial and the slope k0 at the intersection: A4=w1 (10) A1+A2+A3+A4=w2 (11) A1r0 3 +A2r0 2 +A3r0+A4=kr0+c (12) Among them, w1 is the relative velocity of the blade inlet, and w2 is the relative velocity of the blade outlet.

5. The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method according to claim 4 is characterized in that: In step 4), based on the four solved equations, in order to ensure the rationality of the distribution of relative velocity, two constraints are added to the slope of the inlet and outlet cubic polynomials. After the constraints are met, the cubic polynomial is obtained, where the constraints are: Where k1 is the slope of the cubic polynomial at the inlet, and k2 is the slope of the cubic polynomial at the outlet.

6. The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method according to claim 5, characterized in that: In step 5), the airflow angle β at different blade relative positions is calculated based on the obtained relative speed, and the formula used is: Calculate the corresponding central angle according to the airflow angle β The size of , the formula used is: in, is the central angle.

7. The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method according to claim 6, characterized in that: In step 6), in the numerical simulation of the whole machine, the three-dimensional aerodynamic model is created using UG software, the impeller mesh is divided using Turbogrid software, the collector and volute mesh are divided using ICEM software, and the mesh is imported into CFX software for numerical simulation of the whole machine to obtain the total pressure and efficiency of the fan.

8. The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method according to claim 7, characterized in that: In step 7), the Latin hypercube sampling method is used to create sample points for the intersection position r0 and the slope k0 at the intersection. The value range of the intersection position r0 is 0.2 to 0.8, and the value range of the slope k0 at the intersection is -25.4 to -30.0, which is determined by the constraints of the slopes k1 and k2 at the inlet and outlet of the cubic polynomial. The total pressure and efficiency of different sample points are obtained through numerical simulation of the whole machine, and are used as training data to complete the construction of the kriging proxy model.

9. The centrifugal fan two-dimensional blade profile design method based on the variable speed distribution method according to claim 8, characterized in that: In step 8), the constraint condition of the genetic algorithm is the original wind turbine design full pressure of 4961Pa, the population size is set to 200, and the maximum iteration number is 100.

10. A centrifugal fan two-dimensional blade profile design system based on a variable speed distribution method, characterized in that: include: The first solution module calculates the fan blade inlet and outlet meridian velocity c according to the original fan impeller structural parameters 1m and c 2m Size, then solve the size of the inlet and outlet relative speeds w1 and w2; The distribution equation determination module determines the distribution equation of the relative speed along the relative position of the blade: the distribution equations of the relative speed w along the relative position r of the blade are respectively specified as a cubic polynomial and a linear polynomial; The parameter setting module, based on the cubic polynomial, when the relative speed of the inlet and outlet is known, sets the intersection position r0 of the cubic polynomial and the linear polynomial and the slope k0 at the intersection, thereby completing the four equations required by the cubic polynomial; The constraint condition adding module adds two constraint conditions for the slope of the inlet and outlet cubic polynomials based on the four solved equations to ensure the rationality of the distribution of relative velocity. After the constraint conditions are met, the cubic polynomial is obtained. The second solution module obtains the relative speed w of the blades at different relative positions from the inlet to the outlet according to the cubic polynomial, calculates the airflow angle β at different blade relative positions according to the relative speed w, and then calculates the corresponding central angle according to the airflow angle β Then, the coordinate points of the blade profile are obtained, and the coordinate points are connected to obtain the blade profile; The performance difference analysis module performs numerical simulation of the entire machine based on the obtained blade profile, and preliminarily compares the performance differences of different blade profiles obtained by combining a small number of different intersection positions r0 and slopes k0 at the intersection points; The proxy model construction module creates sample points based on the intersection position r0 and the slope k0 at the intersection, and combines the full machine numerical simulation to obtain the total pressure and efficiency of each sample to complete the construction of the Kriging proxy model; The optimal blade profile optimization module uses the efficiency predicted by the Kriging agent model as the fitness function and the fan design total pressure as the constraint condition. It uses a genetic algorithm to optimize the two parameters of the intersection position r0 and the slope k0 at the intersection to obtain the optimal blade profile.

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