非均匀温度场下汽车尾气热电发电系统多场耦合建模与性能优化

According to the statistics, two thirds of the automobiles fuel combustion energy is lost and diffused as heat, and 40 % of the heat is discharged to the atmosphere in the form of automobile exhaust. Effective re-using of the waste heat from automobiles will not only improve the use efficiency of existing energy sources, but also can reduce emissions and improve the environmental quality. Utilizing thermoelectric generator (TEG) to recovery waste heat from automobiles exhaust is regarded as one of the most promising ways in the future. The multi-physics modeling and performance optimization for the automobile TEG system will be mainly investigated by this project, including revealing the physical mechanisms of heat transportation and electricity generation within thermoelectric materials, and the flow heat transfer mechanism under conditions of time-variability and temperature non-uniformity of heat sources; establishing the 3-D, steady and dynamic numerical model for the automobile TEG system with consideration of coupling of flow field, temperature field and electric potential field; obtaining the relationship between key structure, operation parameters and the system performance; developing the optimization method of active control in consideration of the temperature non-uniformity of heat sources, as well as an inverse multi-objective and multi-parameter optimization method to further improve the automobile TEG system performance; building an experimental apparatus to verify the numerical model and accumulate the experimental data of the automobile TEG system with various structure parameters and operating conditions. Based on the above research contents, this project can provide critical support theory and experimental data for the widely industrial applications of the automobile TEG system.

利用半导体热电发电技术可有效回收汽车燃油消耗中超过40%的尾气废热，从而提高能效并改善环境。而现有汽车尾气热电发电建模和设计中普遍忽略烟气热源、热电器件和热沉冷源之间多场耦合，导致系统性能预测与实验偏差20%以上，无法有效指导实际系统设计。基于热电内部所有能量传输与交换的本质是载流子微观传递行为的认识，本课题首先揭示载流子的微观输运机制、产热及发电机理，通过求解电子和空穴浓度建立热电单元电-热耦合模型，进而结合实际热源和冷源，建立完备的汽车尾气热电系统多场耦合模型；其次，鉴于非均匀温度分布导致系统整体与热电单元个体性能之间存在不同步性，本课题提出通过使热电单元个体性能最佳，自然实现系统整体性能最佳的“先个体，而整体”主动优化设计方法；最后，搭建汽车尾气热电系统实验平台，验证理论模型正确性以及热电结构新设计的有效性。本课题获得的主要结论能为新一代汽车尾气热电系统开发和高效应用提供参考依据。

半导体热电发电技术可有效回收汽车燃油消耗中超过40%的尾气废热，从而提高能效并改善环境。考虑汽车尾气热电系统具有热源、器件、冷源之间强耦合性，本项目首先建立了基于载流子微观传递机理的多物理场热电耦合数学模型，从发电和制冷两个层面探寻了梯度变截面型半导体结构对系统的适用性；其次，针对汽车尾气温度分均匀分布特点，从稳态和瞬态两方面探究非均匀热源影响下热电性能增强的可能解决方案和优化方式。为此，本项目将带精英策略的快速非支配排序遗传算法（nondominated sorting genetic algorithm II,NSGA – II）开发用于本项目建立的汽车尾气热电系统模型，形成了一套行之有效的多目标反问题优化方法，并围绕系统特性分别开展了串联式及分别式联合TEG-TEC系统几何结构参数优化和瞬态超冷规则波形及非规则波形操作工况参数优化的方法有效性验证。最后，本项目提出利用多孔扰流柱强化汽车尾气热源与热电器件间换热，从而提升系统性能，并开展了基于非支配排序精英决策的多参数多目标反问题优化。本课题获得的主要结论能为新一代汽车尾气热电系统开发和高效应用提供参考依据。