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| Author | : Xing Rao |
| Publisher | : |
| Total Pages | : 133 |
| Release | : 2010 |
| Genre | : Electronic dissertations |
| ISBN | : 9781124371467 |
| Author | : Caroline Winters |
| Publisher | : |
| Total Pages | : 228 |
| Release | : 2017 |
| Genre | : Aerospace engineering |
| ISBN | : |
This work has produced extensive sets of new data on low-temperature plasma-assisted fuel oxidation in hydrogen-oxygen-argon and hydrocarbon-oxygen-argon mixtures. The measurements have been made in two different plasma flow reactors, at an initial temperature of 500 K and pressures ranging from 300 Torr to 700 Torr. In both reactors, the plasma is generated by a high peak voltage, ns pulse discharge, operated at high pulse repetition rates (up to 20 kHz). Metastable Ar atom number density distributions in the discharge afterglow are measured by Tunable Diode Laser Absorption Spectroscopy (TDLAS), and used to characterize plasma uniformity. Temperature in the discharge-excited reacting flow is measured by Rayleigh scattering. Two-photon Absorption Laser Induced Fluorescence (TALIF) is used to measured absolute H and O atom number densities. The results are compared with predictions of a kinetic model analyzing reaction kinetics of excited species and radicals generated by the plasma at low temperatures and high pressures. The modeling predictions show good agreement with the data, with the exception of fuel-limited mixtures, when nearly all fuel available in the mixture of reactants is oxidized in the discharge. Kinetic modeling analysis identified dominant processes of generation and decay of atomic and radical species in the discharge and in the afterglow. At the present low-temperature conditions, the effect of chain branching reactions on plasma-assisted fuel oxidation kinetics is insignificant.
| Author | : |
| Publisher | : |
| Total Pages | : 10 |
| Release | : 1996 |
| Genre | : |
| ISBN | : |
Plasma assisted chemical vapor deposition (PACVD) represents a novel approach for utilizing the nonequilibrium effects of reactive plasmas for depositing a wide range of protective hardface coatings that have both wear and erosion application. The nonequilibrium plasma is the heart of this complex system and has the function of generating the reactive molecular fragments (radicals) and atomic species at concentration levels unattainable by other competing processes. It is now widely accepted that such advanced protective hardface coatings materials will play a vital role in the energy technologies of the coming decades, with major applications in diverse areas ranging from aerospace and commercial propulsion systems (jet engines) to automotive components and internal combustion engines, (ceramic heat engines), cutting and machining tools, electronic packaging, thermal management, and possibly room-temperature superconductors. Wear and associated erosion aspects are responsible for an enormous expenditure of energy and fiscal resources in almost all DOE applications. Many of the results from this investigation arc also applicable to other materials processing reactors such as electron beam, PVD, CVD, laser ablation, microwave, high energy cathodic arc, thermal plasma (rf or dc) and combustion spray. These also include the various hybrid systems such as the rf/dc arc as used in Japan for diamond deposition and e-beam PVD deposition of advanced titanium alloy coatings as used at the Paton Institute in Kiev, Ukraine.
| Author | : |
| Publisher | : |
| Total Pages | : 9 |
| Release | : 2008 |
| Genre | : |
| ISBN | : |
A Particle Imaging Velocimetry (PIV) system, an Imaged Intensified CCD (ICCD) camera (PI-MAX), an infrared laser diode, an oscilloscope, and a boxcar Integrator were purchased for the diagnostics of combustion and ignition enhancement using the non-equilibrium plasma and for the species measurements in non-premixed flames using JP-8 surrogate fuels. The systems were integrated into the existing Nd-YAG and Cobra-Stretch dye lasers, as well as the plasma assisted combustion burners. OH concentrations, O3 and O(1D) emissions, temperature distributions in plasma assisted combustion were measured by using the planar laser induced fluorescence, emission spectroscopy, and Rayleigh scattering. The flow field and flame speeds of surrogate fuel-air premixed flames were measured by using the PIV system. A new diagnostic method for simultaneous measurement of flow velocity and temperature by using PIV technique together with nanophosphor emissions is under development. The purchased experimental equipment significantly increased the experimental capabilities for quantitative measurements of intermediate species in plasma assisted combustion and contributed to the advancement of fundamental understanding of non-equilibrium plasma assisted combustion.
| Author | : |
| Publisher | : |
| Total Pages | : 91 |
| Release | : 2015 |
| Genre | : |
| ISBN | : 9789176234624 |
| Author | : K Muraoka |
| Publisher | : CRC Press |
| Total Pages | : 307 |
| Release | : 2016-04-19 |
| Genre | : Science |
| ISBN | : 1420034065 |
Updated and expanded from the original Japanese edition, Laser-Aided Diagnostics of Gases and Plasmas takes a unique approach in treating laser-aided diagnostics. The book unifies the subject by joining applications instead of describing each application as a totally separate system. In taking this approach, it highlights the relative strengths of
| Author | : Che Amungwa Fuh |
| Publisher | : |
| Total Pages | : 148 |
| Release | : 2018 |
| Genre | : |
| ISBN | : |
Plasmas when coupled to the oxidation process of various fuels have been shown to influence the process positively by improving upon flameholding, reduction in ignition delay time, reduced pollutant emission, etc. Despite all this positive effects being known to the science community, the mechanisms through which the plasmas effects all these enhancements are poorly understood. This is often due to the absence of accurate experimental data to validate theoretical mechanisms and the availability of a myriad sources of plasmas having different chemistries. The goal of this thesis is to further narrow the knowledge gap in the understanding of plasma assisted combustion by using a nonthermal microwave plasma to investigate the mechanism through which it enhances the oxidation of several fuel/oxidant combinations. The enhancement metrics used in this studies are minimum ignition energy, flameholding and rotational temperature. A suite of noninvasive optical diagnostics techniques (camera for visual imaging, optical emission spectroscopy and cavity ringdown spectroscopy) are employed to probe the plasma assisted combustion flame and identify the species, obtain rotational temperatures, and identify pathways through which the microwave plasma enhances the combustion process. Initially, the effect of a microwave plasma on the ignition and flameholding of an ethylene/air mixture was investigated. Then, based on observations from that study and previous studies, a novel plasma assisted combustion platform was designed capable of discriminating between the various pathways through which the plasma enhances the combustion of a fuel/air mixture. Using the designed platform, a comparative study was carried out on the roles played by the plasma activated fuel vs. plasma activated oxidizer stream. The roles played by the plasma activated fuel or air molecules in the ignition of the fuel/air mixture was investigated. Data from this study led to the suggestion that there exist a minimum required plasma generated radical pool for ignition to occur with reactive oxygen and nitrogen playing a more important role in the ignition and flameholding effects. Ground state OH(X) number densities were also measured for the first time in the hybrid ignition zone of a plasma assisted combustion reactor using cavity ringdown spectroscopy.
| Author | : Yupan Bao |
| Publisher | : |
| Total Pages | : |
| Release | : 2022 |
| Genre | : |
| ISBN | : 9789189391574 |
Optical diagnostics techniques based on coded imaging were developed and applied for plasma-related phenomena and applications. The signal of interest is first encoded with a sinusoid pattern either by structured laser illumination or implement of a diffractive optical element, such as a grating, along the optical path of the signal. The coded signal will then be extracted from the raw data by a lock-in based algorithm, such as frequency recognition algorithm for multiple exposures (FRAME). Two types of non-thermal plasma sources, i.e., gliding arc discharges and nanosecond pulsed discharges, were investigated. Volumetric information of molecular distributions around a gliding arc was captured using laser-induced fluorescence with structured illumination and FRAME. Laser scattering imaging during the formation of a nanosecond pulsed discharge on a at methane-air flame was extracted from luminous plasma emission using structured laser illumination. Furthermore, a technique named periodic shadowing was applied for streak camera measurements, where both higher temporal contrast and effective dynamic range were achieved. The gliding arc plasma discharge was also applied in an industrial prototype burner as plasma-assisted combustion has been proven to be a promising technique to increase energy efficiency as well as reduce environmentally harmful emission. With the help of 0.1% additional energy, the lean blow-out limit of a hundred kilowatt burner was extended from a global equivalence ratio of 0.47 to 0.45.
| Author | : Alan C. Eckbreth |
| Publisher | : CRC Press |
| Total Pages | : 630 |
| Release | : 2022-01-27 |
| Genre | : Technology & Engineering |
| ISBN | : 1000124622 |
This book examines the variety of potential laser diagnostic techniques and presents a considerable theoretical foundation elucidating physics relevant to the laser diagnostics. It explains the Raman-based approaches for major species and temperature measurements.
| Author | : |
| Publisher | : |
| Total Pages | : 37 |
| Release | : 1997 |
| Genre | : |
| ISBN | : |
Significant milestones for quantitative laser-based diagnostics of reacting flows were reached on two separate tasks: (1) the extension of laser-based diagnostics to shorter vacuum ultraviolet (vuv) wavelengths and (2) the development of amplified spontaneous emission (ASE) diagnostics for light atoms. For the first task, phase-matching was applied to produce significant increases in vuv laser intensities, producing over 5 mu J at Lyman alpha (121.6 nm) in a mixture of krypton and argon. Factors affecting the long-term stability of vuv powers were studied. The diagnostic potential of two-photon excited ASE of atomic hydrogen and oxygen was explored in a variety of low-pressure flames. Direct ASE gain measurements gave oxygen concentrations. A model of the ASE signal was developed, and a new understanding of both ASE and laser-induced fluorescence of two-photon excited atoms emerged from this model.
