A numerical simulation method for the dynamics of a three-way spring valve core considering the inlet pipeline

Abstract

The purpose of the present invention is to provide a research method for numerical simulation of the spool dynamics of a three-way spring valve taking into account the inlet pipeline, comprising the following steps: pre-processing of complex valve numerical simulation, numerical iterative calculation, repeating the above two steps to obtain formulas for different working conditions, valve openings, and fluid forces acting on the spool; substituting the spool force formula into the spool dynamics equation and coupling it with the pipeline wave equation to complete the establishment of a pipe-valve coupling model; based on the pipe-valve coupling model, completing the numerical simulation of the spool dynamics of a three-way spring valve taking into account the inlet pipeline under all working conditions through numerical calculation. The present invention proposes an accurate, reasonable, and efficient numerical simulation method for studying the dynamic performance of the spool under the coupling of a spring valve and a pipeline, breaking through the limitations of traditional research methods based on experimental testing and CFD calculation performance, and providing technical support for the design and production of valves and the configuration, selection, and design of pipe-valve devices in power plants.

Description

Technical Field

[0001] The present invention relates to a pump-valve-pipeline simulation method, in particular to a valve core dynamic response simulation method. Background Art

[0002] In modern factories, control valves are very common pipeline components that play an important role in fluid transportation. They are actuators and terminal components in the process control industry and are widely used in large oil pipelines, chemical industry, shipbuilding, aviation, power stations and other fields.

[0003] Valves, as important control components in piping systems, can be used to regulate the flow and pressure of media in the pipeline, or to cut off or open the flow medium passage. A spring check valve is one of many valves whose main function is to cut off the backflow of the medium. Spring check valves play an important role in piping systems. Their ability to cut off backflow and regulate flow distribution is crucial for the smooth operation of the piping system. However, during actual piping system operation, the spool of a spring-controlled valve can become unstable, causing continuous oscillation of the piping system. During factory testing, spring-controlled valves meet the requirements for single-valve hydraulic performance and structural vibration indicators. Therefore, previous studies on the dynamic characteristics of a single device were unable to predict the actual response of the valve in the piping system. It was necessary to consider coupling the actual piping system and the valve for research, which is difficult to achieve during factory testing.

[0004] Typically, a piping system includes components such as pumps, valves, and pipelines, all of which work together to ensure the safe, stable, and economical operation of the entire equipment. Common methods for studying piping systems include theory, experimentation, and CFD simulation. Theoretical research often focuses on simple valve body models. The main reason is that for complex valve body structures, it is difficult to directly determine the valve's flow relationship and the valve core force formula. Experimentation is currently an important means of studying the stability of piping systems. Existing experimental methods are as follows: drilling the valve body and reprocessing the valve core to obtain test data on the valve core's vibration response. This test data is then used to optimize the system design, and this process is repeated to ultimately obtain a design solution that meets the requirements. Although experimentation is the most effective research method, the drilling process is cumbersome, and the repeated cycles of machining, experimentation, and reprocessing consume a lot of manpower and material resources. Furthermore, drilling tests are not possible in some special cases. As CFD technology matures, it can be used to understand the flow characteristics within flow-passing components. However, it should be emphasized that although CFD is a state-of-the-art tool for describing fluid flow, it is not designed for transient simulation calculations of the entire operating condition of a piping system. The main reason is that the vibration of the valve core in the valve changes the fluid domain, requiring mesh reconstruction. In addition, the flow rate within the valve fluctuates dramatically, requiring high mesh size. For pipelines, capturing the acoustic field within the pipe also requires high mesh quality. With current computing power, completing system-level transient analysis of the entire operating condition is almost impossible. Summary of the Invention

[0005] The purpose of the present invention is to provide a three-way spring valve core dynamics numerical simulation research method considering the inlet pipeline, which provides technical support for the design and production of valves and the pipe-valve configuration, selection and design in power devices.

[0006] The object of the present invention is achieved like this:

[0007] The present invention provides a method for numerical simulation of the dynamics of a three-way spring valve core taking into account an inlet pipeline, which is characterized by:

[0008] (1) Pre-processing of complex valve numerical simulation, including 3D modeling of spring check valve, flow field extraction, flow field meshing, turbulence model, selection of near-wall function and mesh independence verification;

[0009] (2) Numerical iterative calculation, setting the boundary conditions of the flow field numerical simulation, numerical simulation of the steady flow field, obtaining the flow coefficient and the fluid force on the valve core;

[0010] (3) Repeat the above two steps to obtain different working conditions Q in / p out , valve opening and the fluid force F on the valve core fluid (x,Q in ,p out)formula;

[0011] (4) Substitute the valve core force formula into the valve core dynamic equation and couple it with the pipeline wave equation to complete the establishment of the pipe-valve coupling model;

[0012] (5) Based on the pipe-valve coupling model, numerical simulation of the valve core dynamics of the three-way spring valve in the inlet pipeline under all working conditions is completed through numerical calculation.

[0013] The present invention may also include:

[0014] 1. In step (2), select the boundary conditions of flow inlet and pressure outlet, and set the inlet flow rate to Q in , main outlet pressure p out , the air outlet is directly discharged to the outside, the pressure is 1 standard atmospheric pressure, that is, p out2 =1bar, through numerical simulation, the main outlet flow coefficient C of the valve opening and working conditions is obtained d1 、Empty outlet C d2 And the fluid force F on the valve core fluid .

[0015] 2. In step (4),

[0016] For the pipeline part, the flow field distribution inside the pipeline is determined according to the wave equation. The wave equation is shown as follows. The characteristic line method is used to process the wave equation:

[0017]

[0018]

[0019] Where p is the pressure in the pipe, Q is the pressure volume flow rate in the pipe, x is the coordinate along the axial direction of the pipe, t is the time, ρ is the density of the fluid medium in the pipe, A is the cross-sectional area of ​​the pipe, and a is the sound velocity of the fluid. K is the bulk elastic modulus of the fluid, represents the flow friction resistance term, f is the Darcy friction coefficient, D is the pipe diameter;

[0020] L1+λL2 gives:

[0021]

[0022] when When The above formula is derived as follows:

[0023]

[0024]

[0025] Divide the pipe of length L into N segments, each segment is The design time step is Divide the grid in this way, and the diagonal of each small grid is a characteristic line. For the above two characteristic line equations and respectively in C + and C - Integrate the friction resistance term and take the trapezoidal quadrature on the time axis:

[0026]

[0027]

[0028] Let p A and Q A It is known that for C + , p P and Q P Use p A and Q A Indicates that for C - , use p B and Q B Indicates p P and Q P , combining the above two equations, we can solve for p P and Q P The friction resistance term f(Q) at a segment point i on the characteristic grid represents the friction resistance generated by the pipe segment with the point as the midpoint and the length of each segment as the length, which can be expressed as:

[0029]

[0030] For the boundary, assuming that the pipeline inlet is the flow boundary Q0 of the pump, combined with formula C - : The physical quantity of the system port can be determined; for the pipeline outlet, the following formula can be used: valve flow formula and characteristic line formula Determine the physical quantities of the pipeline outlet boundary.

[0031]

[0032] Where C d1 、C d2 Respectively represent the flow coefficient of the valve main outlet and the empty outlet, A g1 、A g2 Respectively represent the flow area of ​​the valve main outlet and the empty outlet, p N Indicates the valve inlet pressure, that is, the pipeline outlet pressure;

[0033] For the valve part, step (3) F fluid (x,Q in ,pout ) in That is the pipeline outlet Q N , the valve core dynamic equation is:

[0034]

[0035] Combined with collision theory, the valve core dynamic equation is transformed into differential form:

[0036]

[0037]

[0038] v + =R(v - )=-rv -

[0039] Where m includes the total mass of the valve core and the equivalent spring, k is the system damping, s is the spring stiffness, and x0 is the spring pre-compression. When the valve core collides with the valve seat or the maximum opening limit of the valve, energy loss will occur. r represents the collision loss coefficient.

[0040] Select the fourth-order Runge-Kutta method for the formula v + =R(v - )=-rv - Perform calculations.

[0041] The advantages of this invention lie in its provision of an accurate, rational, and efficient numerical simulation method for studying the dynamic performance of spring-loaded valve cores coupled to pipelines. This method overcomes the limitations of traditional experimental methods and CFD calculations. This method can be used to study the dynamic performance of complex spring-loaded valve cores under all operating conditions in a pipeline system, providing technical support for valve design and production, as well as for the configuration, selection, and design of pipe-valve systems in power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the piping system of the present invention;

[0043] Figure 2 is a flow chart of the present invention;

[0044] Figure 3a Schematic diagram of pipeline grid division (characteristic line grid) of the present invention, Figure 3b Schematic diagram of pipeline grid division (characteristic lines on the boundary) of the present invention;

[0045] Figure 4a It is a schematic diagram of the three-dimensional structure of the spring valve. Figure 4b Schematic diagram of valve core, valve stem and empty outlet;

[0046] Figure 5 This is a schematic diagram of the force applied to the valve core of the spring valve of the present invention. DETAILED DESCRIPTION

[0047] The present invention will be described in more detail below with reference to the accompanying drawings:

[0048] Combine Figure 1-5 , the present invention takes a three-way check valve as an example to introduce a research method for the numerical simulation of the valve core dynamics of a complex valve-pipeline coupling system. First of all, the spring valve includes an inlet, a main outlet, an empty outlet, a valve core, a valve stem, a throttling sleeve and other components. It is an asymmetric three-way valve; the valve core is an important component in the spring check valve, and the spring valve's backflow cut-off and flow distribution functions are both realized by the valve core. When the inlet pressure is less than the valve core trigger pressure, the valve core does not move under the action of the spring elastic force, and the valve is in a closed state; when the inlet pressure is greater than its trigger pressure, the valve core moves upward due to the upward combined force, and the valve enters the opening process until it reaches stability. Under rated working conditions, all water is discharged from the main outlet, and the empty outlet is equivalent to being blocked, which is no different from a conventional two-way valve at this time; this valve is mainly designed for non-rated working conditions to facilitate the adjustment of variable working conditions of the water supply pipeline system. Under non-rated operating conditions, water is discharged simultaneously from the main outlet and the drain port. At this time, the spring check valve is not fully open, and the valve core is suspended in an unstable state within the spring check valve. Under these conditions, the movement of the valve core and the flow within the valve are complex, and at certain flow rates, abnormal vibration of the spring check valve-pipeline system may occur. Therefore, to mitigate the impact of the unstable equilibrium state of the valve core on the hydraulic performance and vibration characteristics of the system, it is necessary to measure or estimate the system. Therefore, studying the dynamic performance of the spring check valve core in the piping system is of great significance to the safe and reliable operation of the piping system and can also provide technical support for the configuration, selection, and design of pipes and valves in power plants.

[0049] The present invention specifically comprises the following steps:

[0050] Step 1: Pre-processing of complex valve numerical simulation (three-dimensional modeling of spring check valve, flow field extraction, flow field meshing, turbulence model, selection of near-wall function and mesh independence verification).

[0051] The meshing of the flow field during pre-processing significantly impacts the convergence and accuracy of subsequent numerical simulations. The densification of the mesh near the wall during meshing also significantly impacts the simulation of the flow near the wall. This paper considers the varying requirements for the first-layer mesh height for different turbulence models and near-wall functions, and densifies the mesh near the wall boundary layer based on the parameters selected for the numerical simulation.

[0052] Step 2: numerical iterative calculation (setting boundary conditions for flow field numerical simulation, numerical simulation of steady flow field, obtaining flow coefficient and fluid force on valve core);

[0053] In numerical iterative calculation, boundary condition setting is very important, and the inlet and outlet boundary conditions must conform to engineering practice. The present invention selects the boundary conditions of flow inlet and pressure outlet, and sets the inlet flow as Q in , main outlet pressure p out , the air outlet is directly discharged to the outside, so the pressure is 1 standard atmospheric pressure, that is, p out2 =1bar. Through numerical simulation, the valve opening and the main outlet flow coefficient C under the working condition are obtained. d1 、Empty outlet C d2 And the fluid force F on the valve core fluid .

[0054] Step 3: Repeat the above two steps to obtain different working conditions (Q in / p out ), valve opening (valve flow coefficient under x) and valve core force, the flow coefficient C is obtained by data fitting d1 (x,Q in ,p out ), C d2 (x,Q in ,p out ) and the fluid force F acting on the valve core fluid (x,Q in ,p out )formula.

[0055] Step 4: Substitute the valve core force formula into the valve core dynamic equation and couple it with the pipeline wave equation to complete the establishment of the pipe-valve coupling model.

[0056] First, for the pipeline, the flow field distribution inside the pipeline can be determined based on the wave equation. The wave equation is shown in formula (1). To facilitate numerical calculations, the characteristic line method is used to process the wave equation.

[0057]

[0058] Where p is the pressure in the pipe, Q is the pressure volume flow rate in the pipe, x is the coordinate along the axial direction of the pipe, t is the time, ρ is the density of the fluid medium in the pipe, A is the cross-sectional area of ​​the pipe, and a is the sound velocity of the fluid. K is the bulk elastic modulus of the fluid, represents the flow friction resistance term, f is the Darcy friction coefficient, and D is the pipe diameter.

[0059] L1+λL2 gives:

[0060]

[0061] when When Formula (2) can be derived as follows:

[0062]

[0063]

[0064] Divide the pipe of length L into N segments, each segment is The design time step is As shown in Figure 3(a), when the grid is divided in this way, the diagonal of each small grid is a characteristic line. + and C - Integrate the friction resistance term and take the trapezoidal quadrature on the time axis:

[0065]

[0066] Let p A and Q A It is known that for C + , p P and Q P Use p A and Q A Similarly, for C - , available p B and Q B Indicates p P and Q P Solving the simultaneous equations (5) and (6) yields p P and Q P The friction resistance term f(Q) at a segment point i on the characteristic grid represents the friction resistance generated by the pipe segment with the point as the midpoint and the length of each segment as the length, which can be expressed as:

[0067]

[0068] For the boundary, as shown in Figure 3(b), assuming that the left boundary (inlet) of the pipeline is the flow boundary Q0 of the pump, combined with formula (6), the physical quantity of the system port can be determined; and for the right boundary (outlet) of the pipeline, the physical quantity of the pipeline outlet boundary can be determined according to the valve flow formula (formula (8)) and the characteristic line formula (5).

[0069]

[0070] Where C d1 、C d2 Respectively represent the flow coefficients of the valve main outlet and the empty outlet, which have been obtained in the first three steps. g1 、A g2 They represent the flow area of ​​the valve main outlet and the empty outlet respectively, which is related to the valve opening x, p NIndicates the valve inlet pressure, that is, the pipeline outlet pressure.

[0071] For the valve part, the most important thing is to analyze the force on the valve core. The relationship between the fluid force on the valve core and the valve opening and the valve inlet and outlet boundaries has been obtained from step three. It should be emphasized here that the valve inlet boundary condition should be consistent with the pipeline outlet, that is, step three F fluid (x,Q in ,p out ) in That is the pipeline outlet Q N The dynamic equation of the valve core is:

[0072]

[0073] Combined with collision theory, the valve core dynamic equation is transformed into differential form:

[0074]

[0075] Where m includes the total mass of the valve core and equivalent spring, k is the system damping, s is the spring stiffness, and x0 is the spring precompression. When the valve core collides with the valve seat or the maximum valve opening limit, energy loss occurs, and r represents the collision loss coefficient.

[0076] In order to ensure the accuracy of the numerical calculation, the fourth-order Runge-Kutta method is selected to calculate formula (10).

[0077] Step 5: Based on the pipe-valve coupling model, complete the dynamic numerical simulation of the three-way spring valve core of the inlet pipeline under all working conditions through numerical calculation.

Claims

1. A method for numerical simulation of the spool dynamics of a three-way spring-loaded valve considering the inlet pipeline, characterized by: (1) Pre-processing of complex valve numerical simulation, including 3D modeling of spring check valve, flow field extraction, flow field meshing, turbulence model, selection of near-wall function and mesh independence verification; (2) Numerical iterative calculation, setting the boundary conditions of the flow field numerical simulation, numerical simulation of the steady flow field, obtaining the valve flow coefficient and the fluid force on the valve core; Set the inlet flow rate Q in , Main outlet pressure P out , the air outlet is directly discharged to the outside, the pressure is 1 standard atmosphere, that is, P out2 =1bar; Through numerical simulation, the valve flow coefficient and the fluid force on the valve core under the valve opening x are obtained; (3) Repeat the above two steps to obtain different working conditions Q in / P out , the valve flow coefficient under the valve opening x and the fluid force on the valve core, and the flow coefficient C is obtained by data fitting d1 (x,Q in ,p out ), C d2 (x,Q in ,p out ) and the fluid force F acting on the valve core fluid (x,Q in ,p out )formula; (4) The fluid force F on the valve core fluid (x,Q in ,p out ) formula is substituted into the valve core dynamic equation and coupled with the pipeline wave equation to complete the establishment of the pipe-valve coupling model; For the pipeline part, the flow field distribution inside the pipeline is determined according to the wave equation. The characteristic line method is used to process the wave equation. The wave equation is: Where p is the pressure in the pipe; Q is the pressure volume flow rate in the pipe; x is the coordinate along the pipe axis; t is the time; ρ is the density of the fluid medium in the pipe; A is the cross-sectional area of ​​the pipe; a is the sound velocity of the fluid; K is the bulk elastic modulus of the fluid; represents the flow friction resistance term, f is the Darcy friction coefficient, D is the pipe diameter; L1+λL2 gives: when When The above formula is derived as follows: Divide the pipe of length L into N segments, each segment is The design time step is Divide the grid, and the diagonal of each small grid is the characteristic line. The two characteristic line equations are respectively in C + and C - Integrate the friction resistance term and take the trapezoidal quadrature on the time axis: Among them, p A and Q A It is known that for C + , p P and Q P Use p A and Q A Indicates; for C - , use p B and Q B Indicates p P and Q P , combining the above two equations, we can solve for p P and Q P ; The friction resistance term f(Q) at a segment point i on the characteristic grid represents the friction resistance generated by the pipe segment with the point as the midpoint and the length of each segment as the length, which can be expressed as: For the boundary, assuming that the pipeline inlet is the flow boundary Q0 of the pump, combined with formula C - : Determine the physical quantity of the system port; for the pipeline outlet, according to the following formula, valve flow formula and characteristic line formula C + : Determine the physical quantities of the pipeline outlet boundary; Where C d1 、C d2 Respectively represent the flow coefficient of the valve main outlet and the empty outlet; A g1 、A g2 Respectively represent the flow area of ​​the valve main outlet and the empty outlet; p N Indicates the valve inlet pressure, that is, the pipeline outlet pressure; For the valve part, F fluid (x,Q in ,p out ) in That is the pipeline outlet Q N , the valve core dynamic equation is: Combining the collision theory, the valve core dynamic equation is transformed into differential form: v + =R(v - )=-rv - Where m includes the total mass of the valve core and the equivalent spring; k is the system damping; s is the spring stiffness; x0 is the spring pre-compression; when the valve core collides with the valve seat or the maximum valve opening limit, energy loss will occur, and r represents the collision loss coefficient. The fourth-order Runge-Kutta method is used to calculate the differential form of the valve core dynamic equation; (5) Based on the pipe-valve coupling model, numerical simulation of the valve core dynamics of the three-way spring valve considering the inlet pipeline under all working conditions is completed through numerical calculation.

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