【作者】 孙健；

【导师】 何莉萍； 田永；

【作者基本信息】 湖南大学 ， 车辆工程（专业学位）， 2020， 硕士

【摘要】 随着我国能源安全和环境污染的问题日益严重,电动汽车产业迎来了高速发展的机会,目前世界各国都对电动汽车的研发展开了激烈竞争。在电动汽车中,电池包是其核心部件,它对电动汽车的续航里程、动力特性、安全性能影响巨大。由于电池包中的锂离子电池在工作过程中会产生大量热量,使电池温度不断上升,若不能有效对其进行散热,会严重影响锂离子电池的工作状态和循环寿命,长时间使用甚至会出现热失控的现象。为了保证电池包的安全,就需要设计电池热管理系统。此外,电动汽车行驶过程中会遇到一些极端工况,作为电池载体的电池包箱体,对动力电池稳定、安全的工作起到非常关键的作用,因此研究动力电池包的箱体结构也十分重要。本文基于计算机仿真技术,以动力电池包为研究对象,主要对电池包的液冷散热系统以及箱体结构进行了以下几个方面的研究:(1)对锂离子电池的结构组成,工作原理,产热机理和传热方式进行了深入研究,建立了电池单体的热效应模型。之后基于计算流体力学的理论,应用Fluent软件对电池单体1C、2C、3C和4C倍率放电时的温度场分布进行了仿真分析。结果表明电池单体的温度从其中心向四周不断降低,并且随着电池放电倍率的增大,电池内部的峰值温度和最大温差也不断升高,超过了电池能够适应的正常工作温度范围,需要对电池进行热管理。(2)构建了电池模组的三维模型,并对其进行了热仿真分析,结果发现当环境温度为25℃,电池以2C倍率放电时,模组内电池的最高温度为60.61℃,最大温差为8.5℃,远远超过了电池的最佳工作温度。因此对模组的结构进行了优化,设计了电池液冷散热系统,并分析了不同冷却板数量、冷却液入口温度以及环境温度对模组散热的影响。仿真结果表明优化后电池模组最高温度仅为27.44℃,最大温差为4.85℃,相比自然对流散热的模组结构,优化后的电池模组最高温度降低了54.7%,最大温差降低了42.9%,满足了锂离子最高温度不超过40℃,最大温差不超过5℃的设计要求。(3)基于动力电池包的机械安全和轻量化设计要求,对电池包的上盖和下箱体等部件进行了材料遴选和结构设计,并根据优化后的电池模组结构,建立了动力电池包的液冷散热系统。之后采用有限元分析方法,在ANSYS软件中对动力电池包进行了极限工况下的静态分析和动态分析。仿真结果表明动力电池包的一阶固有频率为69.71Hz,其在极端工况下的最大应力为126.73MPa,最大应变为1.063mm,满足电池包强度和刚度的设计要求。更多还原

【Abstract】 With the increasingly serious problems of energy safety and environmental pollution in China,the traditional automobile industry has come to a revolutionary opportunity.In order to achieve the goal of sustainable development,electric vehicles have become the mainstream development direction.At present,the research and development of electric vehicles are facing fierce competition all over the world.As the core component of electric vehicle,power battery pack has a great influence on the range and safety performance of electric vehicle.Because lithium ion batteries in the battery pack generate a lot of heat during the charging and discharging process,the temperature of the batteries keeps rising.Failure to effectively heat them will seriously affect the working state and cycle life of the lithium ion batteries,and even lead to thermal runaway phenomenon during long-term use.To ensure the safety of the battery pack,a battery thermal management system needs to be designed.In addition,the electric vehicle will encounter some extreme operating conditions during driving.The battery package as a battery carrier plays a key role in the stable and safe operation of the power battery.Therefore,it is very important to study the box structure of the power battery package.Based on computer simulation technology and taking power battery package as research object,this paper researches on the following aspects of battery liquid cooling heat dissipation system and battery package structure:(1)The structure,working principle,heat generating mechanism and heat transfer mode of lithium ion battery were studied in depth,and the thermal effect model of battery monomer was established.Then,based on the theory of computational fluid dynamics,the temperature field distribution of cell monomer in 1C,2C,3C and 4C rate discharge was simulated and analyzed in Fluent software.The results show that the temperature of lithium ion batteries decreases from the center to all sides,and the peak temperature and maximum temperature difference inside the batteries increase with the increase of discharge rate,which exceeds the normal operating temperature range for the batteries and requires thermal management of the batteries.(2)The three-dimensional model of the battery module was established and the thermal simulation analysis was carried out.The results show that when the ambient temperature is 25℃ and the battery is discharged at 2C multiple,the maximum temperature of the battery in the module is 60.61℃ and the maximum temperature difference is 8.5℃,which far exceeds the optimum operating temperature of the battery.Therefore,the structure of the battery module is optimized and the liquid cooling and heat dissipation system of the battery is designed.The influence of number and position of cooling plates on module heat dissipation is analyzed.The simulation results show that the maximum temperature and maximum temperature difference of the optimized battery module are only 27.44℃ and 4.85℃.Compared with the module structure of natural convection heat dissipation,the maximum temperature and maximum temperature difference of the optimized battery module are reduced by 54.7% and 42.9%,which fully satisfy the design requirements that the maximum temperature of lithium ion in the module does not exceed 40℃ and the maximum temperature difference does not exceed 5℃.(3)Based on the design requirements of lightweight power battery package and mechanical safety performance,the upper cover and lower box of power battery package are designed in structure,and the liquid-cooled heat dissipation system of power battery package is established according to the optimized battery module structure.Then,static analysis and dynamic analysis of power battery pack under limit condition are carried out in ANSYS software by using finite element analysis method.The simulation results show that the firstorder natural frequency of the power battery pack is 69.71 Hz,and its maximum stress and strain under extreme conditions are 126.73 MPa and 1.063 mm,which meet the design requirements of the strength and stiffness of the battery pack.更多还原