CFD simulation-based strip steel surface purging method

Abstract

The invention discloses a strip steel surface purging method based on CFD simulation. The method is specifically implemented according to the following steps that S1, key parameters during strip steel purging are collected, and a purging simplified model is established; s2, dividing the purge simplified model into grids, and performing local encryption on the grid at a nozzle; s3, setting boundary conditions; s4, under the condition that the boundary conditions in the S3 are met, different nozzle angles and pressure values are substituted, and the velocity field and the pressure field of the surface of the strip steel are solved; a group of nozzle parameters with the optimal purging effect are obtained by comparing different velocity fields and pressure fields; and S5, the nozzle parameters, obtained through simulation in the step S4, with the optimal purging effect are input into nozzle equipment to conduct purging on the surface of the steel strip. The structure parameter optimization in the purging process is realized by changing the purging angle and pressure of the nozzles, so that the emulsion residue on the steel surface can be effectively reduced by the arrangement of the nozzles and the setting of the pressure in the flat purging process of the strip steel, and the quality of the steel surface is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of purging control in the rolling process and relates to a strip surface purging method based on CFD simulation. Background Art

[0002] With the continuous upgrading and transformation of the steel industry and the improvement of product quality, people's requirements for the surface quality of strips are getting higher and higher. A key factor affecting the strip surface quality is the residual emulsion on the steel surface. If the air purging device cannot effectively purge the emulsion on the rolled plate surface, on the one hand, it will cause the so-called "oil burning" emulsion stains, and on the other hand, too much emulsion will be carried away from the plate surface, increasing the consumption of rolling oil. The residual emulsion on the strip surface affects the strip surface quality, affects the rolling mill thickness control accuracy, increases the production cost, and deteriorates the operating environment.

[0003] The amount of residual emulsion is closely related to the structural parameters of the air purging device in the strip production process. The existing technologies are all about the structural transformation of the air purging device. For example, in the invention patent with the application publication date of August 9, 2024, and the application publication number of CN118455284A, a strip surface purging device is disclosed, including a roll surface purging mechanism and a hot air purging mechanism. The design of the roll surface purging mechanism purges the surface of the work roll to remove the residual emulsion on the work roll surface. The design of the hot air purging mechanism purges the upper and lower surfaces of the strip. Among them, through the design of the hot air box, the air generated by the second air pump can be heated, and hot and dry air is purged. Its temperature is close to the surface temperature of the strip during high-speed movement, and a very small temperature difference will not cause the atomization of the emulsion, thereby improving the purging effect.

[0004] However, the existing technologies improve the purging effect through the structural improvement of the purging device, which has a complex structure, high installation and purchase costs, relatively high requirements for the operation method, and also occupies the working space of the equipment, and cannot be obtained by simply transforming existing old equipment. Summary of the Invention

[0005] The purpose of the present invention is to provide a strip surface purging method based on CFD simulation, which solves the problem of residual emulsion on the steel surface existing in the prior art.

[0006] The technical solution adopted by the present invention is a strip surface purging method based on CFD simulation, which specifically includes the following steps:

[0007] S1. Collect the key parameters during strip purging and establish a simplified purging model;

[0008] S2. Divide the mesh of the simplified purging model, and locally refine the mesh at the nozzle;

[0009] S3. Set boundary conditions;

[0010] S4. Under the boundary conditions in S3, different nozzle angles and pressure values are substituted to solve the velocity field and pressure field on the strip surface; by comparing different velocity fields and pressure fields, a set of nozzle parameters with the optimal purging effect is obtained.

[0011] S5. The nozzle parameters with the optimal purging effect obtained from the simulation in S4 are input into the nozzle device to implement the purging of the strip surface.

[0012] The technical solution of the present invention is also characterized in that:

[0013] The key parameters collected in S1 include: air knife length l, air knife nozzle gap d, distance L from the midpoint of the nozzle to the strip surface, angle α between the central axis of the nozzle and the strip surface, and nozzle pressure P.

[0014] The purging simplified model is constructed in Workbench according to the collected key parameters.

[0015] The mesh element of the model calculation area in S2 is 3 mm; the mesh element at the locally refined area is 0.5 mm.

[0016] In S3, the continuity equation and N-S equation in the time-averaged form are used for setting boundary conditions; the solver is the pressure solver; the turbulence model is the k-ε model.

[0017] The continuity equation in the time-averaged form is as follows:

[0018]

[0019] In the formula, is the density of the fluid, with the unit of kg / m 3 ; is the time-averaged value of the fluid velocity component, with the unit of m / s; t is time, with the unit of s; x i is the spatial coordinate, with the unit of m.

[0020] The N-S equation in the time-averaged form is:

[0021]

[0022] In the formula: is the time-averaged value of the pressure, with the unit of is the dynamic viscosity, with the unit of Pa·s; is the Reynolds stress, with the unit of m 2 / s 2 .

[0023] The transport equation of k in the k-ε model is:

[0024]

[0025] Where: k is the turbulent kinetic energy, m 2 / s 2 ; μ t is the turbulent viscosity, Kg / (m·s); σ k is the Prandtl constant, usually taken as 0.1; P k is the generation term of the turbulent kinetic energy, Kg / (m·s 3 ); ε is the turbulent dissipation rate, m 2 / s 3 ;

[0026] The transport equation of ε is:

[0027]

[0028] Where: σ ε is the Prandtl constant, usually taken as 1.3; C1 and C2 are empirical constants, and the common values are C1≈1.44, C2≈1.92.

[0029] The beneficial effects of the present invention are:

[0030] The present invention establishes a nozzle purging model for strip steel during temper rolling and purging. Based on the principle of computational fluid dynamics, a velocity field and pressure field model for the purging process is constructed. By changing the nozzle purging angle and pressure, the structural parameters during purging are optimized, enabling the nozzle arrangement and pressure setting during the temper rolling and purging of strip steel to effectively reduce the emulsion residue on the steel surface, improve the steel surface quality, and without the need to modify the purging equipment, improve the purging effect without generating additional costs and without occupying additional space, and the purging effect of old equipment can also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic flow chart of the strip steel surface purging method based on CFD simulation of the present invention;

[0032] Figure 2 is a schematic diagram of the purging simplified model and nozzle parameters in the strip steel surface purging method based on CFD simulation of the present invention;

[0033] Figure 3 is the grid division of the purging simplified model in the strip steel surface purging method based on CFD simulation of the present invention;

[0034] Figure 4 is the velocity contour map of the cross-section where the plate width direction is equal to 0 at a nozzle angle of 60° in the present invention;

[0035] Figure 5 is the velocity contour map of the cross-section where the plate width direction is equal to 0 at a nozzle angle of 90° in the present invention;

[0036] Figure 6 It is the velocity contour map of the cross-section where the width along the plate is equal to 0 at a 45° nozzle angle in the present invention;

[0037] Figure 7 It is the velocity contour map of the cross-section where the width along the plate is equal to 0 at a 30° nozzle angle in the present invention;

[0038] Figure 8 It is the pressure contour map of the cross-section where the width along the plate is equal to 0 at a 60° nozzle angle in the present invention;

[0039] Figure 9 It is the pressure contour map of the cross-section where the width along the plate is equal to 0 at a 90° nozzle angle in the present invention;

[0040] Figure 10 It is the pressure contour map of the cross-section where the width along the plate is equal to 0 at a 45° nozzle angle in the present invention;

[0041] Figure 11 It is the pressure contour map of the cross-section where the width along the plate is equal to 0 at a 30° nozzle angle in the present invention;

[0042] Figure 12 It is the volume fraction contour map of the water on the strip surface at the moment of 0.005s at a 60° nozzle angle in the present invention;

[0043] Figure 13 It is the volume fraction contour map of the water on the strip surface at the moment of 0.01s at a 60° nozzle angle in the present invention;

[0044] Figure 14 It is the volume fraction contour map of the water on the strip surface at the moment of 0.015s at a 60° nozzle angle in the present invention;

[0045] Figure 15 It is the volume fraction contour map of the water on the strip surface at the moment of 0.02s at a 60° nozzle angle in the present invention;

[0046] Figure 16 It is the volume fraction contour map of the water on the strip surface at the moment of 0.005s at a 90° nozzle angle in the present invention;

[0047] Figure 17 It is the volume fraction contour map of the water on the strip surface at the moment of 0.01s at a 90° nozzle angle in the present invention;

[0048] Figure 18 It is the volume fraction contour map of the water on the strip surface at the moment of 0.015s at a 90° nozzle angle in the present invention;

[0049] Figure 19 It is the volume fraction contour map of the water on the strip surface at the moment of 0.02s at a 90° nozzle angle in the present invention;

[0050] Figure 20 It is the volume fraction contour map of the water on the strip surface at the moment of 0.005s under the 45° nozzle angle of the present invention;

[0051] Figure 21 It is the volume fraction contour map of the water on the strip surface at the moment of 0.01s under the 45° nozzle angle of the present invention;

[0052] Figure 22 It is the volume fraction contour map of the water on the strip surface at the moment of 0.015s under the 45° nozzle angle of the present invention;

[0053] Figure 23 It is the volume fraction contour map of the water on the strip surface at the moment of 0.02s under the 45° nozzle angle of the present invention;

[0054] Figure 24 It is the volume fraction contour map of the water on the strip surface at the moment of 0.005s under the 30° nozzle angle of the present invention;

[0055] Figure 25 It is the volume fraction contour map of the water on the strip surface at the moment of 0.01s under the 30° nozzle angle of the present invention;

[0056] Figure 26 It is the volume fraction contour map of the water on the strip surface at the moment of 0.015s under the 30° nozzle angle of the present invention;

[0057] Figure 27 It is the volume fraction contour map of the water on the strip surface at the moment of 0.02s under the 30° nozzle angle of the present invention;

[0058] Figure 28 It is the volume fraction contour map of the water on the strip surface at the moment of 0.005s under the 90° nozzle angle and 0.05MPa pressure of the present invention;

[0059] Figure 29 It is the volume fraction contour map of the water on the strip surface at the moment of 0.01s under the 90° nozzle angle and 0.05MPa pressure of the present invention;

[0060] Figure 30 It is the volume fraction contour map of the water on the strip surface at the moment of 0.015s under the 90° nozzle angle and 0.05MPa pressure of the present invention;

[0061] Figure 31 It is the volume fraction contour map of the water on the strip surface at the moment of 0.02s under the 90° nozzle angle and 0.05MPa pressure of the present invention;

[0062] Figure 32 It is the volume fraction contour map of the water on the strip surface at the moment of 0.005s under the 90° nozzle angle and 0.15MPa pressure of the present invention;

[0063] Figure 33 This is the volume fraction contour map of water on the strip surface at the moment of 0.01 s under the nozzle angle of 90° and pressure of 0.15 MPa of the present invention;

[0064] Figure 34 This is the volume fraction contour map of water on the strip surface at the moment of 0.015 s under the nozzle angle of 90° and pressure of 0.15 MPa of the present invention;

[0065] Figure 35 This is the volume fraction contour map of water on the strip surface at the moment of 0.02 s under the nozzle angle of 90° and pressure of 0.15 MPa of the present invention. Detailed implementation manners

[0066] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0067] In order to effectively simulate the external gas flow field of the nozzle, a relatively large external calculation area is connected at the nozzle outlet. The simplified nozzle purge model is imported into Workbench, and the boundary conditions are set to calculate the velocity field and pressure field under different nozzle angles and pressures.

[0068] As Figure 1 shown, the strip surface purge method based on CFD simulation provided by the present invention is specifically implemented according to the following steps:

[0069] S1. Collect the key parameters during strip purging and establish a simplified purge model;

[0070] The collected parameters mainly include: air knife length l, air knife nozzle gap d, distance L from the middle point of the nozzle to the strip surface, angle α、 between the middle axis of the nozzle and the strip surface, and nozzle pressure P; a simplified nozzle purge model is formed in Workbench according to the collected data.

[0071] S2. Mesh the simplified purge model. In order to make the simulation results more accurate, the mesh at the nozzle needs to be locally refined;

[0072] The mesh unit of the model calculation area is 3 mm; the mesh unit at the locally refined area is 0.5 mm.

[0073] S3. Set the boundary conditions;

[0074] Based on the basic requirements of computational fluid dynamics (CFD), the fluid equations used in the present invention include the continuity equation and the N - S equation (Navier - Stokes equation); the solver is a pressure solver; the turbulence model adopts the k - ε model;

[0075] Ensure the conservation of fluid mass during the simulation through the time - averaged continuity equation to avoid unreasonable mass loss or accumulation;

[0076] The time-averaged form of the continuity equation is as follows:

[0077]

[0078] In the formula, is the density of the fluid, with the unit of kg / m 3 ; is the time-averaged value of the fluid velocity component, with the unit of m / s; t is the time, with the unit of s; x i is the spatial coordinate, with the unit of m;

[0079] The Navier-Stokes equation is the core equation in fluid simulation, used to describe the velocity field and pressure field of the fluid. In fluid finite element software, it is used to calculate the main characteristics of fluid flow, such as velocity distribution, pressure distribution, shear stress, etc. It is applicable to Newtonian fluids, considering turbulence, and incompressible fluids;

[0080] The time-averaged form of the N-S equation is:

[0081]

[0082] In the formula: is the time-averaged value of the pressure, with the unit of kg / (m·s 2 ); is the dynamic viscosity, with the unit of Pa·s; is the Reynolds stress, with the unit of m 2 / s 2 ;

[0083] The k-ε turbulence model is a time-averaged model. Through the two equations of turbulent kinetic energy k and turbulent kinetic energy dissipation rate ε, we can well approximate the behavior of turbulence in industrial flow calculations, and the numerical solution process is relatively simple, suitable for various complex flow problems;

[0084] The turbulent kinetic energy k describes the energy magnitude in turbulent flow, generated by vortices in the fluid (local rotation of turbulent flow), aiming to describe the change of turbulent kinetic energy, including the generation, dissipation, and diffusion of turbulence;

[0085] The transport equation of k is:

[0086]

[0087] In the formula: k is the turbulent kinetic energy, m 2 / s 2 ; μ t is the turbulent viscosity, Kg / (m·s); σ k is the Prandtl constant, usually taking the value of 0.1; P kis the generation term of turbulent kinetic energy, Kg / (m·s 3 );ε is the turbulent dissipation rate, m 2 / s 3 ;

[0088] The turbulent dissipation rate ε describes the rate at which turbulent energy is converted into heat energy. Specifically, it reflects the energy dissipation process of small-scale vortices in the turbulence. Turbulent energy is gradually converted into molecular thermal motion due to internal friction;

[0089] The transport equation of ε is:

[0090]

[0091] In the formula: σ ε is the Planck constant, usually taking a value of 1.3; C1 and C2 are empirical constants, and common values are C1≈1.44 and C2≈1.92.

[0092] S4. Under the boundary conditions in S3, input different sets of nozzle parameters to obtain the velocity field and pressure field on the strip surface; by comparing different velocity fields and pressure fields, obtain a set of nozzle parameters with the optimal purging effect;

[0093] The nozzle parameters include the nozzle angle and the nozzle pressure.

[0094] S5. Input the nozzle parameters with the optimal purging effect obtained from the simulation in S4 into the nozzle device to perform purging on the strip surface.

[0095] Example 1

[0096] In this example, the parameters of the skin pass purging equipment used are that the nozzle uses an air knife nozzle, the air knife length l = 258 mm, and the air knife nozzle gap d = 2 mm.

[0097] The strip surface purging method based on CFD simulation is specifically implemented according to the following steps:

[0098] S1. Collect the key parameters during strip purging and establish a simplified purging model;

[0099] The main parameters collected during the skin pass purging process are the air knife length l = 258 mm, the air knife nozzle gap d = 2 mm, the distance L from the midpoint of the nozzle to the strip surface = 120 mm, the angle α between the central axis of the nozzle and the strip surface = 60°, and the nozzle pressure P = 0.1 MPa;

[0100] As Figure 2 shown, in the workbench software, connect a larger calculation area outside the nozzle according to the above parameters as the simplified purging model;

[0101] S2. Mesh the simplified purging model, and locally refine the mesh at the nozzle.

[0102] As Figure 3 shown, the mesh element in the nozzle area is 0.5 mm, and the mesh element in the external calculation area is 3 mm.

[0103] S3. Set the boundary conditions.

[0104] S4. Under the boundary conditions in S3, substitute different nozzle angles and pressure values, and solve the velocity field and pressure field on the strip surface; by comparing different velocity fields and pressure fields, obtain a set of nozzle parameters with the optimal purging effect.

[0105] Figure 4 is the velocity contour map of the cross-section equal to 0 along the strip width direction at the nozzle angle α = 60° and the nozzle pressure P = 0.1 MPa.

[0106] Figure 8 is the pressure contour map of the cross-section equal to 0 along the strip width direction at the nozzle angle α = 60° and the nozzle pressure P = 0.1 MPa.

[0107] S5. Input the nozzle parameters with the optimal purging effect obtained from the simulation in S4 into the nozzle device to implement the purging of the steel strip surface.

[0108] Verify the simulation effect:

[0109] Set a 2-mm water film on the steel plate surface to replace the emulsion to simulate the emulsion residue on the strip surface during the actual purging process.

[0110] Figure 12 ., Figure 13 ., Figure 14 and Figure 15 are the volume fraction contour maps of water on the strip surface at different times of 0.005 s, 0.01 s, 0.015 s, and 0.02 s at the nozzle angle α = 60° and the nozzle pressure P = 0.1 MPa, respectively, which can prove that a better purging effect can be obtained by the method of the present invention.

[0111] Example 2

[0112] In this example, the parameters of the temper mill purging equipment used are as follows: the nozzle is an air knife nozzle, the air knife length l = 258 mm, and the air knife nozzle gap d = 2 mm.

[0113] The method for purging the strip surface based on CFD simulation is specifically implemented according to the following steps:

[0114] S1. Collect the key parameters during strip purging and establish a simplified purging model.

[0115] The relevant parameters during the collection, leveling, and purging process are mainly: the length of the air knife \(l = 258\) mm, the gap of the air knife nozzle \(d = 2\) mm, the distance from the midpoint of the nozzle to the strip surface \(L = 120\) mm, the angle \(\alpha\) between the central axis of the nozzle and the strip surface is \(90^{\circ}\), and the nozzle pressure \(P = 0.1\) MPa;

[0116] As Figure 2 shown, in the workbench software, connect a larger calculation area outside the nozzle according to the above parameters as the purging simplified model;

[0117] S2. Mesh the purging simplified model, and locally refine the mesh at the nozzle.

[0118] As Figure 3 shown, the mesh element of the nozzle area is 0.5 mm, and the mesh element of the external calculation area is 3 mm;

[0119] S3. Set the boundary conditions;

[0120] S4. Under the boundary conditions in S3, substitute different nozzle angles and pressure values, and solve the velocity field and pressure field on the strip surface; by comparing different velocity fields and pressure fields, obtain a set of nozzle parameters with the optimal purging effect;

[0121] Figure 5 is the velocity contour at the cross-section where the plate width direction is equal to 0 under the nozzle angle \(\alpha = 90^{\circ}\) and nozzle pressure \(P = 0.1\) MPa;

[0122] Figure 9 is the pressure contour at the cross-section where the plate width direction is equal to 0 under the nozzle angle \(\alpha = 90^{\circ}\) and nozzle pressure \(P = 0.1\) MPa;

[0123] S5. Input the nozzle parameters with the optimal purging effect obtained from the simulation in S4 into the nozzle device to implement the purging of the steel strip surface.

[0124] Verify the simulation effect:

[0125] Set a 2-mm water film on the steel plate surface to replace the emulsion to simulate the emulsion residue on the strip surface during the actual purging process;

[0126] Figure 16 、 Figure 17 、 Figure 18 and Figure 19 are the volume fraction contours of water on the strip surface at different times of 0.005 s, 0.01 s, 0.015 s, and 0.02 s under the nozzle angle \(\alpha = 90^{\circ}\) and nozzle pressure \(P = 0.1\) MPa, respectively, which can prove that a better purging effect can be obtained through the method of the present invention.

[0127] Example 3

[0128] In this example, the parameters of the skin pass mill blowing equipment are as follows: the nozzle uses an air knife nozzle, the length of the air knife l = 258 mm, and the gap of the air knife nozzle d = 2 mm.

[0129] The strip surface blowing method based on CFD simulation is specifically implemented according to the following steps:

[0130] S1. Collect the key parameters during strip blowing and establish a simplified blowing model;

[0131] The relevant parameters collected during the skin pass blowing process are mainly the length of the air knife l = 258 mm, the gap of the air knife nozzle d = 2 mm, the distance L from the midpoint of the nozzle to the strip surface = 120 mm, the angle α between the central axis of the nozzle and the strip surface = 45°, and the nozzle pressure P = 0.1 MPa;

[0132] As Figure 2 shown, in the workbench software, connect a larger calculation area outside the nozzle according to the above parameters as the simplified blowing model;

[0133] S2. Mesh the simplified blowing model, and locally refine the mesh at the nozzle.

[0134] As Figure 3 shown, divide the model into tetrahedral meshes, the mesh element in the nozzle area is 0.5 mm, and the mesh element in the external calculation area is 3 mm;

[0135] S3. Set the boundary conditions;

[0136] S4. Under the boundary conditions in S3, substitute different nozzle angles and pressure values to solve the velocity field and pressure field on the strip surface; by comparing different velocity fields and pressure fields, obtain a set of nozzle parameters with the best blowing effect;

[0137] Figure 6 is the velocity contour at the cross-section equal to 0 along the strip width direction under the nozzle angle α = 45° and the nozzle pressure P = 0.1 MPa;

[0138] Figure 10 is the pressure contour at the cross-section equal to 0 along the strip width direction under the nozzle angle α = 45° and the nozzle pressure P = 0.1 MPa;

[0139] S5. Input the nozzle parameters with the best blowing effect obtained from the simulation in S4 into the nozzle equipment to blow the strip surface.

[0140] Verify the simulation effect:

[0141] Set a 2-mm water film on the steel plate surface to replace the emulsion to simulate the emulsion residue on the strip surface during the actual blowing process;

[0142] Figure 20 and Figure 21 and Figure 22 and Figure 23 are respectively the contour maps of the volume fraction of water on the strip surface at different times of 0.005 s, 0.01 s, 0.015 s and 0.02 s under the nozzle angle α = 45° and the nozzle pressure P = 0.1 MPa. It can be proved from this that a better purging effect can be obtained by the method of the present invention.

[0143] Example 4

[0144] In this example, the parameters of the skin pass purging equipment adopted are that the nozzle uses an air knife nozzle, the air knife length l = 258 mm, and the air knife nozzle gap d = 2 mm.

[0145] The strip surface purging method based on CFD simulation is specifically implemented according to the following steps:

[0146] S1. Collect the key parameters during strip purging and establish a simplified purging model;

[0147] The relevant parameters collected during skin pass purging are mainly the air knife length l = 258 mm, the air knife nozzle gap d = 2 mm, the distance L from the middle point of the nozzle to the strip surface = 120 mm, the angle α between the middle axis of the nozzle and the strip surface = 30°, and the nozzle pressure P = 0.1 MPa;

[0148] As Figure 2 shown, connect a larger calculation area outside the nozzle in the workbench software according to the above parameters as the simplified purging model;

[0149] S2. Mesh the simplified purging model, and local encryption should be performed on the mesh at the nozzle;

[0150] As Figure 3 shown, divide the model into tetrahedral meshes, the mesh element of the nozzle area is 0.5 mm, and the mesh element of the external calculation area is 3 mm;

[0151] S3. Set the boundary conditions;

[0152] S4. Under the boundary conditions in line with S3, substitute different nozzle angles and pressure values, and solve the velocity field and pressure field on the strip surface; by comparing different velocity fields and pressure fields, a set of nozzle parameters with the best purging effect is obtained;

[0153] Figure 7 is the velocity contour map of the cross-section equal to 0 along the strip width direction under the nozzle angle α = 30° and the nozzle pressure P = 0.1 MPa;

[0154] Figure 11It is the pressure contour map at the cross-section equal to 0 along the width direction of the plate under the nozzle angle α = 30° and the nozzle pressure P = 0.1 MPa;

[0155] S5. Input the nozzle parameters with the optimal purging effect obtained from the simulation in S4 into the nozzle device to perform purging on the surface of the steel strip.

[0156] Verify the simulation effect:

[0157] Set a 2-mm water film on the surface of the steel plate to replace the emulsion to simulate the emulsion residue on the surface of the strip during the actual purging process;

[0158] Figure 24 、 Figure 25 、 Figure 26 and Figure 27 are the volume fraction contour maps of water on the surface of the strip at different times of 0.005 s, 0.01 s, 0.015 s, and 0.02 s under the nozzle angle α = 30° and the nozzle pressure P = 0.1 MPa, from which it can be proved that a better purging effect can be obtained by the method of the present invention.

[0159] Example 5

[0160] In this example, the parameters of the skin pass purging equipment adopted are that the nozzle uses an air knife nozzle, the air knife length l = 258 mm, and the air knife nozzle gap d = 2 mm.

[0161] The strip surface purging method based on CFD simulation is specifically implemented according to the following steps:

[0162] Collect the relevant parameters during the skin pass purging process, mainly including the air knife length l = 258 mm, the air knife nozzle gap d = 2 mm, the distance L from the midpoint of the nozzle to the strip surface = 120 mm, the angle α between the middle axis of the nozzle and the strip surface = 90°, and the nozzle pressure P = 0.05 MPa;

[0163] As Figure 2 shown, connect a larger calculation area outside the nozzle in the workbench software according to the above parameters as a purging simplified model.

[0164] S2. Mesh the purging simplified model, and local refinement should be performed on the mesh at the nozzle;

[0165] As Figure 3 shown, divide the model into tetrahedral meshes, with the mesh element in the nozzle area being 0.5 mm and the mesh element in the external calculation area being 3 mm.

[0166] S3. Set the boundary conditions.

[0167] S4. Under the boundary conditions in S3, substitute different nozzle angles and pressure values to solve the velocity field and pressure field on the strip surface; by comparing different velocity fields and pressure fields, obtain a set of nozzle parameters with the optimal purging effect.

[0168] S5. Input the nozzle parameters with the optimal purging effect obtained from the simulation in S4 into the nozzle device to implement the purging of the strip surface.

[0169] Verify the simulation effect:

[0170] Set a 2-mm water film on the steel plate surface to replace the emulsion to simulate the emulsion residue on the strip surface during the actual purging process.

[0171] Figure 28 、 Figure 29 、 Figure 30 and Figure 31 are the contour maps of the volume fraction of water on the strip surface at different times of 0.005 s, 0.01 s, 0.015 s, and 0.02 s when the nozzle angle α = 90° and the nozzle pressure P = 0.05 MPa. It can be proved that better purging effects can be obtained by the method of the present invention.

[0172] Example 6

[0173] In this example, the parameters of the skin pass purging equipment used are as follows: the nozzle is an air knife nozzle, the air knife length l = 258 mm, and the air knife nozzle gap d = 2 mm.

[0174] The strip surface purging method based on CFD simulation is specifically implemented according to the following steps:

[0175] Collect the relevant parameters during the skin pass purging process, mainly including the air knife length l = 258 mm, the air knife nozzle gap d = 2 mm, the distance L from the midpoint of the nozzle to the strip surface = 120 mm, the angle α between the middle axis of the nozzle and the strip surface = 90°, and the nozzle pressure P = 0.15 MPa.

[0176] S2. Divide the mesh of the purging simplified model, and locally refine the mesh at the nozzle.

[0177] As Figure 3 shown, divide the model into tetrahedral meshes, with the mesh element in the nozzle area being 0.5 mm and the mesh element in the external calculation area being 3 mm.

[0178] S3. Set the boundary conditions.

[0179] S4. Under the boundary conditions in S3, substitute different nozzle angles and pressure values to solve the velocity field and pressure field on the strip surface; by comparing different velocity fields and pressure fields, obtain a set of nozzle parameters with the optimal purging effect.

[0180] S5. Input the nozzle parameters with the optimal purging effect obtained from S4 into the nozzle device to perform purging on the surface of the steel strip.

[0181] Verify the simulation effect:

[0182] Set a 2 - mm water film on the surface of the steel plate to replace the emulsion to simulate the emulsion residue on the surface of the strip during the actual purging process;

[0183] Figure 32 、 Figure 33 、 Figure 34 and Figure 35 are the contour maps of the volume fraction of water on the surface of the strip at different times of 0.005 s, 0.01 s, 0.015 s, and 0.02 s when the nozzle angle α = 90° and the nozzle pressure P = 0.15 MPa. Thus, it can be proved that a better purging effect can be obtained by the method of the present invention.

[0184] In summary, as can be seen from Figures 4 - 7 , when the nozzle purges obliquely, the velocity will no longer be symmetrically distributed about the impact point. After the air flow impacts the steel plate, a large amount of air flow will flow to the right side (+y direction) of the impact point. Under the condition of the same flow rate, the smaller the incident angle, the more air flow will flow to the right side.

[0185] As can be seen from Figures 8 - 11 , when the air flow blows onto the steel plate, through the conversion of momentum, a certain impact force is exerted on the steel plate near the impact point. As the incident angle decreases, the maximum pressure point moves more towards the negative direction of the y - axis, and as the incident angle decreases, the pressure also decreases. This is because the decrease in the incident angle will generate air flow in the horizontal direction, resulting in a weakening of the impact force of the vertical air flow on the steel plate.

[0186] As can be seen from Figures 12 - 27 , the water on the surface of the steel plate is blown off first at the place far from the center point. This is because the farther away from the center point, the greater the purging speed, indicating that there is a great correlation between the purging effect and the purging speed. The greater the air flow speed, the earlier the moisture is blown off the surface of the steel plate.

[0187] Under vertical purging, the region where the moisture is blown off first is approximately symmetric about the center point, while under an inclined nozzle, the region where the moisture is blown off first always starts from below (Y < 0). This is because when the incident angles are 60°, 45°, and 30°, the maximum pressure on the steel plate is always at a certain point in the negative direction of the y - axis. The greater the pressure, the greater the impact force on the surface of the steel plate, and the easier the moisture is to detach from the surface of the steel plate.

[0188] As can be seen from Figures 28 - 35 , the purging effect is positively correlated with the nozzle pressure. The greater the nozzle pressure, the less free emulsion on the surface of the strip, and the better the purging effect.

Claims

1. Strip surface blowing method based on CFD simulation, characterized in that, The implementation is specifically carried out according to the following steps: S1. Collect the key parameters during strip blowing and establish a simplified blowing model; S2. Divide the grid of the simplified blowing model, and locally refine the grid at the nozzle; S3. Set the boundary conditions; S4. Under the boundary conditions in S3, substitute different nozzle angles and pressure values to solve the velocity field and pressure field on the strip surface; By comparing different velocity fields and pressure fields, obtain a set of nozzle parameters with the optimal blowing effect; S5. Input the nozzle parameters with the optimal blowing effect obtained from the simulation in S4 into the nozzle device to implement the blowing on the strip surface.

2. The strip surface blowing method based on CFD simulation according to claim 1, characterized in that The key parameters include: air knife length l, air knife nozzle gap d, distance L from the middle point of the nozzle to the strip surface, angle α between the middle axis of the nozzle and the strip surface, and nozzle pressure P.

3. The strip surface purging method based on CFD simulation according to claim 2, characterized in that The simplified blowing model is constructed in Workbench software based on the collected key parameters.

4. The strip surface blowing method based on CFD simulation according to claim 3, characterized in that The grid division parameters in S2 are: the grid element of the calculation area is 3 mm; the grid element of the locally refined area is 0.5 mm.

5. The strip surface blowing method based on CFD simulation according to claim 1, characterized in that, The boundary conditions are the time-averaged form of the continuity equation and the N-S equation; the turbulence model is the k-ε model; the solver is the pressure solver.

6. The strip surface blowing method based on CFD simulation according to claim 5, characterized in that The time-averaged form of the continuity equation is as follows: In the formula, is the density of the fluid, with the unit of kg / m 3 ; is the time-averaged value of the fluid velocity component, with the unit of m / s; t is the time, with the unit of s; x i is the spatial coordinate, with the unit of m.

7. The strip surface purging method based on CFD simulation according to claim 5, wherein The time-averaged form of the N-S equation is: In the formula: is the time-averaged value of pressure, with the unit of kg / (m·s 2 ); is the dynamic viscosity, with the unit of Pa·s; is the Reynolds stress, with the unit of m 2 / s 2 .

8. The strip surface blowing method based on CFD simulation according to claim 5, wherein The transport equation of k in the k-ε model is: where: k is the turbulent kinetic energy, m 2 / s 2 ; μ t is the turbulent viscosity, Kg / (m·s); σ k is the Prandtl constant, usually taken as 0.1; P k is the generation term of the turbulent kinetic energy, Kg / (m·s 3 ); ε is the turbulent dissipation rate, m 2 / s 3 ; The transport equation of ε is: where: σ ε is the Planck constant, usually taken as 1.3; C1 and C2 are empirical constants, and common values are C1 ≈ 1.44 and C2 ≈ 1.92.

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