Numerical Simulation Of Reliability On The Closing Process Of Axial Check Valve

Check valve is a key component of pipeline system, whose service ability,serviceable life and reliability directly affects the safety of the pump units and thewhole pipeline system. Since the traditional methods of reliability test always takelong time and cost much money when we evaluate the reliability of the valve, a newmethod of reliability test should be formed based on the effective reliability ofnumerical simulation on typical hydraulic components.During the closure of the check valve, the movement of check valve disc isextremely complex, involving the interaction of the fluid-solid coupling problem withhydraulic force and spring force, always along with the water hammer which is sodangerous that should be avoided. Hence Fluent dynamic mesh method is applied todescribe the dynamic motion of valve disc. In this paper, the relationship betweenparameters such as displacement, time, velocity, acceleration, hydraulic force, etc. isgiven by programming, then the CFD simulation during the closing process of2Daxial check valve is analyzed in static-pressure condition and pump-off conditionrespectively. Finally the reliability of the system is numerical analyzed by MonteCarlo method and the structure is optimized through the reliability sensitivity analysis.Contributions in this thesis are listed as follow:(1)UDF and dynamic mesh technology is a strong tool to represent the closingprocess of2D axial check valve and study the hydrodynamic characteristics of flowfield in check valve. When check valve starts to close, the valve disc responseinstantly to close; at first the valve disc velocity increases to maximum, and thendeclines until closed fully.(2)After the pump stops working, check valve can be reliably shut down; thevelocity of the valve is in oscillation when it is nearly closing, as the hydraulic force isoscillated during the stage. During the closure, the flow field of check valve ischanging due to the movement of the valve disc. The maximum velocity appears inthe upper right of the valve disc, and the highest pressure appears in the throttle.While the flow section area suddenly reduces with the motion of the valve disc, thevelocity of flow increases, and the pressure decreases, there are obvious reflux andvortex, and the turbulent kinetic energy here is higher than that in the downstream.(3)The reliability of the system was analyzed by Monte Carlo method. The resultshows spring stiffness, the diameter of the valve and the thickness of valve disc arethe main effects through the reliability sensitivity analysis. The reliability of system isimproved observably after optimizing the key variables.