基于非接触式测量的旋转叶片动应变重构方法

A dynamic strain reconstruction method of rotating blade based on blade tip timing non-contact measurement and transmissibility concept was proposed. The transmissibility between displacement and strain of any point was derived in the frequency domain. The analytical formula of transmissibility with respect to mode shapes was obtained. The three-dimensional (3D) finite element model of rotating blade was established to conduct modal analysis considering rotating pre-stress effect. The displacement and strain mode shapes of blade were extracted and the transmissibility between displacement at blade tip and dynamic strain of critical point at blade root under any rotational speed was calculated. The test for high-rotating blade based on blade tip timing non-contact measurement was conducted. The Circumferential Fourier transform method was applied for analyzing blade-tip displacement at different rotational speeds in case of single mode resonance. Combining with the transmissibility, the dynamic strain of five blades at some critical points was reconstructed. Results showed that when the first mode resonance at rotational speed of 9000r/min and 13000r/min occurred, comparing with the measuring results of strain gages, the average relative error of dynamic strain reconstruction of three critical points on the blade root, such as the maximum-strain point, the secondary-strain point and the edge point, was less than 15%, showing the validity of the dynamic strain reconstruction method.