Development and Validation of an Efficient TEHD Model of Tilting Pad Journal Bearings

The constant increase of turbomachinery rotational speed has brought the design and the use of journal bearings to their very limits: tilting pad journal bearings (TPJBs) have been introduced for high-speed/high-load applications due to their intrinsic stability properties and can be used both in transient and steady-state operations obtaining superior performances. TPJBs operation involves different physical aspects, like the pads flexibility and the heat exchange between solids and fluids. An accurate analysis of the TPJBs behavior is essential for a successful design and operation of the system; however, it is necessary to reach a compromise between the accuracy of the results provided by the TPJB model and its computational cost. The present thesis exposes the development of an innovative and efficient quasi-3D TPJB modeling approach that allows an accurate analysis of the interactions between the fluid dynamic and thermal phenomena with the elastic behaviour of the solid components (ThermoElastoHydroDynamic analysis); the majority of existing models describes these aspects separately but their complex interactions must be taken into account to obtain a more accurate characterization of the system. The main objective of the proposed model is to provide accurate 3D results with low computational times; furthermore, it is characterized by a strong modularity, allowing for complex transient simulations of the complete plant and for the representation of different kinds of bearings. In this thesis, the whole model has been developed and experimentally validated in collaboration with Nuovo Pignone General Electric S.p.a., which provided the required technical and experimental data.