航空发动机叶片高频模态阻尼的实验测试方法

以NASA Rotor37叶片为对象,研究了航空发动机叶片的高频模态阻尼比的实验测试方法.实验分析和数值计算均说明:在随机声激励下获得频响曲线将包含由支撑结构振动造成的峰值.基于此提出在支撑结构上布置多个传感器的实验方案,并以支撑结构的振动峰值位置和能量相对大小来判定叶片振动主导的振动峰值.用小波阈值收缩法和曲线拟合法对这些振动峰值进行了降噪和模态阻尼比识别,给出了实测模型在10kHz内"叶片主导振动"的模态阻尼比.结果表明:一般的结构金属材料条件下,叶片结构的高频模态阻尼比的数量级小于1%,且随频率增加呈下降趋势.

Experimental test method for high-frequency modal damping of turbomachinery blades

High-frequency modal damping ratio experimental identification of turbomachinery blade was studied using NASA Rotor37 blade. The blade was tested by random acoustic excitation in order to obtain evident high frequency response. It is shown, both numerically and experimentally, that the obtained frequency-response curve at high-frequency also showed the information of the excited modes from the supporting structure. Therefore the vibration of the supporting structure was also monitored by several sensors. Then a data processing approach was proposed to distinguish the blade dominant peaks by comparing the energy transfer ratio of the blade with that of the supporting structure. After wavelet threshold denoising, the blade's modal damping ratios less than 10kHz were obtained by fitting the blade dominant peaks. Additionally, the results show that the magnitude of blade's high-frequency modal damping is less than 1% when it is produced by general metal materials, and the magnitude has a downward trend along with the frequency.