Experimental and Computational Studies of the No-Load Churning Loss of a Truck Axle 2020-01-1415

This paper describes the work performed in predicting and measuring the contribution of oil churning to the no-load losses of a commercial truck axle at typical running speeds. A computational fluid dynamics (CFD) analysis of the churning losses was conducted. The CFD model accounts for design geometry, operating speed, temperature, and lubricant properties. The model calculates the oil volume fraction and the torque loss caused by oil churning due to the viscous and inertia effects of the fluid. CFD predictions of power losses were then compared with no-load measurements made on a specially developed, dynamometer-driven test stand. The same axle used in the CFD model was tested in three different configurations: with axle shafts, with axle shafts removed, and with ring gear and carrier removed. This approach to testing was followed to determine the contribution of each source of loss (bearings, seals, and churning) to the total loss. After bearing and seal loss measurements and predictions were factored in, the churning loss measurement and prediction comparisons were made. Experimental and computational results compared favorably. This capability will be used to implement design improvements in housing and gear geometry, lubrication properties, fluid level, and flow characteristics.