Thermodynamic analysis of a novel supercritical carbon dioxide Brayton cycle based on the thermal cycle splitting analytical method

摘要

The closed recuperative Brayton cycle using supercritical carbon dioxide (sCO(2) cycle) is becoming a hot research topic with the aim of achieving higher power generation efficiency. To evaluate the performance of the sCO(2) cycle with different configurations, the thermal cycle splitting analytical method was proposed to split the complex sCO(2) cycle into a simple host cycle and one/several simple equivalent power cycle(s) (EPC). Using this new analytical method, three basic modification measures for the sCO(2) cycle, i.e., recompression, intercooling and reheat, can be considered as deducting a low-efficiency EPC, adding a low-temperature EPC for heat recovery and adding a high-efficiency EPC from/to the host cycle, respectively. Based on the proposed analytical method, a novel combined sCO(2) cycle configuration was proposed, in which the recompression splitting point is not effected by the intercooling process and partial intercooling was adopted to avoid the additional heat input from the heater. The split EPCs were utilized to analyze the influences of the modification parameters on the performance of the novel combined cycle, and finally helped to achieve the cycle efficiency at 53.58%. The proposed novel combined cycle was also compared with the other combined cycles and the benefit of the novel combined cycle for efficiency improvement was directly and visually illustrated by the proposed analytical method in a shortcut way, and the results showed that the efficiency of the novel combined cycle was higher than those of other combined cycles.