Term of Award

Summer 2022

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Mechanical Engineering

Committee Chair

Sevki Cesmeci, PhD

Committee Member 1

Priya Goeser, PhD

Committee Member 2

Prakashbhai Bhoi, PhD

Abstract

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 0.2MPa to 20MPa. At the high pressure of 20MPa, the clearance height at the throat (ht) was found to be 24.7µm which is about 50.6% than the initial seal clearance (h0) of 50µm, 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 seal thickness 0.5mm and 2.0mm, respectively at 20MPa. An increase in the shaft diameter led to a decrease in mass flow rate with 0.00187 kg/s and 0.00125 kg/s for 25mm and 50mm respectively at 20MPa. For the seal length, the mass flow rate decreased with increasing seal length with 0.00255 kg/s and 0.001185 kg/s for seal lengths of 13mm and 28mm 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.

Research Data and Supplementary Material

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