Gearboxes are efficient systems for torque transmission, with an overall efficiency over 99 % if well designed. Nevertheless its use in high power applications lead to significant energy loss. Further improvement of efficiency can be reached analyzing in more detail the different sources of power losses within the transmission system. These losses can be classified into two groups, load-dependent and load-independent. Whereas the load-dependent power losses have been closely studied and predictive models have been already developed, on the contrary the fluid-dynamic losses require further analyses. There are many sources of such losses, but the primary ones are related to the windage, the oil squeezing due to the gear meshing and oil churning. The relative magnitude of these mechanisms varies depending on the application. The objective of this work is to study the meshing losses by means of CFD simulations. A gear pair has been analyzed, representing an experimental test available in literature. Transient RANS calculations have been performed, exploiting two different numerical approaches. The influence of the rotational speed on the fluid-dynamic resistant torque has been investigated, then the flow and pressure fields associated with the gears motion have been evaluated. The results are compared to experimental data in order to validate the most appropriate modelling.

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