Assessment of gas-surface interaction modelling for lifting body re-entry flight design

Space re-entry is a challenging endeavor due to the harsh thermo-chemical environment around the vehicle. Heat flux being the reference parameter for Thermal Protection System (TPS) design, the total energy transfer can significantly increase due to the exothermic atomic recombination enhanced by TPS catalytic properties. The catalytic recombination coefficient modelling is critical for heat flux computation during TPS design. This work assesses the ability to determine the recombination coefficient at Von Karman Institute's (VKI) plasma wind tunnel (Plasmatron) as a step towards future validation of catalytic models : from a reference catalytic model development for enthalpy characterization of the facility, to the identification of the most influential parameters found in non-equilibrium boundary layers. Plasmatron test results encourage a flight extrapolation strategy development in order to link the catalysis measured on ground to the catalysis appearing in flight. The strategy, focused on off-stagnation point conditions, shall contribute to future post-flight activities of the CATalytic Experiment (CATE) on board of the Intermediate eXperimental Vehicle (IXV). Relevant data from IXV and CATE are also presented, laying the foundation for for future developments at VKI.Postprint (published version

Assessment of gas-surface interaction modelling for lifting body re-entry flight design

Space re-entry is a challenging endeavor due to the harsh thermo-chemical environment around the vehicle. Heat flux being the reference parameter for Thermal Protection System (TPS) design, the total energy transfer can significantly increase due to the exothermic atomic recombination enhanced by TPS catalytic properties. The catalytic recombination coefficient modelling is critical for heat flux computation during TPS design. This work assesses the ability to determine the recombination coefficient at Von Karman Institute's (VKI) plasma wind tunnel (Plasmatron) as a step towards future validation of catalytic models : from a reference catalytic model development for enthalpy characterization of the facility, to the identification of the most influential parameters found in non-equilibrium boundary layers. Plasmatron test results encourage a flight extrapolation strategy development in order to link the catalysis measured on ground to the catalysis appearing in flight. The strategy, focused on off-stagnation point conditions, shall contribute to future post-flight activities of the CATalytic Experiment (CATE) on board of the Intermediate eXperimental Vehicle (IXV). Relevant data from IXV and CATE are also presented, laying the foundation for for future developments at VKI

Assessment of gas-surface interaction modelling for lifting body re-entry flight design

Space re-entry is a challenging endeavor due to the harsh thermo-chemical environment around the vehicle. Heat flux being the reference parameter for Thermal Protection System (TPS) design, the total energy transfer can significantly increase due to the exothermic atomic recombination enhanced by TPS catalytic properties. The catalytic recombination coefficient modelling is critical for heat flux computation during TPS design. This work assesses the ability to determine the recombination coefficient at Von Karman Institute's (VKI) plasma wind tunnel (Plasmatron) as a step towards future validation of catalytic models : from a reference catalytic model development for enthalpy characterization of the facility, to the identification of the most influential parameters found in non-equilibrium boundary layers. Plasmatron test results encourage a flight extrapolation strategy development in order to link the catalysis measured on ground to the catalysis appearing in flight. The strategy, focused on off-stagnation point conditions, shall contribute to future post-flight activities of the CATalytic Experiment (CATE) on board of the Intermediate eXperimental Vehicle (IXV). Relevant data from IXV and CATE are also presented, laying the foundation for for future developments at VKI.Postprint (published version

Design of a Solid Freeform Fabrication Diamond Reactor

Solid Freeform Fabrication (SFF) has progressed from the visualization aided stage of computer aided designs (CAD) to rapid prototyping of structural parts. Among the promising techniques for producing structural prototypes is the technology ofchemical vapor deposition (CVD) ofpolycrystalline diamond. This paper discusses the thermodynamic and kinetic theories that suggest that structural diamond may be rapidly deposited at rates approaching 1 mmJhr from the vapor phase at metastable thermodynamic conditions. The design of a reactor that will produce structural diamond prototypes is discussed. This reactor combines downstream microwave plasma enhanced chemical vapor deposition (DMWPECVD) with a scanned CO2 laser that locally heats the substrate to diamond deposition temperatures. The input:Fases are H2, 02' CH4, and Ar. The operating pressure range of the reactor is 1 x 10- to 7 x 102 Torr. The reactor is designed for in situ determination of deposit thickness while deposition occurs as well as having the capacity of fitting on an existing resonance enhanced multiphoton ionization time of flight mass spectroscopy (REMPITOFMS) apparatus that will allow for plasma diagnostics immediately above the heated substrate. Plasma diagnostics will be employed to determine the active metastable species that results in diamond deposition so that optimization can be made ofthe operating parameters to maximize diamond selectivity and deposition rate.Mechanical Engineerin

Computational studies of plasma–liquid interactions

By the introduction of modern power supplies capable of producing low-temperature plasma under atmospheric pressure, the interaction between plasmas and liquids have presented great potentials in many exciting applications in recent years. Cancer treatment, wound healing, nanomaterial production, water disinfection and chemical analysis are just a few examples of emerging applications of plasmas interacting with liquids. Despite the large attention received in recent years, research in this area is still in its infancy. To take the current technologies further and develop practical solutions for these applications, many fundamental questions need to be answered first. Although reactive oxygen species (ROS) and reactive nitrogen species (RNS) are known to play a dominant role in these applications. The underlying physics of plasma-liquid interaction, the chemistry involved in the liquid phase, the interfacial effects governing the mass transfer between the plasma and the liquid, mass transfer quantities and the propagation mechanisms of the transferred species throughout the liquid media are just a few sample questions that remain unanswered.A combination of computational modelling and experimental methods are used throughout this thesis to shine some light on some of these questions. New insights into the dynamics of the liquid phase chemistry as well as the physical effects of the plasma on the liquid bulk are addressed as part of this thesis. The developed computational model not only provides a better understanding of the system in general, but also predicts properties and quantities which are difficult or impossible to measure experimentally with current available apparatus and measurement techniques. The results are then employed to layout guidelines for optimized configurations of plasma-liquid systems in practical applications.Since the gas phase computational study has been explored extensively in previous works, in this thesis our main focus will be the interaction between the plasma and the plasma effluent with the liquid phase and the subsequent physicochemical reactions. The problem is broken down into three parts. In the first part, the plasma gas phase is studied independent of the liquid phase to clarify the kinetics of the plasma medium. The main chemical reaction pathways are studied as well as the effect of input power modulation on the chemical pathway variations and final gas composition. The next part focuses on the transfer of heavy reactive species into the liquid and the subsequent chemical reactions. This is relevant in remote plasma systems in which the plasma is not in electric contact with the liquid. In particular we study an epoxidation reactor that relies on a He + O2 to epoxidate alkenes in liquid phase. In the third part, the focus is on the transfer of electrons into the liquid phase. In this case, the plasma is electrically connected to the liquid and electrons are delivered to the liquid to drive liquid phase reactions. The electrochemical properties of the liquid are studied along with the effect of the surface tension gradient caused by the plasma on the liquid phase mixing patterns.</div

Computational Modeling of Gas-Surface Interactions for High-Enthalpy Reacting Flows

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106443/1/AIAA2013-187.pd

Chemical Kinetics

Chemical Kinetics relates to the rates of chemical reactions and factors such as concentration and temperature, which affects the rates of chemical reactions. Such studies are important in providing essential evidence as to the mechanisms of chemical processes. The book is designed to help the reader, particularly students and researchers of physical science, understand the chemical kinetics mechanics and chemical reactions. The selection of topics addressed and the examples, tables and graphs used to illustrate them are governed, to a large extent, by the fact that this book is aimed primarily at physical science (mainly chemistry) technologists. Undoubtedly, this book contains "must read" materials for students, engineers, and researchers working in the chemistry and chemical kinetics area. This book provides valuable insight into the mechanisms and chemical reactions. It is written in concise, self-explanatory and informative manner by a world class scientists in the field