The large-diameter gate valve in the closing process and small opening conditions are easy to cause flow resonance,resulting in strong vibration of the valve stem and valve plate.This paper proposed the structural optimization method of adding pipe expansion after the valve to reduce the sudden change of the fluid flow state to reduce the resonance,and it gave three specific ways of improvement.The feasibility of optimization is analyzed by comparing the pressure pulsation and resonance amplitude of the liquid flow system in the gate valve pipeline before and after optimization.The results of the study demonstrate that the addition of an expanding tube after the valve can reduce vortex and pressure pulsation after the valve,so that the fluid within the valve will be stabilized faster.After optimization,the amplitude of co-oscillation of the valve at 1/16 and 1/8 opening is reduced from 26.819 mm and 2.347 mm to 10.036 mm and 1.959 8 mm,which greatly reduces the amplitude of co-oscillation of the valve in a small opening,and effec-tively reduces of resonance damage to valves.The large value of pressure pulsation is concentrated in the low frequency range(50 Hz)under small opening,and the shedding vortex frequencies are 26.72 Hz and 28.44 Hz,which are prone to flow-excited resonance when the valve system is in the second-order and fourth-order modes,so that it should be avoided to work in the small-opening condition and corresponding frequency range.The results of the study can provide a reference for optimizing the optimization of vibra-tion damping of large-diameter gate valves.
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