Air pipe air outlet uniformity design method based on fluid simulation analysis

Abstract

The invention discloses an air pipe air outlet uniformity design method based on fluid simulation analysis. The method comprises the following steps that S10, fluid simulation analysis is conducted on an air pipe; s20, evaluating the air outlet uniformity of the air pipe; wherein S10 comprises the following steps: S11, performing pretreatment on an air duct 3D geometric model which needs to be subjected to fluid simulation analysis; s12, dividing a grid; s13, fluid dynamics simulation parameter setting is calculated; and S14, solving and calculating. The fluid simulation analysis method is used for conducting flow field simulation calculation analysis on the air pipe, internal flow field information of the air pipe under different structures can be rapidly obtained, the air pipe structure with the good air outlet uniformity is selected according to the fluid simulation result for sample piece experiment testing and confirmation, the experiment frequency and cost are reduced, and the development efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of fluid analysis, and relates to a method for designing air duct air outlet uniformity based on fluid simulation analysis. Background Art

[0002] The design of cooling ducts in traditional heat treatment equipment is generally based on the engineers' past experience. Due to the lack of detailed data on the internal flow field organization of the duct during the design phase, it is often necessary to prepare more samples for experimental testing during the trial production phase to evaluate the duct structure with better air uniformity, which requires a longer experimental cycle and higher costs. Summary of the invention

[0003] Based on the above shortcomings of the prior art, the present invention provides a method for designing air duct air outlet uniformity based on fluid simulation analysis, comprising the following steps:

[0004] S10, performing fluid simulation analysis on the air duct;

[0005] S20, air duct air uniformity assessment;

[0006] Wherein, S10 includes the following steps:

[0007] S11, pre-processing the 3D geometric model of the duct that needs to be subjected to fluid simulation analysis;

[0008] S12, grid division;

[0009] S13, computational fluid dynamics simulation parameter setting;

[0010] S14, solve the calculation.

[0011] Preferably, the 3D geometric model of the air duct in S11 includes a fan, an air inlet duct, and an air outlet duct, and the pre-processing includes model simplification and fluid calculation domain extraction.

[0012] Preferably, the model simplification includes: deleting chamfers with a radius of <1 mm, deleting bolts and filling bolt holes, deleting the connecting shaft between the fan impeller and the motor and filling the through holes on the fan casing, and filling the gaps between the fan and the air duct and between different air ducts.

[0013] Preferably, the fluid calculation domain extraction includes the impeller area and the air duct area, wherein in the impeller area, area a wrapped around the impeller is established at an offset of 10 mm on the outside of the impeller of the fan, and the thickness of the impeller is dug out in area a to obtain a fluid calculation domain A that only includes the outer wall surface of the impeller and the outer contour surface of area a; in the air duct area, the air inlet pipe, the fan housing, and the air outlet pipe are combined using a Boolean sum operation, the thick parts of the air inlet pipe, the fan housing, and the air outlet pipe are removed, and the inlet of the air inlet pipe and the outlet of the air outlet pipe are filled with surfaces to obtain area b, and area a is dug out in area b to obtain a fluid calculation domain B that only includes the outer wall surface of area a and the outer contour surface of area b.

[0014] Preferably, the grid division in S12 is specifically to set the size of the discrete grid according to the size of the air duct, including mesh encryption around the fan and in the air duct according to the characteristic area of ​​the model to capture the flow field information.

[0015] Preferably, the size of the discrete grids includes setting the basic grid size of the air inlet duct, the fan housing, and the air outlet duct, specifically taking a value of 5% of their respective equivalent diameters, wherein the equivalent diameter D = 4A / C, A is the cross-sectional area perpendicular to the direction of fluid movement, and C is the wetted circumference of the fluid flowing in the pipeline.

[0016] Preferably, the mesh encryption includes taking values ​​for the mesh size of the fan impeller area, the minimum value being 80% of the blade thickness and the maximum value being 1.5% of the impeller diameter;

[0017] Set the local small step grid size, the minimum value is 100% of the step width, and the maximum value is 160% of the step width;

[0018] Set the local small hole grid size to 16% of the hole diameter;

[0019] The grid size at the interface between fluid calculation domain A and fluid calculation domain B is set, with the minimum value being 1.6% of the diameter of the interface and the maximum value being 2.4% of the diameter of the interface.

[0020] Preferably, in the S13 computational fluid dynamics simulation parameter setting, the parameters include fan speed, duct inlet and outlet pressure conditions and fluid medium properties.

[0021] Preferably, the S14 solution calculation specifically includes setting a calculation convergence judgment standard, defining the iterative residual convergence standard as 0.001, and monitoring the velocity mean iterative change curve of the outlet plane of the air outlet duct at the same time, and judging that the calculation converges when the iterative residual is lower than 0.001.

[0022] Preferably, the S20 air duct air outlet uniformity assessment comprises the following steps:

[0023] S21, after the calculation is completed, a velocity distribution contour map on the duct outlet plane is drawn to qualitatively evaluate the uniformity of the duct air outlet. The sparser the distribution of the contour lines and the closer the difference between them is to 0, the better the air outlet uniformity.

[0024] S22, output the velocity values ​​of grid nodes at different positions on the outlet plane of the duct, use the sample variance calculation formula to calculate the variance value of the velocity distribution on the plane, and quantitatively evaluate the uniformity of the duct air outlet. The smaller the value, the lower the velocity dispersion and the better the air outlet uniformity.

[0025] The sample variance calculation formula is: S 2 is the sample variance, X is the variable, is the sample mean, n is the number of samples;

[0026] S23, comparing the air outlet uniformity evaluation results of different air duct structures, and selecting an air duct structure solution with required uniformity.

[0027] The beneficial effects of the present invention include at least: using the fluid simulation analysis method to perform flow field simulation calculation and analysis on the air duct, the internal flow field information of the air duct under different structures can be quickly obtained, and the air duct structure with better air outlet uniformity is selected according to the fluid simulation results for sample experimental testing and confirmation, so as to reduce the number and cost of experiments and improve development efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a geometric model diagram of the air duct of S11 of the air duct air outlet uniformity design method based on fluid simulation analysis of the present invention;

[0029] Figure 2 It is a schematic diagram of the S21 isovalue line of the air duct air outlet uniformity design method based on fluid simulation analysis according to a specific embodiment of the present invention;

[0030] Figure 3 A schematic diagram of network nodes in S22 of a method for designing air duct air outlet uniformity based on fluid simulation analysis according to a specific embodiment of the present invention;

[0031] Figure 4 A schematic diagram of a porous plate structure at the upper end of an air outlet duct and contour lines of a method for designing air outlet uniformity of an air duct based on fluid simulation analysis according to a specific embodiment of the present invention;

[0032] Figure 5 A schematic diagram of a porous plate structure at the lower end of an air outlet duct and contour lines of a method for designing air outlet uniformity of an air duct based on fluid simulation analysis according to a specific embodiment of the present invention;

[0033] Figure 6This is a schematic diagram of a porous plate structure with one layer at the upper and lower ends of an air outlet duct and contour lines of a method for designing air outlet uniformity of an air duct based on fluid simulation analysis in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.

[0036] The present invention comprises the following steps:

[0037] S10, performing fluid simulation analysis on the air duct;

[0038] S20, air duct air uniformity assessment;

[0039] Wherein, S10 includes the following steps:

[0040] S11, pre-processing the 3D geometric model of the duct that needs to be subjected to fluid simulation analysis;

[0041] S12, grid division;

[0042] S13, computational fluid dynamics simulation parameter setting;

[0043] S14, solve the calculation.

[0044] See also Figure 1 ,The 3D geometric model of the air duct in S11 includes fan 1, air inlet duct 2, and air outlet duct 3. The pre-processing includes model simplification and fluid calculation domain extraction.

[0045] Model simplification includes: deleting chamfers with a radius of less than 1 mm, deleting bolts and filling bolt holes, deleting the connecting shaft between the fan impeller and the motor and filling the through holes on the fan housing, and filling the gaps between fan 1 and the air duct and between different air ducts.

[0046] The fluid calculation domain extraction includes the impeller area and the air duct area. In the impeller area, area a that wraps the impeller is established at an offset of 10 mm on the outside of the fan impeller. The thickness of the impeller is dug out in area a to obtain a fluid calculation domain A that only includes the outer wall surface of the impeller and the outer contour surface of area a. In the air duct area, the air inlet pipe, fan housing, and air outlet pipe are combined using Boolean sum operation, the thick parts of the air inlet pipe, fan housing, and air outlet pipe are removed, and the inlet and outlet of the air inlet pipe are filled with surfaces to obtain area b. In area b, area a is dug out to obtain a fluid calculation domain B that only includes the outer wall surface of area a and the outer contour surface of area b.

[0047] S12 divides the grid, specifically setting the size of the discrete grid according to the size of the duct, including mesh encryption around the fan and in the duct according to the characteristic area of ​​the model to capture the flow field information.

[0048] Setting the size of the discrete grid includes setting the basic grid size of the air inlet duct, fan housing, and air outlet duct, specifically taking the value as 5% of their respective equivalent diameters, where the equivalent diameter D = 4A / C, A is the cross-sectional area perpendicular to the direction of fluid movement, and C is the wetted circumference of the fluid flowing in the pipe.

[0049] Mesh refinement includes setting the mesh size of the fan impeller area, with a minimum value of 80% of the blade thickness and a maximum value of 1.5% of the impeller diameter;

[0050] Set the local small step grid size, the minimum value is 100% of the step width, and the maximum value is 160% of the step width;

[0051] Set the local small hole grid size to 16% of the hole diameter;

[0052] The grid size at the interface between fluid calculation domain A and fluid calculation domain B is set, with the minimum value being 1.6% of the diameter of the interface and the maximum value being 2.4% of the diameter of the interface.

[0053] In the S13 computational fluid dynamics simulation parameter setting, the parameters include fan speed, duct inlet and outlet pressure conditions and fluid medium properties. Among them, fan speed: according to the rated frequency of the fan, the corresponding speed is found, which is the setting value of the fan speed value during simulation; duct inlet and outlet boundary setting: according to the environmental pressure of the duct inlet and outlet when the equipment is working, the pressure of the duct inlet and outlet during simulation is set, and the absolute pressure value of this calculation is 101325Pa; fluid medium properties: according to the pressure and temperature of the actual working environment of the equipment, the density and viscosity of the fluid medium are set. When the environmental absolute pressure is 101325Pa, the corresponding relationship between the density, viscosity and temperature of the air is shown in Table 1.

[0054] Table 1

[0055]

[0056] The S14 solution calculation specifically includes setting the calculation convergence judgment standard, defining the iterative residual convergence standard as 0.001, and monitoring the velocity mean iterative change curve of the outlet plane of the air duct. When the velocity mean iterative change curve is stable or the iterative residual is less than 0.001, the calculation is judged to be converged.

[0057] The S20 duct air outlet uniformity assessment includes the following steps:

[0058] S21, after the calculation is completed, the velocity distribution contour map on the duct outlet plane is drawn to qualitatively evaluate the uniformity of the duct outlet air. The sparser the distribution of the contour lines and the closer the difference between them is to 0, the better the uniformity of the air outlet; see Figure 2 , which is a schematic diagram of contour lines.

[0059] S22, grid nodes 11 at different positions on the outlet plane of the output air duct (see Figure 3 ) velocity value, and use the sample variance calculation formula to calculate the variance value of the velocity distribution on the plane to quantitatively evaluate the uniformity of the air duct outlet. The smaller the value, the lower the velocity dispersion and the better the air outlet uniformity.

[0060] The sample variance calculation formula is: S 2 is the sample variance, X is the variable, is the sample mean, n is the number of samples;

[0061] S23, comparing the air outlet uniformity evaluation results of different air duct structures, and selecting an air duct structure solution with required uniformity.

[0062] In the specific embodiment, see Figure 4-Figure 6 , are contour diagrams of three different air outlet duct structures, wherein the apertures of the porous plate 4 are all 12 mm, and the hole center distance is 18 mm. Figure 4 The schematic diagram of the structure and contour of the porous plate 4 at the upper end of the air outlet pipe has a variance of 7.838; Figure 5 The schematic diagram of the structure and contour of the porous plate 4 at the lower end of the air outlet pipe has a variance of 7.369; Figure 6 The diagram of the structure and contour lines of the porous plate 4 at the upper and lower ends of the air outlet pipe has a variance of 5.519. Figure 6 The air duct structure makes the air outlet uniformity the best and is the preferred solution.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing air duct air outlet uniformity based on fluid simulation analysis, characterized in that: The following steps are involved: S10, performing fluid simulation analysis on the air duct; S20, air duct air uniformity assessment; Wherein, S10 includes the following steps: S11, pre-processing the 3D geometric model of the duct that needs to be subjected to fluid simulation analysis; S12, grid division; S13, computational fluid dynamics simulation parameter setting; S14, solve the calculation.

2. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 1, characterized in that: The 3D geometric model of the air duct in S11 includes a fan, an air inlet duct, and an air outlet duct, and the pre-processing includes model simplification and fluid calculation domain extraction.

3. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 2, characterized in that: The model simplification includes: deleting chamfers with a radius of less than 1 mm, deleting bolts and filling bolt holes, deleting the connecting shaft between the fan impeller and the motor and filling the through holes on the fan housing, and filling the gaps between the fan and the air duct and between different air ducts.

4. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 2, characterized in that: The fluid calculation domain extraction includes the impeller area and the air duct area, wherein in the impeller area, an area a that wraps the impeller is established at an offset of 10 mm on the outside of the impeller of the fan, and the thickness of the impeller is dug out in area a to obtain a fluid calculation domain A that only includes the outer wall surface of the impeller and the outer contour surface of area a; in the air duct area, the air inlet pipe, the fan housing, and the air outlet pipe are combined using a Boolean sum operation, the thick parts of the air inlet pipe, the fan housing, and the air outlet pipe are removed, and the inlet of the air inlet pipe and the outlet of the air outlet pipe are filled with surfaces to obtain area b, and area a is dug out in area b to obtain a fluid calculation domain B that only includes the outer wall surface of area a and the outer contour surface of area b.

5. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 4, characterized in that: The S12 grid division is specifically to set the size of the discrete grid according to the size of the air duct, including mesh encryption around the fan and in the air duct according to the characteristic area of ​​the model to capture the flow field information.

6. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 5, characterized in that: The size of the discrete grid is set including the basic grid size of the air inlet pipe, the fan housing and the air outlet pipe, which is specifically set at 5% of their respective equivalent diameters, wherein the equivalent diameter D=4A / C, A is the cross-sectional area perpendicular to the direction of fluid movement, and C is the wetted circumference of the fluid flowing in the pipe.

7. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 5, characterized in that: The mesh encryption includes setting a value for the mesh size of the fan impeller area, with a minimum value of 80% of the blade thickness and a maximum value of 1.5% of the impeller diameter; Set the local small step grid size, the minimum value is 100% of the step width, and the maximum value is 160% of the step width; Set the local small hole grid size to 16% of the hole diameter; The grid size at the interface between fluid calculation domain A and fluid calculation domain B is set, with the minimum value being 1.6% of the diameter of the interface and the maximum value being 2.4% of the diameter of the interface.

8. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 1, characterized in that: In the S13 computational fluid dynamics simulation parameter setting, the parameters include fan speed, duct inlet and outlet pressure conditions and fluid medium properties.

9. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 1, characterized in that: The S14 solution calculation specifically includes setting a calculation convergence judgment standard, defining an iterative residual convergence standard as 0.001, and monitoring the velocity mean iterative change curve of the outlet plane of the air duct at the same time, and determining that the calculation converges when the iterative residual is lower than 0.

001.

10. The method for designing air duct air outlet uniformity based on fluid simulation analysis according to claim 1, characterized in that: The S20 air duct air outlet uniformity assessment includes the following steps: S21, after the calculation is completed, a velocity distribution contour map on the duct outlet plane is drawn to qualitatively evaluate the uniformity of the duct air outlet. The sparser the distribution of the contour lines and the closer the difference between them is to 0, the better the air outlet uniformity. S22, output the velocity values ​​of grid nodes at different positions on the outlet plane of the duct, use the sample variance calculation formula to calculate the variance value of the velocity distribution on the plane, and quantitatively evaluate the uniformity of the duct air outlet. The smaller the value, the lower the velocity dispersion and the better the air outlet uniformity. The sample variance calculation formula is: S 2 is the sample variance, X is the variable, is the sample mean, n is the number of samples; S23, comparing the air outlet uniformity evaluation results of different air duct structures, and selecting an air duct structure solution with required uniformity.

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