Investigating Grease Behaviour in Tilted Double-Row Tapered Roller Bearing Installed in Wind Turbine by Developing a Full Scale Multi-Phase CFD Model

Abstract. Lubrication plays critical role in effective performance of Tapered Roller Bearings (TRBs) used as main-bearing in wind turbines. Several experimental and CFD-based studies have investigated lubrication behaviour in single-row TRBs. However, grease-lubricated double-row TRBs have not yet been studied extensively, particularly in large size bearings. Therefore, this paper aims to investigate in detail the grease behaviour in a tilted double-row TRB installed in direct-drive wind turbine by developing a novel, full scale, multiphase CFD model. This model was implemented in open-source environment OpenFOAM^®, using a transient, incompressible solver. The grease was modeled as a non-Newtonian fluid using the Herschel-Bulkley formulation, with its rheological parameters determined by performing a best-fit analysis on experimentally obtained data. The simulated operating conditions included three grease filling ratios—45 %, 35 %, and 21 % of total volume of bearing lubricating chamber—at rated rotational speed i.e. 17.5 rpm with a bearing tilt of 5° towards the Main-Frame Side (MFS) w.r.t the vertical axis. The results highlight the grease flow characteristics including grease distribution, fluxes, and pressure fields within the bearing after one complete rotation of cage at the stated operating conditions. They emphasize that the lubricant behavior inside the bearing is strongly affected by the combined influence of bearing tilt and gravitational forces.