基于遗传算法的LNG气化混合工质配比研究

Research on LNG gasification mixed working medium ratio based on genetic algorithm

混合工质合适的配比可以使其放热曲线与LNG气化曲线更好的匹配,减少冷能损失,从而提高循环效率。初选R23和R170为第一级循环的混合工质,R290、R143a、R1270和R125为第二级循环的混合工质。利用Hysys建立了利用LNG冷能发电的两级低温朗肯循环系统。以系统净输出功为目标函数,利用Design Expert设计混料试验进行计算并进行方差分析。借助Matlab中遗传算法得到混合工质配比的优化结果,其第一级循环配比:R23为80%、R170为20%;第二级循环配比:R290为33%、R134a为3.2%、R1270为60.1%、R125为3.7%。此时,系统净输出功为1 447.26 kW。再次利用Hysys对其进行验证,可靠度为99.91%。研究表明:第一级循环中制冷剂R23和第二级循环中R1270的含量对系统净输出功的影响最为显著。

The appropriate ratio of mixed working medium can make the heat release curve better match the LNG gasification curve, reduce the loss of cold energy, and improve the cycle efficiency.R23 and R170 were initially selected as the mixed working mediums of the first-stage circulation, and R290, R143 a, R1270 and R125 were the mixed working mediums of the second-stage circulation. A two-stage low-temperature Rankine cycle system using LNG cold energy to generate electricity was established by Hysys.Taking the net output power of the system as the objective function, and Design Expert was used to design a mixture experiment for calculation and variance analysis.With the help of genetic algorithm in Matlab, the optimization result of the mixed working medium ratio was obtained. The first-level cyclic ratio: R23 is 80%, R170 is 20%;the second-level cyclic ratio: R290 is 33%, R134 a is 3.2%, R1270 is 60.1% and R125 is 3.7%. At this time, the net output power of the system is 1447.26 kW.It is verified by Hysys again, and the reliability is 99.91%.Research shows that the content of refrigerant R23 in the first-stage cycle and R1270 in the second-stage cycle has the most significant impact on the net output of the system.