3D Drive Unit - Pump Coupled Model to Predict Line Pressures during Vehicle Manoeuvres

The drive unit, primarily consisting of an electric motor and a gearbox, need to be cooled and lubricated for its long life and efficient performance. In an extreme drive cycle condition, the pickup tube to the pump may get exposed to air, leading to a substantial loss in line pressure and a drop in oil flow rate to the subsystems. An advanced Computational Fluid Dynamics (CFD) simulation can provide insights into the oil delivery system and help in improving the oil sump design, optimizing the position of the pick tube to the pump and oil delivery lines. The current study employs a Volume of Fluid (VOF) based multiphase model implemented in a commercial CFD solver, Simerics-MP+. The drive unit lubrication system considered in the study consists of a gerotor pump, the entire oil delivery lines to the two subsystems and the drive unit casing. A multiphase simulation of the system with transient operation of the pump is computationally expensive. Therefore, a new methodology is implemented to reduce the runtime of such a simulation by simulating the gerotor pump separately, yet simultaneously, from the remainder of the drive unit by exchanging the flow and concentration distributions between the two computational models. The coupled methodology is first validated using a simplified system with a gerotor pump, and then the actual drive unit lubrication system is simulated for three different drive cycle conditions. The pump outlet line pressure compares well with the test data.