带气膜阻尼结构振动特性的理论研究

针对航空发动机气膜阻尼的结构设计需求,基于挤压间隙流理论和能量方程建立气膜阻尼的力学模型,由此获得气膜阻尼结构的等效刚度系数和等效阻尼系数,通过振动方程的理论推导获得放大因子的表达式.结果表明:气腔厚度、气腔初始压强、吸振薄板模态频率和安装位置是影响减振效果的关键参数.气腔最优厚度主要由附面层厚度和实际振动频率决定,需结合实际情况确定气腔厚度,以最大程度降低振动响应;气腔初始压强越高,阻尼系数越大;吸振薄板的固有频率应尽可能与叶片本体接近,并且安装在本体振动响应最大位置,以取得最好的减振效果. 

Theoretic investigation on vibration characteristics of structure with air film damper

According to the configuration design requirements of the air film damper in the aero engines, the mechanics model of the air film damper was built based on the extrusion gap flow theory and energy equation. Therefore, the equivalent stiffness coefficient and the equivalent damper coefficient were obtained. The amplification factor's expression was also obtained through derivation from the vibration equations. Research results revealed that,the air cavity thickness, the initial cavity pressure, the modal frequency and the location of the absorbing vibration plate were the key parameters which determined effect of vibration reduction. The optimization air cavity thickness was determined by the boundary layer thickness and vibration frequency, thus the best value could be acquired according to the particular case in order to depress the vibration response to the maximum extent. The damper coefficient increased with the increase of the initial cavity pressure. The nature frequency of the additional plate was recommended to be close to that of blade, and the absorbing vibration plate was suggested to be installed on the location with the maximum vibration response,in order to obtain the best effect of vibration reduction.