Numerical simulation of jet cooling method inside air gap in a high-power permanent magnet synchronous motor

High-power permanent magnet synchronous motor (PMSM) has great application potential in the field of traction or propulsion. Since the compact structure and high heat load density of PMSM, heat dissipation conditions introduce new challenges and opportunities for further improvement of its power, efficiency and reliability. In this paper, a new gas–liquid two-phase jet cooling system (GLCS) for PMSM is proposed. The flow and heat transfer characteristics of GLCS are studied numerically. The effects of different factors on heat and mass transfer characteristics were studied. It lays a foundation for the development of thermal analysis and thermal design of high power density permanent magnet synchronous motors with wide application prospects in high-speed rail, urban rail and electric vehicle traction systems. The results show that the surface temperature of stator and rotor can be below 350 K, which proves the heat dissipation capacity of the cooling system. The closer the jet area is to the surface of the rotor, the smaller the velocity is. The surface temperature of stator and rotor is distributed in a W-shape. The effect of liquid volume fraction on different surfaces is different. On the rotor surface, with the increase of liquid volume fraction, the cooling effect is enhanced, while on the stator surface, the cooling effect is weakened. When the rotating speed is 4200 r min⁻¹, the jet cone angle is less than 60°, which can ensure the heat dissipation capacity of the cooling system. The axial influence distance of jet velocity on the surface temperature of rotor is 40 mm. The number of circumferential nozzles is 3 and the number of axial nozzles is 6, which can ensure the best heat dissipation capacity of GLCS.