Multi-approach analysis of catalytic recombination in hypersonic flow극초음속 유동장에서의 촉매 재결합 현상에 대한 다중 접근 분석

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dc.contributor.advisorPark, Gisu-
dc.contributor.authorYang, Yosheph-
dc.description학위논문(박사) - 한국과학기술원 : 항공우주공학과, 2020.8,[xiii, 196 p. :]-
dc.description.abstractSurface catalytic recombination phenomena have received extensive attention since these phenomena are responsible for an additional heat transfer that space vehicle may encounter during the (re-)entry process. Better understanding and accurate prediction of these phenomena play an important role in the design process for thermal protection system. With this importance being considered, the present work aims to study the catalytic recombination process from various perspectives. The approaches considered in the present study include the following: catalytic boundary layer, experimental catalytic assessment, catalytic modeling, and molecular dynamics study. Concerning the boundary layer study, the Goulard's theory, a well-known method to estimate the catalytic properties from heat transfer measurement, has been improved. The developed catalytic boundary layer theory takes into account various number of species in a gas mixture, diffusion phenomena, and different recombination efficiency for oxygen and nitrogen atoms. Two different major solution methods, matrix diagonalization and shooting methods, have been proposed to obtain the solution for the developed catalytic boundary layer. Further investigation includes the application of the developed theory to estimate the heat transfer in tertiary and quinary gas mixtures. In the experimental approach, the catalytic assessment is conducted through heat transfer measurement at the shock tube end-wall using thin-film gauges. The driven gas mixture consists of 21\%O\textsubscript{2}-79\%Ar by volume. The experimental measurement emphasizes on the catalytic assessment for a SiC-coated surface. The effect of surface roughness and pre-heating treatment on the heat transfer is considered. The results reveal that a roughened surface, due to a higher number of surface site concentration, gives a higher heat transfer and thus bigger recombination efficiency value. On the other hand, the pre-heating treatment gives a lesser heat transfer, which results in lower recombination efficiency. The first numerical approach applied to understand the catalytic process is performed through finite-rate catalytic modeling. Two different finite-rate catalytic modelings are considered: Norman's model and an updated finite-rate catalytic model. The updated catalytic model includes a more number of surface reactions that are not considered in the Norman's model. The parameters required for the model are obtained through curve-fitting process with the experimentally measured data as the input parameters. The modeling result shows that the required parameters depend highly on the chosen experimental data values and different sets of surface reactions may alter the dominant reaction at low wall temperature during the recombination process. Yet another numerical approach to study the catalytic recombination process is achieved through the microscopical analysis using molecular dynamics (MD) study. By using a reactive force field (ReaxFF), the surface catalytic recombination process is modeled with a fixed influx boundary condition. Specifically, the importance of argon atom in the oxygen recombination process is studied through this microscopical study. By varying the argon gas pressure near the surface while keeping the oxygen gas pressure constant, the importance of argon gas in recombination process is investigated. It is observed that the argon gas does not exhibit a major influence on the oxygen recombination process on the silica surface.-
dc.subjectcatalytic recombination▼ahypersonic flow▼aboundary layer▼aheat transfer measurement▼acatalytic modeling▼amolecular dynamics-
dc.subject촉매 재결합▼a극초음속 유동▼a경계층▼a열 전달 측정▼a촉매 모델링▼a분자 동역학-
dc.titleMulti-approach analysis of catalytic recombination in hypersonic flow-
dc.title.alternative극초음속 유동장에서의 촉매 재결합 현상에 대한 다중 접근 분석-
dc.description.department한국과학기술원 :항공우주공학과,-
dc.contributor.alternativeauthorYOSHEPH YANG-
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