Cooperative suppression method for impeller-guide vane flow-induced vibration

Abstract

The invention discloses an impeller-guide vane flow-induced vibration cooperative suppression method, and belongs to the field of rotary fluid mechanical vibration analysis. The method comprises the following steps: establishing a fluid domain three-dimensional model and a solid domain three-dimensional model of a target rotating machine by utilizing three-dimensional modeling software according to structural characteristic parameters of the target rotating machine, establishing an automatic process to perform grid division, performing flow field steady-state simulation analysis, and verifying grid independence and simulation accuracy; geometric parameter dimension reduction processing is carried out according to molded line characteristics; an optimization algorithm is selected, impeller and guide vane collaborative iterative optimization is carried out, and a turbo expander optimization model is obtained; results before and after optimization are compared, and the optimization effect is summarized. According to the method, the flow-induced vibration characteristics of the impeller and the guide vane can be optimized efficiently at low cost, scientific guidance is provided for impeller design and optimization, and the overall stability and reliability of large rotating equipment are improved.

Description

Technical Field

[0001] The invention belongs to the field of vibration analysis of rotating fluid machinery, and in particular relates to a method for collaboratively suppressing impeller-guide vane flow-induced vibration. Background Art

[0002] Impeller machinery is an indispensable core equipment in industries such as energy production, chemical processing, aerospace, and marine engineering. They convert energy into fluid power or pressure changes through rotating impellers. The working principle of this type of machinery usually involves converting input energy (such as electrical energy or thermal energy) into rotational kinetic energy, and then using this kinetic energy to work on the fluid (gas or liquid), thereby achieving functions such as transportation, compression, and pumping. However, due to its high-speed operation, high-temperature and high-pressure working conditions, and complex fluid-solid interaction, impeller machinery is prone to vibration problems, which not only affect the reliability and life of the equipment, but may also lead to serious safety risks and economic losses.

[0003] Studies have found that flow instability caused by fluid excitation during mechanical operation is also one of the main causes of impeller mechanical vibration. These vibrations will seriously affect the efficiency of the entire impeller mechanical system, posing a huge risk to the integrity and stable operation of the structure. The current optimization design only optimizes the impeller or guide vane separately. However, the strong dynamic and static interference effect between the impeller and the guide vane is the main cause of flow-induced vibration, and the mutual influence will lead to changes in the fluid state. Therefore, the coordinated optimization design of the impeller guide vanes can ensure the optimal vibration performance of the rotating machinery. Therefore, it is of great significance to invent a method for collaborative optimization design of impeller guide vanes to reduce flow-induced vibration. Summary of the invention

[0004] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for collaboratively suppressing flow-induced vibration of an impeller-guide vane. The present invention directly controls and optimizes the model parameters through an optimization algorithm, thereby achieving high-precision collaborative optimization of the impeller guide vanes and providing a scientific reference for the optimal design of the impeller guide vanes of the impeller machinery.

[0005] In order to achieve the above-mentioned invention object, the present invention specifically adopts the following technical solutions:

[0006] A method for collaboratively suppressing impeller-guide vane flow-induced vibration comprises the following steps:

[0007] S1. Taking the impeller and guide vane of the expansion end of the turbine expander as the target rotating machinery, a fluid domain 3D model and a solid domain 3D model of the target rotating machinery are established using 3D modeling software according to the structural characteristic parameters of the target rotating machinery;

[0008] S2. Perform finite element meshing on the three-dimensional model of the fluid domain, then import the finite element calculation mesh of the turbine expander impeller and the finite element calculation mesh of the turbine expander guide vane obtained by the finite element meshing into the fluid domain simulation software, set the fluid domain simulation conditions, obtain the fluid domain calculation model, and perform steady-state simulation on the fluid domain calculation model to obtain the fluid domain steady-state simulation results;

[0009] S3. Verify the grid independence of the fluid domain steady-state simulation results. After the grid independence verification, perform experimental measurement on the fluid domain three-dimensional model to obtain the fluid domain experimental measurement results. Compare the fluid domain experimental measurement results with the fluid domain steady-state simulation results to ensure the accuracy of the three-dimensional steady-state flow field simulation inside the turbine expander.

[0010] S4, meshing the solid domain three-dimensional model, setting solid domain simulation conditions, and obtaining a solid domain calculation model;

[0011] S5. A fluid-solid coupling calculation model is established based on the solid domain calculation model and the fluid domain calculation model. Without changing the basic structures of the fluid domain three-dimensional model and the solid domain three-dimensional model, the fluid-solid coupling calculation model is parameterized to obtain an impeller profile diagram and a guide vane profile diagram. The angle and thickness in the impeller profile diagram and the angle and thickness in the guide vane profile diagram are parameterized to obtain a parameterized model after dimensionality reduction.

[0012] S6. Using the parameterized model after dimensionality reduction, taking minimization of the flow-induced vibration intensity parameter as the optimization goal and the performance of the target rotating machinery as the constraint condition, constructing the original model of the turbine expander, and iteratively optimizing the constructed original model of the turbine expander by the optimization algorithm to obtain the optimized model of the turbine expander;

[0013] S7. Construct the bidirectional fluid-solid coupling data transfer module of CFX, Transient Structural and System Coupling in Ansys Workbench, and perform bidirectional fluid-solid coupling simulation on the optimized model of the turboexpander and the original model of the turboexpander in the bidirectional fluid-solid coupling data transfer module;

[0014] S8. Import the bidirectional fluid-solid coupling simulation results of the turbine expander optimization model and the bidirectional fluid-solid coupling simulation results of the turbine expander original model into the post-processing software for post-processing, use the impeller acceleration change at the expansion end of the turbine expander as an evaluation index, output the turbine expander optimization model whose flow-induced vibration characteristics meet the preset requirements, and realize the coordinated suppression of impeller-guide vane flow-induced vibration.

[0015] Based on the above scheme, each step can be implemented in the following preferred specific manner.

[0016] Preferably, in step S1, UG NX is used as the three-dimensional modeling software; the entire fluid calculation domain of the three-dimensional model of the fluid domain of the expansion end of the turbine expander includes four parts: impeller, guide vane, inlet pipe, and outlet pipe, and the inlet pipe and the outlet pipe are respectively extended to form an inlet extension section and an outlet extension section respectively; the three-dimensional model of the solid domain of the expansion end of the turbine expander sets the blade surface and the hub surface as the fluid-solid coupling interface, the three-dimensional model of the solid domain considers the influence of the earth's gravity and ignores the influence of mechanical vibration caused by other components, and an ideal displacement constraint is adopted at the impeller shaft hole.

[0017] Preferably, in step S2, finite element meshing of the three-dimensional model of the fluid domain is implemented by Turbo Grid and ICEM, the fluid domain simulation software adopts CFD simulation software, and the fluid domain simulation conditions include fluid material properties, turbulence model, inlet boundary conditions, outlet boundary conditions, impeller flow domain rotation speed, dynamic and static interface, wall setting and calculation steps.

[0018] Preferably, in step S3, firstly, an initial grid model is established and a simulation is performed, and then the grid is gradually encrypted, and the simulation is rerun after each mesh encryption to complete the grid independence verification of the steady-state simulation results of the fluid domain; the measured outlet pressure, inlet pressure, outlet temperature and inlet temperature are obtained from the fluid domain experimental measurement results, the isentropic efficiency is calculated based on the measured outlet pressure, inlet pressure, outlet temperature and inlet temperature, and the isentropic efficiency calculation result is used as the measured isentropic efficiency, the simulated outlet pressure, inlet pressure, outlet temperature and inlet temperature are obtained from the fluid domain steady-state simulation results, the isentropic efficiency is recalculated based on the simulated outlet pressure, inlet pressure, outlet temperature and inlet temperature, and the isentropic efficiency calculation result is used as the simulated isentropic efficiency, and the isentropic efficiency relative error between the measured isentropic efficiency and the simulated isentropic efficiency is calculated, if the isentropic efficiency relative error is less than the preset accuracy threshold, it means that the three-dimensional steady-state flow field simulation inside the turbine expander is correct; otherwise, the fluid domain steady-state simulation results are reacquired until the three-dimensional steady-state flow field simulation inside the turbine expander is correct.

[0019] Preferably, the isentropic efficiency η is calculated by the following formula:

[0020]

[0021] Where κ is the gas constant of superheated steam; P in is the inlet pressure, P out is the outlet pressure, T in is the inlet temperature, T out is the outlet temperature.

[0022] Preferably, in step S4, the mesh size when the fluid domain three-dimensional model is meshed by finite element is used as a benchmark, and the solid domain three-dimensional model is meshed using the Ansys meshing tool in ANSYS Mechanical. The solid domain three-dimensional model is meshed using a tetrahedral mesh structure, and the solid domain simulation conditions include solid material properties, constraints, gravity settings, calculation time, calculation step size and fluid-solid coupling interface settings.

[0023] Preferably, in step S5, the Blade Editor in the Design Modeler software is used for parameterization, and a plurality of sections are equally spaced between the hub surface and the cover surface in the impeller profile diagram, and each section corresponds to an angle curve of the following form:

[0024] Y Angle =AP M 2 +C

[0025] Where Y Angle Represents the angle curve matrix of each section, P M is the curve position matrix, A=[a 1 ,a 2 ,…,a m ] and C=[c 1 ,c 2 ,…,c m ] are coefficient matrices used to divide the number of cross sections; a 1 ,a 2 ,…,a m and c 1 ,c 2 ,…,c m are the elements in the coefficient matrices A and C respectively; m represents the number of cross sections;

[0026] Then the first point of the hub surface is taken as the first reference point, and the last point of the hub surface is taken as the second reference point. On the angle curve corresponding to the hub surface, the angle values ​​of the first reference point and the second reference point are used as variables. When the angle values ​​of the first reference point and the second reference point change, the two angle values ​​are substituted into the angle curve corresponding to the hub surface to obtain the optimized angle curve y corresponding to the hub surface. 1 ' _Angle :

[0027] y 1 ' _Angle =a 1 ′p M +c 1 '

[0028] In the formula, a 1 ′ and c1 ′ is the quadratic coefficient of the optimized angle curve corresponding to the hub surface; p M Indicates the horizontal coordinate value of the angle curve corresponding to the hub surface;

[0029] Except for the hub surface, the quadratic coefficients of the remaining sections are determined by the following formula:

[0030]

[0031] In the formula, a n ′ and c n ′ are the quadratic coefficients of the angle curve after optimization of the nth section; a n and c n are the quadratic coefficients of the angle curve of the nth section respectively.

[0032] Preferably, in step S6, the optimization algorithm is a particle swarm algorithm, and the equivalent entropy efficiency of the turbine expander is greater than 80% as a constraint condition to minimize the unevenness of the flow velocity V at the expander outlet. s To optimize the goal:

[0033]

[0034] In the formula, v k represents the speed of the kth exit node; v is the average exit speed; K is the total number of exit nodes.

[0035] Preferably, in the bidirectional fluid-solid coupling data transmission module of step S7, the solid domain calculation model, the fluid domain calculation model and the time step, the number of calculation steps and the calculation time set in System Coupling are kept consistent, and the time for the impeller at the expansion end of the turbine expander to rotate 3° is used as the time step.

[0036] Preferably, in step S8, the post-processing software outputs a time domain graph of acceleration change of the turbine expander optimization model and a time domain graph of acceleration change of the turbine expander original model, and a frequency spectrum graph of acceleration change of the turbine expander optimization model and a frequency spectrum graph of acceleration change of the turbine expander original model are obtained from the time domain graph of acceleration change of the turbine expander optimization model and the time domain graph of acceleration change of the turbine expander original model. The two frequency spectrum graphs are correspondingly used as a first frequency spectrum graph and a second frequency spectrum graph. When the acceleration amplitude of the impeller radial vibration direction at the peak frequency in the first frequency spectrum graph is less than the acceleration amplitude of the impeller radial vibration direction at the peak frequency in the second frequency spectrum graph and the acceleration amplitude difference between the two is less than a preset acceleration amplitude threshold, it indicates that the flow-induced vibration characteristics of the turbine expander optimization model meet the requirements.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention provides a method for collaboratively suppressing flow-induced vibration of an impeller and a guide vane. The dynamic-static interference effect between an impeller and a guide vane will cause strong vibration of a rotating machine, while the current optimization design only optimizes the impeller or the guide vane separately, and cannot effectively suppress the flow-induced vibration. The method of the present invention introduces a bidirectional fluid-solid coupling analysis, conducts an in-depth study on the dynamic-static interference effect between the impeller and the guide vane, and considers the mutual influence between the two in the design stage, thereby achieving more accurate and effective optimization. Furthermore, the dimensionality reduction processing of geometric parameters is adopted to reduce the computational complexity and improve the simulation efficiency. In addition, by selecting a suitable optimization algorithm and building a simulation optimization module, the collaborative iterative optimization of the impeller and the guide vane is achieved. This method can not only improve the flow-induced vibration characteristics of the impeller and the guide vane efficiently and at low cost, but also provide scientific guidance for the design of rotating machinery. At the same time, it helps to improve the overall stability and reliability of large rotating machinery, thereby extending the life of the equipment, reducing maintenance costs, and reducing safety hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a flow chart of the method of the present invention;

[0040] Figure 2 Schematic diagram of a fluid domain three-dimensional model and a solid domain three-dimensional model of an expansion end of a turbine expander provided in an embodiment of the present invention; wherein (a) is a schematic diagram of a fluid domain three-dimensional model, and (b) is a schematic diagram of a solid domain three-dimensional model;

[0041] Figure 3 A schematic diagram of a finite element calculation grid for a turbine expander impeller and a finite element calculation grid for a turbine expander guide vane provided in an embodiment of the present invention;

[0042] Figure 4 The result diagram of parameterizing the turbine expander impeller according to the embodiment of the present invention; wherein (a) is the impeller profile diagram, (b) is the angle result diagram of each section in the impeller profile diagram, and (c) is the thickness result diagram of each section in the impeller profile diagram;

[0043] Figure 5 A schematic diagram of a bidirectional fluid-solid coupling data transmission path provided in an embodiment of the present invention;

[0044] Figure 6 The time domain diagram and spectrum diagram of impeller flow-induced vibration before and after optimization provided by the embodiment of the present invention; wherein (a) is a time domain diagram of acceleration change of the original model of the turbine expander, (b) is a time domain diagram of acceleration change of the optimized model of the turbine expander, (c) is a spectrum diagram of acceleration change of the original model of the turbine expander, and (d) is a spectrum diagram of acceleration change of the optimized model of the turbine expander;

[0045] Figure 7A schematic diagram showing a comparison of flow-induced vibration intensity before and after optimization provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0047] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinguishing descriptions, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0048] The present invention provides a method for collaboratively suppressing flow-induced vibration of an impeller and guide vanes, which is used to optimize the design of impellers and guide vanes in rotating machinery. Specifically, it can be used to analyze and optimize the vibration intensity of impeller guide vanes caused by the fluid. For example, the impeller guide vanes at the expansion end of a turbine expander can be collaboratively optimized to reduce flow-induced vibration, and the vibration caused by the interaction between other internal components of the impeller machinery can also be optimized.

[0049] like Figure 1 As shown, in a preferred implementation of the present invention, in this embodiment, the expansion end impeller of the turbine expander is selected for collaborative optimization to reduce its flow-induced vibration intensity, and the above-mentioned impeller-guide vane flow-induced vibration collaborative suppression method is used for analysis. The method includes the following steps S1 to S8, and the specific implementation process is described in detail below.

[0050] S1. The impeller and guide vane at the expansion end of the turbine expander are taken as the target rotating machinery. According to the structural characteristic parameters of the target rotating machinery analyzed, a fluid domain three-dimensional model and a solid domain three-dimensional model of the target rotating machinery are established using three-dimensional modeling software.

[0051] It should be noted that, in step S1 of the present invention, the impeller and guide vane of the expansion end of the turbine expander are taken as the target rotating machinery, and the three-dimensional modeling software UG NX is used to establish the fluid domain three-dimensional model and the solid domain three-dimensional model of the expansion end of the turbine expander according to the structural characteristic parameters of the impeller and the guide vane.

[0052] In step S1 of this embodiment, Figure 2As shown in (a), the three-dimensional model of the fluid domain at the expansion end of the turbine expander. The entire fluid calculation domain includes four parts: impeller, guide vane, inlet pipe, and outlet pipe. The inlet pipe and outlet pipe are extended to form an inlet extension section and an outlet extension section to ensure that the boundary conditions have no effect on the numerical results in the fluid calculation domain. Figure 2 As shown in (b), the solid domain three-dimensional model of the expansion end of the turbine expander sets the blade surface and the hub surface as the fluid-solid coupling interface. The solid domain three-dimensional model takes into account the influence of the earth's gravity and ignores the mechanical vibration influence of other components. An ideal displacement constraint is used at the impeller shaft hole, that is, its displacement in the XYZ directions is limited.

[0053] S2. Perform finite element meshing on the three-dimensional model of the fluid domain, then import the finite element calculation mesh of the turbine expander impeller and the finite element calculation mesh of the turbine expander guide vane obtained by the finite element meshing into the fluid domain simulation software, set the fluid domain simulation conditions, obtain the fluid domain calculation model, and perform steady-state simulation on the fluid domain calculation model to obtain the fluid domain steady-state simulation results.

[0054] It should be noted that in step S2 of the present invention, finite element meshing of the fluid domain three-dimensional model is implemented by Turbo Grid and ICEM, the fluid domain simulation software adopts CFD simulation software, and the fluid domain simulation conditions include fluid material properties, turbulence model, inlet boundary conditions, outlet boundary conditions, impeller flow domain rotation speed, dynamic and static interface, wall setting and calculation steps.

[0055] In step S2 of this embodiment, the models corresponding to the impeller and guide vane of the turbine expander are converted to TurboGrid for meshing, and the geometric models corresponding to the inlet pipe, the inlet extension section, the outlet pipe and the outlet extension section are meshed in ICEM-CFD. In order to meet the requirements of flow field analysis, the four parts of the fluid calculation domain are all converted into structured hexahedral units, and the generated turbine expander impeller finite element calculation grid and turbine expander guide vane finite element calculation grid are as follows: Figure 3 shown. Figure 3 The upper middle part is the finite element calculation mesh of the turbine expander guide vane, and the lower part is the finite element calculation mesh of the turbine expander impeller. At the same time, the mesh quality is strictly controlled to ensure the reliability of the numerical calculation. Dense meshes are arranged near the blade wall and guide vane wall to establish the boundary layer and capture the complex flow structure.

[0056] In step S2 of this embodiment, CFD simulation software is used to perform steady-state simulation on the fluid domain calculation model under rated design conditions, and the RNG k-ε model is selected as the turbulence model for steady flow field calculation. The impeller area of ​​the turbine expander rotates at a speed of 24500 rpm, and the remaining areas are stationary. The medium is compressible superheated water vapor. The rated mass flow rate of 100 t / h and the temperature of 698.15 K are used as inlet boundary conditions at the inlet, and the pressure of 2.2 MPa is used as the outlet boundary condition at the outlet.

[0057] S3. Verify the grid independence of the fluid domain steady-state simulation results. After the grid independence verification, perform experimental measurement on the fluid domain three-dimensional model to obtain the fluid domain experimental measurement results. Compare the fluid domain experimental measurement results with the fluid domain steady-state simulation results to ensure the accuracy of the three-dimensional steady-state flow field simulation inside the turbine expander.

[0058] It should be noted that, in step S3, the initial grid model is first established and the simulation is performed, and then the grid is gradually encrypted. The simulation is rerun after each mesh encryption to complete the grid independence verification of the steady-state simulation results of the fluid domain.

[0059] It should be noted that in step S3, in order to study the independence of the steady-state simulation results of the fluid domain, five prototype grids of different sizes were generated and calculated under the rated operating conditions. As can be seen from Table 1, with the increase of the number of grids, the outlet temperature T out With inlet pressure P in The value of gradually stabilizes, and the outlet temperature T between Scheme 3 and the subsequent Schemes 4 and 5 is out and inlet pressure P in The difference is very small and can be ignored. Therefore, considering the calculation accuracy and computing resources, the grid number of the fluid domain 3D model is set to 2.45×10 6 elements.

[0060] Table 1. Grid independence verification

[0061]

[0062] Experiments were conducted on the three-dimensional model of the fluid domain to verify the accuracy of the numerical method of the present invention. Specifically, the measured outlet pressure, inlet pressure, outlet temperature and inlet temperature are obtained from the experimental measurement results of the fluid domain, the isentropic efficiency is calculated based on the measured outlet pressure, inlet pressure, outlet temperature and inlet temperature, and the isentropic efficiency calculation result is used as the measured isentropic efficiency, the simulated outlet pressure, inlet pressure, outlet temperature and inlet temperature are obtained from the steady-state simulation results of the fluid domain, the isentropic efficiency is recalculated based on the simulated outlet pressure, inlet pressure, outlet temperature and inlet temperature, and the isentropic efficiency calculation result is used as the simulated isentropic efficiency, and the relative error of the isentropic efficiency between the measured isentropic efficiency and the simulated isentropic efficiency is calculated. If the relative error of the isentropic efficiency is less than the preset accuracy threshold, it means that the three-dimensional steady-state flow field simulation inside the turbine expander is correct; otherwise, the fluid domain steady-state simulation results are re-obtained until the three-dimensional steady-state flow field simulation inside the turbine expander is correct.

[0063] In this embodiment, given the rated working conditions, the experimental test data of the three-dimensional model of the fluid domain fits well with the numerical results. Under the design conditions, the outlet temperature error is 0.63%, the inlet pressure error is 0.28%, and the isentropic efficiency relative error is 4.69%. Since the numerical calculation does not take into account factors such as gap leakage and mechanical friction loss, and the boundary conditions set in the rated working conditions are not completely consistent with the test results, there is a deviation between the numerical results and the experimental results. The overall calculation error basically meets the accuracy requirements, indicating that the numerical method used in the present invention is acceptable.

[0064] Further, the isentropic efficiency η is calculated by the following formula:

[0065]

[0066] Wherein, κ is the gas constant of superheated steam, which is 1.33 in this embodiment; P in is the inlet pressure, P out is the outlet pressure, T in is the inlet temperature, T out is the outlet temperature.

[0067] S4. Meshing the solid domain three-dimensional model, setting solid domain simulation conditions, and obtaining a solid domain calculation model.

[0068] It should be noted that in step S4, the solid domain 3D model is meshed according to the fluid-solid coupling theory while ensuring the quality of the mesh mapping of the fluid-solid coupling interface. Specifically, the coupling strategy of CFX+ANSYS Mechanical+SystemCoupling is adopted, which is based on the mapping relationship of nodes. In order to ensure the quality of the mesh mapping of the fluid-solid coupling interface, the pressure at the node i on the known fluid domain mesh is Pfi , determine a circular area with a radius of r with the jth node on the solid domain grid as the center, and find the n nodes corresponding to the circular area on the fluid domain grid. At this time, the pressure P at the node j on the solid domain grid is sj It can be expressed as:

[0069]

[0070] Where, d i is the spatial distance between the i-th node of the fluid domain mesh and the j-th node of the solid domain mesh.

[0071] The excitation load at node j on the solid domain mesh is calculated as follows:

[0072] F sj =∫ S P sj dS

[0073] Where S represents the finite element mesh area at the jth node of the solid domain mesh.

[0074] From the above theory, it can be known that the mesh size of the fluid-solid coupling interface should be as close as possible to achieve a better coupling effect and improve simulation accuracy and speed. Therefore, the mesh size when the finite element meshing of the fluid domain three-dimensional model is used as a benchmark, and the Ansys meshing tool in ANSYS Mechanical is used to mesh the solid domain three-dimensional model. Due to the huge amount of calculation of bidirectional fluid-solid coupling, a tetrahedral mesh structure is used to improve calculation efficiency; the solid domain simulation conditions include solid material properties, constraints, gravity settings, calculation time, calculation step size and fluid-solid coupling interface settings.

[0075] S5. A fluid-solid coupling calculation model is established based on the solid domain calculation model and the fluid domain calculation model. Without changing the basic structure of the fluid domain three-dimensional model and the solid domain three-dimensional model, the fluid-solid coupling calculation model is parameterized to obtain the impeller profile diagram and the guide vane profile diagram. The angle and thickness in the impeller profile diagram and the angle and thickness in the guide vane profile diagram are parameterized and modeled to obtain a parameterized model after dimensionality reduction.

[0076] It should be noted that in step S5, the Blade Editor in the Design Modeler software is used for parameterization, and the impeller and guide vane are parameterized and modeled by the angle-thickness method in the Blade Editor. The angle refers to the angle between the tangent along the camber angle of the impeller airfoil and the axial direction of the turbine at any point, and the thickness is defined as the maximum distance between the upper surface and the lower surface of the impeller airfoil.

[0077] In this embodiment, the impeller profile diagram is as follows: Figure 4 As shown in (a), in order to ensure the accuracy of parametric modeling, the present invention divides nine sections from the hub surface (span = 0) to the cover surface (span = 1) at equal intervals, and the angle curve of each section is as follows: Figure 4 (b) shows that the thickness curve of each section is Figure 4 (c) is shown. Eight control points are used on each section's impeller angle curve and impeller thickness curve to generate the impeller airfoil spline curve. Therefore, in the optimization design process, the impeller airfoil can be changed by changing the horizontal and vertical coordinate values ​​of each control point. In order to ensure the uniform distribution of control points, the relative positions of the control points will not change during the optimization design process. This means Figure 4 (b) with Figure 4 (c) The horizontal axis value remains unchanged.

[0078] It should be noted that in step S5, considering that the specific process of parameterizing the angle and thickness in the impeller profile diagram and the angle and thickness in the guide vane profile diagram is similar, the following is a specific description of the parameterized modeling of the angle in the impeller profile diagram as an example. First, curve fitting is performed on the control point distribution of the impeller angle. This embodiment specifically uses the quadratic fitting formula with the symmetry axis as the y-axis for fitting, and the regression coefficient R of each section is 2 All of them are greater than 0.96, indicating that the fitting effect is good. Other fitting formula forms can also be selected here, as long as the cross-sectional regression coefficient R 2 It only needs to meet the preset accuracy requirements. Each section corresponds to an angle curve, which can be expressed as:

[0079] Y Angle =AP M 2 +C

[0080] Where Y Angle Represents the angle curve matrix of each section, P M is the curve position matrix, A=[a 1 ,a 2 ,…,a m ] and C=[c 1 ,c 2 ,…,c m ] is the coefficient matrix used to divide the number of cross sections; a 1 ,a 2 ,…,a m and c 1 ,c 2 ,…,c m are the elements in the coefficient matrices A and C respectively; m represents the number of sections.

[0081] Then, the first point (M-Prime=0) of the hub surface (Span=0) is used as the first reference point, and the last point (M-Prime=3.68) of the hub surface (Span=0) is used as the second reference point. 1 and the angle θ of the second reference point 2 is a variable, when the angle value θ of the first reference point 1 and the angle θ of the second reference point 2 When the angle changes, substitute the two angle values ​​into the angle curve corresponding to the hub surface to obtain the optimized angle curve corresponding to the hub surface:

[0082] y 1 ' _Angle =a 1 ′p M +c 1 '

[0083] In the formula, a 1 ′ and c 1 ′ is the quadratic coefficient of the optimized angle curve corresponding to the hub surface; p M Indicates the horizontal coordinate value of the angle curve corresponding to the hub surface;

[0084] Except for the hub surface, the quadratic coefficients of the remaining sections are determined by the following formula:

[0085]

[0086] In the formula, a n ′ and c n ′ are the quadratic coefficients of the angle curve after optimization of the nth section; a n and c n are the quadratic coefficients of the angle curve of the nth section respectively.

[0087] Therefore, the angle curve equations of all sections in the impeller profile diagram can be obtained. Since the horizontal coordinate value of each section remains unchanged during the optimization process, the angle value of the control point after the change can be obtained by substituting the corresponding angle curve equation. In this way, the impeller profile angle is parametrically modeled and the parameters are geometrically reduced.

[0088] When performing parametric modeling on the thickness in the impeller profile diagram, it is only necessary to replace the "impeller angle" in the above process with "impeller thickness". Specifically, firstly, curve fitting is performed on the distribution of control points of the impeller thickness, and a thickness curve is obtained for each section. Then, the thickness value of the first reference point and the thickness value of the second reference point are used as variables on the thickness curve corresponding to the hub surface. According to the above process, the optimized thickness curve corresponding to the hub surface is obtained, and then the coefficients of the remaining sections are determined to achieve parametric modeling of the impeller profile thickness.

[0089] When parameterizing the angle or thickness in the guide vane profile diagram, it is only necessary to replace the "impeller angle" in the above process with "guide vane angle" and the "impeller thickness" with "guide vane thickness". The specific process will not be repeated here.

[0090] S6. Using the parameterized model after dimensionality reduction, with minimizing the parameter that can measure the flow-induced vibration intensity as the optimization goal and the performance of the target rotating machinery as the constraint condition, the original model of the turbine expander is constructed, and the optimization algorithm is used to iteratively optimize the constructed original model of the turbine expander to obtain the optimized model of the turbine expander.

[0091] It should be noted that in step S6, the optimization algorithm is a particle swarm optimization algorithm, which usually exhibits a fast convergence speed and effectively solves nonlinear problems. s To optimize the goal:

[0092]

[0093] In the formula, v k represents the speed of the kth exit node; v is the average exit speed; K is the total number of exit nodes.

[0094] In this embodiment, the joint simulation technology of Matlab and Ansys software is used to achieve the optimal design of the internal flow characteristics of fluid machinery. In this process, a method of directly modifying the guide vanes and impeller contours is used to optimize the structure. First, the position of the particle swarm is initialized in the Matlab environment. Then, based on the parametric modeling method in the previous steps, the variables in the optimization algorithm are converted into specific geometric parameters, and imported into the Ansys software for geometric shape update and meshing. Subsequently, finite element analysis (FEA) is performed based on the updated geometric model to evaluate the flow-induced vibration under different design schemes. After completing the finite element simulation, key performance indicators are extracted from the simulation results and fed back to the particle swarm optimization algorithm in Matlab as the fitness function value. This cyclic iterative process will continue until the preset convergence criterion is met, that is, the change in the optimal solution does not exceed 10 in ten consecutive iteration cycles. -4 .

[0095] In this embodiment, the intensity of unsteady pressure fluctuation is often used as a key indicator to measure the performance of water-induced vibration. The flow uniformity at the impeller outlet is directly related to the formation and evolution of the unsteady flow structure inside the expander. Based on this, the present invention uses the flow velocity non-uniformity at the expander outlet to quantify the flow-induced vibration intensity.

[0096] It is worth noting that while pursuing the optimization of flow-induced vibration performance, the thermal performance of the turboexpander must be taken into account to avoid its deterioration due to the adjustment of geometric features. To this end, the present invention sets a clear constraint condition: the isentropic efficiency of the turboexpander must be greater than 80%. In summary, the present invention aims to explore and construct a turboexpander optimization model that can minimize flow-induced vibration under the design condition of meeting the isentropic efficiency requirement (not less than 80%).

[0097] S7. Construct the bidirectional fluid-solid coupling data transfer module of CFX, Transient Structural and System Coupling in Ansys Workbench, and perform bidirectional fluid-solid coupling simulation on the optimized model of the turbine expander and the original model of the turbine expander in the bidirectional fluid-solid coupling data transfer module.

[0098] It should be noted that in step S7, a CFX+TransientStructural+System Coupling bidirectional fluid-structure coupling data transfer module is constructed in Ansys Workbench. The data transfer path is as follows: Figure 5 As shown, a bidirectional fluid-solid coupling simulation is performed. In order to simulate the real flow field inside the turbine expander before and after optimization, so as to facilitate the convergence of transient calculations, after the steady-state calculation is completed, the steady-state calculation results are used as the transient initial conditions. The unsteady analysis is still based on the commercial software CFX, and the mesh deformation is turned on in the rotating area to achieve the purpose of bidirectional fluid-solid coupling. In the bidirectional fluid-solid coupling setting, the solid domain calculation model, the fluid domain calculation model and the time step, number of calculation steps and calculation time set in System Coupling are consistent; the iteration limit of each time step is set to 20 steps, and the convergence tolerance is set to 1×10 -4 , the transient rotor model is selected for the dynamic and static interface of the flow field, and the other boundary conditions are consistent with the steady-state calculation; the time for the impeller at the expansion end of the turbine expander to rotate 3° is taken as the time step. Since the speed of the turbine expander is 24500r / min, the time step is 2.04×10 -5 s, that is, 120 time steps are one rotation period, the total sampling time is 15 rotation periods, the total number of time steps is 1800, and the total simulation time is 0.03672s.

[0099] S8. Import the bidirectional fluid-solid coupling simulation results of the turbine expander optimization model and the bidirectional fluid-solid coupling simulation results of the turbine expander original model into the post-processing software for post-processing, use the impeller acceleration change at the expansion end of the turbine expander as an evaluation index, output the turbine expander optimization model whose flow-induced vibration characteristics meet the preset requirements, and realize the coordinated suppression of impeller-guide vane flow-induced vibration.

[0100] In this embodiment, in order to measure the vibration of the impeller, the acceleration change of the impeller is used as an evaluation index, and the acceleration change time domain diagram of the turboexpander optimization model is output by the post-processing software (i.e. Figure 6 The acceleration time domain of the optimized model in the figure) and the acceleration time domain diagram of the original model of the turbo expander (i.e. Figure 6 The baseline model acceleration time domain in , such as Figure 6 As shown. Figure 6 It can be seen that the vibrations in the X and Y directions are both radial vibrations, and their vibration amplitudes and laws are almost the same. In contrast, the vibration in the Z direction is an axial vibration, and due to the constraints, its vibration amplitude is much lower than the radial vibration. Therefore, in the impeller flow-induced vibration, radial vibration occupies a dominant position. Then, the acceleration change spectrum diagram of the turbine expander optimization model (i.e., Figure 6 The acceleration spectrum of the optimized model in the figure) and the acceleration change spectrum of the original model of the turbo expander (i.e. Figure 6 The baseline model acceleration spectrum in ), the two frequency domain graphs are correspondingly regarded as the first spectrum graph and the second spectrum graph. Figure 6 (c) and Figure 6 (d) Data analysis shows that the radial vibration of the impeller is mainly 2f GV is the main characteristic frequency, and at f GV The peak value also appears at f. In contrast, the axial vibration of the impeller is only at f. GV There is a peak value.

[0101] When the acceleration amplitude of the impeller radial vibration direction at the peak frequency in the first spectrum graph is smaller than the acceleration amplitude of the impeller radial vibration direction at the peak frequency in the second spectrum graph and the acceleration amplitude difference between the two is smaller than the preset acceleration amplitude threshold, it indicates that the flow-induced vibration characteristics of the turbine expander optimization model meet the requirements.

[0102] In this embodiment, in order to further quantify the vibration changes before and after optimization, this embodiment compares the acceleration amplitudes at the peak frequencies in the above directions. The results are as follows: Figure 7 As shown. Figure 7 It can be seen that the amplitude of radial vibration is significantly reduced, and the acceleration amplitude of the turboexpander optimization model is reduced by 916.7m / s 2, the decrease ratio reached 74.3%. According to the previous analysis, radial vibration dominates the overall flow-induced vibration of the impeller. Therefore, by optimizing the radial vibration, the overall vibration level of the expander is significantly reduced. It should be noted that in some specific positions, the vibration amplitude has increased slightly, but it still has little effect on the overall vibration. This phenomenon is due to the consideration of the global effect during the optimization process, and appropriate compromises are made to the local optimum. This result once again verifies the effectiveness and rationality of the method of the present invention.

[0103] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A method for collaboratively suppressing impeller-guide vane flow-induced vibration, characterized in that: The following steps are involved: S1. Taking the impeller and guide vane of the expansion end of the turbine expander as the target rotating machinery, a fluid domain 3D model and a solid domain 3D model of the target rotating machinery are established using 3D modeling software according to the structural characteristic parameters of the target rotating machinery; S2. Perform finite element meshing on the three-dimensional model of the fluid domain, then import the finite element calculation mesh of the turbine expander impeller and the finite element calculation mesh of the turbine expander guide vane obtained by the finite element meshing into the fluid domain simulation software, set the fluid domain simulation conditions, obtain the fluid domain calculation model, and perform steady-state simulation on the fluid domain calculation model to obtain the fluid domain steady-state simulation results; S3. Verify the grid independence of the fluid domain steady-state simulation results. After the grid independence verification, perform experimental measurement on the fluid domain three-dimensional model to obtain the fluid domain experimental measurement results. Compare the fluid domain experimental measurement results with the fluid domain steady-state simulation results to ensure the accuracy of the three-dimensional steady-state flow field simulation inside the turbine expander. S4, meshing the solid domain three-dimensional model, setting solid domain simulation conditions, and obtaining a solid domain calculation model; S5. A fluid-solid coupling calculation model is established based on the solid domain calculation model and the fluid domain calculation model. Without changing the basic structures of the fluid domain three-dimensional model and the solid domain three-dimensional model, the fluid-solid coupling calculation model is parameterized to obtain an impeller profile diagram and a guide vane profile diagram. The angle and thickness in the impeller profile diagram and the angle and thickness in the guide vane profile diagram are parameterized to obtain a parameterized model after dimensionality reduction. S6. Using the parameterized model after dimensionality reduction, taking minimization of the flow-induced vibration intensity parameter as the optimization goal and the performance of the target rotating machinery as the constraint condition, constructing the original model of the turbine expander, and iteratively optimizing the constructed original model of the turbine expander by the optimization algorithm to obtain the optimized model of the turbine expander; S7. Construct the bidirectional fluid-solid coupling data transfer module of CFX, Transient Structural and System Coupling in Ansys Workbench, and perform bidirectional fluid-solid coupling simulation on the optimized model of the turboexpander and the original model of the turboexpander in the bidirectional fluid-solid coupling data transfer module; S8. Import the bidirectional fluid-solid coupling simulation results of the turbine expander optimization model and the bidirectional fluid-solid coupling simulation results of the turbine expander original model into the post-processing software for post-processing, use the impeller acceleration change at the expansion end of the turbine expander as an evaluation index, output the turbine expander optimization model whose flow-induced vibration characteristics meet the preset requirements, and realize the coordinated suppression of impeller-guide vane flow-induced vibration.

2. A method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 1, characterized in that: In step S1, UG NX is used as the three-dimensional modeling software; the entire fluid calculation domain of the three-dimensional model of the fluid domain of the expansion end of the turbine expander includes four parts: impeller, guide vane, inlet pipe, and outlet pipe, and the inlet pipe and the outlet pipe are respectively extended to form an inlet extension section and an outlet extension section respectively; the three-dimensional model of the solid domain of the expansion end of the turbine expander sets the blade surface and the hub surface as the fluid-solid coupling interface, the three-dimensional model of the solid domain considers the influence of the earth's gravity and ignores the influence of mechanical vibration generated by other components, and an ideal displacement constraint is used at the impeller shaft hole.

3. The method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 1, characterized in that: In step S2, finite element meshing of the three-dimensional model of the fluid domain is implemented by Turbo Grid and ICEM, the fluid domain simulation software adopts CFD simulation software, and the fluid domain simulation conditions include fluid material properties, turbulence model, inlet boundary conditions, outlet boundary conditions, impeller flow domain rotation speed, dynamic and static interface, wall setting and calculation steps.

4. A method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 3, characterized in that: In step S3, firstly, an initial grid model is established and simulation is performed, and then the grid is gradually encrypted. After each mesh encryption, the simulation is rerun to complete the grid independence verification of the steady-state simulation results of the fluid domain; The measured outlet pressure, inlet pressure, outlet temperature and inlet temperature are obtained from the fluid domain experimental measurement results, the isentropic efficiency is calculated based on the measured outlet pressure, inlet pressure, outlet temperature and inlet temperature, and the isentropic efficiency calculation result is used as the measured isentropic efficiency, the simulated outlet pressure, inlet pressure, outlet temperature and inlet temperature are obtained from the fluid domain steady-state simulation results, the isentropic efficiency is recalculated based on the simulated outlet pressure, inlet pressure, outlet temperature and inlet temperature, and the isentropic efficiency calculation result is used as the simulated isentropic efficiency, and the isentropic efficiency relative error between the measured isentropic efficiency and the simulated isentropic efficiency is calculated. If the isentropic efficiency relative error is less than the preset accuracy threshold, it means that the three-dimensional steady-state flow field simulation inside the turbine expander is correct; otherwise, the fluid domain steady-state simulation results are re-obtained until the three-dimensional steady-state flow field simulation inside the turbine expander is correct.

5. A method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 4, characterized in that: The isentropic efficiency η is calculated by the following formula: Where κ is the gas constant of superheated steam; P in is the inlet pressure, P out is the outlet pressure, T in is the inlet temperature, T out is the outlet temperature.

6. A method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 1, characterized in that: In step S4, the mesh size when the finite element meshing of the fluid domain three-dimensional model is used as a benchmark, and the solid domain three-dimensional model is meshed using the Ansys meshing tool in ANSYS Mechanical. The tetrahedral mesh structure is used when the solid domain three-dimensional model is meshed. The solid domain simulation conditions include solid material properties, constraints, gravity settings, calculation time, calculation step size and fluid-solid coupling interface settings.

7. A method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 1, characterized in that: In step S5, the Blade Editor in the Design Modeler software is used for parameterization, and multiple sections are equally spaced between the hub surface and the cover surface in the impeller profile diagram. Each section corresponds to an angle curve of the following form: AND Angle =AP M 2 +C Where Y Angle Represents the angle curve matrix of each section, P M is the curve position matrix, A=[a1,a2,…,a m ] and C=[c1,c2,…,c m ] are coefficient matrices used to divide the number of cross sections; a1, a2, …, a m and c1,c2,…,c m are the elements in the coefficient matrices A and C respectively; m represents the number of cross sections; Then the first point of the hub surface is taken as the first reference point, and the last point of the hub surface is taken as the second reference point. On the angle curve corresponding to the hub surface, the angle values ​​of the first reference point and the second reference point are used as variables. When the angle values ​​of the first reference point and the second reference point change, the two angle values ​​are substituted into the angle curve corresponding to the hub surface to obtain the optimized angle curve y1′ corresponding to the hub surface. _Angle : y1′ _Angle =a1′p M +c1′ Where a1′ and c1′ are the quadratic coefficients of the optimized angle curve corresponding to the hub surface; p M Indicates the horizontal coordinate value of the angle curve corresponding to the hub surface; Except for the hub surface, the quadratic coefficients of the remaining sections are determined by the following formula: In the formula, a n ′ and c n ′ are the quadratic coefficients of the angle curve after optimization of the nth section; a n and c n are the quadratic coefficients of the angle curve of the nth section respectively.

8. The method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 1, characterized in that: In step S6, the optimization algorithm is a particle swarm algorithm, and the equivalent entropy efficiency of the turbine expander is greater than 80% as a constraint condition to minimize the unevenness of the expander outlet flow rate V s To optimize the goal: In the formula, v k represents the speed of the kth exit node; is the average export speed; K is the total number of export nodes.

9. The method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 1, characterized in that: In the bidirectional fluid-solid coupling data transmission module of step S7, the solid domain calculation model, the fluid domain calculation model and the time step, the number of calculation steps and the calculation time set in System Coupling are consistent, and the time for the impeller at the expansion end of the turbine expander to rotate 3° is used as the time step.

10. The method for cooperatively suppressing impeller-guide vane flow-induced vibration according to claim 1, characterized in that: In step S8, the post-processing software outputs a time domain graph of acceleration change of the turbine expander optimization model and a time domain graph of acceleration change of the turbine expander original model, and a frequency spectrum graph of acceleration change of the turbine expander optimization model and a frequency spectrum graph of acceleration change of the turbine expander original model are obtained from the time domain graph of acceleration change of the turbine expander optimization model and the time domain graph of acceleration change of the turbine expander original model. The two frequency spectrum graphs are correspondingly used as a first frequency spectrum graph and a second frequency spectrum graph. When the acceleration amplitude of the impeller radial vibration direction at the peak frequency in the first frequency spectrum graph is less than the acceleration amplitude of the impeller radial vibration direction at the peak frequency in the second frequency spectrum graph and the acceleration amplitude difference between the two is less than the preset acceleration amplitude threshold value, it indicates that the flow-induced vibration characteristics of the turbine expander optimization model meet the requirements.

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