Study on the methods for lessening errors due to probe position shift in blade tip timing measurement

摘要

Blade tip timing (BTT) is a promising technique for the measurement of blade vibrations. Synchronous (Engine Ordered) vibration and asynchronous (non-Engine-Ordered) are two typical kinds of blade resonances occurred under excitations. Current techniques for evaluating the engine order are intricate and inexact while the estimation of the amplitude can be biased considering the fiber optic probe position shift caused by the case growing in different directions. Moreover, data analysis process in the synchronous case is more involved and more sensitive to noise. Methods utilizing four sensors for the analysis of BTT data from assemblies undergoing synchronous resonances has been suggested. First, based on compressive sensing, sparse blade tip timing signals were represented and reconstructed to evaluate the engine order. Second, the amplitude on synchronous resonances was estimated adopting the optimal placement of probes which is insensitive to errors due to probe position shift by calculating a reference condition number. In the end, numerical simulation examples of synchronous vibrations are carried out to validate the feasibility of proposed methods. The main advantage of this series of methods is the more accurate identification for vibration parameters considering the probe position shift error without increasing the probe number.