Abstract

Over the next decade, e-drive units for Hybrid and Electric traction will continue to evolve towards the industry-specific requirements: increase in power density, efficiency improvement, cost reduction, reliability. On the other hand, the EVs and hybrid platforms are expected to become mainstream even for less expensive cars with high production volumes placing even more pressure on the cost of materials and process for the e-drives. Thermal management of the e-drive is a crucial factor affecting both the performance and life. Internal spray cooling concepts are already used by several players in the automotive and transportation sector in order to cool down the e-drives components with impressive results. Even more, the growing integration of the e-drive and transmission units allows for the use of the transmission fluid to be used as the coolant in the e-motor. The development of this type of cooling is still very dynamic with multiple players exploring the limits of this technology (see recent patents). Nidec-PSA e-Motors joint venture took on the challenge of developing and producing high-performance and competitive e-motors, bridging e-Motor design and manufacture know-how and automotive expertise together in a very ambitious enterprise. The company has adopted simulation techniques since the early stages of the development process to drive the thermal design of their line of e-motors and to predict and optimize the motor temperature. This presentation will focus on the simulation of oil distribution system in the motor, and its use on predicting the heat removal and temperature distribution in the motor. Fast comparison of different concepts and the choice of the best design solution is done by running mesh-less CFD simulations using the Moving Particle Simulation method, which is ideal for simulating oil splashing and jet impingement phenomena in the e-drive. In this presentation engineers from Nidec PSA emotors and EnginSoft will explain the simulation process that allows inspecting virtual prototypes of the e-drive. In the first part, the coolant flow rate and distribution in the cooling channels are predicted for different load cases and flow rate conditions. In the second part, the coolant particles trajectory and heat transfer coefficient on the parts to be cooled are calculated considering the influence of air flow inside the motors. Lastly, the coupling between mesh-less CFD and thermal calculation allow the prediction of critical electrical components temperatures. The results of this procedure and the validation of the numerical results are presented and explained.