Term of Award

Spring 2024

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Digital Commons@Georgia Southern License

Department

Department of Mechanical Engineering

Committee Chair

Sevki Cesmeci

Committee Member 1

Priya Goeser

Committee Member 2

Prakashbai Bhoi

Abstract

Supercritical carbon dioxide (sCO2) power cycles outperform conventional thermodynamic cycles regarding the efficiency and equipment footprint because of its unique property of maintaining the density of liquid in the gaseous phase at supercritical state (304.13 K and 7.37 MPa). It has robust use in concentrated solar power, fossil fuel power plants, geothermal electricity, nuclear power, and ship propulsion. To fully utilize sCO2 power cycles, technology readiness must be demonstrated at 10-60 MWe scale, with a working temperature and pressure of 350-700°C, and 10-35 MPa respectively. A crucial obstacle to the full realization of this technology is the absence of effective sealing. As a solution, an Elasto-Hydrodynamic (EHD) seal is proposed for sCO2 cycles which leverages the proven elastohydrodynamic lubrication theory to minimize leakage and wear, creating a self-regulating constriction effect. This study used a physics-based modeling approach to study elastohydrodynamic sealing solutions, utilizing COMSOL's Thin-Film Flow module and solid mechanics module for seal deformation analysis. The results of this study were compared with the experimental results. A test seal with a 2" diameter and a pressure range of 0 Pa to 1.0 MPa was used to examine the seal. Both numerical simulation and experimental results showed the throttling effect successfully. The numerical analysis showed a maximum leakage rate of 7.51 g/s at 0.3 MPa, decreasing to 0.05 g/s at 0.85 MPa. The experimental study recorded a maximum leakage rate of 6.24 g/s at 0.5 MPa pressure, decreasing to 2.35 g/s at 1.0 MPa. Considering that the proposed numerical approach is one of the most simplified analyses of the EHD seals, these results are very encouraging. The proposed model could further be enhanced to capture the dynamic behavior of the seal more successfully. Thus, it lays a foundation for more sophisticated model developments. Yet, the proposed model could still be used as an initial design tool to estimate the design boundaries of the EHD seal as well as conducting a parametric analysis to determine the influence of significant design parameters on the performance of the EHD seals.

Research Data and Supplementary Material

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