Numerical simulation method for corrugated plate gas-liquid separator of nuclear power steam generator

Abstract

The present application provides a numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator, and belongs to the technical field of steam-water separation of nuclear power steam generators. The method solves the problem that the traditional separation model of the corrugated plate gas-liquid separator ignores the changes of the physical property parameters of the fluid and droplets under different pressures, resulting in differences between the simulation results and the actual operation results of the corrugated plate gas-liquid separator. The method comprises the following steps: creating a geometric model of the corrugated plate gas-liquid separator in modeling software, importing the established geometric model into a grid division software to perform grid division and obtain a grid file; establishing a droplet separation model of the corrugated plate; setting the droplet size distribution, droplet separation parameters, and the physical property parameters of the fluid and droplets in the grid file, solving the established droplet separation model of the corrugated plate; extracting the solving data and performing result analysis to obtain the separation performance of the corrugated plate gas-liquid separator under different working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to a numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator, and belongs to the technical field of steam-water separation of a nuclear power steam generator. BACKGROUND

[0002] The gas-liquid separator refers to a separation device for separating liquid droplets mixed in a gas flow. The gas-liquid separator is widely used in steam-water separation of a steam boiler, steam-water separation of a nuclear power steam generator, and water droplet separation in processes such as oil and natural gas exploration and storage and transportation. The gas-liquid separator can effectively reduce water droplets carried by the gas, avoid corrosion of the liquid droplets to the equipment, prolong the service life of the equipment, reduce water droplets carried by the steam, and improve the quality of the steam. The corrugated plate separator is widely used in actual industrial production due to its convenient production, high gas-liquid separation efficiency, and small occupied area.

[0003] The traditional corrugated plate gas-liquid separator separation model is calculated under normal pressure conditions, and the changes of the physical property parameters of the fluid and the liquid droplets under different pressures are ignored, so that there is a certain difference between the simulation results of the corrugated plate gas-liquid separator and the actual operation results. At the same time, the development cost of the high-pressure condition gas-liquid separator experimental device is relatively high. Due to the limitation of the experimental device, the measured data can only measure the non-continuous data at the boundary of the experiment, and the guiding significance for revising the overall structure of the gas-liquid separator is relatively small. Only through a large number of repetitive experiments can relatively comprehensive data be obtained. The experimental process not only consumes a large amount of manpower and material resources, but also has a relatively long development cycle. Numerical calculation is a new technology developed in recent years. The numerical calculation method is used to solve the physical process in the fluid domain to obtain the physical solution at different positions in the whole flow domain. The numerical calculation method has the characteristics of good adjustability, short research and development cycle, and vivid display of the physical process.

[0004] In view of the defects of the prior art, the present application designs a numerical simulation method of a corrugated plate gas-liquid separator for separating liquid droplets under different pressures, which can more accurately predict the difference in the separation capacity of the corrugated plate gas-liquid separator for different particle sizes of liquid droplets under different pressures. SUMMARY

[0005] The present application is to solve the problem that the traditional corrugated plate gas-liquid separator separation model ignores the changes of the physical property parameters of the fluid and the liquid droplets under different pressures, resulting in a difference between the simulation results of the corrugated plate gas-liquid separator and the actual operation results, and further proposes a numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator.

[0006] The technical scheme adopted by the present application to solve the above problems is as follows:

[0007] Step 1: create a corrugated plate gas-liquid separator geometry model in modeling software, and import the established geometry model into a meshing software for meshing to obtain a mesh file;

[0008] Step 2: based on the relationship between the interaction flow between droplets and fluid in the corrugated plate internal fluid domain, gas flow and droplet separation captured by the fluid domain wall, a corrugated plate droplet separation model is established;

[0009] Step 3: set the droplet particle size distribution, droplet separation parameters and physical property parameters of the fluid and droplets in the mesh file, solve the established corrugated plate droplet separation model, and obtain the separation efficiency of the corrugated plate under the set working condition.

[0010] Step 4: extract the solution data and perform result analysis to complete the numerical simulation of the corrugated plate gas-liquid separator.

[0011] Preferably, the corrugated plate gas-liquid separator geometry model in step 1 includes the corrugated plate internal fluid domain and the fluid domain wall.

[0012] Preferably, after meshing the corrugated plate gas-liquid separator geometry model in step 1, the fluid domain wall mesh is encrypted.

[0013] Preferably, the corrugated plate droplet separation model in step 2 includes a turbulent flow model, a gas-liquid two-phase flow model and a fluid domain wall droplet capture model in the fluid domain.

[0014] Preferably, the turbulent flow model selects k-ε model and uses enhanced wall function, and based on k-ε model, obtains mass and momentum conservation equations of steady gas flow and transport equations of turbulent kinetic energy k and dissipation rate ε.

[0015] Preferably, the gas-liquid two-phase flow model selects DPM model, takes the fluid as the continuous phase and the droplet as the discrete phase, obtains the motion equation of the discrete droplet in the Lagrangian reference system, and opens the discrete random trajectory model to determine the instantaneous gas velocity.

[0016] Preferably, the fluid domain wall droplet capture model selects Euler liquid film model, and based on Euler liquid film model, obtains the mass equation and momentum equation of the liquid film.

[0017] Preferably, step 3 specifically includes:

[0018] Step 3.1: read the mesh file using the meshing software, set the flow channel inlet of the corrugated plate gas-liquid separator as the gas and droplet velocity inlet boundary, and the gas and droplet enter the channel at the same speed, wherein the droplet diameter distribution obeys Rosin-Rammler distribution, the wall boundary condition is set based on k-ε model, the flow channel outlet is set as the gas pressure outlet boundary, the continuous phase and the discrete phase are coupled, the Euler liquid film model and the DPM model are coupled, and the initial conditions of the calculation domain are set.

[0019] Step 3.2: set the fluid phase as saturated steam, and the particle phase as saturated liquid; set the physical property parameters of the fluid phase and the particle phase according to the pressure;

[0020] Step 3.3: solve the corrugated plate separation droplet model according to the set different pressure conditions, different physical property parameters of the gas phase and the liquid phase, to obtain the separation efficiency of the liquid droplets with different particle sizes at different wave nodes of the corrugated plate under the set working conditions.

[0021] The beneficial effects of the present application are:

[0022] (1) The present application divides the model into a fluid domain and a fluid domain wall surface on the basis of the grid-based corrugated plate separation droplet geometric model, and encrypts the wall surface grid; uses the DPM model to regard the liquid droplets as a discrete phase and high-pressure air as a continuous phase, and simultaneously opens the discrete random trajectory model; and sets the Euler liquid film model (EWF) on the wall surface, which can truly simulate the motion trajectory of the liquid droplets in the fluid domain and the process of the liquid droplets impacting the wall surface.

[0023] (2) The present application overcomes the defects of the above-mentioned prior art under normal pressure conditions, can truly simulate the process of the corrugated plate separation droplets, obtain the separation capacity of the corrugated plate at different wave nodes for liquid droplets with different particle sizes under different pressures, and more accurately predict the separation performance of the corrugated plate, which has important significance for understanding the biomass particle pyrolysis process in detail and guiding engineering practice.

[0024] (3) The present application divides the grid of the gas-liquid separator internal space through a finite element modeling software (such as fluent mesh, Gambit, ICEM, etc.), which reduces the calculation cost while meeting the required grid quality for calculation. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A flowchart of a numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator is provided for the present application;

[0026] Figure 2 A grid division schematic diagram is provided for the present application;

[0027] Figure 3 A spatial arrangement schematic diagram of a corrugated plate gas-liquid separator is provided for the present application;

[0028] Figure 4 A separation efficiency schematic diagram of different particle sizes at the first wave node under different pressures is provided for the present application;

[0029] Figure 5 A separation efficiency schematic diagram of different particle sizes at the second wave node under different pressures is provided for the present application;

[0030] Figure 6 A schematic diagram illustrating the separation efficiency of different particle sizes at the third-stage node under different pressures, provided by the present invention.

[0031] Figure 7 This is a schematic diagram comparing the calculation results of this invention with experimental data;

[0032] Figure 8 This is a schematic diagram comparing the separation efficiency and pressure drop of the present invention. Figure 8 In the diagram, (a) shows a comparison of separation efficiency, and (b) shows a comparison of pressure drop.

[0033] Figure 9 The trace diagrams of droplet particles at different velocities provided by this invention. Detailed Implementation

[0034] Combination Figures 1-6 This implementation method is described as follows: Figure 1 As shown, the steps of the numerical simulation method for a corrugated plate gas-liquid separator for a nuclear power steam generator described in this embodiment include:

[0035] S1: Create a geometric model of the corrugated plate gas-liquid separator in the modeling software, and import the established geometric model into the mesh generation software to generate a mesh file;

[0036] In this embodiment, the modeling software is SolidWorks, the mesh generation software is FluentMesh, and the geometric model of the corrugated plate gas-liquid separator includes the internal fluid domain of the corrugated plate and, for example, the fluid domain inside the corrugated plate. Figure 2 The fluid domain wall shown.

[0037] S2: Based on the influence of airflow in the fluid domain, the interactive flow between droplets and fluid, and the capture and separation of droplets by the fluid domain wall, a corrugated plate model for separating droplets is established.

[0038] In this embodiment, the established corrugated plate droplet separation model includes a turbulence model, a gas-liquid two-phase model, and a wall collision model.

[0039] S201: The turbulence model is the k-ε model. Based on the principle of mass and momentum conservation, the mass and momentum conservation equations for steady-state gas flow are:

[0040]

[0041] In formulas (1) and (2), ρ f Let μ be the gas density, f be the gas velocity, and f be the interaction force between the gas and the droplet. eff The effective viscosity of the gas is given by the gas dynamic viscosity u. f and turbulent viscosity u tThe composition, the gas turbulent viscosity is calculated according to the available k-ε model, and the expressions of the turbulent kinetic energy k and the dissipation rate ε transport equation are as follows:

[0042]

[0043] In the formula (3) and (4), G k is the energy generated by the turbulence, the coefficient σ k is 1.0, the coefficient σ ε is 1.2, the coefficient C1 is 1.44, and the coefficient C2 is 1.9.

[0044] S202: The DPM model is selected for the gas-liquid two-phase model, the fluid is regarded as a continuous phase, and the discrete droplet is regarded as a discrete phase. The motion equation of the discrete droplet in the Lagrange reference system is described as follows:

[0045]

[0046] In the formula (5), u is the droplet velocity, ρ p is the droplet density, is the force acting on the droplet, F D is the drag coefficient of the unit mass droplet, and the expression of F D is as follows:

[0047]

[0048] In the formula (6), C d is the drag coefficient, Re r is the relative Reynolds number, d p is the droplet diameter, and the expression of Re r is as follows:

[0049]

[0050] The present embodiment adopts a random method (discrete random walk model) to determine the instantaneous gas velocity. In the discrete random walk model (DRW), the fluid fluctuation velocity component is a discrete segmented function of time. The fluid fluctuation velocity which is dominant during the lifetime of the turbulent vortex is assumed to obey a Gaussian probability distribution:

[0051]

[0052] In the formula (8), ξ is a random number obeying a normal distribution, τ e is the droplet vortex characteristic lifetime, and T cross is the droplet vortex crossing time. For a small droplet moving together with the fluid (zero drift velocity), the vortex characteristic lifetime is proportional to the Lagrange integral time of the fluid, that is:

[0053]

[0054] In formula (9), C L = 0.15, and the expression of the droplet vortex crossing time T cross0 is as follows:

[0055]

[0056] In formula (10), L e is the vortex length size.

[0057] S203: The wall surface model selects the EWF model, i.e., the Euler liquid film model, and the expression of the mass equation of the liquid film is as follows:

[0058]

[0059] In formula (11), h is the water film thickness, ▽ s is the surface gradient operator, V1 is the water film velocity vector, ρ1 is the water film density, is the liquid mass flow per unit area;

[0060] The expression of the momentum equation is as follows:

[0061]

[0062] In formula (12), g τ is the gravity component parallel to the wall; τ fs is the shear stress of the gas-liquid interface; ν1 is the kinematic viscosity of the liquid film; q is the pressure change on the liquid film surface; P L is the pressure of the gas on the wall, the gravity component perpendicular to the wall, and the resultant force of the surface tension, and its expression is as follows:

[0063] P L = P gas + P h + P σ (13).

[0064]

[0065] P σ = -σ▽ S ·(▽ S h) (15).

[0066] The expression of the energy equation is as follows:

[0067]

[0068] In formula (16), T f is the average temperature of the liquid film perpendicular to the wall; V f is the average velocity of the liquid film; c pCp is the constant pressure specific heat capacity of water; T s T is the liquid film temperature at the gas-liquid interface; T w T is the liquid film temperature at the wall surface; k f k is the thermal conductivity of the liquid film; E is the energy carried by the liquid droplet when it impacts the wall surface; m is the evaporation rate of the liquid film; L is the latent heat of evaporation of the liquid film.

[0069] Since the thickness of the liquid film generated under the Euler liquid film model is much smaller than the radius of curvature of the wall surface, the physical properties of the liquid film do not change with the thickness of the liquid film, so this embodiment only uses the mass and momentum conservation equations of the liquid film.

[0070] S3: Read the calculation grid file using the fluent mesh, then establish the initial conditions and boundary conditions, give the solution control parameters, and solve the established corrugated plate separation droplet model;

[0071] S301: As shown in Figure 3 , the gravity direction of the corrugated plate is downward, the flow channel inlet is a gas and liquid droplet velocity inlet boundary, the humidity is 5%, and the gas and liquid droplets flow into the channel at the same speed of 4 m / s; the droplet diameter distribution obeys the Rosin-Rammler distribution, the minimum and maximum diameters are 0.001 mm and 0.05 mm, the median is 0.01 mm, and the particle size dispersion coefficient is 2.5; the flow channel outlet is a gas pressure outlet boundary; the outlet is set to escape, and the wall surface is set to trap; different pressure conditions are 1.6 MPa, 2.5 MPa, 3.8 MPa, 5.3 MPa, 5.5 MPa, and 7 MPa; the continuous phase and the dispersed phase are coupled; the Euler liquid film model and the DPM model are coupled;

[0072] S302: In this embodiment, the fluid phase is set to saturated steam, and the particle phase is set to saturated liquid; the physical property parameters of the fluid phase and the particle phase are set according to the pressure.

[0073] S4: Extract the solution data and perform result analysis to obtain the separation performance of the corrugated plate gas-liquid separator under different conditions;

[0074] This embodiment sets different pressures, different physical property parameters of the gas phase and the liquid phase, and comprehensively analyzes the separation performance of the corrugated plate gas-liquid separator under different conditions, and the separation performance of the corrugated plate gas-liquid separator under different pressures is obtained as shown in Figures 4-6 .

[0075] In addition, in order to verify the accuracy of the simulation results in this embodiment, the technical effects obtained by the above steps are compared with the actual data, and the comparison results are as shown in Figures 7-8 . Figure 7It can be known that the separation efficiency and actual data accuracy of the particles with different particle sizes obtained by the application are extremely high, and the data accuracy is Figure 8 (a) and Figure 8 (b) It can be known that the maximum and minimum separation efficiency of the application respectively differ by 1.04% and 0.19%, the maximum and minimum pressure drop respectively differ by -2.97% and 19.67%, and the above, the application adopts the optimization wall function algorithm, and the process of capturing, impacting and breaking into small droplets of the liquid droplets on the corrugation and the secondary droplet formation of the liquid film on the corrugated plate under the action of high-pressure gas flow is refined, as shown in Figure 9 The specific process of the liquid droplets flowing between the corrugated plates is vividly presented, compared with the traditional numerical method, the application improves the calculation accuracy of the gas-liquid separation efficiency and the pressure drop in the corrugated plate, and more accurately predicts the separation performance and the pressure drop of the corrugated plate, thereby providing a powerful tool for designing a high-performance corrugated plate separator.

[0076] The above is only a preferred embodiment of the application, and does not limit the application in any form, although the application has been disclosed as above, however, it is not intended to limit the application, any person skilled in the art, without departing from the technical solution of the application, can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments, as long as it does not depart from the technical solution of the application, according to the technical essence of the application, within the spirit and principles of the application, any simple modification, equivalent replacement and improvement of the above embodiments, all still belong to the protection scope of the technical solution of the application.

Claims

1. A numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator, characterized by, The steps of the numerical simulation method of the corrugated plate gas-liquid separator for nuclear power steam generators include the following steps: Step 1: A geometric model of the corrugated plate gas-liquid separator is created in modeling software, and the established geometric model is imported into a mesh division software for mesh division to obtain a mesh file; Step 2: Based on the relationship between the interactive flow between droplets and fluid in the internal fluid domain of the corrugated plate, the gas flow, and the separation of the droplets captured by the fluid domain wall, a droplet separation model of the corrugated plate is established; Step 3: The droplet particle size distribution, droplet separation parameters, and the physical property parameters of the fluid and the droplets are set in the mesh file, the established droplet separation model of the corrugated plate is solved, and the separation efficiency of the corrugated plate under the set working condition is obtained; Step 4: The solving data is extracted and the result is analyzed, and the numerical simulation of the corrugated plate gas-liquid separator is completed.

2. The numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator according to claim 1, characterized in that, The geometric model of the corrugated plate gas-liquid separator in step 1 includes the internal fluid domain of the corrugated plate and the fluid domain wall.

3. The numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator according to claim 1, characterized in that, After the mesh division of the geometric model of the corrugated plate gas-liquid separator in step 1, the fluid domain wall mesh is encrypted.

4. The numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator according to claim 1, characterized in that, The droplet separation model of the corrugated plate in step 2 includes a turbulent flow model, a gas-liquid two-phase flow model, and a droplet capture model of the fluid domain wall.

5. The numerical simulation method of a corrugated plate gas-liquid separator for a nuclear power steam generator according to claim 4, characterized in that, The turbulent flow model selects the k-ε model and uses the enhanced wall function, and the mass and momentum conservation equations of the steady gas flow and the transport equations of the turbulent kinetic energy k and the dissipation rate ε are obtained based on the k-ε model.

6. The numerical simulation method of a corrugated plate gas-liquid separator for nuclear power steam generators according to claim 4, characterized in that, The gas-liquid two-phase flow model selects the DPM model, takes the fluid as the continuous phase and the droplet as the discrete phase, obtains the motion equation of the discrete droplet in the Lagrangian reference system, and opens the discrete random trajectory model to determine the instantaneous gas velocity.

7. The numerical simulation method of a corrugated plate gas-liquid separator for nuclear power steam generators according to claim 4, characterized in that, The droplet capture model of the fluid domain wall selects the Euler liquid film model, and the mass equation and the momentum equation of the liquid film are obtained based on the Euler liquid film model.

8. The numerical simulation method of a corrugated plate gas-liquid separator for nuclear power steam generators according to claim 1, characterized in that, Step 3 specifically includes: Step 3.1: The mesh file is read by using the mesh division software, the inlet of the flow channel of the corrugated plate gas-liquid separator is set as the gas and droplet velocity inlet boundary, the gas and droplet enter the channel at the same speed, the droplet diameter distribution obeys the Rosin-Rammler distribution, the wall boundary condition is set based on the k-ε model, the outlet of the flow channel is set as the gas pressure outlet boundary, the continuous phase and the discrete phase are coupled, the Euler liquid film model and the DPM model are coupled, and the initial conditions of the calculation domain are set; Step 3.2: The fluid phase is set as saturated steam, and the particle phase is set as saturated liquid; the physical property parameters of the fluid phase and the particle phase are set according to the pressure; Step 3.3: The droplet separation model of the corrugated plate is solved according to the set different pressure conditions, different gas phase and liquid phase physical property parameters, and the separation efficiency of the droplets of different particle sizes at different wave nodes of the corrugated plate under the set working condition is obtained.

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