柴油机排气低品位余热TEG-SCR耦合系统能量供求自洽机制研究

Thermoelectric Generator (TEG) is introduced in order to realize energy recovery of engine exhaust low-grade waste heat and boost energy supply for exhaust system when atomization and decomposition of urea aqueous solutions become insufficient in SCR system, realizing energy supply-demand self-consistency and closed-loop for exhaust system. Based on target optimization method, parametric contributions and comprehensive influence mechanism for efficient thermoelectric conversion of TEG modules is explored. Multi-field coupling model of TEG-MPPT-CB energy storage system is established, energy gradient distribution and characteristics of energy transfer and storage in the system is revealed. Thermogravimetric characteristics and change regularity of real-time evolved gas for urea aqueous solutions in SCR system are researched, the physical and chemical model of decomposition for urea aqueous solutions is established and the causes for deposit formation are analyzed. The time-space characteristics of urea aqueous solutions particle swarm in the process of liquid-gas phase transformation, energy transfer and mutual interference effects for particle swarm with exhaust are studied. The characteristics of dynamic equilibrium between continuous energy storage of the energy storage system and intermittent energy supply of the SCR system are researched. Energy distribution rule and mechanism of energy supply-demand self-consistency for the TEG-SCR coupling system are analyzed, realizing its closed-loop thermal management. This research lays a theoretical foundation and scientific basis for improving decomposition capacity of urea aqueous solutions and avoiding the formation of its deposit in the SCR system by TEG initiated by diesel engine exhaust heat.

利用TEG对柴油机排气低品位余热进行能量回收，在SCR系统尿素水溶液粒子雾化分解不良时对排气系统进行能量补给，实现排气系统能量供求自洽及闭环热管理。基于目标优化法探寻TEG模块热-电能量形式高效转换的参量贡献度及综合影响机制，建立TEG-MPPT-CB储能系统多场耦合模型，揭示储能系统能级梯度分布、能量传递及存储特性；研究SCR系统尿素水溶液热重特性及实时逸出物变化规律，建立尿素水溶液分解理化模型并剖析结晶成因，探索水溶液粒子群在排气中的液-气相变时空特性及与排气的能量传递和互扰效应；研究储能系统能量不间断存储及SCR系统能量间断补给的动态平衡特性，解析TEG-SCR耦合系统能量分布规律和供求自洽机制，实现系统级闭环热管理，为利用柴油机排气余热TEG有效提升SCR系统尿素水溶液分解能力、避免结晶奠定理论基础和科学依据。

利用温差发电技术对低品位余热进行能量回收，基于目标优化法探寻了TEG模块结构参数对其伏安特性的影响规律，研究了冷热端热边界条件及电路动态负载对输出电压、电流、功率及效率的影响规律，揭示了Peltier效应对TEG热电能量转换过程中的电热逆向效应，以及由此效应引发的TEG输出性能偏移及衰减规律；建立了TEG-MPPT模型，发现MPPT介入可在较大边界温度和负载变化范围内有效保证温差发电系统的最佳输出状态；搭建了高温波动热源-相变材料-温差发电能量回收系统，开展了PCM结合TEG进行能量回收的研究工作，系统论证了PCM对高温热源的温度波动抑制效应，及其储能和传热特性对TEG输出性能及系统能量回收的影响，建立了TEG不同冷端散热强度时PCM与TEG联合系统能量存储与转化的动态关系，实现了系统余热利用效率提升和TEG稳定运行的双重目标；详细研究了不同结构气助式喷嘴在不同喷射条件时形成的喷雾液滴尺度变化和空间分布特点，结合液滴碰壁原理和传热学理论梳理了喷雾碰壁过程中壁面温度的瞬态变化特性和液滴群发生铺展、反弹及破碎等效应的区分机制；总结了喷射粒子撞壁时粒子流的时空特性及撞壁后形成液膜和结晶的规律，对柴油机不同运行工况时形成的尿素水溶液结晶成分进行了详细分析；探寻了SCR后处理系统降低柴油机NOx排放时排气温度、流量和喷嘴形式、布置方案及尿素水溶液喷射压力、喷射量等因素对NOx转化效率的影响规律。