A blade tip-timing method without once-per-revolution sensor for blade vibration measurement in gas turbine engines

The blade vibration measurement is crucial for gas turbine engines in order to ensure safe operations. One of the techniques is blade tip-timing (BTT), which is under the assumption that rotor speed is constant and depends on a once-per-revolution (OPR) timing reference to calculate the blade tip displacement, and identifying the blade sequence. However, this assumption is incorrect for transient conditions, and the installation of OPR sensor sometimes is not allowable and reliable. These reasons greatly limit the application of BTT technique. This paper proposes a self-correcting (SC) BTT method to realize the blade vibration measurement under different operating conditions without using the OPR sensor, which is based on the polynomial fitting and a reference probe is used to correct high-order fitting coefficients. Numerical results show that the SC-BTT method can greatly reduce the fitting error caused by blade pitch and vibrational parameters. Experimental results demonstrate that the proposed technique is capable of removing the limitation of the lack of OPR sensor and overcoming the drawbacks of OPR system, such as the failure of OPR sensor or low-speed resolution. For three investigated cases, the relative errors of derived rotor speed are below 0.12%. The relative error of blade peak-to-peak amplitude (PPA) and the initial phase angle are around 3% at the resonance region with engine order (EO) 2.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author