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Volume of Fluid vs. Cavitation CFD-Models to Calculate Drag Torque in Multi-Plate Clutches
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
Wet running multi-plate clutches and brakes are important components of modern powershift gearboxes and industrial powertrains. In the open stage, drag losses occur due to fluid shear. Identification of drag losses is possible by experiment or CFD-simulation. For calculation of the complex fluid flow of an open clutch CFD-approaches such as the Volume of Fluid (VoF) method or the Singhal cavitation model are applicable. Every method has its own specific characteristics. This contribution sets up CFD-calculation models for different clutches with diverse groove designs. We present results of calculations in various operating conditions obtained from the Singhal cavitation model and the VoF-method. Despite the high spatial resolution of the calculation models the usage of a modern commercial CFD-solver and mesher (Simerics MP+) results in very short calculation times. The developed CFD-models consider the geometry of a complete clearance consisting of the friction plate, the gap between the plates, the steel plate and the flow conditions arising from the design of the inner and outer plate carrier. The full 360-degree modeling makes it possible to take arbitrary groove designs on the friction and steel plate into account in contrast to often-used circumferential symmetry. We carried out a high number of calculations with various influencing factors such as operating conditions, groove design, speed ratio, oil temperature and oil flow rate. We proofed the numerical solutions with results from experiments. The basis of the broad validation of the models are characteristic values obtained from experimental investigations by design of experiments on the drag loss test rig LK-4. The usage of serial production parts from automobile and industrial applications ensures a data basis that is reliable and relevant for practical work. The contribution characterizes the examined CFD-approaches with respect to computing effort and validity of the results. Furthermore, it shows the possibilities and limitations as well as the pros and cons of the specific CFD-approaches to calculate drag losses of wet multi plate clutches.