针对某型低压汽轮机支撑结构的共振问题，利用ANSYS平台建立三维模型，采用数值计算的方法开展模态分析。计算得到该支撑结构冷态8阶固有频率及对应振型，分析了温度场对模态的影响机理。研究表明：冷态计算1~8阶共振频率分布于18.57~147.41 Hz之间，最大振幅极值出现在第5阶模态，达到了22.49 mm位移幅度；在汽轮机组运行过程中，结构模态受热力因素影响将发生变化，变化原因其一是不均匀温度场引起的热应力，其二是材料属性随温度变化；在转子转速调节范围内，应避免在各阶临界转速区间长时间停留。

In view of the resonance problem of the support structure of a certain low pressure steam turbine,a threedimensional model was established by using the ANSYS platform,and the modal analysis was carried out by means of numerical calculation.The resonance frequency and corresponding vibration mode of the support structure at cold eighthorder were obtained by calculation,and the influence mechanism of the temperature field on the mode was analyzed.The research results show that the resonance frequencies at cold firstorder to the eighthorder are distributed between 18.57 to 147.41 Hz,and the maximum amplitude limit value appears in the fifthorder mode,which reaches the displacement amplitude of 22.49 mm.During the operation of the steam turbine unit,the structural mode will change under the influence of heat,one of the change reason is the thermal stress caused by the uneven temperature field,and the other is the change of material properties with temperature.In the range of rotor speed adjustment,long stay at each order critical speed interval should be avoided.

TK264.9