A Parametric Study of the Dynamics of a Six-Pocket Hydrostatic Journal Bearing

This paper presents a numerical investigation into the dynamics and pressure distribution of a full hydrostatic bearing with six pockets. The pockets are rectangular and the effects of their depth are investigated by choosing a deep pocket type (0.25in) and a shallow one (0.01in), respectively. Parametric studies are partitioned in operational and geometric. The operational ones include the effects of bearing eccentricity and shaft rotation speeds. The geometric ones are the concentric clearance and the pocket depth. Whether deep or shallow the pockets have the same footprint projected base. It was found that the pocket’s depth causes the pressure to be either uniform across the pocket (deep pocket) or vary (shallow) in a ramp increasing in the direction of rotation. In both cases a Raleigh step effect is observed at the downstream edge of the pocket. More interestingly, in the convergent region the hydrodynamic effect on the lands creates pressures that are significantly higher than those in the hydrostatic pockets when the rotational speeds are high. It was found that for narrow clearance the effect of pocket depth on cross-coupled and direct stiffness is negligible, while for the large clearance the stiffness decreases with the increase in the pocket depth. For either type of pocket the stiffness increases with eccentricity and rotation whether the concentric clearance is large or small.