Self-synchronization and Automatic Balancing in Rotor Dynamics

Abstract

Synchronous elimination as one of the possible methods of cancelling any harmful vibration resulting from the unbalance of rotary machines is considered. This method, introduced by Fesca and Thearle, involves the placement of unbalanced elements (e.g. ring, pendulum, ball balancers) on the rotor axis, which can occupy any angular position in relation to the rotor. Under defined conditions in the postcritical frequency range, there is a spontaneous placement of the corection elements such that they balance the rotor unbalance. Hedaya and Sharp generalized this method by combining two force balancers to compensate the unbalanced moment as well as the unbalanced force of a rigid rotor.In the present work this generalization is analysed in detail. The existence and the stability conditions of compensating phasing are developed by the method of direct motion separation, the dependence of these conditions on the polar inertia is investigated, and the validity of Blekhman's principle of self-balancing is discussed.The results are confirmed by computer simulation. Moreover, computer simulation is used to investigate transient motions induced by initial conditions.