TEHD Performance Evaluation of Planetary Gear Journal Bearings with Flexible Bushings for Wind Turbine Gearboxes

Abstract Planetary gear journal bearings are a promising alternative to rolling bearings in large wind turbine gearboxes, but their reliability is challenged by transient gear-meshing loads, high angular misalignments, and strongly coupled thermo-structural effects. This paper presents a mixed thermo-elastohydrodynamic simulation framework that couples the generalized Reynolds equation with a mass-conserving cavitation model, asperity contact, and bearing surface mechanical deformation obtained through a reduced FEM substructure. The framework further incorporates a conjugate heat-transfer formulation to account for thermal interactions between the lubricant and the solid interfaces. The proposed approach is applied to a 7 MW wind turbine planetary journal bearing and is used to compare a baseline bushing design with a flexible configuration featuring circumferential grooves at both axial ends. The results show that the grooved configuration leads to a substantial increase in the minimum oil film thickness while simultaneously reducing the maximum hydrodynamic pressure, with the mean pressure remaining nearly unchanged and only a slight rise in the maximum temperature. In addition, the presence of grooves effectively suppresses mixed lubrication conditions by significantly reducing asperity contact across the range of operating conditions investigated.