Design method of disc turbine stirring paddle based on combination of CFD simulation and orthogonal test

Abstract

The invention discloses a disc turbine stirring paddle design method based on combination of CFD simulation and an orthogonal test. The disc turbine stirring paddle design method comprises the steps that a design target of a disc turbine stirring paddle and influence factors of the design target are obtained; performing orthogonal test design based on the design target and the influence factors to obtain an orthogonal test scheme; geometric modeling is carried out according to data included in the orthogonal test scheme, a three-dimensional model of the disc turbine stirring paddle is obtained, CFD simulation is carried out based on the three-dimensional model of the disc turbine stirring paddle, and an orthogonal simulation result is obtained; and carrying out statistical analysis on the orthogonal simulation result, and determining the blade structure of the disc turbine stirring paddle. According to the method, factors influencing the performance of the disc turbine stirring paddle are designed according to an orthogonal test method to obtain an orthogonal test scheme, the test frequency is reduced, drawing and CFD simulation of a three-dimensional model of the disc turbine stirring paddle are carried out based on the test frequency, the shape of the disc turbine paddle is optimized according to a simulation result, and the performance of the disc turbine stirring paddle is improved. And the requirements in different application scenes can be met.

Description

Technical Field

[0001] The invention belongs to the field of bioreactor engineering, and in particular relates to a disc turbine stirring blade design method based on the combination of CFD simulation and orthogonal experiment. Background Art

[0002] As the core equipment of aerobic fermentation process, stirred bioreactor needs to have good mixing and high oxygen supply capacity to meet the needs of microbial growth and product synthesis. In actual process operation, better mixing and mass transfer effects can be obtained by increasing the stirring speed and aeration rate, but it is also accompanied by high power input. For large-scale aerobic biological fermentation production processes, ventilation and stirring account for a large proportion of the total production input cost. Therefore, in some production processes, blindly improving stirring and ventilation may reduce economic benefits or even bring negative returns.

[0003] The performance of stirred bioreactors is determined by a combination of factors such as height-to-diameter ratio, number of blades, blade type, air intake structure and operating process. Many studies have shown that the type and structure of blades are the most important factors determining the mixing and mass transfer characteristics in the reactor. The RT impeller is a typical disc turbine impeller with good mixing and mass transfer capabilities and is widely used in microbial aerobic fermentation production, but its biggest disadvantage is its high power consumption and a significant drop in power during aeration. Based on cavitation theory, researchers have designed many new disc turbine impellers by changing the curvature of the blades, such as semicircular tube impellers, asymmetric parabolic impellers, fan-shaped turbines, semi-elliptical tube-disc turbines, and so on.

[0004] The development of new impellers with high mass transfer and low power consumption has high economic value in aerobic fermentation industrial production. However, there has been no systematic and comprehensive study on the impact of blade structure on its impeller performance. Many researchers rely on experience to design and develop, which lacks system and comprehensiveness. At the same time, the design and development of the blade structure requires a lot of time and money. Even with the assistance of computational fluid dynamics technology, considering the combination optimization of multiple factors at the same time, it also requires huge computing resources. Based on orthogonal experiments and statistical analysis, it is possible to select the optimal combination of control factors and quantitatively evaluate them. Through reasonable experimental design and statistical analysis, the number of samples that need to be simulated can be reduced. Based on this, this study invented a disc turbine impeller design method based on the combination of CFD simulation and orthogonal experiments. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a disc turbine impeller design method based on the combination of CFD simulation and orthogonal test to solve the problems existing in the above prior art.

[0006] To achieve the above object, the present invention provides a disc turbine impeller design method based on a combination of CFD simulation and orthogonal test, comprising:

[0007] Obtain the design objectives and influencing factors of the disc turbine impeller;

[0008] Perform an orthogonal test design based on the design objectives and influencing factors to obtain an orthogonal test plan;

[0009] Perform geometric modeling according to the data included in the orthogonal test scheme to obtain a three-dimensional model of a disc turbine impeller, and perform CFD simulation based on the three-dimensional model of the disc turbine impeller to obtain an orthogonal simulation result;

[0010] The orthogonal simulation results are statistically analyzed to determine the blade structure of the disk turbine impeller.

[0011] Optionally, the disc turbine agitator comprises a disc, blades and a stirring shaft; the blades are arranged along the circumference of the disc and are divided into an upper part and a lower part according to a horizontal plane where the disc is located, a radial extension line of the blades at the junction of the upper part and the lower part is a curve structure that satisfies a set equation, and the stirring shaft is located in the center of the disc.

[0012] Optionally, the design target is an Ev function, wherein the Ev function is a balance between the oxygen mass transfer capacity and power consumption of the impeller, and its expression is as follows:

[0013] Ev = 0.5 × normalized value of volumetric oxygen mass transfer coefficient + 0.5 × (1 - normalized value of unit volume power input).

[0014] Optionally, factors influencing the design objective include the curvature of the blade, the degree of asymmetry between the upper and lower blades, and the radial bending angle of the blade.

[0015] Optionally, multiple level values ​​are set for each influencing factor, and single-factor CFD simulation is performed based on the influencing factor and the level value corresponding to each influencing factor to obtain the optimal level value of each influencing factor for the design objective, and orthogonal experimental design is performed based on the optimal level value.

[0016] Optionally, the process of obtaining the orthogonal simulation results includes: determining the boundary conditions and fluid domain of the three-dimensional model of the disc turbine impeller, and then performing meshing; setting the initial calculation conditions, and performing calculations and solutions based on the generated mesh file and the initial calculation conditions until the torque of the impeller reaches stability, thereby obtaining the orthogonal simulation results.

[0017] Optionally, the process of performing statistical analysis on the orthogonal simulation results to determine the blade structure of the disc turbine impeller includes: evaluating the order of influence of three factors, namely, the curvature of the blade, the degree of asymmetry of the upper and lower blades, and the radial bending angle of the blade, on the design objectives through orthogonal simulation results and range analysis; evaluating the significance level of the influence of three factors, namely, the curvature of the blade, the degree of asymmetry of the upper and lower blades, and the radial bending angle of the blade on the design objectives through orthogonal simulation results and variance analysis, and determining the blade structure of the disc turbine impeller based on the order of influence and the significance level analysis results with the goal of obtaining the maximum value of the design objective.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] The present invention provides a disc turbine impeller design method based on the combination of CFD simulation and orthogonal experiment. The factors affecting the performance of the disc turbine impeller are designed according to the orthogonal experiment method to obtain an orthogonal experiment scheme, which reduces the number of experiments. Based on this, a three-dimensional model of the disc turbine impeller is drawn and CFD simulation is performed, and the shape of the disc turbine blade is optimized according to the simulation results, thereby realizing the determination of the optimal shape of the disc turbine blade through numerical simulation design to meet the needs of different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0021] Figure 1 A flow chart of a disc turbine impeller design method based on a combination of CFD simulation and orthogonal test according to an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of a three-dimensional structure of a disk turbine blade designed for an orthogonal test of an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of the structure of a bioreactor used in CFD simulation of an embodiment of the present invention;

[0024] Figure 4 It is a schematic diagram of the three-dimensional structure of the disc turbine blade according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0027] Embodiment 1

[0028] like Figure 1-4 As shown, this embodiment provides a disc turbine impeller design method based on CFD simulation and orthogonal test, including:

[0029] The disc turbine impeller comprises a disc, a blade and an agitator shaft; the blade is arranged along the circumference of the disc; the blade is divided into an upper part and a lower part with the horizontal plane where the disc is located as a boundary; the radial extension line of the blade at the junction of the upper part and the lower part is a curve structure and satisfies the specific equation y=a·x 2 .

[0030] Determine the design goals, such as high mass transfer, high gas holdup, low power consumption, etc.; determine the number of factors that affect the design goals and the level of each factor; design and determine the orthogonal test plan, and draw a three-dimensional model of the disc turbine impeller; perform CFD simulation based on the drawn three-dimensional model to obtain the orthogonal test simulation results; determine the impeller structure corresponding to the optimal design goal based on the statistical analysis results

[0031] As a preferred implementation, the design objectives include: gas holdup, mixing time, volumetric oxygen mass transfer coefficient, monomer volumetric power input, and Ev function; the Ev function is Ev = 0.5 × normalized value of volumetric oxygen mass transfer coefficient + 0.5 × (1-normalized value of unit volumetric power input), which is expressed as a balance between the impeller oxygen mass transfer capacity and power consumption.

[0032] As a preferred implementation, factors affecting the design target include the curvature of the blade, the degree of asymmetry between the upper and lower blades, and the radial bending angle of the blade.

[0033] The level of each factor affecting the design target is set based on experience with a wide gradient. The blade curvature is given by the equation y = a·x 2 The coefficient a controls the degree of asymmetry of the upper and lower blades. Taking T15B20 as an example, T15 means that the height of the upper blade is 15 mm, and B20 means that the height of the lower blade is 20 mm. The radial bending angle of the blade, A0° means that the radial bending angle of the blade is 0°, and AM15° means that the radial bending angle of the blade is 15°, and its direction is the opposite direction of the rotation of the stirring paddle.

[0034] As a preferred implementation, the process of orthogonal test design, determining the orthogonal test scheme, and drawing the three-dimensional model of the disc turbine impeller includes:

[0035] Before the orthogonal experimental design, single-factor CFD simulation is performed based on the determined factors and their levels to obtain the optimal level of each factor for the design objective.

[0036] Based on the optimal level of each factor for the design goal, an orthogonal test design is carried out and an orthogonal test plan is determined. The basic idea of ​​an orthogonal test is to arrange the level combinations of multiple factors according to a certain rule so that the levels of each factor can appear evenly and balanced in each test. It helps to reduce the complexity and cost of the test, while being economical and efficient, and can obtain relatively comprehensive information through a smaller number of tests. Through orthogonal tests, the best combination of blade shapes for the design goal can be screened out.

[0037] Specifically, by taking the Ev function as the design target, the three factors and their levels of the blade curvature, the asymmetry of the upper and lower blades, and the radial bending angle of the blade are determined as shown in Table 1. Based on this, an orthogonal design table with three factors and three levels is designed as shown in Table 2, and the three-dimensional model of the disk turbine impeller under different cases is drawn, as shown in Table 2. Figure 2 shown.

[0038] Table 1

[0039]

[0040]

[0041] Table 2

[0042]

[0043] As a preferred implementation, the process of performing CFD simulation based on the drawn three-dimensional model and obtaining the orthogonal test simulation results includes:

[0044] The process of obtaining the orthogonal simulation results includes: naming the boundary conditions and fluid domain of the three-dimensional model of the disk turbine impeller, and then meshing; setting the initial calculation conditions, and performing calculations and solutions based on the generated mesh file and the initial calculation conditions until the torque of the impeller reaches stability and the orthogonal simulation results are obtained.

[0045] Specifically, the schematic diagram of the two-dimensional plane structure of the bioreactor for simulation is as follows Figure 3 As shown, specifically, T is the tank diameter, H is the tank height, d is the stirring shaft diameter, b is the baffle width, C is the distance between the annular distributor and the bottom of the tank, E is the distance between the impeller disk and the bottom of the tank, D is the impeller diameter, h is the blade height, and l is the blade width.

[0046] In each test scheme shown in Table 2 above, a simulation model of each test scheme is constructed by replacing the stirring blade structure to perform simulation.

[0047] Specifically, the simulation process includes:

[0048] Use Creo software to geometrically model the specific values ​​of the influencing factors of each test scheme;

[0049] The constructed geometric model was imported into Design Modeler to name the boundary conditions and fluid domains, and then imported into FLUENT MESHING for meshing. The overall mesh was polyhedral, and the impeller, inlet ring, and baffle areas were locally encrypted.

[0050] Import the generated grid file into FLUENT to set the initial calculation conditions, and then perform the calculation and solution until the calculation process reaches convergence.

[0051] After the solution is completed, the calculation results are imported into the CFD-POST software for post-processing to obtain the simulation results.

[0052] Specifically, the setting of the initial conditions for calculation includes:

[0053] The gravity is set to 9.8m / s 2 , the direction is the negative direction of the coordinate axis z-axis. The Euler-Euler multiphase flow model is used to simulate the gas-liquid two-phase. The surface tension is set to 0.073N / m, the drag model is set to the Grace model, and other interphase forces are ignored. The size of the gas phase is controlled by the PBM model, and the range is set to 0.5mm-9mm. The turbulence model is set to the standard k-ε model. The impeller area simulates the rotational motion of the impeller through a multiple reference system (MRF). The interface is set to interface, the gas inlet surface is set to velocity-inlet, the gas outlet surface is set to degassing, and the remaining boundary conditions are set to wall. The value of velocity-inlet is used as a reference for initialization, and the volume fraction of the gas phase is set to 0. The solution method uses the Phase Coupled SIMPLE algorithm, and the residual is set to 10 -5 The impeller torque is monitored during the solution process and is considered converged when stability is reached.

[0054] As a preferred implementation, based on the statistical analysis results, the process of determining the impeller structure corresponding to the optimal value of the design target includes:

[0055] The process of statistically analyzing the orthogonal simulation results and determining the blade structure of the disc turbine impeller includes: evaluating the order of influence of the three factors, namely the curvature of the blade, the asymmetry of the upper and lower blades, and the radial bending angle of the blade, on the design objectives through orthogonal simulation results and range analysis; evaluating the significance level of the influence of the three factors, namely the curvature of the blade, the asymmetry of the upper and lower blades, and the radial bending angle of the blade, on the design objectives through orthogonal simulation results and variance analysis; according to the results of the order of influence and the significance level analysis, the blade structure of the disc turbine impeller is determined with the goal of obtaining the maximum value of the design objective.

[0056] Specifically, the influence of three factors, namely, the curvature of the blade, the asymmetry of the upper and lower blades, and the radial bending angle of the blade, on the Ev function was evaluated by range analysis as shown in Table 3. The order of the influence of the three factors on Ev is: the asymmetry of the upper and lower blades > the radial bending angle of the blade > the curvature of the blade. In Table 3, K1, K2, and K3 correspond to the levels of 0.1, 0.15, and 0.2 of the coefficient a, T20B20, T15B20, and T10B20 of the blade asymmetry, and A0°, AM15°, and AM30° of the blade radial bending angles, respectively; the optimal value is determined by the average of K at each level of each factor. The Ev value in the present invention is to obtain the maximum value, so the coefficient a is determined to be 0.1 through 0.48 in Table 3, the blade asymmetry T15B20 is determined to be the best through 0.499 in Table 3, and the blade radial bending angle is determined to be AM30° through 0.491 in Table 3. In this case, the objective function Ev value is the largest, and the oxygen mass transfer capacity of the impeller and the input of the power per unit volume are optimally balanced.

[0057] Table 3

[0058]

[0059]

[0060] Specifically, the significance level of the influence of three factors, namely, the curvature of the blade, the asymmetry of the upper and lower blades, and the radial bending angle of the blade, on the Ev function was evaluated by variance analysis, as shown in Table 4. The asymmetry of the upper and lower blades and the radial bending angle of the blade were significant influencing factors of the Ev value (P<0.05), while the curvature of the blade had no significant effect on the Ev function.

[0061] Table 4

[0062]

[0063] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A disc turbine impeller design method based on CFD simulation and orthogonal test, characterized in that: The following steps are involved: Obtain the design objectives and influencing factors of the disc turbine impeller; Perform an orthogonal test design based on the design objectives and influencing factors to obtain an orthogonal test plan; Perform geometric modeling according to the data included in the orthogonal test scheme to obtain a three-dimensional model of a disc turbine impeller, and perform CFD simulation based on the three-dimensional model of the disc turbine impeller to obtain an orthogonal simulation result; The orthogonal simulation results are statistically analyzed to determine the blade structure of the disk turbine impeller.

2. The disc turbine impeller design method based on the combination of CFD simulation and orthogonal test according to claim 1 is characterized in that: The disc turbine impeller comprises a disc, blades and a stirring shaft; the blades are arranged along the circumference of the disc and are divided into an upper part and a lower part according to a horizontal plane where the disc is located; a radial extension line of the blades at the junction of the upper part and the lower part is a curve structure that satisfies a set equation; and the stirring shaft is located in the center of the disc.

3. The disc turbine impeller design method based on the combination of CFD simulation and orthogonal test according to claim 1 is characterized in that: The design target is the Ev function, where the Ev function is the balance between the impeller oxygen mass transfer capacity and power consumption, and its expression is as follows: Ev = 0.5 × normalized value of volumetric oxygen mass transfer coefficient + 0.5 × (1 - normalized value of unit volume power input).

4. The disc turbine impeller design method based on the combination of CFD simulation and orthogonal test according to claim 1 is characterized in that: Factors influencing the design objectives include the curvature of the blade, the degree of asymmetry between the upper and lower blades, and the radial bending angle of the blade.

5. The disc turbine impeller design method based on the combination of CFD simulation and orthogonal test according to claim 1 is characterized in that: Multiple level values ​​are set for each influencing factor, and single-factor CFD simulation is performed based on the influencing factor and the level value corresponding to each influencing factor to obtain the optimal level value of each influencing factor for the design target, and orthogonal experimental design is performed based on the optimal level value.

6. The disc turbine impeller design method based on the combination of CFD simulation and orthogonal test according to claim 1 is characterized in that: The process of obtaining the orthogonal simulation results includes: determining the boundary conditions and fluid domain of the three-dimensional model of the disc turbine impeller, and then meshing; setting the initial calculation conditions, and performing calculations and solutions based on the generated mesh file and the initial calculation conditions until the torque of the impeller reaches stability, and obtaining the orthogonal simulation results.

7. The disc turbine impeller design method based on the combination of CFD simulation and orthogonal test according to claim 1 is characterized in that: The process of statistically analyzing the orthogonal simulation results and determining the blade structure of the disc turbine impeller includes: evaluating the order of influence of the three factors, namely the curvature of the blade, the asymmetry of the upper and lower blades, and the radial bending angle of the blade, on the design objectives through orthogonal simulation results and range analysis; evaluating the significance level of the influence of the three factors, namely the curvature of the blade, the asymmetry of the upper and lower blades, and the radial bending angle of the blade, on the design objectives through orthogonal simulation results and variance analysis; according to the results of the order of influence and the significance level analysis, the blade structure of the disc turbine impeller is determined with the goal of obtaining the maximum value of the design objective.

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