The Disc Structure And Equal Percentage Flow Characteristic Analysis Of Pressurize Spray Valve Of Nuclear Power Plants

The pressurized spray valve is one of the important equipment for the pressure control of the reactor coolant system, which is located in the pressurized spray system of the reactor coolant system of the 3rd generation of pressurized water reactor nuclear power plant. Pressurized spray valve highly valued in the field of nuclear power utilization, requires equal percentage flow characteristics, and its accuracy directly affects the stability of the system.In this paper, pressurized spray valve uses V-ball valve and diaphragm actuator as its basic structure. The flow characteristic analysis of the pressurized spray valve is mainly discussing the flow area analysis. Different circulation area has different flow resistance, so the flow coefficient is not the same. Want to make the flow characteristics reach to the ideal equal percentage flow characteristics, we must change the circulation area in different openings, and make flow coefficient be close to the coefficient of the ideal equal percentage flow characteristics, and then improve its flow characteristics.Through simplifying fluid model, this article uses the Bernoulli equation to derive the circulation area and flow coefficient, and then through the analysis of the relationship between the circulation area and the input motion, the calculation formula of flow coefficient and the input motion is established. When studying the motion of the actuator and valve disc, the paper derives the motion equation of the valve disc, and gives the main structure parameters, such as the length of the connecting rod, the length of the rocker and the offset distance of the push rod. In circulation area calculation, the paper establishes the valve disc rotation model, and the structure parameters are given, such as the V-shaped angle and position, round size, spherical radius and the diameter of the valve seat, etc. In order to obtain equal percentage flow characteristics, through the calculation of valve disc dynamic motion equation, flow coefficient equations, the relationship between the parameters and the final flow rate characteristic curve, and the comparison of theory and calculated curves, the actuator structure optimization and valve disc structure optimization schemes are proposed.Finally, by performing the control valve flow test, the relative flow characteristic curve and the test data are compared, which verifies the correctness of the calculation method and the optimization scheme.Through the above research, we effectively improve the pressurized spray valve flow characteristics, so that the flow characteristics and equal percentage flow characteristics tend to be consistent, reducing the flow coefficient error. In this paper, the equal percentage flow characteristics in different stroke of valve disc motion formula, circulation area calculation formula and flow coefficient calculation method and the corresponding optimization method, provides a fast and efficient method for engineering design, simplifying the design and calculation process, to avoid a large number of test, saves the cost.