Session: 4.3 - Nuclear Power

Paper Number: 108959

108959 - Numerical Modeling of an Elastohydrodynamic Seal Design for Supercritical Co2 Power Cycles 

Supercritical carbon dioxide (sCO₂) power cycles show great potential for higher plant efficiencies and power densities for a wide range of power generation applications such as fossil fuel power plants, nuclear power production, solar power, and geothermal power generation. sCO₂ leakage has been one of the main concerns in such applications, 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 analytical 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. Also, a parametric study was conducted to see the effects of the seal thickness, shaft diameter, and seal length on the performance of the seal. The results showed that all three geometric parameters play a major role in the seal deformation and the mass flow rate of the seal. For the seal thickness, the mass flow rate increased as the seal thickness increased. It resulted to be 0.00161 kg/s and 0.004055kg/s for the seal thicknesses of 0.5 mm and 2.0 mm, respectively at 20 MPa.  An increase in the shaft diameter led to a decrease in the mass flow rate with being 0.00187 kg/s and 0.00125 kg/s for the shaft diameters of 25 mm and 50 mm, respectively at 20 MPa. For the seal length, the mass flow rate decreased with increasing the seal length with being 0.00255 kg/s and 0.001185 kg/s for the seal lengths of 13 mm and 28 mm, respectively at 20MPa. The presented analytical study lays a solid foundation for future model developments that could be used in the design of the proposed EHD seal.

Presenting Author: Sevki Cesmeci Georgia Southern University

Presenting Author Biography: Dr. Sevki Cesmeci currently works as an Assistant Professor of Mechanical Engineering at Georgia Southern University. Dr. Cesmeci's research interests are in the general area of thermo-fluidic systems, micropump designs for drug delivery, and smart materials and structures. Dr. Cesmeci currently serves as the Principal Investigator of an STTR Phase II project about advanced sealing systems for supercritical carbon dioxide turbomachinery funded by the U.S. Department of Energy.