Numerical Modeling of the Gas Dynamics of the Safety Valve

Abstract

Gas-dynamic processes in a cavity of the safety valve with determination of force impact of a gas flow on a disk, taking into account the instability and compressibility of a flow are considered. The safety valve represents the mechanism automatically opening in case of increase in pressure to the value higher than the operating one and closed in case of pressure decrease to the operating one or slightly below it. The task of calculation of safety valves is throughput determination, selection of characteristics of their spring, the dynamic efforts arising when actuating the safety valve. The known mathematical models of operation of valves describing movements of a disk under the influence of forces from gas and a spring are based either on application of empirical coefficients, or on difficult implementable decision of the task on the gas-dynamic processes which are realized in three-dimensional setting with use of a package of ANSYS. In this paper the possibility of numerical modeling of the main gas-dynamic characteristics of the valve on the basis of the solution of the axisymmetric equations of gas dynamics is justified. The method of control volume is applied to the numerical solution of system of the gas-dynamic equations with an axial symmetry. Gas parameters on boundaries of control volumes are determined by S.K. Godunov's method with use of the self-similar decision of the task on decay of an arbitrary gap. In calculation the structured orthogonal difference grid constructed by a complex method of edge elements and displaying the curvilinear estimated area on a rectangle is applied. The mathematical model is written for movement of a disk of the valve taking into account the unstable change of pressure in capacity in which the pressure is regulated. Results of numerical modeling of the non-stationary process of opening and closing of the valve are received. The carried-out numerical modeling of gas-dynamic processes in the safety spring valve of direct action showed that the current in the area located above along a flow from a disk has an axial symmetry. The sound line "locking" this area from perturbations is lower along a flow adjoins to the edge of a disk for the prevailing time period. Results of an experiment confirm dynamics of opening of the valve calculated by the considered method.