Optimal Design and Steady-state Characteristic Analysis of High Speed S-CO2 Axial Turbine Blades

The operating characteristics of S-CO
₂
axial turbine with high rotating speed have a direct effect on system's energy conversion and cycle efficiency. At present, the research on S-CO
₂
axial turbine of high rotating speed is mainly focused on the aerodynamic characteristics of the whole turbine, and there is little literature focused on the distribution and variation regularity of the flow field in the structure under the steady operation condition. In order to solve the problem of internal flow situation of S-CO
₂
axial turbine, the method of modeling, simulation and numerical calculation through CFturbo and ANSYS/CFX software is adopted in this paper. Also the stator and rotor blade structures of axial turbine with different speed grades and fluid mass flow are optimized. On this basis, the NIST/REFPROP database S-CO
₂
physical parameters are introduced into the CFX material library and the 10-6 residual axis power and isentropic efficiency are calculated based on the SST k- ω turbulence model. Meanwhile the variation of flow velocity, stress and state of different axial turbine structures under steady and variable conditions are systematically analyzed. The results show that the variations of axial turbine speed, inlet temperature, mass flow rate and pressure have different effects on the flow field and pressure distribution in the turbine. The relationship between them can be analyzed by subsequent numerical simulation and further detailed analysis can be carried out. This research work can provide theoretical guidance for the design of S-CO
₂
axial turbine with different power levels and isentropic efficiency.