Three-dimensional Steady Numerical Simulation Of Critical Flows And Cavitation Flows In Nuclear Safety Relief Valves

The safety relief valve is a significant safety accessory to pressure loaded installations. This paper researched the superheated steam critical flow and supercooled water cavitation flow in the nuclear safety relief valve by the CFD software, CFX. The results are useful for the structure design and optimization of safety relief valves. The main work was as follows:(1) External vessel was added to the outlet of valve to form the geometry model. The flow field of superheated vapor was simulated with different lift, pressure on inlet and the position of lower adjusting ring. The results indicate that the sonic surface appears in the annular region consisting of the upper adjusting ring and the lower adjusting ring, not on the cross-section of throat, when there is the critical flow; the region of sonic surface increases with the increase of pressure on inlet and the height of lower adjusting ring; the critical flow suppresses the discharge capacity; properties of superheated vapor have slight impact on the velocity field and affect the temperature field strongly.(2)The cavitation flow of supercooled water with constant properties was simulated in the steam safety relief valve with different geometry, pressure on outlet and velocity on inlet. Data from the field indicates that the cavitation occurs mainly in the annular region consisting of upper adjusting ring and lower adjusting ring; the cavitation flow decreases the action performance of the valve seriously when there is cavitation in the annular region consisting of the recoil surface and the sealing surface; the number of cavitation increases with the increase of velocity on inlet and decreases with the increase of lift and pressure on outlet.