Study of Magnetorheological Grease Flow in a Double Restriction Seal Configuration

Abstract

This work presents an investigation of magnetohydrodynamic flow in a novel double restriction seal configuration using micro-Particle Image Velocimetry (µPIV). A conventional seal design has been modified to impart magnetic effects in the flow of magnetorheological grease, which is prepared with 5% by weight of carbonyl iron particles dispersed in NLGI 3 grade lithium-soap-based grease. Rectangular bar magnets are fitted on the seal to induce an external magnetic field strength greater than 0.8 T. The grease flows between two restrictions in the annular domain, and the velocity field is captured by a µPIV technique. Experimental results predict that flow velocities are considerably lower in the presence of the magnetic field. Carbonyl iron particles orient themselves in the direction of the magnetic field and form strong chains which increase the yield stress of the grease medium. Maximum velocities are obtained in the vicinity of the shaft. Further, a numerical model has been developed to predict the velocities at different locations in the annular grease domain at varying rotational speeds of the shaft.