Numerical Modeling of an Elastohydrodynamic Seal Design for Supercritical CO₂ Power Cycles

Supercritical carbon dioxide (SCO₂) leakage has been one of the major issues in sCO₂ power cycles, penalizing the cycle efficiencies. The effect of the seal leakage on the cycle efficiency could be as high as 0.65% for a utility sCO₂ power cycle. Therefore, there is a pressing need for effective sealing solutions to get the full benefit of sCO₂ power generation technology. To offer a potential solution, we propose an Elasto-Hydrodynamic (EHD) seal that can work at elevated pressures and temperatures with low leakage and minimal wear. The EHD seal has a very simple, sleeve like structure, wrapping on the rotor with minimal initial clearance at 25 to 50μm levels. In this work, a proof-of-concept study for the proposed EHD seal was presented by using the Reynolds equation, Lame’s formula, Barus Equation, and Dowson-Higginson formula to model the pressure distribution along the seal clearance as well as the seal deformation. The numerical modeling of the seal was carried out in Matlab using its built-in ordinary differential equation solver. The seal was evaluated for a 2″ diameter test seal with a pressure range of 0.2 MPa to 20 MPa. At the high pressure of 20 MPa, the clearance height at the throat (h_t) was found to be 24.7 μm which is about 50.6% than the initial seal clearance (h₀) of 50 μm, which resulted in a mass flow rate of 0.00162 kg/s. The presented analytical study lays a solid foundation for future model developments that could be used in the design of the proposed EHD seal.