Rohit Sharma, Vinay Kumar Gupta, Alok Khaware, Vinayak Kamat
Abstract: Electric vehicles show a great potential to decrease carbon emissions as compared to traditional internal-combustion engine-based vehicles. An electric motor is one of the most important components of the electric vehicle, which decides the overall performance of the vehicle. A proper cooling mechanism of the electric motor is critical to achieve its optimum performance, safety and reliability. Oil-cooled electric motor designs are frequently utilized in high-power density automotive electric motors. A commonly used electric motor design concept involves a hollow, rotating shaft with holes that supply oil to different motor parts for cooling. Design optimization of rotating shaft is crucial to ensure the required flow distribution for effective cooling. Shaft design optimization involves multiple flow rates, rotational speeds, and geometric parameters. Multiphase flow with length scales varying from a meter to less than a millimetre and high rotation speeds up to 25,000 rpm pose additional challenges in the design analysis and optimization. Traditionally, experimental methods or flow and thermal network modelling have been utilized for such design optimization studies, but all these methods have their well-known limitations. Therefore, the use of CFD-based design optimization is required for detailed physics-based numerical modelling of realistic geometries. It is crucial to develop an efficient solution methodology for fast and accurate analysis. A steady-state CFD solution methodology is developed to simulate the two-phase flow physics in a rotating shaft using the Volume-of-Fluid method. The solution developed for this application uses the pseudo-transient method and several other numerical recipes to increase the solution accuracy and robustness. The proposed approach is validated against the experimental data for two-phase flow physics in a horizontal rotating shaft with twin exit branches. A benchmarking is also carried out against the traditional full transient approach, and a significant improvement in the turnaround time is observed. A well-integrated and automated workflow is demonstrated for design sensitivity analysis. Overall, the proposed modelling approach allows for a fast, accurate, and robust design analysis, thus making detailed design optimization feasible.
Keywords: Electric Motor, Hollow Rotating Shaft, High Rotational Flow, VOF, Pseudo-Transient, PIDO
Date Published: August 2, 2022 DOI: 10.11159/jffhmt.2022.009View Article