某大型汽轮机组旁排阀流固耦合特性分析

Analysis on fluid-solid coupling characteristics of bypass valve of a large steam turbine unit

某1750 MW大型汽轮机组在启动联调期间发生多起由振动引发的旁路调节阀(旁排阀)部件疲劳断裂情况,影响机组的安全运行。本文旨在揭示旁排阀流致振动机理及振动规律,为旁排阀结构优化和运行方式优化提供参考。通过对阀内介质流体动力学仿真分析,发现阀内介质存在明显的旋涡脱落和边界层分离现象,且随着阀门开度变化,流动特性发生显著变化。结合流体、结构动力学仿真结果及振动测试结果,开展了流固耦合综合分析。分析结果表明:阀内漩涡脱落激发的抖振是阀杆及连轴器断裂的主要原因,阀门结构优化改善了介质湍流及旋涡脱落程度,但是阀门在大开度下反复调节流量时,依然会激发阀杆及联轴器较高的振动水平;阀门大开度下激发的涡激共振是紊流罩破坏的主要原因。

During the start-up phase of a 1750 MW large scale turbine unit,several fatigue fracture cases occurred in by-pass valve components due to valve vibrations,which affected the safety operation of the units.The goal of this paper is to reveal the vibration mechanism and law of by-pass valve,and provide references for its structure and operation mode optimization.Simulation is performed to investigate the fluid dynamics inside the valve.The results show that,there are obvious vortex shedding and boundary layer separation phenomena in the valve fluid medium,and the flow characteristics change significantly with the changing valve opening degree.Based on the simulation results of fluid structural dynamics and vibration test results,the fluid structure coupling comprehensive analysis is carried out.The analysis results indicate that,the vibration induced by vortex shedding in the valve is the main cause of the fracture of the valve stem and the coupling.The valve structure optimization decreases the turbulence and vortex shedding degree of the fluid medium.However,when the flowrate is regulated frequently at large valve opening degrees,the higher vibration level of valve stem and coupling will still be excited.The vortex induced vibration of the valve with large opening degrees is the main reason for the damage of turbulence hood.