A PROOF-OF-CONCEPT STUDY OF A NOVEL ELASTO-HYDRODYNAMIC SEAL FOR CO₂

This paper deals with numerical studies of a novel Elasto-Hydrodynamic Seal (EHD), which has been developed for supercritical CO₂ (sCO₂) turbomachinery applications. Current sCO₂ turbomachinery suffer from high leakage rates, which is creating a major roadblock for the full realization of sCO₂ power technology. The high leakage rates not only penalize the efficiencies but also create environmental concerns due to greenhouse effects caused by increased CO₂ discharge to the atmosphere. The proposed novel EHD seal needs to work at elevated pressures (12 – 35 MPa) and temperatures (350 – 700 °C) with low leakage and minimal wear. The unique mechanism of such a EHD seal provides a self-regulated constriction effect to restrict the flow without substantial material contact, thereby minimizing the leakage and wear. This work utilizes a physics-based modeling approach. The flow through the gradually narrowing seal clearance is modeled by the well-known Reynolds equation in EHD lubrication theory. Whereas the deformation of the seal is modeled by using the governing equations of three-dimensional solid mechanics. As for the solution methodology, COMSOL’s Thin-Film Flow and Solid Mechanics Modules were employed with their powerful capabilities. The numerical results were presented and discussed. It was observed that the Reynolds equation fully coupled with the surface deformation was able to capture the constriction effect successfully. It was also interesting to observe that the seal leakage followed a quadratic trend with increasing pressure differential, which can become advantageous for high-pressure applications such as sCO₂ power generation technology.