Laminar flat flame combustion has been studied with molecular-beam mass-spectrometry (MBMS) for a fuel-rich cyclohexane (Ф = 2.003) flame, a fuel-lean toluene (Ф = 0.895), and a fuel-rich toluene (Ф = 1.497) flame. Different hydrocarbon species in these flames were identified, and their mole fraction profiles were measured. The information can be used to propose reaction mechanisms for the different hydrocarbon flames. One MBMS apparatus located at Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory was used to identify and measure the mole-fraction profiles of different species in these flames. The MBMS apparatus located at University of Massachusetts Amherst was used to measure the temperature profile of the cyclohexane flame. The temperature profile of two different fuel-rich toluene flames (Ф= 2.02 , Ф = 3.94) and a fuel-lean (Ф=0.452) methane flame were also measured with the UMass apparatus.

Computed tomography for flame chemiluminescence emissions allows for 3D spatially resolved flame measurements to be acquired using a series of discrete viewing angle camera images. To determine fuel/air ratios, the ratio of excited radical species (OH*/CH*) emissions using chemiluminescence can be employed. Following the process of high-resolution tomography reconstructions in this work allowed for flame tomography coupled with chemiluminescence emissions to be used for spatially resolved phase averaged equivalence ratio measurements. This is important as variations in local equivalence ratios can have a profound effect on flame behavior including but not limited to thermoacoustic instability, NOx and CO formation, and flame stabilization. Local equivalence ratios are determined from a OH*/CH* ratio of tomographically reconstructed intensity fields and relating them to equivalence ratio. The correlation of OH*/CH* to equivalence ratio is derived from an axisymmetric, commercially available flat flame burner (Holthuis and Associates Burner). To relate intensity field imaging (camera coordinate system) during the tomographic reconstruction to the real-world coordinate system of the burner a calibration procedure was performed and then validated. A calibration plate with 39 non-coplanar points was used in this procedure. It was then validated by comparing the Abel inverted flame images of the axisymmetric Holthuis and Associates burner with the tomographic reconstructed images. Results show a successful tomographic reconstruction of thermoacoustic self-excited cycle concluding equivalence ratio fluctuations coinciding with the 1st dominate frequency of the pressure fluctuations and influenced by a 2nd harmonic frequency. / Master of Science / In recent years tomographic reconstruction of flames have gained significant focus in understanding different flame phenomenon. One specific flame phenomenon is known as a thermoacoustic instability. Using highspeed cameras for chemiluminescence imaging of specific species can help define heat release rate, air/fuel ratio/equivalence ratio spatially. Coupling of pressure measurements to imaging methods can be used to determine the flames response to acoustic perturbations in the flow field. Every optics system has inherently different light transmission characteristics and therefore, needs to be calibrated/correlated using a known flame source. The work done in this paper used a Holthuis and Associates flat flame as the known flame source in conjunction with an optics system to correlate OH*/CH* ratio to equivalence ratio. This is possible due to the perfectly premixed nature the flat flame provides. The correlation curve for the optics system is then applied to the tomographically reconstructed chemiluminescence intensities during a self-excited thermo-acoustic instability. In addition, a flat flame burner was used to validate the tomography approach and calibration procedure. In conclusion the objective of this work develops and validates a method for use in tomographic reconstruction of spatially varying equivalence ratios.

Thin filament pyrometry is a proven technique used to measure flame temperature by capturing the spectral radiance produced by the immersion of silicon carbide filaments in a hot gas environment. In this study a commercially available CMOS color camera was used, and the spectral response of each color channel was integrated with respect to the assumed graybody radiation spectrum to form a look up table between color ratio and temperature. Interpolated filament temperatures are then corrected for radiation losses via an energy balance to determine the flame temperature. Verification of the technique was performed on the Holthuis and Associates Flat Flame Burner, formerly known as the Mckenna Burner, and the results are directly compared to literature values measured on a similar burner. The results are also supported by radiation corrected measurements taken using a type B thermocouple on the same burner setup. An error propagation analysis was performed to determine which factors contribute the most to the final measurement uncertainty and confidence intervals are calculated for the results. Uncertainty values for a single point measurement were determined to be between ±15 and ±50 K depending on the color ratio and the total uncertainty associated with day-to-day changes in the measurement setup was found to be ±55 K. / Master of Science / Determination of flame temperature is an important aspect of combustion research and is often critical to the evaluation of combustion systems as well as the integration of those systems into more complex devices. In this thesis the technique of thin filament pyrometry was implemented and verified through the use of a well characterized calibration flame. This technique involves placing thin filaments usually made from silicon carbide into the flame and capturing the spectrum of light they emit with a detector. Since the amount of light emitted as well as which wavelengths the light is concentrated in is a strong function of temperature, this methodology may be used to calculate the temperature of the flame. Thin filament pyrometry has the advantage compared to other techniques in that it is extremely cheap to implement and requires no advanced scientific equipment. The SiC filaments have been shown to have a very high resistance to the flame environment and do not face many of the same challenges that can cause problems for other techniques. A statistical analysis of the method implemented in this work was also performed and the expected uncertainty was similar to many of the alternative techniques which necessitate a more complex or expensive setup.

Current operational wildland fire models are based on numerous correlations from experiments performed on dry (dead) fuel beds. However, experience has shown distinct differences in burning behaviors between dry and moist (live) fuels. To better understand these fundamental differences, an experiment was designed to use a flat-flame burner to simulate a moving fire front which heated and ignited a stationary, individual fuel sample. Samples included various U.S. species from the California chaparral, the intermountain west, and the southeastern regions. Temperature, mass, and video images were recorded throughout each experimental run from which numerous data values were obtained such as time to ignition, ignition temperature, flame height, time of flame duration, and mass release rates. Qualitative results showed various phenomena such as color change, bubbling, bursting, brand formation, and bending; these phenomena were species-dependent. Quantitative results showed differences in the ignition values (time, temperature, and mass) among species. It was observed that all moisture did not leave the interior of the sample at the time of ignition. Also, from the temperature history profiles, no plateau was observed at 100°C, but instead at 200-300°C. This indicates a need to treat evaporation differently than the classical combustion model. Samples were treated with solvents in attempt to extract the cuticle from the surface. These treated samples were compared to non-treated samples, though no significant combustion characteristics were observed. The time of color change for the treated samples varied significantly, indicating that the cuticle was indeed removed from the surface. Two-leaf configurations were developed and compared to determine combustion interactions between leaves. A second leaf was placed directly above the original leaf. Results showed that the time of flame duration of the upper leaf was significantly affected by the presence of the lower leaf. Causes for the prolonged flame were found to be the consumption of O2 by the lower leaf and the obstruction provided by the lower leaf, creating a wake effect which displaced hot gases from the flat-flame burner as well as entrained surrounding room temperature gas. A semi-physical model based on fluid dynamics and heat and mass transfer was developed that included the observed plateau at 200-300°C, rather than at 100°C; this was done for both the single- and two-leaf configurations. Another model using a statistical approach was produced which described the combustion of a bush that incorporated data obtained from the experimental results. Overall burning times and percentage of fuel consumption were obtained for various fuel loadings using this statistical model.

Les suies et les hydrocarbures polyaromatiques, qui sont émis à l’échappement des moteurs Diesel, constituent une part importante de la pollution urbaine. Depuis plusieurs années, de nombreuses recherches ont permis de progresser dans le domaine de la cinétique de la combustion des hydrocarbures qui est maintenant relativement bien connue. Il reste néanmoins des zones d’ombre concernant la formation des composés aromatiques (benzène, toluène,…) et des hydrocarbures aromatiques polycycliques (HAP) dont la formation provient d’espèces composées de deux à six atomes de carbone et qui mènent directement ou indirectement à la formation des suies.L’allène, le propyne, le butadiène et le cyclopentène sont des produits intermédiaires importants de la combustion dans les moteurs. Dans ce contexte, ce travail de thèse a permis de mieux comprendre les voies réactionnelles importantes dans la formation du benzène et du toluène. Le chapitre I de ce mémoire présente une revue bibliographique des travaux antérieurs sur l’oxydation du méthane, de l’allène, de propyne, de 1,3-butadiène et du cyclopentène. Le chapitre II présente une description détaillée du montage expérimental utilisé durant cette étude afin d’étudier la structure de la flamme laminaire de prémélange. Les chapitres III, IV et V présentent les résultats expérimentaux obtenus en flamme laminaire de prémélange, ainsi qu’une comparaison avec des simulations effectuées à l’aide de mécanismes réactionnels élaborés durant ce travail de thèse / Soots and polyaromatic hydrocarbons (PAH), which are present in the exhaust gas of diesel engines, represent a large part of the urban pollution. Many efforts have then been focused on reducing the emissions of these compounds. The formation of soot precursors and PAH in combustion involves small unsaturadted hydrocarbons the chemistry of which is still very uncertain. Allene, propyne, 1,3-butadiene and cyclopentene are intermediate products in the combustion in cars engines. This work has led to a better understanding of several important paths in the formation of benzene and toluene. The chapter I of this report presents a bibliographic review of former work on the oxidation of methane, allene, propyne, 1,3-butadiene and cyclopentene. Chapter II gives a detailed description of the experimental set up used during this work to study the structure of the premixed flat laminar flames. Chapters III, IV and V present our experimental results obtained in laminar premixed flat flames and also the comparison with simulations

Le secteur des transports est soumis à des réglementations sévères visant à limiter les émissions polluantes à l’échappement. Les biocarburants ont reçu une attention particulière en tant que carburant de substitution ou additif aux carburants traditionnels dans l’espoir de remédier aux problèmes de l’épuisement des ressources fossiles et des émissions de certains polluants. Cette thèse a pour objectif principal d’étudier l’impact de l’incorporation des biocarburants oxygénés ou synthétiques aux carburants traditionnels sur les émissions de polluants non réglementés à savoir les composés carbonylés (aldéhydes et cétones) et les hydrocarbures aromatiques polycycliques (HAPs) adsorbés sur la suie. Dans un premier temps, une étude a été menée dans une chambre de combustion interne. Les prélèvements des gaz à l’échappement suivis par les analyses chromatographiques en phase liquide ont permis d’évaluer l’effet de l’additivation du carburant sur les émissions de composés carbonylés. Une deuxième étude a été menée au moyen d’un brûleur à flamme plate permettant de collecter des suies de flammes riches dans des conditions stabilisées. Les mesures effectuées ont permis de déterminer l’effet de l’incorporation des biocarburants oxygénés au carburant sur la production de suie et le contenu d’HAPs adsorbés. Ce travail a été complété par l’étude de la cinétique d’oxydation de trois additifs oxygénés à l’état pur en réacteur auto-agité à pression atmosphérique et dans un large domaine de températures (530-1280 K) et de richesses (0,5-4). Les profils de concentration des réactifs, produits et principaux intermédiaires stables ont été obtenus par spectrométrie infrarouge à transformée de Fourrier (IRTF) et chromatographie en phase gazeuse. Ces résultats ont été ensuite confrontés aux profils d’espèces obtenus par simulation, à l’aide des modèles cinétiques d’oxydation disponibles dans la littérature. / The transport sector is subject to strict regulations aiming at limiting pollutants emissions. Biofuels have received particular attention as alternative fuel or additive to traditional fuels for remedying two issues: the depletion of fossil resources and emissions of certain pollutants. In this work we studied the impact of blending conventional fuels with synthetic or oxygenated biofuels on the emissions of non-regulated pollutants, namely carbonyl compounds (aldehydes and ketones) and polycyclic aromatic hydrocarbons (PAHs) adsorbed on soot. Firstly, the carbonyl compounds emissions were studied using an internal combustion engine. The carbonyls were collected at the exhaust of a diesel engine running with biofuel blends and analyzed using high performance liquid chromatography. Secondly, the impact of blending the conventional fuel with oxygenated biofuels on soot formation and adsorbed PAHs were studied using a flat flame burner under well stabilized conditions. This work was completed by the study of the kinetics of oxidation of three oxygenated additives in a jet-stirred reactor at atmospheric pressure, over the temperature range 530-1280 K and for different equivalence ratios (0.5-4). The concentration profiles of reactants, products and main stable intermediates were obtained by probe sampling and gas analyses including Fourier transform infrared spectroscopy (FTIR) and gas phase chromatography. These results were then compared to simulated species concentration profiles obtained using oxidation kinetic models available from the literature.

This thesis is concerned with the development and application of laser induced thermal grating spectroscopy (LITGS) as a tool for thermometry in reacting and non-reacting flows. LITGS signals, which require resonant excitation of an absorbing species in the measurement region to produce a thermal grating, are acquired for systematic measurements of temperature in high pressure flames using OH and NO as target absorbing species in the burned gas. The signal obtained in LITGS measurements appears in the form of a time-based signal with a characteristic frequency proportional to the value or the sound speed of the local medium. With knowledge of the gas composition, the temperature can be derived from the speed of sound measurement. LITGS thermometry using resonant excitation of OH in the burned gas region of in oxygen enriched CH4/O2/N2 and CH4/air laminar flames was performed at elevated pressure (0.5 MPa) for a range of conditions. Measurements were acquired in oxygen enriched flames to provide an environment in which to demonstrate LITGS thermometry under high temperature conditions (up to 2900 K). The primary parameters that influence the quality of LITGS signal were also investigated. The signal contrast, which acts as a marker for the strength of the frequency oscillations, is shown to increase with an increase in the burnt gas density at the measurement point. LITGS employing resonant excitation of NO is also demonstrated for quantitative measurements of temperature in three environments – a static pressure cell at ambient temperature, a non-reacting heated jet at ambient pressure and a laminar premixed CH4/NH3/air flame operating at 0.5 MPa. Flame temperature measurements were acquired at various locations in the burned gas close to a water-cooled stagnation plate, demonstrating the capability of NO-LITGS thermometry for measuring the spatial distribution of temperature in combustion environments. In addition, the parameters that in influence the local temperature rise due to LITGS were also investigated in continuous vapour flows of acetone/air and toluene/air mixtures at atmospheric conditions. Acetone and toluene are commonly targeted species in previous LITGS measurements due to their favourable absorption characteristics. Results indicate that LITGS has the potential to produce accurate and precise measurements of temperature in non-reacting flows, but that the product of the pump intensity at the probe volume and the absorber concentration must remain relatively low to avoid significant localised heating of the measurement region.