New step to improve the accuracy of blade tip timing method without once per revolution

Abstract

Abstract The mechanical vibration has always been one of the main factors that restrict the improvement of turbomachinery performance such as aero-engines. Blade vibration is one of the most important obstacle. As a non-intrusive vibration measurement method, blade tip timing (BTT) technology has the potential to replace strain gauges for blade dynamic stress monitoring. However, it still faces enormous challenges, one of which is the accuracy and reliability of the once per revolution (OPR) probe. Here, an efficient and high-precision compound reference (CR) based BTT method without OPR is proposed. The method is based on straight line fitting (SLF), and taking the blade at the midpoint of the SLF interval as the reference blade. The vibration displacement of the reference blade is obtained by the SLF of the time of arrival (ToA) of probe No. 1. Further, taking the blade as the reference, the vibration displacement of other blades is obtained. With this method, the actual blade installation angle and the probe installation angle can be measured simultaneously based on the none OPR method so as to further improving the measurement accuracy. By the numerical simulation, high speed test-rig and large scale industry turbo fan verification, the results indicate that the method has the merit of stronger anti-noise ability, less uncertainty, and much higher computational efficiency. Whereby, high-efficiency blade vibration measurement can be achieved in the whole operating speed range.