A method for analyzing flow-thermal coupling characteristics of a ring-lubricated bearing

Abstract

The application relates to the field of internal flow field analysis of an aero-engine high-speed bearing, and discloses a ring-lubricated bearing flow-heat coupling characteristic analysis method, which can greatly improve the calculation precision of the flow-heat characteristics of the ring-lubricated bearing, realizes accurate prediction of the flow-heat characteristics of the ring-lubricated bearing, and provides important support for fine design of the high-speed bearing of a main shaft of a serviceable and researched advanced aero-engine.

Description

Technical Field

[0001] This invention relates to the field of internal flow field analysis of high-speed bearings in aero-engines, and discloses a method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing. Background Technology

[0002] High-speed bearings are key components supporting the rotor system of aero engines, and the stable high-speed operation of the engine depends on the reliable operation of the main shaft bearings. With the continuous improvement and breakthrough of the engine's extreme performance, the service conditions of the main shaft bearings are becoming increasingly demanding. They must operate under high speed and high load conditions while facing a high-temperature working environment. The heat generated by their own friction and the heat transferred from the external environment increase sharply, which may lead to failure due to overheating.

[0003] With the increasing engine speed, traditional jet lubrication and nozzle lubrication can no longer meet the lubrication and cooling requirements of bearings. Under-ring lubrication has become the most effective technical means to solve the high temperature problem of bearings. However, the oil supply pattern and flow characteristics of under-ring lubrication are significantly different from those of traditional jet lubrication. Currently, traditional analysis models and methods mostly rely on empirical formulas to decouple flow and heat transfer, making it difficult to accurately predict the oil-gas distribution, viscous frictional heat generation, heat transfer characteristics, and temperature distribution of under-ring lubricated bearings. To ensure the reliable operation of aero-engine main shaft bearings under under-ring lubrication conditions, the "heat" problem must be properly addressed. Therefore, a comprehensive and detailed analysis of the internal oil-gas two-phase flow, heat generation, and heat transfer of the bearing is required. Summary of the Invention

[0004] The purpose of this invention is to provide a method for analyzing the flow-thermal coupling characteristics of under-ring lubricated bearings, which can significantly improve the calculation accuracy of the flow-thermal characteristics of under-ring lubricated bearings and achieve accurate prediction of the flow-thermal characteristics of under-ring lubricated bearings.

[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0006] A method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing includes: A geometric model of an under-ring lubricated bearing system is established. The components of the under-ring lubricated bearing system include an inner ring, an outer ring, a cage, rolling elements, a shaft, and a bearing housing. The inner ring of the bearing is provided with multiple oil supply holes, the shaft is provided with oil collection holes, and a circumferential annular groove is provided between the shaft and the inner ring of the bearing. The geometric model is divided into multiple fluid computational domains and multiple solid computational domains. The fluid computational domains and solid computational domains are respectively divided into volume-fitted meshes to obtain the corresponding computational domain meshes. A fluid-thermal coupling numerical simulation was conducted under given initial boundary conditions using a fluid viscous friction heat generation and heat transfer calculation model to obtain the temporal and spatial distribution results of various physical quantities in the fluid and solid computational domains. The physical quantities include oil-gas integral number, velocity, temperature, pressure, turbulent kinetic energy, and turbulent kinetic energy dissipation rate. Based on the temporal and spatial distribution results of various physical quantities obtained from the fluid-thermal coupling numerical simulation, the temperature rise and convective heat transfer coefficient of the bearing are calculated through the physical quantities of the boundary and space.

[0007] Furthermore, based on the structure of the under-ring lubrication bearing system, the geometric model is divided into four types of fluid computational domains: The first type of fluid computational domain includes the oil inlet, oil outlet, circumferential annular groove, and fluid space close to the inner ring of the bearing; The second type of fluid computational domain includes the fluid space close to the cage and rolling elements; The third type of fluid computational domain includes the fluid space close to the outer ring of the bearing; The fourth type of fluid computational domain includes the fluid space extending on both sides of the bearing; In this process, a flow interface is formed between adjacent fluid computational domains, and the flow interface transmits physical parameter information through interpolation.

[0008] Furthermore, based on the structure of the under-ring lubrication bearing system, the geometric model is divided into six types of solid computational domains: The first type of solid computational domain includes the axis body; The second type of solid computational domain includes the bearing housing body; The third type of solid computational domain includes the outer ring body of the bearing; The fourth type of solid computational domain includes the inner ring body of the bearing; The fifth type of solid computational domain includes the cage body; The sixth type of solid computational domain includes the rolling body body; Among them, fluid computing domains or solid computing domains adjacent to various solid computing domains form coupling interfaces, and the coupling interfaces share physical parameter information.

[0009] Furthermore, when performing body-fit mesh generation for the fluid computational domain and the solid computational domain respectively, the mesh nodes of the fluid computational domain and the adjacent solid computational domain correspond one-to-one at the corresponding coupling interface.

[0010] Furthermore, the calculation model for viscous frictional heat generation and heat transfer of flowing fluid includes at least the continuity equation model, momentum equation model, energy equation model, two-phase flow equation model, and turbulence equation model.

[0011] Furthermore, there are rotational speed differences between the fluid computational domains, and a sliding mesh is used to simulate the rotation of the computational domains.

[0012] Furthermore, a distributed heat generation method is used to calculate the heat generated by contact friction between components, and the heat is applied as a volume heat source to the coupling interface formed between adjacent fluid computational domains and solid computational domains.

[0013] Furthermore, when using a fluid viscous frictional heat generation and heat transfer calculation model to conduct fluid-thermal coupling numerical simulations under given initial boundary conditions, the iteration time step of the simulation process is... ;in, This is the diameter of the bearing's inner ring. Where is the diameter of the bearing outer ring. This represents the rotational speed of the bearing's inner ring. The outer ring speed of the bearing is defined as the rotational speed of the inner ring. When the inner and outer rings rotate in the same direction, the outer ring speed is positive; when they rotate in opposite directions, the outer ring speed is negative. The diameter of the rolling element.

[0014] Furthermore, the temperature rise of the bearing is calculated using physical quantities of the boundary and space. ,in For the temperature rise of the ring-lubricated bearing, For the export boundary Temperature of each grid, For the export boundary The speed of each grid For the export boundary The area of ​​each grid, For the export boundary The mixture density of each grid, The number of grid cells at the export boundary. The temperature of the lubricating oil at the inlet of the oil collection hole; Convective heat transfer coefficient at the coupling interface ,in, The total area of ​​the coupling interface. For the first coupling interface Heat flux density of each grid For the first coupling interface The wall temperature of each grid.

[0015] Compared with the prior art, the beneficial effects of this invention are as follows: By establishing a geometric model of the under-ring lubrication bearing system, this invention comprehensively considers the effects of contact friction heat generation, fluid viscous friction heat generation, and external heat transfer. By utilizing the coupling solution of oil-gas two-phase flow with heat generation and heat transfer, it can significantly improve the calculation accuracy of the flow-thermal characteristics of the under-ring lubrication bearing, realize the accurate prediction of the flow-thermal characteristics of the under-ring lubrication bearing, and provide important support for the refined design of high-speed bearings for the main shaft of advanced aero-engines in service and under development. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method for analyzing the flow-thermal coupling characteristics of the under-ring lubricated bearing in the embodiment; Figure 2 This is a schematic diagram of the under-ring lubrication bearing system in the embodiment; Figure 3 This is a schematic diagram of the computational domains and computational grids of the under-ring lubrication bearing system in the embodiment; Among them, 1. shaft; 2. bearing housing; 3. bearing outer ring; 4. bearing inner ring; 5. cage; 6. rolling elements; 7. oil supply hole; 8. oil collection hole; 9. circumferential annular groove; 10. First type of solid computation domain; 20. Second type of solid computation domain; 30. Third type of solid computation domain; 40. Fourth type of solid computation domain; 50. Fifth type of solid computation domain; 60. Sixth type of solid computation domain; 100, Type I fluid computation domain; 200, Type II fluid computation domain; 300, Type III fluid computation domain; 400, Type IV fluid computation domain. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0018] Example 1 See Figures 1 to 3 A method for analyzing the flow-thermal coupling characteristics of annular lubricated bearings, comprising: A geometric model of an under-ring lubricated bearing system is established. The components of the under-ring lubricated bearing system include an inner bearing ring 4, an outer bearing ring 3, a cage 5, rolling elements 6, a rotating shaft 1, and a bearing housing 2. The inner bearing ring 4 is provided with multiple oil supply holes 7, the rotating shaft 1 is provided with oil collection holes 8, and a circumferential annular groove 9 is provided between the rotating shaft 1 and the inner bearing ring 4. The geometric model is divided into multiple fluid computational domains and multiple solid computational domains. The fluid computational domains and solid computational domains are respectively divided into volume-fitted meshes to obtain the corresponding computational domain meshes. A fluid-thermal coupling numerical simulation was conducted under given initial boundary conditions using a fluid viscous friction heat generation and heat transfer calculation model to obtain the temporal and spatial distribution results of various physical quantities in the fluid and solid computational domains. The physical quantities include oil-gas integral number, velocity, temperature, pressure, turbulent kinetic energy, and turbulent kinetic energy dissipation rate. Based on the temporal and spatial distribution results of various physical quantities obtained from the fluid-thermal coupling numerical simulation, the temperature rise and convective heat transfer coefficient of the bearing are calculated through the physical quantities of the boundary and space.

[0019] In this embodiment, by establishing a geometric model of the under-ring lubricated bearing system, the effects of contact friction heat generation, fluid viscous friction heat generation, and external heat transfer are fully considered. By utilizing the coupling solution of oil-gas two-phase flow with heat generation and heat transfer, the calculation accuracy of the under-ring lubricated bearing's flow-thermal characteristics can be significantly improved, enabling accurate prediction of the under-ring lubricated bearing's flow-thermal characteristics. This provides important support for the refined design of high-speed bearings for the main shafts of advanced aero-engines in service and under development.

[0020] Example 2 See Figures 1 to 3 A method for analyzing the flow-thermal coupling characteristics of annular lubricated bearings, comprising: S1. Establish a geometric model of the under-ring lubrication bearing system. The components of the under-ring lubrication bearing system include an inner bearing ring 4, an outer bearing ring 3, a cage 5, rolling elements 6, a rotating shaft 1, and a bearing housing 2. The inner bearing ring 4 is provided with multiple oil supply holes 7, the rotating shaft 1 is provided with oil collection holes 8, and a circumferential annular groove 9 is provided between the rotating shaft 1 and the inner bearing ring 4.

[0021] S2. Divide the geometric model into multiple fluid computational domains and multiple solid computational domains, and perform body-fitting meshing on the fluid computational domains and solid computational domains respectively to obtain the corresponding computational domain meshes; In this embodiment, based on the structure of the under-ring lubrication bearing system, the geometric model is divided into four types of fluid computational domains: The first type of fluid computational domain 100 includes an oil collection hole 8, an oil supply hole 7, a circumferential annular groove 9, and a fluid space close to the inner ring 4 of the bearing. The second type of fluid computing domain 200 includes the fluid space close to the cage 5 and the rolling element 6; The third type of fluid computational domain 300 includes the fluid space close to the outer ring 3 of the bearing; The fourth type of fluid computational domain 400 includes the fluid space extending on both sides of the bearing; In this process, a flow interface is formed between adjacent fluid computational domains, and the flow interface transmits physical parameter information through interpolation.

[0022] The geometric model is divided into six types of solid computational domains: The first type of solid computational domain 10 includes the body of the rotation axis 1; The second type of solid computational domain 20 includes the body of the bearing housing 2; The third type of solid computational domain 30 includes the body of the bearing outer ring 3; The fourth type of solid computational domain 40 includes the body of the bearing inner ring 4; The fifth type of solid computing domain 50 includes the body of the cage 5; The sixth type of solid computational domain 60 contains the body of the rolling element 6; Among them, fluid computing domains or solid computing domains adjacent to various solid computing domains form coupling interfaces, and the coupling interfaces share physical parameter information.

[0023] In this embodiment, when performing body-fitting mesh generation on the fluid computational domain and the solid computational domain respectively, the mesh nodes at the corresponding coupling interface of the fluid computational domain and the adjacent solid computational domain correspond one-to-one, ensuring that the values ​​of the mesh nodes are transmitted accordingly, resulting in smaller calculation errors and better convergence.

[0024] S3. Using a fluid viscous frictional heat generation and heat transfer calculation model, a fluid-thermal coupling numerical simulation is carried out under given initial boundary conditions to obtain the temporal and spatial distribution results of each physical quantity in the fluid calculation domain and the solid calculation domain; the physical quantities include oil-gas integral number, velocity, temperature, pressure, turbulent kinetic energy, and turbulent kinetic energy dissipation rate; The calculation model for viscous frictional heat generation and heat transfer of the flowing fluid in this embodiment includes a continuity equation model, a momentum equation model, an energy equation model, a two-phase flow equation model, and a turbulence equation model, as detailed below:

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] in, The density of the oil-gas mixture, t For time variables, For speed, For relative velocity, Angular velocity of rotation For pressure, For viscous shear stress, It is the acceleration due to gravity. For surface tension, For energy, For total enthalpy, For position vectors, For effective thermal conductivity, For temperature, The density of the lubricating oil, This is the volume fraction of the lubricating oil. For turbulent kinetic energy, The reciprocal of the Prandtl number corresponding to turbulent kinetic energy. For effective viscosity, This is the turbulent kinetic energy production term caused by the average velocity gradient. The turbulent kinetic energy dissipation rate, The reciprocal of the Prandtl number corresponding to the turbulent kinetic energy dissipation rate. and It is a constant, with values ​​of 1.44 and 1.92 respectively.

[0031] In this embodiment, there are rotational speed differences between various fluid computational domains, and a sliding mesh is used to simulate the rotation of the computational domains as boundary conditions; the revolution speeds of the cage 5 and the rolling element 6 are:

[0032] in, The revolution speed, This refers to the diameter of the inner ring 4 of the bearing. The diameter of bearing outer ring 3 is [missing information]. This refers to the rotational speed of bearing inner ring 4. Let the rotational speed of the outer ring 3 of the bearing be the rotational speed. The rotational speed of the inner ring 4 of the bearing is defined as positive. When the inner ring 4 and the outer ring 3 of the bearing rotate in the same direction, the rotational speed of the outer ring 3 is positive. When the inner ring 4 and the outer ring 3 of the bearing rotate in opposite directions, the rotational speed of the outer ring 3 is negative. The diameter of rolling element 6; The rotational speed of rolling element 6 is:

[0033] The real-time coordinates of the origin of rotation of rolling element 6 are:

[0034] in, For the first The initial angular position of each rolling element 6 It is a time variable.

[0035] During the simulation, a distributed heat generation method is used to calculate the heat generated by contact friction between components, and this heat is applied as a volume heat source to the coupling interface formed between adjacent fluid and solid computational domains. The specific calculations are as follows:

[0036] in, For the first Frictional heat generation in the contact area Let be the area of ​​the coupling interface. The thickness of the coupling interface; Iteration time step based on The analysis revealed that it is possible to balance computational cost, convergence effect, and computational accuracy.

[0037] S4. Based on the time and space distribution results of each physical quantity obtained from the fluid-thermal coupling numerical simulation, obtain the distribution of oil-gas integral number, velocity, temperature, pressure and turbulent kinetic energy inside the bearing, and calculate the temperature rise and convective heat transfer coefficient of the bearing through the physical quantities of the boundary and space. In this embodiment, the temperature rise of the under-ring lubricated bearing... The calculation method is as follows:

[0038] in, For the export boundary Temperature of each grid, For the export boundary The speed of each grid For the export boundary The area of ​​each grid, For the export boundary The mixture density of each grid, The number of grid cells at the export boundary. The temperature of the lubricating oil at the inlet of oil collection hole 8.

[0039] The total heat change of the under-ring lubrication bearing system is as follows:

[0040] in, The specific heat capacity of lubricating oil. The specific heat capacity of air. air density, This refers to the mass flow rate of the lubricating oil. The total heat generated by the under-ring lubrication bearing system includes heat generated by contact friction, heat generated by fluid viscous friction, and heat exchange with the external environment. The heat generated by fluid viscous friction can be calculated using the following formula:

[0041] in, Heat is generated by the viscous friction of the fluid. The first obtained from the fluid-thermal coupling simulation results Heat exchange at the outer boundary A positive value indicates that external heating is applied to the ring-lubricated bearing system. A negative value indicates that the under-ring lubrication bearing system dissipates heat to the outside.

[0042] The convective heat transfer coefficient of the coupling interface Calculate according to the following formula:

[0043] in, The total area of ​​the coupling interface. For the first coupling interface Heat flux density of each grid For the first coupling interface The wall temperature of each grid.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing, characterized in that, include: A geometric model of an under-ring lubricated bearing system is established. The components of the under-ring lubricated bearing system include an inner ring, an outer ring, a cage, rolling elements, a shaft, and a bearing housing. The inner ring of the bearing is provided with multiple oil supply holes, the shaft is provided with oil collection holes, and a circumferential annular groove is provided between the shaft and the inner ring of the bearing. The geometric model is divided into multiple fluid computational domains and multiple solid computational domains. The fluid computational domains and solid computational domains are respectively divided into volume-fitted meshes to obtain the corresponding computational domain meshes. A fluid-thermal coupling numerical simulation was conducted under given initial boundary conditions using a fluid viscous friction heat generation and heat transfer calculation model to obtain the temporal and spatial distribution results of various physical quantities in the fluid and solid computational domains. The physical quantities include oil-gas integral number, velocity, temperature, pressure, turbulent kinetic energy, and turbulent kinetic energy dissipation rate. Based on the temporal and spatial distribution results of various physical quantities obtained from the fluid-thermal coupling numerical simulation, the temperature rise and convective heat transfer coefficient of the bearing are calculated through the physical quantities of the boundary and space.

2. The method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing according to claim 1, characterized in that, Based on the structure of the under-ring lubrication bearing system, the geometric model is divided into four types of fluid computational domains: The first type of fluid computational domain includes the oil inlet, oil outlet, circumferential annular groove, and fluid space close to the inner ring of the bearing; The second type of fluid computational domain includes the fluid space close to the cage and rolling elements; The third type of fluid computational domain includes the fluid space close to the outer ring of the bearing; The fourth type of fluid computational domain includes the fluid space extending on both sides of the bearing; In this process, a flow interface is formed between adjacent fluid computational domains, and the flow interface transmits physical parameter information through interpolation.

3. The method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing according to claim 1, characterized in that, Based on the structure of the under-ring lubrication bearing system, the geometric model is divided into six solid computational domains: The first type of solid computational domain includes the axis body; The second type of solid computational domain includes the bearing housing body; The third type of solid computational domain includes the outer ring body of the bearing; The fourth type of solid computational domain includes the inner ring body of the bearing; The fifth type of solid computational domain includes the cage body; The sixth type of solid computational domain includes the rolling body body; Among them, fluid computing domains or solid computing domains adjacent to various solid computing domains form coupling interfaces, and the coupling interfaces share physical parameter information.

4. The method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing according to claim 3, characterized in that, When performing body-fit mesh generation for the fluid computational domain and the solid computational domain respectively, the mesh nodes of the fluid computational domain and the adjacent solid computational domain correspond one-to-one at the corresponding coupling interface.

5. The method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing according to claim 1, characterized in that, The calculation model for heat generation and heat transfer due to viscous friction of flowing fluids includes at least the continuity equation model, momentum equation model, energy equation model, two-phase flow equation model, and turbulence equation model.

6. The method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing according to claim 1, characterized in that, There are rotational speed differences between the fluid computational domains, and a sliding mesh is used to simulate the rotation of the computational domains.

7. The method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing according to claim 1, characterized in that, The distributed heat generation method is used to calculate the heat generated by contact friction between components and it is applied as a volume heat source to the coupling interface formed between adjacent fluid computational domains and solid computational domains.

8. The method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing according to claim 1, characterized in that, When performing fluid-thermal coupling numerical simulations using a fluid viscous friction heat generation and heat transfer calculation model under given initial boundary conditions, the iteration time step of the simulation process is... ;in, This is the diameter of the bearing's inner ring. Where is the diameter of the bearing outer ring. This represents the rotational speed of the bearing's inner ring. The outer ring speed of the bearing is defined as the rotational speed of the inner ring. When the inner and outer rings rotate in the same direction, the outer ring speed is positive; when they rotate in opposite directions, the outer ring speed is negative. The diameter of the rolling element.

9. The method for analyzing the flow-thermal coupling characteristics of an under-ring lubricated bearing according to claim 3, characterized in that, Calculate the bearing temperature rise using physical quantities of the boundary and space. ,in For the temperature rise of the ring-lubricated bearing, For the export boundary Temperature of each grid, For the export boundary The speed of each grid For the export boundary The area of ​​each grid, For the export boundary The mixture density of each grid, The number of grid cells at the export boundary. The temperature of the lubricating oil at the inlet of the oil collection hole; Convective heat transfer coefficient at the coupling interface ,in, The total area of ​​the coupling interface. For the first coupling interface Heat flux density of each grid For the first coupling interface The wall temperature of each grid.

Images