大口径楔式闸阀广泛应用于石油、化工管道系统，其常承受介质动压载荷与温度载荷的耦合作用；耦合载荷不仅会加剧阀门结构的变形，增加阀杆与阀盖的摩擦磨损，也会影响流体流态，严重时甚至会诱发流激振动，造成阀杆断裂。该文针对DN1 200 mm大口径闸阀实际工程应用中的阀杆断裂问题，采用过程离散分析法划分多阀板位置，利用ANSYS数值模拟技术可视化了闸阀流场的流动特征，基于傅里叶信号分析法揭示了流体域的压力脉动响应，并对阀门管道液流系统进行模态分析和谐响应分析，研究了特定行程下多物理场耦合作用的阀杆和闸板共振特性。结果表明：当闸阀启闭且行程较小时，阀后因闸板扰流作用出现大的卡门涡街和回流现象，流体压力脉动增大且流动紊乱，进而诱发阀门管道液流系统产生大的共振幅值，导致阀杆断裂。基于此，提出在阀后添加扩管，发现添加扩管可缓解阀后涡流和回流，减小压力脉动，进而避免流激共振的发生。该文还定性和定量分析了扩管尺寸对流体压力脉动和共振幅值的削弱作用，对比研究表明：扩管直径为1.3倍管径（1 560 mm）且长度为1倍管径（1 200 mm）时，减振效果最好。该文研究结果对大口径闸阀的减振优化研究具有一定的指导意义。

Large diameter wedge gate valves are commonly used in petroleum and chemical pipeline systems, where they endure a coupled load of dynamic pressure from the medium and thermal loads. This coupled load not only exacerbates the structural deformation of the valve but also increases the friction wear between the valve stem and the valve cover. Additionally, it may affect the fluid flow pattern, and, in severe cases, may induce flow-induced vibration, leading to valve stem fracture issues. Aiming at the problem of valve stem fracture in the practical engineering application of DN1 200 mm large-caliber gate valve, this paper uses the process discrete analysis method to divide the position of multi-valve plate, adopts ANSYS numerical simulation technology to visualize the flow characteristics of flow field in the gate valve, and employs Fourier signal analysis method to reveal the pressure pulsation response in fluid domain. Then, the modal analysis and harmonic response analysis of the valve pipeline flow system are carried out, and the resonance characteristics of valve stem and gate plate with multi-physical field coupling under specific stroke are studied. The results show that, when the gate valve opens/closes and the stroke is small, the large Karman vortex street and backflow phenomenon are generated due to the disturbance of the gate plate after the valve, the fluid pressure pulsation increases and the flow condition is disordered, which induces the valve pipeline flow system to produce a large common amplitude value, resulting in the fracture of the valve stem. Therefore, this paper proposes and verifies that the addition of expansion pipe can alleviate the vortex and backflow behind the valve, reduce the pressure pulsation and avoid the flow-induced resonance. Qualitative and quantitative analyses are finally performed to determine the expansion pipe size to weaken the fluid pressure pulsation and the common amplitude value. The comparative study shows that the vibration reduction effect is the best when the diameter of the expansion pipe is 1.3 times that of the pipe (1 560 mm) and when the length of the expansion pipe equals the diameter of the pipe (1 200 mm). The obtained results have certain guiding significance for the vibration reduction optimization research of large-caliber gate valves.