串联式干气密封对超临界二氧化碳轴流透平气动性能的影响

Leakage problem is inevitable in the tip of axial-inflow turbine, which seriously affects the efficiency and operating safety. In actual engineering, seal structure is usually arranged on the shroud to weaken the influence of leakage flow. In order to further improve the seal performance, a series dry gas seal was arranged on the rotor shroud of a 1.5-stage supercritical carbon dioxide axial-inflow turbine. The flow characteristics and aerodynamic performance under different seal clearance were discussed in detail. The feasibility of the series dry gas seal was verified by adopting the thermal-fluid- solid coupling approach to study the deformation characteristics of seal face. The results showed that the arrangement of series dry gas seal on the shroud can effectively reduce the leakage and improve the leakage characteristics. When the seal clearance was 10μm, the dimensionless relative leakage was only 2.43×10^-5, and the efficiency was only 0.01% lower than that of turbine without leakage. As the seal clearance enlarges, the leakage and loss increased while the efficiency decreased. However, compared with the conventional single-stage dry gas seal, the series dry gas seal structure performed better under large seal clearance. Under all seal clearances, the thermo-mechanical axial deformation difference between the inner and outer radius of the seal face was less than 27μm, and high turbine efficiency can be kept after deformation. The results showed that arranging series dry gas seal on the shroud can effectively reduce leakage and maintain high aerodynamic performance with acceptable operating safety.