Experimental and numerical analysis of the multiphase flow distribution in multi plate wetclutches for HVT transmissions under actual operating conditions

The paper investigates the multiphase flow through the plates of multi plate wet-clutches for hydro- mechanical variable transmission in order to address the performance of the lubricating systems and its influence on the thermo-mechanical stresses on the plates. The lubricating oil distribution is very difficult to measure experimentally on a real geometry, therefore, a numerical model for the prediction of the flow distribution within the clutch plates is proposed. The volume of fluid approach is used to model the multi-phase flow that characterizes the component and a modular approach is defined to reproduce accurately the real geometry. Furthermore, the numerical modeling is validated against measurements carried out on an ad-hoc designed test rig. The testing facility replicates both the geometry of a real clutch and the actual operating conditions. Transparent PMMA components and fast imaging techniques are used to capture the multiphase flow pattern within the gear distributor chamber, while a 3D printed component and a specific collector system have been designed in order to reproduce the disks position and measure the oil distribution through the plates' clearances by varying the working conditions. A good agreement between the numerical and the experimental results was found and the analysis highlighted the importance of modeling the multi-phase nature of the lubrication process for the accurate prediction of the oil distribution within multi plate wet-clutches.)