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The identification results for the static performance characteristics of a large tilting-pad bearing in load between pad configuration are presented for specific bearing loads between 1.0 and 2.5 MPa and for circumferential speeds up to 79 m/s. The bearing is lubricated by spray-bars and can be described by the following specifications: Five pads, 0.23 nominal preload, 60% offset, 56° pad arc angle, 500 mm inner diameter, 350 mm pad length and 1.28 per mille relative bearing clearance. The axial oil flow is reduced by a fixed seal on both bearing edges which has a nominal radial clearance of 1 mm. The film pressure and the gap width are determined in the whole area of the sliding surface by an axial shift of the shaft. The bearing temperatures are measured by means of 100 thermocouples located 5 mm behind the sliding surface. The experimental results indicate that significant pad deformation occurs in circumferential and in axial direction. Also the effective supply temperatures are much higher than the nominal ones. According to the lubricant flow the sensor temperatures close to the spray-bars at the sliding surface rise about 20 K for 7 l/s and 40 K for 3.5 l/s at 3000 rpm. The temperatures are nearly constant between all pads and depend only on speed and not on load. The theoretical analyses of the bearing performance was accomplished with the bearing calculation software COMBROS. This code models the transition between laminar and turbulent flow and solves an extended Reynolds equation, the three dimensional energy equation of the film and the heat conduction equations of the shaft and the pads considering various boundary conditions due to the judgment of the user. Concerning the minimum film thickness, the maximum temperature on the sliding surface and the maximum film pressure only poor agreement was reached if the influence of the axial pad deformation was neglected. In advanced analyses a co-simulation between COMBROS and a structural mechanics software shows that an improvement of the prediction was achieved. The comparison of the measurement data and the advanced simulation shows very good agreement for the characteristic bearing parameters as well as for the local distributions of film pressure, temperature and film thickness in the whole operating range of the bearing. Further, the applied inlet mixing model for the lubricant supply process proves to be very suitable.

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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