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Experimental and Computational Studies of the No-Load Churning Loss of a Truck Axle
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
This paper summarizes 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 performed. The CFD modeling accounted for design geometry, operating speed, temperature, and lubricant properties. The model computed the torque loss due to oil churning due to the viscous and inertia effects of the fluid. It also displayed the flow pattern generated and computes the oil volume fraction at any location within the volume. CFD predictions of power losses were then compared with no load measurements made on a specially developed dynamometer driven test stand. The same axle that was 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 performed 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. Those comparisons were very favorable. This capability will be used to effect design improvements in lubrication properties, housing and gear geometry, and fluid level and flow characteristics.