Passive vibration absorbers for vibration reduction in the multi-bladed rotor with rotor and stator contact

Contact phenomena are among the most undesirable incidences in a rotor dynamic system where its emergence could be due to the centrifugal force generated by an unbalance disk. In this work, a Jeffcott rotor supported by oil film journal bearings and with rigid blades is taken into account. The long oil film lubrication is considered where the axial flow is negligible. The rotational speed is taken as a control parameter, and the analysis is performed for two different clearances considering the rotor with three, four, and five blades. To reduce the vibrations of the system with the purpose of contact elimination, a tuned mass damper and a nonlinear energy sink as passive absorbers are utilized. Then, by an optimization process applying a complex averaging method, the optimum parameters for each absorber are calculated. Due to the critical behavior of the system in the lower clearance values, double coupling of the absorbers is suggested. The results demonstrate that single coupling of the absorbers can considerably reduce the vibration of the system. On the other hand, for the lower clearance value single coupling is not efficient, and double coupling could be utilized to mitigate the unwanted vibrations of the system.