Topological optimization design method for volute and air duct of high air volume fan

Abstract

The present invention belongs to the field of fan ducts, and proposes a topology optimization design method for a fan volute and an air duct, and the steps are as follows: Step 1: Calculate the speed magnitude and direction around the fan in the free space field through simulation. Step 2: Set the inlet boundary conditions of the topology calculation domain based on the calculated speed magnitude and speed direction. Step 3: Perform topology optimization calculation of the fan duct. Step 4: Reconstruct the model and perform flow field analysis based on the topologically optimized air duct and volute form. Step 5: Perform flow field analysis on the original fan duct. Step 6: Compare the air volume before and after the topology optimization of the fan volute and air duct. If the topologically optimized air duct and volute meet the expected air volume increase, the designed new air duct is completed. If the increase is insufficient or deteriorates, the number of iterations is increased and the optimization process is repeated. This optimization method has the advantage of automatic optimization; the optimized new fan volute and air duct have the advantages of low energy consumption, low vortex, and high air volume.

Description

Technical Field

[0001] The invention belongs to the field of design of fan volutes and air ducts, and relates to a topological optimization design method for fan volutes and air ducts with high air volume. Background Art

[0002] Fan duct systems, used to transport air, are a crucial component of ventilation systems. Their design requires that a certain volume of air be delivered to a designated location through the duct at the desired velocity. The air volume directly determines ventilation efficiency. With increasing demands for energy efficiency and environmental comfort in both industrial and residential sectors, optimizing the design of fan duct systems is crucial. This paper employs topology optimization techniques to optimize the design of the refrigeration fan volute and duct for a specific refrigerator model. The goal is to design a volute form and duct layout that minimizes energy loss while increasing air flow at the outlet.

[0003] Traditional fan volute and duct design relies heavily on personnel experience and requires numerous design, simulation, and verification trials. This significantly increases design time and investment costs. Furthermore, the resulting fan volute and duct layout is often suboptimal, leading to low air volume, high energy consumption, and even backflow at the outlet. To address these issues, a topology optimization design method for fan volute and duct was proposed.

[0004] The topology optimization method is a technology that uses mathematical methods to determine the optimal distribution of materials in a structure under given loads, support conditions and material properties. It has a wide range of applications in the fields of engineering design and manufacturing, especially in situations where weight reduction, performance improvement and cost reduction are required. The present invention mainly applies topology optimization technology to the optimal design of fan volutes and air ducts, utilizing minimal time and labor costs and getting rid of dependence on human experience. A layout form of a new fan volute and air duct with the advantages of low energy consumption, low vortex and high air volume is designed. The new fan volute and air duct optimized by the present invention have the advantages of low energy consumption, low vortex and high air volume. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of backflow, high energy consumption and low air volume in the fan volute air duct in the engineering field, and to propose a topological optimization design method for the fan volute air duct. Through the topological optimization technical means, the optimal form of the fan volute and the automatic optimization layout of the air duct can be performed by only giving the outlet position and the inlet position. The new fan volute and air duct optimized by the topological optimization method of the fan volute air duct proposed in the present invention have the advantages of low energy consumption, low vortex and high air volume, and include the following steps:

[0006] Step 1: Topology optimization inlet boundary conditions are obtained. The boundary conditions are obtained by obtaining the tangential velocity and normal velocity of the fan through the rated speed of the fan in the free field.

[0007] Step 2: Establishment of topology optimization model of fan volute air duct

[0008] 2.1 Setting of inlet and outlet boundary conditions;

[0009] In step 2.1, the inlet boundary condition is the velocity boundary condition, and the inlet velocity is expressed as u x with u y Indicates that u x with u y is defined as Formula 9; the outlet boundary condition is set to pressure boundary condition, static pressure 0Pa.

[0010] 2.2 Structural design of fan volute air duct topology optimization model;

[0011] Step 3: Reconstruct the 3D model of the fan volute duct topology optimization model and analyze the flow field. Use the grid filter to obtain the new duct volute contour. Use the finite element method to calculate the air volume of the optimized duct volute.

[0012] Step 4: Use the finite element method to calculate the air volume of the initial air duct volute;

[0013] Step 5: Compare the air volume before and after optimization and calculate the increase in air volume.

[0014] The working principle of the technical solution of the present invention is as follows: the flow field analysis part uses a steady-state model for calculation, and the duct wall is set to a no-slip boundary condition. Due to the complexity of the flow inside the duct, especially the complexity of the wall, it may have a significant impact on the flow characteristics. For example, flow separation, turbulent transition or flow blockage may occur inside the duct. In order to accurately simulate the internal flow, it is crucial to select the correct turbulence model. Compared with other turbulence models, the k-ω model, as a low Reynolds number model, can analyze the flow near the wall and even the wall itself. This model shows better performance when dealing with complex flow conditions such as internal flow, strong curvature flow, separated flow and jet flow, and is particularly suitable for simulating the flow conditions inside the fan duct. The topology optimization part of the optimization process starts from the original duct, expands the design space, constructs the optimized design domain, and performs mesh discretization. In the early stages of duct topology optimization design, we usually have no preset concept of the specific layout of the duct and only know the location of the fan and the air outlet. The density method of topology optimization is a widely used technology in structural topology optimization. This method describes the existence of material in the design space by introducing a pseudo-density variable. These design variables are usually defined in each cell or at each node of the grid. This method has the advantages of high design freedom, simple program design and high clarity of optimization results. The material density of the duct structure is used as the design variable (θ k ), taking the minimum energy consumption as the objective function of topology optimization, and imposing the size constraint of the fluid domain (L), the optimization formula is as follows:

[0015] Find:θ k ,(1)

[0016]

[0017] f(x i ,y i )≤L(x,y), (4)

[0018]

[0019] In the topology optimization design of fan ducts, laminar flow is used to study the flow path and velocity to more accurately control the fluid flow and obtain a better design layout. For laminar flow problems, the fan duct calculation domain is calculated using the finite element software k-ω turbulence model. The fluid flow is described by the Navier-Stokes equations as follows:

[0020]

[0021] F=-α(θ)u, (7)

[0022]

[0023] Where ρ is the fluid density, u is the fluid velocity, p is the fluid pressure, and η is the fluid dynamic viscosity. is a gradient operator defined on the computational domain Ω, α(θ) is the inverse of the local permeability, and q is a positive real number. Duct topology optimization is based on the Darcy interpolation model of the density model, introducing a resistance term F into the Stokes equations. A larger resistance term prevents fluid from traveling within the computational domain, effectively preventing fluid from traveling through solid materials within the computational domain. θ is the boundary control material volume factor, ranging from 0 ≤ θ ≤ 1. When θ = 1, the resistance term is 0, representing an air domain where the flow is unimpeded. When θ = 0, significant resistance is generated, representing a solid domain.

[0024] In order to better implement the method of the present invention, further, in step 1, the rated speed RPM of the fan is 1080r / min, the tangential speed u x0 is 1.4671m / s, and the normal velocity is u y0 It is 1.285m / s.

[0025] Furthermore, in step 2.1, the inlet velocity is expressed as u x with u y express.

[0026]

[0027] Furthermore, in step 2.2, the number of iteration steps is initially set to 100 steps.

[0028] Furthermore, in step 3, in the flow field calculations before and after optimization in steps 3 and 4, the fan speed is set to 1080 r / min, and the speed before and after optimization is kept the same.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) The present invention uses topological optimization technology to optimize the layout of the fan volute and air duct, including the establishment of the objective function, the acquisition of the boundary conditions of the topological calculation domain, the application of the variable density method, and the analysis of the flow field before and after optimization, to ensure that the optimized new fan volute air duct has low energy consumption and low vortex, thereby achieving the effect of increasing the outlet air volume.

[0031] (2) The method of the present invention eliminates the empirical dependence in traditional fan volute and air duct design, as well as the high time cost and large workload in traditional design. The method of the present invention can automatically optimize the layout of the fan volute and air duct.

[0032] (3) The new fan volute air duct optimized by the method of the present invention avoids the backflow problem of the original fan volute air duct, and the air volume after optimization is increased by 173.17 L / min, and the air volume increase rate is 34.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Flow chart of the method of the present invention;

[0034] Figure 2 The calculation domain of the initial fan volute air duct fluid in the embodiment;

[0035] Figure 3 The calculation result of the initial fan volute air duct flow field information in the embodiment;

[0036] Figure 4 The calculation results of the direction and magnitude of the fan speed around the fan when the fan speed is 1080 r / min in free space in the embodiment are as follows;

[0037] Figure 5 The calculation domain and the location of each outlet of the fan volute domain air duct topology optimization in the embodiment;

[0038] Figure 6 The topology optimization result of the wind duct in the volute area of ​​the fan in the embodiment is shown;

[0039] Figure 7 The calculation information of the wind duct flow field in the fan volute area reconstructed after optimization in the embodiment;

[0040] Figure 8 The pressure distribution diagram of the fan volute and the air duct before and after optimization for the embodiment;

[0041] Figure 9 The vortex distribution diagram of the fan volute and the air duct before and after optimization of the embodiment. DETAILED DESCRIPTION

[0042] To make the objectives, calculation methods, and advantages of the present invention more clearly understood, the specific embodiments of the present invention are further described in detail with reference to the following examples. However, the embodiments and applicable objects of the present invention are not limited thereto. Without departing from the technical concept of the present invention, various substitutions and modifications based on common technical knowledge and customary means in the art are intended to be within the scope of the present invention. The specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0043] Example:

[0044] Take the volute air duct of a refrigerator refrigeration fan as an example. Figure 2 shown. Figure 2The figure in the middle shows the fluid domain of the initial fan volute and duct before optimization. The duct contains five air outlets and one air inlet. The fan is located in the rotating domain. The rotation of the fan creates a negative pressure zone within the rotating domain, which draws air into the duct.

[0045] The velocity field distribution and streamline diagram of the fan at 1080 r / min before optimization were obtained through finite element simulation, as shown in the figure below. Figure 3 As shown in the figure, the unreasonable design of outlet 2 causes backflow.

[0046] In order to accurately describe the speed and direction around the fan after the fan rotates at the rated speed, the fan flow field distribution state under free field is constructed as follows: Figure 4 As shown in Figure 2, it provides the most realistic velocity distribution state for the inlet boundary condition in topology optimization.

[0047] Constructing a topological computing model such as Figure 5 As shown in the figure, the boundary conditions at the inlet are obtained by the velocity and size around the fan in the free field, and the velocity boundary conditions are loaded into the model using Equation 9. The outlet positions and number in the topology optimization model are consistent with the fan duct before optimization.

[0048] Figure 6 The optimization results of the fan volute and air duct. It can be seen from the figure that compared with before optimization, the fan volute form and air duct layout have changed significantly before and after topology optimization.

[0049] The optimized fan volute and air duct are subjected to flow field analysis. Figure 7 is the velocity field distribution diagram after optimization, Figure 8 and Figure 9 The pressure distribution and vortex size of the fan volute and air duct before and after optimization are shown in the figure. The figure shows that the pressure pulsation and vortex size of the fan volute and air duct after optimization are reduced, indicating that the flow performance of the fluid in the air duct is improved, the vortex loss is reduced, and the energy consumption is reduced.

[0050] Table 1 shows the comparison of air volume at each outlet before and after optimization. It can be seen from the table that the air volume is greatly improved after optimization, and the air volume increase rate reaches more than 34%.

[0051] Table 1

[0052]

[0053]

Claims

1. A topological optimization design method for a high-volume fan volute and air duct, characterized in that: The following steps are involved: Step 1: Topology optimization inlet boundary conditions are obtained. The boundary conditions are obtained by obtaining the tangential velocity and normal velocity of the fan through the rated speed of the fan in the free field. Step 2: Establishment of topology optimization model of fan volute air duct 2.1 Setting of inlet and outlet boundary conditions; In step 2.1, the inlet boundary condition is the velocity boundary condition, and the inlet velocity is expressed as u x with u y Indicates that u x with u y The definition of is formula 9; u x0 is the tangential velocity of the fan in the free field, u y0 is the normal speed; RPM is the rated speed of the fan; 2.2 Structural design of fan volute air duct topology optimization model; In step 2.2, the objective function of the fan volute air duct topology optimization model is: The volume constraint is The governing equations used Where F = -α(θ)u, ρ is the fluid density, u is the fluid velocity, p is the fluid pressure, η is the fluid dynamic viscosity, is the gradient operator defined on the computational domain Ω, α(θ) is the inverse of the local permeability, q is a positive real number; θ is the volume factor of the boundary control material; Step 3: Reconstruct the 3D model of the fan volute duct topology optimization model and analyze the flow field. Use the grid filter to obtain the new duct volute contour. Use the finite element method to calculate the air volume of the optimized duct volute. Step 4: Use the finite element method to calculate the air volume of the initial air duct volute; Step 5: Compare the air volume before and after optimization and calculate the increase in air volume.

2. The method for topological optimization design of a volute and air duct of a high-volume fan according to claim 1, characterized in that: In step 2.2, the duct topology optimization is implemented based on the Darcy interpolation model of the density model, and a resistance term F is introduced into the Stokes equation; the larger the value of the resistance term, the less likely the fluid will be able to be transmitted in this calculation domain, which will have the effect of preventing the fluid from being transmitted when solid materials appear in the calculation domain.

3. The method for topological optimization design of a volute and air duct of a high-air-volume fan according to claim 1 or 2, characterized in that: In step 2.2, the value range of θ is 0≤θ≤1.

4. The method for topological optimization design of a volute and air duct of a high-air-volume fan according to claim 1 or 2, characterized in that: In step 1, the rated speed of the fan RPM is 1080r / min, and the tangential speed of the fan in the free field is u x0 is 1.4671m / s, and the normal velocity is u y0 It is 1.285m / s.

5. The method for topological optimization design of a volute and air duct of a high-volume fan according to claim 3, characterized in that: In step 1, the rated speed of the fan RPM is 1080r / min, and the tangential speed of the fan in the free field is u x0 is 1.4671m / s, and the normal velocity is u y0 It is 1.285m / s.

6. The method for topological optimization design of a volute and air duct of a high air volume fan according to claim 1 or 2, characterized in that: In step 2.1, the outlet boundary condition is set to a pressure boundary condition, with a static pressure of 0 Pa.

7. The method for topological optimization design of a volute and air duct of a high air volume fan according to claim 3, characterized in that: In step 2.1, the outlet boundary condition is set to a pressure boundary condition, with a static pressure of 0 Pa.

8. The method for topological optimization design of a volute and air duct of a high-air-volume fan according to claim 4, wherein: In step 2.1, the outlet boundary condition is set to a pressure boundary condition, with a static pressure of 0 Pa.

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