Leakage reduction mechanism of supercritical CO2 scallop damper seal: Vortex structure and turbulence dissipation

The scallop damper seal (SDS) is a new sealing solution utilized in supercritical CO2(S-CO2) turbomachinery, and its sealing performance is of great interest. Analyzing the energy dissipation of fluid in the seal is critical for understanding the leakage characteristics of SDS. In this paper, we develop a high-order compressible flow solver with real gas thermophysical modeling. The vortex structure and turbulence dissipation of leakage flow are investigated to uncover the leakage reduction mechanism of SDS. By comparing the flow fields within a labyrinth seal (LABY) and a full-partition pocket damper seal (FPDS), we demonstrate that SDS has better leakage reduction performance for S-CO2. The results indicate that S-CO2 fluid flows into the SDS cavity and expands significantly. The formed vortex dissipates sufficiently more energy, reducing the leakage flow rate (LFR). The increase in the Mach number of the fluid flowing through the SDS gap is limited. Still, the gas permeability phenomenon caused by the throttling effect is observed in the clearance of LABY and FPDS, resulting in an increased LFR. At the differential pressure of 5 MPa, the LFR of SDS is 36.6% and 54.4% lower than that of LABY and FPDS, respectively. Although the rotor rotation leads to an asymmetric distribution of vortex in the SDS cavity, the vortex develops rapidly and occupies the entire space. For the seal design of S-CO2 turbomachinery, enhancing the turbulence dissipation of fluid in the cavity and reducing the gas permeability of fluid in clearance should be the focus of attention.