基于凝结激波的喷射式非共沸有机朗肯循环

Organic Rankine Cycle (ORC) is a promising technology for converting thermal energy to mechanical power. The power consumption of the working fluid pump in small-scale ORC dramatically worsens the cycle efficiency, and hinders the development of ORC. This project proposes a vapor-liquid ejector assisted ORC system working with zeotropic mixture. Using its characteristics of ejection and pressure lift, a vapor-liquid ejector is applied to reduce the power consumption of working fluid pump and increase the power output of turbine. Meanwhile, a better temperature match to source/sink is realized by using the zeotropic mixture and composition adjusting. Following “phenomenon to process to system”, three research contents are addressed as: generation of the zeotropic condensation shock and its regulation mechanism, feature and principle of the vapor-liquid ejector, system thermodynamic analysis. By means of theoretical analysis, mathematical modeling, experimental study and system simulation, it is to obtain the maximum pressure lift of the zeotropic condensation shock, and reveal the coupling mechanism of entrainment ratio and pressure lift ratio to system performance, as well as achieve high efficiency system operation. The project is of great significance to improve the vapor-liquid ejector theory, and very important to the development of small-scale ORC.

有机朗肯循环（ORC）是非常有前景的热功转化技术，工质泵的耗功在小型ORC中严重影响循环效率，成为发展瓶颈。本项目提出一种气-液喷射式非共沸ORC系统，利用气-液喷射的引射和升压特性，减少工质泵的耗功和提高膨胀机的输出功，同时利用非共沸工质和组分调节，实现与冷/热源更好的温度匹配。按照“现象→过程→系统”的层次关系，围绕非共沸工质凝结激波产生与调控机理、气-液喷射过程的特性和规律、系统热力学分析这三个研究内容，通过理论分析、数学建模、实验研究和系统仿真模拟，获得非共沸工质凝结激波的升压极限，揭示喷射系数和升压比与系统热力性能的耦合机理，实现系统高效运行。本项目对气-液喷射理论的完善有重要科学意义，对小型ORC的发展有重要应用价值。

有机朗肯循环（ORC）发电系统是极具前景的热功转化技术，工质泵耗功严重影响小型ORC系统能效。项目提出利用气-液喷射的引射和升压特性，减少工质泵的耗功和提高膨胀机的输出功，同时利用非共沸工质，实现与冷/热源更好的温度匹配，实现能效提升。按照“现象-过程-系统”的层次关系，围绕非共沸工质凝结激波产生与调控机理、气-液喷射过程的特性和规律、系统热力学分析展开了深入研究。结果表明：（1）在给定工况下，凝结激波生成与与气体喷嘴出口马赫数相关，且随高沸点组份的增加而增加；气体和液体的入口工况对非共沸工质凝结激波强度的影响较大。（2）基于理想气体假设的气体喷嘴与基于实际气体性质的喷嘴性能有较大的差别；对于两相喷嘴，其不同描述方程会导致喷嘴性能的较大差异，甚至会导致的喷嘴等熵效率大于1；气-液喷射器的最大升压比可达44.15，为实际升压比的16.94倍，升压比损失最多的是在混合室中，给定条件下，只有11.34%的温度㶲转化为压力㶲；满足非共沸工质Toluene/Heptane (0.5/0.5)升压比大于1的条件为喷射系数和喉部截面比分别小于12.5和1.6。（3）构建了新型的气-液喷射式ORC系统，当工质泵等熵效率低于57%，蒸发温度高于95℃时，其系统效率优于普通ORC和回热式ORC。当R1336mzz(Z)/R1234ze(Z)的组份为0.5/0.5时，系统效率最大，为12.56%；当组份为0.7/0.3时，输出功最大为3.39 kW。基于热力学第二定律分析，系统最大㶲损为蒸发器，其次是膨胀机，气-液喷射器、冷凝器和工质泵。本项目对气-液喷射理论的完善有重要科学意义，对小型ORC的发展有重要应用价值。