Static and dynamic characteristics of magnetized journal bearings lubricated with ferrofluid

This work was concerned with the static and dynamic characteristics of the hydrodynamic journal bearings lubricated with ferrofluid. Based on the momentum and continuity equations, a pressure differential equation (modified Reynolds equation) was obtained. Assuming linear behavior for the magnetic material of the ferrofluid, the magnetic force was calculated. The magnetic pressure resulting from the magnetic force was incorporated into the Reynolds equation and it was not separately treated. The equation was solved numerically by the finite difference procedure, obtaining the appropriate iterative technique and pressure distributions. The load-carrying active region and cavitation region boundary shapes could be then determined. The solution renders the bearing performance characteristics, namely, load carrying capacity, attitude angle, frictional force at the journal surface, friction coefficient and bearing side leakage. By the finite perturbation technique, the eight-oil film stiffness and damping coefficients were determined. The dynamic coefficients were used as input data for studying the stability characteristics of the rotor-bearing system. The critical speed at which whirling motion begins to occur was calculated.