Effiziente CFD-Simulationen zur Berechnung des Schleppmoments nasslaufender Lamellenkupplungen im Abgleich mit Prüfstandmessungen

Wet-running multi-disk clutches and brakes are an important component of modern powershift transmissions and industrial drive trains. In the open state, drag losses occur due to fluid shear, which are among the load-independent losses. The goal of development is to reduce these losses. This requires a detailed knowledge of the flow conditions in the clutch in order to identify the formation and influencing factors of the losses and, in a further step, to make the design of future clutches loss-reduced. This article presents an evaluation method for drag torque at the FZG drag torque test rig LK-4. Furthermore, a stationary, isothermal simulation model, which is implemented in the commercial CFD-Software SimericsMP+, is presented. The CFD-Model includes the geometry of a complete clearance for the calculation of drag moments. First, the oil capacity of the open clutch and the drag torque in the linear range are calculated by means of a single-phase flow simulation. The drag torque of operating points in the subsequent non-linear range are calculated using a cavitation model. The presented 3D simulation model for the prediction of the drag torque of a wet-running multi-disk clutch shows promising results in comparison with measurements on the component test rig LK-4. The trend of the calculated drag torque is well reproduced qualitatively and quantitatively. The influences of changes in operating conditions, oil injection temperature and volumetric flow rate are shown both in the measurements and in the simulation results. Due to the short calculation times, the simulation model is a good way of estimating the drag torque of a clutch at an early stage of development. Furthermore, the calculation times help with the holistic development of the model. The effects of model changes can be assessed after a short time based on a complete differential-speed-drag torque curve.