Heat Transfer Research and Optimisation of Spray Oil Cooling System for IPMSM in EVs

With the increasing demand for high power density in motors for electric vehicles, an effective cooling structure directly impacts the safety and stability of motor operation. To improve the cooling effect of the electric drive system, a novel triple‐spray oil cooling structure for the winding end was proposed. This paper focuses on the heat transfer research using CFD‐thermal coupling evaluation for a 60 kW, 6000r/min interior permanent magnet synchronous motor (IPMSM). And it was investigated with a multi‐objective optimisation method based on Strength Pareto Evolutionary Algorithm II (SPEA‐II). FEM was adopted to perform fluid‐solid coupled heat transfer calculation for the IPMSM. In the paper, it was analysed of the variation trends of cooling structure pressure, winding end pressure, and the maximum temperature of motor with different inlet velocities. By comprehensively selecting the inlet velocity, the heat dissipation characteristics were summarised. Furthermore, a multi‐parameter sensitivity of the cooling structure was conducted, and an optimisation method was researched with response surface methodology. Based on SPEA‐II algorithm, the optimal solution for the four parameters of the oil cooling structure was determined. Moreover, the multiphase flow characteristics and thermal field distribution of the motor before and after optimisation were comparatively analysed. The results indicate that the maximum temperature after optimisation is reduced by approximately 10%–20% under both operating conditions of the rated speed and peak speed. Finally, the prototype and platform were built for the temperature rise experiments. It was verified the accuracy of the simulation calculation and the rationality of the multi‐objective optimisation method. This research provides valuable insights into heat dissipation in motors and optimisation analysis.