MECHANISM OF OCCURRENCE OF SELF-EXCITED OSCILLATIONS OF A ROTOR WITH A CLEARANCE BETWEEN BEARING HOLDER AND HOUSING

It is well known that, in a rotor system with a radial clearance between a rotating part (ex. shaft) and a static part (ex. guide), a forward rubbing with the same angular speed as the rotational speed , a backward rubbing with an angular speed proportional to , and various kinds of nonlinear resonances occur. On the contrary, some rotor systems have a clearance between a movable but non-rotating part and a static part. For example, a squeeze-film damper bearing has a clearance between a bearing holder and housing. In such a system, a self-excited oscillation occurs in addition to various kinds of nonlinear resonances. In this paper, the characteristics of this self-excited oscillation are investigated and the mechanism of the occurrence of a self-excited oscillation is clarified by considering energy balance