The design and analysis of supercritical carbon dioxide centrifugal turbine

Abstract

Turbine is one of key components in the supercritical CO2 cycle, and centrifugal turbine has a big advantage in the SCO2 cycle because of the great compressibility of SCO2. In this paper, a 10MW single-stage centrifugal turbine using SCO2 as the working fluid was designed. The unsteady three-dimensional flow field inside the blade passages was assessed by software CFX. In order to obtain the desired parameters of the turbine with maximum total-static efficiency, blade shape was optimized by adjusting the blade thickness and blade angle distribution. The total-static efficiency and output power of the optimized SCO2 centrifugal turbine are 89.02% and 10.07MW, respectively, which generally meet the design requirements. The off-design aerodynamic performance of the designed centrifugal turbine stage was also analyzed. The results show that the relative mass flow rate increases with the increase of the pressure ratio; the total-static efficiency rapidly increases at first and then decreases slowly with pressure ratio increasing; the output power increases with the increasing pressure ratio at its designed speed. When the turbine operates at different rotational speeds, the minimum and operational flow rate for the designed centrifugal turbine is increased with the increase of the rotational speed, while the maximum and operational flow rate remains constant. The high efficiency always occurs at the condition of high flow rates.