Blade tip-timing vibration velocity analysis without Once-Per-Revolution sensor

In traditional blade tip timing (BTT) techniques, it is common to use a Once-Per-Revolution (OPR) sensor as a reference to obtain the expected time of arrival (TOA) for each blade, which is then compared to the measured actual TOA to calculate the vibration displacement. However, in practical applications, installing a reference sensor in the optimal measurement position is often challenging. Finding a real or virtual alternative reference baseline for calculating blade vibration becomes difficult. To address these issues, this paper proposes a method that eliminates the need for an OPR sensor and the calculation of expected arrival times to obtain vibration displacement. Instead, it only requires two BTT sensors and the measured arrival times to obtain blade tip vibration velocity without an OPR sensor. This method substitutes vibration velocity for traditional vibration displacement, reducing the uncertainties in BTT measurements and still enabling accurate acquisition of blade vibration parameters.