An error correction blade tip-timing method to improve the measured accuracy of blade vibration displacement during unstable rotation speed

Abstract

Rotor blades, being the key part for power and energy conversion, are essential to the safety of turbomachinery. Monitoring the running state of rotor blades is significantly important to ensure the safety of blade operation. The blade tip-timing (BTT) technology has many advantages of non-intrusive measurement being a popular monitor method. The accuracy of vibration data obtained by BTT method is critical to evaluate the running state of blade. However, the blade vibration displacement obtained by the traditional BTT (T-BTT) method and its extended methods still faces the calculation errors caused by unstable rotation speed. To improve the calculation accuracy of blade vibration displacement and minimize the calculation errors caused by unstable rotation speed, the error correction BTT (EC-BTT) method is proposed. In this method, the calculation errors caused by unstable rotation speed are analyzed, and then the calculation errors are eliminated by the derived formula to obtain more accurate vibration displacement data. The EC-BTT method is proved to be feasible and effective by simulation models and a large-scale industry axial fan. The results indicate that the EC-BTT method can eliminate the calculation errors of vibration displacement caused by sudden change and fluctuating speed. The method also can be used in T-BTT and its extended methods.