Simulation analysis method for lubrication in sealed bearing cavity based on swing working condition

Abstract

The invention belongs to the technical field of swing bearing sealing, and particularly relates to a simulation analysis method for lubrication in a sealed bearing cavity based on a swing working condition. The invention provides a simulation analysis method for lubrication in a sealed bearing cavity based on swing working conditions, which comprises the following steps of: constructing a calculation model of two-phase flow of lubricating grease and air in a fluid domain of a rolling bearing, analyzing the flow distribution rule of the lubricating grease in the swing process, and carrying out numerical calculation under various swing working conditions; simulation analysis of the lubrication condition in the bearing cavity under the swing condition is achieved, and technical support is provided for improving the sealing performance of an existing rolling bearing. The simulation analysis method specifically comprises the following steps: step 1, analyzing a kinematics relation of the sealed bearing under a swing working condition; 2, the two-phase flow state of lubricating grease and air in a sealed bearing cavity under the swing working condition is set; 3, modeling is conducted on the sealed bearing under the swing working condition, and grids of the sealed bearing are divided; 4, setting boundary conditions; and 5, simulation solution is carried out.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of swing bearing sealing, and particularly relates to a simulation analysis method for lubrication in a sealed bearing cavity based on a swing working condition. BACKGROUND

[0002] The maintenance-free rolling bearing of a pumping unit is a large swing bearing under low speed and heavy load. Since the bearing movement mode is different from that of the existing conventional rotating bearing, the grease distribution characteristics of the swing bearing are significantly different from those of the existing conventional rotating bearing. For example, under swing operation conditions, the bearing elements in the load-carrying area fail prematurely due to the fact that the rolling elements cannot make a full revolution around the bearing raceway, and the bearing elements in the non-load-carrying area cannot play their due roles. In addition, due to the limitation of the swing angle, the lubricating grease in the cavity cannot be uniformly distributed between different rollers, thus causing some rollers to be in a starved lubrication state and aggravating the bearing wear. It should be noted that the swing process of the bearing is a non-steady state process, and the flow and distribution state of the lubricating grease in the bearing cavity are different from and more complex than those under conventional rotating conditions. Moreover, there are complex flow and friction phenomena inside the swing bearing, and the above processes all affect the distribution of the lubricating grease in the bearing. Therefore, analyzing the flow and distribution rules of the lubricating grease inside the swing bearing is the theoretical basis for improving the lubrication technology of the swing bearing.

[0003] At present, the research on the bearing grease distribution rules is mostly completed by means of field tests. For example, in the Chinese patent application CN116256347A, a synchronous online detection method for grease distribution and oil separation is disclosed. In this method, two kinds of fluorescent agents are used to mark the base oil phase and the thickener phase of the lubricating grease respectively, so as to realize the separate tracking and quantitative detection of the two-phase flow of the lubricating grease, and thus simultaneously obtain the distribution and oil separation information of the lubricating grease online. However, the inventors have found in further research that the prior art including the above reference patent document needs to configure different kinds of test conditions for different types and different specifications of bearings under different working conditions, especially for the maintenance-free rolling bearing of a pumping unit, which has a long test cycle and high test cost. Therefore, it is urgent for the technical personnel in the field to further provide a reliable and effective simulation analysis method to optimize the test cycle and test cost of the lubrication in the bearing cavity. SUMMARY

[0004] The present application provides a simulation analysis method for lubrication in a sealed bearing cavity based on a swing working condition. The simulation analysis method analyzes the flow and distribution rules of the lubricating grease in the swing process by constructing a calculation model of the two-phase flow of the lubricating grease and air in the fluid domain of the rolling bearing, and carries out numerical calculation under various swing working conditions, thereby realizing the simulation analysis of the lubrication in the bearing cavity under swing conditions and providing technical support for improving the sealing performance of the existing rolling bearing.

[0005] To solve the above technical problems, the application adopts the following technical solutions: A simulation analysis method for lubrication in a sealed bearing cavity based on a swing working condition, comprising the following steps: Step one: analyzing the kinematic relationship of the sealed bearing in the swing working condition; Step two: setting the two-phase flow state of the lubricating grease and air in the sealed bearing cavity in the swing working condition; Step three: modeling the sealed bearing in the swing working condition and dividing the grid; Step four: setting boundary conditions; Step five: simulation solution.

[0006] More preferably, in the process of analyzing the kinematic relationship of the swing bearing in step one, it specifically comprises: calculating the rotation speed n b of the rolling element around its own axis m ; Wherein, the clockwise rotation direction is positive, then the rotation speed n b of the rolling element around its own axis satisfies: The revolution speed n m of the rolling element satisfies: In the formula, n i is the inner ring speed; n e is the outer ring speed; α i is the inner raceway contact angle; α e is the outer raceway contact angle; the symbol ± in the formula indicates that the inner and outer rings rotate in opposite directions, and the symbol in the formula indicates that the inner and outer rings rotate in the same direction. γ i , γ e and the velocity vector nodal angle β respectively satisfy: In the formula, d m is the bearing nodal diameter; D w is the roller diameter.

[0007] More preferably, in the process of analyzing the kinematic relationship of the swing bearing in step one, it specifically further comprises: determining the mass center motion speed of the rolling element in the swing bearing; Wherein, assuming that the swing speed of the swing bearing is n osc= A cos ωt, then the x direction motion velocity and y direction motion velocity formed by the motion velocity decomposition of the mass center of the rolling body satisfy: In the formula, θ is the initial phase angle of the rolling body.

[0008] More preferably, the step two can be described as follows: The Herschel-Bulkey model is used for the sealing bearing in the swing condition, and the Herschel-Bulkey model satisfies: In the formula, τ is the shear stress; τ0 is the fluid yield stress; k is the consistency coefficient; is the shear strain rate; n is the rheological index; The viscosity μ of the lubricating grease is calculated by initializing the lubricating grease distribution of the sealing bearing in the swing condition in the uniform filling mode, and the viscosity μ satisfies: When , When , In the formula, is the critical shear rate.

[0009] More preferably, in the process of setting the boundary condition in the step four, specifically, the reference pressure of the modeling model is set as the atmospheric pressure, the air model is set as the incompressible gas, and the turbulence model is selected and set as the RNG k-epsilon.

[0010] The application provides a simulation analysis method for lubrication in a sealing bearing cavity based on a swing condition, and the simulation analysis method specifically includes the following steps: Step one: analyzing the kinematics relationship of the sealing bearing in the swing condition; step two: setting the two-phase flow state of the lubricating grease and air in the sealing bearing cavity in the swing condition; step three: modeling the sealing bearing in the swing condition and dividing the grid; step four: setting the boundary condition; and step five: simulation solving. The simulation analysis method for lubrication in the sealing bearing cavity based on the swing condition has the above step characteristics, the calculation model of the two-phase flow of the lubricating grease and air in the rolling bearing fluid domain is constructed, the flow distribution law of the lubricating grease in the swing process is analyzed, the numerical calculation under various swing conditions is carried out, and the simulation analysis of the lubrication in the sealing bearing cavity under the swing condition is realized. Compared with the prior art, at least the following technical advantages are achieved: 1. The simulation analysis process of the lubrication condition in the sealed bearing cavity under the swing working condition is more scientific and fast, and the simulation analysis result is more reliable, which can realize the purpose of providing technical support for the safety production of oil pumping machines. 2. The simulation analysis process of the lubrication condition in the sealed bearing cavity under the swing working condition is universal, and can meet the mass application demand. DETAILED DESCRIPTION

[0011] The drawings are used to provide further understanding of the present application, and constitute a part of the specification, and are used to explain the present application together with embodiments of the present application, and do not constitute a limitation to the present application. In the following drawings: Figure 1 A flowchart of the simulation analysis method of the lubrication in the sealed bearing cavity based on the swing working condition is provided. Figure 2a One of the kinematic relationship diagrams of the sealed bearing (internal component) under the swing working condition. Figure 2b The second kinematic relationship diagram of the sealed bearing (internal component) under the swing working condition. Figure 3 The relationship between the shear stress and the strain rate in the non-Newtonian fluid calculation using the Herschel-Bulkey model. DETAILED DESCRIPTION

[0012] The present application provides a simulation analysis method of the lubrication in the sealed bearing cavity based on the swing working condition, which analyzes the flow distribution law of the lubricating grease in the swing process by constructing a calculation model of the two-phase flow of the lubricating grease and air in the fluid domain of the rolling bearing, and develops numerical calculation under various swing working conditions, so as to realize the simulation analysis of the lubrication condition in the bearing cavity under the swing condition, and provide technical support for improving the sealing performance of the existing rolling bearing. Embodiment one

[0013] The present application provides a simulation analysis method of the lubrication in the sealed bearing cavity based on the swing working condition, as shown in the figure, which includes the following steps: Figure 1

[0014] Step one: analyze the kinematic relationship of the sealed bearing under the swing working condition.

[0015] It is worth noting that for the maintenance-free rolling bearing of the pumping machine, the movement of the sealed bearing will affect the change of the lubricating grease flow field in real time during the swing operation under the swing working condition. For example, the sealed bearing will operate reciprocating swing at a sine wave speed under low speed condition; for the sealed bearing, no relative sliding occurs between the rolling body and the raceway, so the kinematic relationship of the (sealed bearing internal component) can be mainly referred to as the following three kinds: ​The first is the revolution of the rolling body around the inner ring. The revolution of the rolling body will agitate the lubricating grease attached around the rolling body, and a pressure difference is generated in front and back of the rolling body in the movement direction of the rolling body. The second is that the self-rotation movement of the rolling body will affect the distribution state of the lubricating grease. The speed difference between the self-rotation direction of the rolling body and the rotation direction of the inner and outer rings is the power source for forming the oil film. The self-rotation direction of the rolling body is opposite to the rotation direction of the inner ring and same to the rotation direction of the outer ring. The different rotation directions cause the speed difference in the contact area between the rolling body and the inner and outer rings, and the pressure difference of the lubricating grease in the up and down of the movement direction of the rolling body. The third is the rotation of the cage and the inner and outer rings. Under the action of the viscosity and surface tension of the lubricating grease itself, the lubricating grease attached to the surface will move together with the inner and outer rings. At this time, the pocket of the cage will generate shape resistance to the fluid. The kinematics relationship of the sealed bearing in the specific swing operation process can be referred to as shown in Figure 2a 、 Figure 2b Under the joint action of the above three kinds of movements, the lubricating grease generates a complex flow bearing in the sealed bearing cavity.

[0016] Step two: set the two-phase flow state of the lubricating grease and air in the sealed bearing cavity in the swing working condition.

[0017] After completing step one, step two is further implemented. It is worth noting that, as a more preferred embodiment of the present application, the Herschel-Bulkey model is first used for the sealed bearing in the swing working condition, which satisfies: In the formula, τ is the shear stress, τ0 is the yield stress of the fluid, k is the consistency coefficient, γ is the shear strain rate, and n is the rheological index.

[0018] It is necessary to supplement here that, for the two-phase flow state of the lubricating grease and air in the sealed bearing cavity in the swing working condition, the lubricating grease belongs to a non-Newtonian fluid. Therefore, in the finite element numerical theory, the Herschel-Bulkey model is used to simulate and calculate the non-Newtonian fluid to obtain the viscosity μ of the lubricating grease, which should satisfy: However, it should be noted that, for the calculation of the non-Newtonian fluid using the Herschel-Bulkey model, when the strain rate approaches 0, the calculated viscosity becomes infinite, which will lead to the divergence of the N-S equation in the calculation. Therefore, in order to accurately reflect the flow state of the lubricating grease, the critical shear rate is further introduced, so as to approximately process the calculation of the non-Newtonian fluid using the Herschel-Bulkey model. For details, refer to Figure 3 .

[0019] Specifically, Figure 3 ​The relationship between shear stress and strain rate in non-Newtonian fluid calculation using Herschel-Bulkey model is shown. The uniform filling method is used to initialize the lubricating grease distribution of the sealing bearing in the swing condition, and the viscosity μ of the lubricating grease is calculated to satisfy: When , When , In the formula, is the critical shear rate.

[0020] Step three: modeling the sealing bearing in the swing condition and dividing the grid.

[0021] After completing step two, step three is further implemented. It should be noted that according to the requirements of the actual simulation analysis process, in order to further improve the solving accuracy and efficiency, the technical personnel can also make the following reasonable assumptions and simplifications in the modeling process: For example: (1) appropriately increase the bearing clearance and ignore the effect of the retainer to reduce the number of grids generated by grid division and improve the solving efficiency; (2) assume that the sealing bearing of the beam pumping unit operates at very low speed, and the influence of the temperature rise of the sealing bearing is not considered; (3) the sealing ring and the inner raceway of the sealing bearing are interference fit, and the influence of leakage on the flow field can be ignored, and the sealing end cover is set to a closed state in modeling; (4) the sealing bearing is completed with grease injection, grease uniformization and sealing end cover installation before leaving the factory.

[0022] On the basis of the above assumptions and simplifications, according to the basic parameters of the sealing bearing, the conventional modeling software (such as SOLID WORKS three-dimensional modeling software) is used to model the sealing bearing in the swing condition, and the grid division process is realized by importing FLUENT. Due to the limitation of dynamic grid boundary conditions, all unstructured grids are used for division. Different local encryption conditions produce different grid numbers, in order to improve the calculation efficiency, the inner and outer raceway grid local encryption can be selected, which can reduce about 30% of the calculation amount.

[0023] Step four: setting boundary conditions.

[0024] After completing step three, step four is further implemented. As a more preferred embodiment of the present application, in the process of setting boundary conditions in this step four, it specifically includes: setting the reference pressure of the modeling model to atmospheric pressure, setting the air model to incompressible gas, and selecting the turbulence model to RNG k-epsilon.

[0025] It is worth noting that the application studies the change process of the flow field of the grease mixed with air in the oscillation process of the sealed bearing, and the required solution result is the result of instantaneous change. Therefore, the skilled in the art can further obtain the calculation result according to the calculation analysis, drive the roller wall movement by using the udf programming, the outer ring and the sealing ring are the no-slip moving wall, and the inner ring is the static wall; and the dynamic mesh division method is used for the whole movement area, that is, the mesh is re-divided every time step, so that the dynamic calculation result is simulated.

[0026] Step five: simulation solution.

[0027] After completing step four, step five is further implemented. The simulation solution process of step five can realize the numerical solution process by using the COUPLE algorithm of the second-order implicit transient format, and the pressure discrete format can refer to the Modi fied BodyForce Wei ghted. According to the set grid size and the oscillation speed, the calculation step and the number of steps are defined to complete the whole process of numerical simulation solution. Embodiment two

[0028] Embodiment two contains all the technical features of embodiment one. Embodiment two further explains the kinematic relationship of the sealed bearing in step one of analyzing the oscillation working condition as follows: Specifically, referring to the kinematic relationship of the sealed bearing shown in Figure 2a , Figure 2b , the self-rotation speed n b of the rolling body around its own axis and the revolution speed n m of the rolling body can be calculated.

[0029] Wherein, the clockwise rotation direction is defined as positive, then the self-rotation speed n b of the rolling body around its own axis satisfies: The revolution speed n m of the rolling body satisfies:

[0030] In the formula, n i is the inner ring speed; n e is the outer ring speed; α i is the inner raceway contact angle; α e is the outer raceway contact angle; the symbol ± indicates that the inner and outer ring rotation directions are opposite, and the symbol indicates that the inner and outer ring rotation directions are the same.

[0031] And γ i , γ eand the velocity vector pitch angle β, respectively, satisfy the following formula: In the formula, d m is the bearing pitch diameter; D w is the roller diameter. Example Three

[0032] Example Three contains all the technical features of Example One. Example Three further explains and describes the kinematics of the sealed bearing in the swing condition in Step One, which is not mentioned in Example Two: As a more preferred embodiment of the present application, the rolling element of the sealed bearing in the swing condition will undergo reciprocating motion, and for the sealed bearing in the swing condition, we cannot directly define the rolling element's orbital velocity using the cylindrical coordinates. Therefore, we choose to decompose the center-of-mass motion velocity of the rolling element, and determine the center-of-mass motion velocity of the rolling element in the swing bearing by means of the x-direction motion velocity and the y-direction motion velocity formed by the decomposition.

[0033] Specifically, let the swing speed of the swing bearing be n osc = A cos ωt, then the x-direction motion velocity and the y-direction motion velocity formed by the decomposition of the center-of-mass motion velocity of the rolling element satisfy: In the formula, θ is the initial phase angle of the rolling element.

[0034] The present application provides a simulation analysis method for lubrication in the sealed bearing cavity based on the swing condition, which specifically includes the following steps: Step One: analyze the kinematics of the sealed bearing in the swing condition; Step Two: set the two-phase flow state of the lubricating grease and air in the sealed bearing cavity in the swing condition; Step Three: model the sealed bearing in the swing condition and divide the grid; Step Four: set the boundary conditions; Step Five: simulate and solve. The simulation analysis method for lubrication in the sealed bearing cavity based on the swing condition with the above step characteristics, by constructing a calculation model of the two-phase flow of the lubricating grease and air in the rolling bearing fluid domain, analyzing the flow distribution law of the lubricating grease in the swing process, and carrying out numerical calculation under various swing conditions, realizes the simulation analysis of the lubrication in the sealed bearing cavity under the swing condition. Compared with the prior art, it at least has the following technical advantages: 1. The simulation analysis process of the lubrication condition in the sealed bearing cavity under the swing working condition is more scientific and fast, and the simulation analysis result is more reliable, so as to realize the purpose of providing technical support for the safety production of oil pumping machines. 2. The simulation analysis process of the lubrication condition in the sealed bearing cavity under the swing working condition is strong in universality, and can meet the mass application demand.

[0035] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A simulation analysis method for lubrication within the cavity of a sealed bearing based on oscillating operating conditions, characterized in that, The steps include the following: Step 1: Analyze the kinematic relationship of the sealed bearing under oscillating conditions; Step 2: Set the two-phase flow state of grease and air in the sealed bearing cavity under oscillating conditions; Step 3: Model the sealed bearing under oscillating conditions and mesh it; Step 4: Set boundary conditions; Step 5: Simulation solution.

2. The simulation analysis method for lubrication in the cavity of a sealed bearing based on oscillating conditions according to claim 1, characterized in that, The process of analyzing the kinematic relationship of the oscillating bearing in step one specifically includes: calculating the rotational speed n of the rolling elements in the oscillating bearing about their own axis. b and the revolution speed n of the rolling element m ; Where clockwise rotation is defined as positive, the rotational speed n of the rolling element about its own axis is... b ,satisfy: The revolution speed n of the rolling element m ,satisfy: In the formula, n i n is the inner ring rotation speed; e α is the outer ring speed; i α is the contact angle of the inner raceway. e This refers to the outer raceway contact angle; the ± sign in the symbol indicates that the inner and outer races rotate in opposite directions. The symbol indicates that the inner and outer rings turn in the same direction; γ i γ e And the velocity vector node fillet β, respectively satisfying: In the formula, d m D is the bearing pitch circle diameter; w The diameter is the roller diameter.

3. The simulation analysis method for lubrication in the cavity of a sealed bearing based on oscillating conditions according to claim 1, characterized in that, In the process of analyzing the kinematic relationship of the oscillating bearing in step one, the following is also included: determining the velocity of the center of mass of the rolling elements in the oscillating bearing; Let the oscillation speed of the oscillating bearing be n. osc =Acosωt, then the x-direction velocity and y-direction velocity formed by the decomposition of the center of mass motion of the rolling element satisfy the following respectively: In the formula, θ is the initial phase angle of the rolling element.

4. The simulation analysis method for lubrication in the cavity of a sealed bearing based on oscillating conditions according to claim 1, characterized in that, Step two can be specifically described as follows: For sealed bearings operating under oscillating conditions, the Herschel-Bulkey model is used. This Herschel-Bulkey model satisfies the following: In the formula, τ is the shear stress; τ0 is the fluid yield stress; and k is the consistency coefficient. n is the shear strain rate; n is the rheological index. The grease distribution of the sealed bearing under oscillating conditions is initialized using a uniform filling method. The viscosity μ of the grease is calculated to satisfy: when hour, when hour, In the formula, This is the critical shear rate.

5. The simulation analysis method for lubrication in the cavity of a sealed bearing based on oscillating conditions according to claim 1, characterized in that, The process of setting boundary conditions in step four specifically includes: setting the reference pressure of the modeling model to atmospheric pressure, setting the air model to an incompressible gas, and selecting the turbulence model as RNG k-epsilon.

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