Calculation method and system for dynamic characteristic coefficient of sliding bearing

Abstract

The invention belongs to the technical field of equipment evaluation, and discloses a sliding bearing dynamic characteristic coefficient calculation method and system, and the method comprises the steps: taking a half of a real oil film model at an axial symmetry plane as a research object, setting the side surfaces, located at the axial symmetry position, of a film and an oil inlet as symmetry planes, computing resources can be remarkably saved, and the computing speed is increased; the thin film and the oil inlet are divided into grids independently, and the outer wall surface of the thin film and the bottom surface of the oil inlet are set as grid interfaces, so that automatic grid division can be realized while the grid quality is ensured; according to the method, small displacement and speed disturbance is applied to the journal at the balance position in Fluent software by means of the UDF, calculation of the dynamic characteristic coefficient of the sliding bearing is achieved, and the calculation precision is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of equipment evaluation and relates to a calculation method and system for a sliding bearing dynamic characteristic coefficient. Background Art

[0002] Dense-phase CO2 refers to a special state of CO2 that occurs when it is above its critical pressure and below its critical temperature. Its high density and low viscosity significantly reduce transportation and storage costs, making it widely used in the CCUS (carbon capture, utilization, and storage) sector. The pump is a core component of dense-phase CO2 transportation, pressurizing the dense-phase CO2 through the rotation of its impeller. Sliding bearings are key components of dense-phase CO2 pumps. They support loads through the dynamic lubricating oil film formed between the journal and the bearing shell, effectively absorbing vibration and shock while reducing friction and wear, thereby improving the pump's operational stability. The dynamic characteristics of the sliding bearing (including stiffness and damping coefficients) significantly affect the rotordynamic performance of the dense-phase CO2 pump, and thus the overall operating efficiency and lifespan of the unit. Accurately and conveniently calculating the dynamic characteristics of the sliding bearing at specific speeds and loads is fundamental to studying the overall performance of dense-phase CO2 pumps and can provide a reference for the development and improvement of dense-phase CO2 pumps. Existing technical solutions can be mainly divided into two types: one is to construct the corresponding control equations and perform numerical calculations with the help of programming languages such as Matlab and Python to obtain the dynamic characteristic coefficients of the sliding bearing. This solution has a high threshold for operation and is relatively difficult, requiring the operator to have a certain level of mathematics and programming skills, and it also requires the introduction of many simplifying assumptions (such as ignoring pressure changes in the oil film thickness direction and ignoring axial heat transfer in the oil film), which affects the calculation accuracy. The other is to use commercial CFD software such as Fluent to calculate the dynamic characteristic coefficients of the sliding bearing; first, this solution uses ICEM software to perform structured meshing on the bearing oil film model. This step requires manual operation and is not conducive to automatic meshing; in addition, this solution uses the journal oil film force monitoring macro and the displacement macro to iteratively solve to determine the stable position of the journal, which has low calculation efficiency; finally, this solution assumes that the viscosity of the lubricating oil is a constant value, ignores the influence of the temperature field on the lubricating oil viscosity, and cannot guarantee the calculation accuracy. Summary of the Invention

[0003] The purpose of the present invention is to solve the problem in the prior art that it is impossible to quickly and accurately obtain the dynamic characteristic coefficient of the sliding bearing under the speed and load to meet the problem of CCUS field for the development and improvement of dense phase CO2 delivery pumps, and to provide a method and system for calculating the dynamic characteristic coefficient of the sliding bearing.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for calculating a dynamic characteristic coefficient of a sliding bearing, comprising:

[0006] Construct an oil film model of a sliding bearing, and take half of the real oil film model at the axial symmetry plane as the research object;

[0007] Import the oil film model into the DesignModeler module of Workbench and set the horizontal offset and vertical offset of the journal as input parameters;

[0008] In the Mesh module of Workbench, define the symmetry surface, inlet, outlet, wall, and interface of the oil film model, and mesh the constructed half oil film model to obtain the bearing oil film mesh file;

[0009] Import the bearing oil film mesh file into Fluent software, set the solution type for the bearing oil film mesh file and the material properties of the lubricating oil and lubricating oil vapor contained in the bearing oil film mesh file in Fluent, and then simulate the relationship between the lubricating oil and lubricating oil vapor;

[0010] The flow characteristics of the lubricating oil are simulated based on the viscosity model. The boundary conditions for the simulation are set. The interface is set as the grid interface. The mass flow difference between the input and output of the viscosity model is monitored. Based on the difference in the mass flow difference, it is determined whether the viscosity model simulation has reached a stable state.

[0011] If a steady state is reached, the multiphase flow simulation in the Fluent software is initialized, and the oil film pressure field is obtained based on the horizontal and vertical offsets of the journal;

[0012] In the CFD Post module of Workbench, based on the oil film pressure field, the relationship between the horizontal and vertical oil film forces on the journal is obtained, and then the equilibrium position of the journal is obtained;

[0013] Small displacement disturbances and small acceleration disturbances are applied to the journal at the equilibrium position through UDF to obtain the stiffness coefficient and damping coefficient of the bearing.

[0014] A further improvement of the present invention is:

[0015] Furthermore, an oil film model of a sliding bearing is constructed, specifically: an oil film model of a sliding bearing is established based on Solidworks software, and half of the oil film model is taken as a research object at the axial symmetry plane. The half oil film model includes a cylindrical film 1 and an oil inlet 2; the oil inlet 2 is arranged on the film 1.

[0016] Furthermore, in the Mesh module of Workbench, the symmetry plane, inlet, outlet, wall and interface of the oil film model are defined. Specifically, the side surfaces of the film 1 and the oil inlet 2 located at the axial symmetry are defined as the symmetry plane, the top surface of the oil inlet 2 is defined as the inlet, the other side surface of the film 1 is defined as the outlet, the inner wall surface of the film 1 is defined as the moving wall surface, the remaining surfaces are defined as the stationary wall surfaces, and the outer wall surface of the film 1 and the bottom surface of the oil inlet 2 are set as the interface surface.

[0017] Furthermore, the solution type for the bearing oil film grid file and the material properties of the lubricating oil and lubricating oil vapor contained in the bearing oil film grid file are set in Fluent, and the relationship between the lubricating oil and lubricating oil vapor is simulated. Specifically, "Steady" is selected as the solution type; N32 lubricating oil is selected, and the lubricating oil viscosity is set through the UDF containing the viscosity-temperature effect; multiphase flow is set, the Mixture model is selected, and the liquid phase material and the corresponding density and viscosity physical quantities are set; as well as the density and specific heat capacity physical quantities corresponding to the gas phase material, the Schnerr-Sauer model in Cavitation is selected for mass transfer, and the vaporization pressure is set to 30,000 Pa; the Laminar model is selected as the viscosity model, and ViscousHeating is selected to consider the viscous heating of the lubricating oil; the operating pressure is set to 0 Pa.

[0018] Furthermore, the flow characteristics of the lubricating oil are simulated based on the viscosity model, and the boundary conditions for the simulation are set. The interface is set as the grid interface, and the mass flow difference between the input and output of the viscosity model is monitored. Based on the difference in the mass flow difference, it is determined whether the viscosity model simulation has reached a stable state. Specifically:

[0019] The boundary conditions are the inlet gauge pressure and temperature, the outlet gauge pressure and the total reflux temperature, the rotational speed of the moving wall, the heat transfer coefficient, and the temperature of the fluid as it flows into the calculation area. The wall thickness is set to 40 mm, the Convection thermal condition is selected, and the other walls are set to static walls. In the thermal condition settings, the wall thickness is set to 15 mm, and the remaining settings are the same as for the moving wall. The calculation area is the area consisting of the inlet, outlet, moving wall, and other static walls.

[0020] For a multiphase flow problem, we selected Coupled as the solution method in the pressure-velocity coupling algorithm. We also set the spatial discretization format, including PRESTO! for the pressure format and First Order Upwind for all other flux formats. We set the number of iterations to 500 and monitored the difference in mass flow rates between the inlet and outlet. When the difference was less than 1%, the iteration was considered converged.

[0021] Furthermore, the multiphase flow simulation in the Fluent software is initialized, and the oil film pressure field is obtained based on the horizontal and vertical offsets of the journal, specifically:

[0022] Select hybrid initialization, configure the steady-state solver based on the set simulation boundary conditions and defined fluid properties, and use the journal horizontal offset and vertical offset as P1 and P2, respectively, as the initial conditions for the simulation. Start the simulation and wait for it to converge to obtain the oil film pressure field.

[0023] Set the horizontal oil film force acting on the journal to F x =force_x()@moving_wall×2, the vertical oil film force is set to F y =force_y()@moving_wall×2, the ratio of the two is set to λ=F x / F y , and F y and λ are set as output quantities, P3 and P4 respectively, where force_x() represents the force component in the x-axis direction; force_y() represents the force component in the y-axis direction; and @moving_wall represents the force acting on the wall moving_wall.

[0024] Furthermore, in the CFDPost module of Workbench, based on the oil film pressure field, the relationship between the horizontal and vertical oil film forces of the journal is obtained, and then the equilibrium position of the journal is obtained. Specifically, the values of P1 and P2 are changed to obtain P3 and P4 corresponding to a series of design points composed of P1 and P2, and a response surface is generated. The optimization target is set to P3 = 5000N, P4 = 0, and the tolerance is 0.001. The candidate design point closest to the optimization target is calculated and selected, which is the equilibrium position of the journal.

[0025] Furthermore, small displacement perturbations and small acceleration perturbations are applied to the journal at the equilibrium position through UDF to obtain the stiffness coefficient and damping coefficient of the bearing, specifically:

[0026] A small displacement disturbance is applied to the journal at the equilibrium position through UDF to calculate the bearing stiffness coefficient. The displacement disturbances ±Δx and ±Δy are taken, and the corresponding relationship between each disturbance and the calculated oil film force is:

[0027]

[0028] The bearing stiffness coefficient is expressed as:

[0029]

[0030] A small velocity disturbance is applied to the journal at the equilibrium position by UDF, and the damping coefficient of the bearing is calculated. The dimensionless velocity disturbances ±Δx′ and ±Δy′ are taken, and the corresponding relationship between each disturbance and the calculated oil film force is:

[0031]

[0032] The bearing damping coefficient is expressed as:

[0033]

[0034] Among them, F x1 Indicates the change in the oil film force in the x direction under the action of displacement disturbance +Δx; F y1 It represents the change of the oil film force in the y direction under the action of displacement disturbance +Δx;

[0035] F x2 Indicates the change in the oil film force in the x direction under the action of the displacement disturbance -Δx; F y2 It represents the change of the oil film force in the y direction under the action of the displacement disturbance -Δx;

[0036] F x3 Indicates the change in the oil film force in the x direction under the action of displacement disturbance +Δy; F y3 It represents the change of oil film force in y direction under the action of displacement disturbance +Δy;

[0037] F x4 F represents the change in the oil film force in the x direction under the action of the displacement disturbance -Δy; y4 It represents the change of oil film force in the y direction under the action of displacement disturbance -Δy;

[0038] k xx It represents the force required to be applied in the x direction when the journal produces unit displacement in the x direction;

[0039] k xy It represents the force required to be applied in the x direction when the journal produces a unit displacement in the y direction;

[0040] k yx It represents the force required to be applied in the y direction when the journal produces a unit displacement in the x direction;

[0041] k yy It represents the force required to be applied in the y direction when the journal produces a unit displacement in the y direction;

[0042] F x5 Indicates the change in oil film force in the x direction under the action of velocity disturbance +Δx'; F y5 It represents the change of oil film force in y direction under the action of velocity disturbance +Δx';

[0043] Fx6 Indicates the change in the oil film force in the x direction under the action of the velocity disturbance -Δx'; F y6 represents the change in the oil film force in the y direction under the action of the velocity disturbance -Δx';

[0044] F x7 Indicates the change in oil film force in the x direction under the action of velocity disturbance +Δy'; F y7 It represents the change of oil film force in y direction under the action of velocity disturbance +Δy';

[0045] F x8 F represents the change in the oil film force in the x direction under the action of the velocity disturbance -Δy'; y8 It represents the change of oil film force in y direction under the action of velocity disturbance -Δy';

[0046] d xx It represents the force required to be applied in the x direction when the journal generates unit velocity in the x direction;

[0047] d xy It represents the force required in the x direction when the journal produces unit velocity in the y direction;

[0048] d yx It represents the force required in the y direction when the journal produces unit speed in the x direction;

[0049] d yy It represents the force required to be applied in the y direction when the journal generates unit velocity in the y direction.

[0050] A calculation system for a sliding bearing dynamic characteristic coefficient comprises:

[0051] A construction module, wherein the construction module constructs an oil film model of the sliding bearing and takes half of the real oil film model at the axial symmetry plane of the oil film model as a research object;

[0052] A parameter setting module, wherein the parameter setting module imports the oil film model into the DesignModeler module of Workbench and sets the horizontal offset and the vertical offset of the journal as input parameters;

[0053] A meshing module, in the Mesh module of the Workbench, defines the symmetry plane, inlet, outlet, wall, and interface of the oil film model, and meshes the constructed half oil film model to obtain a bearing oil film mesh file;

[0054] a property definition module, which imports the bearing oil film mesh file into Fluent software and sets the solution type for the bearing oil film mesh file and the material properties of the lubricating oil and lubricating oil vapor contained in the bearing oil film mesh file in Fluent, thereby simulating the relationship between the lubricating oil and the lubricating oil vapor;

[0055] a judgment module, wherein the judgment module simulates the flow characteristics of the lubricating oil based on the viscosity model, sets boundary conditions during the simulation, sets the interface as a grid interface, monitors the mass flow difference between the input and output of the viscosity model, and judges whether the viscosity model simulation reaches a stable state based on the difference in the mass flow difference;

[0056] An initialization module, wherein if the initialization module reaches a stable state, the multiphase flow simulation in the Fluent software is initialized, and the oil film pressure field is obtained based on the horizontal offset and the vertical offset of the journal;

[0057] A first acquisition module, in the CFD Post module of Workbench, obtains the relationship between the oil film forces in the horizontal and vertical directions of the journal based on the oil film pressure field, thereby obtaining the equilibrium position of the journal;

[0058] The second acquisition module applies a small displacement disturbance and a small acceleration disturbance to the journal at the equilibrium position through UDF to obtain the stiffness coefficient and the damping coefficient of the bearing.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] The present invention takes half of the real oil film model at the axial symmetry plane as the research object, and sets the side surfaces of the film and the oil inlet at the axial symmetry as the symmetry plane, which can significantly save computing resources and speed up the calculation speed; and the film and the oil inlet are separately meshed, and the outer wall surface of the film and the bottom surface of the oil inlet are set as the mesh interface, which can realize automatic mesh division while ensuring the mesh quality; the present invention uses UDF in Fluent software to apply small displacement and velocity disturbances to the journal at the equilibrium position to realize the calculation of the dynamic characteristic coefficient of the sliding bearing, effectively improving the calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0062] Figure 1Schematic diagram of the flow of the method for calculating the dynamic characteristic coefficient of the sliding bearing of the present invention;

[0063] Figure 2 Schematic diagram of the structure of the calculation system of the sliding bearing dynamic characteristic coefficient of the present invention;

[0064] Figure 3 This is the flow chart for solving the dynamic characteristic coefficient of the sliding bearing;

[0065] Figure 4 Schematic diagram of half oil film model;

[0066] Figure 5 Schematic diagram of mesh division of oil film model. DETAILED DESCRIPTION

[0067] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0068] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0069] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0070] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0071] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0072] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0073] The present invention is described in further detail below with reference to the accompanying drawings:

[0074] See also Figure 1 The present invention discloses a method for calculating the dynamic characteristic coefficient of a sliding bearing, comprising:

[0075] S101, constructing an oil film model of a sliding bearing, and taking half of the real oil film model at the axial symmetry plane as a research object;

[0076] Construct an oil film model of a sliding bearing, specifically: establish an oil film model of a sliding bearing based on Solidworks software, take half of the oil film model at the axial symmetry plane as the research object, the half oil film model includes a cylindrical film 1 and an oil inlet 2; the oil inlet 2 is set on the film 1.

[0077] S102, importing the oil film model into the DesignModeler module of Workbench, and setting the journal horizontal offset and vertical offset as input parameters;

[0078] S103, in the Mesh module of Workbench, define the symmetry surface, inlet, outlet, wall, and interface of the oil film model, and mesh the constructed half oil film model to obtain a bearing oil film mesh file;

[0079] The side surface of the film 1 and the oil inlet 2 at the axial symmetry is defined as the symmetry surface, the top surface of the oil inlet 2 is defined as the inlet, the other side surface of the film 1 is defined as the outlet, the inner wall surface of the film 1 is defined as the moving wall surface, the remaining surfaces are defined as the stationary walls, and the outer wall surface of the film 1 and the bottom surface of the oil inlet 2 are defined as the interface

[0080] S104, importing the bearing oil film mesh file into Fluent software, and setting the solution type for the bearing oil film mesh file and the material properties of the lubricating oil and lubricating oil vapor contained in the bearing oil film mesh file in Fluent, thereby simulating the relationship between the lubricating oil and the lubricating oil vapor;

[0081] Select "Steady" as the solution type; select N32 lubricant and set the lubricant viscosity through the UDF including the viscosity-temperature effect; set multiphase flow, select the Mixture model, and set the liquid phase material and the corresponding density and viscosity physical quantities; as well as the density and specific heat capacity physical quantities corresponding to the gas phase material. For mass transfer, select the Schnerr-Sauer model in Cavitation, and set the vaporization pressure to 30,000 Pa; select the Laminar model as the viscosity model, and select ViscousHeating to consider the viscous heating of the lubricant; set the operating pressure to 0 Pa.

[0082] S105, simulating the flow characteristics of the lubricating oil based on the viscosity model, setting boundary conditions for the simulation, setting the interface as a grid interface, and monitoring the mass flow difference between the input and output of the viscosity model. Based on the difference in the mass flow difference, determining whether the viscosity model simulation has reached a stable state;

[0083] The boundary conditions are the inlet gauge pressure and temperature, the outlet gauge pressure and the total reflux temperature, the rotational speed of the moving wall, the heat transfer coefficient, and the temperature of the fluid as it flows into the calculation area. The wall thickness is set to 40 mm, the Convection thermal condition is selected, and the other walls are set to static walls. In the thermal condition settings, the wall thickness is set to 15 mm, and the remaining settings are the same as for the moving wall. The calculation area is the area consisting of the inlet, outlet, moving wall, and other static walls.

[0084] For a multiphase flow problem, we selected Coupled as the solution method in the pressure-velocity coupling algorithm. We also set the spatial discretization format, including PRESTO! for the pressure format and First Order Upwind for all other flux formats. We set the number of iterations to 500 and monitored the difference in mass flow rates between the inlet and outlet. When the difference was less than 1%, the iteration was considered converged.

[0085] S106 , if a stable state is reached, the multiphase flow simulation in the Fluent software is initialized, and the oil film pressure field is obtained based on the horizontal offset and the vertical offset of the journal;

[0086] Select hybrid initialization, configure the steady-state solver based on the set simulation boundary conditions and defined fluid properties, and use the journal horizontal offset and vertical offset as P1 and P2, respectively, as the initial conditions for the simulation. Start the simulation and wait for it to converge to obtain the oil film pressure field.

[0087] Set the horizontal oil film force acting on the journal to F x =force_x()@moving_wall×2, the vertical oil film force is set to F y =force_y()@moving_wall×2, the ratio of the two is set to λ=F x / F y , and F y and λ are set as output quantities, P3 and P4 respectively.

[0088] S107, in the CFD Post module of Workbench, based on the oil film pressure field, obtain the relationship between the horizontal and vertical oil film forces on the journal, and then obtain the equilibrium position of the journal;

[0089] By changing the values of P1 and P2, we can obtain P3 and P4 corresponding to a series of design points composed of P1 and P2, and generate a response surface. The optimization targets are set to P3 = 5000N, P4 = 0, and the tolerances are both 0.001. The candidate design point closest to the optimization target is calculated and selected, which is the equilibrium position of the journal.

[0090] S108 , applying small displacement disturbances and small acceleration disturbances to the journal at the equilibrium position through UDF to obtain the stiffness coefficient and damping coefficient of the bearing.

[0091] A small displacement disturbance is applied to the journal at the equilibrium position through UDF to calculate the bearing stiffness coefficient. The displacement disturbances ±Δx and ±Δy are taken, and the corresponding relationship between each disturbance and the calculated oil film force is:

[0092]

[0093] The bearing stiffness coefficient is expressed as:

[0094]

[0095] A small velocity disturbance is applied to the journal at the equilibrium position by UDF, and the damping coefficient of the bearing is calculated. The dimensionless velocity disturbances ±Δx′ and ±Δy′ are taken, and the corresponding relationship between each disturbance and the calculated oil film force is:

[0096]

[0097] The bearing damping coefficient is expressed as:

[0098]

[0099] Among them, F x1 Indicates the change in the oil film force in the x direction under the action of displacement disturbance +Δx; F y1 It represents the change of the oil film force in the y direction under the action of displacement disturbance +Δx;

[0100] F x2 Indicates the change in the oil film force in the x direction under the action of the displacement disturbance -Δx; F y2 It represents the change of the oil film force in the y direction under the action of the displacement disturbance -Δx;

[0101] F x3 Indicates the change in the oil film force in the x direction under the action of displacement disturbance +Δy; F y3 It represents the change of oil film force in y direction under the action of displacement disturbance +Δy;

[0102] F x4 F represents the change in the oil film force in the x direction under the action of the displacement disturbance -Δy; y4 It represents the change of oil film force in the y direction under the action of displacement disturbance -Δy;

[0103] k xx It represents the force required to be applied in the x direction when the journal produces unit displacement in the x direction;

[0104] k xy It represents the force required to be applied in the x direction when the journal produces a unit displacement in the y direction;

[0105] k yx It represents the force required to be applied in the y direction when the journal produces a unit displacement in the x direction;

[0106] k yy It represents the force required to be applied in the y direction when the journal produces a unit displacement in the y direction;

[0107] F x5 Indicates the change in oil film force in the x direction under the action of velocity disturbance +Δx'; F y5 It represents the change of oil film force in y direction under the action of velocity disturbance +Δx';

[0108] F x6 Indicates the change in the oil film force in the x direction under the action of the velocity disturbance -Δx'; F y6 represents the change in the oil film force in the y direction under the action of the velocity disturbance -Δx';

[0109] F x7 Indicates the change in oil film force in the x direction under the action of velocity disturbance +Δy'; F y7It represents the change of oil film force in y direction under the action of velocity disturbance +Δy';

[0110] F x8 F represents the change in the oil film force in the x direction under the action of the velocity disturbance -Δy'; y8 It represents the change of oil film force in y direction under the action of velocity disturbance -Δy';

[0111] d xx It represents the force required to be applied in the x direction when the journal generates unit velocity in the x direction;

[0112] d xy It represents the force required in the x direction when the journal produces unit velocity in the y direction;

[0113] d yx It represents the force required in the y direction when the journal produces unit speed in the x direction;

[0114] d yy It represents the force required to be applied in the y direction when the journal generates unit velocity in the y direction.

[0115] See also Figure 2 The present invention discloses a calculation system for a sliding bearing dynamic characteristic coefficient, comprising:

[0116] A construction module, wherein the construction module constructs an oil film model of the sliding bearing and takes half of the real oil film model at the axial symmetry plane of the oil film model as a research object;

[0117] A parameter setting module, wherein the parameter setting module imports the oil film model into the DesignModeler module of Workbench and sets the horizontal offset and the vertical offset of the journal as input parameters;

[0118] A meshing module, in the Mesh module of the Workbench, defines the symmetry plane, inlet, outlet, wall, and interface of the oil film model, and meshes the constructed half oil film model to obtain a bearing oil film mesh file;

[0119] a property definition module, which imports the bearing oil film mesh file into Fluent software and sets the solution type for the bearing oil film mesh file and the material properties of the lubricating oil and lubricating oil vapor contained in the bearing oil film mesh file in Fluent, thereby simulating the relationship between the lubricating oil and the lubricating oil vapor;

[0120] a judgment module, wherein the judgment module simulates the flow characteristics of the lubricating oil based on the viscosity model, sets boundary conditions during the simulation, sets the interface as a grid interface, monitors the mass flow difference between the input and output of the viscosity model, and judges whether the viscosity model simulation reaches a stable state based on the difference in the mass flow difference;

[0121] An initialization module, wherein if the initialization module reaches a stable state, the multiphase flow simulation in the Fluent software is initialized, and the oil film pressure field is obtained based on the horizontal offset and the vertical offset of the journal;

[0122] A first acquisition module, in the CFD Post module of Workbench, obtains the relationship between the oil film forces in the horizontal and vertical directions of the journal based on the oil film pressure field, thereby obtaining the equilibrium position of the journal;

[0123] The second acquisition module applies a small displacement disturbance and a small acceleration disturbance to the journal at the equilibrium position through UDF to obtain the stiffness coefficient and the damping coefficient of the bearing.

[0124] Example:

[0125] See also Figure 3 The present invention discloses a method for calculating the dynamic characteristic coefficient of a sliding bearing, comprising:

[0126] Step 1: Use Solidworks software to build the oil film model of the sliding bearing, preferably, Figure 4 As shown in the figure, in order to save computing resources and speed up the calculation, half of the real oil film model is taken as the research object at the axial symmetry plane. The half oil film model consists of two parts, namely the cylindrical film 1 between the journal and the bearing shell and the semi-cylindrical oil inlet 2. The inner diameter of the film 1 is 79.8 mm, the outer diameter is 80 mm, and the width is 50 mm. The diameter of the oil inlet 2 is 4 mm and the height is 5 mm.

[0127] Step 2: Import the oil film model into the DesignModeler module of Workbench, set the horizontal offset and vertical offset of the journal in step 1 as input parameters, P1 and P2 respectively, and set initial values to prepare for response surface optimization. Preferably, the initial value of P1 is set to 0.02 mm and that of P2 is set to 0.03 mm.

[0128] Step 3: In the Mesh module, select and define the symmetry plane, inlet, outlet, wall, and interface of the oil film model. Preferably, the side surface of the film 1 and the oil inlet 2 located at the axial symmetry is defined as the symmetry plane, the top surface of the oil inlet 2 is defined as the inlet, the other side surface of the film 1 is defined as the outlet, the inner wall surface of the film 1 is defined as the moving wall surface, the remaining surfaces are defined as the stationary walls, and the outer wall surface of the film 1 and the bottom surface of the oil inlet 2 are set as the interface surface;

[0129] Step 4: Automatically mesh the half oil film model, preferably, as follows: Figure 5 As shown, the film 1 is divided into 720 equal parts in the circumferential direction, 150 equal parts in the axial direction, and 5 equal parts in thickness. The oil inlet 2 is divided into 12 equal parts in the circumferential direction and radial direction, and 16 equal parts in height.

[0130] Step 5: Select steady-state solution in Fluent;

[0131] Step 6: Set the material properties of the lubricating oil and lubricating oil vapor in Fluent. Preferably, select N32 lubricating oil and set the lubricating oil viscosity through a UDF that includes the viscosity-temperature effect. At the same time, set the gas phase material for the lubricating oil vapor.

[0132] Step 7: Open multiphase flow in Fluent. Preferably, select Mixture model, select liquid phase material for the first phase, select gas phase material for the second phase, select Schnerr-Sauer model in Cavitation for mass transfer, and set the vaporization pressure to 30,000 Pa.

[0133] Step 8: Set the viscosity model in Fluent. Preferably, select the Laminar model and check ViscousHeating to introduce viscous heating of the lubricating oil.

[0134] Step 9: Set the operating pressure in Fluent. Preferably, set the operating pressure to 0Pa.

[0135] Step 10: Set boundary conditions in Fluent. Preferably, set the inlet gauge pressure to 120000Pa, the temperature to 298.15K, the outlet gauge pressure to 101325Pa, the reflux total temperature to 298.15K, the moving wall speed to 2000rpm, the thermal condition to Convection, and the heat transfer coefficient to 50W / (m 2 ·K), the incoming flow temperature is set to 298.15K, the wall thickness is set to 40mm, and other walls are set as static walls. In the settings of thermal conditions, the wall thickness is set to 15mm, and the rest of the settings are the same as those of the moving wall;

[0136] Step 11: Set the grid interface in Fluent. Preferably, set the interface defined in step 3 as the grid interface.

[0137] Step 12: Set the solution method in Fluent. Preferably, select the Coupled format for the pressure-velocity coupling algorithm, PRESTO! for the pressure format in the spatial discretization, and first-order upwind for all other flux formats. Set the number of iterations to 500 and monitor the difference in mass flow rate between the inlet and outlet. When the difference is less than 1%, the iteration is considered converged.

[0138] Step 13: Initialize in Fluent. Preferably, choose hybrid initialization.

[0139] Step 14: Perform the first calculation in Fluent to obtain the oil film pressure field when P1 and P2 are the initial values;

[0140] Step 15: Set the output in the CFD Post module.

[0141] Set the horizontal oil film force acting on the journal to F x =force_x()@moving_wall×2, the vertical oil film force is set to F y =force_y()@moving_wall×2, the ratio of the two is set to λ=F x / F y , and F y and λ are set as output quantities, P3 and P4 respectively;

[0142] Step 16: Use the response surface optimization module to solve the equilibrium position of the journal. Preferably, calculate P3 and P4 corresponding to a series of design points composed of P1 and P2, and generate a response surface. Set the optimization target to P3 = 5000N, P4 = 0, and the tolerance is 0.001. Calculate and select the candidate design point closest to the optimization target, that is, P1 = 0.036155mm, P2 = 0.032725mm, which is the equilibrium position of the journal. At this time, F x0 =-4.33N, F y0 =4991.71N;

[0143] Step 17: Apply a small displacement perturbation to the journal at the equilibrium position through UDF to calculate the bearing stiffness coefficient. Take the displacement perturbations ±Δx and ±Δy. The corresponding relationship between each perturbation and the calculated oil film force is:

[0144]

[0145] The bearing stiffness coefficient can be expressed as:

[0146]

[0147] Preferably, the displacement disturbance Δx=1×10 -3 mm, Δy=1×10 -3 mm, we get:

[0148]

[0149] Step 18: Apply a small velocity perturbation to the journal at the equilibrium position through UDF to calculate the damping coefficient of the bearing. Take the dimensionless velocity perturbations ±Δx′ and ±Δy′. The corresponding relationship between each perturbation and the calculated oil film force is:

[0150]

[0151] The bearing damping coefficient can be expressed as:

[0152]

[0153] Preferably, select transient solution in Fluent and set the time step to 1×10 -5 s, the number of steps is 10, the maximum number of iterations per step is 100, the grid is turned on, and the other settings remain unchanged. Take the velocity perturbations Δx′=0.262mm / s, Δy′=0.262mm / s, and obtain:

[0154]

[0155] Among them, F x1 Indicates the change in the oil film force in the x direction under the action of displacement disturbance +Δx; F y1 It represents the change of the oil film force in the y direction under the action of displacement disturbance +Δx;

[0156] F x2 Indicates the change in the oil film force in the x direction under the action of the displacement disturbance -Δx; F y2 It represents the change of the oil film force in the y direction under the action of the displacement disturbance -Δx;

[0157] F x3 Indicates the change in the oil film force in the x direction under the action of displacement disturbance +Δy; F y3 It represents the change of oil film force in y direction under the action of displacement disturbance +Δy;

[0158] F x4 F represents the change in the oil film force in the x direction under the action of the displacement disturbance -Δy; y4 It represents the change of oil film force in the y direction under the action of displacement disturbance -Δy;

[0159] k xxIt represents the force required to be applied in the x direction when the journal produces unit displacement in the x direction;

[0160] k xy It represents the force required to be applied in the x direction when the journal produces a unit displacement in the y direction;

[0161] k yx It represents the force required to be applied in the y direction when the journal produces a unit displacement in the x direction;

[0162] k yy It represents the force required to be applied in the y direction when the journal produces a unit displacement in the y direction;

[0163] F x5 Indicates the change in oil film force in the x direction under the action of velocity disturbance +Δx'; F y5 It represents the change of oil film force in y direction under the action of velocity disturbance +Δx';

[0164] F x6 Indicates the change in the oil film force in the x direction under the action of the velocity disturbance -Δx'; F y6 represents the change in the oil film force in the y direction under the action of the velocity disturbance -Δx';

[0165] F x7 Indicates the change in oil film force in the x direction under the action of velocity disturbance +Δy'; F y7 It represents the change of oil film force in y direction under the action of velocity disturbance +Δy';

[0166] F x8 F represents the change in the oil film force in the x direction under the action of the velocity disturbance -Δy'; y8 It represents the change of oil film force in y direction under the action of velocity disturbance -Δy';

[0167] d xx It represents the force required to be applied in the x direction when the journal generates unit velocity in the x direction;

[0168] d xy It represents the force required in the x direction when the journal produces unit velocity in the y direction;

[0169] d yx It represents the force required in the y direction when the journal produces unit speed in the x direction;

[0170] d yy It represents the force required to be applied in the y direction when the journal generates unit velocity in the y direction.

[0171] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for calculating the dynamic characteristic coefficient of a sliding bearing, characterized in that: include: Construct an oil film model of a sliding bearing, and take half of the real oil film model at the axial symmetry plane as the research object; Import the oil film model into the DesignModeler module of Workbench and set the horizontal offset and vertical offset of the journal as input parameters; In the Mesh module of Workbench, define the symmetry surface, inlet, outlet, wall, and interface of the oil film model, and mesh the constructed half oil film model to obtain the bearing oil film mesh file; Import the bearing oil film mesh file into Fluent software, set the solution type for the bearing oil film mesh file and the material properties of the lubricating oil and lubricating oil vapor contained in the bearing oil film mesh file in Fluent, and then simulate the relationship between the lubricating oil and lubricating oil vapor; The flow characteristics of the lubricating oil are simulated based on the viscosity model. The boundary conditions for the simulation are set. The interface is set as the grid interface. The mass flow difference between the input and output of the viscosity model is monitored. Based on the difference in the mass flow difference, it is determined whether the viscosity model simulation has reached a stable state. If a steady state is reached, the multiphase flow simulation in the Fluent software is initialized, and the oil film pressure field is obtained based on the horizontal and vertical offsets of the journal; In the CFD Post module of Workbench, based on the oil film pressure field, the relationship between the horizontal and vertical oil film forces on the journal is obtained, and then the equilibrium position of the journal is obtained; Small displacement disturbances and small acceleration disturbances are applied to the journal at the equilibrium position through UDF to obtain the stiffness coefficient and damping coefficient of the bearing.

2. The method for calculating the dynamic characteristic coefficient of a sliding bearing according to claim 1, characterized in that: The oil film model of the sliding bearing is constructed in the following manner: the oil film model of the sliding bearing is established based on Solidworks software, half of the oil film model is taken as a research object at the axial symmetry plane, and the half oil film model includes a cylindrical film (1) and an oil inlet (2); the oil inlet (2) is arranged on the film (1).

3. The method for calculating the dynamic characteristic coefficient of a sliding bearing according to claim 2, wherein: In the Mesh module of the Workbench, the symmetry surface, inlet, outlet, wall surface and interface of the oil film model are defined, specifically: the side surface of the film (1) and the oil inlet (2) located at the axial symmetry is defined as the symmetry surface, the top surface of the oil inlet (2) is defined as the inlet, the other side surface of the film (1) is defined as the outlet, the inner wall surface of the film (1) is defined as the moving wall surface, the remaining surfaces are defined as the stationary wall surfaces, and the outer wall surface of the film (1) and the bottom surface of the oil inlet (2) are set as the interface surface.

4. The method for calculating the dynamic characteristic coefficient of a sliding bearing according to claim 3, wherein: The solution type for the bearing oil film grid file and the material properties of the lubricating oil and lubricating oil vapor contained in the bearing oil film grid file are set in Fluent, thereby simulating the relationship between the lubricating oil and lubricating oil vapor. Specifically, the following steps are: select "Steady" as the solution type; select N32 lubricating oil, and set the lubricating oil viscosity through a UDF containing viscosity-temperature effects; set multiphase flow, select the Mixture model, and set the liquid phase material and the corresponding density and viscosity physical quantities; as well as the density and specific heat capacity physical quantities corresponding to the gas phase material. For mass transfer, select the Schnerr-Sauer model in Cavitation, and set the vaporization pressure to 30,000 Pa; select the Laminar model as the viscosity model, and select Viscous Heating to consider the viscous heating of the lubricating oil; and set the operating pressure to 0 Pa.

5. The method for calculating the dynamic characteristic coefficient of a sliding bearing according to claim 4, characterized in that: The viscosity model is used to simulate the flow characteristics of the lubricating oil, and boundary conditions are set during the simulation. The interface is set as a grid interface, and the mass flow difference between the input and output of the viscosity model is monitored. Based on the difference in the mass flow difference, it is determined whether the viscosity model simulation has reached a stable state. Specifically, The boundary conditions are the inlet gauge pressure and temperature, the outlet gauge pressure and the total reflux temperature, the rotational speed of the moving wall, the heat transfer coefficient, and the temperature of the fluid as it flows into the calculation area. The wall thickness is set to 40 mm, the Convection thermal condition is selected, and the other walls are set to static walls. In the thermal condition settings, the wall thickness is set to 15 mm, and the remaining settings are the same as for the moving wall. The calculation area is the area consisting of the inlet, outlet, moving wall, and other static walls. For a multiphase flow problem, we selected Coupled as the solution method in the pressure-velocity coupling algorithm. We also set the spatial discretization format, including PRESTO! for the pressure format and First Order Upwind for all other flux formats. We set the number of iterations to 500 and monitored the difference in mass flow rates between the inlet and outlet. When the difference was less than 1%, the iteration was considered converged.

6. The method for calculating the dynamic characteristic coefficient of a sliding bearing according to claim 5, characterized in that: The multiphase flow simulation in the Fluent software is initialized, and the oil film pressure field is obtained based on the horizontal and vertical offsets of the journal, specifically: Select hybrid initialization, configure the steady-state solver based on the set simulation boundary conditions and defined fluid properties, and use the journal horizontal offset and vertical offset as P1 and P2, respectively, as the initial conditions for the simulation. Start the simulation and wait for it to converge to obtain the oil film pressure field. Set the horizontal oil film force acting on the journal to F x =force_x()@moving_wall×2, the vertical oil film force is set to F y =force_y()@moving_wall×2, the ratio of the two is set to λ=F x / F y , and F y and λ are set as output quantities, P3 and P4 respectively, where force_x() represents the force component in the x-axis direction; force_y() represents the force component in the y-axis direction; and @moving_wall represents the force acting on the wall moving_wall.

7. The method for calculating the dynamic characteristic coefficient of a sliding bearing according to claim 6, characterized in that: In the CFD Post module of Workbench, the relationship between the oil film forces in the horizontal and vertical directions of the journal is obtained based on the oil film pressure field, and then the equilibrium position of the journal is obtained. Specifically, By changing the values of P1 and P2, we can obtain P3 and P4 corresponding to a series of design points composed of P1 and P2, and generate a response surface. The optimization targets are set to P3 = 5000N, P4 = 0, and the tolerances are both 0.

001. The candidate design point closest to the optimization target is calculated and selected, which is the equilibrium position of the journal.

8. The method for calculating the dynamic characteristic coefficient of a sliding bearing according to claim 7, wherein: The UDF is used to apply small displacement disturbances and small acceleration disturbances to the journal at the equilibrium position to obtain the stiffness coefficient and damping coefficient of the bearing, specifically: A small displacement disturbance is applied to the journal at the equilibrium position through UDF to calculate the bearing stiffness coefficient. The displacement disturbances ±Δx and ±Δy are taken, and the corresponding relationship between each disturbance and the calculated oil film force is: The bearing stiffness coefficient is expressed as: A small velocity disturbance is applied to the journal at the equilibrium position by UDF, and the damping coefficient of the bearing is calculated. The dimensionless velocity disturbances ±Δx′ and ±Δy′ are taken, and the corresponding relationship between each disturbance and the calculated oil film force is: The bearing damping coefficient is expressed as: Among them, F x1 Indicates the change in the oil film force in the x direction under the action of displacement disturbance +Δx; F y1 It represents the change of the oil film force in the y direction under the action of displacement disturbance +Δx; F x2 Indicates the change in the oil film force in the x direction under the action of the displacement disturbance -Δx; F y2 It represents the change of the oil film force in the y direction under the action of the displacement disturbance -Δx; F x3 Indicates the change in the oil film force in the x direction under the action of displacement disturbance +Δy; F y3 It represents the change of oil film force in y direction under the action of displacement disturbance +Δy; F x4 F represents the change in the oil film force in the x direction under the action of the displacement disturbance -Δy; y4 It represents the change of oil film force in the y direction under the action of displacement disturbance -Δy; k xx It represents the force required to be applied in the x direction when the journal produces unit displacement in the x direction; k xy It represents the force required to be applied in the x direction when the journal produces a unit displacement in the y direction; k yx It represents the force required to be applied in the y direction when the journal produces a unit displacement in the x direction; k yy It represents the force required to be applied in the y direction when the journal produces a unit displacement in the y direction; F x5 Indicates the change in oil film force in the x direction under the action of velocity disturbance +Δx'; F y5 It represents the change of oil film force in y direction under the action of velocity disturbance +Δx'; F x6 Indicates the change in the oil film force in the x direction under the action of the velocity disturbance -Δx'; F y6 represents the change in the oil film force in the y direction under the action of the velocity disturbance -Δx'; F x7 Indicates the change in oil film force in the x direction under the action of velocity disturbance +Δy'; F y7 It represents the change of oil film force in y direction under the action of velocity disturbance +Δy'; F x8 F represents the change in the oil film force in the x direction under the action of the velocity disturbance -Δy'; y8 It represents the change of oil film force in y direction under the action of velocity disturbance -Δy'; d xx It represents the force required to be applied in the x direction when the journal generates unit velocity in the x direction; d xy It represents the force required in the x direction when the journal produces unit velocity in the y direction; d yx It represents the force required in the y direction when the journal produces unit speed in the x direction; d yy It represents the force required to be applied in the y direction when the journal generates unit velocity in the y direction.

9. A calculation system for the dynamic characteristic coefficient of a sliding bearing, characterized in that: include: A construction module, wherein the construction module constructs an oil film model of the sliding bearing and takes half of the real oil film model at the axial symmetry plane of the oil film model as a research object; A parameter setting module, wherein the parameter setting module imports the oil film model into the DesignModeler module of Workbench and sets the horizontal offset and the vertical offset of the journal as input parameters; A meshing module, in the Mesh module of the Workbench, defines the symmetry plane, inlet, outlet, wall, and interface of the oil film model, and meshes the constructed half oil film model to obtain a bearing oil film mesh file; a property definition module, which imports the bearing oil film mesh file into Fluent software and sets the solution type for the bearing oil film mesh file and the material properties of the lubricating oil and lubricating oil vapor contained in the bearing oil film mesh file in Fluent, thereby simulating the relationship between the lubricating oil and the lubricating oil vapor; a judgment module, wherein the judgment module simulates the flow characteristics of the lubricating oil based on the viscosity model, sets boundary conditions during the simulation, sets the interface as a grid interface, monitors the mass flow difference between the input and output of the viscosity model, and judges whether the viscosity model simulation reaches a stable state based on the difference in the mass flow difference; An initialization module, wherein if the initialization module reaches a stable state, the multiphase flow simulation in the Fluent software is initialized, and the oil film pressure field is obtained based on the horizontal offset and the vertical offset of the journal; A first acquisition module, in the CFD Post module of Workbench, obtains the relationship between the oil film forces in the horizontal and vertical directions of the journal based on the oil film pressure field, thereby obtaining the equilibrium position of the journal; The second acquisition module applies a small displacement disturbance and a small acceleration disturbance to the journal at the equilibrium position through UDF to obtain the stiffness coefficient and the damping coefficient of the bearing.

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