船舶烟气S-CO2布雷顿循环稳态热力学优化

Thermodynamic Optimization of Supercritical Carbon Dioxide Brayton Cycle in Exhaust Gas Recovery

主机烟气余热进行循环再利用是船舶绿色化的重要技术实现途径,其核心环节在于采用适宜的热力学循环系统实现烟气输入热功到涡轮输出轴功之间的高效能量转换。在简述超临界二氧化碳(S-CO2)布雷顿热力学循环系统基本原理和技术特点的基础上,根据换热器、涡轮机和压缩机等系统核心组成设备的数学模型,在Fortran软件环境中建立以系统热效率为目标优化函数的再压缩式循环结构的稳态运行效率数值计算仿真模型,分别针对循环压比、回热器总换热系数、分流系数等参数对系统循环热效率的影响问题进行算例分析。结果表明:在 2.10~2.45的压比范围内,不同工况条件下均存在全局最优分流系数使得热效率最大化。船舶热能动力循环发电系统最优运行工况分析中,在涡轮机入口温度500℃、压缩机入口温度35℃下,存在最优分流系数为0.39,对应的循环压比为2.37,循环热效率为32.15%。

Recycling and reusing the waste heat of the main engine flue gas needs the appropriate thermodynamic cycle system to realize the efficient energy conversion between the input heat of the flue gas and the output shaft power of the turbine. The basic principles and technical characteristics of the supercritical carbon dioxide Brayton thermodynamic cycle system are briefly described and the mathematical models of the core components, such as the heat exchangers, the turbines and the compressors, are built. The steady state simulation model of the recompression cycle structure is set up in Fortran software environment. The objective function for optimizing the thermal efficiency of the system is established. The influences of the cycle pressure ratio, total heat transfer coefficient of regenerator and the split coefficient on the thermal efficiency of the system are investigated through simulation. The results show that within the pressure ratio range of 2.10- 2.45, for each interested operating condition, the global split coefficient exists, leading to the optimal thermal efficiency. For instance, analyzing optimal operation conditions of marine thermal cycle power generation system, under 500℃ at the turbine inlet and 35℃ at the compressor inlet, the optimal split coefficient is 0.39, corresponding to a cyclic pressure ratio of 2.37 and a cyclic thermal efficiency of 32.15%.