Download or read book Investigation of Premixed Sooting Flames by Combined Laser Induced Incandescence and Laser Induced Fluorescence written by Jaclyn Dunn and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study applies the techniques of laser induced incandescence (LII) and laser induced fluorescence (LIF) to investigate laminar sooting flames of premixed ethylene air. The approach involves using three different excitation wavelengths, together with temporally and spectrally resolved detection, generating a rich dataset concerning the formation of soot and polycyclic aromatic hydrocarbons (PAHs). Both prompt and delayed detection are used to perform LII when exciting with short wavelengths, both with issues involved. Delayed detection gives an underestimation of soot volume fraction at low heights in the flame, as a result of particle size effects. Prompt detection gives overestimation of soot volume fraction due to fluorescence in the measurement volume. It is shown that care must be taken with either method and through evaluation of the associated errors this study shows delayed detection provides a more accurate measure of soot volume fraction. The ability to obtain the fluorescence signals over a range of heights above burner and stoichiometries is demonstrated. The approach relies on heating the soot particles equivalently with three excitation wavelengths so the LII contribution to the signals can be subtracted, leaving only fluorescence. Fluorescence profiles obtained show similar features to those seen in the literature for invasive measurements, including a reduction in the fluorescence signal generated by 283 nm excitation at intermediate heights above the burner surface followed by a re-increase. Although the data do not allow species-selective measurements of PAHs, these in-situ measurements allow inferences to be drawn about changing concentration of different size classes of these precursors to soot formation. Finally the method of obtaining subtracting the LII contribution to signals was used to obtain fluorescence spectra both for 283 nm and 532 nm excitation. This showed the possibility that fluorescence can yield useful information that it is otherwise impossible to obtain in-situ under sooting conditions.

Download or read book Development of Novel Laser Diagnostic Techniques for the Quantitative Study of Premixed Flames written by Robin Simon Macpherson Chrystie and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The main topic of this thesis concerns the development and application of laser diagnostic techniques for accurate temperature measurements and for the determination of flamefront properties in premixed flames that can serve as input data for computational fluid dynamical (CFD) models in technical combustion. The work comprises of a number of related studies, to address problems of relevance in the field of combustion research. The first part of this work involves the development and testing of an improved method for the computation of flamefront curvature in lean premixed turbulent flames. Measurements of spatially resolved heat release rate along the flamefront were then compared with the curvature data and it could be shown that a significant correlation exists between local rate of heat release and flamefront curvature. The results here agree with predictions from CFD models and improve on previous experimental attempts to find a correlation between curvature and heat release. In the second part of this work, the focus was shifted towards the development and application of improved thermometry techniques. One study was on the improvement and application of a coherent anti-Stokes Raman spectroscopy (CARS) setup to an acoustically-forced turbulent lean premixed flame stabilised on a burner, whose design was modelled to mimic phenomena of relevance in industrial combustors. In a related previous study reported in the literature two-line OH planar laser induced fluorescence had been applied to this flame and it was suspected that the results were inaccurate. Using CARS, these inaccuracies could be verified, amounting to discrepancies in temperature of up to 47% compared to the true temperatures. A major effort towards the end of this project was focused on the improvement of traditional thermometry techniques, in order to make them more accurate, faster, and spatially resolved. A technique based on indium two-line atomic fluorescence (TLAF) thermometry was developed and applied, which employed a novel extended cavity diode laser design, and it was shown for the first time that temperature measurements with high accuracy and precision could be performed in low pressure sooting flames without recourse to calibration. Both the high precision and accuracy of the technique allowed for the deduction that the temperature in the flames studied here is relatively insensitive to changes in pressure in stark contrast to the soot volume fraction. Finally, it is shown for the first time that low power diode lasers can be used in combination with indium TLAF to measure spatially and temporally highly resolved temperatures in a quasi-continuous fashion. We demonstrated such measurements at effective rates of 3.5 kHz in a steady laminar test flame yielding an unprecedented precision of 1.5 % at ~2000 K at this measurement rate.

Download or read book Laser Induced Fluorescence Measurements and Modeling of Nitric Oxide in High Pressure Premixed Flames written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-25 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser-induced fluorescence (LIF) has been applied to the quantitative measurement of nitric oxide (NO) in premixed, laminar, high-pressure flames. Their chemistry was also studied using three current kinetics schemes to determine the predictive capabilities of each mechanism with respect to NO concentrations. The flames studied were low-temperature (1600 less than T less than 1850K) C2H6/O2/N2 and C2H6/O2/N2 flames, and high temperature (2100 less than T less than 2300K) C2H6/O2/N2 flames. Laser-saturated fluorescence (LSF) was initially used to measure the NO concentrations. However, while the excitation transition was well saturated at atmospheric pressure, the fluorescence behavior was basically linear with respect to laser power at pressures above 6 atm. Measurements and calculations demonstrated that the fluorescence quenching rate variation is negligible for LIF measurements of NO at a given pressure. Therefore, linear LIF was used to perform quantitative measurements of NO concentration in these high-pressure flames. The transportability of a calibration factor from one set of flame conditions to another also was investigated by considering changes in the absorption and quenching environment for different flame conditions. The feasibility of performing LIF measurements of (NO) in turbulent flames was studied; the single-shot detection limit was determined to be 2 ppm. Reisel, John R. and Laurendeau, Normand M. Unspecified Center NASA-CR-195404, E-9248, NAS 1.26:195404 NAG3-1038; RTOP 537-02-20...

Download or read book Laser Induced Incandescence Imaging for the Investigation of Soot Formation in Laminar Flames written by Robert Gray Roy and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser Diagnostics for High Pressure Combustion written by David Escofet-Martin and published by . This book was released on 2017 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser diagnostics have been a staple for experimental combustion research as a modern tool to evaluate high temperature reacting flow environments and to contribute to the fundamental knowledge needed for improving our current combustion systems in a non-intrusive way; they also represent an essential tool for validating computational models. High pressure diagnostics are of particular importance due to the fact that the majority of practical combustion systems operate at high pressure, involving increased challenges in the measurements. The current work examines a variety of linear and non-linear light/matter interaction processes (Raman, fluorescence, and coherent anti-Stokes Raman spectroscopy or CARS) with the goal of measuring the temperature, pressure, and spatial distribution of important reacting flow species. The specific techniques involving OH planar laser induced fluorescence (PLIF), two-line OH PLIF thermometry, two-photon CO PLIF, nanosecond vibrational CARS and hybrid femtosecond/picosecond rotational CARS are all demonstrated at atmospheric pressure using a non-premixed coflow impinging jet as a study flame and examined in detail under high pressure conditions (up to 12 bar) as a coflow flame and in a calibration high pressure vessel; the implications of pressure are discussed in detail in the linear and non-linear techniques. The high pressure experimental data set shows soot laser induced incandescence (LII) as a source of interference for high pressure LIF in non-premixed flames, good agreement with 3 different chemical mechanisms, in particular at high pressure, between an OpenFOAM simulated fluorescence and the experimental pressure dependent data regarding both the spatial distribution of the OH molecule and the overall number of $OH$ molecules interacting with the excitation source. Chirp is identified as a critical parameter when using a second harmonic bandwidth compressor in the hybrid fs/ps CARS configuration, and the chirped CARS signal depends strongly on probe delay in N2 experiments. High quality high pressure data can be achieved once chirp influence has been quantified accurately. Together the combination of diagnostics studied provide insights into high pressure laser diagnostics challenges beyond what is currently available.

Download or read book Experimental Study of Soot Formation in Laminar Premixed Flames of Fuels of Interest for Automobile and Aeronautics written by Christopher Betrancourt and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emission of soot formed from incomplete combustion of fossil fuels, biofuels and biomass is a serious concern due to soot's harmful impact on human health, environment and its radiative forcing on climate. Gaining fundamental understanding of soot formation, particularly the nucleation step leading to the formation of the nascent soot particles, is critical to develop reliable predictive soot models and to help the design of more efficient and cleaner combustion devices. This work demonstrates that nascent soot particles in the size range of 2-4 nm are able to emit a black body radiation by combined Laser Induced Incandescence (LII), scanning mobility particle sizer (SMPS) and helium-ion microscopy (HIM). These nascent soot particles are investigated in nucleation premixed flames in which soot particles are essentially formed by nucleation, without growth by soot surface processes and in standard sooting premixed flames in which growth processes occur. This work provides an extensive database for improvement of kinetics modelling of sooting flames with a focus on the soot nucleation in flames. Two kinds of fuels have been selected: n-butane and mixture of n-butane and n-propylbenzene. For each fuels two flames have been studied: a nucleation and a standard sooting flames. The database consist of species profiles obtained by online gas chromatography, temperature profiles measured by Laser induced fluorescence thermometry, soot volume fraction profiles obtained by LII calibrated by cavity ring-down extinction and particles size distributions obtained in n-butane flames by SMPS and HIM. From this database effect of equivalence ratio and fuel composition is analyzed.

Download or read book Laser Induced Fluorescence Measurements and Modeling of Nitric Oxide in High pressure Premixed Flames written by and published by . This book was released on 1994 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Applied Combustion Diagnostics written by KoHse-HoingHaus and published by CRC Press. This book was released on 2002-04-26 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt: The editors have assembled a world-class group of contributors who address the questions the combustion diagnostic community faces. They are chemists who identify the species to be measured and the interfering substances that may be present; physicists, who push the limits of laser spectroscopy and laser devices and who conceive suitable measurement schemes; and engineers, who know combustion systems and processes. This book assists in providing guidance for the planning of combustion experiments, in judging research strategies and in conceiving new ideas for combustion research. It provides a snapshot of the available diagnostic methods and thier typical applications from the perspective of leading experts in the field.

Download or read book Investigation of Laser induced Incandescence and Soot Vaporization Using Time Resolved Light Scattering in a Propane Diffusion Flame written by Gregory David Yoder and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Laser-induced incandescence is a technique that uses a pulsed laser beam to heat soot particles up to levels far above the background, causing them to emit radiation as essentially blackbodies, which can then be related to the total soot volume using suitable calibration schemes. However, the temperature reached by the laser-heated particles may cause the particles to begin to vaporize, thereby changing the parameter of interest, namely the total soot volume. The primary goal of this thesis is to investigate the particle vaporization due to LII using time-resolved laser light scattering. Based on the experimental measurements in a sooting propane diffusion flame, significant particle vaporization was found to occur on the time scale of the LII laser pulse. A model was developed to describe the particle temperature and volume as the particles are heated up and vaporized by the LII laser and as the particles subsequently cooled. This heat transfer model uses a fundamental energy balance along with the Planck distribution to model the LII signal as a function of time, and was then used to estimate the influence of particle vaporization on the time-resolved LII signal.

Download or read book Investigation of Turbulent Flame Characteristics Via Laser Induced Fluorescence written by Sunil Kumar Omar and published by . This book was released on 2006 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser saturated Fluorescence Measurements in Laminar Sooting Diffusion Flames written by Changlie Wey and published by . This book was released on 1993 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hydroxyl radical is known to be one of the most important intermediate species in the combustion processes. The hydroxyl radical has also been considered a dominant oxidizer of soot particles in flames. In this investigation the hydroxyl concentration profiles in sooting diffusion flames were measured by the laser-saturated fluorescence (LSF) method. The temperature distributions in the flames were measured by the two-line LSF technique and by thermocouple. In the sooting region the OH fluorescence was too weak to make accurate temperature measurements. The hydroxyl fluorescence profiles for all four flames presented herein show that the OH fluorescence intensities peaked near the flame front. The OH fluorescence intensity dropped sharply toward the dark region of the flame and continued declining to the sooting region. The OH fluorescence profiles also indicate that the OH fluorescence decreased with increasing height in the flames for all flames investigated. Varying the oxidizer composition resulted in a corresponding variation in the maximum OH concentration and the flame temperature. Furthermore, it appears that the maximum OH concentration for each flame increased with increasing flame temperature.

Download or read book Use of Laser Induced Ionization to Detect Soot Inception in Premixed Flames written by S. L. Manzello and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soot Formation in Combustion written by Henning Bockhorn and published by Springer Science & Business Media. This book was released on 2013-03-08 with total page 595 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soot Formation in Combustion represents an up-to-date overview. The contributions trace back to the 1991 Heidelberg symposium entitled "Mechanism and Models of Soot Formation" and have all been reedited by Prof. Bockhorn in close contact with the original authors. The book gives an easy introduction to the field for newcomers, and provides detailed treatments for the specialists. The following list of contents illustrates the topics under review:

Download or read book Laser Induced Fluorescence Measurements and Modeling of Nitric Oxide in Counterflow Diffusion Flames written by and published by . This book was released on 2000 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Application of Laser Induced Fluorescence in an Atmospheric Pressure Boron Seeded Flame written by Greg R. Schneider and published by . This book was released on 1987 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this research was to demonstrate the feasibility of using laser-induced fluorescence (LIF) of boron oxide radicals in atmospheric-pressure flames. Such a demonstration would provide a useful tool with which to probe the detailed combustion chemistry of boron fuels. The radical species sought were BO2 and BO, both having spectra in the visible region of the spectrum. These two species are believed to play critical roles in the boron combustion process. A CH4/air/O2 flame was seeded with BC13 producing the green emission characteristic of boron flames. Unfortunately, it also created significant quantities of aerosols of solid boric acid from the reaction of the BC13 with the water vapor in the building air used in the flame. The burner was 1 cm in diameter and composed of approximately 60 capillary tubes. The burner could be remotely translated in two directions permitting investigation of different regions of the flame.

Download or read book Laser induced Fluorescence Radical Measurements in Partially Premixed Bunsen type Methane Flames written by Norbert H. Heberle and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser induced Incandescence for Soot Diagnostics written by and published by . This book was released on 2012 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: