机-热电转换系统的多场协同强化机制及多学科设计优化

Machine-thermoelectric system refers to a system that can transfer waste heat generated by the working process of engine into electric energy by thermoelectric conversion device directly. It has a wide range of applications, but there are also the problems of low efficiency, low power density and high price. This project is set in a thermoelectric conversion system for the exhaust heat from automobile engine. It's used in the multi-field coupling strengthening mechanisms study for the high-power thermoelectric conversion system and designing optimizatioin. By taking the form of heat transfer enhancement of heat exchanger and circuit network of thin-arm thermocouples,the voltage of conversion element was constant. The electrical and thermal resistance was also reduced. So that the thermoelectric conversion efficiency was improved synthetically and the structural parameters of a high-performance thermoelectric generation system was obtained by the collaborative strengthening mechanisms of flow-thermal -electric field. Based on the form of hot pulsating flows and the transmission characteristics of pipeline, we analyse fluid-solid coupling, effects coupling, thermoelectric coupling and resistance coupling of the subsystem, set up a multi-field coupling mathematical model for energy conversion and gain the accurate parameters of system performance. The designed structure matrix was used for planning and restructuring optimization task of the target cascading. It can help us solve the problems of information exchange about multi-service and collaborative optimization, so that it would provide the theory, method and technical support for the design and optimization of the thermoelectric conversion system, and a kind of new technology for automotive energy-saving.

机-热电转换系统是指机械装置工作过程中产生余热，由热电直接转换装置转换为电能的系统，有广泛的应用前景，但也存在效率低、输出功率小、价格高的问题。本项目以汽车发动机排气余热的温差发电系统为背景，研究大功率机-热电转换系统的多场协同强化机制和设计优化问题，拟采取换热器强化传热和薄臂型热电偶回路网络解耦技术，使转换元件的电动势不变而降低电阻和热阻值，综合提高热电转换效率；通过流-热-电场协同强化机制，获得高性能温差发电系统的结构形式；针对脉动排气的热流体形态和管道传输特点，从子系统的热流固耦合、效应耦合、热电耦合、部件阻力耦合特性分析出发，建立全程排气系统能量转换的多场耦合数学模型，获得准确的系统设计参数；采取多学科设计优化方法，用设计结构矩阵对目标级联的优化任务进行规划和重组，解决信息交互规划和协同优化问题。为机-热电转换系统设计优化提供理论、方法及技术支持，为汽车节能提供新技术。

机-热电转换系统是指机械装置工作过程中产生余热，由温差发电装置转换为电能的系统，它的基础理论是热电效应，核心技术涉及机电科学、传热学、材料科学等多个学科的协同配合。热电转换有着广泛的应用前景，但目前存在转换效率低、输出功率小、体积不紧凑以及价格高的问题。.本项目以发动机排气余热的温差发电系统为对象，研究了大功率机-热电转换系统的多场协同强化机制和设计优化问题。主要研究内容为：针对排气系统的热流体形态和传输特点，建立能量转换的多场耦合数学模型和计算方法；采取多学科耦合设计优化的方法，设计高性能温差发电系统的结构形式；仿真及实验分析紧凑型温差发电器的温度分布和应力特性，以及热电转换元件的最优阵列形式；研究热电偶回路的强化原理及协同热电转换形式。研究的主要结果包括了建立温差发电系统的流-热-电场的协同强化机制，通过优化设计总结出了1千瓦级紧凑型温差发电器的最优参数组合，进而提出了基于强化传热管（排）结构的温差发电器的设计方法和设计准则、大功率温差发电系统的组成方案、以及温差发电器的热流体加热系统的可行性方案。提出了基于硅基PN结的热电转换器件的基本原理和结构形式的研究（继续进行中），目标是通过半导体PN结在热电偶回路中的设置，大幅度地提高热电转换过程的热电动势和系统的协同特性，推动热电转换系统的实际应用。