Water cooling structure design and temperature field analysis of permanent magnet synchronous motor for underwater unmanned vehicle

Unmanned underwater vehicles (UUVs) have extremely harsh cooling conditions for permanent magnet synchronous motor (PMSM) due to global sealing and compact space, and an efficient heat dissipation system is essential for the safety and operational reliability of PMSM. Currently, with the introduction of seawater and the addition of heat exchanger, liquid reservoir are typically used for open-circuit heat dissipation, which not only adds weight, but seriously affects the flow characteristics of the UUV. In this paper, a novel dual channel water cooling structure is designed to achieve internal circulating heat dissipation without additional auxiliary devices. The temperature field of the PMSM with different water cooling structures is solved by Computational Fluid Dynamics (CFD) under rated operating conditions. The results show that the cooling efficiency of water cooling structures is more affected by low flow rates, accompanied by increasing the flow rate from 0.5 L/min to 24 L/min, the cooling performance is enhanced, but does not entirely obey a strict linear variation. Furthermore, at a flow rate of 6 L/min, the dual spiral water cooling structure performs the best heat dissipation, the maximum operating temperature of the PMSM is reduced by 51.72 K, the maximum temperature rise suppression rate reaches 53.02%, and the minimum differential pressure of 10.18 kPa.