Collaborative simulation method for dynamic pressure type oil-gas separator and lubricating oil tank

Abstract

The invention belongs to the technical field of simulation, and particularly relates to a co-simulation method for a dynamic pressure type oil-gas separator and a lubricating oil tank. Comprising the following steps: establishing an integral three-dimensional geometric model of a lubricating oil tank and an oil-gas separator, and establishing a conode monitoring surface at the joint of the oil-gas separator and the lubricating oil tank; discretizing the continuous geometric model into a finite number of computational grids; obtaining a discretized coupling calculation domain of the lubricating oil tank and the oil-gas separator; establishing a control equation set of simulation calculation, and calculating a physical quantity in each discrete grid; collecting flow parameters and physical property parameters, and inputting the flow parameters and the physical property parameters into a control equation set to obtain field data of an oil-gas distribution field, a pressure field and a velocity field; post-processing software is introduced, and time-average speed distribution of all positions in the lubricating oil tank and the oil-gas separator and the mass flow of inlet and outlet lubricating oil and air are obtained; mass flow monitoring data of the lubricating oil and the air are imported into post-processing software, the separation efficiency of the oil-gas separator body and the overall oil-gas separation efficiency of the lubricating oil tank can be calculated, and simulation is completed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of simulation, and particularly relates to a dynamic pressure type oil-gas separator and oil tank cooperative simulation method. BACKGROUND

[0002] An aero-engine is a kind of rotor power machinery, and a large amount of air will be mixed into the oil when it rotates at a high speed, which puts forward a rigorous requirement on the oil-gas separation capacity of the lubricating system. The dynamic pressure type oil-gas separator (hereinafter referred to as the oil-gas separator) has the characteristics of simple structure, large processing capacity and high separation efficiency, and has been widely applied to new aero-engines.

[0003] The most important performance index of the oil-gas separator is the separation efficiency, which is calculated by measuring the volume ratio of the oil and air discharged from the oil tank in the test. This method actually measures the separation efficiency of the whole oil tank, rather than the efficiency of the oil-gas separator itself, which is the limitation of the test method. This will lead to the fact that the oil-gas separator cannot be decoupled from the oil tank when evaluating the performance of the oil-gas separator, that is, when the same kind of separator is matched with different structures of the oil tank, a test analysis needs to be re-performed, which increases the time and economic cost. With the development of CFD technology, the separation efficiency of the oil-gas separator itself can be more accurately measured through numerical simulation. To realize the numerical simulation of the oil-gas separation process, a suitable multiphase flow model needs to be selected.

[0004] The researchers of China Flight Test Establishment, such as Ren Qi, use the RSM model to study the internal flow field characteristics and separation mechanism of the dynamic pressure type oil-gas separator, and propose to calculate the separation efficiency of the separator by measuring the oil-gas ratio of the oil outlet and the inlet according to the principle of the volume method. However, it can be known from the calculation results (as shown in Figure 1 , although the counter-flow area is formed in the separator, that is, the side wall velocity gradient is positive and the center velocity gradient is negative, but there is no obvious air column formed in the center part, which shows that the model can predict that the oil-gas separation process cannot be effectively calculated.

[0005] In the existing research, the VOF model is used to simulate the internal flow field and the development process of the oil-gas separation interface of the oil-gas separator, and the structure size of the separator is optimized according to the calculation results. The model can calculate the oil-gas separation interface that generally conforms to the physical law, but the adaptability of the model to different working conditions is poor: under the conditions of low inlet oil-gas ratio and inlet flow rate, no obvious spiral upward center airflow is formed; when the oil-gas ratio or flow rate is increased, the airflow path will be excessively extended to the bottom outlet, and these two situations will cause the reduction of the separation efficiency. At the same time, the model will unreasonably form local large bubbles when capturing the oil-gas separation interface, as shown in Figure 2The left figure shows the inlet gas ratio of 5:5 and the flow rate of 30 L / min, and the right figure shows the inlet gas ratio of 3:7 and the flow rate of 50 L / min, which indicates that the model needs to be improved for calculating the high cyclone motion in the oil-gas separator.

[0006] The oil-gas separator relies on strong cyclone to complete oil-gas separation, and the flow pattern of the oil-gas mixture is very complex. The multiphase flow model can predict the flow rule of the gas-liquid two-phase flow, but different kinds of models have their own applicability, and the calculation accuracy of the existing CFD simulation model in the oil-gas distribution and the velocity field, the pressure field and other parameters needs to be improved. In addition to achieving the above goals, the new model should also be able to realize the coupling simulation of the separator and the oil tank, and be able to independently calculate the separation efficiency of the separator and the oil tank. The specific improvements include: (1) The existing model divides the oil-gas interface by judging the oil-gas volume ratio in each grid, which is more suitable for solving physical problems with clear phase boundaries. Since the dynamic pressure oil-gas separator and the oil tank contain complex flow states such as inlet bubbly flow, main body stratified flow and oil pool disturbance flow, the prediction accuracy of the model in the oil-gas distribution pattern and the velocity field, the pressure field and other parameters, and the adaptability of the model to the working condition changes all need to be improved.

[0007] (2) The flow path of some new oil-gas separator is more complex, which will disturb the oil-gas flow in the oil tank, and the calculation domain of the existing model is limited to the oil-gas separator, which cannot study the oil-gas separation mechanism when the separator and the oil tank work together.

[0008] (3) When the grid is encrypted to improve the solving accuracy, the calculation amount of this solving method is very large when the existing model describes the oil-gas two-phase motion by solving single-phase / two-phase control equations in each calculation grid. SUMMARY

[0009] To solve the above technical problems, the present application provides a dynamic pressure oil-gas separator and oil tank collaborative simulation method, which comprises the following steps: Step 1: Establish a three-dimensional geometric model of the whole oil tank and oil-gas separator, and establish a common node monitoring surface at the connection between the oil-gas separator and the oil tank; then discretize the continuous geometric model into a finite number of calculation grids; adopt polyhedral grid, each grid unit is surrounded by multiple polygonal faces, and more than 6 adjacent units share the face, and finally get the discretized coupling calculation domain of the oil tank and the oil-gas separator; Step 2: Based on the coupling calculation domain, establish a control equation group for simulation calculation, which is used to calculate the physical quantity in each discrete grid; Step 3: Collect the flow parameters and physical parameters and input them into the control equation group, use the solver to solve the equation group, and calculate the field data of the oil-gas distribution field, the pressure field and the velocity field; Step 4: The calculated field data results are imported into the post-processing software, and the time-averaged velocity distribution of each part of the lubricating oil tank and the oil-gas separator, as well as the mass flow of the inlet and outlet lubricating oil and air, can be obtained; Step 5: The mass flow monitoring data of lubricating oil and air at a specific position are imported into the post-processing software, and the oil-gas separator body separation efficiency and the overall oil-gas separation efficiency of the lubricating oil tank can be calculated, and the simulation is completed.

[0010] Further, a control equation set is constructed based on the homogeneous flow assumption, which allows the oil and gas two phases to penetrate each other, and the volume fraction of any phase in a single control volume can take any value in the interval 0~1, which conforms to the actual situation of bubble dispersion distribution in lubricating oil; The equation set includes the following equations: 1) Continuity equation In the formula, and are the mass average velocity and density of the oil-gas mixture, and t is time.

[0011] 2) Momentum equation The momentum equations of each phase independent of each other can be added to obtain the momentum equation of the mixture, which is expressed as: Where n is the number of phases, is the volume force, is the viscosity of the mixture, is the acceleration of gravity, is the volume fraction of the kth phase, is the density of the kth phase, is the drift velocity of the secondary phase air.

[0012] 3) Slip velocity equation Slip velocity refers to the velocity of the gas phase relative to the velocity of the lubricating oil phase, and the displacement between the oil and gas two phases is represented by this variable: In order to specify the algebraic relationship of the relative velocity, local balance between oil and gas should be achieved on a small spatial scale. The slip velocity can also be written as: Where is the relaxation time of the particle, is the density of the bubble, is the acceleration of the air bubble. The resistance function formula is: 4) Interfacial area concentration equation The interfacial area concentration is defined as the interfacial area per 1 m 3The interfacial area between the two phases. Since the size and distribution of bubbles change rapidly due to growth, pressure variations leading to expansion, coalescence, breakup, or nucleation mechanisms, this parameter is used to predict mass, momentum, and energy transfer across the phase interface. The transport equation for interfacial concentration is: in It is the interfacial area concentration (m²) 2 / m 3 ), , , These represent the volume fraction, density, and velocity of air, respectively. The first two terms on the right-hand side of the equation are due to bubble expansion caused by compressibility and phase change mass transfer. It is the mass transfer rate per unit volume of the gas phase mixture (kg / m³). 3 / s). S RC and S WE These are coalescing sink terms caused by random collisions and wake entrainment, respectively. TI It is a fragmentation source term caused by turbulent impact.

[0013] After constructing the system of equations, a solver was used to solve them. The least-squares gradient was used as the gradient term discretization method, and the PRESTO! scheme was used for interpolation of the pressure term. The control equations were discretized using a second-order upwind scheme, and the geometric reconstruction method was used to interpolate the control volume between the gas and liquid phases. The compression scheme is a second-order reconstruction scheme based on a slope limiter; this model uses the compression scheme to describe sharp / dispersed interfaces.

[0014] Furthermore, in step 5, the separation efficiency of the oil-gas separator body is calculated using the following method: The sum of the mass flow rates of the lubricating oil discharged from each drain hole, divided by the mass flow rate of the inlet lubricating oil: The overall oil-gas separation efficiency of the lubricating oil tank is calculated by dividing the air mass flow rate at the exhaust port by the air mass flow rate at the inlet: .

[0015] The present application adopts control equation groups based on the assumption of homogeneous flow, and realizes the tracking of the flow state evolution process from oil-gas dispersed mixed flow to oil-gas stratified flow by coupling solving the phase boundary area density equation and the second-order interface reconstruction equation based on slope limitation. The simulation results show that in the commonly used working condition range of the engine, the model can monitor the flow of the small flow channel of the separator, and then calculate the separation efficiency of the separator body, and the prediction accuracy of the oil-gas two-phase distribution and flow field is also improved compared with other models. The simulation method can couple the transient flow field, pressure field, vortex intensity and other parameters of the oil-gas separator and the oil tank, so as to realize the numerical simulation of the built-in oil-gas separator of the oil tank, and reveal the oil-gas separation mechanism of oil-gas from dispersed mixed state to stratified flow state under the coupling action of centrifugal force and gravity. The simulation method only solves a set of control equation groups of oil / air mixture, and calculates the velocity difference between oil and gas phases in each control body by introducing the slip velocity equation, so that ideal solving accuracy can be obtained by using general resolution calculation grid, thereby greatly reducing the calculation time cost. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Oil-gas separator velocity cloud map Figure 2 Oil-gas distribution cloud map Figure 3 Computational domain schematic diagram Figure 4 Oil tank oil return flow state schematic diagram Figure 5 Mean tangential velocity along diameter distribution schematic diagram of cylindrical section (z=15mm) Figure 6 Mean tangential velocity along diameter distribution schematic diagram of conical section (z=-24mm) Figure 7 Separator body separation efficiency comparison schematic diagram Figure 8 Oil tank overall separation efficiency comparison schematic diagram DETAILED DESCRIPTION

[0017] The principles and characteristics of the present application are described below in combination with the drawings, and the examples are only used to explain the present application, and are not used to limit the scope of the present application.

[0018] The purpose of the present application is to establish a simulation analysis method of a built-in dynamic pressure type oil-gas separator of an oil tank, which can be applied to a wide range of engine operating conditions and structure size changes of the oil-gas separator and the oil tank. The core of the method can be refined into three steps: (1) Coupling of the discretization of the calculation domain First, the overall three-dimensional geometric model (such as Figure 3The continuous geometric model is then discretized into a finite number of computational grids. In order to make the grid more conformal to the geometric structure, the method uses polyhedral grids, each grid cell is surrounded by multiple polygonal faces, and more than 6 adjacent cells share the face, which can enhance the data transmission efficiency, and make the physical quantity (including velocity, pressure) gradient interpolation more accurate, and the residual error convergence speed faster. The final step is to obtain the discretized coupling calculation domain of the oil tank and the oil-gas separator.

[0019] The continuous geometric model is then discretized into a finite number of computational grids. In order to make the grid more conformal to the geometric structure, the method uses polyhedral grids, each grid cell is surrounded by multiple polygonal faces, and more than 6 adjacent cells share the face, which can enhance the data transmission efficiency, and make the physical quantity (including velocity, pressure) gradient interpolation more accurate, and the residual error convergence speed faster. The final step is to obtain the discretized coupling calculation domain of the oil tank and the oil-gas separator.

[0020] (2) Construction of the control equation set The second step of the method is to establish the control equation set for the simulation calculation, which is used to calculate the physical quantity in each discrete grid. In the oil return pipeline of the engine lubrication system, the oil and air are in a dispersed bubble flow state (as shown in Figure 4 ), and the coupling between oil and gas is strong.

[0021] In order to solve this flow state problem, the control equation set can be constructed based on the homogeneous flow assumption, which allows the oil and gas two phases to penetrate each other, and the volume fraction of any phase in a single control volume can take any value in the interval 0~1, which is very consistent with the actual situation of the dispersion of bubbles in the oil. The equation set includes the following equations: 1) Continuity equation In the formula and are the mass average velocity and density of the oil-gas mixture.

[0022] 2) Momentum equation The independent phase momentum equations can be added to obtain the mixture momentum equation, which is expressed as: Where n is the number of phases, is the volume force, is the viscosity of the mixture, is the acceleration of gravity, is the volume fraction of the kth phase, is the density of the kth phase, is the drift velocity of the secondary phase air.

[0023] 3) Slip velocity equation Slip velocity refers to the velocity of the gas phase relative to the oil phase, and the displacement between the oil and gas two phases is characterized by the variable: To define the algebraic relation of relative velocity, local balance between oil and gas should be reached in small spatial scale. The slip velocity can also be written as: where is the relaxation time of particles, is the density of bubbles, is the acceleration of air bubbles. The drag function is given by: 4) Interfacial area concentration equation The interfacial area concentration is defined as the interfacial area per 1 m 3 between the two phases in the oil-gas mixture. Since the size of bubbles and its distribution can change rapidly due to growth, expansion due to pressure change, coalescence, breakup or nucleation mechanisms, this parameter is used to predict the mass, momentum and energy transfer across the phase interface. The transport equation for the interfacial area concentration is: where is the interfacial area concentration (m 2 / m 3 ), , , are the volume fraction, density and velocity of air, respectively. The first two terms on the right hand side are due to the expansion of the bubble due to compressibility and phase change mass transfer. is the mass transfer rate inside the gas phase per unit volume of mixture (kg / m 3 / s). S RC and S WE are the coalescence sink terms due to random collision and wake entrainment, respectively. S TI is the breakup source term due to turbulent impaction.

[0024] After the construction of the system of equations, the solver is used to solve the system of equations. The least-squares gradient is used as the discretization method for the gradient term, the PRESTO! scheme is used for the interpolation of the pressure term, the second order upwind scheme is used for the discretization of the governing equations, and the Geometric reconstruction method is used for the interpolation of the control volume between the gas-liquid interface. The compressive scheme is a second-order reconstruction scheme based on the slope limiter, and the model uses the compressive scheme to describe the sharp / dispersed interface.

[0025] (3) Evaluation of separation efficiency A set of examples can illustrate the whole process from parameter import to the separation efficiency.

[0026] 1) Input flow parameters and physical property parameters. The densities and viscosities of the oil and air corresponding to each oil temperature are input into the solver in turn as shown in Table 1.

[0027] Table 1 Simulation conditions 2) Calculate the internal physical quantity field of the oil-gas separator and the oil tank. The solver calculates the data of the oil-gas distribution field, the pressure field and the velocity field, which are stored in the solver for later calling.

[0028] 3) Perform data analysis to obtain the velocity distribution law. The time-averaged velocity values in the oil-gas separator and the oil tank, as well as the mass flow rates of the inlet and outlet oil and air are extracted, and the calculation results are imported into the post-processing software origin, so that the time-averaged velocity distribution curves at each place can be obtained, as shown in Figure 5 and Figure 6 .

[0029] Figure 5 is the time-averaged tangential velocity along the diameter in the cylindrical section. Under each condition, the velocity value near the side wall of the separator is the highest, and the velocity value of the oil and gas close to the side wall decreases to almost 0. With the decrease of the radius, the tangential velocity gradually decreases to 0, and this velocity distribution conforms to the velocity characteristics of forced vortex. By comparing A1, A6, A7 and A8, under the condition that the inlet oil volume flow rate is constant, as the oil-gas ratio increases, the air volume flow rate also increases, resulting in an increase in the tangential velocity. By comparing A1, A4 and A5, under the condition that the oil-gas ratio is constant, as the inlet volume flow rate increases, the tangential velocity of the two-phase flow increases. By comparing A1, A2 and A3, as the temperature of the oil-gas mixture increases, the viscosity of the oil-gas decreases, resulting in an increase in the tangential velocity, but the change is slight.

[0030] Figure 6 is the time-averaged tangential velocity along the diameter at the second oil hole in the conical section. As shown in the figure, under each condition, the tangential velocity first increases along the radial direction from the side wall to the center, and then decreases at about ±0.75R to the minimum speed of about 0. The flow field distribution meets the characteristics of combined vortex, i.e. free vortex near the side wall and forced vortex at the center of the separator. It is found by comparison that increasing the oil-gas ratio and increasing the volume flow rate can significantly increase the tangential flow velocity of the oil-gas mixture in the conical section, while the change of temperature has little effect on the tangential velocity.

[0031] 4) Calculate the separation efficiency. The oil mass flow rate and air mass flow rate parameters at a specific position are imported into the post-processing software excel, so that the oil-gas separator body separation efficiency and the oil-gas separation efficiency of the entire oil tank can be calculated, as shown in Figure 7 and Figure 8 .

[0032] The calculation method of the oil-gas separator body separation efficiency is to use the sum of the mass flow rate of the discharged lubricating oil of each oil discharge hole divided by the inlet lubricating oil mass flow rate: The calculation method of the oil-gas separator body separation efficiency is to use the sum of the mass flow rate of the discharged lubricating oil of each oil discharge hole divided by the inlet lubricating oil mass flow rate: As shown in Figure 7 , when the temperature decreases, the density of the lubricating oil and air increases, and the viscosity of the lubricating oil increases, thereby causing greater flow shear force and causing greater flow loss. When the temperature increases, the density and viscosity of the lubricating oil and air decrease, thereby causing the flow shear force to decrease and thereby reducing the flow resistance, causing the separation efficiency to increase. When the volume flow rate of the oil-gas mixture decreases or increases, the mass flow rate also decreases or increases, respectively, which causes the flow rate of the oil-gas mixture to decrease or increase, respectively, thereby causing the centrifugal force to decrease or increase, thereby causing the separation efficiency to decrease or increase. As the oil-gas ratio increases, the greater the volume flow rate of the air, the higher the overall flow rate of the oil-gas mixture, and the stronger the separation centrifugal force, and therefore the separation efficiencies of A6, A1, A7, and A8 also increase in turn.

[0033] As shown in Figure 8 , when the temperature decreases, the decrease in the overall separation efficiency of the lubricating oil tank is greater than the decrease in the separation efficiency of the separator body. When the volume flow rate of the oil-gas, that is, the total energy input from the outside, decreases, this will cause the flow rate of the oil-gas mixture thrown outward to decrease. The disturbance of the oil-gas mixture with a lower flow rate to the oil pool of the lubricating oil tank decreases, and therefore the separation efficiency increases. When the volume flow rate of the oil-gas increases, this will cause the flow rate of the oil-gas mixture thrown outward to increase. The disturbance of the oil-gas mixture with a higher flow rate to the oil pool of the lubricating oil tank increases, and therefore the generation of oil mist in the lubricating oil tank increases, causing more lubricating oil to escape from the air outlet, and therefore the separation efficiency decreases. As the oil-gas ratio increases, the total energy input from the outside of the oil-gas mixture also increases. When the flow rate of the oil-gas mixture decreases, the disturbance of the oil-gas mixture to the oil pool of the lubricating oil tank is small, there are fewer air bubbles in the oil pool, and the amount of air escaping from the air inlet decreases, and therefore the separation efficiency increases. If the flow rate of the mixture increases, the disturbance of the mixture to the oil pool of the lubricating oil tank is more severe, a large number of air bubbles are formed in the oil pool, the amount of air escaping from the air inlet increases, and therefore the separation efficiency decreases.

[0034] According to the simulation results, the following conclusions can be drawn: 1) Under different inlet conditions such as lubricating oil flow rate, lubricating oil temperature, and oil-gas ratio, simulation analysis is performed to obtain the separation characteristics of the two-phase flow that conforms to the objective physical law, indicating that the model can effectively describe the behavior of bubbles converging, breaking up in the dispersed flow, and the entire process of completely separating from the oil, and is a numerical calculation method that has wide operating condition applicability and high robustness for analyzing the coupling of the oil-gas separator and the lubricating oil tank.

[0035] 2) The short circuit vortex can re-entrain part of the oil thrown to the side wall into the central upward airflow, which has a negative impact on oil-gas separation. The main vortex can promote the downward flow of oil and the upward flow of air, and the bottom vortex helps to suck air from the oil tank, thereby forming an air column. The two effective vortices are closely coupled with each other and influence each other. This is the separation mechanism of the modified dynamic pressure oil-gas separator.

[0036] 3) The simulation method can effectively predict the separation efficiency of the oil-gas separator body and the overall oil-gas separation efficiency of the oil tank, and can image the velocity field, oil-gas distribution field and other parameters of the oil tank.

[0037] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for simulating a dynamic pressure oil and gas separator in cooperation with an oil tank, characterized in that, Comprising the following steps, Step 1: Establish a three-dimensional geometric model of the oil tank and oil-gas separator as a whole, and establish a co-node monitoring surface at the connection between the oil-gas separator and the oil tank; then discretize the continuous geometric model into a finite number of calculation grids; adopt polyhedral grids, each grid unit is surrounded by multiple polygonal faces, shares faces with more than 6 adjacent units on average, and finally obtains the discretized coupling calculation domain of the oil tank and the oil-gas separator; Step 2: Based on the coupling calculation domain, establish the control equation set for simulation calculation, which is used to calculate the physical quantity in each discrete grid; Step 3: Collect the flow parameters and physical parameters and input them into the control equation set, solve the equation set using a solver, and calculate the field data of the oil-gas distribution field, pressure field and velocity field; Step 4: Import the calculated field data results into post-processing software such as origin, and obtain the time-averaged velocity distribution at each place inside the oil tank and oil-gas separator, as well as the mass flow of inlet and outlet oil and air; Step 5: Import the mass flow monitoring data of oil and air at a specific position into post-processing software such as excel, and calculate the oil-gas separator body separation efficiency and the overall oil-gas separation efficiency of the oil tank to complete the simulation.

2. The dynamic pressure type oil-gas separator and oil tank collaborative simulation method according to claim 1, characterized in that, The control equation set is constructed based on the assumption of homogeneous flow, which allows the gas-liquid two-phase to penetrate each other, and the volume fraction of any phase in a single control volume can take any value in the interval 0~1, which conforms to the actual situation of bubble dispersion distribution in oil; The equation set includes the following equations: Continuity equation where and are the mass average velocity and density of the oil and gas mixture, respectively, and t is time. Momentum equation The momentum equations of each independent phase can be added to obtain the momentum equation of the mixture, which is expressed as: where n is the number of phases, is the volume force, is the mixture viscosity, is the gravitational acceleration, is the volume fraction of the kth phase, is the density of the kth phase, is the drift velocity of air; Slip velocity equation Slip velocity refers to the velocity of the gas phase relative to the oil phase, which characterizes the displacement between oil and gas: In order to specify the algebraic relationship of relative velocity, local balance between oil and gas should be achieved on a small spatial scale; Slip velocity can also be written as: wherein, is the relaxation time of the bubble, is the density of the bubble, is the acceleration of the air bubble; the drag function is given by: Interface area concentration equation Interface area concentration is defined as the interface area between the two phases per 1m3 of oil-gas mixture; Since the size and distribution of bubbles can change rapidly due to growth, expansion caused by pressure change, coalescence, fragmentation or nucleation mechanism, this parameter is used to predict mass, momentum and energy transfer through the phase interface; The transport equation of interface concentration is: wherein, is the interfacial area concentration (m2 / m3), , , are the volume fraction, density, and velocity of air, respectively; the first two terms on the right-hand side are the bubble expansion due to compressibility and phase change mass transfer; is the mass transfer rate inside the gas phase per unit volume of mixture (kg / m3 / s); SRC and SWE are the coalescence sink terms due to random collision and wake entrainment, respectively; STI is the break-up source term due to turbulent impaction; after the completion of the system of equations, the system of equations is solved using a solver.

3. The method of claim 2, wherein, The least-squares gradient is used as the gradient term discretization method, the PRESTO! format is used for pressure term interpolation, the second-order upwind format is used for control equation discretization, and the Geometric reconstruction method is used for interpolation of control bodies between gas-liquid phase interfaces; The compression format is a second-order reconstruction format based on slope limiter, and the compression format is used to describe sharp / dispersed interfaces in this model.

4. The method of claim 1, wherein, In step 5, the oil-gas separator body separation efficiency is calculated by the following method, The sum of the mass flow of oil discharged through each oil drain hole is divided by the inlet oil mass flow: The calculation method of the oil-gas separation efficiency of the lubricating oil tank as a whole is to divide the air mass flow at the exhaust port by the air mass flow at the inlet: 。

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