Investigation of a multi-ball, automatic dynamic balancing mechanism for eccentric rotors

摘要

This paper concerns an analytical and experimental investigation into the dynamics ofnan automatic dynamic balancer (ADB) designed to quench vibration in eccentric rotors.nThis fundamentally nonlinear device incorporates several balancing masses that are freento rotate in a circumferentially mounted ball race. An earlier study into the steady statenand transient response of the device with two balls is extended to the case of an arbitrarynnumber of balls. Using bifurcation analysis allied to numerical simulation of a fullynnonlinear model, the question is addressed of whether increasing the number of balls isnadvantageous. It is found that it is never possible to perfectly balance the device atnrotation speeds comparable with or below the first natural, bending frequency of thenrotor. When considering practical implementation of the device, a modification isnsuggested where individual balls are contained in separate arcs of the ball race, with rigidnpartitions separating each arc. Simulation results for a partitioned ADB are comparednwith those from an experimental rig. Close qualitative and quantitative match is foundnbetween the theory and the experiment, confirming that for sub-resonant rotationnspeeds, the ADB at best makes no difference to the imbalance, and can make thingsnsubstantially worse. Further related configurations worthy of experimental andnnumerical investigation are proposed.