Flutter Prediction Method for Long Blade of Steam Turbine

doi:10.12096/j.2096-4528.pgt.21001

Abstract

Abstract:

A three-dimensional fluid-solid coupling calculation model of long blade of steam turbine was established based on the aerodynamic and structural vibration simulation platform. Taking the second last stage blade of a foreign 60Hz steam turbine unit as an example, the aerodynamic characteristics of the flow field in the single flow channel and the vibration characteristics of the entire blade structure field were analyzed. Combined with the energy method criterion, a method for predicting and evaluating the flutter of the steam turbine long blade was further proposed. The results show that the unit flow rate and the vibration form of blade pitch diameter have a great influence on the blade flutter characteristics. For the current 2nd last stage blade, the probability of blade flutter induced by pressure fluctuation in the flow field is between 80% and 90% under 40% flow condition. Therefore, this kind of blade should be carefully used under the low flow condition. Based on the unidirectional liquid-solid coupling method, the periodic work under fluctuating pressure in flow field can be analyzed effectively and relatively quickly, and the aerodynamic damping coefficient under modal vibration of blade can be obtained. Thus, the flutter characteristics of blade can be predicted.

Key words: steam turbine, liquid-solid coupling, aerodynamic characteristics, vibration characteristics, flutter prediction

CLC Number:

TK05

Changchun LIU, Chun GUAN, Kuijun GUO, Yufeng LI, Yiliang MA. Flutter Prediction Method for Long Blade of Steam Turbine[J]. Power Generation Technology, 2021, 42(4): 500-508.

Figures/Tables 12

References 16

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材料参数		设计参数
参数	数值	参数	数值
材料	0Cr17	设计转速/(r/min)	3 600
密度/(kg/m³)	7 780	数量	68
泊松比	0.3	叶高/mm	441.5
弹性模量/MPa	213 000	设计流量/(t/h)	325.8

材料参数		设计参数
参数	数值	参数	数值
材料	0Cr17	设计转速/(r/min)	3 600
密度/(kg/m³)	7 780	数量	68
泊松比	0.3	叶高/mm	441.5
弹性模量/MPa	213 000	设计流量/(t/h)	325.8

工况	进口模式	进口压力/Pa	进口温度/K	出口模式	出口压力/Pa	出口温度/K
100%流量	Inlet	51 552.6	357.2	Outlet	31 110.0	—
40%流量	Opening	33 615.1	344.3	Opening	31 110.0	343.1

工况	进口模式	进口压力/Pa	进口温度/K	出口模式	出口压力/Pa	出口温度/K
100%流量	Inlet	51 552.6	357.2	Outlet	31 110.0	—
40%流量	Opening	33 615.1	344.3	Opening	31 110.0	343.1

项目	单向流固耦合	双向流固耦合
计算对象	周期功、气动阻尼系数	非定常力、振动位移
假设条件	叶片做恒幅振动；频率为某阶固有频率；指定叶间相位角	仅考虑汽流力的影响；叶间相位角由计算流道数决定
简化程度	只需计算两流道	一般需全周计算
输入参数	入口、出口工况参数	入口、出口工况参数
传递参数	流场压力数据；该工况某一节径振动频率下单只叶片各个节点x, y, z三个方向的网格位移数据	流场压力数据；结构场网格位移数据
目标差异	旨在获得叶片气动阻尼与振型、叶间相位角的关系，依据气动阻尼正负判断节径振动是否会激发颤振	旨在获得汽流激振力作用下流场–叶片的耦合作用，依据振动位移收敛性来判断颤振是否发生
预测评价	基于模态共振条件来预测颤振，结果偏保守，计算量较小，适合工程应用	仅考虑了汽流力作用来判断颤振，结果有风险，计算量大，计算机配置要求高