带摩擦阻尼器长叶片振动特性优化研究

为了防止透平机械长叶片因振动而导致的疲劳损坏,目前普遍采用的方法是在叶片上增加摩擦阻尼结构.针对带摩擦阻尼器长叶片的结构特点,采用扭曲梁与空间直梁单元模化叶片,推导叶片阻尼连接单元的力学模型,由此建立叶片总的动力特性分析方程.然后详细分析某阻尼围带长叶片具有不同围带厚度和围带间隙的振动响应,由此获得优化的阻尼围带结构,该分析结果还与自由叶片的响应数值进行对比,发现共振时由于围带的阻尼效果,优化阻尼结构的最大响应值只有自由叶片的42.4%.最后分析添加整圈松拉金结构的叶片振动响应,发现松拉金的加入将进一步降低叶片振动响应值.分析结果表明,该数值模型可以应用于多种摩擦阻尼器长叶片的振动特性分析及优化设计,将为阻尼叶片的设计提供实用工具.

NUMERICAL MODEL AND OPTIMIZATION FOR DYNAMIC CHARACTERISTIC OF LONG BLADE WITH FRICTION DAMPER

Adding damped structure can decrease dynamic stress of blade and avoid blade fatigue failure from forced vibration.Based on the structural feature of long blade with friction damper,pretwist beam element and space straight beam element were adopted to discrete the blade,and the numerical model of damper link element was established,then the gross finite element motion equation of the blade was obtained.The response of a last stage long blade with different thickness shroud and gap between shrouds was investigated in detail,then the optimal structure of damped shroud was obtained,the comparison for response between damped blade and freestanding blade shows the maximum response of blade with optimal damper is 42.4% of that of freestanding blade.At last,the tie wire was added to the damped blade,numerical result shows it can decrease blade response further.Dynamic characteristic of various dampers of blades can be analyzed by the numerical model,and it may be usable for optimization of damped blade.