Anti-impact optimization method for floating disc of floating roof oil storage tank

Abstract

According to the anti-impact optimization method for the floating disc of the floating roof oil storage tank, the process that the oil flow impacts the floating disc in the oil receiving operation of the storage tank is simulated by adopting a mathematical model and a solution algorithm in Ansys Fluent software, and the pressure intensity distribution, the maximum impact pressure intensity and the impact force of the oil flow impacting the floating disc in the oil receiving process can be obtained; and the easily-deformed position of the floating disc is found according to the obtained pressure distribution, the maximum impact pressure and the impact force, so that the easily-deformed position of the floating disc can be protected, the anti-impact performance of the floating disc is optimized, and the floating disc is prevented from being damaged.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical storage and transportation equipment, and in particular to an anti-impact optimization method for a floating plate of a floating roof oil storage tank. Background Art

[0002] Floating roof tanks are widely used in refinery oil depots, finished oil transfer depots, and finished oil sales depots, especially in the storage of highly volatile oil products such as gasoline, kerosene, diesel, and naphtha. However, when the liquid level in the tank is low for receiving and sending oil, it is very easy to form turbulence and impact the floating plate, resulting in uneven force on the floating plate, causing large-scale damage to the floating plate. The oil and gas will diffuse from the damaged part of the floating plate to the oil and gas space under the tank top, and then leak into the atmosphere from the vent, which will not only cause a waste of resources, but also cause great pollution to the environment. If it encounters lightning strikes or static induction of thunderclouds, it will catch fire and explode, causing serious economic losses. Although lower speed conditions and high-stability floating plates have been used for receiving and sending oil, floating plate damage and sinking accidents still occur from time to time.

[0003] In order to monitor the operation status of the floating plate of the floating roof tank, the Chinese utility model patent with the announcement number CN206318276U discloses an improved internal floating roof tank floating plate monitoring device, an observation window is installed on the light-transmitting hole of the internal floating roof tank, and the floating plate inside the tank is monitored through the observation window on the light-transmitting hole, which is convenient for daily monitoring of the operation status of the internal floating roof floating plate. The Chinese utility model patent with the announcement number CN206798261U discloses a fault self-alarm internal floating plate. When the internal floating plate sinks, the oil presses the elastic waterproof membrane to extend inside the first shell, the left conductor block contacts the right conductor block, and the power supply and buzzer are connected to trigger the alarm. When the internal floating plate is chucked, the liquid level is separated from the floating block, and the magnetic repulsion of the driven block on the driven slider is reduced after the driving block descends. The first spring presses the conductor bar to connect the left contact and the right contact, and the power supply and buzzer are connected to trigger the alarm. The Chinese invention patent application with publication number CN109932020A discloses a floating plate position monitoring system and monitoring method for an internal floating roof tank, which can monitor the operation status of the floating plate in real time. The Chinese invention patent application with publication number CN105236042A discloses an anti-impact safety device for the internal floating roof of a storage tank. The use of an air equalization device can make the exhaust uniform during the line sweeping operation to avoid damage to the internal floating roof. The degassing and exhaust device on the internal floating roof is usually in a closed state. When the storage tank is performing a line sweeping operation, the device automatically opens, separates the gas carrying the stored liquid from gas and liquid, and discharges the gas in an orderly manner to avoid the occurrence of floating plate flooding and sinking accidents.

[0004] In the prior art, although corresponding measures have been taken to monitor the operation status of the floating plate, the problems behind the technical bottlenecks that affect the damage of the floating plate have not been solved. Determining the degree of influence of the oil flow of the oil collection operation on the impact of the floating plate, that is, the magnitude of the impact pressure and impact force and the position of the floating plate that is easily deformed under the impact of the oil flow, the clarification of the above conclusions is of great significance to the protection of the floating plate, pollution control and tank area safety. Summary of the invention

[0005] The present invention provides an anti-impact optimization method for a floating plate of a floating roof oil storage tank, which can obtain the pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow during the oil collection process, and find the easily deformed position of the floating plate according to the obtained pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow, so that the easily deformed position of the floating plate can be protected, thereby avoiding damage to the floating plate.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for optimizing the impact resistance of a floating plate of a floating roof oil storage tank comprises the following steps:

[0008] S1, Geometric modeling of floating roof oil storage tanks: The tank body below the floating plate of the floating roof storage tank is taken as the research object. The Ansys Spacecliam modeling software in the Ansys Workbench finite element analysis software is used to establish a physical model of the oil flow impacting the floating plate during the three-dimensional oil collection process for the fluid domain and oil inlet wrapped by the floating plate and the tank body below the floating plate. The movement of the floating plate is defined by the dynamic mesh model and program source file in the Ansys Fluent computational fluid dynamics software;

[0009] S2, structured meshing: Ansys Meshing software is used to perform structured meshing on the physical model of oil flow impacting the floating plate in the three-dimensional oil collection process. The mesh at the oil inlet is encrypted by changing the mesh size and adding a boundary layer.

[0010] S3, if the mesh unit quality is greater than or equal to 0.75, the main mesh aspect ratio is less than or equal to 5, and the mesh aspect ratio in the boundary layer is less than or equal to 100, proceed to step S4, otherwise return to step S2 to adjust the mesh size again;

[0011] S4, importing the mesh file divided by Ansys Meshing software into Ansys Fluent, using Ansys Fluent software to numerically simulate the impact characteristics of the oil flow impacting the floating plate during the oil collection process of the floating roof oil storage tank, so as to calculate the pressure distribution, maximum impact pressure and impact force value of the floating plate impacted by the oil flow during the oil collection process of the floating roof oil storage tank;

[0012] S5, finding the easily deformed position of the floating plate according to the obtained pressure distribution, maximum impact pressure and impact force value of the floating plate impacted by the oil flow, so as to protect the easily deformed position of the floating plate.

[0013] Further, step S4 includes the following steps:

[0014] S41, importing the mesh file divided by Ansys Meshing software into Ansys Fluent and checking the size range of the physical model and the mesh. If the minimum volume of the mesh is a positive value, the size of the physical model is consistent with the size range of the physical model set during modeling, and the boundary condition definition is correct, proceed to step S42;

[0015] S42, select a transient solver, select the pressure-velocity coupling PISO algorithm as the transient calculation method, set the gravity acceleration value, select a turbulence model, and set the oil product physical property parameters, unit area conditions, initial conditions and boundary conditions, and dynamic mesh parameters of the dynamic mesh model;

[0016] S43, setting two monitoring values ​​of the maximum impact pressure and impact force of the oil flow impacting the floating plate at different times in the report definition;

[0017] S44, setting the sub-relaxation factor and the residual absolute standard value, and determining the time step, the number of time steps and the maximum number of iterations according to the convergence of the discrete method;

[0018] S45, Ansys Fluent software discretizes the fluid domain of the physical model through the finite volume method, obtains the unsteady discrete equations that control the volume of the grid and the internal nodes, and then uses the pressure-velocity coupling PISO algorithm to solve the unsteady discrete equations until convergence:

[0019] When the residual values ​​of the variables in the continuity equation, momentum equation, and turbulence equation are reduced to 10 in each time step -3 , and the residual curve is wavy, it is determined to be converged: if converged, complete the simulation calculation, and obtain the pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow during the oil collection process of the floating roof oil storage tank; if not, return to step S2 to re-divide the grid to improve the grid quality, or return to step S44 to readjust the sub-relaxation factor until convergence.

[0020] Furthermore, the oil product related parameters in step S42 are the actual density and viscosity values ​​of the oil product added to the floating roof oil storage tank; the setting of the initial condition refers to determining the initial liquid level.

[0021] Furthermore, in step S42, the setting of boundary conditions includes: setting of inlet boundary conditions, setting of floating plate rising speed and setting of wall boundary conditions. When setting, the velocity inlet is used as the inlet boundary condition, and the oil inlet speed is set; the tank bottom, tank wall and floating plate are set as wall boundary conditions.

[0022] Furthermore, the following formula (1) is used as the calculation formula for the floating plate rising speed:

[0023] According to the continuity equation, the volume flow rate of the oil product flowing into the tank inlet is converted into the rising speed of the floating plate. The calculation formula is:

[0024]

[0025] Where: d 1 is the oil inlet of the tank, i.e. the diameter of the velocity inlet, d 2 is the diameter of the floating roof tank, u 1 is the oil inlet speed, u 2 is the rising speed of the floating plate.

[0026] Furthermore, the continuity equation in step S45 is:

[0027] The oil stored in the floating roof tank is an incompressible fluid. Any flow process must satisfy the law of conservation of mass. The continuity equation is:

[0028]

[0029] In the formula, u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 .

[0030] Furthermore, in step S42, a layering method is selected to merge and split the mesh of the fluid domain according to the movement of the floating plate, and the floating plate is set as a rigid body; the dynamic mesh parameters are set as follows: the mesh height is 0.07 m, the splitting factor is 0.4, and the merging factor is 0.2.

[0031] Furthermore, the momentum equation in step S45 is:

[0032] The flow process of oil in the floating roof tank must satisfy the law of conservation of momentum. The momentum equation is:

[0033]

[0034]

[0035] Where ρ is the oil density, unit: kg·m -3; p is the static pressure of the oil, unit is Pa; μ is the dynamic viscosity of the oil, unit is kg·(m·s) -1 ; t is the oil flow time, unit is s; g is the gravity acceleration of the oil, unit is m·s -2 ;u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 .

[0036] Furthermore, in step S42, the turbulence model selects the Realizable k-ε model and the standard wall function.

[0037] Furthermore, turbulence is composed of vortices of various scales. The oil flow in the floating roof tank oil collection process is turbulent. The Realizable k-ε model widely used in engineering is used to simulate and solve the turbulent problem. The turbulent kinetic energy transport equation of incompressible fluid is as follows:

[0038]

[0039] The dissipative transport equation for incompressible fluid is as follows:

[0040]

[0041] Where ρ is the oil density, unit: kg·m -3 ; p is the static pressure of the oil, unit is Pa; μ is the dynamic viscosity of the oil, unit is kg·(m·s) -1 ; t is the oil flow time, unit is s; g is the gravity acceleration of the oil, unit is m·s -2 ;u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 ; k is the turbulent kinetic energy, ε is the dissipation rate, μ t is the turbulent viscosity, G k represents the turbulent kinetic energy due to the mean velocity gradient, G b represents the turbulent kinetic energy due to buoyancy. For incompressible fluids, G b =0; Y M represents the contribution of pulsating expansion to the overall dissipation rate in compressible flow. For incompressible fluid, Y M =0;σ k and σ ε are the Prandtl numbers corresponding to the turbulent kinetic energy k and the dissipation rate ε, respectively, which can be empirical values; S, S k , S ε is a custom source item; C 1 , C2 , C 1ε , C 3ε is an empirical constant. When the direction of the shear flow is the same as the direction of gravity, C 3ε =1; when the shear flow is perpendicular to the direction of gravity, C 3ε =0; υ is the kinematic viscosity.

[0042] Furthermore, in step S42, the discrete format of the pressure-velocity coupled PISO algorithm is set as follows: the gradient adopts the least squares unit, the pressure adopts the second-order format, the momentum adopts the second-order upwind format, the turbulent kinetic energy and the turbulent dissipation rate both adopt the first-order upwind format, and the time term discrete format adopts the first-order implicit format.

[0043] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0044] The present invention discloses an anti-impact optimization method for a floating plate of a floating roof oil storage tank. The mathematical model and solution algorithm in Ansys Fluent software are used to simulate the process of oil flow impacting the floating plate during the oil collection operation of the storage tank. The pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow during the oil collection operation of the floating roof oil storage tank can be obtained. The easily deformed position of the floating plate can be found according to the obtained pressure distribution, maximum impact pressure and impact force, so that the easily deformed position of the floating plate can be protected, thereby optimizing the anti-impact performance of the floating plate and avoiding damage to the floating plate.

[0045] The present invention provides an anti-impact optimization method for a floating plate of a floating roof oil storage tank. The method simulates the process of oil flow impacting the floating plate during the oil collection operation of the storage tank through the mathematical model and solution algorithm in the Ansys Fluent software, so as to obtain the pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow during the oil collection process of the floating roof oil storage tank. Compared with the method of collecting data through experimental tests on the engineering site, the operation process is simpler and safer, and will not affect the operation of the on-site oil tank, and can reduce the cost of data collection. Moreover, the collected data can be displayed in charts through the Ansys Fluent software, which makes it more convenient for on-site engineering personnel to understand the operating status of the floating plate during the oil collection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of a method for optimizing the anti-impact of a floating plate of a floating roof storage tank according to a preferred embodiment of the present invention;

[0047] Figure 2 It is a structural schematic diagram of a floating roof oil storage tank;

[0048] Figure 3 A physical model diagram of the oil flow impacting the floating plate during the three-dimensional oil collection process established in step S1;

[0049] Figure 4 is a schematic diagram of grid division, where Figure 4 (a) is a schematic diagram of the mesh division of the fluid domain wrapped by the tank part below the floating plate 20. Figure 4 (b) Schematic diagram of the encrypted grid division at the inlet;

[0050] Figure 5 is the pressure distribution diagram of the floating plate at 2.3 m calculated by the CFD-Post software in step S4;

[0051] Figure 6 is a diagram of the maximum impact pressure of the oil flow impacting the floating plate at different times when the floating plate rises from 1.8m to 2.3m, calculated by the CFD-Post software in step S4;

[0052] Figure 7 The impact force diagram of the oil flow impacting the floating plate at different times when the floating plate rises from 1.8m to 2.3m is calculated by the CFD-Post software in step S4;

[0053] In the attached drawings, 100 is a floating roof oil storage tank; 10 is a tank body; 11 is a tank body portion below a floating plate of the floating roof storage tank; 20 is a floating plate; 30 is an oil inlet pipe; and 40 is an oil outlet pipe. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0057] Please also see Figures 1 to 4 A preferred embodiment of the present invention provides an anti-impact optimization method for a floating plate of a floating roof oil storage tank, comprising the following steps:

[0058] S1, geometric modeling of floating roof oil storage tank: the tank body part 11 below the floating plate of the floating roof storage tank is taken as the research object, and the floating roof storage tank can be an external floating roof storage tank or an internal floating roof storage tank; the Ansys Spacecliam modeling software in the Ansys Workbench finite element analysis software is used to establish a physical model of the oil flow impacting the floating plate during the three-dimensional oil collection process for the fluid domain and the oil inlet wrapped by the floating plate 20 and the tank body part 11 below the floating plate 20. The movement of the floating plate is defined by the dynamic mesh model and program source file in the Ansys Fluent computational fluid dynamics software.

[0059] When modeling, a model tank with the same size and shape as the large floating roof storage tank on site was established. Only the impact of turbulence on the floating plate during oil collection was considered, and other factors such as the quality of the floating plate and installation problems, uneven settlement of the tank bottom plate, equipment corrosion, and production operation impact were ignored. In order to facilitate research, the model tank was simplified as necessary to finally obtain a three-dimensional physical model.

[0060] In this embodiment, the tank body 10 of the floating roof oil storage tank 100 is provided with the oil inlet, and the outlet end of the oil inlet pipe 30 is fixed on the tank body 10 and communicated with the oil inlet.

[0061] S2, structured mesh division: Ansys Meshing software is used to perform structured mesh division on the physical model of oil flow impacting the floating plate in the three-dimensional oil collection process. The mesh at the oil inlet is encrypted by changing the mesh size and adding a boundary layer.

[0062] S3, if the mesh unit quality is greater than or equal to 0.75, the main mesh aspect ratio is less than or equal to 5, and the mesh aspect ratio in the boundary layer is less than or equal to 100, proceed to step S4, otherwise return to step S2 to adjust the mesh size again.

[0063] S4, importing the mesh file divided by Ansys Meshing software into Ansys Fluent, using Ansys Fluent software to perform numerical simulation on the impact characteristics of the oil flow impacting the floating plate during the oil collection process of the floating roof oil storage tank, so as to calculate the pressure distribution, maximum impact pressure and impact force value of the floating plate impacted by the oil flow during the oil collection process of the floating roof oil storage tank, including the following steps:

[0064] S41, import the mesh file divided by Ansys Meshing software into Ansys Fluent and check the size range and mesh of the physical model. If the minimum volume of the mesh is a positive value, the size of the physical model is consistent with the size range of the physical model set during modeling, and the boundary conditions are correctly defined, it means that the inspection result meets the standard, and enter step S42. If the inspection result does not meet the standard, it is necessary to return to the above steps to adjust the corresponding parameters until the inspection result meets the standard. For example, it can return to step S2 to re-divide the mesh, or return to the modeling step of step S1 to adjust the physical model or boundary conditions.

[0065] S42, select the transient solver, select the pressure-velocity coupling PISO algorithm as the transient calculation method, set the gravity acceleration value, select the turbulence model, and set the oil physical properties, unit area conditions, initial conditions and boundary conditions, and dynamic mesh parameters of the dynamic mesh model.

[0066] Specifically, the oil-related parameters in step S42 are the actual density and viscosity values ​​of the oil added to the floating roof oil storage tank; the setting of the unit area is to define the properties of the fluid in the initial state in the fluid domain, for example, to define that the fluid domain below the floating plate is full of oil in the initial state. The setting of the initial conditions refers to determining the initial liquid level. The setting of boundary conditions includes: the setting of the inlet boundary conditions, the setting of the floating plate rising speed, and the setting of the wall boundary conditions. When setting, the velocity inlet, that is, the oil inlet, is used as the inlet boundary condition, and the oil inlet speed is set; the tank bottom, tank wall, and floating plate are set as wall boundary conditions; and the following formula (1) is used as the calculation formula for the floating plate rising speed:

[0067] According to the continuity equation, the volume flow rate of the oil product flowing into the tank inlet is converted into the rising speed of the floating plate. The calculation formula of the rising speed of the floating plate is:

[0068]

[0069] Where: d 1 is the oil inlet of the tank, i.e. the diameter of the velocity inlet, d 2 is the diameter of the floating roof tank, u 1 is the oil inlet speed, u 2 is the rising speed of the floating plate.

[0070] When oil is added, the float rises as the oil level increases. The rising speed is realized by the Profile source file. The Profile source file is:

[0071] ((moving_wall transient 61)

[0072] (time 01.02.03.04.05.0)

[0073] (v_y 0.0047258979 0.0047258979 0.0047258979 0.00472589790.00472589790.0047258979))

[0074] Import the above source files at the corresponding boundary conditions.

[0075] When setting the dynamic mesh parameters of the dynamic mesh model, the layering method is selected, the mesh of the fluid domain is merged and split according to the movement of the floating plate, and the floating plate is set as a rigid body; the dynamic mesh parameters are set as follows: the mesh height is 0.07m, the splitting factor is 0.4, and the merging factor is 0.2.

[0076] In this embodiment, the discrete format of the pressure-velocity coupled PISO algorithm is set as follows: the gradient adopts the least squares unit, the pressure adopts the second-order format, the momentum adopts the second-order upwind format, the turbulent kinetic energy and the turbulent dissipation rate both adopt the first-order upwind format, and the time term discrete format adopts the first-order implicit format.

[0077] S43, in the report definition, two monitoring values ​​of the maximum impact pressure and impact force of the oil flow impacting the floating plate at different times are set.

[0078] S44, setting the sub-relaxation factor and the residual absolute standard value, and determining the time step, the number of time steps and the maximum number of iterations according to the convergence of the discrete method.

[0079] S45, Ansys Fluent software discretizes the fluid domain of the physical model through the finite volume method, obtains the unsteady discrete equations that control the volume of the grid and the internal nodes, and then uses the flow field iteration algorithm to solve the unsteady discrete equations until convergence:

[0080] When the residual values ​​of the variables in the continuity equation, momentum equation, and turbulence equation are reduced to 10 in each time step -3 , and the residual curve is wavy, it is determined to be converged: if converged, complete the simulation calculation, and obtain the pressure distribution, maximum impact pressure and impact force value of the floating plate impacted by the oil flow during the oil collection process of the floating roof oil storage tank; if not, return to step S2 to re-divide the grid to improve the grid quality, or return to step S44 to readjust the sub-relaxation factor until convergence.

[0081] Wherein, the continuity equation is:

[0082] The oil stored in the floating roof tank is an incompressible fluid. Any flow process must satisfy the law of conservation of mass. The continuity equation is:

[0083]

[0084] In the formula, u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 .

[0085] The momentum equation is:

[0086] The flow process of oil in the floating roof tank must satisfy the law of conservation of momentum. The momentum equation is:

[0087]

[0088]

[0089] Where ρ is the oil density, unit: kg·m -3 ; p is the static pressure of the oil, unit is Pa; μ is the dynamic viscosity of the oil, unit is kg·(m·s) -1 ; t is the oil flow time, unit is s; g is the gravity acceleration of the oil, unit is m·s -2 ;u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 .

[0090] The turbulence model selected is the Realizable k-ε model and the standard wall function: turbulence is formed by the superposition of vortices of various scales. The oil flow in the floating roof tank oil collection process is turbulent. The Realizable k-ε model widely used in engineering is used to simulate and solve the turbulence problem. The turbulent kinetic energy transport equation of incompressible fluid is as follows:

[0091]

[0092] The dissipative transport equation for incompressible fluid is as follows:

[0093]

[0094] Where ρ is the oil density, unit: kg·m -3 ; p is the static pressure of the oil, unit is Pa; μ is the dynamic viscosity of the oil, unit is kg·(m·s) -1 ; t is the oil flow time, unit is s; g is the gravity acceleration of the oil, unit is m·s -2 ;u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 ; k is the turbulent kinetic energy, ε is the dissipation rate, μt is the turbulent viscosity, G k represents the turbulent kinetic energy due to the mean velocity gradient, G b represents the turbulent kinetic energy due to buoyancy. For incompressible fluids, G b =0; Y M represents the contribution of pulsating expansion to the overall dissipation rate in compressible flow. For incompressible fluid, Y M =0;σ k and σ ε are the Prandtl numbers corresponding to the turbulent kinetic energy k and the dissipation rate ε, respectively, which can be empirical values; S, S k , S ε is a custom source item; C 1 , C 2 , C 1ε , C 3ε is an empirical constant. When the direction of the shear flow is the same as the direction of gravity, C 3ε =1; when the shear flow is perpendicular to the direction of gravity, C 3ε =0; υ is the kinematic viscosity.

[0095] After completing the corresponding settings in Ansys Fluent software according to steps S42 to S44, Ansys Fluent software will solve the non-steady-state discrete equations by combining the continuity equation, momentum equation and turbulence equation according to the corresponding settings using the set algorithm. In addition, in this embodiment, the pressure distribution, maximum impact pressure and impact force value of the floating plate impacted by the oil flow calculated by Ansys Fluent software are post-processed in CFD-Post software to obtain the pressure distribution diagram of the floating plate and the impact force of the floating plate impacted by the floating plate, analyze the changing law of the pressure of the floating plate impacted by turbulence during the oil collection process in the floating roof oil storage tank, and find the position where the floating plate is easily deformed, that is, the position where the impact pressure of the floating plate impacted by the oil flow is the largest.

[0096] S5, finding the easily deformed position of the floating plate according to the obtained pressure distribution, maximum impact pressure and impact force value of the floating plate impacted by the oil flow, so as to protect the easily deformed position of the floating plate.

[0097] Specifically, the easily deformed position of the floating plate is the position where the maximum impact pressure and impact force are located in the pressure distribution diagram of the floating plate impacted by the oil flow. When protecting the easily deformed position of the floating plate, the direction and flow rate of the oil flow entering the tank body can be changed to reduce the impact of the oil flow on the easily deformed position during the oil collection process, prevent the floating plate from being damaged or deformed during the oil collection process, thereby extending the service life of the floating plate and improving production safety.

[0098] The following is a specific example to illustrate the anti-impact optimization method of the floating plate of the floating roof oil storage tank of the embodiment of the present invention. Specifically, the size of the storage tank is 1000m3 The oil inlet diameter is 0.5m and the gasoline density is 728kg / m 3 , viscosity is 0.0006kg / m·s; the oil inlet flow rate is set to 2.5m / s, and the initial liquid level is 1.8m; the sub-relaxation factors of pressure, density, volume force, turbulent kinetic energy, turbulent dissipation rate and turbulent viscosity are set to 0.3, 1, 1, 0.7, 0.8, 0.8, and 1, respectively, and the absolute standard value of the residual is set to 0.001 for each parameter. The time step is set to 0.1s, the floating plate rises from 1.8m to 2.3m, the time step is set to 1058, and the maximum number of iterations is set to 60.

[0099] The pressure distribution diagram of the floating plate at 2.3 m calculated by the anti-shock optimization method of the floating plate of the floating roof oil storage tank according to the embodiment of the present invention is as follows: Figure 5 As shown, the maximum impact pressure of the oil flow impacting the floating plate when the floating plate rises from 1.8m to 2.3m at different times calculated by the anti-impact optimization method of the floating plate of the floating roof oil storage tank according to the embodiment of the present invention is as follows: Figure 6 As shown, the impact force of the oil flow impacting the floating plate when the floating plate rises from 1.8m to 2.3m at different times calculated by the anti-impact optimization method of the floating plate of the floating roof oil storage tank according to the embodiment of the present invention is as follows: Figure 7 As shown. Figure 5 It can be seen that the pressure is the highest at the edge of the floating plate on the upper side opposite to the oil inlet. From the perspective of protecting the floating plate, it is necessary to strengthen the safety protection of this area. Figure 6 It can be seen that when the oil is first added, the oil product suddenly increases from static to accelerated, and the maximum pressure of the oil flow impacting the floating plate has a sudden increase process. After the oil flow speed stabilizes, with the continuous oil addition, the maximum impact pressure drops, then steadily increases, and then decreases. Figure 7 Impact force change law and Figure 5 similar.

[0100] The present invention discloses an anti-impact optimization method for a floating plate of a floating roof oil storage tank. The mathematical model and solution algorithm in Ansys Fluent software are used to simulate the process of oil flow impacting the floating plate during the oil collection operation of the storage tank. The pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow during the oil collection operation of the floating roof oil storage tank can be obtained. The easily deformed position of the floating plate can be found according to the obtained pressure distribution, maximum impact pressure and impact force, so that the easily deformed position of the floating plate can be protected, thereby optimizing the anti-impact performance of the floating plate and avoiding damage to the floating plate.

[0101] The present invention provides an anti-impact optimization method for a floating plate of a floating roof oil storage tank. The method simulates the process of oil flow impacting the floating plate during the oil collection operation of the storage tank through the mathematical model and solution algorithm in the Ansys Fluent software, so as to obtain the pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow during the oil collection process of the floating roof oil storage tank. Compared with the method of collecting data through experimental tests on the engineering site, the operation process is simpler and safer, and will not affect the operation of the on-site oil tank, and can reduce the cost of data collection. Moreover, the collected data can be displayed in charts through the Ansys Fluent software, which makes it more convenient for on-site engineering personnel to understand the operating status of the floating plate during the oil collection process.

[0102] As a mature professional computational fluid dynamics software, Ansys Fluent has a wealth of calculation models. Users do not need to write formula models by themselves, which lowers the threshold for users. The calculated results are more credible and accurate.

[0103] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for optimizing the anti-impact of a floating plate of a floating roof oil storage tank, characterized in that: The following steps are involved: S1, Geometric modeling of floating roof oil storage tanks: The tank body below the floating plate of the floating roof storage tank is taken as the research object. The Ansys Spacecliam modeling software in the AnsysWorkbench finite element analysis software is used to establish a physical model of the oil flow impacting the floating plate during the three-dimensional oil collection process for the fluid domain and oil inlet wrapped by the floating plate and the tank body below the floating plate. The movement of the floating plate is defined by the dynamic mesh model and program source file in the AnsysFluent computational fluid dynamics software; S2, structured meshing: Ansys Meshing software is used to perform structured meshing on the physical model of oil flow impacting the floating plate in the three-dimensional oil collection process. The mesh at the oil inlet is encrypted by changing the mesh size and adding a boundary layer. S3, if the mesh unit quality is greater than or equal to 0.75, the main mesh aspect ratio is less than or equal to 5, and the mesh aspect ratio in the boundary layer is less than or equal to 100, proceed to step S4, otherwise return to step S2 to adjust the mesh size again; S4, importing the mesh file divided by Ansys Meshing software into Ansys Fluent, using Ansys Fluent software to perform numerical simulation on the impact characteristics of the oil flow impacting the floating plate during the oil collection process of the floating roof oil storage tank, so as to calculate the pressure distribution, maximum impact pressure and impact force value of the floating plate impacted by the oil flow during the oil collection process of the floating roof oil storage tank; S5, finding the easily deformed position of the floating plate according to the obtained pressure distribution, maximum impact pressure and impact force value of the floating plate impacted by the oil flow, so as to protect the easily deformed position of the floating plate.

2. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 1, characterized in that: Step S4 includes the following steps: S41, importing the mesh file divided by Ansys Meshing software into Ansys Fluent and checking the size range of the physical model and the mesh. If the minimum volume of the mesh is a positive value, the size of the physical model is consistent with the size range of the physical model set during modeling, and the boundary condition definition is correct, proceed to step S42; S42, select a transient solver, select the pressure-velocity coupling PISO algorithm as the transient calculation method, set the gravity acceleration value, select a turbulence model, and set the oil product physical property parameters, unit area conditions, initial conditions and boundary conditions, and dynamic mesh parameters of the dynamic mesh model; S43, setting two monitoring values ​​of the maximum impact pressure and impact force of the oil flow impacting the floating plate at different times in the report definition; S44, setting the sub-relaxation factor and the residual absolute standard value, and determining the time step, the number of time steps and the maximum number of iterations according to the convergence of the discrete method; S45, Ansys Fluent software discretizes the fluid domain of the physical model through the finite volume method, obtains the unsteady discrete equations that control the volume of the grid and the internal nodes, and then uses the pressure-velocity coupling PISO algorithm to solve the unsteady discrete equations until convergence: When the residual values ​​of the variables in the continuity equation, momentum equation, and turbulence equation are reduced to 10 in each time step -3 , and the residual curve is wavy, it is determined to be converged: if converged, complete the simulation calculation, and obtain the pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow during the oil collection process of the floating roof oil storage tank; if not, return to step S2 to re-divide the grid to improve the grid quality, or return to step S44 to readjust the sub-relaxation factor until convergence.

3. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 2, characterized in that: The oil product related parameters in step S42 are the actual density and viscosity values ​​of the oil product added to the floating roof oil storage tank; the setting of the initial conditions refers to determining the initial liquid level.

4. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 2, characterized in that: In step S42, the setting of boundary conditions includes: setting of inlet boundary conditions, setting of floating plate rising speed and setting of wall boundary conditions. When setting, the velocity inlet is used as the inlet boundary condition, and the oil inlet speed is set; the tank bottom, tank wall and floating plate are set as wall boundary conditions.

5. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 4, characterized in that: The following formula (1) is used as the calculation formula for the floating plate rising speed: According to the continuity equation, the volume flow rate of the oil product flowing into the tank inlet is converted into the rising speed of the floating plate. The calculation formula is: In the formula: d1 is the oil inlet of the tank, that is, the diameter of the velocity inlet, d2 is the diameter of the floating roof tank, u1 is the oil inlet velocity, and u2 is the floating plate rising velocity.

6. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 5, characterized in that: The continuity equation in step S45 is: The oil stored in the floating roof tank is an incompressible fluid. Any flow process must satisfy the law of conservation of mass. The continuity equation is: In the formula, u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 .

7. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 2, characterized in that: In step S42, a layering method is selected to merge and split the mesh of the fluid domain according to the movement of the floating plate, and the floating plate is set as a rigid body; the dynamic mesh parameters are set as follows: the mesh height is 0.07m, the splitting factor is 0.4, and the merging factor is 0.

2.

8. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 2, characterized in that: The momentum equation in step S45 is: The flow process of oil in the floating roof tank must satisfy the law of conservation of momentum. The momentum equation is: Where ρ is the oil density, unit: kg·m -3 ; p is the static pressure of the oil, unit is Pa; μ is the dynamic viscosity of the oil, unit is kg·(m·s) -1 ; t is the oil flow time, unit is s; g is the gravity acceleration of the oil, unit is m·s -2 ;u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 .

9. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 2, characterized in that: Turbulence is composed of vortices of various scales. The oil flow in the floating roof tank oil collection process is turbulent. The Realizable k-ε model widely used in engineering is used to simulate and solve the turbulent problem. The turbulent kinetic energy transport equation of incompressible fluid is as follows: The dissipative transport equation for incompressible fluid is as follows: Where ρ is the oil density, unit: kg·m -3 ; p is the static pressure of the oil, unit is Pa; μ is the dynamic viscosity of the oil, unit is kg·(m·s) -1 ; t is the oil flow time, unit is s; g is the gravity acceleration of the oil, unit is m·s -2 ;u x 、u y 、u z They are the velocity components of the oil in the x, y and z directions, in m·s -1 ; k is the turbulent kinetic energy, ε is the dissipation rate, μ t is the turbulent viscosity, G k represents the turbulent kinetic energy due to the mean velocity gradient, G b represents the turbulent kinetic energy due to buoyancy. For incompressible fluids, G b =0; Y M represents the contribution of pulsating expansion to the overall dissipation rate in compressible flow. For incompressible fluid, Y M =0;σ k and σ ε are the Prandtl numbers corresponding to the turbulent kinetic energy k and the dissipation rate ε, respectively, which can be empirical values; S, S k , S ε For custom source items; C1, C2, C 1ε , C 3ε is an empirical constant. When the direction of the shear flow is the same as the direction of gravity, C 3ε =1; when the shear flow is perpendicular to the direction of gravity, C 3ε =0; υ is the kinematic viscosity.

10. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 2, characterized in that: In step S42, the discrete format of the pressure-velocity coupling PISO algorithm is set as follows: the gradient adopts the least squares unit, the pressure adopts the second-order format, the momentum adopts the second-order upwind format, the turbulent kinetic energy and the turbulent dissipation rate both adopt the first-order upwind format, and the time term discrete format adopts the first-order implicit format.

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