轮毂电机在电动汽车中的应用标志着交通电气化的重要进步。轮毂电机提供车轮的直接驱动能力, 简化了机械传动系统, 并增强了扭矩输出的灵活性。然而, 颠簸路面激励可能会扰乱轮毂电机液体冷却系统中流体状态。该文探讨了低频大振幅的颠簸运动对轮毂电机液体冷却性能的影响。在理论分析中, 基于正弦路面定义颠簸运动, 根据Navier-Stokes方程引入与竖直方向加速度相关的附加力, 以分析冷却回路流量波动状态。在仿真分析中, 建立了轮毂电机冷却回路的一维流动方程、轮毂电机水套的三维流体模型和轮毂电机的三维热模型。通过热模型和流体模型的热-流耦合仿真分析, 获得颠簸运动过程中冷却回路瞬态流量变化和轮毂电机内部温度分布。在实验测试中, 基于已有的颠簸运动物理模拟平台, 进一步搭建轮毂电机样机的液体冷却系统, 并实验验证理论和仿真分析的有效性。研究结果说明, 在颠簸运动中, 冷却回路流量以颠簸频率波动且平均值下降, 但对轮毂电机液体冷却性能的影响有限。

Objective: With the rapid advancement of electric vehicle technology, in-wheel motors (IWMs) have emerged as a novel solution for transportation electrification because of their distributed drive characteristics. IWMs simplify mechanical transmission systems, enhance overall transmission efficiency and torque output performance, and improve vehicle torque control flexibility through force distribution control, making them ideal for navigating intricate terrain. Consequently, IWMs are increasingly applied in high-torque-density scenarios such as mining dump trucks and military tractors. Liquid cooling, characterized by its high convective heat transfer coefficient at the fluid-solid interface and the coolant's high specific heat capacity, has emerged as a crucial solution for managing thermal loads during short-term high-overload operations. This ability is crucial because IWMs are directly integrated into vehicle wheels, exposing them to more direct impacts from road vibrations compared to centralized drive systems. High-frequency small-amplitude vibrations caused by minor road deformations coexist with low-frequency large-amplitude bump motion resulting from substantial road undulations. Although tires can mitigate the effects of minor road shapes, low-frequency large-amplitude bump motion considerably affects the vertical acceleration of IWMs and their cooling systems, impacting fluid dynamics and heat dissipation performance. Methods: To assess these impacts, this research adopts advanced simulation techniques, including the finite element method for thermal analysis and computational fluid dynamics to fluid flow analysis under dynamic conditions, alongside experimental validation using a custom-designed physical simulator replicating real-world bumpy road scenarios. Theoretical models based on the Navier-Stokes equations describe the fluid behavior under bump motion by considering additional forces induced by vertical acceleration. By integrating multiphysics modeling and employing simplified 1D-3D coupling approaches, the study effectively simulates the entire cooling circuit, achieving a balance between accuracy and computational efficiency. A multiphysics model integrating electromagnetic, thermal, and fluid dynamics fields was developed and validated against experimental data obtained from the physical simulation platform. Results: The simulations reveal that under the specified bump conditions (an amplitude of 4.5 cm and a frequency of 2 Hz), the average flow rate decreases by approximately 3.8%, peak-to-peak fluctuation reaches up to 23.2%, and the IWM's maximum internal temperature increases by approximately 1.2 ℃, demonstrating a moderate yet considerable effect on the overall cooling efficacy. The experimental results show that the average flow rate decreases by 2.7% and the peak-to-peak fluctuation reaches 20.8% under bump conditions compared to those under the steady-state operation, and the IWM's maximum internal temperature is approximately 1.2 ℃. The comparison between the simulation and experimental results validates the effectiveness of the proposed multiphysics modeling and simulation. Furthermore, this paper analyzes the impact of transient bump motion on the IWM's temperature increase. The analysis reveals that during such conditions, the cooling circuit flow experiences reduced average flow and fluctuates at the bump frequency. Through fluid-thermal coupling simulations, this paper examines how varying the bump motion's amplitude, frequency, and steady-state flow rate affects these fluctuations, leading to considerable changes in IWM wall temperature increase. Increased amplitude and frequency exacerbate flow rate fluctuations and temperature increases, while higher steady-state flow mitigates these effects. Conclusions: This research highlights the importance of understanding and addressing the thermal management challenges faced by IWMs under real-world bump motion, paving the way for their broader application in the future. The insights gained from this study suggest that further optimization of cooling system designs and thermal management strategies will be crucial for enhancing the reliability and performance of IWMs in challenging environments such as bumpy roads.