移动装置内燃机余热回收CO2动力循环多能流耦合关键问题研究

Waste heat recovery from Mobile Internal Combustion Engine has important values. Aiming at new bottoming cycle which suits the characteristics of waste heat and meets the requirements of high recovery efficiency, down-sizing as well as light weight, this research project proposes to apply CO2 power cycle system for recovering the waste heat from Mobile Internal Combustion Engine considering its advantage on recovering waste heat with large temperature gradient and varying transient property, as well as on heat transfer in micro-channels and expansion process in small size. The CO2 power cycle further couples the ICE through the integration design of super-critical CO2 to exhaust gas heat exchanger and muffler, as well as the expander gearing to engine with variable speed ratio. Based on theoretical analysis and experimental research, this project focuses on the following four parts: The research about coupling rules between CO2 power cycle mode and waste heat characteristic from Mobile Internal Combustion Engine; The research about multi-fields coupling mechanism and its enhancement method during micro-scale and high-enhanced heat transfer process. The research about the transient expansion process of super-critical CO2 at the micro-scale and feedback mechanism of power output; The research about quick response and cooperative control for recovering energy from varying transient heat source with high efficiency. Through researches above, the complete theory of CO2 power cycle system from the matching of cycle structure and the optimization of core thermodynamic process to the operation at whole working conditions with high efficiency is expected. This project enriches and develops the theory of waste heat recovery form Internal Combustion Engine, which shows important scientific significances as well as practical values.

移动装置内燃机余热回收具有重要意义，为获得适应其余热特性，同时满足高回收效率和小型轻量化要求的新型底循环回收系统，本项目提出了移动装置内燃机余热回收CO2动力循环系统，充分发挥其适应移动装置内燃机品位梯度大、瞬态脉动的余热特性，同时又适合微通道换热和小型膨胀过程的特点，并通过超临界CO2烟气换热/消声一体化和膨胀机变转速比传动装置设计，进一步与内燃机进行耦合。基于理论分析和试验测试，本项目拟开展以下四个方面研究：新型CO2动力循环模式与热源特性的耦合规律研究；微尺度高强化换热过程中的多场耦合机理及强化方法；超临界CO2流体小尺度瞬时条件下膨胀过程及输出能量反馈机制研究；与瞬变脉动余热协调的系统高效运行动态响应和协同控制研究。通过系统研究，期望获得CO2动力循环从循环结构匹配、关键热力过程优化到系统全工况高效运行的理论和方法。本研究丰富和发展了内燃机余热回收理论，具有重要科学意义和实用价值。

针对移动式内燃机余热回收，本项目提出CO2动力循环的底循环技术路径，以期实现余热高效回收、瞬变工况高效运行、小型化的协同目标。为此，从循环匹配、换热强化、膨胀机理、系统控制等四个角度开展了深入研究。本项目按预定计划完成了项目制定的研究内容：1）揭示了CO2工质与移动式内燃机高低余热源的耦合匹配规律，提出了设计点及面工况余热高效回收的分流匹配循环设计方法，自主研制分流式CO2动力循环试验样机；2）获得了移动式内燃机CO2-烟气换热器综合评价方法，以此完成换热器的优化设计，首次提出印刷板式CO2-烟气换热器，开展了换热-消声-后处理耦合的小型化换热器探索；3）提出部分进气轴流涡轮气动的小型CO2膨胀机方案，揭示了超临界CO2膨胀机内部流动机理，建立了超临界CO2高速小型膨胀机的设计理论与方法；4）基于实验样机，开展了循环动态特性测试，并获得高精度动态仿真模型，提出了道路工况下分层次、模块化高效回收控制策略。基于本项目提出的CO2动力循环技术，与潍柴开展了相关的技术应用开发项目。所开发CO2动力循环系统，最大输出功率为11.3kW，实现发动机有效热效率提升3.52%。通过本项目的开展，共发表SCI论文40篇，EI论文10篇，SCI他引632次，1篇入选ESI高被引论文；受邀为PECS（IF=29.39）撰写综述论文；申请发明专利20项，授权3项；在学术会议做大会邀请报告2次。共计培养博硕士研究生13名，包括中国汽车工程学会和内燃机学会优博共4名，第一参与人获2021年国家优秀青年基金。本项目成果作为重要科学发现之一，支撑项目负责人以第一完成人获2020年国家自然科学二等奖。