Numerical Calculation of the Oil Flow in a Truck Rear Axle Transmission and the Influence of Gear-Induced Air Flow

For the reliable operation of a gearbox, consistently sufficient lubrication of machine elements is necessary. Thus, the gearbox fluid flow plays an important role. The state of the art indicates that computational fluid dynamics (CFD) enables targeted support of the gearbox development process at an early stage. Computational time plays a prominent role in practical applications. The particle-based smoothed particle hydrodynamics (SPH) shows great potential for time-efficient calculations, especially with a simplified single-phase modeling approach. This study first examines the influence of gear-induced air flow on gearbox oil flow, focusing on a test gearbox to identify a suitable modeling approach for a truck rear axle transmission. The results indicate that the gear-induced air flow mainly impacts gearbox oil flow at higher circumferential speeds. For lower circumferential speeds, a single-phase model yields good results with significantly reduced computation times compared to a two-phase model. Applying the single-phase model to the truck rear axle transmission and comparing numerical results with experimental findings demonstrates a reliable representation of the oil flow characteristics.