Oil distribution and churning losses of gearboxes: Experimental and numerical analysis
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Currently, energy efficiency represents one of the main requisites in mechanical design. Gearboxes play an important role in several industrial applications and, even if they are already characterized by high efficiency, their performance can still be improved, leading to energy saving and the reduction of pollutant emissions. The possibility to investigate different gearbox geometries and operating conditions in the preliminary stages of design represents a clear advantage for engineers and can significantly contribute to the achievement of these objectives. However, analytical formulations that are able to accurately describe gear losses, especially those due to the interaction with the lubricant, are not available or are not accurate enough. Furthermore, the analytical models are typically not suitable for novel gearbox designs. In the present work, a numerical approach based on Computational Fluid Dynamics (CFD) for the prediction of lubricant fluxes and power losses of gearboxes is presented. The presented methodology utilizes a meshing strategy that reduces the computational effort of the simulations and enables parametrical studies. The numerical approach is validated both with torque measurements and data regarding the oil flow obtained by the Particle Image Velocimetry (PIV). Thus, the validation of the numerical approach is performed not only qualitatively with respect to the oil distribution but also quantitatively with respect to the torque and velocity field in the oil sump. Good agreement of the CFD and experimental data was observed for the torque, oil distribution and fine flow details including the vorticial structures and recirculation areas.