Magneto-rheological fluid based squeeze film damper for semi-active unbalance response control of rotor

Abstract

About four decades ago, the invention of a squeeze film damper (SFD) has compromised with the dilemmatic characteristics of the conventional bearings, such as ball and journal bearings. Kinematically, the SFD is a kind of journal bearing in which the journal can only vibrate or whirl but not spin: the outer raceway of the rolling element bearing, or an attached sleeve, serves as the journal of the SFD. It is usually slotted or restrained loosely with a pin to prevent spin. The most important effect of non-rotating journal is that a rotor supported on SFDs does not execute oil whip, i.e., SFDs are rotordynamically stabilizing at all rotational speeds. Generally, the dynamic behavior of such a rotor system depends strongly upon the dynamic characteristics of the SFD in service and, therefore, it is important to know the characteristics of the SFD accurately. Recently, the trends in turbomachinery seeking for a greater power output per unit of weight, and for higher speed and lighter weight power transmission shaft, demand a need for the development of flexible rotor and shaft technology. The implementation of a lightweight flexible shaft for power transmission brings the apparent advantages of having fewer parts, a less complex mechanism, and more efficiency. However, the flexibility of such a shaft makes it more sensitive to small unbalances and often results in an instability problem as disturbances, such as component shift, wear and corrosion, act on the shaft. Therefore, researches in the area of developing a controllable damper that works in active or semi-active way have been paid much attention by both researchers and engineers. Among the vigorous activities, semi-active SFDs using controllable fluids, such as electro-rheological (ER) and magneto-rheological (MR) fluids, instead of conventional lubricants are initiated recently. Especially, MR fluids are non-colloidal suspensions of polarizable particles having a size on the order of a few microns and resp...