A cooling system was designed for a supercritical carbon dioxide(S-CO_2) axial turbine. The dry gas seal

shaft and casing were cooled by extracting the low temperature S-CO_2 in the pipeline behind the compressor to ensure that the dry gas seal operating temperature was below 200 ℃.The flow and heat transfer characteristics of the cooling system were analyzed using the coupled heat transfer method

and the temperature distributions of solid domains such dry gas seal

shaft and casing of different cooling schemes were compared. The research shows that the temperature drop of the shaft reaches 220.3 ℃ when theshaft cooling scheme is adopted

and the maximum temperature of the dry gas seal is 229.1 ℃. Further introduction of S-CO_2 with lower temperature and larger flow rate to cool the casing can inhibit the heating effect of the high temperature mainstream at the turbine inlet. The temperature drop of the shaft increases to 244.1 ℃

and the maximum temperature of the dry gas seal decreases to 181.2 ℃. Meanwhile

the reasonable temperature gradient of the cooled domains such as the dry gas seal

shaft and casing is achieved. The cooling system designed in this paper provides a solution for the safe and reliable operation of S-CO_2 axial turbines.