Bearing cavity oil-gas two-phase flow characteristic simulation and optimization method

Abstract

According to the bearing cavity oil-gas two-phase flow characteristic simulation and optimization method, a bearing cavity fluid domain model is built based on bearing cavity structure design, analysis and improvement, three-dimensional flow field simulation analysis software is adopted, parameters such as bearing cavity fluid domain oil-gas boundary conditions are determined, the bearing cavity oil-gas two-phase flow characteristics are subjected to simulation analysis, and the bearing cavity oil-gas two-phase flow characteristic optimization is achieved. And the three-dimensional flowing condition of oil gas in the bearing cavity can be obtained. By adjusting oil supply, oil return, ventilation, sealing and other structures of the bearing cavity, setting different boundary parameters and the like, the oil-gas two-phase flow characteristics of the bearing cavity are analyzed, evaluation criteria of pressure distribution, flow velocity distribution, volume fraction, oil collection efficiency and oil return efficiency are established, and the oil-gas two-phase flow characteristics can be evaluated. The influence of factors such as structure, rotating speed and cavity pressure on the flow characteristic of the bearing cavity and the internal mechanical mechanism are disclosed, the oil-gas two-phase flow characteristic is optimized, the test cost is reduced, and the calculation efficiency is improved.

Description

Technical Field

[0001] This application belongs to the field of engine design, and specifically relates to a simulation and optimization method for the two-phase flow characteristics of oil and gas in a bearing cavity. Background Technology

[0002] An engine typically contains multiple pivot bearings to support the rotor, stator, and casing. To ensure reliable long-term operation, these bearings require a supply of lubricating and cooling oil, forming a bearing cavity comprised of the rotor, stator, casing, sealing devices, and bearings. This bearing cavity generally includes oil supply paths, oil return paths, ducting air paths, and ventilation paths. Therefore, the bearing cavity contains both lubricating oil and air as working media. Under complex operating conditions such as high speed and high pressure, the flow characteristics of these two working media significantly impact the oil supply and return processes.

[0003] Currently, in engine development, one-dimensional calculation methods are mostly used to simulate and analyze the oil supply and return system of the bearing cavity. This method cannot obtain and understand the two-phase flow characteristics of oil and gas inside the bearing cavity, and their impact on the bearing oil supply and return system. The specific drawbacks are as follows:

[0004] 1. Obtaining data such as oil supply and return flow rates in the bearing cavity through experiments requires iterative processing of test pieces, which is costly and inefficient. Furthermore, the structure and working environment of the bearing cavity are complex, and the oil and gas flow inside the bearing cavity cannot be directly captured.

[0005] 2. Traditional one-dimensional calculation methods for simulating and analyzing the oil supply and return system of bearing cavity can only treat the bearing cavity as a black box. They can only obtain parameters such as the oil supply and return flow rate of the bearing cavity, but cannot obtain and understand the two-phase flow characteristics of oil and gas inside the bearing cavity and its impact on the bearing oil supply and return system, thus reducing the calculation accuracy of the oil supply and return flow rate.

[0006] Therefore, it is urgent to establish a simulation and optimization method for the two-phase flow characteristics of oil and gas in bearing cavities, so as to realize the ability to analyze the two-phase flow characteristics of oil and gas in bearing cavities. Summary of the Invention

[0007] The purpose of this application is to provide a simulation and optimization method for the two-phase flow characteristics of oil and gas in bearing cavities, so as to solve the problem that existing technologies are unable to effectively analyze the flow thermal properties of oil and gas in bearing cavities.

[0008] The technical solution of this application is: a method for simulating and optimizing the two-phase flow characteristics of oil and gas in a bearing cavity, including:

[0009] The oil supply structure, oil return structure, ventilation structure and sealing structure of the bearing cavity are optimized to obtain the optimized bearing cavity structure;

[0010] Perform bearing cavity structure analysis to determine the oil and gas flow characteristics of the oil supply structure, oil return structure, ventilation structure, and sealing structure;

[0011] The bearing cavity fluid domain is constructed based on the oil and gas flow characteristics, and the fluid domain results affecting the oil and gas flow characteristics are calculated in the bearing cavity fluid domain.

[0012] Based on the fluid domain results of oil and gas flow characteristics, the network is divided, and the fluid domain mesh layer and boundary layer of the bearing cavity are defined. Boundary conditions and simulation conditions are set to simulate the two-phase flow characteristics of oil and gas, and the simulation results are output.

[0013] Preferably, when optimizing the oil supply structure, the oil supply hole angle, diameter, oil collection space, and oil collection path of the bearing cavity are optimized.

[0014] When optimizing the oil return structure, optimize the oil return pool space, oil return path, and oil-gas separation structure at the oil return port.

[0015] When optimizing the ventilation structure, the oil-gas separation structure of the ventilation opening should be optimized.

[0016] When optimizing the sealing structure, optimize both contact seals and non-contact seals.

[0017] Preferably, when performing bearing cavity structure analysis, the oil-gas separation structure of the oil return port in the oil return structure and the rotational speed and cavity pressure data in the bearing cavity are used to determine the circumferential flow airflow generated by the rotation of the low-pressure turbine rotor and the airflow disturbance data at the edge of the oil return cavity, thereby determining the oil-gas flow characteristics.

[0018] Preferably, the bearing cavity fluid domain is constructed based on the oil and gas flow characteristics, the geometric configurations of the oil supply structure, oil return structure and ventilation structure are obtained respectively, the fluid flow paths of the oil supply structure, oil return structure and ventilation structure are obtained respectively, the fluid domains of the oil supply structure, oil return structure and ventilation structure are constructed, and the bearing cavity fluid domain is obtained by combining them.

[0019] Preferably, when dividing the network based on the fluid domain results of oil and gas flow characteristics, the multiphase flow, turbulence, wall slip and heat transfer characteristics in the bearing cavity are obtained. The depth of the interaction between lubricating oil-air and solid wall is established through multi-subdomain hybrid grid topology, and the grid density at different positions of the fixed wall is determined.

[0020] Preferably, in setting boundary conditions and simulation conditions, the simulation conditions include a multiphase turbulence model, a viscous model, material parameters, multiphase flow, and boundary parameters; the boundary parameters include inlet boundary conditions, outlet boundary conditions, stationary walls, and moving walls; and the simulation conditions include simulation time and step size.

[0021] Preferably, the oil-gas two-phase flow characteristics are simulated, and the simulation results are output. The simulation results include pressure distribution, velocity distribution, lubricating oil volume distribution, oil recovery efficiency, and oil return efficiency; the design determination is obtained, and it is determined whether the current simulation results meet the design requirements for oil-gas two-phase flow characteristics.

[0022] If not, then determine the components that have a significant impact on the return port of the return structure based on the pressure distribution, flow velocity distribution, lubricating oil volume distribution, oil recovery efficiency, and return efficiency. Then, redesign the oil-gas separation structure of the corresponding components and verify it again until the oil-gas two-phase flow characteristics meet the design requirements.

[0023] The method for simulating and optimizing the two-phase flow characteristics of oil and gas in a bearing cavity disclosed in this application has the following advantages:

[0024] 1. Based on the structural design, analysis and improvement of the bearing cavity, a fluid domain model of the bearing cavity is built. Using three-dimensional flow field simulation analysis software, parameters such as the oil-gas boundary conditions of the fluid domain of the bearing cavity are clarified, and the two-phase flow characteristics of oil and gas in the bearing cavity are simulated and analyzed to obtain the three-dimensional flow of oil and gas inside the bearing cavity.

[0025] 2. By adjusting the bearing cavity's oil supply, return, ventilation, and sealing structures, and setting different boundary parameters, the oil-gas two-phase flow characteristics of the bearing cavity are analyzed. Evaluation criteria for pressure distribution, velocity distribution, volume fraction, oil recovery efficiency, and oil return efficiency are established. This allows for the assessment of oil-gas two-phase flow characteristics, revealing the influence of factors such as structure, rotational speed, and cavity pressure on the bearing cavity flow characteristics and their underlying mechanical mechanisms. This optimizes the oil-gas two-phase flow characteristics, reduces experimental costs, and improves computational efficiency. Attached Figure Description

[0026] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0027] Figure 1 This is a schematic diagram of the overall process of this application;

[0028] Figure 2 This is a schematic diagram of the bearing cavity structure of this application;

[0029] Figure 3 This is a schematic diagram of the fluid network partitioning in this application;

[0030] Figure 4 This is a schematic diagram of the pressure distribution in this application;

[0031] Figure 5 This is a schematic diagram of the flow velocity distribution in this application;

[0032] Figure 6 This is a schematic diagram of the lubricating oil volume fraction in this application;

[0033] Figure 7 This is a volume distribution diagram of the lubricating oil in this application;

[0034] Figure 8 This is the optimized lubricating oil volume distribution diagram of this application. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] A simulation and optimization method for the two-phase flow characteristics of oil and gas in a bearing cavity is proposed. The method uses a flow field simulation software platform and takes the two-phase flow characteristics of oil and gas in the return oil of an intermediate bearing cavity of an engine as an example. The simulation analysis is carried out according to the simulation calculation process.

[0037] like Figure 1 As shown, it includes the following steps:

[0038] In step S100, the oil supply structure, oil return structure, ventilation structure and sealing structure of the bearing cavity are optimized to obtain the optimized bearing cavity structure.

[0039] The bearing cavity structure design of an aero-engine typically includes: a four-point bearing supporting the high-pressure and low-pressure rotors, a five-point bearing supporting the low-pressure rotor and the casing, and related oil supply and return, sealing, and other structures. See [link to bearing cavity structure description] for details. Figure 2 .

[0040] Preferably, when optimizing the oil supply structure, the oil supply hole angle, diameter, oil collection space, and oil collection path of the bearing cavity are optimized.

[0041] When optimizing the oil return structure, optimize the oil return pool space, oil return path, and oil-gas separation structure at the oil return port.

[0042] When optimizing the ventilation structure, the oil-gas separation structure of the ventilation opening should be optimized.

[0043] When optimizing the sealing structure, optimize both contact seals and non-contact seals.

[0044] Step S200: Perform bearing cavity structure analysis to determine the oil and gas flow characteristics of the oil supply structure, oil return structure, ventilation structure, and sealing structure.

[0045] When performing bearing cavity structure analysis, based on the oil-gas separation structure of the oil return port in the oil return structure and the speed and pressure data in the bearing cavity, the circumferential flow airflow generated by the rotation of the low-pressure turbine rotor and the airflow disturbance data at the edge of the oil return cavity are determined, and the oil-gas flow characteristics are determined.

[0046] Step S300: Construct the bearing cavity fluid domain based on the oil and gas flow characteristics, and calculate the fluid domain results that affect the oil and gas flow characteristics within the bearing cavity fluid domain.

[0047] Based on the oil and gas flow characteristics, the bearing cavity fluid domain is constructed. The geometric configurations of the oil supply structure, oil return structure, and ventilation structure are obtained respectively. The fluid flow paths of the oil supply structure, oil return structure, and ventilation structure are obtained respectively. The fluid domains of the oil supply structure, oil return structure, and ventilation structure are constructed and combined to obtain the bearing cavity fluid domain.

[0048] Step S400: Based on the fluid domain results of the oil and gas flow characteristics, divide the network, define the bearing cavity fluid domain mesh layer and boundary layer, refine the mesh at the boundaries and other locations, and fully consider the interaction between lubricating oil-air and solid walls. See [link to fluid mesh generation] for details. Figure 3 .

[0049] Set boundary conditions and simulation conditions, perform simulation of oil-gas two-phase flow characteristics, and output simulation results.

[0050] When dividing the network based on the fluid domain results of oil and gas flow characteristics, the multiphase flow, turbulence, wall slip and heat transfer characteristics in the bearing cavity are obtained. The depth of the interaction between lubricating oil-air and solid wall is established by multi-subdomain hybrid grid topology, and the grid density at different positions of the fixed wall is determined.

[0051] Preferably, in setting boundary conditions and simulation conditions, the simulation conditions include a multiphase turbulence model, a viscous model, material parameters, multiphase flow, and boundary parameters; the boundary parameters include inlet boundary conditions, outlet boundary conditions, stationary walls, and moving walls; and the simulation conditions include simulation time and step size.

[0052] Simulations of oil-gas two-phase flow characteristics are performed, and the simulation results are output, including pressure distribution, velocity distribution, lubricating oil volume distribution, oil recovery efficiency, and oil return efficiency. The design determination is obtained, and it is judged whether the current simulation results meet the design requirements for oil-gas two-phase flow characteristics.

[0053] If not, then determine the components that have a significant impact on the return port of the return structure based on the pressure distribution, flow velocity distribution, lubricating oil volume distribution, oil recovery efficiency, and return efficiency. Then, redesign the oil-gas separation structure of the corresponding components and verify it again until the oil-gas two-phase flow characteristics meet the design requirements.

[0054] Preferably, the simulation conditions are set as follows:

[0055] a) Multiphase turbulence model, select the "Volume of Fluid" model.

[0056] b) Viscous model, select the "k-epsilon" model.

[0057] c) Material parameters: Set parameters such as density and viscosity of lubricating oil and air, as shown in Table 1.

[0058] Table 1 Fluid property parameters

[0059]

[0060] d) Multiphase flow composition, with the first phase being air and the second phase being lubricating oil.

[0061] e) Boundary parameters, as shown in Table 2, include:

[0062] The inlet boundary is configured with parameters such as the inlet boundary pressure of lubricating oil and air, radial velocity, tangential velocity, axial velocity, rotational speed, vector axis direction, and two-phase flow volume ratio.

[0063] Export boundary, setting parameters such as export pressure boundary.

[0064] Stationary wall.

[0065] For the moving wall surface, set parameters such as rotation speed and vector axis direction.

[0066] Other parameters.

[0067] Table 2 Calculation of Boundary Parameters

[0068]

[0069] A new report definition has been added to define the simulation data of interest, such as the total mass of lubricating oil on the wall and body, the inlet mass flow rate of lubricating oil, the outlet mass flow rate of lubricating oil, the total pressure at the ventilation outlet, and the total pressure at the return oil outlet.

[0070] The simulation results are output as follows:

[0071] Analyze the pressure distribution, noting its uniformity and the presence of any unusual variations such as extremely high or low pressures. Assess whether the pressure analysis results meet the requirements. (See...) Figure 4 The oil return chamber is located in a high-pressure zone, while the vent is located in a low-pressure zone. Due to the disturbance of high-pressure and high-speed fluid, local high-pressure zones and local low-pressure zones are formed in the oil return pipe, reducing the cross-sectional area of ​​the oil return and thus affecting the oil return effect.

[0072] Analyze the velocity distribution, noting its uniformity, the presence of extreme high or low velocity, abrupt changes, eddies, or other unusual variations, and whether the velocity analysis results meet the requirements. See [link / reference]. Figure 5Driven by the high-speed rotation of the low-pressure vortex shaft, the fluid inside the cavity flows clockwise, and the radial velocity gradient tends to increase.

[0073] Volume fraction analysis is used to assess the lubricating oil's filling properties, whether it is disturbed by gas, and whether the oil distribution meets requirements. See Figure 6 When the fluid in the cavity flows to the chamfer of the return oil inlet, part of the fluid flows into the return oil pipe. Due to the high flow velocity, the fluid cannot completely fill the return oil port, forming a low-velocity zone on the outer wall of the inner side of the pipe. This affects the flow cross-sectional area in the return oil pipe, forming an area where the lubricating oil is not completely filled. Another part of the fluid flows back into the front oil collecting ring cavity along the wall of the ring cavity, and cannot completely enter the return oil pipe, forming lubricating oil dispersion in the ring cavity.

[0074] Oil recovery efficiency is defined as "oil recovery efficiency = lubricating oil content entering the bearing / (lubricating oil content entering the bearing + lubricating oil content flowing out through seals and other locations)". The higher the oil recovery efficiency, the more sufficient the lubricating oil lubricates and cools the bearing.

[0075] Oil return efficiency is defined as "Oil return efficiency = Lubricating oil flow rate into the return pipe / (Lubricating oil flow rate into the return pipe + Lubricating oil flow rate into the ventilation pipe and other locations)". A higher oil return efficiency indicates more complete oil return and lower oil consumption. The definition is: "Oil return efficiency = Lubricating oil flow rate into the return pipe / (Lubricating oil flow rate into the return pipe + Lubricating oil flow rate into the ventilation pipe and other locations)". See the oil volume distribution diagram (including ventilation openings) for details. Figure 7 Based on the above analysis results, after the lubricating oil disperses in the bearing cavity, part of the lubricating oil flows back into the oil return port, while the other part flows out of the bearing cavity through the vent, ultimately leading to a decrease in the lubricating oil return efficiency.

[0076] After redesigning the oil-gas separation structure of the corresponding component and verifying it again, the lubricating oil volume distribution diagram (including the vent) was obtained. Figure 8 After adding the oil-gas separation structure, the lubricating oil dispersion phenomenon disappears, and the lubricating oil basically flows into the return oil chamber. Therefore, the lubricating oil consumption in the ventilation pipe is reduced, the return oil efficiency is significantly improved, the requirements are met, and the process ends.

[0077] Other parameters.

[0078] In summary, this application has the following advantages:

[0079] 1. Based on the structural design, analysis and improvement of the bearing cavity, a fluid domain model of the bearing cavity is built. Using three-dimensional flow field simulation analysis software, parameters such as the oil-gas boundary conditions of the fluid domain of the bearing cavity are clarified, and the two-phase flow characteristics of oil and gas in the bearing cavity are simulated and analyzed to obtain the three-dimensional flow of oil and gas inside the bearing cavity.

[0080] 2. By adjusting the bearing cavity's oil supply, return, ventilation, and sealing structures, and setting different boundary parameters, the oil-gas two-phase flow characteristics of the bearing cavity are analyzed. Evaluation criteria for pressure distribution, velocity distribution, volume fraction, oil recovery efficiency, and oil return efficiency are established. This allows for the assessment of oil-gas two-phase flow characteristics, revealing the influence of factors such as structure, rotational speed, and cavity pressure on the bearing cavity flow characteristics and their underlying mechanical mechanisms. This optimizes the oil-gas two-phase flow characteristics, reduces experimental costs, and improves computational efficiency.

[0081] Finally, it should be noted that the accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0082] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., 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 simulating and optimizing the two-phase flow characteristics of oil and gas in a bearing cavity, characterized in that, include: The oil supply structure, oil return structure, ventilation structure and sealing structure of the bearing cavity are optimized to obtain the optimized bearing cavity structure; Perform bearing cavity structure analysis to determine the oil and gas flow characteristics of the oil supply structure, oil return structure, ventilation structure, and sealing structure; The bearing cavity fluid domain is constructed based on the oil and gas flow characteristics, and the fluid domain results affecting the oil and gas flow characteristics are calculated in the bearing cavity fluid domain. Based on the fluid domain results of oil and gas flow characteristics, the network is divided, and the fluid domain mesh layer and boundary layer of the bearing cavity are defined. Boundary conditions and simulation conditions are set to simulate the two-phase flow characteristics of oil and gas, and the simulation results are output.

2. The simulation and optimization method for the two-phase flow characteristics of oil and gas in a bearing cavity as described in claim 1, characterized in that, When optimizing the oil supply structure, the oil supply hole angle, diameter, oil collection space, and oil collection path of the bearing cavity should be optimized. When optimizing the oil return structure, optimize the oil return pool space, oil return path, and oil-gas separation structure at the oil return port. When optimizing the ventilation structure, the oil-gas separation structure of the ventilation opening should be optimized. When optimizing the sealing structure, optimize both contact seals and non-contact seals.

3. The simulation and optimization method for the two-phase flow characteristics of oil and gas in a bearing cavity as described in claim 1, characterized in that, When performing bearing cavity structure analysis, based on the oil-gas separation structure of the oil return port in the oil return structure and the speed and pressure data in the bearing cavity, the circumferential flow airflow generated by the rotation of the low-pressure turbine rotor and the airflow disturbance data at the edge of the oil return cavity are determined, and the oil-gas flow characteristics are determined.

4. The simulation and optimization method for the two-phase flow characteristics of oil and gas in a bearing cavity as described in claim 1, characterized in that, Based on the oil and gas flow characteristics, the bearing cavity fluid domain is constructed. The geometric configurations of the oil supply structure, oil return structure, and ventilation structure are obtained respectively. The fluid flow paths of the oil supply structure, oil return structure, and ventilation structure are obtained respectively. The fluid domains of the oil supply structure, oil return structure, and ventilation structure are constructed and combined to obtain the bearing cavity fluid domain.

5. The simulation and optimization method for the two-phase flow characteristics of oil and gas in a bearing cavity as described in claim 1, characterized in that, When dividing the network based on the fluid domain results of oil and gas flow characteristics, the multiphase flow, turbulence, wall slip and heat transfer characteristics in the bearing cavity are obtained. The depth of the interaction between lubricating oil-air and solid wall is established by multi-subdomain hybrid grid topology, and the grid density at different positions of the fixed wall is determined.

6. The simulation and optimization method for the two-phase flow characteristics of oil and gas in a bearing cavity as described in claim 1, characterized in that, In setting boundary conditions and simulation conditions, simulation conditions include multiphase turbulence model, viscous model, material parameters, multiphase flow and boundary parameters; boundary parameters include inlet boundary conditions, outlet boundary conditions, stationary wall and moving wall; simulation conditions include simulation time and step size.

7. The simulation and optimization method for the two-phase flow characteristics of oil and gas in a bearing cavity as described in claim 6, characterized in that, Simulations of oil-gas two-phase flow characteristics are performed, and the simulation results are output, including pressure distribution, velocity distribution, lubricating oil volume distribution, oil recovery efficiency, and oil return efficiency. The design determination is obtained, and it is judged whether the current simulation results meet the design requirements for oil-gas two-phase flow characteristics. If not, then determine the components that have a significant impact on the return port of the return structure based on the pressure distribution, flow velocity distribution, lubricating oil volume distribution, oil recovery efficiency, and return efficiency. Then, redesign the oil-gas separation structure of the corresponding components and verify it again until the oil-gas two-phase flow characteristics meet the design requirements.

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