Numerical investigation on flow characteristics and aerodynamic performance of shroud seal in a supercritical CO₂ axial-flow turbine

Increasing attention has been paid to the axial-flow turbine in supercritical CO₂ power cycle and the tip leakage has a significant effect on turbine performance. In the absence of investigation into supercritical CO₂ seal on shroud, four types of configurations are established based on a supercritical CO₂ axial-flow turbine: the structure without leakage (Without leakage) and the structures with a smooth leakage passage (Smooth), labyrinth seals (Labyrinth) and dry gas seal (DGS). The flow characteristics and aerodynamic performance are discussed in detail. The dry gas seal arranged on the shroud can substantially improve the overall performance. Compared with Labyrinth, the leakage of DGS is reduced by 99.38% while the power and isentropic efficiency are raised by 0.88% and 1.56% respectively. The mass flow rate and leakage increase while the power and isentropic efficiency decrease as seal clearance increases. The mechanical load and thermal load result in converse axial deformation of seal end face while the former performs more remarkably. DGS achieves notable performance close to Without leakage under different inlet pressure and temperature.