3-D CFD Simulation of Oil Flow and Heat Transfer in an Electric Drive Unit

The Electric Drive Unit (EDU) for electric vehicles has high power density and unavoidably generates considerable waste heat during its operation. Thermal management of the Electric Drive Unit is crucial for its reliable, optimum operation. This demands efficient cooling technology. Computation Fluid Dynamics (CFD) simulation as a virtual test bed, provides detailed insights into the flow, and temperature fields which help in making the necessary design changes for better thermal performance of Electric Drive Unit at the product development phase. The present work deals with the prediction of temperature of the windings during the warming up cycle using a fast and novel coupled heat transfer approach. A 3-D, quasi-steady state, and transient, multiphase flow with conjugate heat transfer model of Electric Drive Unit is simulated in Simerics-MP+, a CFD software. The 3-D model of the drive unit consists of an e-motor with all the primary parts such as windings, end rings, stator, rotor laminate, shaft, and transmission gears. The oil distribution inside the motor is predicted using an explicit Volume of Fluid (VOF) formulation for multiphase flow with high resolution interface capturing between oil and air phases for proper oil distribution. The oil splashing due to gear rotation is also captured in the simulation. The quasi-steady state and transient evolution temperature field of the motor is predicted with the conditions as considered in the experimental setup. The predicted temperature of the windings is compared with experiment measurements at 29 different locations and the comparison is good.