Suppression of multi-modal torsional vibration of the long-shafting rotor system with nonlinear piecewise NES

Long-shafting rotor systems tend to cross multi-order natural frequencies at start up and coast down, and the multi-order modes of vibration are excited by various excitations. The bending vibration can be limited to the single rotor, but the torsional vibration is obviously coupled between each single rotor, which leads to more problems. Therefore, the current work proposes to suppress the multi-modal torsional vibration of long-shafting rotor system by a single nonlinear piecewise NES (PNES). The dynamic models of long-shafting rotor system and the long-shafting rotor-PNES system are established in which the PNES is used to suppress the first two-order torsional vibration. The genetic algorithm (GA) is used to optimize the multi-modal transient and steady-state torsional vibration suppression results of PNES to obtain optimal parameters design, respectively. And the influences of the parameters of long-shafting rotor-PNES system and the additional position of PNES on the vibration suppression effect of PNES are also discussed. The experimental verification of the suppression of the first two-order steady-state torsional vibration of the long-shafting rotor system by a PNES is carried out. In numerical simulation, the percentage of accumulated energy dissipation of the PNES can reach 52.2 % for the multi-modal transient torsional vibration, and the inhibitions of the three torsional vibrations by the PNES are about 71.6 % and 77.9 %, 67.5 % and 81.2 %, 68.5 % and 69.5 % in the multi-modal steady-state torsional vibration suppression. In the test, only the suppression of the first torsional vibration by PNES is tested, that the PNES can reduce the first two-order steady-state torsional resonances of the first torsional vibration of the long-shafting rotor system by 62.1 % and 65 % respectively.