60175 - Numerical Investigation on Hydrodynamic Characteristics of Supercritical Co2 Cylindrical Film Seal 

The gas film seal has been extensively utilized in the fields of energy, petroleum and chemical industry due to its prominent advantages of non-contact, little wear, long durability, high stability and low power consumption. In view of the superior performance, the gas film seal is suitable for high-speed turbomachinery theoretically.

To design seals with significant performance in supercritical carbon dioxide (SCO₂) environment, this paper establishes a spiral-grooved cylindrical film seal structure and aims to study the effects of structural and operating parameters. The sealing performance and aerodynamic characteristics are obtained by the computational fluid dynamics method.

It indicates that with the increase of eccentricity, the leakage, floating force, friction torque and Nu all ascend. When the film thickens, the leakage increases while the floating force and friction torque decrease, and there is a transition from heat dissipation to absorption. The aspect ratio should be chosen flexibly according to the actual demand due to its non-monotonous effect on the performance.

The speed and inlet pressure have significant influence on the sealing performance under different working conditions. The leakage, floating force, friction torque and Nu all rise up with the increase of inlet pressure. The leakage and Nu decrease while the floating force and friction torque increase with the escalation of rotating speed.

In addition, great results are obtained by coupling cylindrical film seal to a SCO₂ radial-inflow turbine with slight reductions of the power and efficiency, which suggests the potential applicability of cylindrical film seal to SCO₂ turbomachinery.