Session: 11-13-01: Fluids and Public Health and Medicine / Industrial Flows

Paper Number: 167011

A Three-Dimensional Computational Fluid Dynamics Study of Electric Vehicle Bearing Geometries and Their Influence on Lubrication Performance 

Optimal lubrication is critical for the efficient operation of electric vehicle (EV) drivetrains for the proper functioning of transmission gears and bearings. Insufficient lubrication can lead to mechanical failures, while excessive oil increases power loss through churning. In high-speed operation, rolling bearings significantly impact energy efficiency due to churning losses, which arise from the interaction of rotating components with the lubricant. Accurately predicting these losses in the bearings remains a challenge. This study employs a CFD approach, utilizing unsteady Reynolds-Averaged-Navier-Stokes equations and capturing the gas-liquid interface, to investigate the complex multiphase flow within EV drivetrain roller and ball bearings. Key considerations include: (1) Realistic motion: The model incorporates the rotation of the cage, races, and rollers/balls around the shaft, as well as the self-rotation of the rollers/balls. (2) Accurate geometry: A novel meshing technique is developed to accurately represent the thin gaps between components while preserving their original shapes. (3) Comprehensive analysis: Simulations are conducted across various shaft speeds and oil inlet flow rates for the bearings to investigate the influence of shaft speed/oil inflow on multiphase flow characteristics and oil distribution within the bearings. Furthermore, the study explores different types of bearings individually, including tapered roller, and deep groove ball bearings in these operations to analyze the inherent physics associated with each bearing. The study aims to: (1) Understand oil dynamics: Investigate the mechanisms of oil feed, splash, and distribution within individual bearings (2) Quantify churning losses: Determine the impact of operating conditions and bearing design on churning power losses. The study highlights the strong dependence of multiphase flow characteristics and oil distribution on factors such as shaft speed, oil inflow and bearing design. Results show that the churning losses increase with the increasing rotational speed of the shaft while the oil retention decreases with the increasing rotation speed. Results also demonstrate how the geometrical complexities of the bearings as well as changes in oil inflow affect the oil splash pattern which significantly affects how the bearings get lubricated, thereby affecting the churning loss characteristics.  The computational study was validated by comparing the computed churning power loss of the bearings at quasi-steady operation with the experimental measurements. Since the study is validated and considers all moving components of the bearing without any approximation and accurately resolves all the thin gaps between the respective solid components, the CFD methodology developed in this study is a valuable tool for guiding the design and development of more efficient rolling bearings. This is particularly crucial for electrified driving systems where minimizing energy losses is paramount.

Presenting Author: Ashutosh Pandey Simerics, Inc.

Presenting Author Biography: Senior Engineer at Simerics, Inc.

Authors:

Ashutosh Pandey Simerics, Inc.
Abdul Motin Rivian Automotive
Chiranth Srinivasan Simerics, Inc.
Alain Ganamet Rivian Automotive