An anti-impact optimization method for the floating plate of a floating roof oil storage tank

Abstract

The present invention provides an anti-impact optimization method for a floating plate of a floating roof oil storage tank. By adopting the mathematical model and solution algorithm in Ansys Fluent software 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 oil flow impacting the floating plate during the oil collection process can be obtained. Based on the obtained pressure distribution, maximum impact pressure and impact force, the easily deformed position of the floating plate can be found, so that the easily deformed position of the floating plate can be protected, and then the anti-impact performance of the floating plate can be optimized to avoid damage to the floating plate.

Description

Technical Field

[0001] The present 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 depots, refined product transfer depots, and refined product sales depots, playing a crucial role in storing highly volatile fuels such as gasoline, kerosene, diesel, and naphtha. However, when the liquid level in the tank is low during oil delivery and reception operations, turbulence can easily form, impacting the floating plate, causing uneven force on the plate and causing extensive damage. Oil and gas can then diffuse from the damaged plate into the oil and gas space under the tank roof, and then leak into the atmosphere through the vents. This not only wastes resources but also significantly pollutes the environment. Lightning strikes or static electricity induction from thunderclouds can cause fires and explosions, resulting in severe economic losses. Although relatively low speeds and high-stability floating plates are now used for oil delivery and reception operations, floating plate damage and sinking still occur.

[0003] To monitor the operating status of the floating roof tank's float, Chinese utility model patent publication number CN206318276U discloses an improved internal floating roof tank float monitoring device. This device incorporates an observation window over the light-transmitting hole of the internal floating roof tank, allowing the float inside the tank to be monitored through the observation window, facilitating daily monitoring of the internal floating roof's operating status. Chinese utility model patent publication number CN206798261U discloses a fault-detecting internal floating roof. When the internal floating roof sinks, oil compresses the elastic waterproof membrane to extend toward the interior of the first shell, causing the left conductor block to contact the right conductor block, connecting the power supply and buzzer, triggering an alarm. When the internal floating roof is engaged, the liquid level detaches from the float block. The magnetic repulsion of the driver block on the driven slider decreases as it descends, causing the first spring to compress the conductor bar, connecting the left and right contacts, connecting the power supply and buzzer, and triggering an alarm. Chinese invention patent application publication number CN109932020A discloses a floating plate position monitoring system and method for internal floating roof tanks, which can monitor the operating status of the floating plate in real time. Chinese invention patent application publication number CN105236042A discloses an anti-impact safety device for the internal floating roof of a storage tank. The device uses a gas equalization device to ensure uniform exhaust during line sweeping operations, preventing damage to the internal floating roof. The gas venting device on the internal floating roof is normally closed. When the tank is undergoing line sweeping operations, the device automatically opens, separating the inflowing gas carrying the stored liquid and discharging it in an orderly manner, thus preventing flooding and sinking accidents of the floating plate.

[0004] While existing technologies have implemented measures to monitor the operating status of floating platforms, the underlying technical bottlenecks that prevent damage remain unresolved. Determining the impact of oil flow during oil recovery operations on the floating platform—specifically, the magnitude of the impact pressure and force, and the locations where the floating platform is most susceptible to deformation under the impact of oil flow—is crucial for floating platform protection, pollution control, and tank farm 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 based on the obtained pressure distribution, maximum impact pressure and impact force of the floating plate impacted by the oil flow, so as to protect the easily deformed position of the floating plate and avoid 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 anti-impact performance of a floating plate of a floating roof oil storage tank comprises the following steps:

[0008] S1, Floating Roof Oil Storage Tank Geometric Modeling: The tank body below the floating roof tank's float was used as the research object. Ansys Spacecliam modeling software within Ansys Workbench finite element analysis software was used to establish a three-dimensional physical model of the oil flow impacting the floating roof during the oil collection process, including the fluid domain enclosed by the floating roof and the tank body below the floating roof, as well as the oil inlet. The motion of the floating roof was defined by a dynamic mesh model and program source files within Ansys Fluent computational fluid dynamics software.

[0009] S2, structured meshing: Ansys Meshing software was used to perform structured meshing on the physical model of the oil flow impacting the floating plate during the three-dimensional oil recovery process. The mesh at the oil inlet was refined by changing the mesh size and adding boundary layers.

[0010] S3: If the mesh cell 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 and adjust the mesh size again.

[0011] S4, importing the mesh file generated by the Ansys Meshing software into Ansys Fluent, and 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;

[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, thereby protecting the easily deformed position of the floating plate.

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

[0014] S41, importing the mesh file generated by the 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 positive, the size of the physical model is consistent with the size range set during modeling, and the boundary conditions are correctly defined, proceed to step S42;

[0015] 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;

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

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

[0018] In S45, Ansys Fluent software discretizes the fluid domain of the physical model using the finite volume method to obtain the unsteady discrete equations that control the volume and internal nodes of the grid. The pressure-velocity coupled PISO algorithm is then used 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, the -3 , and the residual curve is wavy, it is determined to be converged: if converged, complete the simulation calculation 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; 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-related parameters in step S42 are the actual density and viscosity values ​​of the oil added to the floating roof oil storage tank; and the setting of the initial conditions 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: 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.

[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] Where 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 meshes 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: mesh height is 0.07m, splitting factor is 0.4, and merging factor is 0.2.

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

[0032] The flow process of oil into 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 is 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 gravitational 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 the superposition of vortices of various scales. The oil flow in the floating roof tank oil recovery process is turbulent. The Realizable k-ε model widely used in engineering is used to simulate and solve the turbulent flow problem. The turbulent kinetic energy transport equation of incompressible fluid is as follows:

[0038]

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

[0040]

[0041] Where ρ is the oil density, unit is 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 gravitational 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, 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 shear flow is the same as the direction of gravity, C3ε =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 inverse wind format, the turbulent kinetic energy and the turbulent dissipation rate both adopt the first-order inverse wind 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 method uses a mathematical model and a solution algorithm in Ansys Fluent software to simulate a process in which oil flow impacts the floating plate during an oil collection operation of the storage tank. The method can obtain 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. The method also finds the easily deformed position of the floating plate based on the obtained pressure distribution, maximum impact pressure, and impact force. This method can protect the easily deformed position of the floating plate, thereby optimizing the anti-impact performance of the floating plate and preventing 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 tank through the mathematical model and solution algorithm in 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 operation of the floating roof oil storage tank. Compared with the method of collecting data through on-site engineering experimental tests, the operation process is simpler and safer, and will not affect the operation of the on-site oil tank, which can reduce the cost of data collection. In addition, the collected data can be displayed in charts through Ansys Fluent software, which makes it easier 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 This is a flow chart of a method for optimizing the anti-impact performance of a floating roof storage tank floating plate according to a preferred embodiment of the present invention;

[0047] Figure 2 This is a structural 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 The maximum impact pressure of the oil flow hitting the floating plate at different times when the floating plate rises from 1.8 m to 2.3 m, calculated by the CFD-Post software in step S4;

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

[0053] In the accompanying drawings, 100 is a floating roof oil storage tank; 10 is a tank body; 11 is a tank body portion below the 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 clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts 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 central component. 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 central component. 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 central component. 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 commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

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

[0058] S1. Geometric modeling of floating roof oil storage tanks: The tank body 11 below the floating plate of the floating roof tank is taken as the research object. The floating roof tank can be an external floating roof tank or an internal floating roof tank. The Ansys Spacecliam modeling software in the Ansys Workbench finite element analysis software is used to establish a three-dimensional physical model of the oil flow impacting the floating plate during the oil collection process for the fluid domain and oil inlet enclosed by the floating plate 20 and the tank body 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] During the modeling process, a mock tank was constructed with the same size and shape as the large floating roof tanks currently in operation. Only the impact of turbulence on the floating platform during oil recovery was considered, while other factors, such as the quality and installation of the floating platform, uneven tank floor settlement, equipment corrosion, and the impact of production operations, were ignored. To facilitate the study, the mock tank was simplified as necessary to obtain a final 3D 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 meshing: Ansys Meshing software was used to perform structured meshing on the physical model of the oil flow impacting the floating plate during the three-dimensional oil recovery process. The mesh at the oil inlet was refined by changing the mesh size and adding boundary layers.

[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 and adjust the mesh size again.

[0063] S4, importing the mesh file generated by the Ansys Meshing software into Ansys Fluent, and 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 generated by the Ansys Meshing software into Ansys Fluent and check the size range of the physical model and the mesh. If the minimum volume of the mesh is positive, the size of the physical model is consistent with the size range set during modeling, and the boundary conditions are correctly defined, the inspection result meets the requirements and the process proceeds to step S42. If the inspection result does not meet the requirements, it is necessary to return to the previous steps and adjust the corresponding parameters until the inspection result meets the requirements. For example, the process can return to step S2 to re-mesh the mesh, or return to the modeling step in 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 float is full of oil in the initial state. The setting of the initial conditions refers to determining the initial liquid level. The setting of the 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 float 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: 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.

[0070] When oil is added, the float rises as the oil level rises. The rising speed is realized by the Profile source file, which 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: mesh height is 0.07m, split factor is 0.4, and merge factor is 0.2.

[0076] In this embodiment, 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 inverse wind format, the turbulent kinetic energy and the turbulent dissipation rate both adopt the first-order inverse wind format, and the time term discretization format adopts the first-order implicit format.

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

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

[0079] In S45, Ansys Fluent software discretizes the fluid domain of the physical model using the finite volume method to obtain the unsteady discrete equations that control the volume and internal nodes of the grid. The unsteady discrete equations are then solved using a flow field iterative algorithm 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, the -3 , and the residual curve is wavy, it is determined to be converged: if converged, complete the simulation calculation to 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] Where ux 、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 into 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 is 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 gravitational 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 composed of the superposition of vortices of various scales. The oil flow in the floating roof tank oil recovery 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 dissipation rate transport equation for incompressible fluid is as follows:

[0093]

[0094] Where ρ is the oil density, unit is 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 gravitational 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 tis 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, 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 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 use the configured algorithm to solve the unsteady discrete equations by combining the continuity equation, momentum equation, and turbulence equation according to the corresponding settings. In addition, in this embodiment, the pressure distribution, maximum impact pressure, and impact force values ​​of the floating plate impacted by the oil flow calculated by Ansys Fluent software are post-processed in CFD-Post software to obtain data such as the pressure distribution diagram of the floating plate and the impact force of the floating plate. The changing pattern of the pressure on the floating plate caused by the turbulent impact during the oil collection process in the floating roof oil storage tank is analyzed to find the position of the floating plate that is prone to deformation, that is, the position of the floating plate where the impact pressure due to the oil flow is the greatest.

[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, thereby protecting the easily deformed position of the floating plate.

[0097] Specifically, the easily deformed location of the float plate is the location in the pressure distribution diagram of the float plate subjected to the oil flow impact, where the maximum impact pressure and impact force are located. Protecting this easily deformed location of the float plate can be achieved by changing the direction and velocity of the oil flow entering the tank. This reduces the impact of the oil flow on this easily deformed location during the oil collection process, preventing damage or deformation of the float plate during the oil collection process. This can extend the float plate's service life and improve production safety.

[0098] The following is a specific example to illustrate the anti-impact optimization method of the floating roof oil storage tank float of the embodiment of the present invention. Specifically, the size of the tank is 1000m 3 The oil inlet diameter is 0.5m and the gasoline density is 728kg / m3 , viscosity is 0.0006 kg / m·s; the oil inlet flow rate is set to 2.5 m / s, and the initial liquid level is 1.8 m; 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 each parameter of the residual is set to 0.001. The time step is set to 0.1 s, the floating plate rises from 1.8 m to 2.3 m, 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 2.3m 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 in FIG, 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 in FIG, 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 goes from static to suddenly accelerated, and the maximum pressure of the oil flow impacting the floating plate has a sudden increase. After the oil flow speed stabilizes, as the oil continues to be added, the maximum impact pressure decreases, 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 method uses a mathematical model and a solution algorithm in Ansys Fluent software to simulate a process in which oil flow impacts the floating plate during an oil collection operation of the storage tank. The method can obtain 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. The method also finds the easily deformed position of the floating plate based on the obtained pressure distribution, maximum impact pressure, and impact force. This method can protect the easily deformed position of the floating plate, thereby optimizing the anti-impact performance of the floating plate and preventing 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 tank through the mathematical model and solution algorithm in 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 operation of the floating roof oil storage tank. Compared with the method of collecting data through on-site engineering experimental tests, the operation process is simpler and safer, and will not affect the operation of the on-site oil tank, which can reduce the cost of data collection. In addition, the collected data can be displayed in charts through Ansys Fluent software, which makes it easier 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 rich set of calculation models. Users do not need to write formula models 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 embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications 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 performance of a floating roof oil storage tank, characterized in that: The following steps are involved: S1, Floating Roof Oil Storage Tank Geometric Modeling: The tank body below the floating plate of the floating roof tank was used as the research object. Ansys Spacecliam modeling software within Ansys Workbench finite element analysis software was used to establish a three-dimensional physical model of the oil flow impacting the floating plate during the oil collection process for the fluid domain enclosed by the floating plate and the tank body below the floating plate, as well as the oil inlet. The motion of the floating plate was defined by the dynamic mesh model and program source files within Ansys Fluent computational fluid dynamics software. S2, structured meshing: Ansys Meshing software was used to perform structured meshing on the physical model of the oil flow impacting the floating plate during the three-dimensional oil recovery process. The mesh at the oil inlet was refined by changing the mesh size and adding boundary layers. S3: If the mesh cell 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 and adjust the mesh size again. S4, importing the mesh file generated by the Ansys Meshing software into Ansys Fluent, and using the Ansys Fluent software to perform a numerical simulation of 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; step S4 includes the following steps: S41, importing the mesh file generated by the 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 positive, the size of the physical model is consistent with the size range set during modeling, and the boundary conditions are correctly defined, proceed to step S42; 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; S43, in the report definition, set two monitoring values ​​of the maximum impact pressure and impact force of the oil flow impacting the floating plate at different times; S44, setting the sub-relaxation factor and the absolute standard value of the residual, and determining the time step, the number of time steps and the maximum number of iterations according to the convergence of the discretization method; In S45, Ansys Fluent software discretizes the fluid domain of the physical model using the finite volume method to obtain the unsteady discrete equations that control the volume and internal nodes of the grid. The pressure-velocity coupled PISO algorithm is then used 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, the -3 , and the residual curve is wavy, it is determined to be converged: if converged, complete the simulation calculation 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; 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; 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, thereby protecting 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: The oil-related parameters in step S42 are the actual density and viscosity of the oil added to the floating roof oil storage tank; the setting of the initial conditions refers to determining the initial liquid level.

3. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 1, 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.

4. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 3, 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: Where: 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.

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 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: Where 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 .

6. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 1, characterized in that: In step S42, the 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: mesh height is 0.07m, splitting factor is 0.4, and merging factor is 0.

2.

7. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 1, characterized in that: The momentum equation in step S45 is: The flow process of oil into the floating roof tank must satisfy the law of conservation of momentum. The momentum equation is: Where ρ is the oil density, unit is 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 gravitational 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 .

8. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 1, characterized in that: Turbulence is composed of the superposition of vortices of various scales. The oil flow in the floating roof tank oil recovery process is turbulent. The Realizable k-ε model, widely used in engineering, is used to simulate and solve turbulent flow problems. The turbulent kinetic energy transport equation for incompressible fluids is as follows: The dissipation rate transport equation for incompressible fluid is as follows: Where ρ is the oil density, unit is 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 gravitational 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, 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 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.

9. The anti-impact optimization method for the floating plate of a floating roof oil storage tank according to claim 1, 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 inverse wind format, the turbulent kinetic energy and the turbulent dissipation rate both adopt the first-order inverse wind format, and the time term discretization format adopts the first-order implicit format.

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