Dynamic Characteristics Analysis of Pilot Valves with Different Inlet Diameters Installed on the Main Steam Valve Set

The Main Steam Valve Set(MSVS) is the key protection equipment for nuclear power plants, whose dynamic characteristics are directly related to the security of the secondary circuit system under overpressure conditions. Dynamic mesh technology is used in this work to capture the dynamic characteristics of the interconnected pilot valves on the MSVS with different inlet diameters. The research results show that increasing inlet diameter can significantly reduce the opening time of the pilot valves, but it will also increase the fluid force of valve stem during the opening process as well as the movement speed at the maximum opening. The pressure of the pilot valves during the opening process is then analyzed. It can be seen that changing the inlet diameter will affect the inlet annular throttling area, thereby changing the pressure rise speed in the external chamber of the valve stem and the inner cavity of the valve body, thereby affecting the total response time. This work provides a reference for the selection of the pilot valve diameter in MSVS, and helps to improve the overpressure protection capability of MSVS