Calculation method for radial eccentric wear force of cylinder wall of air cylinder in movement process

Abstract

The invention provides a method for calculating radial eccentric wear force of a cylinder wall in a motion process, which comprises the following steps of: 1, analyzing the stress of a valve core, establishing a motion equation, and solving displacement x; 2, a 1D calculation model is established, and valve element movement, friction force and spring force are simulated; differentiating the differential displacement data x (t) to obtain the speed v (t) of the valve core, and fitting the speed v (t) into a one-element cubic equation; 3, establishing a CFD model, initializing a flow field, and setting a medium and a solver; 4, defining load and boundary conditions, and extracting radial force data; applying the fitted velocity equation v (t) to the dynamic grid through UDF; a safety valve element is simplified into a single-degree-of-freedom spring mass system, a force balance equation is established, the dynamic relation between hydraulic pressure and valve element displacement is directly coupled, acceleration sudden change and fluid dynamic response at the moment of opening of the valve element can be accurately captured, and the problem of stress analysis deviation caused by neglecting of the dynamic effect in a traditional method is solved.

Description

Technical Field

[0001] The present invention relates to a method for calculating the radial eccentric wear force of a cylinder wall during movement, and particularly relates to the technical field of radial wear force. Background Art

[0002] In mechanical equipment and industrial systems, the radial eccentric wear force of a cylinder wall is one of the important factors affecting the performance and lifespan of the equipment. During the operation of the cylinder, due to the movement of the valve core and the dynamic action of the fluid, the cylinder wall will be subjected to uneven radial forces, resulting in eccentric wear. This phenomenon not only reduces the sealing performance of the cylinder but may also cause equipment failures and increase maintenance costs. Therefore, accurately calculating the radial eccentric wear force of the cylinder wall is of great significance for optimizing the cylinder design and improving equipment reliability.

[0003] Traditional methods usually simplify the force analysis of the cylinder wall as a static or quasi-static problem, ignoring the dynamic effects during the movement of the valve core. For complex pneumatic valve systems, this simplified method is difficult to accurately reflect the force conditions under actual working conditions.

[0004] Existing 1D calculation models are mostly used in the preliminary design stage and cannot accurately simulate non-linear factors such as friction force and spring force during the movement of the valve core. These models usually rely on empirical formulas and lack a detailed description of the actual physical process.

[0005] To reduce the calculation complexity, the model is usually simplified to a local two-dimensional or three-dimensional model, which cannot comprehensively reflect the actual working conditions. The simulation calculation efficiency of complex models is low, and the debugging time is long, making it difficult to meet the engineering requirements. Summary of the Invention

[0006] Object of the Invention: To propose a method for calculating the radial eccentric wear force of a cylinder wall during movement to solve the above problems existing in the prior art.

[0007] Technical Solution: A method for calculating the radial eccentric wear force of a cylinder wall during movement, comprising:

[0008] Step 1: Analyze the force on the valve core, establish the motion equation, and solve for the displacement x.

[0009] Step 2: Establish a 1D calculation model to simulate the movement of the valve core, friction force, and spring force; differentiate the differential displacement data x(t) to obtain the velocity v(t) of the valve core, and fit it into a cubic equation of one variable.

[0010] Step 3: Establish a CFD model, initialize the flow field, and set the medium and solver.

[0011] Step 4: Define the load and boundary conditions, and extract the radial force data; apply the fitted velocity equation v(t) to the dynamic mesh through UDF.

[0012] In a further embodiment, Step 1: Force analysis of the pneumatic valve spool,

[0013] Simplify the safety valve spool into a single-degree-of-freedom spring-mass system. Taking the piston as the research object, establish a force balance equation. The specific equation is:

[0014]

[0015] In the formula, F is the external load received by the piston, generated by the hydraulic pressure of the brake fluid; m is the mass of the spool, is the acceleration of the spool, x is the displacement of the spool, and k is the stiffness of the safety valve spool spring;

[0016] Safety valve spool opening condition: The safety valve is initially closed and opens when the air pressure reaches a certain threshold. The hydraulic pressure F is related to the opening of the valve port, and the opening action of the spool needs to be calculated through a separate spool model.

[0017] In a further embodiment, Step 2: Establish a 1D calculation model of the pneumatic valve:

[0018] Adopt the PANO042 spool model and set the size of the liquid outlet of the safety valve spool;

[0019] Use the MECMAS21 mass limit model; adjust the limit of the spool movement displacement,

[0020] Use PNAFS02 to simulate the cup friction in the movement of the safety valve spool;

[0021] Use SD0000A to express the spring force received by the safety valve spool;

[0022] By solving the spool movement equation ( in Step 1), obtain the displacement x of the spool, differentiate the displacement x with respect to time t to get the spool velocity

[0023] Fit the velocity data v(t) into a cubic equation of one variable, in the form of:

[0024] v(t)=at 3 +bt 2 +ct + d

[0025] where a, b, c, and d are fitting coefficients.

[0026] In a further embodiment, Step 3: Establish a CFD model of the valve spool

[0027] CFD model initialization: Set the exhaust pressure of the safety valve to 17 bar, the pressure difference between the inlet and outlet to 17 bar, and calculate the flow velocity and pressure distribution under the steady-state flow field;

[0028] Medium and solver: Set the gas inside the safety valve as ideal gas, use the couple solver and the kw-sst turbulence model;

[0029] Calculation of transient flow field: Use dynamic mesh to simulate the movement of the valve core. Assume the minimum size of the mesh is L and the maximum axial speed of the valve core is v, then the time step does not exceed L / v.

[0030] In a further embodiment, Step 4: Definition of load and boundary conditions:

[0031] Radial force output: In the CFD software, extract the force received by the wall of the valve core; Assume the axial direction is Z, and extract the forces of the valve core in the X and Y directions;

[0032] Boundary: Set the inlet pressure to 17 bar, the outlet to 0 bar, and determine the operating pressure of the ideal gas to be 0 bar;

[0033] Application of valve core speed: Take the cubic equation of one variable v(t)=at 3 +bt 2 +ct + d obtained by fitting in Step 2 as the input, and use udf_define_cg_moiton in fluent to apply the speed of the valve core to the rigid body moving wall surface in the dynamic mesh.

[0034] Beneficial effects: The present invention proposes a calculation method for the radial eccentric wear force of the cylinder wall during the movement process. By simplifying the safety valve core into a single-degree-of-freedom spring-mass system, establishing a force balance equation, and directly coupling the dynamic relationship between the hydraulic pressure and the valve core displacement, it can accurately capture the acceleration mutation at the moment of valve core opening and the fluid dynamic response, and solve the problem of deviation in force analysis caused by traditional methods ignoring dynamic effects;

[0035] By fitting the velocity from the differential displacement data to form a cubic equation, the dynamic coupling of the friction force and the spring force is realized. Through physically driven parametric modeling, the prediction accuracy of the non-linear force is significantly improved; The couple solver, combined with the ideal gas state equation, initializes the steady-state flow field under a 17 bar pressure difference condition, providing accurate initial conditions for transient simulation;

[0036] Apply the fitted velocity equation to the dynamic mesh boundary through Fluent UDF to realize the real-time bidirectional coupling of the valve core movement and the flow field, avoiding the limitations of the preset movement law of the traditional dynamic mesh, and enabling dynamic adjustment of the mesh deformation strategy; Through the 1D-CFD joint simulation framework, realize the cross-scale coupling of system-level dynamics and local flow field details. The 1D model quickly calculates the movement trajectory of the valve core, and the CFD model focuses on the high-frequency components of the radial force on the cylinder wall. Description of the drawings

[0037] Figure 1 Schematic diagram of the eccentric wear calculation model of the present invention. Specific implementation mode

[0038] The applicant believes that at present, most of the simulation methods for rubber sealing rings are simulation calculation methods based on implicit dynamics. Due to the difficult convergence characteristic of the implicit solution method, the simulation model is generally simplified into a local two-dimensional or three-dimensional model. For the rubber seal simulation that needs to consider the actual complex model under complex working conditions, either the calculation efficiency is low, the debugging time is long, or the calculation is difficult to converge.

[0039] To solve the problems existing in the prior art, the present invention provides a calculation method for the radial eccentric wear force of the cylinder wall during movement, which improves the accuracy and efficiency of the calculation of the radial eccentric wear force of the cylinder wall and is applicable to the simulation analysis under complex working conditions.

[0040] The following is a further specific description of the solution through embodiments and in conjunction with the drawings.

[0041] In this application, we propose a calculation method for the radial eccentric wear force of the cylinder wall during movement, including the following steps:

[0042] Step 1: Analyze the force on the valve core, establish the motion equation, and solve for the displacement x; Analyze the force on the valve core of the pneumatic valve. Taking the valve core of the safety valve as the research object, consider its force situation.

[0043] Simplify the safety valve core into a single-degree-of-freedom spring-mass system, and ignore the damping brought by the brake fluid lubrication.

[0044] Taking the piston as the research object, establish the force balance equation, and the specific equation is:

[0045]

[0046] In the formula, F is the external load received by the piston, generated by the hydraulic pressure of the brake fluid; m is the mass of the valve core. is the acceleration of the valve core, x is the displacement of the valve core, and k is the stiffness of the safety valve core spring.

[0047] Safety valve core opening condition: The safety valve is initially closed and opens when the air pressure reaches a certain threshold. The liquid pressure F is related to the opening of the valve port, and the opening action of the valve core needs to be calculated through a separate valve core model.

[0048] Step 2: Establish a 1D calculation model to simulate the movement, friction force, and spring force of the valve core; Differentiate the differential displacement data x(t) to obtain the velocity v(t) of the valve core, and fit it into a cubic equation; Establish a 1D calculation model of the pneumatic valve:

[0049] Adopt the PANO042 valve core model and set the size of the liquid outlet of the safety valve core;

[0050] Use the MECMAS21 mass limit model; adjust the limit of the valve core movement displacement,

[0051] Use PNAFS02 to simulate the friction force of the leather cup during the movement of the safety valve core;

[0052] Use SD0000A to express the spring force received by the safety valve core;

[0053] By solving the movement equation of the valve core (in step one ), obtain the displacement x of the valve core, differentiate the displacement x with respect to time t to get the velocity of the valve core

[0054] Fit the velocity data v(t) into a cubic equation of one variable, in the form of:

[0055] v(t) = at 3 + bt 2 + ct + d

[0056] where a, b, c, and d are fitting coefficients.

[0057] Step 3: Establish a CFD model, initialize the flow field and set the medium and solver; establish a CFD model of the valve core of the valve

[0058] CFD model initialization: Set the exhaust pressure of the safety valve to 17 bar, the pressure difference between the inlet and outlet to 17 bar, and calculate the flow velocity and pressure distribution under the steady-state flow field;

[0059] Medium and solver: Set the gas inside the safety valve as an ideal gas, use the couple solver and the kw-sst turbulence model;

[0060] Calculation of the transient flow field: Use dynamic meshing to simulate the movement of the valve core. Assume that the minimum size of the mesh is L and the maximum axial velocity of the valve core is v, then the time step does not exceed L / v.

[0061] Step 4: Define the load and boundary conditions, and extract the radial force data; apply the fitted velocity equation v(t) to the dynamic mesh through UDF; Definition of load and boundary conditions:

[0062] Radial force output: Use the CFD software (such as Fluent) to extract the force received by the valve core wall; assume the axial direction is Z and extract the forces of the valve core in the X and Y directions;

[0063] Boundary: Set the inlet pressure to 17 bar, the outlet to 0 bar, and determine the operating pressure of the ideal gas to be 0 bar;

[0064] Spool velocity application: Take the cubic equation of one variable v(t)=at 3 +bt 2 +ct + d obtained by fitting in step 2 as the input, and use the udfdefine_cg_moiton (user-defined function) in fluent to apply the velocity of the spool to the rigid body moving wall surface in the dynamic mesh.

[0065] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as a limitation of the present invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the present invention defined by the appended claims.

Claims

1. A calculation method for the radial eccentric wear force of the cylinder wall during the movement process, characterized in that Including: Step 1: Analyze the forces acting on the valve core, establish the motion equation, and solve for the displacement x. Step 2: Establish a 1D calculation model to simulate the valve core movement, frictional force, and spring force; differentiate the differential displacement data x(t) to obtain the velocity v(t) of the valve core, and fit it into a cubic equation of one variable. Step 3: Establish a CFD model, initialize the flow field, and set the medium and solver. Step 4: Define the loads and boundary conditions, and extract the radial force data; apply the fitted velocity equation v(t) to the dynamic mesh through UDF.

2. The calculation method of the radial eccentric wear force of the cylinder wall during the movement according to claim 1, wherein, Step 1: Force analysis of the pneumatic valve core Simplify the safety valve core into a single-degree-of-freedom spring-mass system, take the piston as the research object, and establish the force balance equation. The specific equation is: where F is the external load on the piston, generated by the hydraulic pressure of the brake fluid; m is the mass of the spool valve, is the acceleration of the spool valve, x is the displacement of the spool valve, and k is the stiffness of the spring of the safety valve spool Opening condition of the safety valve core: The safety valve is initially closed and opens when the air pressure reaches a certain threshold. The liquid pressure F is related to the opening of the valve port, and the opening action of the valve core needs to be calculated through a separate valve core model.

3. The calculation method of the radial eccentric wear force of the cylinder wall during movement according to claim 1, characterized in that, Step 2: Establish a 1D calculation model of the pneumatic valve Adopt the PANO042 valve core model and set the size of the liquid outlet of the safety valve core. Use the MECMAS21 mass limit model; adjust the limit of the valve core movement displacement. Use PNAFS02 to simulate the cup leather friction force during the movement of the safety valve core. Use SD0000A to express the spring force received by the safety valve core. By solving the motion equation of the spool valve ( in step 1), the displacement x of the spool valve is obtained, and the displacement x is differentiated with respect to time t to obtain the velocity of the spool valve Fit the velocity data v(t) into a cubic equation of one variable, in the form of: v(t) = at 3 + bt 2 + ct + d where a, b, c, and d are fitting coefficients.

4. The calculation method of the radial eccentric wear force of the cylinder wall during movement according to claim 1, characterized in that Step 3: Establish a CFD model of the valve core CFD model initialization: Set the exhaust pressure of the safety valve to 17 bar, the pressure difference between the inlet and outlet to 17 bar, and calculate the flow velocity and pressure distribution under the steady-state flow field. Medium and solver: Set the gas inside the safety valve as an ideal gas, use the couple solver, and the kw-sst turbulence model. Calculation of the transient flow field: Use the dynamic mesh to simulate the valve core movement. Assume that the minimum size of the mesh is L and the maximum axial velocity of the valve core is v, then the time step does not exceed L / v.

5. The calculation method of the radial eccentric wear force of the cylinder wall during movement according to claim 1, wherein Step 4: Definition of loads and boundary conditions Radial force output: Use the CFD software to extract the force received by the valve core wall; assume the axial direction is Z, and extract the forces of the valve core along the X and Y directions. Boundary: Set the inlet pressure to 17 bar, the outlet to 0 bar, and determine the operating pressure of the ideal gas to be 0 bar. Spool velocity application: Use the cubic equation of one variable v(t)=at 3 +bt 2 +ct + d obtained by fitting in step 2 as the input, and use udf_define_cg_motion in Fluent to apply the spool velocity to the rigid body moving wall surface in the dynamic mesh.

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