Load Capacity of a Grooved Circular Step Thrust Bearing

Abstract

A parametric analysis based on narrow groove theory (NGT) has been presented for estimating the load capacity of a grooved circular step thrust bearing. Three types of grooving arrangements of the bearing surface, namely, (a) both the step and the recess are grooved, (b) only the step is grooved, and (c) only the recess is grooved, are considered. It is found that grooving in the step provides the most significant enhancement on the load capacity. The load capacity and the pumping power loss are affected by the step location, step height, and inertia. There is no benefit of making step location smaller than 0.6 that corresponds to the minimum power loss due to pumping. At a very large value of step location, say 0.85, the load capacity drops drastically. To take advantage of inertia as well as grooving, the dimensionless step location should be 0.6 ∼ 0.85 and the dimensionless step height should be less than 5. The load capacity also depends on groove geometry parameters such as groove inclination, groove depth, and fraction of area grooved. The groove inclination angle has been found to be the most important parameter that determines the increase or decrease in load capacity. For the most enhancement of load capacity, the inclination angle should be 135 deg with the direction of rotation, the groove depth should be at least twice the minimum film thickness, and the fraction of the step surface area grooved should be around 0.5.