A Numerical Simulation for Predicting the Gear Drag Torque

The gear is one of the vital components of power transmission, and its churning loss is a significant factor that determines the efficiency of the mechanical system when it is operated without a load. The gear churning loss has long been analyzed using empirical correlations with experiment; however, computational performance has recently improved and has enabled 3D CFD (three-dimensional computational fluid dynamics). In this study, analyses to predict the gear churning loss were performed using a 1D method and 3D simulation. Two techniques for the rotating motion of the gear, namely the sliding grid technique and MRF (multiple reference frames), were adopted. A multi-phase model with the VOF (volume of fluid) method was used out to predict the interfacial flows. A good agreement was obtained by comparing experimental data, empirical relation, and 3D analysis results at a rotation speed of 5,000 rpm. From the results, further study on the detailed lubricant flow is possible through validated 3D CFD simulation.