Low-noise fan design method

Abstract

The invention provides a low-noise fan design method. The low-noise fan design method comprises the steps that pipeline flow field numerical simulation is conducted on an initial fan through a Reynolds average Navier-Stokes equation; utilizing a Lowson model to predict the pure tone noise of the initial fan blade; performing bionic design on blades of the initial fan in combination with an owl wing and feather structure to obtain blades of a bionic fan, and determining parameters of the blades of the bionic fan; and noise and aerodynamic performance of the blades of the bionic fan and the blades of the initial fan are evaluated and compared. The bionic design concept is adopted, an owl feather structure capable of achieving mute flight is used for conducting aerodynamic shape design on fan blades, and evaluation and comparison find that compared with an initial fan, the noise intensity is remarkably reduced, meanwhile, the aerodynamic performance is also improved, and the design is more reasonable. The bionic fan can be widely applied to systems with large fan equipment, such as transformer substations and cooling towers.

Description

Technical Field

[0001] This application belongs to the technical field of pipeline noise reduction, and more specifically, it relates to a design method for a low-noise fan. Background Art

[0002] During the operation of some large industrial equipment or systems, a fan system must be used for ventilation and heat dissipation. However, the fan system will generate a large amount of noise. This noise will not only affect the health of the staff, but the vibration caused by it will even damage mechanical equipment. As the problem of fan noise becomes increasingly severe, people pay more and more attention to the harm of noise, and a low-noise fan has become the most basic requirement of people.

[0003] The noise generated during the operation of a fan can be divided into aerodynamic noise, mechanical noise, and electromagnetic noise. From the causes of fan aerodynamic noise, it can be seen that reasonable fan design is the most fundamental method to reduce fan aerodynamic noise. Therefore, most of the control of fan noise is carried out from the aspect of optimizing the fan structure. Reasonable selection of fan parameters can not only improve the efficiency of the fan, but also achieve the purpose of reducing fan noise. For example, using forward-swept blades to reduce fan noise, using inclined rectifying vanes to reduce fan rotation noise, using unequal blades to reduce fan rotation noise, etc. With the in-depth exploration of the fan blade shape in terms of aerodynamic and noise design in the industrial field, the noise reduction benefits brought by the optimization of the blade shape are limited. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a design method for a low-noise fan to solve the technical problem of limited noise reduction benefits brought by the optimization of the conventional blade shape in the existing technology.

[0005] To achieve the above purpose, the technical solution adopted in this application is: providing a design method for a low-noise fan, including:

[0006] Performing numerical simulation of the pipeline flow field on the initial fan through the Reynolds-averaged Navier-Stokes equations;

[0007] Predicting the pure tone noise of the blades of the initial fan using the Lowson model;

[0008] Combining the structure of an owl's wings and feathers to perform bionic design on the blades of the initial fan to obtain the blades of the bionic fan and determine the parameters of the blades of the bionic fan;

[0009] Evaluating and comparing the noise and aerodynamic performance of the blades of the bionic fan and the blades of the initial fan.

[0010] Further, the integral form of the Reynolds-averaged Navier-Stokes equations is:

[0011]

[0012] In the formula: Ω is the control volume, is the boundary of the control volume, Q is the conserved quantity of the flow field, dS represents the differential element of the surface integral, n is the unit normal vector of the outer normal of the control surface dS, and F(Q) and G(Q) are the inviscid flux and viscous flux respectively.

[0013] Furthermore, in the Lowson model, the sound pressure level radiated by the rotor blade is:

[0014]

[0015] In the formula, J mz-λ is the first Bessel function of order mz - λ, z is the number of blades, j 2 = -1. Thus, the noise contributions of the modal components F x (λ) and F y (λ) can be more intuitively understood.

[0016] Furthermore, the blades of the bionic fan adopt a bionic noise reduction design with a serrated trailing edge and a streamlined leading edge shape of the blade.

[0017] Furthermore, the parameters of the bionic fan blades include the serration amplitude 2h and the serration wavelength λ.

[0018] Furthermore, a numerical calculation model is established to calculate the aerodynamic characteristics and noise level of the initial fan.

[0019] Furthermore, the numerical calculation model includes a far - field inlet static region, a stator blade region, a rotor blade rotation region, and a far - field outlet static region, and the calculation of each region uses unstructured grids.

[0020] Furthermore, based on the calculation and analysis results in the numerical simulation of the pipeline flow field, the leading edge of the blades of the initial fan is designed with a streamlined modification to improve the flow separation induced by the blunt body. At the same time, an owl - bionic serrated shape design is adopted at the trailing edge of the blades of the initial fan to obtain the blades of the bionic fan.

[0021] Furthermore, the aerodynamic characteristics and noise level of the blades of the bionic fan are calculated to obtain noise and aerodynamic performance parameters, and a comparison is made with the initial fan.

[0022] Furthermore, the noise and aerodynamic performance parameters include the axial velocity at the outlet section behind the rotor, the sound pressure level spectrum, the sound power level spectrum, and the fundamental frequency noise.

[0023] The beneficial effects of the low-noise fan design method provided by this application are as follows: Compared with the prior art, this application adopts a bionic design concept, draws on the structure of owl feathers that can fly silently to conduct aerodynamic shape design of the fan blades, and proposes corresponding numerical simulation methods for the pipeline flow field and pure tone noise prediction methods. Through evaluation and comparison, it is found that the bionic design concept has a greater space for noise reduction benefits. Compared with the initial fan, the noise intensity of this application has been significantly reduced, and at the same time, the aerodynamic performance has also been improved. The bionic fan can be widely applied in systems with large fan equipment such as substations and cooling towers. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a flowchart of the low-noise fan design method provided by the embodiment of this application;

[0026] Figure 2 It is a schematic diagram of the relative positions of the noise source and the observation point in the Lowson model of the low-noise fan design method provided by the embodiment of this application;

[0027] Figure 3 It is a schematic diagram of the serrated trailing edge structure of the bionic fan in the low-noise fan design method provided by the embodiment of this application;

[0028] Figure 4 It is a schematic diagram of the structure of the DFBZ-6.3 square wall-mounted axial flow fan in the low-noise fan design method provided by the embodiment of this application;

[0029] Figure 5 It is a schematic diagram of the numerical calculation model in the low-noise fan design method provided by the embodiment of this application;

[0030] Figure 6 It is a schematic diagram of the surface mesh of the far-field intake static region in the numerical calculation model of the low-noise fan design method provided by the embodiment of this application;

[0031] Figure 7 It is a schematic diagram of the surface mesh of the stator blade region in the low-noise fan design method provided by the embodiment of this application;

[0032] Figure 8 It is a schematic diagram of the surface mesh of the rotor blade rotation region in the low-noise fan design method provided by the embodiment of this application;

[0033] Figure 9 Schematic diagram of the surface mesh in the static area at the far - field outlet in the low - noise fan design method provided by the embodiment of the present application;

[0034] Figure 10 Schematic diagram of the spatial mesh distribution in the computational domain in the low - noise fan design method provided by the embodiment of the present application;

[0035] Figure 11 Schematic diagram of the shape of the bionic blade in the low - noise fan design method provided by the embodiment of the present application;

[0036] Figure 12 Schematic diagram of the surface mesh of the bionic blade in the low - noise fan design method provided by the embodiment of the present application;

[0037] Figure 13 Axial velocity contour map at the rear outlet cross - section of the initial fan rotor in the low - noise fan design method provided by the embodiment of the present application;

[0038] Figure 14 Axial velocity contour map at the rear outlet cross - section of the bionic fan rotor in the low - noise fan design method provided by the embodiment of the present application;

[0039] Figure 15 Sound pressure level spectrum curves of the initial fan and the bionic fan in the low - noise fan design method provided by the embodiment of the present application;

[0040] Figure 16 Sound power level spectrum curves of the initial fan and the bionic fan in the low - noise fan design method provided by the embodiment of the present application;

[0041] Figure 17 Directivity curves of the fundamental frequency noise of the initial fan and the bionic fan in the low - noise fan design method provided by the embodiment of the present application. Detailed implementation manners

[0042] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0043] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0044] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0045] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0046] Please refer to Figure 1 , and now the low-noise fan design method provided by the embodiments of the present application will be described. The low-noise fan design method specifically includes the following steps:

[0047] Step 1: Numerically simulate the duct flow field of the initial fan through the Reynolds-averaged Navier-Stokes equations (RANS);

[0048] Step 2: Predict the pure tone noise of the blades of the initial fan using the Lowson model;

[0049] Step 3: Carry out bionic design on the blades of the initial fan by combining the owl wing and feather structures to obtain the blades of the bionic fan and determine the parameters of the blades of the bionic fan;

[0050] Step 4: Evaluate and compare the noise and aerodynamic performance of the blades of the bionic fan and the blades of the initial fan.

[0051] Compared with the prior art, the low-noise fan design method provided by the present application adopts the bionic design concept, draws on the owl feather structure capable of silent flight for the aerodynamic shape design of the fan blades, and proposes corresponding numerical simulation methods for the duct flow field and pure tone noise prediction methods. Through evaluation and comparison, it is found that the bionic design concept has a greater noise reduction benefit space. Compared with the initial fan, the noise intensity of the present application is significantly reduced, and at the same time, the aerodynamic performance is also improved. The bionic fan can be widely applied in systems with large fan equipment such as substations and cooling towers.

[0052] In an embodiment of the present application, the integral form of the Reynolds-averaged Navier-Stokes equations is:

[0053]

[0054] where: Ω is the control volume, is the boundary of the control volume, Q is the conserved quantity of the flow field, dS represents the differential element of the surface integral, n is the unit outer normal vector of the control surface dS, and F(Q) and G(Q) are the inviscid flux and viscous flux respectively.

[0055] In this embodiment, the spatial discretization scheme of the Reynolds-averaged Navier-Stokes equations is the second-order upwind Roe scheme, which can not only achieve a good balance between the solution accuracy and the solution efficiency, but also its calculation accuracy can meet the capture of complex flow phenomena such as separated flow.

[0056] In this embodiment, by using the Reynolds-averaged Navier-Stokes equations to perform numerical simulation on the flow field of the initial fan in the pipeline, the flow field situation of the fan during actual operation can be simulated more accurately, providing reliable data support for the subsequent design of the fan blades. During the numerical simulation process, it is necessary to accurately model the geometric model of the initial fan and set reasonable boundary conditions and initial conditions to ensure the accuracy of the simulation results. Through numerical simulation, key information such as the velocity distribution and pressure distribution in the fan flow field can be obtained, and these information are crucial for the subsequent design of the fan blades.

[0057] In an embodiment of the present application, in the Lowson model, the sound pressure level radiated by the rotor blade is:

[0058]

[0059] where J mz-λ is the first Bessel function of order mz - λ, z is the number of blades, j 2 = -1. Thus, the noise contributions of the modal components F x (λ) and F y (λ) can be more intuitively understood.

[0060] Specifically, at low speed, the main noise component is the dipole source. For the relative positions of the noise source and the observation point, please refer to Figure 2 . Figure 2 In, x is the rotation axis, and the fluctuating load and the observer position are defined as:

[0061]

[0062] where F x and F y are the aerodynamic unsteady thrust and drag (torque) components respectively, represented by the global forces applied on the blades.

[0063] Considering the periodicity of thrust and drag, Lowson proposed the following harmonic formula:

[0064]

[0065] where λ is the harmonic order or mode.

[0066] Thus, the sound pressure level radiated by the z rotor blade is:

[0067]

[0068] In this embodiment, by using the Lowson model to predict the pure tone noise of the initial fan blade, the noise level of the initial fan blade under different working conditions can be evaluated more accurately. During the prediction process, various factors such as the blade geometry, rotational speed, and flow field conditions need to be considered to ensure the accuracy of the prediction results. Through the prediction of the Lowson model, key information such as the sound pressure level and spectral characteristics radiated by the blade can be obtained, which has important guiding significance for the subsequent bionic design of the fan blade.

[0069] In an embodiment of the present application, the blade of the bionic fan adopts a bionic noise reduction design with a serrated trailing edge and a streamlined leading edge profile.

[0070] Based on the research on the structure of owl wings and feathers and the understanding of owl's silent flight, the bionic fan in the embodiment of the present application adopts a bionic noise reduction design with a serrated trailing edge and a streamlined leading edge blade, which significantly reduces the intensity of low-frequency turbulent pulsation near the trailing edge and the amplitude of pressure pulsation on the airfoil surface, effectively reduces the spanwise correlation of the vortex at the trailing edge, and at the same time, the serrated trailing edge has little influence on the flow field upstream of the blade, and the streamlined leading edge can effectively improve the aerodynamic characteristics of the blade.

[0071] In an embodiment of the present application, for the serrated trailing edge structure, please refer to Figure 3 , and the parameters of the bionic fan blade include the serration amplitude 2h and the serration wavelength λ.

[0072] Specifically, by optimizing parameters such as the serration amplitude 2h and the serration wavelength λ, the design of the bionic fan blade can be further refined to achieve the best noise reduction and aerodynamic performance. During the design process, advanced computational fluid dynamics (CFD) technology is used to conduct detailed numerical simulations on the bionic fan blade to predict its performance in actual operation. The simulation results not only provide in-depth insights into the flow field characteristics of the blade but also provide data support for subsequent blade optimization.

[0073] In an embodiment of the present application, a numerical calculation model is established to calculate the aerodynamic characteristics and noise level of the initial fan.

[0074] Please refer to Figure 4, in this application, taking the DFBZ-6.3 square wall-mounted axial flow fan as an example, the specification model is 715×715×361mm, the power is 0.37kw, and the air volume is 10570m 3 / h. To evaluate its aerodynamic performance, a numerical calculation model as shown in Figure 5 is established.

[0075] In an embodiment of this application, the numerical calculation model includes a far-field inlet static region A, a stator blade region B, a rotor blade rotating region C, and a far-field outlet static region D. The calculation of each region uses unstructured grids.

[0076] It can be understood that an unstructured grid is a flexible grid type. It does not depend on fixed grid lines but is composed of a series of randomly distributed points or nodes, and these points or nodes are connected to form elements. In the numerical calculation model of this application, unstructured grids are widely used in each calculation region to adapt to the complex geometric shape and flow characteristics of the fan.

[0077] Specifically, the far-field inlet static region A, the stator blade region B, the rotor blade rotating region C, and the far-field outlet static region D are all divided using unstructured grids. This grid type can more accurately capture the flow details near the fan blades, such as vortices, turbulence, etc., thereby improving the accuracy and reliability of numerical calculations.

[0078] When establishing the numerical calculation model, it is necessary to reasonably divide the unstructured grid. The size, shape, and distribution of the grid will all affect the accuracy and efficiency of numerical calculations. Therefore, in this application, advanced grid generation techniques are adopted to ensure the quality and adaptability of the grid. At the same time, a sensitivity analysis of the grid is also carried out to determine the optimal grid division scheme.

[0079] By adopting unstructured grids and advanced numerical calculation methods, this application has successfully established an accurate numerical calculation model, and comprehensively evaluated the aerodynamic characteristics and noise level of the initial fan. This provides reliable data support and theoretical basis for the subsequent bionic fan blade design.

[0080] In this embodiment, the far-field inlet static region A and the far-field outlet static region D are respectively located on both sides of the rotor blade rotating region C, and the stator blade region B is located in front of the rotor blade rotating region C. The far-field inlet static region A, the stator blade region B, the rotor blade rotating region C, and the far-field outlet static region D are connected through interfaces to ensure data transfer and flow field continuity during the numerical calculation process.

[0081] Specifically, please refer to Figure 6 and Figure 9, both the far - field inlet static region A and the far - field outlet static region D are cylinders with a diameter of 1m and a length of 5m. Interpolation is performed between different regions through the interface. The calculation uses a full - turbulence model, with a high turbulence intensity of 10%, and the physical time scale for time advancement is set to 0.05s. The inlet is given a static sea - level atmosphere at 25 degrees Celsius, and the total pressure is 101,325 Pa. The outlet is set as an open boundary, with a relative static pressure of 25 Pa given, and the rotational speed of the rotating domain is 960 rev / min.

[0082] The calculation of the initial fan uses unstructured grids, with a grid quantity of 13,026,084. Among them, please refer to Figure 6 , the grid quantity of the far - field inlet static region A is 612,030; please refer to Figure 7 , the grid quantity of the stator blade region B is 1,391,963; please refer to Figure 8 , the grid quantity of the rotor blade rotating region C is 7,666,033; please refer to Figure 9 , the grid quantity of the far - field outlet static region D is 592,385. The height of the first layer of the boundary layer is 1e - 5, and the growth rate is 1.1. The spatial grid is as Figure 10 shown.

[0083] In an embodiment of the present application, according to the calculation and analysis results in the numerical simulation of the pipeline flow field, the leading edge of the blades of the initial fan is designed with fairing modification to improve the flow separation induced by the blunt body. At the same time, an owl - biomimetic serrated shape design is adopted at the trailing edge of the blades of the initial fan to obtain the blades of the biomimetic fan.

[0084] The shape of the finally designed biomimetic blade is as Figure 11 shown. The grids of the far - field inlet static region A, the stator blade region B, and the far - field outlet static region D are consistent with the calculation grids of the initial fan. The rotor blade rotating region C uses unstructured grids. The surface grid of the biomimetic blade is as Figure 12 shown. The calculation settings of the biomimetic fan are consistent with the structure of the initial fan. The total grid quantity is 17,065,926. Among them, the grid quantity of the rotor blade rotating region C is 11,705,875.

[0085] In an embodiment of the present application, the aerodynamic characteristics and noise level of the blades of the biomimetic fan are calculated to obtain noise and aerodynamic performance parameters, and compared with the initial fan.

[0086] In an embodiment of the present application, the noise and aerodynamic performance parameters include the axial velocity at the outlet section behind the rotor, the sound pressure level spectrum, the sound power level spectrum, and the fundamental frequency noise.

[0087] The axial velocity contour map at the outlet section behind the rotor of the initial fan is as Figure 13As shown; the axial velocity contour map at the rear outlet section of the bionic fan rotor is as follows Figure 14 As shown; the sound pressure level frequency spectrum curves of the initial fan and the bionic fan are as follows Figure 15 As shown, the sound power level frequency spectrum curves of the initial fan and the bionic fan are as follows Figure 16 As shown; the directivity curves of the fundamental frequency noise of the initial fan and the bionic fan are as follows Figure 17 As shown. Figures 15 to 17 Among them, Ori represents the initial fan, and Bio represents the bionic fan.

[0088] Table 1 gives the aerodynamic and noise data of the initial fan and the bionic fan. The average axial velocity at the rear outlet section of the bionic fan rotor is 8.95313 m / s, and the air volume is 10381 m 3 / h. The corresponding values of the initial fan are 7.77627 m / s and the air volume is 9023.44 m 3 / h. It can be seen that the aerodynamic performance of the bionic fan has been improved, and the air volume has increased by 15.04%. The fundamental frequency sound pressure levels at 1 m directly in front of the initial fan and the bionic fan rotors are 80.198 dB and 77.889 dB respectively, and the sound power levels of the fans are 90.999 dB and 88.687 dB respectively. It can be seen that the noise of the bionic fan has decreased by 2.3 dB.

[0089] Table 1 Performance comparison between the initial fan and the bionic fan

[0090]

[0091] Please refer to Figure 11 and Figure 12 , the external shape design inspiration of the bionic blade comes from the owl wing and feather structure. Through fine numerical simulation and optimization design, the specific parameters of the bionic blade are determined, including the shape, size of the blade, and the structural details of the serrated trailing edge and the wavy leading edge. This design aims to minimize noise and improve aerodynamic performance.

[0092] After obtaining the blades of the bionic fan, the embodiments of the present application further evaluate and compare the noise and aerodynamic performance of the bionic fan and the initial fan. Please refer to Figure 13 and Figure 14 , which are the axial velocity contour map at the rear outlet section of the initial fan rotor and the axial velocity contour map at the rear outlet section of the bionic fan rotor respectively. It can be seen by comparison that the bionic fan has significantly improved in flow field characteristics, the velocity distribution is more uniform, and the flow separation phenomenon has been effectively suppressed.

[0093] Please refer to Figure 15 and Figure 16, which are the sound pressure level spectrum curves and sound power level spectrum curves of the initial fan and the bionic fan respectively. It can be seen from the figure that the bionic fan has achieved remarkable results in noise control, and the noise intensity has been significantly reduced in multiple frequency bands.

[0094] Finally, please refer to Figure 17 , which is the directivity curve of the fundamental frequency noise of the initial fan and the bionic fan. By comparison, it can be seen that the bionic fan has also been significantly improved in terms of noise directivity, the noise distribution is more uniform, and the noise pollution in a specific direction is reduced.

[0095] In summary, the low-noise fan design method provided by the embodiments of the present application, by adopting the bionic design concept and combining the numerical simulation of the pipeline flow field and the pure tone noise prediction method, has successfully designed a bionic fan with excellent noise reduction effect and aerodynamic performance. The bionic fan can be widely applied to systems with large fan equipment such as substations and cooling towers, and has broad market application prospects.

[0096] The above are only the preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A low-noise fan design method, characterized in that, Including: Performing numerical simulation of the duct flow field of the initial fan through the Reynolds-averaged Navier-Stokes equations; Predicting the pure tone noise of the blades of the initial fan using the Lowson model; Carrying out bionic design of the blades of the initial fan by combining the structures of owl wings and feathers to obtain the blades of the bionic fan and determining the parameters of the blades of the bionic fan; Evaluating and comparing the noises and aerodynamic performances of the blades of the bionic fan and the initial fan.

2. The low-noise fan design method according to claim 1, wherein The integral form of the Reynolds-averaged Navier-Stokes equations is: where: $\Omega$ is the control volume, is the boundary of the control volume, $Q$ is the conserved quantity of the flow field, $dS$ represents the differential element of the surface integral, $n$ is the unit normal vector of the control surface $dS$, and $F(Q)$ and $G(Q)$ are the inviscid flux and the viscous flux, respectively.

3. The low-noise fan design method according to claim 1, characterized in that, In the Lowson model, the sound pressure level radiated by the rotor blades is: where J mz-λ is the first Bessel function of order mz - λ, z is the number of blades, and j 2 = -1. Thus, the noise contributions of the modal components F x (λ) and F y (λ) can be more intuitively understood.

4. The low-noise fan design method according to claim 1, characterized in that, The blades of the bionic fan adopt a bionic noise reduction design with a serrated trailing edge and streamline shaping of the blade leading edge.

5. The low-noise fan design method according to claim 1, characterized in that The parameters of the blades of the bionic fan include the serration amplitude 2h and the serration wavelength λ.

6. The low-noise fan design method according to claim 1, wherein Establishing a numerical calculation model to calculate the aerodynamic characteristics and noise level of the initial fan.

7. The low-noise fan design method according to claim 6, wherein, The numerical calculation model includes a far-field inlet stationary region, a stator blade region, a rotor blade rotating region, and a far-field outlet stationary region, and the calculation of each region uses unstructured grids.

8. The low-noise fan design method according to claim 1, characterized in that, According to the calculation and analysis results in the numerical simulation of the duct flow field, carrying out streamline modification design on the leading edge of the blades of the initial fan to improve the flow separation induced by the blunt body. At the same time, adopting an owl bionic serrated shape design at the trailing edge of the blades of the initial fan to obtain the blades of the bionic fan.

9. The low-noise fan design method according to any one of claims 1-8, characterized in that, Calculating the aerodynamic characteristics and noise level of the blades of the bionic fan to obtain noise and aerodynamic performance parameters and comparing them with the initial fan.

10. The low-noise fan design method according to claim 9, characterized in that, The noise and aerodynamic performance parameters include the axial velocity at the outlet section behind the rotor, the sound pressure level spectrum, the sound power level spectrum, and the fundamental frequency noise.

Images