Effects of throttling window on flow rate through feed-water valves

Feed-water valves are widely used in nuclear power plants to regulate the flow rate of the water supplying to steam generators, and thus holding the water level in steam generators at desired values. The flow rate characteristics of feed-water valves have important effects on the management quality of the water level in steam generators and therefore influence the safety and the efficiency of nuclear power plants. In this paper, the effects of throttling window shapes on the flow rate characteristics through feed-water valves are investigated in two aspects, the overall performances and the fluid dynamics. First of all, a dimensionless parameter defining throttling window shapes is proposed for the quantitative assessment. Then, for the analysis of overall performances, the rated flow coefficient, the loss coefficient, and the inherent valve characteristics are investigated. A revised fitting function is obtained to predict the inherent valve characteristics with different throttling window shapes for engineering applications. Finally, for the observation of the fluid dynamics, the velocity characteristics and the pressure characteristics are both discussed. The wear conditions are predicted at different relative travels and throttling window shapes. This paper provides a reference for researchers dealing with the design work of feed-water valves and is beneficial for the improvement of the whole water level control system.