| Butterfly check valve has the characteristics of simple structure,good buffering performance,stable operation and so on.It is widely used in industrial water supply,sewage treatment plant and other fields.It can not only effectively prevent the internal medium back flow of the pipeline,but also limit the damage of the water hammer to the pipeline,so as to ensure the safety of the use of fluid machinery equipment.Due to the influence of turbulence,the flow field inside the check valve is complicated.If the traditional experimental measurement is adopted as the research method to evaluate the comprehensive performance of the valve,it has the disadvantages of high cost,long test period and many uncontrollable variables,and it is difficult to obtain accurate flow field distribution.The development of computational fluid dynamics and numerical simulation technology provides new ideas and methods for valve research and development.Through numerical simulation,it can simulate calculation under various ideal conditions to observe the flow state of the internal medium of the check valve and the force of the valve disc.In this paper,the flow field characteristics and fluid-structure coupling characteristics of butterfly check valve are studied by numerical simulation method,which provides numerical tools for structural optimization design of butterfly check valve.The main research contents are as follows:(1)CFD method(Computational Fluid Dynamics)is adopted to compute the internal flow field of DN400 three-dimensional butterfly check valve under 18 degrees of openness by combining the basic fluid governing equation,turbulent kinetic energy and turbulent dissipation rate equation.Analyze the pressure,velocity and velocity vector field variation when the medium flows inside the valve.According to the simulation results,the flow rate,flow resistance coefficient and hydrodynamic moment coefficient of butterfly check valve were calculated by using the empirical formula,and the flow resistance characteristic curve,flow characteristic curve and hydrodynamic moment coefficient characteristic curve of butterfly check valve were drawn to analyze the flow performance of the valve.Through the results obtained,it is found that the energy consumption of the flow field inside the valve with different opening degrees is high and the vortex structure is easy to be generated.(2)Considering the dynamic opening process of the check valve,the bidirectional fluid-structure coupling simulation of the mechanical properties of the valve was carried out based on the dynamic grid technology combined with turbulence equation,solid governing equation and dynamic equation,and the characteristic changes of hydrodynamic torque and heavy torque under different working conditions were analyzed.The opening of the valve during normal operation was obtained by the torque balance method.This method is helpful to evaluate the flow resistance of engineering products and provide certain data support for the selection of pump.(3)In view of the vortex phenomenon in the middle stream of the pipeline near the check valve flap area with relatively small opening,the flap shape was optimized,and the fluid calculation domain under different opening conditions was established by ANSYS Workbench module for numerical simulation.The changes of pressure field,velocity field,velocity vector field,flow resistance and flow characteristic curve before and after the structure improvement are compared and analyzed.The optimized check valve has a small flow resistance coefficient.Then,the interaction module of Fluent and Static Structural data was used to simulate the unidirectional fluid-structure coupling of the valve under different openings,and the mechanical properties of the valve before and after improvement were compared and analyzed.This method can provide reference for reducing flow resistance and strength checking in butterfly check valve design. |
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