Experimental Study on Vibration Characteristics of Rotor-Rotor Inter-Shaft Labyrinth Seal Rubbing Faults in a Counter-Rotating Aero-Engine

Abstract In order to solve the problem of rotor-rotor inter-shaft labyrinth seal rubbing fault during the test run of a counter-rotating dual-rotor aero-engine, based on the fast Fourier transform, the vibration time-domain signals of three groups of cross-sectional measuring points on the casing are analyzed in the frequency domain, and the three-dimensional waterfall diagrams of each cross-sectional measuring point and the spectrum diagrams of the step section of the time-domain signal are drawn. The analysis results show that when the high- and low-pressure speeds are both in steady-state, the rotor-rotor inter-shaft labyrinth seal rubbing causes a sudden increase in the amplitude of some measuring points on the casing; the spectrum diagrams at the measuring points of the intake casing and turbine casing sections show regular combined frequencies f1 + k2f2 and k1f1 + f2 characteristics, and the frequency 2f1 + f2 component is dominant; the double fundamental frequency components of the rotating frequency with different amplitudes appear at some of the cross-sectional measuring points. Finally, based on the vibration transfer path analysis method, the vibration characteristics of the rotor-rotor inter-shaft labyrinth seal rubbing fault are analyzed mechanistically, and combined with the results of engine disassembly inspection, it is comprehensively judged that the fault is due to the increase in rotor vibration caused by the rise in high- and low-pressure speeds. Furthermore, the labyrinth seal on the low-pressure rotor expands more due to the high temperature than the wear-resistant coating area, resulting in a reduction in the gap between the labyrinth seal and the wear-resistant coating on the inner side of the high-pressure rotor, which leads to the rotor-rotor inter-shaft labyrinth seal rubbing fault.