三级冷凝朗肯循环的构型和工质同时优化

Simultaneous Optimization of the Configuration and Working Fluid for the Three-stage Condensation Rankine Cycle

为了提高液化天然气(LNG)冷能发电系统的性能,大部分学者关注通过改善换热过程来实现,而对压缩和膨胀过程关注较少.压缩和膨胀过程的布局会影响透平和泵的工况,进而影响循环性能.因此,本文基于我们之前提出的三级冷凝朗肯循环,对压缩过程和膨胀过程的布局进行优化。对9种构型不同的循环,为了提高优化效率,本文提出了一种超结构循环,内含这9种可能的循环构型,并引入了工质选择系数,完成了循环构型和工质的同时优化.结果发现,压缩布局对循环性能影响不大,而膨胀布局的影响更大,其中串联布局性能最佳,而且最佳循环构型不受LNG气化压力影响,仅与工质有关。

Most researches enhanced the heat exchange process to improve the performance of LNG cold power generation system,and the compression and expansion process are less considered.The arrangements for compression and expansion process can affect the working conditions of turbines and pumps,thus affecting the cycle performance.Therefore,this paper optimizes the arrangement for compression and expansion process on the basis of the three-stage condensation Rankine cycle proposed in our previous work.For the 9 cycles with different structures,this paper proposes a superstructure that contains these possible cycle structures to improve the efficiency of the optimization,and introduces the selection coefficient for the working fluids and accomplishes the Simultaneous optimization of the configuration and working fluid.The results indicate that the arrangements for compression process have little effect on the cycle performance,while those for expansion process have a relatively significant effect where the serial expansion arrangement has the best performance.Furthermore,the optimum cycle configuration is not affected by the gasified pressure of LNG and only depends on the working fluid used.