透平叶片试验模态分析中的离散建模方法研究

Study on Discrete Modeling Method of Modal Testing for Turbine Blade

在试验模态分析过程中,离散建模方法的不同对模态分析结果的准确性产生重要的影响。对某一透平弯扭叶片,根据模态理论构建模态分析试验台,通过对比实验,从振型的真实性、振型的可分辨性、测试误差大小以及测试时间方面综合研究离散建模方法对试验模态分析结果的影响。结果表明,所建立的模型越接近真实叶片的形状,其模态振型越逼真,但是对各振型频率的数值影响不大;选择合理的离散网格数目能在保证振型的可分辨性的基础上减少测试误差。研究的结论为透平叶片试验模态分析过程中的测试模型和离散网格数目的确定提供了指导。

In the process of model testing, the difference of discrete modeling methods will impact the accuracy of analysis result. This paper describes a modal analysis approach of a curved and twisted blade using a test bed based on experiment modal analysis method. Through the contrast tests, the influence of the discrete modeling method upon the model testing result is investigated from the authenticity of the mode of vibration, the distinguish ability of the mode of vibration, the error size, and the testing time. The research results show that the more the test model is similar to the real shape of the blade, the higher the fidelity of the model shape is, but the test model hardly impacts the natural frequency of vibration. On the other hand, choosing a reasonable discrete element number will decrease the error size on the basis of ensuring the distinguish ability of the mode shape. The conclusion of this research provides guidance for turbine blade modal testing with the determination of the test model and discrete element number.