Experimental and Numerical Investigation of Gear Flow Field Effects on Churning Torque under Low-Temperature Conditions

To address the significant obstacles to vehicle transmission performance in extremely cold conditions, an integrated experimental and simulation investigation is conducted. The oil flow of a gear at low temperatures is investigated using a visualization test rig to capture the flow patterns at different speeds and temperatures. The dynamic mesh approach is used to create a simulation model of the gear’s flow pattern. The correlation between the flow pattern and the churning torque of the gear is investigated. The results indicate that when rotational speed increases, the flow pattern changes from an envelope flow pattern to a reverse hill-shaped flow pattern, and the oil around the gear tooth tips changes from oil bridges to oil filaments. The churning torque curves are divided into three stages in different speed intervals, and the churning torque decreases with increasing speed in the transition stage. As the ambient temperature fell from -20°C to -30°C, the torque escalated by 200.1%. The results reveal the mechanism of the influence of the variation in flow pattern on the churning torque which provides experimental and theoretical support for the design and application of efficient lubrication of transmission systems at low temperatures.