Rotor Dynamic Behaviour of Electro-Rheological Lubricant Operated Multi-Lobe Journal Bearings

An Electro-rheological (ER) fluid comprises dielectric particles blended in a non-conducting oil. The ER lubricants are commonly known as smart lubricants. This study utilizes an ER lubricant to examine the static and dynamic response of multi-lobe journal bearing. The lubricant flow within the journal-bearing clearance space is described by Reynold’s equation, while the non-linear behavior of the lubricant is characterized using the Bingham model. The solution of the Reynolds equation is obtained employing the Newton-Raphson method, with numerical addressing of gaseous cavitation in the fluid film through a mass-conserving algorithm. The effects of lobe geometry and the applied electric field are scrutinized on bearing performance metrics. The equation of motion for the journal is solved utilizing the fourth-order Runge-Kutta method to predict journal center locus/trajectories. The utilization of ER lubricant in conjunction with a two-lobe journal bearing notably enhances the minimum film thickness by 63.5%, the direct stiffness parameter by 182.4%, and the damping parameter by 210.14%. The multi-lobe configuration adversely affects the frictional power loss of the bearing system. The threshold speed, a critical parameter in the design and operation of journal bearings, is improved by the ER effect and is higher for multi-lobe bearings. In multi-lobe configurations of journal bearings operating with ER lubricant, linear motion journal trajectories are noted to be smaller and more stable. Under given operating conditions, designers should prioritize two-lobe journal bearings operating with ER lubricants, as they exhibit greater stability and superior performance metrics in both steady-state and dynamic conditions.