Today there are a lot of findings to determine losses caused by contact forces inside roller bearings. But there are also losses in bearings caused by displacement of lubricant. These are known as churning or drag losses. In general the bearing manufacturers give recommendations how to reduce them. The most common solution is the reduction of the oil bath level. Some bearing manufacturers even provide models or empirical equations to calculate the resistance resulting from rolling elements moving through the oil. These models take the operating conditions such as the viscosity of the oil at the operating temperature, oil level, bearing type and rotational speed into consideration. A comparison between calculated and experimental results shows that there is still a deviation because of further effects which are not considered in those analytical models. This paper presents experimental studies and numerical simulations which illustrate the influence of the oil quantity on the total friction torque of tapered roller bearings and identify the resulting losses. Highlights• Method for investigation of drag and churning losses. • Influence of viscosity, oil quantity and rotational speed. • CFD simulation of a single-phase flow considering air content in lubricant. • Influence of the air content on the drag and churning losses.

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