Method for measurement and multi-index evaluation of material suction uniformity of bent pipe
By setting multiple observation sections in the bend and combining high-precision anemometer measurements with CFD-DEM coupled simulation, multi-index evaluation indicators are calculated, solving the reliability problem of evaluating the uniformity of material suction in the bend and realizing support for accurate quantification and optimized design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIANGTAN UNIV
- Filing Date
- 2025-12-16
- Publication Date
- 2026-04-17
AI Technical Summary
Existing technologies for evaluating the uniformity of material suction in bent pipes suffer from problems such as reliance on experience-based judgment, sparse measurement points, insufficient reliability of simulation results, and single evaluation indicators, making it difficult to achieve accurate quantification and comprehensive guidance for optimization.
By setting multiple observation sections in the bend, and combining high-precision anemometer measurements with CFD-DEM coupled simulation, multiple evaluation indicators such as average velocity, root mean square error of velocity, and velocity uniformity index are calculated. The results of field experiments and simulations are compared to form a multi-index combined evaluation system.
This method enables reliable measurement and accurate evaluation of the uniformity of material suction in bent pipes, provides direct basis for optimization design, verifies the accuracy of the simulation model, and solves the shortcomings of traditional methods.
Smart Images
Figure FT_1 
Figure FT_2 
Figure FT_3
Abstract
Description
Technical Field
[0001] This invention belongs to the field of industrial pipeline flow field detection and simulation verification technology, specifically involving a method for measuring and evaluating the uniformity of material suction in a bend pipe using multiple indicators. Background Technology
[0002] In pipeline transportation systems of industries such as coal, power, and chemicals, bends are key components connecting transport pipelines and changing the direction of material flow. However, due to the influence of various complex fluid dynamics effects such as centrifugal force and secondary flow when fluids flow through bends, the airflow velocity distribution within the pipeline often exhibits severe non-uniformity. This non-uniform flow field distribution leads to the following: when transporting materials, especially viscous particulate materials, materials can be smoothly transported in high-velocity areas, while materials in low-velocity areas near the wall suffer from insufficient kinetic energy and tend to deposit and adhere. This situation easily causes pipeline blockage, seriously affecting the continuity and stability of the production process.
[0003] Currently, research and evaluation methods for the uniformity of material suction in bends in both industry and academia remain limited. Industrial practice often relies on empirical qualitative judgments or multi-point velocity measurements. While these methods can obtain accurate data, they are generally sparse, failing to comprehensively reflect the true flow field distribution. Coupled simulations using Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) can simulate gas-solid two-phase flow and provide rich flow field information, but their accuracy heavily depends on model parameters and boundary conditions. The lack of a systematic experimental verification framework limits their reliable application in precise engineering design and optimization. Existing flow field uniformity evaluations often use single statistical indicators such as relative standard deviation (CV), making it difficult to comprehensively evaluate flow uniformity and simulation reliability from multiple perspectives, including spatial distribution details, model prediction accuracy, and consistency with physical laws.
[0004] Therefore, there is an urgent need in this field to establish a systematic and scientific measurement and evaluation method. This method should be able to integrate high-precision physical experiments with gas-solid two-phase flow simulation, and comprehensively utilize multiple indicators such as macroscopic statistics, spatial distribution consistency, prediction error, and conformity to physical laws to achieve accurate quantitative evaluation of the uniformity of material intake in bends, and verify the accuracy of simulation models. This will provide reliable technical support and decision-making basis for the optimized design, performance evaluation, and engineering modification of industrial bends. Summary of the Invention
[0005] Purpose of the invention: This invention provides a method for measuring and evaluating the uniformity of material suction in a bend pipe using multiple indicators, offering a scientific, systematic, and reliable solution for evaluating the uniformity of material suction in bend pipes.
[0006] 1. A method for measuring and evaluating the uniformity of material suction in a bend pipe using multiple indicators, comprising the following steps:
[0007] (1) Make a model of the bent pipe and record the dimensions of the bent pipe;
[0008] (2) Set up observation sections at multiple specific locations in the bend along the material flow direction;
[0009] (3) Connect the bend to the fan system to generate a stable negative pressure environment and suck up the material. Use a high-precision anemometer to measure the velocity values at multiple points in each observation section.
[0010] (4) Based on the precise dimensions of the actual bent pipe, establish the corresponding three-dimensional model and perform CFD-DEM coupled simulation to obtain the velocity distribution data of each observation section;
[0011] (5) Based on the velocity data obtained in the above steps, calculate the average velocity, root mean square error of velocity, and velocity uniformity index of each section;
[0012] (6) Compare the average velocity, root mean square error of velocity, and velocity uniformity index between the field experimental test and the CFD-DEM coupled simulation, and compare the velocity distribution cloud map between the field experimental test and the CFD-DEM coupled simulation.
[0013] The beneficial effects of this invention are as follows: it solves the problems of reliance on experience and sparse measurement points in traditional methods, and obtains reliable full-section flow field data through high-density array point layout and systematic process; it solves the problem of insufficient credibility of gas-solid two-phase flow simulation results in engineering, and realizes the accuracy verification of CFD-DEM coupled simulation model through multi-index comparison; it solves the problem of single evaluation index and inability to comprehensively guide optimization, and forms a quantifiable and comparable multi-index combination evaluation system, thereby providing direct and reliable decision-making basis for pipe bend design and optimization.
[0014] The bending pipe model in step (1) contains at least two bending segments.
[0015] The aforementioned beneficial effects are: it is widely applicable to the bend configurations in most engineering projects, and can form a sufficiently complex velocity distribution, accurately reflecting the flow characteristics of the bend.
[0016] The pressure range of the negative pressure environment in step (1) is [-6000Pa, -2000Pa].
[0017] The aforementioned beneficial effects are: the pressure range covers the actual working conditions of most industrial negative pressure suction systems, verifying the versatility of the method within the range of real working conditions.
[0018] In step (2), at least three observation sections are set at specific locations in the bend.
[0019] The aforementioned beneficial effects are: setting up observation sections at at least three specific locations can cover the core flow field region of the bend, accurately describing the overall airflow distribution inside the suction pipe.
[0020] In step (3), the number of measuring points set for each observation section is at least twenty, the measuring points cover the core and edge areas of the section, and are distributed in a radial array of at least two layers of concentric rings.
[0021] The aforementioned beneficial effects are as follows: this measurement point distribution scheme can accurately capture the velocity gradient changes in different regions within the cross-section, reflecting the overall velocity distribution across the entire cross-section. Furthermore, the data collected can generate velocity contour maps, which can be directly compared with the gas phase results from CFD-DEM coupled simulations.
[0022] In step (5), the velocity uniformity index range is [0,1], and the closer the value is to 1, the better the uniformity.
[0023] The aforementioned benefits are: the uniformity evaluation results are intuitive, enabling rapid comparison of the effects between different schemes, and providing clear quantitative targets for engineering optimization.
[0024] In step (5), the root mean square error of the velocity of the measuring point of each cross section in the field experiment and the gas phase velocity of the measuring point at the corresponding position of the CFD-DEM coupled simulation cross section is calculated.
[0025] The aforementioned beneficial effects are: the velocity values of all measuring points were compared, thus verifying the accuracy of the simulation model.
[0026] Step (6) compares whether the relative error between the average velocity of the field test and the average velocity of the CFD-DEM coupled simulation at the same observation section does not exceed 10%, whether the root mean square error of the velocity at the same section is less than 10 m / s, and whether the velocity uniformity index of each observation section changes in a consistent manner.
[0027] The aforementioned beneficial effects are: the comparison of average speed, root mean square error of speed, and speed non-uniformity index can statistically confirm the accuracy of the measurement results.
[0028] Step (6) compares the consistency of the morphology, location and relative range of the high-speed distribution area and the low-speed distribution area in the velocity distribution cloud map of the field experimental test and CFD-DEM coupled simulation.
[0029] The aforementioned beneficial effects are: the consistency between the on-site experimental test cloud map and the CFD-DEM coupled simulation cloud map can verify the accuracy of CFD-DEM coupled simulation in capturing the real flow characteristics of the gas phase.
[0030] The method further includes: applying the method to evaluate the uniformity of material suction of different bent pipe structures, that is, adding a structure to the bent pipe model and repeating the above steps (1) to (6) to evaluate the uniformity of material suction of the new bent pipe model and verify the feasibility of the method.
[0031] The aforementioned beneficial effects are: verifying the feasibility, accuracy, and universality of the method. Attached Figure Description
[0032] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:
[0033] Figure 1 This is a flowchart of the invention;
[0034] Figure 2 This is a schematic diagram of the measurement point distribution established by the present invention;
[0035] Figure 3 This is a schematic diagram of the three-dimensional model of the present invention;
[0036] Figure 4 This is the CFD-DEM coupled simulation page for the bent pipe;
[0037] Figure 5 These are test velocity contour maps of various cross-sections of the bend;
[0038] Figure 6 These are simulated velocity contour maps of various cross sections of the bend;
[0039] Figure 7 This is a schematic diagram of the three-dimensional model of the present invention after adding the flared mouth structure;
[0040] Figure 8 This is the CFD-DEM coupled simulation page after adding a flared structure to the bent pipe;
[0041] Figure 9 These are test velocity contour maps of various cross sections after adding a flared structure to the bent pipe;
[0042] Figure 10 These are simulated velocity contour maps of various cross sections after adding a flared structure to the bent pipe. Specific implementation methods
[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.
[0044] A method for measuring and evaluating the uniformity of material suction in a bend pipe using multiple indicators, such as Figure 1As shown, it includes the following steps:
[0045] 1. Create a model of the bent pipe and record its dimensions;
[0046] 2. Set up multiple observation sections at specific locations in the bend along the material flow direction;
[0047] 3. Connect the bend to the fan system to create a stable negative pressure environment and suck up the material. Use a high-precision anemometer to measure the velocity values at multiple points on each observation section.
[0048] 4. Based on the precise dimensions of the actual bent pipe, establish the corresponding three-dimensional model and perform CFD-DEM coupled simulation to obtain the velocity distribution data of each observation section;
[0049] 5. Based on the velocity data obtained in the above steps, calculate the average velocity, root mean square error of velocity, and velocity uniformity index for each cross section;
[0050] 6. Compare the average velocity, root mean square error of velocity, and velocity uniformity index between the field experimental test and the CFD-DEM coupled simulation, and compare the velocity distribution cloud maps between the field experimental test and the CFD-DEM coupled simulation;
[0051] Step 1 of this embodiment of the invention is specifically as follows:
[0052] 1-1. The bend consists of three continuous bends. The first bend has a bending radius of 935mm and a bending angle of 40°. The second bend has a bending radius of 940mm and a bending angle of 35°. The third bend has a bending radius of 960mm and a bending angle of 45°. The total height of the bend is 1300mm and the diameter of the bend is 180mm.
[0053] Step 2 of this embodiment of the invention is specifically as follows:
[0054] 2-1. Taking the bend inlet as the reference, set cross-sections at distances of 1265mm, 955mm, 745mm, 535mm, and 210mm from the bend inlet, respectively. The cross-section positions are as follows: Figure 3 As shown.
[0055] Step 3 of this embodiment of the invention is specifically as follows:
[0056] 3-1. Connect the bend to the fan system. The bend should be 180mm above the ground. Start the fan to generate a negative pressure of 4500Pa.
[0057] 3-2. Add dry coal to the inlet of the bend. The coal particle diameter should be in the range of 9-12mm, and the addition rate should be 2kg / s.
[0058] 3-3, such as Figure 2As shown, 25 measuring points are determined at each cross section. At the outermost edge of the pipe cross section, close to the inner wall of the bend, 16 measuring points are evenly arranged along the circumference with an interval of 22.5. At 1 / 2 of the radius, 8 measuring points are evenly arranged along the circumference with an interval of 45°. One measuring point is set at the geometric center of the cross section.
[0059] 3-4. Use a high-precision anemometer to measure the velocity at each measuring point on the cross section.
[0060] Step 4 of this embodiment of the invention is specifically as follows:
[0061] 4-1, such as Figure 3 As shown, a three-dimensional model is built based on the dimensions measured in step 1, wherein an extension domain is added at the inlet of the bend, with a length and width of 500mm and a height of 180mm.
[0062] 4-2. In Fluent software, set the parameters as follows: select the Euler model for the multiphase flow model, the standard k-epsilon model for the viscous model, the extended wall function for the wall function, set the inlet boundary condition to a pressure outlet with a pressure of atmospheric pressure, set the outlet boundary condition to a pressure outlet with a pressure 4500 Pa lower than atmospheric pressure, set the pressure factor to 0.2, and set the momentum, turbulent kinetic energy, and turbulent dissipation rate to 0.5. Start the automatic save function and export an h5 file.
[0063] 4-3. Set the parameters in the Rocky software: Particle density is 1442 kg / m³. The particle size distribution is 9-12 mm, and the Young's modulus is... Pa, Poisson's ratio is 0.3. After importing the h5 file and clicking run, the simulation page looks like this. Figure 4 As shown.
[0064] 4-4. After the simulation is completed, analyze the calculation results in CFD-Post software and collect the coordinates and velocities of all nodes in each section;
[0065] Step 5 of this embodiment of the invention is specifically as follows:
[0066] 5-1. Based on the node coordinates and velocity values of each cross section obtained through on-site experimental testing in step 3, and the node coordinates and velocities of each cross section collected through CFD-DEM coupled simulation in step 4, the average velocity, root mean square error of velocity, and velocity uniformity index were calculated. The statistical results are shown in Table 1.
[0067] Table 1. Comparison of average velocity, root mean square error of velocity, and velocity uniformity index at various cross-sections of the bent pipe model.
[0068]
[0069] 5-2. Calculate the average velocity of each cross section obtained from field experimental tests and CFD-DEM coupled simulation statistics. The calculation formula is as follows: ,in The velocity is the velocity measured at a point on the cross section, and n is the total number of measuring points on the cross section.
[0070] 5-3. Calculate the root mean square velocity coefficient (RMSE) of each cross section obtained from field experimental tests and CFD-DEM coupled simulation statistics. The calculation formula is as follows: ,in It is the velocity measured at the cross-section of the test site, which is statistically analyzed in the field experiment. is the velocity of the measurement points on the cross section statistically obtained from CFD-DEM coupled simulation, where n is the total number of measurement points on the cross section;
[0071] 5-4. Calculate the velocity uniformity index of 10 cross sections obtained from field experimental tests and CFD-DEM coupled simulation statistics. The velocity uniformity index has a range of [0,1] and is calculated using the following formula: ,in It is the velocity measured at a point on the cross section. is the cross-sectional average velocity, and n is the total number of measuring points on the cross section;
[0072] Step 6 of this embodiment of the invention is specifically as follows:
[0073] 6-1. Compare whether the relative error between the average velocity measured in the field experiment at the same observation section in step 5 and the average velocity measured in the CFD-DEM coupled simulation does not exceed 10%, whether the root mean square error of the velocity at the same section is less than 10 m / s, and whether the trend of the velocity uniformity index changes at each observation section is consistent; as shown in Table 1, the average velocity error at the same section is less than 10%, the root mean square error of the velocity at the same section is less than 10 m / s, and the velocity uniformity index changes at planes 1, 2, and 3. The velocity uniformity index of planes 3, 4, and 5 gradually decreases from 0.01, indicating that the velocity uniformity index changes in a consistent trend. This demonstrates that the method can achieve a quantitative evaluation of the flow field inside the bend, verifying the reliability of the measurement method and confirming the accuracy of the simulation model.
[0074] 6-2. Import the coordinates and velocity values obtained in steps 3 and 4 into Origin software to generate a velocity contour map. Determine whether the shape, location, and relative range of the high-speed distribution area are consistent with those of the low-speed distribution area; for example... Figure 5 , 6 As shown, the morphology, location, and relative range of the high-speed and low-speed distribution regions in the cross-sectional cloud maps of the field experimental test and CFD-DEM coupled simulation are consistent.
[0075] 7-1, such as Figure 7As shown, a flared structure is added to the inlet of the bent pipe model, with an expansion angle of 70° and a diameter of 216mm. Then, steps 1-6 are repeated. The simulation page is shown below. Figure 8 As shown;
[0076] 7-2. Based on the nodal coordinates and velocity values of each cross-section obtained through on-site experimental testing in step 3, and the coordinates and velocities of each cross-section node collected in step 4, the average velocity, root mean square error of velocity, and velocity uniformity index were calculated. The statistical results are shown in Table 2.
[0077] Table 2 Comparison of average velocity, root mean square error of velocity, and velocity uniformity index for each section of the bell-shaped bend model.
[0078]
[0079] 7-3. Compare whether the relative error between the average velocity measured in the field experiment at the same observation section in step 5 and the average velocity measured in the CFD-DEM coupled simulation does not exceed 10%, whether the root mean square error of the velocity at the same section is less than 10 m / s, and whether the trend of the velocity uniformity index changes at each observation section is consistent; as shown in Table 2, the average velocity error at the same section is less than 10%, the root mean square error of the velocity at the same section is less than 10 m / s, and the velocity uniformity index changes at planes 1, 2, and 3. The velocity uniformity index of planes 3, 4, and 5 gradually increases from 0.01, indicating that the velocity uniformity index changes in a consistent trend. This demonstrates that the method can achieve a quantitative evaluation of the flow field inside the bend, verifying the reliability of the measurement method and confirming the accuracy of the simulation model.
[0080] 7-4. Import the coordinates and velocity values obtained in steps 3 and 4 into Origin software to generate a velocity contour map. Determine whether the shape, location, and relative extent of the high-speed and low-speed distribution areas are consistent. Figure 9 , 10 As shown, the shape, location, and relative range of the high-speed and low-speed distribution regions in the cross-sectional cloud maps of the physical test and fluid dynamics simulation are consistent.
Claims
1. A method for measuring and evaluating the uniformity of material suction in a bend pipe using multiple indicators, comprising the following steps: S1. Create a model of the bent pipe and record the dimensions of the bent pipe; S2. Along the material flow direction, set up observation sections at multiple specific locations in the bend; S3. Connect the bend to the fan system to create a stable negative pressure environment and suck up the material. Use a high-precision anemometer to measure the velocity values at multiple points in each observation section. S4. Based on the precise dimensions of the actual bent pipe, establish the corresponding three-dimensional model and perform CFD-DEM coupled simulation to obtain the velocity distribution data of each observation section; S5. Based on the velocity data obtained in the above steps, calculate the average velocity, root mean square error of velocity, and velocity uniformity index for each section. S6. Compare the average velocity, root mean square error of velocity, and velocity uniformity index between the field experimental test and the CFD-DEM coupled simulation, and compare the velocity distribution cloud map between the field experimental test and the CFD-DEM coupled simulation.
2. The method of claim 1, wherein, In step S1, the pipe bending model contains at least two bending segments.
3. The method of claim 1, wherein, In step S2, at least three observation sections are set at specific locations in the bend.
4. The method of claim 1, wherein, In step S3, the pressure range of the negative pressure environment is [-6000Pa, -2000Pa].
5. The method of claim 1, wherein, In step S3, at least twenty measuring points are set for each observation section, covering the core and edge areas of the section, and are distributed in a radial array of at least two layers of concentric rings.
6. The method of claim 1, wherein, In step S5, the average speed The calculation formula is as follows: ,in Here, n is the velocity at the measuring points on the cross section, and n is the total number of measuring points on the cross section; the root mean square error (RMSE) of velocity is calculated using the following formula: ,in It is the velocity measured at the cross-section of the test section, which is statistically analyzed in the field experiment. It is the velocity measured at the cross-section in the statistical analysis of CFD-DEM coupled simulation.
7. The method of claim 1, wherein, In step S5, the velocity uniformity index ranges from [0,1], and the closer the value is to 1, the better the uniformity. The calculation formula is as follows: ,in It is the velocity measured at a point on the cross section. is the cross-sectional average velocity, and n is the total number of measuring points on the cross-section.
8. The method of claim 1, wherein, In step S6, compare whether the relative error between the average velocity of the field test and the average velocity of the CFD-DEM coupled simulation of the same cross section does not exceed 10%, whether the root mean square error of the velocity of the same cross section is less than 10 m / s, and whether the velocity uniformity index of each cross section changes in a consistent manner.
9. The method of claim 1, wherein, In step S6, the consistency of the morphology, location, and relative range of the high-speed distribution area and the low-speed distribution area in the velocity distribution cloud map of the field experimental test and the CFD-DEM coupled simulation is compared.
10. The method of claim 1, wherein, The method further includes: applying the method to evaluate the material suction uniformity of bent pipes with different structures, that is, adding a structure to the bent pipe model and repeating steps S1 to S6 as described in claim 1 to evaluate the material suction uniformity of the new bent pipe model and verify the feasibility of the method.