Investigation on the drag force mechanism of rolling elements in cylindrical roller bearing with under-race lubrication

The revolution motion of rollers is affected by the drag force of lubricant oil, which has a significant impact on high-speed roller bearing dynamics behavior and power dissipation. To study how the drag force acts on cylindrical rollers of bearing with under-race lubrication, a transient two-phase model was established. Flow characteristics inside the bearing, pressure coefficient, shear stress distribution, and drag force at different relative positions between roller and oil feed holes are analyzed. In addition, a drag force measurement device with cylindrical roller elements in a sandwich space was tested. The numerical results are in good agreement with the experimental data, with an error of about 10%, which proves the accuracy of the numerical method. The results indicate that the drag force is predominantly determined by pressure distribution, contributing over 95% of the total force, while viscous shear stress plays a minor role. Since the supplied oil through feed holes has the same rotating speed as the inner ring, which is faster than the roller's revolution speed, the drag force acting on the roller appears as a pushing force rather than a resistance force. Parametric studies reveal that both the average and maximum drag forces increase with bearing speed and oil flow rate, whereas oil viscosity exhibits a non-monotonic influence. Based on systematic numerical results, empirical formulas for predicting the average and maximum drag forces are derived via multiple linear regression suitable for cylindrical roller in bearing with under-race lubrication. The R-squared (R2) values of 0.992 39 and 0.994 85, respectively, demonstrate an excellent fit for both formulas.