Analysis and experiment of coupled bending and torsional vibration of a rub-impact dual-rotor system

For a dual-rotor system of aero-engine, the coupled bending and torsional dynamic equations with rub-impact force were first established using the Lagrange equation. The Runge-Kutta method was used for numerical calculation. Combined with waterfall map, spectrum diagram, bifurcation diagram, Poincaré map and amplitude-frequency curve, the spectral characteristics and bifurcation characteristics of the bending vibration and torsional vibration were analyzed. The torsional vibration of the rotor experimental platform was measured by incremental encoders to verify the spectral characteristics obtained from the simulation analysis. The research results show that the torsional vibration exhibits characteristic frequencies similar to bending vibration, including multiple frequency, fractional frequency, and the combined frequency of working frequency and multiple/fractional frequency, but these are more obvious in the torsional vibrations; bending and torsional vibrations have similar bifurcation process and same bifurcation point, and there are jump phenomena of amplitude at each bifurcation point.