超临界二氧化碳再压缩布雷顿循环性能分析及优化设计方法研究

To develop engineering-applicable optimization design method for supercritical carbon dioxide Brayton cycle, analysis of the effects of key parameters on the recompression cycle was firstly carried out, and the necessity for cycle optimization design was elaborated. Then an optimization design method for the recompression cycle was proposed based on the particle swarm optimization algorithm. The minimum cycle pressure, cycle pressure ratio and flow split ratio were selected as optimization variables, with the cycle thermal efficiency considered as objective and inlet temperature difference of the flow-split tee as constraint. Results of parametric analysis show that the cycle thermal efficiency decreases persistently with the minimum temperature increasing, while increases monotonically with the maximum temperature increasing. An optimal minimum pressure and optimal pressure ratio resulting in the highest cycle efficiency are found, and they are effected by the minimum temperature and maximum temperature, respectively. Assigning less massflow to the re-compressor is expected to be beneficial to the cycle efficiency, and there is an optimal flow split ratio which would lead to the highest cycle efficiency. The inlet temperature difference of the flow-split tee is significantly effected by the flow split ratio, and this key parameter should be considered as a constraint for cycle optimization. Besides, the proposed method is capable for cycle optimization design, under different temperature difference constraints. Optimization design results showed that a thermal efficiency of 47.77% could be reached under 1℃ temperature difference, while a thermal efficiency of 47.83% could be reached under 10℃ and 20℃ temperature difference.