Design and performance analysis of three stage centrifugal turbine

In this paper, the three-stage centrifugal turbine was designed based on the thermodynamic parameters of a four-stage test axial turbine. 1D aerodynamic design, 3D numerical simulation and optimization, and analysis on off-design performance of the centrifugal turbine were conducted. The results show that the key simulation parameters including total-static efficiency, shaft power, reaction degree, velocity ratio and pressure ratio of turbine stages are close to the 1D calculation values; at the design condition, streamline is smooth in the passage of turbine cascades; high efficiency has been obtained, indicating that the aerodynamic performance of three-stage centrifugal turbine meets the designed requirements. In off-design condition, the total-static efficiency of the designed turbine increases with the increase of pressure ratio first and then decreases; the shaft power decreases with the increase of pressure ratio; the mass flow rate increases gradually with the decrease of pressure ratio and finally tends to be constant when the turbine is under the blocking condition; the variation trend of total-static efficiency, shaft power, mass flow rate with the pressure ratio is similar at different speeds. The total-static efficiency, shaft power and mass flow rate of centrifugal turbine are almost equal to those of the axial turbine at design condition. The total-static efficiency of radial outflow turbine is close to that of axial flow turbine at different pressure ratio, but the mass flow rate of centrifugal turbine is smaller than that of axial flow turbine.