Master of Science, The Ohio State University, 2022, Entomology

Honey bees are exposed to an array of potentially toxic chemicals, which differ in aspects of their toxicity as well as their fate in the environment. In Chapter 1 of my thesis, I discuss the exposure and effects of toxic chemicals to honey bees through the lens of chemical kinetics. I also describe applications of kinetic modeling for the development of mechanistic models of colony exposure. In chapter 2, I demonstrate how kinetic modeling (toxicokinetic-toxicodynamic modeling) can be used to predict the long-term effects of chemical exposure on the survival of individual honey bees and the growth of their colonies. I focus on metal pollutants (As, Cd, Li, Pb, and Zn), which honey bees are exposed to in a range of human modified environments. I found that a toxicokinetic-toxicodynamic model (the General Unified Thresholds Model of Survival, GUTS) better predicted the survival of honey bees in the lab than a simple extrapolation of a standard (probit) model that is commonly used in honey bee risk assessments. When predicting the effects of metal exposure on colony growth, differences between modeling approaches were highly case-specific. In chapter 3, I focus on the exposure and effects of metals to immature honey bees. Specifically, I describe an experiment using queen-rearing boxes to measure the accumulation of metals into larval food (nurse jelly) and developing queen larvae. I also describe a laboratory study on the toxicity of different metals to honey bee larvae reared in vitro. I found that Cd and Li translocate into larval foods at a higher rate than has been observed for pesticides. Furthermore, when applied to the larval diet in vitro, As, Li, and Zn affected the survival of honey bee larvae at field-relevant concentrations.

Committee: Reed Johnson (Advisor); Mary Gardiner (Committee Member); James Strange (Committee Member) Subjects: Entomology; Environmental Science; Toxicology

Doctor of Philosophy, Case Western Reserve University, 2011, Biomedical Engineering

Ca2+ cycling between the cellular and subcellular compartments plays an important role in regulating cardiac contraction. Disturbance in Ca2+ handling occurs in heart failure and is closely related to abnormal contractile performance. The influx of extracellular Ca2+ through L-type calcium channel is the trigger and a key player in the Ca2+ cycling process. However, there are limited ways to measure it in vivo. Recently, manganese (Mn2+)-enhanced MRI (MEMRI) has been proposed as a promising probe to assess Ca2+ uptake because Mn2+ also enters the cell through the Ca2+ channels. However, quantitative analysis and substantial validation are still lacking, which has limited the application of MEMRI as an in vivo method for quantitative delineation of the Ca2+ influx rate. In the current thesis project, a quantitative MEMRI method was developed and validated using small animal models. The sensitivity to subtle alterations in Ca2+ influx rate was demonstrated in a qualitative MEMRI study using a genetically manipulated mouse model that manifested slightly altered L-type Ca2+ channel activity. To provide quantitative estimation of Mn2+ dynamics, fast T1 mapping techniques were developed based on the direct linear relationship between Mn2+ concentration and proton R1. An ECG-triggered saturation recovery Look-Locker (SRLL) method and a model-based compressed sensing method was developed and validated, respectively. When these two methods were combined, rapid T1 mapping (< 80s) of both myocardium and blood were achieved at high spatial resolution (234x469 μm2). Subsequently, a kinetic model was developed to determine Ca2+ influx rate from the quantitative MEMRI measurements. The robustness and accuracy of estimated Ca2+ influx rate was validated using perfusion MEMRI datasets with L-type Ca2+ channel activity well controlled by buffer ingredients. In conclusion, the accomplishment of this project provides a robust MEMRI method for in vivo quantification of L-type Ca2+ (open full item for complete abstract)

Committee: Xin Yu (Committee Chair); Chris Flask (Committee Member); Mark Griswold (Committee Member); David Rosenbaum (Committee Member); David Wilson (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Medical Imaging; Radiation; Radiology

Doctor of Philosophy, Case Western Reserve University, 2009, Biomedical Engineering

In the recent years molecular imaging has become an important tool in biomedical research. To quantify physiology from image data, compartment modeling has been shown to be useful by analyzing the pharmacokinetics from molecular images. However, some challenges still exist and limit the application of compartment modeling in a routine basis. Methods to resolve some of the existing challenges are proposed and validated in this thesis. First, non-invasive methods are developed to measure the input functions required in compartment modeling and parameter estimation for positron-emission tomography (PET) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) studies. Methods for image-derived input functions are developed and validated against the reference input functions. Second, a software environment is established to integrate functions that handle image analysis and modeling analysis based on COmpartment Model Kinetic Analysis Tool (COMKAT). Methods to enhance speed and interface for COMKAT have been implemented as described in this thesis. With the methods and software developed in this thesis, researchers can quantify in vivo pharmacokinetics with molecular imaging methods to measure the physiology and metabolism non-invasively in a routine basis.

Committee: Raymond Muzic PhD (Advisor); Xin Yu PhD (Committee Chair); Gerald Saidel PhD (Committee Member); Peter Faulhaber MD (Committee Member) Subjects: Biomedical Research; Engineering

Doctor of Philosophy, The Ohio State University, 2023, Electrical and Computer Engineering

We present a discussion on the reduced-order modeling of electromagnetic simulation in general, and kinetic plasma simulations in particular, using the Proper Orthogonal Decomposition technique. Computational electromagnetics has been an important tool for physicists and engineers since the mid-1960s, when the increasing availability of modern high-speed computers started to allow the numerical solution of practical problems for which closed-form analytic solutions did not exist or were impractical to calculate. The study of kinetic plasmas is of great interest both for theoretical exploration and technological applications such as design of vacuum electronic devices, the study of the interaction of space-borne assets and cosmic radiation, fusion experiments, among others. Due to the theoretical complexity of these problems and the difficulty in performing physical experiments, simulations are instrumental for obtaining new insights or developing new device designs by resolving the field and plasma behaviors when changes are made. Several variants of simulations exist, but particle-in-cell algorithms for solving particle dynamics coupled with finite-differences or finite-elements field solvers are particularly successful. Despite their success, such algorithms are still constrained by computational cost such as processing time and memory/storage limitations. The Proper Orthogonal Decomposition is a technique that extracts the spatiotemporal behavior from a function of interest or a set of data points. This spatiotemporal behavior is characterized by a set of coupled spatial and temporal modes, which makes the Proper Orthogonal Decomposition especially suitable for analyses and applications in dynamic systems; it has been used for creation of reduced-order models in the past, especially in the fluid dynamics community where it originated from but also in many other areas. We have explored the application of the Proper Orthogonal Decomposition technique to co (open full item for complete abstract)

Committee: Fernando Teixeira (Advisor); Casey Wade (Committee Member); Kubilay Sertel (Committee Member); Robert Burkholder (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Doctor of Philosophy (PhD), Ohio University, 2022, Chemical Engineering (Engineering and Technology)

Corrosion of pipelines is one of the major problems in the oil and gas industry. The research discussed herein focuses on the mechanistic study of the electrochemical reactions associated with corrosion using electrochemical impedance spectroscopy (EIS) as an advanced technique along with direct current (DC) techniques such as steady state potentiodynamic sweeps. The outcome of this research is to increase the understanding of reaction mechanisms occurring at the steel surface which can improve the existing models for the prediction of the corrosion rate. In acidic environments, which are studied in this work, the electrochemical reactions are the anodic dissolution of iron proceeding in parallel with the cathodic reduction of hydrogen ions and water. When using EIS to study an electrochemical reaction, it is important to know if at any given potential an impedance spectrum is collected that contains more information about one reaction or the other, or if it is a mixed response. Therefore, in the first part of this work, a model was developed to calculate the percent contribution of each electrochemical reaction to the measured impedance at different potentials. The model was developed based on calculated polarization resistances of electrochemical reactions using steady state potentiodynamic sweep data. It was concluded that, at any chosen DC potential, the reaction having the lowest impedance has the highest contribution to the total measured impedance response of an electrochemical system. Consequently, the developed model can be used to determine the DC potential at which a specific reaction of interest has the highest contribution to the measured impedance data. The same approach was used as a part of this study related to determining the diffusion coefficient of hydrogen ions. The DC potential for EIS measurements was chosen to obtain the most information about the cathodic reduction of hydrogen ions. In the following part of the work described in this (open full item for complete abstract)

Committee: Srdjan Nesic Dr. (Advisor) Subjects: Chemical Engineering

Master of Science (MS), Wright State University, 2020, Physics

A one-dimensional kinetic particle-in-cell (PIC) MATLAB simulation was created to demonstrate the time-evolution of various plasma distributions. Building on previous plasma PIC programs written in FORTRAN and Python, this work recreates the computational and diagnostic tools of these packages in a more user- and educational-friendly development environment. Plasma quantities such as plasma frequency and species charge-mass ratios are arbitrarily defined. A one-dimensional spatial environment is defined by total length and number and size of spatial grid points. In the first time-step, charged particles are given initial positions and velocities on a spatial grid. After initialization, the program solves for the electrostatic Poisson equation at each time step to compute the force acting on each particle. Using the calculated force on each particle and the “leap-frog” method, the particle positions and velocities are updated and the motion is tracked in phase-space. Modifying parameters such as spatial perturbation, number of particles, and charge-mass ratio of each species, the time-evolution for various distributions are examined. The simulated distributions examined are categorized as the following: Cold Electron Stream, Electron Plasma Waves, Two-Stream Electron Instability, Landau Damping, and Beam-Plasma. The time evolution of the plasma distributions was studied by several methods. Tracking the electric field, charge density and particle velocities through each time step yields insight into the oscillations and wave propagation associated with each distribution. One key diagnostic missing from the original FORTRAN code was the electric field dispersion relation. The numerical dispersion relation allows for further insight into modelling plasma oscillations/waves in addition to the kinetic/field energies and electric field tracking present in the original code. Simulated results show agreement with other kinetic simulations as well as plasma theory.

Committee: Amit Sharma Ph.D. (Advisor); Ivan Medvedev Ph.D. (Committee Member); Sarah Tebbens Ph.D. (Committee Member) Subjects: Atmospheric Sciences; Atoms and Subatomic Particles; Physics; Plasma Physics

Doctor of Philosophy, Case Western Reserve University, 2017, Chemical Engineering

Everyone has probably had the experience of feeling shocked when touching a doorknob after walking across a carpet. This is one of the many examples of electrostatic charging on surfaces. Electrostatic charging, or contact electrification, is a well-known phenomenon in various instances. However, the charging mechanism remains poorly understood. This thesis will elucidate the scientific basis of contact charging on quartz (0001) and sapphire (0001) surfaces with first principle electronic calculations, supported by experimental results. Both experiments and simulations show consistent charging direction and magnitude results, demonstrating the possibility to address electrostatic charging on surfaces of more complicated structures. Electrostatic discharge can happen as a result of charge buildup on surfaces, leading to the gas breakdown. Inadvertent gas breakdown can be harmful, such as damage to microelectronic components. Intentional gas breakdown can be utilized to generate plasma. With high reactivity at relative low temperature, plasma is able to dissociate thermodynamically stable molecules near room temperature, such as carbon dioxide and methane. In this work, we modulate power, volume, flow rate, pressure, voltage, discharge gap distance, and the simultaneous use of catalysts on conversion processes to control plasma reactions. Our combined experimental and multiscale simulation techniques provide a guidance to optimize plasma conversion processes.

Committee: Daniel Lacks (Advisor); R. Mohan Sankaran (Committee Member); Heidi Martin (Committee Member); Hatsuo Ishida (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2016, Biophysics

Dynamic Positron Emission Tomography (PET) has been increasingly demonstrated as a powerful tool to kinetically evaluate tumor physiology for cancer diagnosis and treatment response assessment. By offering differential kinetic information of radiotracers to interpret the dynamic processes of tracer uptake and retention in the target tumors, dynamic PET can characterize the tumors more accurately than the static PET imaging. However, the long scanning time, the strict data acquisition procedure as well as the complicated kinetic data analysis process required for a dynamic PET scan have brought challenges to its application in clinical routine. Solutions need to be explored to improve the feasibility of dynamic PET imaging in clinical oncology. In this dissertation, a detailed investigation of shortening dynamic PET acquisition duration has been completed. By comparing the kinetics results of the acquisition with full-time and that with several shortened acquisition durations, a feasible shortened acquisition duration for dynamic PET imaging was revealed. It was found that a 16min acquisition was long enough to provide accurate PET tracer kinetics. A simpler and faster kinetic modeling method named Patlak plot analysis was also compared to the widely used traditional 2-tissue compartment model (2TCM). It was discovered that Patlak plot analysis method could substitute for 2TCM to accurately quantify the tracer net influx rate Ki with shortened acquisitions. When involving time-of-flight (TOF) information into dynamic PET reconstruction, the feasibility of 16min-long acquisition duration was further confirmed with accurate Ki calculation and a high correlation to whole body maximum standardized uptake values (SUVmax). However, the addition of TOF resulted in variation in Ki quantification compared to the acquisition without it. Suggestions were therefore made that careful consideration should be given when assessing differently acquired and reconstructed dynamic PE (open full item for complete abstract)

Committee: Michael Knopp (Advisor) Subjects: Biophysics

Master of Science, The Ohio State University, 2016, Food Science and Technology

The purpose of this study was to evaluate the antifungal efficacy of the natamycin- shellac coating on commercially washed eggs and pasteurized eggs. Eggs were prepared into three groups: eggs that received no coating (control), eggs that were coated with shellac only (treatment 1), and eggs that were coated with shellac containing 400 µg/ml of natamycin (treatment 2). Concentration of natamycin suitable for application on shell eggs was determined previously. Egg groups were inoculated with mold spores and stored at 25°C for 18 days, and mold growth were monitored by enumeration on potato dextrose agar (PDA). Molds tested in this study belong to three genera: Mucor, Cladosporium and Penicillium. The experiment was repeated three times and results were analyzed statistically. Treatments that permitted mold growth provided data that allowed the construction of growth curves. These growth curves were fitted with logistic model, and growth kinetic parameters (maximum population (A), maximum specific growth rate (µmax), and lag time were estimated and compared. According to parameters comparison between control and treatment 1, shellac coating did inhibit fungal growth on washed egg, but it exhibited antifungal effectiveness against Mucor and Penicillium on pasteurized eggs. Presence of natamycin in shellac coating significantly inhibited fungal contamination on both commercially washed eggs and pasteurized eggs. This study illustrated that shellac coating can be used as a carrier for natamycin to create an effective protection against mold contaminations of eggs, hence the antifungal agent can potentially extend the shelf-life of treated eggs and minimize economic lose.

Committee: Ahmed Yousef (Advisor); Dennis Heldman (Committee Member); Luis Rodriguez-Saona (Committee Member) Subjects: Food Science

MS, University of Cincinnati, 2015, Engineering and Applied Science: Environmental Engineering

Phosphate, as an essential and often limiting nutrient in most aquatic ecosystems, can result in the acceleration of eutrophication; leading to increased water treatment costs, decreased recreational value, and the formation of harmful algal blooms which may pose a risk to human health due to the production of cyanotoxins. Though while viewed as a pollutant in certain scenarios, the demand of phosphate for industrial purposes is increasing; yet reserves are quickly being diminished. Therefore, the remediation and recovery of phosphate is a growing concern. One process which can both remove and recover phosphate is adsorption. Metal oxides like the iron oxide goethite have long been known to adsorb anions like phosphate, and some companies have developed commercially available, goethite-based adsorbents. This study explored the surface modification of one of these commercially available adsorbents, Bayoxide ® E33, using either manganese or silver nanoparticles to coat the solid surface to enhance the capacity of phosphate adsorption. After the synthesis of modified adsorbents, the samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution-TEM (HR-TEM), and BET surface area and zeta potential analyzers to gain insight on physical and chemical characteristics of the adsorbents. To study phosphate adsorption onto these surfaces, batch and column studies were conducted using lake water. Batch studies were carried out to explore both adsorption equilibrium and kinetic parameters. These results were modeled using several models (e.g. the Langmuir isotherm model and the pseudo-second-order model) to gain further insights into the adsorbents equilibrium and kinetics of adsorption. The Langmuir isotherm model, for example, indicate that one of the surface modified adsorbents (E33/AgII) had a slightly higher maximum amount of adsorbate remo (open full item for complete abstract)

Committee: Dionysios Dionysiou Ph.D. (Committee Chair); Mallikarjuna Nadagouda Ph.D. (Committee Member); George Sorial Ph.D. (Committee Member) Subjects: Environmental Engineering

Master of Science in Chemical Engineering, Cleveland State University, 2014, Washkewicz College of Engineering

Energy efficient waste management alternatives have been driven by environmental considerations and increasing energy demands from industrial and government developments. Among the several approaches for waste gasification including combustion/incineration, biological methods, and catalytic oxidation techniques, this study focuses on a NASA-developed technology: Catalytic Wet Thermal Oxidation (CWTO). In CWTO, the gasification of waste polymers is promoted by Ru or Pt -based catalysts at moderate to low temperatures (250-350 °C), while methods such as incineration require temperatures as high as 1000 °C. This research focuses primarily on four model polymers as low-fidelity simulants and primarily PE towards extending this technology to a continuous waste management process. It is estimated that 86% of dry waste stream comes from packaging waste (polyethylene, PE, and polyethylene terephthatalte, PET) with cellulose and nylon as the remaining components present in significant proportions. Carbon sources are investigated by Differential Scanning Calorimetry and Scanning Electron Microscopy for thermal characterization. Thermal behavior of slurries for PE is investigated in the presence of Ru-based catalyst under conditions near the critical (P and T) point for water. Similarly, High Fidelity Wastes are also investigated using a Pt-based catalyst. Batch reactor data is characterized or quantified via gas chromatography. Using this kinetic information and previous empirical evidence from literature, a conceptual phenomenological model is formulated. The model can be used to analyze process scale-up and extension to continuous gasification as a waste management alternative.

Committee: Jorge Gatica PhD (Committee Chair); Dhananjai Shah PhD (Committee Member); Sridhar Ungarala PhD (Committee Member) Subjects: Aerospace Engineering; Chemical Engineering; Engineering

PhD, University of Cincinnati, 2014, Engineering and Applied Science: Environmental Science

In this study, phenol was used in a sodium chloride or sulfate matrix as a representative pollutant to systematically study which operating conditions have the largest impact on chlorine forms in an electrochemical treatment system. Initially, an HPLC method was developed and validated to simultaneously determine phenol and potential intermediates from hydroxylation and hypochlorination pathways during electrooxidation in the presence of chloride. In a combined-reactor configured with a boron-doped diamond (BDD) anode, samples were analyzed to identify and quantify organic intermediates and inorganic chlorine species generated during the electrooxidation of phenol. Ionic strength was kept constant at 50 mM and the applied current density was 12 mA/cm2. The effects of chloride-to-phenol ratio on contaminant removal efficiency and byproduct formation were studied. Experimental results showed that phenol was removed faster at higher chloride-to-phenol ratios but more chlorinated intermediates and chlorate were produced. The impact of initial chloride concentration on the chlorate formation rate was stronger than its impact on phenol removal rate. Analysis of variance (ANOVA) was used to evaluate the statistical significance of operational factors in a full 24 factorial design. Factors studied were anode type (BDD vs. graphite), initial phenol concentration (0.25 – 0.5 mM), initial chloride concentration (5 – 50 mM) and applied current density (12 – 25 mA/cm2), on responses such as phenol removal rate and chlorate production rate. Results showed that anode type and chloride concentration had the most significant effects either individually or interactively on the phenol removal rate, and that chloride concentration had a considerable effect on the chlorate production rate. Additionally, applied current density had a significant effect on the free chlorine production rate after breakthrough if and when it occurred with BDD in the presence of excess chloride (open full item for complete abstract)

Committee: Margaret Kupferle Ph.D. P.E. (Committee Chair); Woo Hyoung Lee Ph.D. (Committee Member); Dionysios Dionysiou Ph.D. (Committee Member); George Sorial Ph.D. (Committee Member) Subjects: Environmental Engineering

Doctor of Philosophy, Case Western Reserve University, 2014, Physiology and Biophysics

Voltage-gated potassium channels have enchanted electrophysiologists for over 60 years since the pioneering work of Hodgkin and Huxley. Potassium channel inactivation is interesting biophysically since it comprises multiple distinct molecular mechanisms that can be characterized. However, inactivation is also interesting physiologically since it can impact the excitability of tissues as diverse as central neurons, pancreatic beta cells, and photoreceptors. Elucidating the molecular mechanisms underlying slow inactivation in Shaker IR and Kv2.1 channels has been the focus of this thesis. A single point mutation in Shaker IR (T449) has been shown to affect the kinetics of slow inactivation up to 100-fold. Originally, this effect was ascribed to C-type inactivation but Shaker is now known to possess two forms of slow inactivation: C-type (preferential open-state inactivation) and U-type (preferential closed-state inactivation). C-type inactivation occurs via outer-pore constriction while the mechanism of U-type inactivation remains unknown. This thesis uses established techniques of electrophysiology, pharmacology, and mutagenesis to demonstrate that mutants of Kv2.1 outer pore residue Y380 (homologous to Shaker T449) undergo U-type inactivation alone, and that mutants of Shaker T449 affect C-type inactivation alone. The study also hypothesizes that Kv2.1 channels lack C-type inactivation as it exists in Shaker IR and that C- and U-type inactivation have different molecular mechanisms. Furthermore, this study advances pore mutation as yet another tool (in addition to pharmacological and electrophysiological approaches) to help separate C- from U-type inactivation in channels with complex slow inactivation. In both Shaker and Kv2.1 channels, slow inactivation in wild-type and mutant channels was characterized with a 12-state Markov model concluding that C-type inactivation is not exclusive open-state inactivation and U-type inactivation is not exclusive closed-sta (open full item for complete abstract)

Committee: Stephen Jones Ph.D. (Advisor); Witold Surewicz Ph.D. (Committee Chair); William Schilling Ph.D. (Committee Member); Diana Kunze Ph.D. (Committee Member); Corey Smith Ph.D. (Committee Member); Isabelle Deschênes Ph.D. (Committee Member); Sudha Chakrapani Ph.D. (Committee Member) Subjects: Applied Mathematics; Biology; Biomedical Research; Biophysics; Experiments; Molecular Biology; Neurosciences; Physiology

Doctor of Philosophy (PhD), Ohio University, 2014, Chemical Engineering (Engineering and Technology)

The ammonia electrolysis process has been proposed as a feasible way for electrochemical generation of fuel grade hydrogen (H2). Ammonia is identified as one of the most suitable energy carriers due to its high hydrogen density, and its safe and efficient distribution chain. Moreover, the fact that this process can be applied even at low ammonia concentration feedstock opens its application to wastewater treatment along with H2 co-generation. In the ammonia electrolysis process, ammonia is electro-oxidized in the anode side to produce N2 while H2 is evolved from water reduction in the cathode. A thermodynamic energy requirement of just five percent of the energy used in hydrogen production from water electrolysis is expected from ammonia electrolysis. However, the absence of a complete understanding of the reaction mechanism and kinetics involved in the ammonia electro-oxidation has not yet allowed the full commercialization of this process. For that reason, a kinetic model that can be trusted in the design and scale up of the ammonia electrolyzer needs to be developed. This research focused on the elucidation of the reaction mechanism and kinetic parameters for the ammonia electro-oxidation. The definition of the most relevant elementary reactions steps was obtained through the parallel analysis of experimental data and the development of a mathematical model of the ammonia electro-oxidation in a well defined hydrodynamic system, such as the rotating disk electrode (RDE). Ammonia electro-oxidation to N2 as final product was concluded to be a slow surface confined process where parallel reactions leading to the deactivation of the catalyst are present. Through the development of this work it was possible to define a reaction mechanism and values for the kinetic parameters for ammonia electro-oxidation that allow an accurate representation of the experimental observations on a RDE system. Additionally, the validity of the reaction mechanism and kinetic paramet (open full item for complete abstract)

Committee: Gerardine Botte Ph.D. (Advisor); Valerie Young Ph.D. (Committee Member); Gang Chen Ph.D. (Committee Member); Savas Kaya Ph.D. (Committee Member); Howard Dewald Ph.D. (Committee Member) Subjects: Chemical Engineering; Chemistry; Energy; Engineering

Doctor of Philosophy, The Ohio State University, 2013, Mechanical Engineering

Kinetic studies of plasma assisted oxidation and ignition have been performed in fuel-air mixtures excited by nanosecond dielectric-barrier discharges at elevated temperatures and low pressures. The following topics have been extensively investigated: (i) accuracy of Rayleigh scattering calibration of OH Laser-Induced Fluorescence (LIF), (ii) characterization of nanosecond pulse discharges, (iii) non-thermal plasma effect on ignition delay, temperature, and OH concentration.

Committee: Igor Adamovich (Advisor); Walter Lempert (Committee Member); Bill Rich (Committee Member); Jeffrey Sutton (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2011, Mechanical Engineering

The dissertation presents an experimental study of ignition and flameholding of high speed, room temperature fuel-air flows using a diffuse, large volume, low temperature plasma produced by a repetitive nanosecond pulse discharge sustained in a cavity. Experiments are performed in premixed, partially premixed, and non-premixed ethylene-air and hydrogen-air flows in a pressure range of P = 0.2 – 0.3 atm. The dissertation also incorporates kinetic modeling of plasma assisted ignition of ethylene-air and hydrogen-air mixtures, to study the effect of radical generation in the plasma on ignition delay. The experimental results demonstrate that repetitive nanosecond pulse plasma assisted ignition occurs via formation of multiple arc filaments in the fuel-air plasma, although air plasma remains diffuse and low-temperature until the fuel is added. Comparison of ignition and flameholding achieved in premixed ethylene-air flows using a repetitive nanosecond pulse discharge and a DC arc discharge of approximately the same power (100 W) demonstrated that DC discharge resulted in sporadic ignition and flame blow-off, much lower burned fuel fraction, and significantly lower velocity (35 m/sec) at which ignition is achieved. For premixed and partially premixed near-stoichiometric ethylene-air flows, ignition and stable flameholding have been achieved up to a flow velocity of 100 m/sec at P=0.2 atm. During these experiments, nearly complete combustion is achieved. For partially premixed hydrogen-air flows, stable ignition and flameholding at P=0.2 atm has been achieved at flow velocities of up to 100 m/sec and equivalence ratios of φ=0.44-0.96. Time averaged plasma temperature measurements using nitrogen emission spectroscopy showed that the air plasma temperature is within 70° C to 200° C, while plasma temperature in presence of a stable flame is 700-1000° C. During non-premixed combustion experiments in ethylene-air at P=0.2 atm, ignition and stable flameholding is observed up t (open full item for complete abstract)

Committee: Igor Adamovich PhD (Advisor); Walter Lempert PhD (Committee Member); J. William Rich PhD (Committee Member); Mohammad Samimy PhD (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering