Electromagnetic-thermal coupled analysis of in-wheel motor with NSGA-based optimization water cooling structure for electric vehicle application

Traction motors with high power density are prone to excessive temperature rise, which negatively affects performance and reliability, making effective thermal management essential. In this study, a spiral water-cooling channel integrated into the stator support of an in-wheel motor is proposed to suppress temperature rise while maintaining acceptable hydraulic losses. Using computational fluid dynamics (CFD) with the finite volume method, the three-dimensional temperature field and flow characteristics of the motor cooling system were analyzed. A multi-objective optimization of the cooling structure is performed using the non-dominated sorting genetic algorithm II (NSGA-II), with winding temperature, inlet–outlet pressure difference, and surface heat transfer coefficient (HTC) selected as optimization objectives. The results show that the optimized spiral cooling structure reduces the maximum motor temperature by 4.23°C. The optimal design consists of four spiral water channels with a cross-sectional height of 10.3 mm, a width of 11.4 mm, and an inlet flow velocity of 1.05 m/s, achieving a balanced compromise between thermal effectiveness and hydraulic efficiency. Experimental validation conducted on a single-motor test platform demonstrates good agreement with the numerical results, confirming the feasibility and effectiveness of the proposed cooling strategy.