A comparative analysis between simulation and test with roughness is carried out for a supercritical carbon dioxide(S-CO_2) axial turbine with different operating conditions

focusing on the roughness impact of the turbine performance. The results show that the numerical calculation method of wall roughness is able to assess the performance of the turbine at different load conditions accurately. Compared with test result

the maximum efficiency error is 1.82 percentage point. Wall roughness degrades the overall performance of the turbine

with a maximum efficiency drop of 2.8 percentage point at Ra1.6 roughness level during the five working condition

and the turbine stage roughness has a more obvious effect on the turbine performance. In addition

the more severe of wall roughness

the greater reduction of turbine efficiency. In non-design operating conditions

the efficiency drops by 11.6 percentage point at Ra6.3 roughness level. The wall roughness exacerbates flow separation of pressure surface

causing greater friction losses and serious affecting of turbine performance. The research can provide technical support for the design and performance simulation of S-CO_2 axial turbines.