Transient mixed elastohydrodynamic performance of journal bearings in wind turbine gearbox during start-up considering multi-component elastic deformations

Abstract

To improve the torque density of wind turbine gearboxes (WTG), planet gear roller bearings are being replaced by planet gear journal bearings (PGJBs). However, the low rotational speeds, wide load variations, and varying operating conditions during startup significant challenges to the performance of PGJB. In this paper, a transient mixed elastohydrodynamic (EHD) model of PGJBs during start-up is proposed, which comprehensively considers multi-component elastic deformations, misalignment, and intermediate oil return groove (IORG) characteristics. Specifically, the dynamic rotational speed, meshing force, and moment of the planet gear, extracted from the wind turbine drivetrain model, serve as inputs for the PGJB. The influence mechanism of the IORG, radial clearance, and modification parameters on the transient EHD performance of PGJB is investigated, followed by experimental validation. Results indicate that the IORG effectively mitigates misalignment in PGJBs while simultaneously inducing earlier contact and significantly increasing both film and contact pressures. This leads to a multi-regime lubrication distribution at the PGJB interface and further influences its contact characteristics. During startup, the primary load-bearing regions maintain hydrodynamic lubrication, whereas the IORG-affected zones transition from mixed lubrication during mid-startup to boundary lubrication under rated operating conditions. Contact occurs in the edge region of the PGJB when the modification depth is less than 30 μm, and shifts to the IORG region at greater depths.