车用动力电池系统热场分布、热传输机理及热管理研究

With the goal of "ultra-safety - long-life - high-performance" for vehicle power batteries thermal management in the whole process, the understanding of thermal behavioral mechanism, thermal design method, and thermal control theory will be certainly deepened, from the configuration to the mechanism, and then to the control method. From the thermal behavioral level, electrochemistry and thermal science will be utilized to analyze heat production from a microscopic view and so is heat production, heat transfer and heat dissipation of macro heat source groups. Multi-modal, multi-dimensional, multi-scale, multi-conditional, multi-coupling thermal behavior mechanism is going to be studied further on. Then the characteristics of function, thermal and controllability under space-time factors will be quantified, revealing the coupling of space-time changes, electrochemical thermal state with macroscopic performance and so is the temperature control requirement with boundary features of process evolution, aging decay, extreme variation. Finally, a definite decoupling relationship of heat production, heat transfer and heat dissipation, as well as thermal field distribution shall be acquired, and the model and online prediction are expected to be realized. From the thermal design level, the elaborated boundary conditions for the thermal demand of battery cells and packs will be analyzed, designed and defined firstly. The intrinsic relationship between system and battery temperature variation, uniformity and responsiveness are going to be revealed then, to establish design indicators and evaluation methods. From the thermal control level, by studying the temperature control with the objective to achieve the maximum available power, a thermoelectric safety strategy and overheat prevention mechanism for the whole process based on thermal runaway prediction model are going to be constructed, aiming to achieve thermal management coordinated control under complex working conditions and constraints, laying scientific foundation for technical advancement of battery system.

以车用动力电池全过程热管理“超安全-长寿命-高性能”为目标，从构形到机理，再到控制机制，深化热行为机理、热设计方法和热控制理论认知。其中，热行为层面，利用电化学与热学等分析微观产热和宏观热源组群的产热/传热/散热，解析多形态、多维度、多尺度、多工况、多耦合热行为机理，量化时空因素作用特征、热力特性及其控变性等，揭示时空变化-电化学热状态-宏观性能耦合关系，揭示进程演变、老化衰变、极端异变等温控需求和边界特征，明确生产热/传热/散热解耦关系和热温场分布规律，建立模型与在线预测。热设计层面，设计分析并界定电池组各单体/组态热力完善需求的边界条件，揭示系统与电池组温变性、温均性、响应性等内在关系，建立设计指标及评测方法。热控制层面，研究最大可用能量温度优控，构建基于热失控预测模型的“全过程”热电安全策略和过热防控机制，实现复杂工作条件和约束条件下热管理协同控制，为电池系统技术进步奠定科学基础。

本项目围绕车用动力电池全过程热管理“超安全-长寿命-高性能”为目标，从构形到机理，再到控制机制，深化热行为机理、热设计方法和热控制理论认知。为了全面评价多变复杂行车工况下热管理过程温控性，利用动态工况电池热管理协同仿真方法构建了一维车辆动力系统模型，三维动力电池单体电热模型和三维动力电池模组热流传输模型。为促进液流循环和风冷对流换热优势集成，实现流固传热局限性分析及其拓展，围绕气动液冷混流式电池热传输增效开展研究。通过提升电池模组离散空间的气流压力梯度，提高电池离散空间气流量和气流速，强化了混流电池热管理气动冷却能力。联系电动汽车实际行驶工况，设定压缩机与电子膨胀阀调节条件，仿真研究了电池直冷过程温控能力可变调控机制。认知分析设计工况中制冷剂恒压变流和恒流变压调节方式对直冷板压降、板壁换热、板壁温降与电池模组热管理温控动态变化特性，界定了动态行驶车速边界下直冷电池温控调节的制冷剂压流联动时变范围幅度，并从短时温均增效角度优选适宜斜率特征，为热泵一体化系统集成热管理温控方案设计提供设计方法。在研究直冷集成系统的耦合关联关系基础上，进一步考虑电池全生命周期性能衰变特性，探索其与直冷热管理的作用关系和规律。考虑常规老化构建电池衰变模型，在印证合理有效的热管理措施有助于延长电池寿命的基础上，协同热管理系统寄生能耗的不利影响，提出并解决了电池热管理目标温度的优化问题。利用前馈+反馈的综合控制思想，选取电动汽车在NEDC循环行驶工况为实验背景，设计出一套基于多信号输入的综合压缩机调控方案，实验结果标明，与恒定较高转速方案相比，综合控制方案的能耗有明显的降低，说明综合控制方案在满足实验工况的热管理需求的同时，也具有一定的节约能耗优势。