Characteristics analysis on 3D blade tip clearance response with regard to turbine blade crack azimuth angle

Abstract

Abstract In view of the insufficiency that blade tip timing signals offer merely one-dimensional information, which restricts the extraction of fault characteristics during the detection of blade cracks, a three-dimensional blade tip clearance (3D-BTC) finite element (FE) model of aero-engine turbine blade-disk-shaft system is developed. With the proposed FE model, the effect of crack azimuth angle on the 3D-BTC of aero-engine turbine blades is analyzed. Firstly, a FE model of the aero-engine turbine blade-disk-shaft system is established. Then, the through crack is introduced at the blade, and the blade deformation under the influence of cracks at different roll angles and pitch angles is calculated by transient dynamics analysis. Finally, the spectrum of the 3D-BTC is obtained, and the characteristics of the 3D-BTC response concerning blade crack azimuth angle are investigated. The results show that the crack reduces the blade stiffness and affects the 3D-BTC. The 3D-BTC decreases with the enlargement of the crack roll angle, and it shows a decrease and then an increase as the crack pitch angle becomes larger. The radial tip clearance is easily affected by the position of the measurement point, while the circumferential deflection angle and the axial deflection angle at different measurement points show a consistent trend. The information on cracks can be reflected more accurately on the basis of the 3D-BTC.