叶片共振频率的测试原理与方法研究

通过力学分析和实验证实：叶片在受敲击等瞬态激励某段时间之后,其小阻尼自由振动发出的声音主要是一阶振动固有频率所确定的基音,而其它高阶振动固有频率所确定的泛音极弱,且叶片的一阶共振频率与一阶振动固有频率极为接近。因此,对一阶共振频率的测量就可以通过自由衰减曲线法转化为对基音频率的测量,即用敲击使叶片产生能够测量的自由衰减的声音信号,将记录下的时间历程与时标比较,便可算出该叶片的共振频率。

Research of Measuring Theory and Method on Resonant Frequency of the Impeller Blades

The resonant frequency of the impeller blades of APU load compressor is a target index necessary to be controlled in the process of the maintenance of impeller. Through a mechanical analysis and test, this paper proves that, having been knocked to have an instantaneous activation for a period of time, the soundscape generated by the free oscillation with small scale damp of the blades is mainly the basic sound determined by the one step inherent frequency, and the overtones determined by the higher step inherent frequencies are rather feeble; moreover, the one step resonant frequency of the blades approaches closely to the ir one step inherent basic frequency. Therefore, the measurement of their one step resonant frequency may be converted to the measurement of their inherent frequency by using a free attenuation curve procedure. That is to say, knocking the blades to generate measurable free attenuation sound signals and comparing the recorded time course with the time targets can calculate the resonant frequency of the blades.