The flexible supports make it possible to decrease the forces transmitted between the working machines and their foundations. As rotating machinery, the hydrodynmic bearings exhibiting compliance and considerable damping together with high load capacity are ofen used for this purpose. Nevertheless, on certain operating conditions, the hydraulic forces produced in the thin oil film can destabilize the rotor equilibrion position, which consequently leads to development of the rotor self-excited vibration of large amplitude. There are several ways how to increase the critical speed of the rotor rotation at which the self-excited vibration starts. Recently, the attention was focused on increasing damping in the rotor supports or on modification of the bearings geometry. At present time there are available many active control devices working on various physical principles. In this paper the research of the concept based on controlled kinematic excitation of the bearings shells is carried out. The performed computer simulations prove that the investigated technique enables to reduce amplitude of the self-excited vibration and to increase the rotor angular speed of rotation, at which the self-excited vibration begins. Suppression of the rotor oscillation is always connected with increasing the force by which the turning rotor acts on its stationary part. The developed computational procedures and results of the performed analyses are intended for finding properties and behaviour of the active control devices for mitigation of excessive vibration of rotating machines and to contribute to their proper design in this way. and Obsahuje seznam literatury
Test stand for investigation of the influence of bearing bushing movement control on behaviour of a rigid rotor supported in sliding journal bearings was designed. The stand was equipped with two pairs of piezoactuators, enabling to move each bearing bushing in two directions, and with two pairs of relative sensors tracing shaft movement at both bearings. The initial tests showed quite unexpected phenomena, which should be cleared up, before experiments with controlled bearing bushing movement could be started. Finally the system began to operate according to predictions and it was possible to start intended experiments. Some results of the rotor behaviour with and without piezoactuator action are presented.