vibration analysis of a rotor bearing system supported on magnetorhelogical squeeze film dampers with short Bearing assumption

By using magneto-rheological (MR) fluid instead of lubricating oil in a traditional squeeze film damper (SFD), one can build a variable-damping SFD, thereby controlling the vibration of a rotor by controlling the magnetic field. In this paper, assuming a short length for the journal con-taining lubricant and bi-zone Bingham plastic model for MR fluid, the Reynolds equation for a short MR bearing is developed and solved to provide expressions for the pressure distribution and the damping forces. Afterwards the model of a rotor supported on two MRSFDs is developed using FEM. Then, the governing equations are solved numerically using the Newmark method. Above all, the pressure distribution along axial and sliding coordinates in journal bearing, transient and steady response of the system, eccentricity ratio and vibration amplitude changes have been investigated to study the behavior of the model. It is clearly observed that just existence of MRSFDs, without any magnetic field present, results in quite lower vibration amplitude in contrast with a rotor without any journal bearing. Moreover increasing the magnetic field in MRSFDs can considerably reduce the vibration amplitude of system, however, it leads to low amplitude variations in the response of system. Finally it was observed that the more the rotor speed is, the more magnetic field is neces-sary to relatively reduce vibration amplitude; this is limited by solidifying the MR fluid, though.

کلیدواژه ها:

Rotordynamics ، MRSFD ، Magnetorheological fluid ، Short bearing ، Long bearing