Analysis Of The Static And Dynamic Characteristics On The Pilot-cage Type Control Valve

Control valve is widely used in industrial automation process,its static and dynamic properties determine the performance of the whole control system.The vibration of control valves in the working process often causes safety accidents causing concern.In this paper,the static and dynamic characteristics of control valves are analyzed by the computational fluid dynamics(CFD).The main research work is as follows.Firstly,the dynamic models of pilot-cage type valve core-stem are established.According to the working principle of control valve and valve core structure,the main force of the valve core and pilot-cage type valve core are analyzed.According to the working principle of the valve locater,the function relation between the pneumatic control force and the valve core displacement is deduced;Two degree of freedom the valve stem vibration system mathematical model is established considering the locator role of valve core.Secondly,the finite element models of the flow field in the process of pilot-cage type valve are established and the solving method about the motion of the valve core of fluid-structure coupling is given.The Solidworks geometry entity model about the flow field in the valve is meshed by the CFD module FLUID142 unit in the ANSYS;According to the import and export pressure differential motion state and the control valve core,boundary conditions are set.According to the core-stem vibration system mathematical model,the forecast-correction algorithm based on Newmark numerical method of APDL,translation process is written,which can solve the motion equation of valve core.Finally,the static and dynamic characteristics of pilot-cage type valve are analyzed in the simulation.The steady state flow field distribution and fluid unbalanced force are obtained in the condition of different opening and differential pressure of valve core in stationary and uniform motion.The effect of differential pressure on vibration displacement and dynamic fluid unbalanced force is analyzed under the opening of the fixed and variable working conditions.Simulation found that unbalanced fluid force and the valve core vibration displacement are affected significantly at import and export pressure difference and the opening size,when opening and differential pressure are large,relative displacement between the main valve core and valve core will generate and the fluid unbalanced force to valve core is minimal at around 50% opening.