Numerical Study of Oil Jet Cooling in Electric Traction Motors with
Hairpin Windings
Abstract
Hairpin winding technology, combined with direct oil jet impingement
cooling, is a viable solution known to increase volumetric power density
and efficiency in the next generation of traction motors. However, the
coolant fluid interaction with the complex winding geometry has not yet
been fully examined; specifically, with the use of high-fidelity CFD
simulations. Thus, the present work investigates the radial and axial
oil impinging jets in a hairpin winding motor using multi-phase
simulation. The study first analyses power losses and temperature
distribution of the motor under the Worldwide Harmonised Light Vehicle
Test Procedure (WLTP). Next, the performance of axial and radial jet
impingement is numerically analysed by considering the fluid flow.
Finally, the two configurations are compared in terms of their oil film
formation rate. The results indicate that the maximum power losses
observed in typical driving conditions are considerably lower than the
maximum losses predicted for the complete operational region of the
motor. Moreover, the axial impinging jet shows a higher oil film
formation rate compared to a radial jet impingement configuration within
the examined conditions.
Manuscript accepted to publication in WEMDCD 2023 IEEE conference.
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