Imbalance vibration is a significant concern in virtually all rotating structures and is an important problem in engineering. Strategies for imbalance vibration mitigation traditionally fall into two categories; i) passive balancing via attached eccentric masses, and ii) vibration suppression using tuned-mass absorbers or active bearing actuation. The aim of this project is to advance an alternative approach based on the principle of passive, nonlinear, automatic balancing. This approach requires use of a special class of balancing devices know as Autobalancers which have eccentric masses that freely revolve around the rotor?s axis of rotation. Automatic balancing is achieved through nonlinear dynamic interaction between the rotor?s lateral vibration and the balancer mass motions. At certain supercritical rotor speeds, the balancer masses naturally adjust their positions to cancel the rotor?s imbalance. A key advantage of the automatic balancing approach is its ability to naturally adapt to imbalance changes without requiring power, sensors or a control system. The overall goals of this project are to; a) develop a nonlinear dynamic analysis for predicting stability and limit-cycle behavior in flexible shaft and bladed-disk rotors fitted with autobalancer devices, b) explore novel kinematically modified autobalancer concepts to stabilize unwanted non-synchronous limit-cycle orbits in autobalancer systems, c) and explore placement and interaction of spatially distributed autobalancers to achieve multi-mode automatic balancing of flexible rotors. These analyses will be experimentally validated using a flexible-rotor/autobalancer testrig.
The nonlinear dynamic analysis methods developed in this project will have important scientific impacts in other active research areas such as coupled fluid-structure dynamics, machine tool vibrations, and rotor-stator interaction problems. This research will also have future benefits on the safety, reliability and efficiency of many civil infrastructures, power generation, transportation and aerospace systems which depend on smooth operation of critical rotating machinery. For example, by gaining an understanding of automatic balancing behavior in bladed-disks, this research will reveal new insights and approaches into the use of autobalancers to enable self-adjusting blade-loss compensation in gas turbine engines which, in turn, will enhance aviation safety. This project also has a significant educational mission. By performing this research, the graduate student involved in this project will be trained with strong analytical and experimental research skills and will develop deep knowledge in areas of rotordynamics, structural vibrations and nonlinear dynamics. Additionally, during high school outreach activities at the University of Tennessee, the laboratory setups in this project will provide a hands-on demonstration which will facilitate an entrée point to motivate and inspire younger students to pursue a scientific career. These efforts will have broad impacts on teaching the next generation workforce and will have a positive influence on education in the East Tennessee region.
