Abstract: [Objecctive] In order to fully recover the waste[基金项目：国家自然科学基金青年基金项目(51906038)。 National Natural Science Foundation of China Youth Fund Project(51906038).] heat energy of gas turbine, this paper constructs the gas turbine-supercritical CO2 Brayton combined cycle waste heat recovery system, and through the cascade regenerativecycle to improve the overall cycle efficiency of the system so as to achieve the purpose of system optimization. [Methods] The mathematical model of each component is established by Matlab software, and the influence of cycle parameters on system performance is analyzed based on the method of optimal shunt ratio. [Result] The results show that the optimal shunt ratio improves the efficiency of the system by increasing the internal heat exchange and reducing the external heat source input. With the increase of the cycle pressure ratio, the internal heat recovery decreases gradually, which leads to the increase of the thermal efficiency of the circulation system at first and then decrease. When the heat transfer of the high temperature heat exchanger is slightly lower than that of the low temperature heat exchanger, the corresponding cycle pressure ratio is the best pressure ratio at the current inlet temperature. [Conclusion] When the two supercritical CO2 Brayton cycles match well, the thermal efficiency of the gas-recompression-regenerative combined cycle reaches 47.50%, which is 4.4 percentage points higher than that of the gas-recompression cycle under the same working conditions.

Key words: gas turbine, waste heat recovery, supercritical carbon dioxide, Brayton cycle, combined circulation, cycle efficiency, thermodynamic analysis