An electrical drivetrain incorporates power electronics to convert the DC voltage provided by the batteries to an AC waveform to drive the electric motor. To develop electric vehicles with a higher driving range, these components need to become more compact and efficient. One of the challenges of the motor design is to increase the ability to evacuate the motor losses from the system. Highly performant cooling techniques are a necessity to increase the electric motor power density.
Conventional electrical traction motors for automotive applications are usually equipped with a water jacket to evacuate heat form the motor. Although the water-jacket is cost effective and well performant, its main drawback it the high thermal resistance between the water and the main heat source (the windings). By use of a dielectric fluid, such as oil, the fluid can be contact with the copper winding and as such significantly reduce the thermal resistance between the coils and the fluid. One of such direct stator cooling method is ‘oil jet cooling’. In this concept the oil jet is impinged on the end-winding of the electric motor. Although frequently implemented in existing electric drive trains (such as Tesla Model 3), the modelling of oil jet cooling is a challenge.
Figure 1: End winding jet cooling setup (NREL Jet Impingement Cooling of electric machines - 2019)
The goal of this master thesis is to model and analyze the performance of such an oil jet on a rectangular wire. In a first part, a study will be made to investigate the different modelling techniques in the literature. Secondly, a two-phase oil jet will be modeled in a CFD software package (Ansys Fluent or OpenFOAM). The wire geometry and the model boundary conditions will be provided by Dana. The model accuracy will be estimated by performing mesh sensitivity studies and turbulence models. In the last part of the project, the jet design and operation points can be optimized.