DOI
https://doi.org/10.25772/FGAX-8K58
Author ORCID Identifier
https://orcid.org/0009-0004-5942-0023
Defense Date
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Mechanical and Nuclear Engineering
First Advisor
Dr. Gennady Miloshevsky
Second Advisor
Dr. Zeyun Wu
Third Advisor
Dr. Karla Mossi
Fourth Advisor
Dr. Ahmed Hassanein
Fifth Advisor
Dr. Tatyana Sizyuk
Abstract
Beryllium (Be) is a material which is used as a plasma facing component in tokamak reactors due to its unique properties of high thermal conductivity, low density, and high strength. However, under extreme conditions of high temperature and pressure, Be can melt on the surface of armor tiles and molten droplets can be ejected into the reactor chamber leading to disruption of fusion plasma. The variations of pressure, mass density, velocity, and temperature of Be vapor on the surface of melt layer as well as magnetic field strength and direction can influence the splashing of Be melt and their effects have to be studied.
The Computational Fluid Dynamics (CFD) model based on the OpenFOAM toolbox was used to treat the coupled flow of liquid Be metal and its vapor. The vapor-melt interface is modeled using the volume of fluid (VOF) approach implemented in the interCondensatingEvaporatingFoam (iCEF) solver that solves the continuity, momentum, heat conduction, and VOF equations. This CFD model is capable of predicting the hydrodynamic pressure effects of Be vapor on the melt layer motion, splashing, non-linear growth of melt waves, and ejection of molten droplets. The modeling accounts for the effects of thermal, viscous, gravitational, and surface tension forces at the vapor-melt interface. Influence of heat and mass transfer across the Be vapor-melt interface (phase change) on the melt layer stability is investigated. Magnetic field plays a crucial role in the tokamak reactor and hence, the investigation of different magnitude and pitch angles of the magnetic flux density for their effects on the flow of molten Be metal is performed. Deformation of ferrofluid droplet due to an applied magnetic field was used as a benchmark in the validation of iCEF solver. In addition, the wetting between the liquid Be and the solid surface takes place affecting the splashing of the molten layer. The effects of the above-mentioned factors on the development of melt structures and waves at the vapor-melt interface are studied.
The main findings of research are 1) the influence of phase change on Be melt splashing has caused higher portion of the molten Be to be ejected into a plasma and significantly decreased its removal time from 1-3 ms to less than 0.5 ms; 2) with increase in magnitude of magnetic flux density in the range from 1 T to 5 T, molten layer is removed at a faster rate and multiple elongated ligaments are formed during the splashing; and 3) as the pitch angle becomes perpendicular to the surface, the restriction on splashing motion of Be melt is observed. However, the results suggest that magnetic flux density and vapor velocity have significantly higher impact on the removal of Be melt than the magnetic field’s pitch angle. The measured Be melting data from Joint European Torus (JET), as the frontier research program in Europe, poses a good avenue for comparisons to ensure that the results of these modeling studies can be justified. Therefore, JET data reproduced by SMITER and MEMOS-U software packages are used for validations and juxtaposition of the JET and iCEF results is carried out.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
5-15-2024