Detailed CFD Modeling of the Mixing Behavior in Oil Supply Pockets of Heavy Duty Gas and Steam Turbine Journal Bearings

Abstract

Oil supply pockets are essential parts for the functionality of journal bearings, because mixing and oil carry-over issues are substantially dominated by these design features. In recent years, the great potential of Computational Fluid Dynamics (CFD) has been recognized. An extensive analysis of the turbulent multiphase flow phenomena including cavitation has been reported for a whole gas and steam turbine journal bearing (GT2012). Furthermore, the complex structure of the turbulent flow in an oil supply pocket has been investigated numerically and validated by Laser-Doppler-Anemometry (LDA) measurements (GT2013). The interaction between oil supply jets with the main flow and the effective mixing behavior remained as challenging tasks. Therefore this study focused on this interaction by means of an up-scaled geometry and a full scale journal bearing. Due to the upscaled geometry, it was possible to assess the flow phenomena experimentally. An extensive CFD analysis including large eddy simulation (LES) was conducted and validated by flow visualizations. The influence of geometric features and performance parameters was investigated. It was found, that even minor changes of the inflow conditions could lead to measurable effects with regard to mixing and oil carry-over behavior.