Fluid Energy Conversion Analysis in Hydraulic Channels of reactor coolant pump under flow coastdown transient

Abstract

Conversion between dynamic energy and static pressure energy is complex in reactor coolant pump (RCP) hydraulic channel in nuclear plant station, especially under flow coastdown transient. The performance was calculated by numerical simulation. The performance of RCP under flow coastdown is studied, and the energy conversion characteristics of hydraulic components are analyzed. The results investigated show that with increasing of coastdown time head loss decreases sharply from coastdown starting. After the coastdown time of 10 s, the head loss in the channel of impeller, guide vane and volute decrease to 50% below. In the process of coastdown, dynamic pressure head of the inlet flow domain drops rapidly from 6.8 m, and finally decreases to 0 m, while static pressure head gradually increases from −7 m, and closes to 0 m after coastdown time is 140 s. When coastdown starts, dynamic energy above 24.33 m is mainly distributed at the outlet of impeller, the inlet of guide vane and the outlet of volute. When t= 110 s, the dynamic energy in most area is below 12.17 m, and when t= 200 s, the dynamic energy is small, distributed in the range of 0 m∼6.08 m. With coastdown time increasing the dynamic energy on pressure and suction surfaces of impeller and guide vane blade decreases. At t= 90 s, dynamic energy is lower at leading edge of blade than that at trailing of impeller blade, and the maximum energy of guide vane blade is located at the root of leading edge. As the coastdown time increases, static pressure energy of RCP inlet flow domain and impeller inlet continues to increase, while the larger static pressure energy distribution area in the volute gradually decreases.