Cavitation problems occur frequently on high temperature pressure reducing valves(361valves)used in ultra supercritical units.Combining with the serious cavitation on the based board of three links of the 361 valve used in Hechuan Power Station

the flow field inside the 361 valve was numerically simulated by Fluent software

on the basis of two-phase cavitation flowing equations.The results show cavitation is an important reason for failure of this kind of valve

which is basically in accordance with the actual failure case.Thus the rationality of this numerical analysis method is verified.According to the simulation results

after the tail pipe was lengthened at the T piece

the pressure at bending point of the T piece decreased by18.09% and the fluid speed reduced by 50.45%.The steam content at the bending point the T piece dropped significantly and the vortex phenomenon weakened dramatically

so the valve's service life was prolonged.