Numerical Simulation Method for Fluid-Structure-Electromagnetic Multi-Physical Field Coupling of Electric Pipeline Pump Sets

Abstract

The object of the present invention is to provide a numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of an electric pipeline pump group, including the following steps: performing pre-processing of fluid field numerical simulation, pre-processing of electromagnetic field numerical simulation, and iterative correction of a single physical field numerical model; establishing an iterative relationship of multi-physical fields and obtaining a numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of an electric pipeline pump; performing numerical simulation of fluid-structure-electromagnetic multi-physical field coupling of an electric pipeline pump, and obtaining the flow rate, pressure, load change of the electric pipeline pump and the vibration displacement and acceleration at the machine feet in real time during the solution process. The present invention studies the interaction mechanism between electromagnetic excitation and fluid excitation and structure, is used to study the operating state of the electric pipeline pump, and further determines the excitation characteristics in the pipeline pump equipment, so as to guide the production and optimization of low-noise design of the electric pipeline pump.

Description

Technical Field

[0001] The present invention relates to a numerical simulation method, specifically a numerical simulation method for multi-physical field coupling of an electric pipeline pump. Background Art

[0002] Electric pipeline pumps are usually used for pipeline pressurization to solve the problem of too low pipeline pressure. Compared with conventional horizontal centrifugal pumps, they have many advantages. The pump and motor of the pipeline pump are integrated, with simple installation, compact structure, and small floor space; the inlet and outlet pipe diameters are the same and on the same center line, which is convenient for pipeline layout; the pump body and the motor are coaxial, with a small axial dimension, enhancing the running stability of the pipeline pump. For a pipeline system, the flow field excitation in the system is closely related to the flow field excitation of the pump body. Therefore, the stability problem of the pipeline pump during operation has always been the focus of people's attention. Poor unit stability will cause large vibrations and noises, affecting performance, and even leading to major safety accidents in severe cases.

[0003] The pipeline pump includes components such as a suction pipe, an impeller, a guide vane, a motor, and an adjustment mechanism, and is an axial flow pump; among them, the impeller and the guide vane are important flow-through components of the pipeline pump, which determine the flow state inside the pump body and are directly related to the stable operation of the pump body. At the same time, since the motor drives the impeller to rotate, the electromagnetic excitation will also affect the operation state of the pump through the shafting, directly affecting its flow field. At the same time, the change of the flow field will also affect the motor electromagnetic field through the shafting, changing its electromagnetic excitation.

[0004] Due to the integrated design of the motor and the pump body of the electric pipeline pump, the electromagnetic excitation of the motor and the flow field excitation in the system are transmitted to the machine feet through the pump structure, affecting its vibration and noise.

[0005] Therefore, studying the fluid-structure-electromagnetic multi-physical field of the electric pipeline pump is of great significance for improving the operation state of the electric pipeline pump, can better study the electromagnetic field and fluid characteristics under non-rated conditions, and is of great significance for reducing vibration and noise of the electric pipeline pump. Summary of the Invention

[0006] The purpose of the present invention is to provide a numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of an electric pipeline pump group to study the operation state of the electric pipeline pump, further determine the excitation characteristics in the pipeline pump equipment, and guide the low-noise design, production, and optimization of the electric pipeline pump.

[0007] The purpose of the present invention is achieved as follows:

[0008] The numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of the electric pipeline pump group of the present invention is characterized in that:

[0009] (1) Conduct preprocessing for numerical simulation of the flow field and preprocessing for numerical simulation of the electromagnetic field, determine the three-dimensional model of the electric pipeline pump, structural grid division, materials, and unit properties, and boundary conditions;

[0010] (2) Iteratively correct the numerical model of a single physical field;

[0011] (3) Establish the iterative relationship of multiple physical fields and obtain the numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of the electric pipeline pump;

[0012] (4) Conduct numerical simulation of fluid-structure-electromagnetic multi-physical field coupling of the electric pipeline pump, and obtain the flow rate, pressure, load changes of the electric pipeline pump, and vibration displacement and acceleration at the machine feet in real time during the solution process.

[0013] The present invention may further include:

[0014] 1. The preprocessing of the flow field numerical simulation includes establishing a three-dimensional model of the electric pipeline pump, extracting the flow field domain, dividing the flow field grid, establishing a turbulence model, selecting a near-wall function, and grid independence verification; the preprocessing of the electromagnetic field numerical simulation includes setting electromagnetic field boundary conditions, dividing the electromagnetic field grid, setting the material properties of the rotor punching sheet, setting the transient solver, and grid independence verification.

[0015] 2. The iterative correction of the numerical model of a single physical field includes presetting the boundary conditions of the flow field numerical simulation, unsteady flow field numerical simulation based on the dynamic grid technology, iterative correction by comparing the calculated head of the pump body with the experimental data to obtain the flow field numerical calculation model, iterative correction of presetting the change of electromagnetic field simulation boundary conditions, change of material properties, and comparison with electromagnetic design sheets and experimental data, iterative correction of changing the material properties of the structural grid, changing the boundary conditions, and comparison with the modal experimental data.

[0016] 3. The specific process of obtaining the numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of the electric pipeline pump in step (3) is as follows:

[0017] For time t 0 Extract the fluid excitation on the housing component and the impeller to obtain the air-gap magnetic density of the electromagnetic field at time t 0 Calculate the radial electromagnetic force wave and tangential electromagnetic force wave through the Maxwell stress tensor method, and apply the fluid excitation on the impeller and the radial electromagnetic force wave and tangential electromagnetic force wave on the motor rotor at time t 0 to the rotor system, use rotor dynamics to calculate the vibration response at time t 0 +dt, and extract the longitudinal vibration displacement and rotation angle of the impeller and the motor; at the same time, the radial electromagnetic force wave on the motor stator and the fluid excitation on the housing at time t 0 and the fluid excitation on the housing at time t 0The nodal displacement response of the time structure is applied to the structural finite element model, and the response at time t is calculated through transient dynamics. 0 The nodal displacements at time t + dt are extracted. At this time, 0 the impeller displacement response and the longitudinal vibration response of the rotor dynamics at time t + dt are used as the boundary conditions for fluid simulation in the flow field calculation. At the same time, 0 the torque, rotation angle, and longitudinal vibration response in the motor rotor at time t + dt are used as boundary conditions for iterative calculation of the electromagnetic finite element model. Through the above steps, a coupled numerical simulation of fluid-structure-electromagnetic multi-physical fields is achieved, a multi-physical field iterative relationship is established, and a method for coupled numerical simulation of fluid-structure-electromagnetic multi-physical fields of an electric pipeline pump is obtained.

[0018] The advantages of the present invention are as follows: Using the dynamic mesh technology in CFD simulation, the numerical simulation study of the flow field of the electric pipeline pump is realized; using the electromagnetic field finite element simulation, the numerical simulation calculation of the electromagnetic field of the electric pipeline pump is realized; using the structural finite element simulation, the numerical calculation of the structural dynamic response of the electric pipeline group is realized. At the same time, the accuracy of the model is verified by the iteration of numerical calculation and existing experimental data, and the iterative calculation method of the numerical model is established by extracting the excitations of each part and modifying the boundary conditions, realizing the coupled numerical simulation method. At the same time, on the basis of the fluid-structure interaction calculation widely used in the field of pipeline pumps, the present invention considers the mutual influence of fluid excitation through the shafting and electromagnetic excitation.

[0019] In the past, when considering the coupled action of multi-physical fields in the calculation of electric pipeline pump groups, more fluid-structure interactions were considered. By establishing a coupled numerical calculation model of multi-physical fields, the present invention can more clearly study the internal operation law of the electric pipeline pump. At the same time, considering the fluid-structure-electromagnetic multi-physical field coupling, it can better observe the operation states of each component during the operation process, provide a research method for studying the operation state of the electric pipeline pump under non-steady working conditions, determine the excitation characteristics in the pipeline pump equipment by using the multi-physical field coupled numerical simulation method, and guide the production and optimization of low-noise design of the electric pipeline pump. Brief Description of the Drawings

[0020] Figure 1 is the flow chart of the present invention;

[0021] Figure 2 is the flow chart of the coupled numerical simulation method of multi-physical fields;

[0022] Figure 3 is the flow chart of the coupled numerical iteration of multi-physical fields. Detailed Embodiment

[0023] The present invention will be described in more detail with reference to the accompanying drawings as follows:

[0024] Combined with Figures 1-3 , the present invention includes the following steps:

[0025] Step 1. Preprocessing for numerical simulation of the flow field (3D model of the electric pipeline pump, extraction of the flow field domain, mesh generation of the flow field, selection of turbulence model, selection of near-wall functions, and verification of grid independence); preprocessing for numerical simulation of the electromagnetic field (setting of electromagnetic field boundary conditions, mesh generation of the electromagnetic field, setting of material properties of the stator and rotor laminations, setting of the transient solver, and verification of grid independence); 3D model of the electric pipeline pump, structured mesh generation, setting of material and element properties, and determination of boundary conditions.

[0026] The mesh generation part of the flow field in the preprocessing process has a great influence on the convergence and accuracy of subsequent numerical simulations. The process of refining the mesh in the near-wall region of the flow field mesh also has a great influence on the simulation of the flow in the near-wall region in numerical simulations. The present invention takes into account the different requirements of different turbulence models and near-wall functions for the height of the first layer of the mesh, and refines the mesh in the boundary layer region near the wall according to the parameters selected in the numerical simulation.

[0027] The mesh generation of the electromagnetic field in the preprocessing process has a great influence on the convergence and accuracy of subsequent numerical simulations. The process of refining the mesh in the air gap region in the electromagnetic field mesh generation has a great influence on the simulation of the air gap magnetic induction intensity in numerical calculations. At the same time, the setting of the electromagnetic materials in the electric pipeline pump will also affect the simulation results. The present invention considers the multi-physics field coupling numerical simulation method, which has high requirements for the accuracy and calculation duration of the calculation model, and grid independence verification is required.

[0028] The mesh generation of the structured mesh in the preprocessing process has a great influence on the convergence and accuracy of subsequent numerical simulations. It is necessary to simplify different structures and processing methods of simulations, and at the same time determine the boundary conditions, meshes at different positions, and material properties of the electric pipeline pump.

[0029] Step 2. Iterative correction of the single-physics field numerical model (presetting the boundary conditions for the numerical simulation of the flow field, unsteady flow field numerical simulation based on the dynamic mesh technology, iterative correction by comparing the calculated head of the pump body with the experimental data to obtain the numerical calculation model of the flow field; iterative correction by presetting the change of electromagnetic field simulation boundary conditions, change of material properties, and comparison with the electromagnetic design sheet and experimental data; iterative correction by changing the material properties of the structured mesh, changing the boundary conditions, and comparison with the modal experimental data)

[0030] For the iterative correction of the flow field numerical model, presetting the boundary conditions is very important. The inlet and outlet boundary conditions should conform to the engineering reality. The present invention selects the boundary conditions of pressure inlet and flow rate outlet. The inlet pressure is directly connected to the outside, so the pressure is one standard atmospheric pressure, while the outlet pressure is unknown. The flow rate outlet is determined according to the flow rate requirements under different working conditions.

[0031] In the transient flow field simulation calculation based on the dynamic mesh technology, the setting of the dynamic mesh, the compilation and call of the UDF program, and the implementation of parallel CFD calculation are the difficulties.

[0032] The division of the dynamic mesh area is mainly carried out in the preprocessing process, which will not be elaborated here. The selection of the dynamic mesh update method (spring smoothing method, dynamic layering method, and mesh reconstruction method) should be reasonable, and the update method should be suitable for the computational mesh. The type of the dynamic mesh area (rigid body, gradual change, and static) should conform to the actual situation to ensure that the movement of the flow field domain in the numerical simulation is consistent with the engineering practice. Therefore, during the movement of the fluid domain using the dynamic mesh technology, its original shape should be maintained, and there should be no cracks or deformations. The pump impeller rotates for a full week with a large displacement, and the dynamic mesh is realized by combining mesh deformation and local reconstruction. The basic method is as follows: when the rotation of the impeller blades is small, each edge of the mesh around the blades is regarded as a spring and undergoes a small deformation as the blades rotate; when the deformation is large and the deformation of the mesh around the blades exceeds a certain limit, re-meshing starts to make the mesh meet the requirements.

[0033] Since the commercial CFD solver ANSYS Fluent cannot realize the real-time monitoring and feedback of the displacement, velocity, acceleration, and force of the pump components, users need to write a custom program (UDF program) for secondary development to realize the above functions. The UDF program used in the present invention is written in C language and is used after being compiled in Fluent.

[0034] The parallel CFD calculation is realized based on the data aggregation of each computing node and the host node. Using parallel computing can greatly improve the computing speed and save time.

[0035] In the numerical iterative calculation of the electromagnetic field, it is very important to preset the boundary conditions, and the boundary conditions at different positions of the pipeline pump should conform to the engineering practice. Since usually the electric pipeline pump is in an insulating system, in the present invention, the outer boundary of the electric pipeline pump is set as the balloon boundary condition. Since the materials at different positions of the stator of the electric pipeline pump are different, the material properties need to be set separately. When the material properties of each part are defined, they need to be compared and corrected according to the electromagnetic design sheet and experimental data during the design, and at the same time, the accuracy of the electromagnetic field numerical calculation is verified. Since the commercial electromagnetic field solver Maxwell cannot realize the real-time monitoring and feedback of the air-gap magnetic density of the motor, users need to write a script for secondary development to realize the above functions. The script used in the present invention is written in the ironpython language and is used after being compiled in Maxwell, aiming to extract the air-gap magnetic density and modify the boundary conditions for simulation.

[0036] During the structural numerical iteration calculation process, boundary conditions, material properties, and cell types are very important for the calculation structure. The boundary conditions of the pipeline pump should conform to the engineering reality. Since the electric pipeline pump is usually fixed in the equipment by bolts, the node displacements at the bolt positions are constrained. After setting the material properties, element types, and boundary conditions of each part, the material properties and boundary conditions are corrected according to the comparison between the modal calculation results and the experimental data.

[0037] Step 3: Establish a multi-physics field iteration relationship and obtain a fluid-structure-electromagnetic multi-physics field coupling numerical simulation method for the electric pipeline pump. (Extract the flow field calculation results and electromagnetic calculation results respectively and apply them to the rotor to consider their influence on the rotor dynamics. Extract the calculation results to iteratively correct the boundary conditions of the flow field and electromagnetic field. At the same time, apply the corrected calculation results to the overall structural numerical calculation model after calculation for calculation)

[0038] For the fluid iteration calculation process, the present invention uses a user-written custom program (UDF program) for time t 0 to extract the fluid excitation received by the casing component and the impeller. For the electromagnetic field calculation results of the present invention, ironpython is used for extraction to obtain the air-gap magnetic flux density of the electromagnetic field at time t 0 and calculate the radial electromagnetic force wave and tangential electromagnetic force wave through the Maxwell stress tensor method. Apply the fluid excitation received by the impeller at time t 0 and the radial electromagnetic force wave and tangential electromagnetic force wave received by the motor rotor to the rotor system, and use rotor dynamics to calculate the vibration response at time t 0 +dt, and extract the longitudinal vibration displacement and rotation angle of the impeller and the motor; at the same time, apply the radial electromagnetic force wave received by the motor stator at time t 0 and the fluid excitation received by the casing, as well as the node displacement response of the structure at time t 0 to the structural finite element model, and extract the node displacement at time t 0 +dt through transient dynamics calculation of the response. At this time, use the impeller displacement response and rotor dynamics longitudinal vibration response at time t 0 +dt as the boundary conditions for fluid simulation, and at the same time use the torque, rotation angle, and longitudinal vibration response in the motor rotor at time t 0 +dt as the boundary conditions to perform iterative calculation on the electromagnetic finite element model. Through the above steps, realize the fluid-structure-electromagnetic multi-physics field coupling numerical simulation, establish a multi-physics field iteration relationship, and obtain a fluid-structure-electromagnetic multi-physics field coupling numerical simulation method for the electric pipeline pump.

[0039] Step 4: Perform fluid-structure-electromagnetic multi-physics field coupling numerical simulation on the electric pipeline pump. During the solution process, the flow rate, pressure, load changes, vibration displacement, acceleration, etc. at the machine feet of the electric pipeline pump can be obtained in real time.

Claims

1. Numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of an electric pipeline pump unit, Characterized in that: (1) Conduct pre-processing of fluid field numerical simulation and pre-processing of electromagnetic field numerical simulation to determine the three-dimensional model of the electric pipeline pump, structural mesh division, materials and element property settings, and boundary conditions; The pre-processing of the fluid field numerical simulation includes establishing the three-dimensional model of the electric pipeline pump, extracting the fluid field domain, dividing the fluid field mesh, establishing a turbulence model, selecting a near-wall function, and grid independence verification; the pre-processing of the electromagnetic field numerical simulation includes setting the electromagnetic field boundary conditions, dividing the electromagnetic field mesh, setting the material properties of the rotor punching sheet, setting the transient solver, and grid independence verification; (2) Iterative correction of the single physical field numerical model; (3) Establish the iterative relationship of multi-physical fields and obtain the numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of the electric pipeline pump; For time t 0 The fluid excitation of the casing parts and impeller is extracted to obtain t 0 The electromagnetic field air gap magnetic flux density at time t is calculated by using the Maxwell stress tensor method to calculate the radial electromagnetic force wave and the tangential electromagnetic force wave. 0 At this moment, the impeller is excited by the fluid and the radial electromagnetic force wave and tangential electromagnetic force wave of the motor rotor are applied to the rotor system. The rotor dynamics is used to calculate t 0 +dt time vibration response, and extract the longitudinal displacement and rotation angle of the impeller and motor; at the same time, t 0 At time t, the radial electromagnetic force wave on the motor stator and the fluid excitation on the casing 0 The node displacement response of the structure at time t is applied to the structural finite element model, and the transient dynamics calculation response is converted to 0 +dt time node displacement is extracted, at this time t 0 The impeller displacement response and rotor dynamics longitudinal vibration response at time +dt serve as boundary conditions for flow field calculation to perform fluid simulation. 0 +dt time, the torque, angle, and longitudinal vibration response of the motor rotor are used as boundary conditions to iteratively calculate the electromagnetic finite element model. Through the above steps, the fluid-structure-electromagnetic multi-physics field coupling numerical simulation is realized, the multi-physics field iterative relationship is established, and the fluid-structure-electromagnetic multi-physics field coupling numerical simulation method of the electric pipeline pump is obtained; (4) Conduct numerical simulation of fluid-structure-electromagnetic multi-physical field coupling of the electric pipeline pump, and obtain the flow rate, pressure, load change of the electric pipeline pump, and vibration displacement and acceleration at the machine feet in real time during the solution process.

2. The numerical simulation method for fluid-structure-electromagnetic multi-physical field coupling of the electric pipeline pump unit according to claim 1, Characterized in that: The iterative correction of the single physical field numerical model includes presetting the boundary conditions of the fluid field numerical simulation, unsteady fluid field numerical simulation based on the dynamic mesh technology, iterative correction by comparing the calculated head of the pump body with the experimental data to obtain the fluid field numerical calculation model, iterative correction by changing the preset electromagnetic field simulation boundary conditions, changing the material properties, and comparing with the electromagnetic design single and experimental data, iterative correction by changing the material properties of the structural mesh, changing the boundary conditions, and comparing with the modal experimental data.

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