CN102880757A - Micro-irrigation pressure adjuster design method based on fluid-solid coupling numerical calculation - Google Patents

Abstract

The invention discloses a micro-irrigation pressure regulator design method based on fluid-solid coupling numerical calculation. Firstly, according to the design requirements of the micro-irrigation pressure regulator, CAD software is used to establish a parametric geometric model of the fluid area in the micro-irrigation pressure regulator and an adjustment component geometry model. Then import the CAD models of the fluid and regulating components into the corresponding fluid and structure calculation modules in the CAE software ADINA, set the boundary conditions and solve the control parameters, and then carry out the numerical calculation of the fluid-solid coupling. In the process of numerical calculation, grid reconstruction is performed in time to ensure the quality of the calculation grid. According to the calculation results, the parameters of the geometric model were adjusted until the calculation results met the design accuracy requirements, and then the rapid prototyping test pieces were produced for pressure regulation performance experiments. Compare the experimental results with the design requirements, or modify the model, or complete the design. The method overcomes the disadvantages of long development period and high cost in the traditional design, and improves the design accuracy and efficiency of the micro-irrigation pressure regulator.

Description

A Design Method of Micro-irrigation Pressure Regulator Based on Fluid-Structure Interaction Numerical Calculation

technical field

The invention relates to a design method of a micro-irrigation pressure regulator, in particular to a rapid design method of a micro-irrigation pressure regulator realized by using fluid-solid coupling numerical calculation technology.

Background technique

The pressure regulator is one of the main pressure regulating devices in the current micro-irrigation system. When the inlet pressure changes, its flow channel will automatically become larger or smaller to keep the outlet pressure stable. The pressure regulator has the characteristics of simple structure, wide adjustment range, and stable performance. It is usually installed at the inlet of branch pipes or capillary pipes in micro-irrigation projects, so that the pressure and head of each branch pipe or capillary inlet are equal, which reduces tedious calculations during design and simplifies the pipe network. The design improves the irrigation uniformity of the irrigation system, and also ensures that each drip irrigation belt works within the design working pressure range. It avoids the bursting of the drip irrigation belt caused by excessive pressure caused by improper design or operational errors, prolongs the service life of the drip irrigation project, and ensures the safety of the system. Most of the micro-irrigation pressure regulators on the market now adjust the outlet pressure by adjusting the axial movement of the adjustment component in the cavity under the water pressure and changing the size of the flow passage section. Among them, there is a strong dynamic coupling relationship between the axial movement of the regulating component and the fluid motion, and it is difficult to obtain the dynamic flow characteristics of the fluid in the micro-irrigation pressure regulator by using the traditional CFD analysis method.

The traditional micro-irrigation pressure regulator design mainly adopts the method of combining CFD calculation and experiment. It is not easy to accurately understand the relationship between the axial deformation of the adjustment component and the inlet and outlet pressure. The error of the model prediction result is relatively large, and the model parameters mainly depend on In the physical part experiment, the product is finalized through repeated experiments, the blindness of design and development is large, the development cycle is long, and the development cost is high.

Contents of the invention

In view of the defects or deficiencies in the above-mentioned prior art, the object of the present invention is to propose a design method for a micro-irrigation pressure regulator based on fluid-solid coupling numerical calculation.

In order to realize above-mentioned task, the technical scheme that the present invention adopts is:

A micro-irrigation pressure regulator design method based on fluid-solid coupling numerical calculation, characterized in that first, according to the design requirements of the micro-irrigation pressure regulator, CAD software is used to establish a parametric geometric model of the fluid area in the micro-irrigation pressure regulator and adjustment components geometry model. Then import the CAD models of the fluid and regulating components into the corresponding fluid and structure calculation modules in the CAE software ADINA, set the boundary conditions and solve the control parameters, and then carry out the numerical calculation of the fluid-solid coupling; during the numerical calculation process, the grid reconstruction is performed in due course In order to ensure the quality of the calculation grid, adjust the geometric model parameters according to the calculation results until the calculation results meet the design accuracy requirements, then make a rapid prototyping test piece and conduct a pressure regulation performance experiment. If the deviation between the experimental results and the design requirements is within the design accuracy requirements Within the range, the design is completed, and if not, the model is modified.

This method overcomes the shortcomings of traditional micro-irrigation pressure regulator design, such as neglecting the coupling effect of fluid and regulating components in CFD calculation, model parameters mainly rely on estimation, and then determined through repeated experiments, long development cycle, and high development cost, and significantly improves micro-irrigation. Pressure regulator design accuracy and efficiency.

Description of drawings

Fig. 1 is a technical roadmap of the present invention;

Fig. 2 is a schematic diagram of the structure and calculation boundary conditions of the example model of the micro-irrigation pressure regulator of the present invention; the marks in the figure respectively represent: 1, pressure inlet, 2, fluid-solid coupling surface, 3, contact position. 4. Pressure outlet.

Fig. 3 is a geometrical model diagram of the fluid domain of the micro-irrigation pressure regulator of the present invention;

Fig. 4 is a diagram of the fluid domain grid model of the micro-irrigation pressure regulator of the present invention;

Fig. 5 is a geometric model diagram of the regulating assembly and the contact wall surface of the present invention;

Fig. 6 is a grid model diagram of the adjustment assembly and the contact wall surface of the present invention;

Fig. 7 is a cross-sectional view of the fluid deformation grid caused by the axial movement and deformation of the adjustment component in the adjustment chamber area of the present invention;

Fig. 8 is a cross-sectional view of the fluid grid redivided in the adjustment cavity area of the present invention.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Detailed ways

Referring to Fig. 1, this embodiment provides a design method of micro-irrigation pressure regulator based on numerical calculation of fluid-solid coupling, and its main design steps are as follows:

1) First, according to the design requirements of the micro-irrigation pressure regulator, CAD software is used to establish the parametric geometric model of the fluid area in the micro-irrigation pressure regulator and the geometric model of the regulating components in the solid area;

2) Then import the CAD model into the CAE software ADINA, set the same boundary conditions as the actual working conditions and solve the control parameters, and then perform the numerical calculation of the fluid-solid coupling;

3) Adjust the parameters of the geometric model according to the calculation results until the deviation between the calculation results and the design requirements is within 10% of the design accuracy requirements, and then make a rapid prototyping test piece for pressure regulation performance experiments;

4) Comparing the experimental results of the pressure regulation performance with the design requirements, if the deviation between the experimental results and the design requirements is within 10% of the design accuracy requirements, the design is completed, and if not, the geometric model of the regulating component is modified.

The specific design process of this method is given below:

(1) Geometric model establishment

Preliminarily determine the structural parameters of the micro-irrigation pressure regulator according to the design requirements of the micro-irrigation pressure regulator, that is, use CAD software to establish the geometric model of the fluid area of the micro-irrigation pressure regulator and the geometric model of the regulating components, and ensure that the coordinates of the fluid area and the solid area are consistent; Since the axial movement deformation of the adjustment component has a great influence on the working performance of the micro-irrigation pressure regulator, and the preset pressure of the spring is an important factor in determining the starting pressure, a contact is established at the contact part between the adjustment component and the shell wall.

The schematic diagram of the structure and calculation boundary conditions of the micro-irrigation pressure regulator example model is shown in Figure 2, and the fluid model of the micro-irrigation pressure regulator is shown in Figure 3.

(2) Model import and discretization

Import the geometric models of the fluid domain and regulating components into the corresponding fluid and structure calculation modules in the CAE calculation software ADINA, and set the material parameters of the fluid and regulating components respectively. The main parameters of the fluid are incompressible viscous fluids with a density of 1000kg/m ³ The viscosity is 0.001N·s/m ² , and the turbulence model is K-ε high Reynolds number turbulence model. Relevant material models are adopted for the regulating components, and the model parameters and Poisson's ratio μ are determined according to the materials used. The material density of the regulating components used in this design is 2000kg/m ³ , and the Poisson's ratio μ is 0.3. The contact wall model adopts the surface geometry established in ADINA software and is set as a rigid contact surface.

Geometric discretization was carried out in ADINA software, and meshing was performed. The fluid model is discretized using 4-node tetrahedral grid units, and the grid is shown in Figure 4. The regulating component model adopts 8-node hexahedral mesh unit to discretize, and the contact wall model adopts 4-node surface mesh. The regulating component and the contacting wall mesh are shown in Fig. 5;

(3) Boundary condition setting

The fluid analysis adopts the pressure inlet (position shown in Figure 2) and outlet conditions, the outlet pressure value is atmospheric pressure, the reference value is 0kPa (position shown in Figure 2), and the fluid-regulating component interface is the fluid-solid coupling boundary ( The position indicated by 2 in Figure 2). Considering the unknown of the contact analysis in the structural field, the transient solution method combining the iterative method and the incremental method is adopted, and the pressure at the inlet is loaded incrementally. At the same time, the pressure loading is controlled to avoid grid overlap caused by excessive deformation of the adjustment components, and to ensure calculation convergence. The contact surface between the adjustment component and the shell wall is the contact boundary (the position indicated by mark 3 in Figure 2), the friction coefficient is measured by experiments, and the interface between the adjustment component and the fluid is the fluid-solid coupling boundary (the position indicated by mark 2 in Figure 2) .

(4) Numerical calculation of fluid-solid coupling

The iterative coupling analysis method is adopted for the fluid-solid coupling, the complete Newton iterative method is adopted for the solution of the governing equation, and the convergence criterion of displacement and pressure—the relative residual error is less than 1×10 ^-5 . The fluid governing equations are solved using the finite volume method, the second-order composite time integration scheme, and the simple algorithm. The variable convergence criterion—the relative residual error is less than 1×10 ^-5 . Solid analysis adopts implicit dynamic analysis method, discrete finite element method, second-order precision Bathe composite time integration format, complete Newton iterative method calculation, displacement convergence criterion - relative residual error is less than 1×10 ^-5 , adjust the distance between component and wall The contact analysis uses the constraint function algorithm.

(5) Adaptive grid reconfiguration and restart analysis

The adjustment component undergoes axial movement and deformation under the action of fluid pressure (as shown in Figure 6), resulting in a change in fluid geometry and distortion of the fluid grid (as shown in Figure 7). Distortion of the fluid grid will affect the convergence of the calculation. When the grid distortion causes the coupling calculation to fail to converge within 50 steps, the calculation is stopped and the fluid domain grid is reconstructed. The fluid grid after reconstruction is shown in Figure 8. Apply the results before the suspension of the calculation as the initial conditions to the reconstructed new mesh model, and return to the fifth step to continue the numerical calculation of the fluid-structure interaction until the loaded inlet pressure value reaches the required pressure.

(6) Post-processing

After the calculation is completed, count the outlet pressure corresponding to different inlet pressures, draw the inlet and outlet pressure relationship curves, and compare them with the design requirements: if the deviation between the calculation results and the design requirements is within 10% of the design accuracy requirements, then complete the calculation and proceed to the seventh step. Otherwise, return to the first step, modify the model parameters and recalculate until the design requirements are met, and record the calculated model parameters and calculation results to provide a basis for modifying the model parameters.

(7) Production of rapid prototyping parts

According to the structural parameters of the micro-irrigation pressure regulator determined by the fluid-solid coupling calculation, its rapid prototyping test piece was made, and the test piece assembly was completed.

(8) Pressure regulation performance experiment

Connect the fabricated test pieces to the micro-irrigation pressure regulator comprehensive performance test bench for experiments. Compare the experimental results with the design requirements, modify the model parameters of the micro-irrigation pressure regulator according to the results, and return to the first step to recalculate until the deviation between the experimental results and the design requirements is within the allowable range of the design accuracy requirements, and the micro-irrigation pressure adjustment is completed The device is quickly finalized.

Claims (2)

1. a slight irrigation pressure governor method for designing of calculating based on the solid Coupled Numerical of stream is characterized in that, follows these steps to design:

1) at first according to the designing requirement of slight irrigation pressure governor, adopt CAD software pro/e to set up the adjusting part geometric model of fluid mass Parametric geometric model and solid area in the slight irrigation pressure governor;

2) then cad model is imported among the CAE software ADINA, after setting the boundary condition identical with actual condition and finding the solution the control parameter, flow solid Coupled Numerical and calculate;

3) adjust the geometric model parameter according to the solid Coupled Numerical result of calculation of stream, until result of calculation and designing requirement deviation design accuracy require 10% within, produce the rapid shaping testpieces, carry out pressure regulating performance and test;

4) contrast pressure regulating performance experimental result and designing requirement, if experimental result and designing requirement deviation design accuracy require 10% within, if complete design then is the satisfied model of then not revising.

2. the method for claim 1 is characterized in that, the specific design step is as follows:

1) geometric model is set up

Tentatively determine slight irrigation pressure governor structural parameters according to the designing requirement of slight irrigation pressure governor, namely use CAD software to set up respectively the adjusting part geometric model of slight irrigation pressure governor fluid domain geometric model and solid area, and guarantee that the fluid mass is consistent with the coordinate of solid area;

2) model imports and is discrete

Fluid domain and adjusting part geometric model are imported respectively corresponding fluid and structural calculation module among the CAE software for calculation ADINA, and the material parameter of fluid, adjusting part is set respectively, fluid is incompressible viscous fluid, density 1000kg/m ³, kinetic viscosity 0.001Ns/m ², turbulence model is selected K-ω high reynolds number turbulence model; Adjusting part adopts isotropic linear elastic material material model, determines model parameter according to material therefor, and the adjusting part density of material is 2000kg/m ³, Poisson ratio μ is 0.3, determines that the contact wall model adopts contact boundary condition, carries out geometry and disperses grid division in ADINA software; Fluid model adopts 4 node tetrahedral grid mesh discretizations; Solid model adopts 8 node hexahedral mesh mesh discretizations, and the contact wall model adopts 4 node surface grids discrete;

3) boundary condition setting

Fluid analysis adopts pressure entrance and exit condition, and the top hole pressure value is atmospheric pressure, and the relative pressure value is 0.Fluid-adjusting part interface is for flowing the border that admittedly is coupled; Consider the not intellectual of contact analysis in the structure field, select method for solving, porch pressure form, the transient state method for solving that adopts process of iteration to combine with method of addition; Determine boundary condition, the friction factor of adjusting part and shell wall side surface of contact and flow the border that admittedly is coupled;

4) the solid Coupled Numerical of stream calculates

The solid coupling of stream adopts the iteration coupling analytical method, and governing equation is found the solution and adopted complete Newton iteration method, and displacement and pressure convergence criterion---relative residual error is less than 1 * 10 ^-5, the fluid governing equation is found the solution the employing Finite Volume Method, and form is selected the second order spatial spreading, and time integral adopts second order composite Integration Scheme, finds the solution and adopts the simple algorithm, the variable convergence criterion---and residual error is less than 1 * 10 relatively ^-5, solid analysis adopts the implicit expression method of dynamic analysis, and Finite Element Method is discrete, and Newton iteration method is calculated fully, the displacement convergence criterion---and residual error is less than 1 * 10 relatively ^-5, contact analysis adopts constraint function algorithm;

5) adaptive mesh reconstruct with restart analysis

Axially-movable distortion occurs in adjusting part under fluid pressure action, thereby causes the change of fluid geometric configuration and cause the fluid mesh distortion; Fluid grid distorted can affect computational convergence, therefore needs to determine suitable calculating step number, and this paper was set to for 50 steps, if do not restrain, termination of computations is carried out the fluid domain grid reconstruction;

Result before the termination of computations is applied on the new grid model after the reconstruct as starting condition, returned for the 5th step and continue the solid Coupled Numerical of stream and calculate, until the inlet pressure value that loads reaches required pressure;

6) aftertreatment

Top hole pressure corresponding to the different inlet pressures of statistics after calculating is finished drawn the inlet and outlet pressure relation curve, and compares with designing requirement:

If result of calculation and designing requirement deviation design accuracy require 10% within, then finish calculating, carry out the work of the 7th step; Otherwise return the first step, revise model parameter and recomputate until meet design requirement, and record finished model parameter and the result of calculation of calculating, provide foundation for revising model parameter;

7) Quick formed part is made

Determined slight irrigation pressure governor structural parameters are calculated in solid coupling according to stream, make its rapid shaping experimental piece, and finish the experimental piece assembling;

8) pressure regulating performance experiment

With the experimental piece access slight irrigation pressure governor combination property bench of making, test, and experimental result and designing requirement are compared, determine whether to finish the design of slight irrigation pressure governor fast shaping.

Images