Judgment method for leakage of airplane reciprocating motion part series sealing system

Abstract

The invention discloses a method for judging leakage of a series sealing system of aircraft reciprocating motion parts. The method comprises the following steps: S1, constructing a two-dimensional axis model; s2, setting material attribute parameters; s3, defining an analysis step; s4, setting a friction coefficient; s5, defining boundary conditions and loads; s6, carrying out grid division; s7, calculating contact pressure distribution data; s8, oil film thickness distribution is obtained through calculation; S9, the contact pressure of each sealing face is calculated; s10, the flow in the two combined seals is calculated; and S11, obtaining a leakage conclusion of the series sealing system. Reliable sealing performance can be directly obtained through a simulation calculation technology, the problems of long test period, high cost and the like in a real object test are avoided, and the sealing performance test universal for different types of airplane reciprocating motion part sealing systems is realized. Through finite element simulation and multi-object-field fluid-solid coupling numerical simulation, interaction between the series sealing systems is analyzed, and whether the series sealing systems leak or not can be accurately determined.

Description

Technical Field

[0001] This invention relates to the field of hydraulic conduit reliability testing technology, specifically to a method for judging the leakage of a series sealing system for reciprocating motion components of an aircraft. Background Technology

[0002] With the development of modern industry, the operating environment of equipment in various industrial fields is becoming increasingly extreme. Sealing systems, facing high-temperature and high-pressure environments, struggle to achieve good sealing results with a single combined sealing element. Sealing systems often represent the operational quality and safety of equipment. To ensure the normal operation of advanced equipment, especially the safe and smooth operation of aircraft, the use of two or more combined seals in series under these extreme conditions is becoming increasingly urgent. However, not all combinations of seals in series will achieve good sealing results. In reciprocating sealing systems, the presence of the first combined seal directly affects the lubrication effect of the second combined seal, potentially leading to "trapped oil" or "exhausted oil" phenomena during operation. Therefore, it is necessary to design a suitable series sealing system based on the operating conditions and application environment.

[0003] A double-sealed tandem seal consists of two sealing elements arranged and installed sequentially, typically as the first and second seals along the direction of media flow. Its structural characteristics are: The first seal is the primary seal, mainly responsible for blocking the medium; the second seal is an auxiliary seal. An intermediate cavity is provided between the two seals to allow the injection of lubricating fluid or to drain leaked medium, enhancing the sealing effect and safety.

[0004] The two combined sealing structures are arranged in series to jointly prevent media leakage and enhance sealing reliability.

[0005] The inner stroke is the range of travel traversed by the combined sealing element when the moving part moves inward. The outer stroke is the range of travel traversed by the combined sealing element when the moving part moves outward. The outer stroke flow rate is the flow rate of lubricating fluid carried out when the moving part extends out of the cavity. The inner stroke flow rate is the flow rate of lubricating fluid carried in when the moving part retracts into the cavity.

[0006] In the aerospace industry, the design of sealing systems for reciprocating aircraft components often relies on experimental methods to assess whether the sealing system meets requirements. This results in long testing cycles, high costs, and other waste. Furthermore, limitations imposed by testing equipment, such as the different testing equipment required for different types of components, can hinder the successful conduct of design verification tests. Therefore, proposing a systematic calculation method for testing the sealing performance of this tandem sealing system during the design phase is of great significance.

[0007] Patent application CN116757012A discloses a method for simulating and analyzing the sealing performance of a pipeline assembly under vibration by using CATIA, Hypermer, and Workbench software in combination and changing the vibration load point and amplitude. Patent application CN115906571B discloses a simulation analysis method for plunger pair sealing under different operating conditions, including material degradation, sealing gap distribution, and sealing pressure. Both simulation analysis methods only obtain the sealing performance of the test object by changing certain operating conditions. They do not consider the differences in sealing performance that may result from the interaction between sealing systems or the mutual influence within series seals, and they do not comprehensively consider the current state of the sealing system, thus having certain limitations. Summary of the Invention

[0008] This invention addresses the problems existing in the series sealing systems of reciprocating motion components in aircraft by proposing a method for judging the leakage of such systems. This method can predict the leakage amount of the series sealing system and achieve reliable sealing performance directly through simulation calculations, avoiding the problems of long test cycles and high costs associated with physical testing. Furthermore, this invention is not limited by testing equipment and can be applied to the sealing performance testing of sealing systems in different types of reciprocating motion components of aircraft. Through finite element simulation and multi-field fluid-structure interaction numerical simulation, based on the principle of flow conservation, the interactions between the series sealing systems are analyzed, and the occurrence of leakage in the series sealing system can be accurately determined.

[0009] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: A method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft includes the following steps: S1. Construct a two-dimensional shaft model using ABAQUS finite element simulation software, where the landing gear piston rod and outer cylinder parts are set as non-deformable rigid bodies, and the combined seal is set as a deformable body. S2. Set the material property parameters of the deformable body material in the two-dimensional axisymmetric model; S3. Define the analysis steps in the two-dimensional axisymmetric model according to the actual operation, and determine the process of interference fit state, applying corresponding displacement and sealing pressure load; S4. Set the friction coefficient of the sealing surface in the two-dimensional axisymmetric model; S5. Define boundary conditions and loads in a two-dimensional axisymmetric model; S6. In the two-dimensional axisymmetric model, mesh the deformable body and adjust the mesh density of each component and the main analysis area; S7. The contact pressure distribution data of each sealing surface is calculated using simulation software; S8. The initial oil film thickness distribution of each sealing surface is calculated using the Reynolds equation. S9. Introduce the GW model and calculate the contact pressure of each sealing surface using the GW model; S10. Calculate the internal and external stroke flow rates of each combined seal by contact pressure, and continuously correct the cavity pressure values ​​between adjacent combined seals until the calculated flow rates of each combined seal are equal. S11. By comparing the flow rates of the inner and outer strokes of the two combined seals, the conclusion of leakage in the series sealing system is drawn.

[0010] The materials of the combined seal in step S1 are rubber and plastic. In step S2, the material property parameters of the deformable body include Young's modulus and Poisson's ratio; In step S4, the friction coefficients of the sealing surfaces include 0.08~0.12 for the piston rod, outer cylinder and plastic contact, 0.39~0.43 for the piston rod, outer cylinder and rubber contact, and 0.17~0.23 for the plastic and rubber contact.

[0011] In step S5, the boundary conditions and loads are defined as applying constraints to the motion boundary of the indeformable rigid body to ensure the motion of each component as boundary conditions; the process of applying pressure to a fluid is simulated by applying a surface pressure load.

[0012] In step S8, calculating the oil film thickness distribution of each sealing surface using the Reynolds equation includes the following steps: S81. The phenomenon of viscous flow of fluid in a confined space is described by the Reynolds equation, which is shown below:

[0013] in or * Indicates fluid viscosity; u * Circumferential velocity; r * The density of the lubricating oil; h * Indicates the thickness of the oil film; t * Indicates time; x * Indicates circumferential position; y * Indicates axial position; p * f Indicates oil film pressure; S82. The Reynolds equation includes oil film thickness on the order of micrometers and oil film pressure on the order of megapascals. To reduce errors, the Reynolds equation is transformed into a dimensionless form, as shown in the following equation:

[0014] in, K Indicates the pressure flow influencing factor; x This indicates that the circumferential position is dimensionless; p This indicates that the oil film pressure is dimensionless; y This indicates that the axial position is dimensionless; c1 Indicates dimensionless velocity; c2 Indicates the squeezing influencing factor; r This indicates that the density of the lubricating oil is dimensionless; h This indicates that the oil film thickness is dimensionless; t This indicates that time is dimensionless; S83. Set the contact pressure distribution to be the same as the oil film pressure distribution, and solve the Reynolds equation in reverse to obtain the initial oil film thickness distribution.

[0015] In step S9, calculating the contact pressure of each sealing surface using the GW model includes the following steps: S91. Using the GW model, the contact between the two rough surfaces of each sealing surface is simplified to a purely elastic contact between an absolutely smooth rigid surface and another rough surface. Furthermore, the rough peaks are considered to be regular hemispheres. The total contact pressure of the rough peaks is shown in the following formula:

[0016] Where R represents the average roughness peak radius. d c E' represents the average roughness peak height, and E′ represents the equivalent elastic modulus of the two rough surfaces. h Indicates the oil film thickness; W represents the total contact pressure of the rough peaks; S92. Assume that the rough peaks satisfy a Gaussian distribution, and the average contact pressure of the rough peaks is as shown in the following formula:

[0017] in or Indicates the density of rough peaks; s P represents the standard deviation of the rough peak. con Z represents the average contact pressure of the rough peak; Z represents the height between the rough peak and the smooth surface; d z This represents the derivative of the height (Z) between the rough peak and the smooth plane; S93. Calculate the rough peak contact stress based on the oil film thickness, and add the rough peak contact stress to the oil film pressure to obtain the contact pressure of each sealing surface.

[0018] Step S9 further includes the following steps: S94. Compare the contact pressure of each sealing surface with the contact pressure calculated by finite element simulation, and use the oil film pressure P f Rough peak contact pressure P con The contact pressure P calculated by finite element simulation sc Calculate the unbalanced stress P f ; Unbalanced stress = P f+ P con- P sc ; S95. Calculation of micro-deformation in the lip contact area using unbalanced stress. d Correct the local oil film thickness to d+h Recalculate the contact pressure of each sealing surface until the unbalanced stress is less than 10. -5 .

[0019] In step S10, the flow rate within the two combined seals is calculated using the following formula:

[0020] in, Indicates the pressure flow influence coefficient; Oil film thickness; This refers to the local oil film thickness. x* Indicates circumferential position; y* Indicates axial position; p* f Indicates oil film pressure; Indicates the pressure flow influence coefficient; This represents the roughness influence coefficient; Indicates the cavitation index; Indicates dimensionless velocity; Indicates the diameter of the rod.

[0021] In step S11, comparing the inner and outer stroke flow rates of the two combined seals to draw a conclusion on leakage of the series sealing system includes: if the inner stroke flow rate is greater than or equal to the outer stroke flow rate, the series sealing system is considered to be non-leaking; if the inner stroke flow rate is less than the outer stroke flow rate, the series sealing system is considered to be leaking.

[0022] The beneficial effects of this invention are: 1. This invention uses simulation and multi-field fluid-structure interaction to determine the leakage of a series sealing system for reciprocating motion components of an aircraft. Based on the principle of flow conservation, by extracting the contact pressure of the combined seals and solving the Reynolds equation and GW model, the pressure in the intermediate cavity can be effectively predicted and the leakage can be calculated. Using this technical solution as a preliminary preparation for landing gear design can greatly reduce the possibility of leakage in the landing gear sealing system.

[0023] 2. This invention enables simultaneous simulation experiments at the design stage, avoiding blind enhancement of the tandem sealing system and thus eliminating unnecessary physical testing. This accelerates R&D efficiency while reducing testing costs. The results report of this invention can serve as a design basis for a product, allowing for evaluation of the sealing performance of the sealing system based on leakage issues during the landing gear product design phase, and facilitating product optimization.

[0024] 3. This invention optimizes the design parameters of combined sealing components in a sealing system, and has strong applicability. This invention is applicable to various sealing systems and can also optimize the design parameters of various sealing components. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the method for determining leakage in a series sealing system of reciprocating motion components of an aircraft according to the present invention.

[0026] Figure 2 This is a schematic diagram of the series sealing system for the reciprocating motion components of the machine in this invention.

[0027] Figure 3 This is a schematic diagram of the sealing surface contact pressure of the first combined seal in the series sealing system of the reciprocating motion components of the machine in this invention.

[0028] Figure 4 This is a schematic diagram of the contact pressure of the sealing surface of the second combined seal in the series sealing system of the reciprocating motion components of the present invention.

[0029] Figure 5 This is a schematic diagram showing the inner and outer stroke flow rates and leakage conclusions of the two combined seals in the series sealing system of the reciprocating motion components of the machine in this invention. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0031] Example 1 This embodiment provides a method such as Figure 1 The method shown for determining leakage in a series sealing system for reciprocating moving parts of an aircraft includes the following steps: S1. Construct a two-dimensional shaft model using ABAQUS finite element simulation software, where the landing gear piston rod and outer cylinder parts are set as non-deformable rigid bodies, and the combined seal is set as a deformable body. The piston rod and outer cylinder of the landing gear have very small deformation in actual application and can be set as non-deformable rigid bodies. The combined seals are usually made of rubber and plastic materials, so they have a large deformation and are set as deformable bodies. S2. Set the material property parameters of the deformable body material in the two-dimensional axisymmetric model; The material properties of deformable bodies include Young's modulus and Poisson's ratio; S3. Define the analysis steps in the two-dimensional axisymmetric model according to the actual operation, and determine the process of interference fit state, applying corresponding displacement and sealing pressure load; S4. Set the friction coefficient of the sealing surface in the two-dimensional axisymmetric model; The friction coefficients of the sealing surfaces include 0.08~0.12 for the piston rod and outer cylinder in contact with plastic, 0.39~0.43 for the piston rod and outer cylinder in contact with rubber, and 0.17~0.23 for the plastic in contact with rubber. S5. Define boundary conditions and loads in a two-dimensional axisymmetric model; Boundary conditions and loads are defined as constraints imposed on the motion boundaries of the indeformable rigid body to ensure the motion of each component; the process of fluid applying pressure is simulated by applying surface pressure loads.

[0032] S6. In the two-dimensional axisymmetric model, mesh the deformable body and adjust the mesh density of each component and the main analysis area; the mesh shape should be mainly quadrilateral. S7. The contact pressure distribution data of each sealing surface is calculated using simulation software; S8. The initial oil film thickness distribution of each sealing surface is calculated using the Reynolds equation; this includes the following steps: S81. The phenomenon of viscous flow of fluid in a confined space is described by the Reynolds equation, which is shown below:

[0033] in or * Indicates fluid viscosity; u * Circumferential velocity; r * The density of the lubricating oil; h * Indicates the thickness of the oil film; t * Indicates time; x * Indicates circumferential position; y * Indicates axial position; p * f Indicates oil film pressure; S82. The Reynolds equation includes oil film thickness on the order of micrometers and oil film pressure on the order of megapascals. To reduce errors, the Reynolds equation is transformed into a dimensionless form, as shown in the following equation:

[0034] in K Indicates the pressure flow influencing factor; x This indicates that the circumferential position is dimensionless; p This indicates that the oil film pressure is dimensionless; y This indicates that the axial position is dimensionless; c1 Indicates dimensionless velocity; c2 Indicates the squeezing influencing factor; r This indicates that the density of the lubricating oil is dimensionless; h This indicates that the oil film thickness is dimensionless; t This indicates that time is dimensionless; S83. Set the contact pressure distribution to be the same as the oil film pressure distribution, and solve the Reynolds equation in reverse to obtain the initial oil film thickness distribution.

[0035] S9. Introduce the GW model and calculate the contact pressure of each sealing surface using the GW model; S91. Using the GW model, the contact between the two rough surfaces of each sealing surface is simplified to a purely elastic contact between an absolutely smooth rigid surface and another rough surface. Furthermore, the rough peaks are considered to be regular hemispheres. The total contact pressure of the rough peaks is shown in the following formula:

[0036] Where R represents the average roughness peak radius. d c E' represents the average roughness peak height, and E′ represents the equivalent elastic modulus of the two rough surfaces. h Indicates the oil film thickness; W represents the total contact pressure of the rough peaks; S92. Assume that the rough peaks satisfy a Gaussian distribution, and the average contact pressure of the rough peaks is as shown in the following formula:

[0037] in or Indicates the density of rough peaks; s P represents the standard deviation of the rough peak. con Z represents the average contact pressure of the rough peak; Z represents the height between the rough peak and the smooth surface; d z This represents the derivative of the height (Z) between the rough peak and the smooth plane; S93. Calculate the rough peak contact stress based on the oil film thickness, and add the rough peak contact stress to the oil film pressure to obtain the contact pressure of each sealing surface.

[0038] Step S9 further includes the following steps: S94. Compare the contact pressure of each sealing surface with the contact pressure calculated by finite element simulation, and use the oil film pressure P f Rough peak contact pressure P con The contact pressure P calculated by finite element simulation sc Calculate the unbalanced stress P f ; Unbalanced stress = P f+ P con- P sc ; S95. Calculation of micro-deformation in the lip contact area using unbalanced stress. d Correct the local oil film thickness to d+h Recalculate the contact pressure of each sealing surface until the unbalanced stress is less than 10. -5 .

[0039] S10. Calculate the internal and external stroke flow rates of each combined seal by contact pressure, and continuously correct the cavity pressure values ​​between adjacent combined seals until the calculated flow rates of each combined seal are equal. The flow rate within the two combined seals is calculated using the following formula:

[0040] in, Indicates the pressure flow influence coefficient; Oil film thickness; This refers to the local oil film thickness. x* Indicates circumferential position; y* Indicates axial position; p * f Indicates oil film pressure; Indicates the pressure flow influence coefficient; This represents the roughness influence coefficient; Indicates the cavitation index; Indicates dimensionless velocity; Indicates the diameter of the rod.

[0041] S11. By comparing the flow rates of the inner and outer strokes of the two combined seals, the conclusion of leakage in the series sealing system is drawn. If the internal stroke leakage rate is greater than or equal to the external stroke leakage rate, the series sealing system is considered to be leak-free; otherwise, the series sealing system is considered to be leaking.

[0042] Example 2 The difference between this embodiment and Embodiment 1 is that, in this embodiment, for example... Figure 2 The leakage of the series sealing system for the reciprocating motion components of the aircraft is assessed. In step S1, a two-dimensional axisymmetric model is constructed in the ABAQUS finite element simulation software. The piston rod and outer cylinder of the landing gear have very small deformation and can be set as non-deformable rigid bodies. The combined seal is usually composed of rubber and plastic materials and has a large deformation and is set as a deformable body.

[0043] In step S2, the Young's modulus and Poisson's ratio of the rubber and plastic materials are set respectively. The stress-strain data of the plastic material is obtained by uniaxial tensile-compression test and imported into the plastic properties in ABAQUS software. The elastic properties are set with an elastic modulus of 532 MPa and a Poisson's ratio of 0.46. The stress-strain data of the rubber material is obtained by equiaxial tensile-compression test and imported into the hyperelastic model in ABAQUS software. The strain potential energy relationship is selected as the Mooney-Rivlin model, and the strain potential energy order is first order with a Poisson's ratio of 0.495.

[0044] In step S3, the analysis steps in the actual operation process are defined, and processes such as assembly and load application are determined. Reasonable establishment of analysis steps can reduce non-convergence during simulation.

[0045] In step S4, the coefficient of friction between the piston rod, outer cylinder and plastic is set to 0.1, the coefficient of friction between the piston rod, outer cylinder and rubber is set to 0.4, and the coefficient of friction between plastic and rubber is set to 0.2.

[0046] In step S5, the three degrees of freedom of the outer cylinder and piston rod in the plane are set to 0. The process of applying pressure to the fluid is simulated by applying load, and the load is directly applied to the O-ring and plastic parts.

[0047] In step S6, the rubber and plastic parts are divided into meshes. The mesh shape is mainly quadrilateral, and the mesh around the parts is arranged in an edge-laying method to refine the surrounding mesh. The mesh can be modified later according to the convergence.

[0048] In step S7, a single-to-combination seal simulation project is created and submitted in the simulation software to obtain detailed data on the contact pressure distribution of the sealing surface.

[0049] In step S8, the viscous flow phenomenon of fluid in a confined space is described by the Reynolds equation. The Reynolds equation includes oil film thickness on the order of micrometers and oil film pressure on the order of megapascals. To reduce errors, the Reynolds equation is transformed into a dimensionless form:

[0050] Assuming that the contact pressure distribution is similar to the oil film pressure distribution, the Reynolds equation is solved in reverse to obtain the initial oil film thickness distribution.

[0051] In step S9, the GW model is introduced, and the contact pressure of the sealing surfaces of the two combined seals is calculated using the GW model; wherein the contact pressure of the sealing surface of the first combined seal is as follows: Figure 3 As shown, the contact pressure of the sealing surface of the second combined seal is as follows: Figure 4 As shown.

[0052] In step S10, the flow rate in the two combined seals is calculated by the contact pressure, and the pressure value of the intermediate cavity is continuously corrected until the flow rates calculated by the two combined seals are equal. In step S11, the leakage conclusion of the series sealing system is obtained by comparing the inner and outer stroke flow rates of the two combined seals. Specifically, in this embodiment, the inner and outer stroke flow rates and the leakage conclusion of the intermediate cavity for this two combined seal are as follows: Figure 5 As shown.

[0053] like Figure 5 As shown, in this embodiment, the external stroke flow rate of the first combined seal is greater than the internal stroke flow rate, so oil will accumulate in the intermediate cavity; the external stroke flow rate of the second combined seal is less than the internal stroke flow rate, so oil will also accumulate in the intermediate cavity. In the short term, the entire series sealing system will not leak, but in the long term, oil will accumulate in the intermediate cavity, forming "back pressure", and the sealing system will fail.

[0054] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft, characterized in that: Includes the following steps: S1. Construct a two-dimensional shaft model using ABAQUS finite element simulation software, where the landing gear piston rod and outer cylinder parts are set as non-deformable rigid bodies, and the combined seal is set as a deformable body. S2. Set the material property parameters of the deformable body material in the two-dimensional axisymmetric model; S3. Define the analysis steps in the two-dimensional axisymmetric model according to the actual operation, and determine the process of interference fit state, applying corresponding displacement and sealing pressure load; S4. Set the friction coefficient of the sealing surface in the two-dimensional axisymmetric model; S5. Define boundary conditions and loads in a two-dimensional axisymmetric model; S6. In the two-dimensional axisymmetric model, mesh the deformable body and adjust the mesh density of each component and the main analysis area; S7. The contact pressure distribution data of each sealing surface is calculated using simulation software; S8. The initial oil film thickness distribution of each sealing surface is calculated using the Reynolds equation. S9. Introduce the GW model and calculate the contact pressure of each sealing surface using the GW model; S10. Calculate the internal and external stroke flow rates of each combined seal by contact pressure, and continuously correct the cavity pressure values ​​between adjacent combined seals until the calculated flow rates of each combined seal are equal. S11. By comparing the flow rates of the inner and outer strokes of the two combined seals, the conclusion of leakage in the series sealing system is drawn.

2. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 1, characterized in that: The material of the combined seal in step S1 is rubber or plastic.

3. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 2, characterized in that: In step S2, the material property parameters of the deformable body include Young's modulus and Poisson's ratio.

4. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 2, characterized in that: In step S4, the friction coefficients of the sealing surfaces include 0.08~0.12 for the piston rod, outer cylinder and plastic contact, 0.39~0.43 for the piston rod, outer cylinder and rubber contact, and 0.17~0.23 for the plastic and rubber contact.

5. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 1, characterized in that: In step S5, the boundary conditions and loads are defined as applying constraints to the motion boundary of the indeformable rigid body to ensure the motion of each component as boundary conditions; the process of applying pressure to a fluid is simulated by applying a surface pressure load.

6. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 1, characterized in that: In step S8, calculating the oil film thickness distribution of each sealing surface using the Reynolds equation includes the following steps: S81. The phenomenon of viscous flow of fluid in a confined space is described by the Reynolds equation, which is shown below: in η * Indicates fluid viscosity; u * Circumferential velocity; ρ * The density of the lubricating oil; h * Indicates the thickness of the oil film; t * Indicates time; x * Indicates circumferential position; y * Indicates axial position; p * f Indicates oil film pressure; S82. The Reynolds equation includes oil film thickness on the order of micrometers and oil film pressure on the order of megapascals. To reduce errors, the Reynolds equation is transformed into a dimensionless form, as shown in the following equation: in, K Indicates the pressure flow influencing factor; x This indicates that the circumferential position is dimensionless; p This indicates that the oil film pressure is dimensionless; y This indicates that the axial position is dimensionless; γ1 Indicates dimensionless velocity; γ2 Indicates the squeezing influencing factor; ρ This indicates that the density of the lubricating oil is dimensionless; h This indicates that the oil film thickness is dimensionless; t This indicates that time is dimensionless; S83. Set the contact pressure distribution to be the same as the oil film pressure distribution, and solve the Reynolds equation in reverse to obtain the initial oil film thickness distribution.

7. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 6, characterized in that: In step S9, calculating the contact pressure of each sealing surface using the GW model includes the following steps: S91. Using the GW model, the contact between the two rough surfaces of each sealing surface is simplified to a purely elastic contact between an absolutely smooth rigid surface and another rough surface. Furthermore, the rough peaks are considered to be regular hemispheres. The total contact pressure of the rough peaks is shown in the following formula: Where R represents the average roughness peak radius. E' represents the average roughness peak height, and E′ represents the equivalent elastic modulus of the two rough surfaces. h Indicates the oil film thickness; W represents the total contact pressure of the rough peaks; S92. Assume that the rough peaks satisfy a Gaussian distribution, and the average contact pressure of the rough peaks is as shown in the following formula: in η Indicates the density of rough peaks; σ P represents the standard deviation of the rough peak. con Z represents the average contact pressure of the rough peak; Z represents the height between the rough peak and the smooth surface; d z This represents the derivative of the height (Z) between the rough peak and the smooth plane; S93. Calculate the rough peak contact stress based on the oil film thickness, and add the rough peak contact stress to the oil film pressure to obtain the contact pressure of each sealing surface.

8. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 7, characterized in that: Step S9 further includes the following steps: S94. Compare the contact pressure of each sealing surface with the contact pressure calculated by finite element simulation, and use the oil film pressure P f Rough peak contact pressure P con The contact pressure P calculated by finite element simulation sc Calculate the unbalanced stress P f ; Unbalanced stress = P f+ P con- P sc ; S95. Calculation of micro-deformation in the lip contact area using unbalanced stress. δ Correct the local oil film thickness to δ+h Recalculate the contact pressure of each sealing surface until the unbalanced stress is less than 10. -5 .

9. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 8, characterized in that: In step S10, the flow rate within the two combined seals is calculated using the following formula: in, Oil film thickness; This refers to the local oil film thickness. Indicates circumferential position; Indicates axial position; Indicates oil film pressure; Indicates the pressure flow influence coefficient; This represents the roughness influence coefficient; Indicates the cavitation index; Indicates dimensionless velocity; Indicates the diameter of the rod.

10. The method for determining leakage in a series sealing system for reciprocating moving parts of an aircraft according to claim 9, characterized in that: In step S11, comparing the inner and outer stroke flow rates of the two combined seals to draw a conclusion on leakage of the series sealing system includes: if the inner stroke flow rate is greater than or equal to the outer stroke flow rate, the series sealing system is considered to be non-leaking; if the inner stroke flow rate is less than the outer stroke flow rate, the series sealing system is considered to be leaking.

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