Five dimensional movement measurement method for rotating blade based on blade tip timing measuring point position tracking

Abstract

As a non-intrusive blade vibration measurement technology, Blade Tip Timing (BTT) has been widely studied and developed in recent years. However, there are still many potential uncertainties in BTT technique, which reduce the correlation of the BTT measurements against the Finite Element (FE) predictions and the Strain Gauge (SG) measurements. One of the main ones is that the BTT sensor only measures the displacement of the blade tip in the direction of rotation. But blade tip movements other than rotation direction including axial, lean, bend, untwist, and sweep will change the position of the measuring point relative to the blade tip. In this paper, a method for measuring the five dimensional blade tip movements is proposed. This method uses BTT data, blade tip profile equation, and the initial measuring point position to track the actual measuring point position relative to the blade tip during blade rotation, so as to determine the blade axial, lean, bend, untwist, and sweep. Simulation results have proven the effectiveness and accuracy of the proposed method. Experiments were carried out on the test rig, industrial axial fan, and engine fan, results show that the method can effectively and accurately measure these types of blade tip movements. The relative error of blade untwist angle measurement is 3.6%. The work in this paper can improve the reliability of BTT measurements, and is of great significance to the comprehensive perception of operation state and accurate evaluation of dynamic stress of rotating blades.