Performance evaluation of large-size tilting-pad thrust bearings based on results from small-size models

Abstract

Large hydrodynamic tilting-pad thrust bearings can exceed diameters of 5 meters, which makes them difficult to test experimentally, which is important in the case of new designs. Therefore, smaller test bearings should be used to fulfil the demand for experimental verification. However, due to the complexity of thermal and flow phenomena, the choice of parameters in scaled tests is not obvious. In this paper dimensional analysis was used to determine the parameters that account for all relevant phenomena in the full-size bearing. As a result of the rigorous use of dimensional analysis, a set of scaling factors was determined. Calculations using an advanced Fluid Solid Interaction (FSI) model showed that the results for a large bearing and its scaled model perfectly agree. However, in the practical planning of the experiments, some parameters after appropriate scaling would be challenging to obtain – e.g., material properties. Next, it was checked if a more liberal approach, namely, leaving some less important parameters without proper scaling, would still allow for a good agreement of the results between a large bearing and a scaled model. The results showed, however, that all parameters have a great influence on the results. Without rigorous application of the dimensional analysis, the similarity between a large bearing and its scaled model is not obtained. The authors recommend that only rigorous dimensional analysis yields proper results. Experiments on small bearings should rather be used to verify theoretical calculation models and it seems impossible to carry out properly scaled experiments.