GENERALIZATION OF RESEARCH RESULTS ON FRICTION LOSSES AND TEMPERATURE IN ROLLING BEARINGS WITH CERAMIC AND STEEL BALLS

Abstract

A generalization of the results of an experimental study on temperature and friction losses in rolling bearings with ceramic and steel balls has been carried out. It is based on comparative tests of all-steel bearings and similar bearings with rolling elements made of silicon nitride (hybrid bearings) under oil-jet lubrication. The generalization was performed using dimensionless criterion-based relationships. The Reynolds, Prandtl, and Euler numbers were adopted as similarity criteria.

Criterion-based relationships were obtained for determining friction power losses under jet lubrication, taking into account the effects of load, thermophysical properties of the lubricant, oil flow rate, ball diameter and quantity, and rotor rotational speed. Experimental results showed that the obtained values of power losses in hybrid and all-steel bearings are quite close. The main components of power losses in a bearing are friction losses between the rolling elements and the rings and cage, as well as losses due to oil churning.

Since oil flow rates in aviation bearings (the study was conducted for aerospace applications) are typically high due to cooling requirements, most of the losses are associated with the oil, accounting for 60–80% of the total losses. Accordingly, differences in the materials of rolling elements, which determine variations in friction losses, are outweighed by the substantial oil-related losses. This made it possible to derive a generalized formula with only a slight reduction in the accuracy of regression coefficients.

The obtained analytical expressions for determining power losses were used to calculate bearing temperatures under the assumption that external heat removal from surrounding components is absent. The research results enable a more substantiated approach to selecting bearing types and predicting their thermal state and power losses.