CFD Modelling and Experimental Validation of Temperature Profile at Pad Leading Edge of Tilting Pad Journal Bearings

An oil-film bearing is a mechanical component that exploits the hydrodynamic lubrication principle to support a rotating shaft. In tilting-pad journal bearings, the pad ability to tilt allows the bearings to support the load, theoretically eliminating the cross-coupling forces that compromise the system stability, as occur in fixed geometry bearings. The temperature of the oil at the leading edge of the pad results from the oil-mixing process that occurs in the between-pad region. A correct prediction of this temperature is fundamental for the estimation of the static and dynamic properties of Tilting Pad Journal Bearings (TPJBs). The most common approach used for the estimation of the leading-edge temperature adopts the so-called mixing-coefficients approach. A hot oil carry-over coefficient is used to describe the fraction of hot oil coming from the upstream pad. A constant leading-edge temperature is obtained as a result. In general, the value selected for the hot oil carry-over factor strongly affects the results and needs to be accurately selected. In this study, a three-dimensional Computational Fluid Dynamic (CFD) model is introduced to simulate the mixing of the oil in the groove and to extract the temperature distribution at the leading edge of downstream pads. The CFD model is then linked to a thermo-hydrodynamic (THD) model for the oil-films that solves both the Reynolds and the energy equations. To validate the integrated model, an experimental campaign was carried out by introducing an array of temperature probes in the groove. Finally, the numerically estimated temperature distribution at the leading edge of the downstream pad is compared with the experimental results.