Numerical Simulation Research On Secondary Circuit Control Valve Of Nuclear Power Plant

The regulating valve is an important part of the nuclear power plant.When the operation conditions of the nuclear power plant change,the nuclear power plant changes the position of the opening and closing parts of the regulating valve to change the valve position,so as to change the pipeline flow,so as to adapt to the flow requirements of the nuclear power plant under different working conditions.As the regulator plays an important role in the operation of nuclear power plant,the nuclear power plant regulator has been widely concerned in the world.At present,there are few researches on nuclear power regulator,especially the unsteady flow and two-phase flow.This paper takes the secondary circuit feedwater control valve of nuclear power plant and the steam turbine medium pressure control valve as the research objects.The unsteady flow in the opening and closing process of the feedwater control valve and the twophase flow in the steam turbine medium pressure control valve are simulated by CFD.Through the one-dimensional three-dimensional coupling method Simulate the steady flow in a feedwater regulating valve and its piping.Through the analysis of the calculation results,a reference is provided for the design and safe operation of the regulating valve.Firstly,the geometric model of the water supply regulating valve is established,and the grid division scheme and the corresponding dynamic grid updating method are determined from the structural characteristics of the water supply regulating valve,the movement mode of the opening and closing parts and the quality of grid updating.Through the analysis of the Courant number,the time step of the transient calculation is determined.The simulation calculation of the unsteady flow during the opening and closing process of the water supply control valve is completed,and then the energy loss,pressure and velocity distribution in the control valve are analyzed according to the calculation results.Secondly,the two-dimensional and three-dimensional models of the steam turbine medium pressure regulating valve are established,and the grid division scheme of the steam turbine medium pressure regulating valve model is determined comprehensively considering the grid quality and the number of grids.By analyzing the flow characteristics of the steam in the medium pressure regulating valve of the steam turbine,a simplified assumption of the twophase flow in the valve is made.By analyzing the applicability of VOF model,Mixture model and Euler-Euler model,the multiphase flow model suitable for two-phase flow in valve was selected.After the simulation calculation of two-phase flow in regulating valve was completed,the simulation results were verified by combining with experimental data.Finally,the full one-dimensional simulation model and coupling calculation model of the water supply regulating valve and its pipeline are established.The applicability of onedimensional and three-dimensional coupling calculation method was verified by comparing the pressure difference of regulating valve with different opening degrees.The flow of regulating valve and its pipeline under different working conditions is calculated by one-dimensional and three-dimensional coupling calculation method.By comparing the calculated results,the influence of different working conditions on the flow in the regulating valve is analyzed.