Dissertations / Theses on the topic 'Flame behavior'

The goal of this work was to identify the mechanisms that effect stabilization of hydrocarbon jet flames. Methane, nitrogen, and co-flowing air were regulated and directed through a burner that created fully-developed fuel flow with concurrent air. The behavior of the reaction zone at the leading-edge was analyzed from digital images obtained from a camera optimally positioned to capture the movements of the entire flame front. Low Reynolds number flows allowed for the investigation of hysteretic behavior. The hysteresis regime refers to the situation where the jet flame has dual positions favorable to flame stabilization: attached and lifted. Results indicate that flame height in hysteresis is significantly impacted by high velocities of co-flow and that past a critical value a local minimum will be created. Fully turbulent lifted flames were also studied to determine the fluctuations in the height of lifted methane flames in the presence of air co-flow. The partially-premixed flame front of the lifted flame fluctuates in the axial direction, with the fluctuations becoming greater in flames stabilized further downstream. These fluctuations are also observed in flames where blowout is imminent. The height and rate of these fluctuations are studied with respect to average height, flow velocities, and Reynolds number. Additionally, the mechanisms that cause jet-flame blowout, particularly in the presence of air co-flow, are not completely understood. Two types of experiments are described, and the data report that a predictor of blowout is the prior disappearance of the axially-oriented flame branch which is consistently witnessed despite a turbulent flameâs inherent variable behavior. The conclusions are supported by experiments with nitrogen-diluted flames. A blowout parameter is also calculated for methane flames in co-flow and diluted methane flames that can be used to predict at what flow velocities blowout will occur. This work analyzes flames near the burner, in the far field, and approaching blowout. The comprehensive study allows for the realization that the mechanisms of flame stabilization differ throughout the combustible field.

The acoustic source structure, acoustic farfield, and duct terminating impedances fully describe the acoustics of a source within a duct. A main goal in the study of noise generated by turbulent combustion is to characterize the structure of the flame as an acoustic source. Data describing the farfield and duct terminating conditions allow for the testing of combustion noise models. The acoustic farfield of a premixed flame burner is documented for various power levels and air-to-fuel ratios. The terminating impedance of the burner exhaust is determined by a method using the transfer function between two microphones that communicate with the acoustic field inside the duct. High temperature probes isolate the microphones from extreme temperatures within the duct while only slightly distorting the results. The real part of the terminating impedance agrees with a correlation in the literature for hot flow leaving a duct.
M.S.

A challenge for fire researchers is obtaining data from those fires that are most dangerous and costly. While it is feasible to instrument test beds, test plots, and small prescribed burns for research, it is uncommon to successfully instrument an active wildland fire. With a focus on very specific facets of wildland fire, researchers have created many unique models utilizing matchsticks, cardboard, liquid fuel, excelsior, plywood, live fuels, dead fuels, and wood cribs of different packing densities. Such scale models, however, only serve as valid substitutes for the full-scale system when all functional relations of the scale model are made similar to corresponding relations of the original phenomena. The field of study of large wildland fires therefore was in need of a framework that researchers could use to relate the results from many previous experiments to full-scale wildland fires; this framework was developed during the research for this dissertation. This further work developing laws for instability scaling in wildland settings was founded on the established work in dynamic similitude of G.I. Taylor, H. C. Hottel, F. A. Williams, R. I. Emori, K. Saito and Y. Iguchi. Additionally, in this work, a new dynamic flame parameter was incorporated into the scaling laws for fires that had not previously been assessed and proved to provide additional, important insight into flame spread. The new dynamic parameter enabled improved St-Fr correlations and was established for a wide range of fire sizes and fuel types.

This paper summarizes research on the structural perfomance of wood elements and assemblies exposed to fire and reviews methodologies available to predict performance. This reasecrh provides a wealth of information on topics such as how fast a flame spreads across the surface of wood, how much smoke is produced during combustion and at what rate does wood char and at what heat release rate.

Wildland fuels and fire behavior have been the focus of numerous studies and models which provide operational support to firefighters. However, fuel and fire complexity in live shrubs has resulted in unexpected and sometimes aggressive fire behavior. The combustion of live fuels was studied and modeled, and the results were assimilated into a shrub-scale fire behavior model which assumes fire spread by flame-fuel overlap. Fire spread models have usually assumed that radiation heat transfer is responsible for driving fire spread, but that assumption is a topic of continuing debate, and appears to contradict some experimental observations. A convection-based shrub-scale fire spread model has been developed, building on a heritage of experiments and modeling previously performed at Brigham Young University. This project has (1) characterized fundamental aspects of fire behavior, (2) integrated the resulting submodels of fire behavior into an existing shrub model framework, and (3) produced shrub-scale fire spread experiments and (4) made model comparisons. This research models fire spread as a convection-driven phenomenon and demonstrates strategies for overcoming some of the challenges associated with this novel approach.

[EN] The potential of diesel engines in terms of robustness, efficiency and energy density has made them widely used as power generators and propulsion systems. Specifically, fuel atomization, vaporization and air-fuel mixing, have a fundamental effect on the combustion process, and consequently, a direct impact on pollutant formation, fuel consumption and noise emission. Since the combustion chamber has a limited space respect to the spray penetration, wall impingement is considered to be a common event in direct injection diesel engines, having a relevant influence in the spray evolution and its interaction with both surrounding air and solid walls. This makes of spray-wall interaction an important factor for the combustion process that is still hardly understood. At cold-start conditions, the low in-chamber pressures and temperatures promote the deposition of fuel in the piston wall, which leads to a boost in the formation of unburned hydrocarbons. Additionally, modern design trends such as the increment of rail pressures in injection systems and the progressive reduction of the engine displacement, favor the emergence of spray collision onto the walls. In spite of the evident relevance of the comprehension of this phenomenon and the efforts of engine researchers to reach it, the transient nature of injection process, its small time scales and the complexity of the physical phenomena that take place in the vicinity of the wall, make challenging the direct observation of this spray-wall interaction. Even though computational tools have proven to be priceless in this field of study, the need for reliable experimental data for the development of those predictive models is present. This thesis is aimed to shed light on the fundamental characteristics of spray-wall interaction (SWI) at diesel-like chamber conditions. A flat wall was set at different impingement distances and angles respect to the spray. In this way, two different kinds of experimental investigations on colliding sprays were carried out: A transparent quartz wall was employed into the chamber to, in isolation, analyze the macroscopic characteristics of the spray at both evaporative inert and reactive conditions, which have been observed laterally and through the wall, thanks to the use of a high-pressure and high-temperature vessel with optical accesses. This same test rig was used in the second kind of experiments, where instead of the quartz plate, a stainless steel wall was used to capture the effect of the operating conditions on the heat flux between the wall and the spray during the injection-combustion events and to determine how spray and flame evolution are affected by realistic heat transfer situations. This wall was instrumented to control its initial in-chamber surface temperature and to measure its variation with time by using high-speed thermocouples. Tests at free-jet conditions were also performed in order to provide a solid comparative base for those experiments.
[ES] El potencial de los motores diesel en términos de robustez, eficiencia y la densidad de energía los ha hecho ser ampliamente usados como generadores de energía y sistemas propulsivos. Específicamente, la atomización de combustible, vaporización y mezcla de aire y combustible tienen un efecto fundamental en el proceso de combustión y, en consecuencia, un impacto directo en la formación de emisiones contaminantes, consumo de combustible y generación de ruido. Dado que la cámara de combustión tiene un espacio limitado con respecto la capacidad de penetración del chorro, el impacto de la pared se considera bastante común en motores de inyección directa diésel, que tienen una influencia relevante en la evolución del chorro y su interacción con el aire circundante y las paredes sólidas. Esto hace de interacción chorro-pared, un factor importante para el proceso de combustión que aún es dificilmente comprendido. En condiciones de arranque en frío, las bajas presiones y temperaturas en la cámara promueven la deposición de combustible en la pared del pistón, lo que conduce a un aumento en los niveles de formación de hidrocarburos no quemados. Además, las tendencias modernas de diseño como el incremento de las presiones de rail en los sistemas de inyección y la progresiva reducción en la cilindrada de los motores, favorecen la aparición de colisiones entre chorro y pared. A pesar de la evidente importancia en la comprensión de este fenómeno y los esfuerzos de los investigadores para alcanzarla, la transitoria naturaleza del proceso de inyección, sus pequeñas escalas de temporales y la complejidad de los fenómenos físicos que tienen lugar en las proximidades de la pared, hacen que la observación directa de esta interacción chorro-pared sea un desafío. Aunque las herramientas computacionales han demostrado ser invaluables en este campo de estudio, la necesidad de datos experimentales confiables para el desarrollo de esos modelos predictivos está muy presente. Esta tesis tiene como objetivo arrojar luz sobre las características fundamentales de la interacción chorro-pared (SWI por sus siglas en inglés) en condiciones de cámara similares a las de un motor diesel. Se colocó una pared plana a diferentes distancias de impacto y ángulos con respecto al jet. De esta manera, dos tipos diferentes de investigaciones experimentales sobre chorros en colisión se llevaron a cabo: se empleó una pared de cuarzo transparente en la cámara para, de forma aislada, analizar las características macroscópicas del chorro en condiciones evaporativas inertes y reactivas, que pueden observarse lateralmente y a través de la pared, gracias al uso de una instalación de alta presión y alta temperatura ópticamente accesible. Esta misma instalación se utilizó en el segundo tipo de experimentos en los que se introdujo una pared de acero inoxidable para capturar adicionalmente el efecto de las condiciones de operación en el flujo de calor entre ésta y el chorro durante los eventos de inyección y combustión y para determinar cómo la evolución del chorro y la llama son afectadas por una situación realista de transferencia de calor. Esta pared fue instrumentada para controlar la temperatura inicial de su superficie expuesta a la cámara y medir su variación con el tiempo, utilizando termopares de alta velocidad. Ensayos en condiciones de chorro libre también se realizaron para proporcionar una base comparativa sólida para esos experimentos.
[CA] El potencial dels motors dièsel en termes de robustesa, eficiència i la densitat d'energia els ha fet ser àmpliament usats com a generadors d'energia i sistemes propulsius. Específicament, l'atomització de combustible, vaporització i barreja d'aire i combustible tenen un efecte fonamental en el procés de combustió i, en conseqüència, un impacte directe en la formació d'emissions contaminants, consum de combustible i generació de soroll. Atès que la cambra de combustió té un espai limitat pel que fa la capacitat de penetració de l'raig, l'impacte de la paret es considera bastant comú en motors d'injecció directa dièsel, que tenen una influència rellevant en l'evolució del doll i la seva interacció amb el aire circumdant i les parets sòlides. Això fa d'interacció doll-paret, un factor important per al procés de combustió que encara és difícilment comprès. En condicions d'arrencada en fred, les baixes pressions i temperatures a la cambra promouen la deposició de combustible a la paret del pistó, el que condueix a un augment en els nivells de formació d'hidrocarburs no cremats. A més, les tendències modernes de disseny com l'increment de les pressions de rail en els sistemes d'injecció i la progressiva reducció en la cilindrada dels motors, afavoreixen l'aparició de col·lisions entre el doll i la paret. Tot i l'evident importància en la comprensió d'aquest fenomen i els esforços dels investigadors per aconseguir-la, la transitòria naturalesa de l'procés d'injecció, les seves petites escales de temporals i la complexitat dels fenòmens físics que tenen lloc en les proximitats de la paret , fan que l'observació directa d'aquesta interacció doll-paret siga un desafiament. Tot i que les eines computacionals han demostrat ser invaluables en aquest camp d'estudi, la necessitat de dades experimentals fiables per al desenvolupament d'aquests models predictius està molt present. Aquesta tesi té com a objectiu donar llum sobre les característiques fonamentals de la interacció doll-paret (SWI per les seues sigles en anglès) en condicions de cambra similars a les d'un motor dièsel. Es va col·locar una paret plana a diferents distàncies d'impacte i angles pel que fa al jet. D'aquesta manera, dos tipus diferents d'investigacions experimentals sobre dolls en col·lisió es van dur a terme: es va emprar una paret de quars transparent a la cambra per, de forma aïllada, analitzar les característiques macroscòpiques del doll en condicions evaporació inerts i reactives, que poden observar lateralment i a través de la paret, gràcies a l'ús d'una instal·lació d'alta pressió i alta temperatura òpticament accessible. Aquesta mateixa instal·lació es va utilitzar en el segon tipus d'experiments en els quals es va introduir una paret d'acer inoxidable per capturar addicionalment l'efecte de les condicions d'operació en el flux de calor entre aquesta i el dull durant els esdeveniments d'injecció i combustió i per determinar com l'evolució del doll i la flama són afectades per una situació realista de transferència de calor. Aquesta paret va ser instrumentada per controlar la temperatura inicial de la seua superfície exposada a la càmera i mesurar la seua variació amb el temps, utilitzant termoparells d'alta velocitat. Assajos en condicions de doll lliure també es van realitzar per proporcionar una base comparativa sòlida per a aquests experiments.
Peraza Ávila, JE. (2020). Experimental study of the diesel spray behavior during the jet-wall interaction at high pressure and high temperature conditions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149389
TESIS

La demande actuelle du marché du transport en matériaux composites à matrice polymère est en augmentation importante afin de remplacer les pièces aujourd’hui fabriquées en alliages métalliques par des matériaux plus légers et performants. Actuellement couramment utilisés, les composites thermodurcissables présentent l’inconvénient de ne pas être recyclables. Aussi, un des objectifs du projet « Résines idéales » durant lequel cette thèse a été réalisée est de mettre au point de nouveaux composites à matrice thermoplastique, doués de propriétés équivalentes. Parmi celles-ci, le comportement au feu est un enjeu essentiel pour leur développement et l’objectif de cette thèse est de développer de nouveaux systèmes retardateurs de flamme pour des matériaux composites thermoplastiques à fibres continues. Dans un premier temps, un screening des retardateurs de flamme phosphorés potentiellement efficaces a été effectué. L’étude de l’influence du renfort taffetas sur la stabilité thermique et le comportement au feu a également été réalisée (cône calorimètre, IOL, UL94). Ensuite, afin d’améliorer le comportement au feu, et en particulier, de satisfaire aux normes feu aéronautiques (les plus exigeantes), nous avons étudié des mélanges binaires et ternaires de retardateurs de flamme constitués du RF phosphoré sélectionné et d’autres charges : alumine, hydroxyde d’aluminium (ATH), graphite expansé, et 9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide (DOPO). Dans chaque cas, la stabilité thermique et le comportement au feu ont été caractérisés et discutés
The present demand of polymer-matrix composite materials in the transport market is significantly increasing, to replace the work-pieces actually manufactured in metal alloys, the polymer-matrix composite being lighter and more performant. Thermoset composites are currently and widely used however this kind of composites presents a severe drawback due to their non- recyclable character. One of the objectives of the “Résines idéales” project and of this thesis is to develop new composites made from thermoplastic matrix, endowed with similar properties. Among them, the fire behavior is a major challenge and the aim of this work is to develop new flame retardant systems for thermoplastics composites reinforced with continuous fibers. Firstly, we have performed a screening of potentially effective phosphorus flame retardants. Also, we have studied the influence of the reinforcement taffetas on the thermal stability and fire behavior. For that, various tests have been performed such as cone calorimeter, LOI and UL-94. Then, to improve the fire behavior and particularly to satisfy the aeronautical fire standards (the most challenging), we have studied binary and ternary mixtures of flame retardants constituted by the selected phosphorus flame retardant and other additives: alumina, aluminum hydroxide (ATH), expanded graphite and 9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide (DOPO). In each case, the thermal stability and fire behavior have been characterized and discussed

A detailed theoretical and numerical investigation of the behaviour of reactive systems under the influence of chaotic stirring is presented. These systems exhibit stationary solutions arising from the balance between chaotic advection and diffusion. Excessive stirring of such systems results in the termination of the reaction via a saddle-node bifurcation. The solution behaviour of these systems is analytically described using a recently developed nonperturbative, non-asymptotic variational method. This method involves fitting appropriate parameterised test functions to the solution, and also allows us to describe the bifurcations of these systems. This method is tested against numerical results obtained using a reduced one-dimensional reaction-advection-diffusion model. Four one- and two-component reactive systems with multiple homogeneous steady-states are analysed, namely autocatalytic, bistable, excitable and combustion systems. In addition to the generic stirring-induced saddle-node bifurcation, a rich and complex bifurcation scenario is observed in the excitable system. This includes a previously unreported region of bistability characterised by a hysteresis loop, a supercritical Hopf bifurcation and a saddle-node bifurcation arising from propagation failure. Results obtained with the nonperturbative method provide a good description of the bifurcations and solution behaviour in the various regimes of these chaotically stirred reaction-diffusion systems.

Doctor of Philosophy
A detailed theoretical and numerical investigation of the behaviour of reactive systems under the influence of chaotic stirring is presented. These systems exhibit stationary solutions arising from the balance between chaotic advection and diffusion. Excessive stirring of such systems results in the termination of the reaction via a saddle-node bifurcation. The solution behaviour of these systems is analytically described using a recently developed nonperturbative, non-asymptotic variational method. This method involves fitting appropriate parameterised test functions to the solution, and also allows us to describe the bifurcations of these systems. This method is tested against numerical results obtained using a reduced one-dimensional reaction-advection-diffusion model. Four one- and two-component reactive systems with multiple homogeneous steady-states are analysed, namely autocatalytic, bistable, excitable and combustion systems. In addition to the generic stirring-induced saddle-node bifurcation, a rich and complex bifurcation scenario is observed in the excitable system. This includes a previously unreported region of bistability characterised by a hysteresis loop, a supercritical Hopf bifurcation and a saddle-node bifurcation arising from propagation failure. Results obtained with the nonperturbative method provide a good description of the bifurcations and solution behaviour in the various regimes of these chaotically stirred reaction-diffusion systems.

A swirl stabilised dump combustor capable of imposing flow perturbations creating combustion instabilities has been designed and commissioned. The capability of supplying different fuel mixtures (methane hydrogen blends) has been incorporated. Additional capability is the facility to preheat the combustion air prior to chamber entry and to be able to introduce dilution air into the chamber. The chamber itself is of fused silica quartz to allow non-intrusive optical diagnostics. High speed CH* Chemiluminescence has been performed to qualitative characterise the unstable heat release rate of pure methane and methane hydrogen blended flames to allow analysis of the mean deconvoluted flame structure. High speed Stereoscopic Particle Imaging Velocimetry (SPIV) has been used to acquire the flow field throughout the chamber and focusing upon the Annulus entry. These diagnostics have been phase locked to the imposed perturbation. A selection of conditions is presented with three different perturbation frequencies within the low frequency range. These reveal vastly different reacting and flow field structures. The difference of structures is attributed to behaviour of the IRZ (Internal Recirculation Zone) and CRZ (Corner Recirculation Zone) in altering the flame shape. All conditions exhibited the axisymmetric/bubble vortex breakdown mechanism responsible for stabilisation. Both single cell and double cell structures were observed in the mean flow field vector maps. The mechanism of oscillating heat release rate is attributed to oscillations of flame surface area. Profiles of integrated heat release rate and flame exhibit the same profile shape and behaviour correlating very well. The inclusion of hydrogen had no quantifiable impact upon the mean reacting or flow field structures using the current diagnostics. Investigation into the nature of the turbulence of the shear layers close to the annulus is presented for three perturbation frequencies. This highlighted periodic structures within the turbulence corresponding to the imposed perturbation frequency. It was found that excitation of both shear layers for all turbulent components was not always true and depended upon the perturbation frequency and flow structure close to the annulus. Two oppositely rotating vorticity structures were revealed attached to the outer and inner circumference of the annulus. These structures protruded into the chamber and spread radially. Frequency analysis of these two structures revealed both were oscillating at the perturbation frequency indicating vorticity shedding. The mean vorticity structures are shown to be influenced also by the behaviour of the recirculation zones.

The environmental occurrence and behaviour of the brominated flame retardant (BFR) decabromodiphenyl ethane (dbdpe) has only been studied to a limited extent. It is structurally similar to decabromodiphenyl ether (decaBDE), which makes it conceivable that dbdpe may also become an environmental contaminant of concern. A method for environmental analysis and comparative assessments of dbdpe and decaBDE was developed. Both BFRs were studied in: a mass balance of the Henriksdal WWTP in Stockholm (Paper I); an international survey of sewage sludge (Paper II); sediment along a transect from Henriksdal WWTP to the outer archipelago of Stockholm and from isolated Swedish lakes (Paper III); and a benthic food web from the Scheldt estuary (Paper IV). Dbdpe was found in sludge from every country surveyed, indicating that it may be a worldwide concern. The WWTP mass balance showed that virtually all of the BFRs were transferred from wastewater to sludge. A small fraction was emitted via the effluent, confirming emissions to the aquatic environment. In the marine sediment, the BFR levels close to the WWTP outfall were high. They decreased along the transect to low levels in the outer archipelago. The study of lake sediment showed a widespread presence of dbdpe in the Swedish environment and provided evidence that it originates from long range atmospheric transport. In the food web, dbdpe did bioaccumulate to a small extent which was similar to decaBDE. The transfer of the BFRs from sediment to benthic invertebrates was low, while transfer from prey to predator was higher. Biodilution was observed rather than biomagnification. This work suggests that the persistence, the susceptibility to long range atmospheric transport, and the potential for bioaccumulation are similar for dbdpe and the regulated decaBDE that it is replacing. Thus, there is a risk that a problematic environmental pollutant is being replaced with a chemical that is equally problematic.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.

This thesis describes studies of the relationship between the molecular structure of a range of organophosphorus-based polymer additives and their ability to confer intumescent flame retardant properties on the resulting polymers. The development of intumescent fire retardants is discussed along with the principles of flame retardancy in general. Much of the work centred around the chemistry of a key starting material, pentaerythritol phosphate (PEPA). This compound was found to be less reactive than expected, due to a combination of its neopentyl type structure and the electron withdrawing effect of the phosphoric ester functionality. Various derivatives of PEPA were synthesised, most containing reactive functional groups which facilitated future development of the compound. The derivatives containing no reactive groups were investigated for their intumescent behaviour in their own right. Derivatives of PEPA containing an acidic functionality were utilised in the production of intumescent salt systems using cations with a high nitrogen content in the form of s-triazines. The most promising was the trimethylolmelamine salt of a bis-PEPA derivative of phosphoric acid, which, on testing, proved to be more effective than the current "state of the art" intumescent additive. Metal salts of acidic PEPA-derivatives were also investigated. Derivatives of PEPA containing a carbon-carbon double bond were investigated for their potential to polymerise and thus form more stable additives. Only one such polymer was successfully synthesised, that being poly (PEPA methacrylate). Despite being non-intumescent, due to its high thermal stability this polymer has potential as a flame retardant additive. The monomer was found to copolymerise with methyl methacrylate to form a polymer of high thermal stability. When investigating the relationship between the molecular structure of the compounds developed and their intumescent behaviour, it was observed that only compounds containing an ionisable hydrogen atom exhibited intumescent decomposition on pyrolysis.

Cette thèse consiste à mettre en place un couplage externe aéro-thermo-mécanique, sur la base d'un schéma partitionné, entre les codes de recherche CEDRE (mécanique des fluides, volumes finis) et Z-set (modules indépendants pour la mécanique des structures et la thermique du solide, éléments finis). Les résultats numériques sont confrontés à ceux de l'expérience (une campagne de mesures a été menée dans le cadre de cette étude), dans le cas d'un problème complexe lié au domaine de l'aérospatial : l'interaction flamme-paroi. Ce phénomène est piloté par la thermique, à travers le flux de chaleur pariétal généré par la flamme. A cause de la disparité des temps caractéristiques thermiques entre les milieux fluide et solide, la partie aéro-thermique du couplage est traitée de façon simplifiée, en considérant le fluide comme une suite d'états stationnaires. L'échauffement de la plaque métallique provoque sa déformation (la loi de comportement mécanique du matériau est de type élasto-visco-plastique). Le déplacement de l'interface fluide-structure est propagé sur le maillage fluide. En se basant sur les similitudes entre jets non réactifs et réactifs (de type flamme) dans le cas de l'impact, des calculs couplés sont menés dans des configurations 2D et 3D de l'impact d'un jet chaud non réactif.

Une prise de conscience commune des facteurs environnementaux et plus particulièrement du réchauffement climatique rend urgent un meilleur contrôle de la consommation d'énergie. Une solution consiste à réduire les pertes d'énergie dans les bâtiments en utilisant de nouveaux matériaux d'isolation thermique efficaces tels que les mousses polyuréthanes. Ces mousses sont des matériaux très performants et compétitifs au regard des autres solutions existantes. Cependant, elles sont extrêmement inflammables en raison de leur nature organique. Les chercheurs et industrielles ajoutent alors des molécules appelées retardateurs de flamme (RFs) dans leur composition afin d’éviter le départ d’un incendie ou encore de diminuer l’intensité de la combustion lorsqu’un feu se déclare. C’est dans ce cadre que s’inscrit cette thèse dont l’objectif est d’étudier de manière systématique des mousses polyuréthanes (PUR) et polyisocyanurates (PIR). Le but est de proposer une démarche scientifique permettant un développement plus rapide et plus efficace de nouvelles formulations. Cette étude systématique a également été couplée à une étude multi-échelle du comportement au feu des mousses puisqu’un test à l’échelle du laboratoire a été développé: « le mini-SBI ». Les RFs étudiés dans ces travaux sont les RFs organiques phosphorés qui sont actuellement mis en avant afin de remplacer certains RFs halogénés qui pourraient être dangereux pour l’environnement et la santé. Les mécanismes de décomposition des mousses vierges et ignifugées ont été élucidés. Ainsi, dans le cas des RFs phosphorés, nous avons pu démontrer que leur mode d’action variait en fonction du degré d’oxydation du phosphore ainsi qu’en fonction de leur point de décomposition. De plus, l’efficacité des RFs varie également en fonction de la mousse utilisée (PUR ou PIR). Ces résultats pourront être mis à profit dans le développement de nouvelles formulations
A common awareness of environmental factors and more particularly of global warming makes it urgent to better control energy consumption. One solution is to reduce energy loss in building using new and efficient thermal insulation materials such as polymeric foams. Polyurethane (PUR) and polyisocyanurate (PIR) foams are very effective and competitive materials due to their low cost. However, these materials are extremely flammable due to their organic nature. Researchers and manufacturers add molecules called flame retardants (FRs) to their composition in order to prevent the outbreak of a fire or reduce the intensity of combustion when a fire breaks out. The objective of this PhD work is to study by systematic approaches the fire behavior of PUR and PIR foams. The aim is to propose a scientific approach allowing a quicker and more efficient development of new formulations. This systematic study was also coupled with a multi-scale study of the fire behavior of the foams, as a laboratory-scale fire test was developed (M-SBI), which allowed a quick and efficient examination of the formulations. The FRs studied in this work are phosphorus organic FRs which are currently promoted to replace some halogenated FRs which could be dangerous for the environment and health. The mechanisms of degradation of virgin and flame retarded foams were elucidated using various analytical tools. Thus, in the case of phosphorus FRs, we were able to demonstrate that their mode of action varied according to the phosphorus oxidation degree as well as according to their point of decomposition. Moreover, the efficiency of the FRs also varies according to the foam used (PUR or PIR). All these results can thus advantageously be exploited to propose future efficient flame retardants for specific systems to reduce the combustion intensity of the foams

This thesis is concerned with the swirl stabilised combustion of gases with variable composition, primarily those derived from the gasification of carbonaceous material, and secondarily those that occur naturally, such as shale gas. During the course of this research the temporal composition of producer gas, derived from the gasification of biomass, was studied in order to ascertain the effect its variable fuel composition had on its combustion properties. Its variation was highly dependent on gasifier operation, and despite the stoichiometric air-to-fuel ratio and Wobbe Index of the fuel being consistent, high throat temperatures resulted in high hydrogen content and laminar flame speeds. Alterations in flame speed are linked to thermo-acoustic instabilities, flame extinction and damaging flame propagation. Acoustic response under combustion conditions was investigated, to determine how it altered over a flames stability range. Indicators of impending flame flashback and blowoff were found, which could be utilised to prevent such events from occurring in an appropriate control system, without the need for real time gas analysis. Flames with high hydrogen content display a propensity for flashback, especially in high turbulence burners, such as those found in gas turbines, where thermo-acoustics are also a significant problem. Variation in fuel composition, particularly in the proportion on hydrogen, exacerbates these problems. The diffusive injection effects of three gases on reacting flow structures were investigated as a method of improving the stability of pre-mixed flames. Carbon dioxide was found to improve flame stability, whilst reducing emissions during the combustion of syngas mixtures in a development gas turbine combustor. Monitoring acoustic response and diffusive injection are thus suggested as additional stabilisation methods for the combustion of gases with variable composition.

La câblerie est un secteur industriel gros consommateur de polymères. Dans ce domaine, les normes imposent cependant de limiter le risque incendie et donc d'ignifuger les matériaux polymères utilisés, sources importantes de combustibles. De nombreux travaux ont porté sur leur ignifugation par utilisation d'additifs retardateurs de flammes, mais peu d'entre eux ont étudié l'influence de la morphologie des mélanges polymères chargés sur la stabilité thermique et le comportement au feu. Cette thèse fait suite à un précédent projet qui avait démontré une influence significative de la morphologie sur le comportement au feu d'un mélange polymère binaire (PC/PBT). Elle a pour but d'améliorer la compréhension de cette influence dans le cas de formulations plus complexes (ternaires ou quaternaires) à matrice éthylène méthylacrylate (EMA). Pour cela, la première stratégie adoptée a été l'identification d'un système ignifugeant comprenant un polyester capable de charbonner lors de l'ajout d'un RF. Une fois ce système identifié (PBT+MDH), il a été incorporé en matrice EMA en faisant varier la composition et la morphologie (dispersion sélective, taille des particules…). Cette approche a mis en évidence des différences significatives entre les différentes formulations et des résultats très intéressants ont été obtenus en termes de réaction au feu à l'échelle laboratoire. Cependant, le passage à l'échelle pilote (test de propagation de flamme) n'a pas permis de valider ces formulations pour des applications câbles. Au vu de ces constatations, une dernière partie a été proposée pour essayer d'améliorer la cohésion du résidu par ajout de polyphosphate d'ammonium
The cable industry is a major consumer of industrial polymers. In this area, the standards impose to limit the fire risk and thus to enhance the fireproof of the polymeric materials which are important sources of fuel. Many studies have focused on their flame retardancy by using additive flame retardants, but few of them have studied the influence of the morphology of filled polymer blends on the thermal stability and the fire behavior. This thesis follows a previous project which demonstrated a significant influence of the morphology on the fire behavior of a binary polymer blend (PC / PBT). It aims to improve the understanding of this influence in the case of more complex formulations (ternary or quaternary) with ethylene methylacrylate (EMA) matrix. The first strategy was the identification of a flame retardant system including polyester that is able to char when a flame retardant is added. Once the system is identified (PBT + MDH), it was incorporated in EMA matrix by varying the composition and the morphology (selective dispersion, particle size ...). This approach showed significant differences between the different formulations and very interesting results have been obtained in terms of fire reaction at the laboratory scale. However, the scale-up approach (flame spread test) did not validate these formulations for cables applications. Therefore, the last part has been proposed to try to improve the cohesion of the residue by adding ammonium polyphosphate

Ce travail porte sur la stabilisation, la structure et le comportement thermique d’oxy-flammes turbulentes opérées avec du méthane comme combustible. L’étude recouvre des flammes fonctionnant dans des conditions prémélangées et non prémélangées, avec et sans swirl, et avec un oxydant dont la concentration d'oxygène est variable. Plus de 3000 flammes sont étudiées sous une large gamme de conditions de fonctionnement grâce à une chambre de combustion polyvalente, et à des diagnostics laser et des outils de calcul haute-fidélité. L'objectif de cette thèse est de répondre à la question suivante. Si un changement de composition du combustible ou de l'oxydant, de la puissance thermique ou une légère modification de l'injecteur est effectué, est-il possible d’ajuster le swirl conféré aux réactifs afin de retrouver la même structure de flamme et le même régime de stabilisation ? L'impact de l’angle d’ouverture d’un divergent placé en sortie d’injecteur sur l’écoulement est étudié sous un angle à la fois théorique et expérimental au moyen de diagnostics optiques. Un modèle est développé pour prédire la position de la zone de recirculation centrale lorsque cet angle varie. Les effets d'une modification de la composition de l'oxydant sur la structure de flamme sont ensuite étudiés lorsque la flamme passe d'une dilution en N2 à une dilution en CO2. Il est démontré que le swirl a un impact considérable sur la structure de la flamme. La température et la distribution du transfert thermique sont ensuite caractérisées expérimentalement le long des parois latérales de la chambre de combustion. Un modèle de premier ordre est développé pour expliquer les changements de transferts thermiques observés entre les flammes diluées en N2 et en CO2. Le comportement thermique de la chambre de combustion Oxytec est ensuite étudié à l’aide de la simulation numérique aux grandes échelles couplée à un solveur de rayonnement Monte Carlo. La prise en compte détaillée du rayonnement thermique modifie faiblement la position de la flamme et la structure de l’écoulement, mais a un impact considérable sur la température des gaz brûlés et sur la distribution du flux thermique à l'intérieur de la chambre de combustion. Un modèle permettant de prédire la température moyenne du gaz et la distribution du transfert thermique des parois lors du passage d'une simulation non couplée à une simulation couplée est finalement proposé.La suite de l’étude est consacrée à la caractérisation expérimentale des effets du swirl sur la structure et les modes de stabilisation des oxy-flammes en condition non prémélangées et opérées avec un injecteur coaxial dans lequel les deux jets peuvent être swirlés. Une analyse paramétrique est menée en couvrant une large gamme de rapports de flux de moments axiaux et de fractions massiques d'O2, et aboutit sur un modèle qui prédit la longueur d’oxy-flammes coaxiales avec et sans swirl. Il est ensuite montré qu’une augmentation du swirl interne peut détacher la flamme des lèvres de l’injecteur. L'origine des différentes structures de flamme et d'écoulement qui en résultent est étudiée plus en détail à l'aide de mesures couplées OH-PLIF / PIV. Il apparaît que le phénomène de détachement de la flamme hors de l’injecteur central est provoqué par un blocage partiel du jet de méthane central lorsque le swirl interne augmente. De plus, la température mesurée à la surface de l’injecteur lorsque la flamme est détachée est considérablement plus faible que lorsque la flamme est accrochée. Enfin, la structure des oxy-flammes coaxiales non prémélangées est étudiée lorsque les swirls centraux et annulaires sont injectés de manière co- et contra-rotatives. Il est prouvé qu’un swirl contra-rotatif diminue la recirculation du gaz tandis qu’un swirl co-rotatif l'améliore. Cette analyse aboutit à un modèle prédisant l’évolution de la position du pied d’une flamme lorsqu’elle est décrochée de l’injecteur
The thesis deals with the stabilization, structure, and thermal behavior of turbulent oxy-flames burning methane. It covers flames operated in premixed and non-premixed conditions, with and without swirl conferred to the flow, and with a variable concentration of oxygen in the oxidizer stream. These flames are investigated over a broad range of operating conditions on a versatile lab-scale combustor with laser diagnostics and high-fidelity computational tools. The objective is to answer the following question. If a change of fuel or oxidizer composition, thermal power, or a slight modification of the injector nozzle is made, can the swirl motion conferred to the reactants be adjusted to retrieve the same flame structure and stabilization regime before the modification? The work relies both on parametrical analysis conducted on a large set of 3000 operating conditions and a thorough investigation of selected flames. Swirled premixed flames are investigated first. The impact on the flow pattern of a diverging cup at the nozzle outlet is investigated both theoretically and experimentally with optical diagnostics. Expressions for the evolution of the swirl level through this diffuser are derived. A model is then developed to predict the position of the central recirculation zone as the quarl angle varies. The study proceeds by assessing effects of a change in the oxidizer composition when switching from N2- to CO2-dilution on the structure of swirled flames. It is found that the swirl has a considerable impact on the flame structure, and two flame wrinkling processes are identified depending on the swirl level. An experimental characterization of the temperature and heat flux distribution along the combustor sidewalls is then conducted. A low-order model is derived to explain changes of the heat flux distributions for the N2- and CO2-diluted flames. The thermal behavior of the Oxytec combustor is then investigated with large-eddy simulations coupled with a Monte Carlo radiative heat transfer solver. It is found that a detailed description of the thermal radiation barely alters the flame and flow position, but has a tremendous impact on the burned gas temperature and the heat flux distribution inside the combustor. A model which enables to predict the global gas temperature and wall heat flux distribution when switching from a non-coupled simulation to a coupled-simulation is finally proposed.An experimental characterization of the effects of swirl on the structure and stabilization modes of non-premixed oxygen-enriched flames above a coaxial injector in which the two streams are eventually swirled is carried out. A model is derived to predict the length of coaxial oxy-flames with and without swirl. It is found that increasing the inner swirl level detaches the flame from the nozzle rim and lowers the flame liftoff distance. Varying the quarl opening angle or the oxygen concentration in the annular oxidizer stream also enables to control the flame liftoff height. The origin of the different flame and flow patterns is further investigated with the help of coupled OH-PLIF/PIV experiments. It is shown that flame detachment from the internal nozzle is caused by a partial blockage of the inner fuel stream by an intense central recirculation zone when the inner swirl increases. The temperature measured at the nozzle rim of the injector is in this case drastically reduced compared to attached flames. The structure of non-premixed co-axial oxy-flames is finally investigated for co- and counter-rotating operations. It is found that counter-swirl cancels gas recirculation along the burner axis while co-swirl enhances it. This allows to separate effects occurring at the outlet of the injector from swirl dissipation taking place further downstream after the coaxial jets have merged. This analysis has resulted in a model for the evolution of the flame root position and validated for about 200 lifted flames

II Brominated flame retardants (BFRs) are persistent organic pollutants that have reached a global distribution in the environment. Many of the BFRs are lipophilic and bioaccumulative, and consequently several of them have been found in wildlife tissue with some of the highest levels recorded in several raptor species. The overall aim of this study was to determine the effects of exposure to environmentally relevant levels of the two most prominent BFRs, polybrominated diphenyl ethers (PBDEs: DE-71 mixture) or hexabromocyclododecane (HBCD) on the reproductive success, behaviour and physiology of captive American kestrels. In 2007, males exposed in ovo to DE-71 at three mean egg exposure concentrations of 289 ng/g ww for the low-exposure males, 1131 ng/g ww for the high-exposure males, or background levels of 3 ng/g ww for controls, were paired with unexposed females, and euthanized in the following year for testes extraction. In 2008, kestrel pairs were exposed via diet to technical HBCD (0.32 µg/µl wet weight (ww) daily) or the vehicle only for controls; testis mass and histology was examined in an additional group of males exposed to the same concentrations for three weeks. Pairs with males exposed in ovo to DE-71 demonstrated decreased clutch size, and egg mass, reduced fertility, and delayed timing of egg-laying when compared to controls. Both members of these pairs displayed reduced courtship behavior, including copulation frequency, and males demonstrated reduced parental behavior compared to controls. The testes of males exposed in ovo to DE-71 were enlarged and contained more seminiferous tubules with lumen, though the number of tubules containing final spermatids decreased with increasing in ovo exposure to some PBDE congeners. Additionally, testosterone levels were reduced during breeding in these males. Pairs exposed to HBCD via diet laid their clutches earlier and their average clutch size of eggs was larger, however no associated increase in reproductive success was noted. Though eggshell thickness was unaffected, HBCD-exposed females produced lighter and smaller eggs. Both members of HBCD-exposed pairs showed reduced courtship behavior and males additionally demonstrated reduced parental care. Males exposed to HBCD had elevated testosterone levels, reduced circulating thyroxin (T4) and increased body mass at certain time-points throughout the breeding season. Unpaired males had larger testes than controls with more seminiferous tubules containing final spermatids. The results presented herein demonstrate that both of these BFRs affect reproduction in American kestrels. Since exposure levels in the present study were environmentally relevant, wild birds receiving similar exposure may experience comparable effects.
IV Les ignifugeants bromés sont des polluants organiques tenaces, répandus globalement dans l'environnement. Lipophiles et bioaccumulatifs, on les retrouve dans les tissus animaux, dont ceux des rapaces qui possèdent parmi les concentrations les plus élevées. Cette étude avait comme objectif global de déterminer les effets sur la reproduction, le comportement et la physiologie de crécerelles d'Amérique (Falco sparverius) captives exposées à deux ignifugeants brominés d'importance, soit les polybromodiphényléther (PBDE : mélange DE-71) et l'hexabromocyclodécane (HBCD), à des concentrations représentatives des niveaux environnementaux. En 2007, trois groupes de mâles exposés in ovo à des concentrations moyennes (± l'erreur-type) de DE- 71 respectives de 288,60 ± 33,35 ng/g mh (faible exposition), de 1130,59 ± 95,34 ng/g mh (forte exposition) et de 3,01 ± 0,46 ng/g mh (contrôle), ont été accouplés avec des femelles non-exposées, et euthanasiés l'année suivante pour en extraire les testicules. En 2008, des couples furent exposés au HBCD dans leur alimentation quotidienne, soit à une concentration de 0.544 µg/µl mh ou à un niveau-contrôle. De plus, la masse et l'histologie testiculaires de mâles non-accouplés exposés pendant trois semaines à ces mêmes concentrations respectives furent analysées. Comparés aux couples-contrôle, les couples avec mâles exposés au DE-71 ont subi une réduction dans la grandeur de leurs couvées et dans la masse et la fertilité de leurs œufs, ainsi qu'un délai dans leur ponte. Chacun des membres de ces couples démontra une diminution des comportements nuptiaux, dont la fréquence de copulation, et les mâles ont fait preuve de soins parentaux réduits. Ces derniers avaient également des testicules hypertrophiés contenant un plus grand nombre de tubules séminifères pourvus de lumen, cependant le nombre de tubules contenant des spermatides finales décrut en fonction de la croissance du niveau d'exposition à certains congénères PBDE. De leur part, les couples exposés au HBCD ont connu des pontes précoces comportant un plus grand nombre moyen d'œufs que les couples-contrôle, par contre leur succès reproductif global demeura inchangé. Bien que l'épaisseur des coquilles ne fut pas affectée, leurs œufs étaient anormalement petits et légers. Encore une fois, chacun des membres de ces couples démontra une baisse dans les comportements nuptiaux et l'apport de soins parentaux fut réduit chez les mâles. Ces derniers présentèrent également à certains moments des niveaux de testostérone et des masses corporelles supérieurs ainsi que des niveaux de thyroxine (T4) inférieurs aux mâles-contrôle, et les mâles non-accouplés développèrent de plus gros testicules avec plus grand nombre de tubules séminifères contenant des spermatides finales. L'ensemble de ces résultats démontre que les deux ignifugeants bromés en question, à leurs niveaux environnementaux, agissent effectivement sur la reproduction chez les crécerelles d'Amérique. Il est donc admissible de supposer que les crécerelles à l'état sauvage, voire même autres oiseaux, éprouvent des impacts comparables.

Le comportement au feu de matériaux polymères peut changer plus ou moins fortement après vieillissement, mettant en péril les biens et les personnes en cas d’incendie. Ces changements dépendent du système considéré (nature du système retardateur de flamme, de la matrice polymère) et des conditions de vieillissement. Or jusqu’à aujourd’hui, les normes exigent l’évaluation de la réaction au feu d’un matériau juste après fabrication et rarement après un vieillissement représentatif des conditions réelles d’utilisation. L’évolution des caractéristiques des polymères ignifugés au cours du temps est actuellement peu connue, et seules quelques études ont eu lieu à ce sujet. Le travail de cette thèse concerne donc l’impact du vieillissement sur les performances au feu de systèmes complexes de polymères ignifugés. L’étude est basée sur les polymères polyméthacrylate de méthyle (PMMA) et acide polylactique (PLA) ; le système retardateur de flamme est quant à lui constitué de charges phosphorées et de silicates nanométriques. Un protocole de vieillissement et une méthodologie d’étude ont ensuite été mis en place pour déterminer l’influence du vieillissement sur les propriétés de ces matériaux : morphologie, masse molaire des polymères, dégradation des retardateurs de flamme, comportement au feu. Enfin, les caractéristiques des produits émis en phase gaz au cours de la combustion d’échantillons vieillis et non vieillis ont été analysées
The fire behaviour of polymeric materials can be modified after ageing, possibly leading to severe damages. These modifications depend on the chemical nature of the system (polymeric matrix, flame retardant system) and on the ageing conditions. Currently, norms exist, that define fire properties of fresh flame-retarded materials; but only few studies have been performed on aged materials. The aim of this work consists in evaluating the impact of ageing of flame-retarded materials. Firstly, materials have been processed from various formulations. The study focused on poly(methyl methacrylate) (PMMA) and poly(lactic acid) (PLA) polymers; flame-retardant system combining a phosphorus compound and mineral nanoparticles was added. Then an operating procedure has been created to simulate ageing, and a methodology has been developed to assess the characteristics of the composites before and after ageing (viscosity, morphology, fire behaviour). Finally, the combustion aerosols emitted by unaged and aged formulations have been investigated

Les polyesters insaturés sont des résines thermodurcissables particulièrement appréciées pour leur facilité de mise en œuvre et leur coût modéré. Cependant, comme tous les polymères organiques ils ont une réaction au feu médiocre, ce qui est critique dans un certains nombres de d'applications. L'objectif de cette thèse était d'élaborer de nouvelles formulations de résines ayant un comportement au feu amélioré. La première stratégie développée a été le greffage de monomères phosponés dans la matrice polyester. Des monomères méthacryliques et styrénique ont été synthétisés et utilisés pour remplacer une partie du styrène dans la résine. La stabilité thermique des résines modifiées est diminuée, mais leur comportement au feu est globalement meilleur. Des effets du phosphore en phase gazeuse et en phase condensée ont pu être mis en évidence.Dans une seconde partie, une sélection de particules se distinguant par leur nature, leur taille et leur facteur de forme a été testée. Si l'impact des ces charges est assez limité lorsqu'elles sont utilisées individuellement, des tests calorimétriques ont révélé que certaines combinaisons de particules pouvaient améliorer significativement la réaction au feu des résines. Enfin, des associations d'additifs phosphorés et de particules submicroniques ont été investiguées. Le polyphosphate d'ammonium se distingue des autres additifs par un impact très important sur le comportement au feu et particulièrement par le charbonnement important qu'il engendre, cependant sa combinaison avec des charges inorganiques ne s'est pas révélée probante
Unsaturated polyesters are thermoset resins particularly appreciated for their low cost and easy processing. Nevertheless one of their main drawbacks is their poor fire resistance. The aim of this PhD thesis was to prepare new resin formulations with an improved fire behaviour. The first part of this work was dedicated to the grafting of phosphorous monomers in the polyester matrix. Methacrylic and styrenic monomers were synthesized and used to replace of part of the styrene in the resin. Resin thermal stability was decreased, but on the whole their fire behaviour was improved. Condensed phase and gas phase effects of phosphorus were highlighted.In a second part, a screening of various kinds of particles with different sizes was performed. Calorimetric tests revealed that, while the effect of these particles used alone is limited, a decrease of resin flammability could be achieved with specific combinations. Finally, commercial phosphorous additives were associated with submicronic fillers. From all the additives tested, ammonium polyphosphate stands out, with a powerful impact on the resin fire reaction and especially a much increased charring. However, its combination with inorganic particles was not conclusive

L’utilisation des matériaux composites à matrice polymère dans l’industrie aéronautique offre de nombreux avantages en termes de gain de masse et de résistance à la fatigue ou à la corrosion. Cependant l’utilisation de nouveaux matériaux tels que les composites à matrice thermodurcissable nécessite des efforts conséquents de développement, de test et de vérification. En particulier dans le domaine de la résistance aux incendies. Ce travail porte sur la caractérisation expérimentale de la résistance au feu pour différents types de matériaux composites au moyen d’un brûleur. La première partie de l’étude traite en particulier de la caractérisation du flux thermique lors de l’agression par la flamme. Dans un second temps, la réponse à cette agression thermique est mesurée pour différents matériaux composites. Pour les deux volets de cette étude, les résultats expérimentaux sont confrontés aux résultats issus de simulations numériques avec OpenFoam
Carbone fibers reinforced polymers offer many advantages in terms of weight, fatigue resistance or corrosion in the aerospace industry. However, the use of new materials such as thermosetting matrix composites requires a significant effort of development, testing and validation. In particular in the field of fire resistance. This work focuses on the experimental characterization of fire resistance for different types of composite materials using a flame burner. The first part of the study deals with the characterization of the heat flux during the flame impingement. In a second step, the response to this thermal stress is measured for different composite materials. For both parts of this study, the experimental results are compared to the results obtained from numerical simulations with OpenFoam

Doutoramento em Restauro e Gestão Fluviais (FLUVIO) - Instituto Superior de Agronomia / Faculdade de Arquitetura / Instituto Superior Técnico
Flow regime regulates the ecological integrity of river ecosystems, shaping the structure and function of fish communities. The discharge fluctuations in hydropower plants in response to peak electricity demand (i.e. hydropeaking) result in rapid flow changes in tailwaters. The continued hydropower operations produced morphological, hydraulic and water quality alterations, affecting downstream fish. Fish responses to hydropeaking range from organism to life-cycle event changes. It is challenging to establish a cause-effect relationship between flow variability and a fish response, and to propose adequate mitigation measures. In the first part of this research, a literature review was conducted to find evidence for that relationship. The review showed that flow variability can represent a stressor for fish. However, it remained unclear if the responses were maladaptive. In the second part, the effects of hydropeaking and refuges were assessed for L. bocagei in an indoor flume. A multidisciplinary approach was adopted, where fish responses were combined with a hydraulic characterization. Peak events were tested by manipulating magnitude, peak frequency and duration. The refuges were lateral (meandering and one-sided deflectors) and instream (triangular pyramids and v-shaped) structures, tested along three experimental campaigns. Glucose and lactate (secondary responses), and movement behaviour (whole-animal responses) were assessed. The flow field and fluid-body interactions were characterized by using acoustic Doppler velocimetry and an artificial lateral line probe respectively. The movement patterns of L. bocagei were diverse and not always proportional to the severity of the flow event. Lateral deflectors and v-shaped structures provided low velocity areas. However, the created flow complexity represented an additional constraint for fish, reducing their ability to find them. Flow thresholds that represented the resting state of L. bocagei were identified, and specific movement patterns were related with hydrodynamic changes. Practical recommendations for operational schemes and for the implementation of mitigation measures to hydropeaking were proposed
N/A

Fine-grained sediment accumulation in the interstices of gravel beds is a key factor in degrading riverine habitats. However, interstitial deposits are highly dynamic and are not sufficiently understood. This work enhances the understanding of interstitial fine sediment deposition by investigating interstitial storage and ingress, flow, suspended sediment and gravel bed character. Furthermore, this work introduces a numerical suspended sediment deposition model with the power to predict patterns of interstitial ingress. The investigation of interstitial deposition were carried out on two levels. Both data orginating from flume experiments and from three locations of the River Culm, Devon, UK was collected. The experimental data showed the significant influence of small scale variations in flow and bed character and their influence on interstitial ingress. The field investigation showed clear differences in interstitial fine-grained sediment for the different river reaches and an overall higher interstitial ingress compared to recent published data. The numerical model development was realised in a two-step approach. First, the model was coded and calibrated for the flume scale processes and, second, an upscaled reach scale model was devolped for the field data. This reach scale suspended sediment deposition model included flow information, for which depthaveraged two dimensional hydrodynamic models were developed with the software Delft3D. The overall explanatory power of the model at this state is not satisfactory with regards to local deposition distribution. A separate chapter discusses the possible causes and implications of this short coming for further research from a data aquisition and modelling perspective.

In recent years, a number of high profile accidental fires have occurred in several road and rail tunnels throughout the world. Many of these fires grew rapidly to catastrophic size and claimed many lives. The processes involved in the rapid growth and extremely severe of these fires are not adequately understood as yet. The introduction to this thesis reviews a number of these accidental fires and describes much of the previous experimental research which has brought about the current understanding of tunnel fire behaviour. A detailed review of the relevant parts of elementary fire dynamics is also presented. This thesis addresses two main questions: 1. What is the influence of longitudinal ventilation on fire size in tunnels? and 2. What is the influence of tunnel geometry on fire size? The answers to both these questions are determined using a probabilistic method called Bayes Theorem. This provides a method of answering the above two questions using the handful of experimental data which are available. It is found that the heat release rate (HRR) of a heavy goods vehicle (HGV) fire may be greatly increased in magnitude by longitudinal ventilation, for example by about a factor of 5 with a longitudinal ventilation velocity of 3ms-1. It is also found that longitudinal ventilation may cause a significant increase in the HRR of large pool fires, but may cause a decrease in the HRR of small pool fires and car fires. An equation is derived to predict the influence of tunnel geometry on HRR. It is found that HRR varies principally with the width of the tunnel and the width of the fire object. The HRR of a fire in a tunnel my be increased up to four times due to the geometry of the tunnel.

Lake surface water temperatures (LSWTs) of 246 globally distributed large lakes were derived from Along-Track Scanning Radiometers (ATSR) for the period 1991 to 2011. These LSWTs, derived in a systematic manner, presents an ideal opportunity to study LSWT behaviour on a global scale. In this thesis, the annual cycles of lake-mean LSWTs derived from these data quantify the responses of large lakes’ surface temperatures to the annual cycle of forcing by solar radiation and the ambient air temperature. Minimum monthly net surface solar irradiance (netSSI) strongly influences minimum LSWTs of non-seasonally ice covered lakes (where lake-mean LSWT remains above 1 ºC throughout the annual cycle), explaining > 0.88 (R2 adj) of the inter-lake variation in both hemispheres. In some regions, for seasonally ice covered lakes (where lake-mean LSWT remains below 1 ºC for part of the annual cycle) the minimum monthly netSSI is a better predictor than latitude, of the length of the frozen period, which shows the importance of local cloud climatological conditions. Additionally, at lake locations between 1º S to 12º N, the netSSI, shown to peak twice annually, is reflected in the LSWT annual cycle. The summer maximum LSWTs of lakes from 25º S to 35º N show a linear decrease with increasing altitude; -3.76 + 0.17 ºC km-1 (R2 adj = 0.95), marginally lower than the corresponding air temperature -4.15 + 0.24 ºC km-1 (R2 adj = 0.95) decrease with altitude. The start and end of the period where the lake-mean LSWT is greater than 4 ºC shows strong correlation with the spring and autumn 0 ºC air temperature crossing days, (R2 adj = 0.74 and 0.80 respectively). The temporally and spatially resolved LSWT observations allows for a greater practical understanding of LSWT behaviour of large lakes. For example, lakes with a greater LSWT annual range have more observed variability in the LSWT extremes, highlighting that they may be more responsive to changes in the climate than lakes with a low annual range. The nighttime LSWT trends show stronger warming than day-night trends in the all regions, except Europe. The lake centre LSWT trends and absolute values can be generally considered representative of the lake-mean LSWT trends and absolute values. The observed LSWT time series are used to tune a 1-dimensional thermodynamic lake model, FLake. By tuning FLake using only 3 basic lake properties, shown by myself to have the most influence over LSWTs (depth, snow and ice albedo and light extinction co-efficient), the daily mean absolute differences for 244 lakes is reduced from 3.38 + 2.74 ºC (untuned model) to 0.85 + 0.61 ºC (tuned model). The effect of wind speed, lake depth, albedo and light extinction co-efficient on LSWTs is demonstrated throughout the tuning process. The modelled summer LSWT response to changes in ice-off is strongly affected by lake depth and latitude explaining 0.50 (R2 adj, p = 0.001) of the inter-lake variation in summer LSWTs. Lake depth alone explains 0.35 (p = 0.003) of the variation, highlighting the sensitivity of the summer LSWTs of deeper lakes to changes in the ice-off. Statistically significant summer/ maximum month modelled LSWT trends, from 1979-2011 are presented for lakes where the modelled LSWTs are strongly supported by observed LSWTs over the period of available observed LSWTs. For these lakes, the trends show LSWT warming of between 0.73 – 2.10 ºC for 29 lakes in northern temperate regions over the 33 year period (1979 – 2011). The modelled regional trends of all lakes over the same period show least warming in Africa of 0.30 ºC and the greatest warming in Europe, 1.35 º.

The amount and morphology of the graphite phase largely controls the resulting properties of cast iron. For instance, in flake graphite cast irons the mechanical properties are low while the thermal conductivity is high. This is in contrast with spheroidal graphite cast irons where the mechanical properties are high and the thermal conductivity is low. These differences are due to the different graphite morphologies and must be accounted for in the design work and material selection of cast iron components. In this work the influence of the graphite phase on the elastic and plastic deformation behaviour of cast irons has been studied. The material grades studied originate from castings for marine diesel engine piston rings with different chemical analyses. Two groups of pearlitic cast iron materials were studied; one with differences in graphite morphology and one with grey irons that differed in graphite content. For these different material grades the mechanical properties were correlated to microstructural parameters. In addition to standard uniaxial tensile tests, acoustic emission measurements were used for the study of deformation. When studying the modulus of elasticity of the cast iron it was found that the modulus of elasticity of the inherent graphite phase depends on the roundness of the graphite particles and is due to the strong anisotropy of the graphite phase. A linear correlation between nodularity and the modulus of elasticity of the graphite phase was derived. This correlation made it possible to account for the anisotropy of the graphite phase in the model used. By applying the linear function when modelling the effective modulus of elasticity, a high accuracy between experimental and theoretical values was achieved. Another factor affecting the elastic response when subjecting a cast iron component to tensile load was found to be the plastic deformation that actually occurs at very low strains for all of the studied cast iron grades. It was observed that the plastic deformation in the low strain elastic region, quantified by using acoustic emission measurements, increased linearly with decreasing modulus of elasticity. These measurements showed that the amount of plastic deformation in the elastic region was largely controlled by the graphite morphology. It was concluded that as the roundness of the graphite particles increases, the plastic deformation activity in the elastic region decreases. The plastic deformation activity continued linearly into the pronounced plastic region of the tensile tests. A decrease in roundness or increase in graphite fraction resulted in an increase of the amount of plastic deformation and the strain hardening exponent. A dependence between strength coefficient and graphite fraction was observed. Models for the flow curves for pearlitic cast irons were developed and shown to accurately reproduce the observed experimental curves. The surveys performed and conclusions from this thesis will be helpful in the design of new cast iron materials.

An understanding of compartment fire behaviour is important for fire protection engineers. For design purposes, whether to use a prescriptive code or performance based design, life safety and property protection issues are required to be assessed. The use of design fires in computer modelling is the general method to determine fire safety. However these computer models are generally limited to the input of one design fire, with consideration of the complex interaction between fuel packages and the compartment environment being simplified. Of particular interest is the Heat Release Rate, HRR, as this is the commonly prescribed design parameter for fire modelling. If the HRR is not accurate then it can be subsequently argued that the design scenario may be flawed. Therefore the selection of the most appropriate fire design scenario is critical, and an increased level of understanding of compartment behaviour is an invaluable aid to fire engineering assumptions. This thesis details an experimental study to enhance the understanding of the impact and interaction that the size and location of pool fires within an enclosure have upon the compartment fire behaviour. Thirty four experiments were conducted in a reduced scale compartment (½ height) with dimensions of 3.6m long by 2.4m wide by 1.2m high using five typical ventilation geometries (fully open, soffit, door, window and small window). Heptane pool fires were used, located in permutations of three evenly distributed locations within the compartment (rear, centre and front) as well as larger equivalent area pans located only in the centre. This thesis describes the experimental development, setup and results of the experimental study. To assist in the classification of compartment fire behaviour during the experiments, a ‘phi’ meter was developed to measure the time dependent equivalence ratio. The phi meter was developed and configured to measure O₂, CO₂ and CO. The background development, calibration, and experimental results are reported. A review of compartment fire modelling using Fire Dynamics Simulator, has also been completed and the results discussed. The results of this experimental study were found to have significant implications for Fire Safety Engineering in that the size of the fire is not as significant as the location of the fire. The effect of a fire near the vent opening was found to have a significant impact on compartment fire behaviour with the vent located fuel source increasing the total compartment heat release rate by a factor of 1.7 to that of a centrally placed pool fire of the same total fuel area. The assumption that a fire located in the centre of the room provides for the highest heat release rate is not valid for post-flashover compartment fires. The phi meter was found to provide good agreement with the equivalence ratio calculated from total compartment mass loss rates, and the results of FDS modelling indicate that the use of the model in its current form can not be applied to complex pool fire geometries.

The aim of this thesis was to implement a software that would be able to render, simulate and record a scene with walking pedestrians in real-time, with emphasis on rendering level of realism. The output of the application could serve as an input test data for people counting systems or similar systems for video recognition. The problem was divided into three major subproblems: character animation, artificial intelligence for character movement and advanced rendering techniques. The character animation problem is solved by the skeletal animation of the model. To achieve the characters moving in a scene autonomously path finding(A* algorithm) and group behaviors(steering behaviors) were implemented. Realism in a scene is added by implemented methods such as normal-mapping, variance shadow-mapping, deffered rendering, skydome, lens flare effect and screen space ambient occlusion. Optimaliaztion of the rendering was implemented using octree data structure for space partitioning. Rendering stage of a scene can be easily parametrized through implemented GUI. Implemented application provides the user with easy way of setting a scene with walking pedestrians, setting its visualization and to record the result.

碩士
國立中山大學
機械與機電工程學系研究所
102
A new model to discuss the behavior of flame repetitive ignition/quenching spread in a tiny tube is established in this study. This new model mainly ignores the velocities perpendicular to the flow direction, and therefore, each streamline meets the conservation of mass flow rate with the Poiseullie flow distribution at the entrance. In other words, as the gas temperatures increase, the gas expand and the velocities increase only in the channel direction. In this study, we compare the new model with the CDM(Constant Density Model) and analyze the difference of the simulation results of the two models. The results show that the ignition/quenching frequencies, flame structures, and propagation speed are obviously of great differences. In CDM, the reaction is easily quenched by the wall and oscillation happens earlier; in the new model, reaction is harder to be quenched by the wall after ignition, and small differences are in the reaction rate. In the investigation of the Lewis number effect, when the Lewis number increases, the oscillation and time increase in CDM model; However , in the new model, the oscillation behavior and time decrease. In the investigation of the inlet temperature effect, when temperature increases, oscillation decrease and in the oscillation process, wavelength expand .However, in the new model, the time is reduced into oscillation and reaction rates decrease.

碩士
國立中山大學
機械與機電工程學系研究所
103
In this study, the complete Navier-Stokes equations are used in the mathematical formulation and the flame combustion is modeled by a simplified single-step reaction for methane-air mixture to investigate the different parameters such as wall-temperature, inlet velocity, diverging angle, and distribution of flame behaviors. When wall-temperature is at 600K, the steady tulip-shaped flame exists in the low-velocity region, the oscillating flame in the mid-velocity region, and the slant-shaped flame, with length increasing with velocity, in the high-velocity region. The flame front will move toward the downstream when the velocity increases. When changing the wall-temperature from low to midrange, the steady flame shape is changes from mushroom to tulip and the only to oscillating flame in the high-temperature range. Due to the thermal coupling between the wall-temperature and flame, the location of flame front moves to the upstream when wall-temperature is increased. The diverging angle of the flow channel affects not only the mass flux but also the flow field. The oscillating flame behaviors are observed in small-angle channel and steady flame behaviors in the large angle (θ=5^°) channel. In the research of oscillating flame, increasing inlet velocity makes the flame front moves to the downstream and makes the stretching flame longer. In the high-velocity region, the period of time becomes longer due to the flame extension. The increase of wall-temperature makes the flame front moves toward the upstream, makes the stretching flame shorter and the period of time becomes shorter with the increasing wall-temperature. For the angle effects of diverging channel, the stretching flame becomes shorter with the increase in angle with less effect on the location of flame front. In addition, the oscillating flame in the parallel channel is stronger and more irregular with a short period of time.

Lifted non-premixed turbulent jet flames in the Transverse Instability Combustor (TIC) have been analyzed using qualitative and quantitative methods. Lifted flames in the TIC have been observed to stabilize about zero to five injector exit diameters downstream of the dump plane into the chamber and exhibit pulsating, unsteady burning. Anchored flames immediately begin reacting in the injector recess and burn evenly in a uniform jet from the injector exit through the entire optically accessible region. Statistically significant, repeatable behavior lifted flames are observed. It is shown that the occurrence of lifted flames is most likely for an injector configuration with close wall-spacing, second greatest for a configuration with close middle-element spacing, and lowest for a configuration with even element-spacing. For all configurations, of those elements that have been observed to lift, the center element is most likely to lift while the second element from the wall was likely. Flames at the wall elements were never observed to lift. Evidence is shown to support that close injector element spacing and stronger transverse pressure waves aid lateral heat transfer which supports flame stability in the lifted position. It is hypothesized that the stability of lifted flames is influenced by neighboring ignition sources, often a neighboring anchored flame. It is also shown that instances of lifted flames increase with the root-mean-squared magnitude of pressure fluctuation about its mean (P’ RMS) up to a threshold, after which flames stabilize in the anchored recess position.

Dynamic mode decomposition (DMD) and proper orthogonal decomposition (POD) analyses of CH* chemiluminescence data is performed. It is found that lateral ignition of the most upstream portion of lifted flames is dominated by the 1W mode. Furthermore, it is shown that low-frequency high energy modes with spatial layers resemble intensity-pulses, possibly attributable to ignition. These modes are trademarks of CH* chemiluminescent intensity data of lifted flames. It was also shown that the residence time in the chamber may be closely associated with those low-frequency modes around 200 Hz. DMD and POD were repeated for a downstream region on the center element, as well as a near-wall element, highlighting differences between the lifted flame dynamics in all three regions.

It is shown that lifted flames are best characterized by their burning behavior and in rare cases may stabilize in the recess, while still being “lifted”. Furthermore, it is shown that flame position differentiation can extend into an initial period of highly stable combustor operation. Dynamic mode decomposition is explored as potential method to understand physical building blocks of proper orthogonal spatial layers. Non-visual indicators of lifted flames within the high-frequency (HF) pressure signal are sought to seek a method that allows for observation of lifted flames in optically inaccessible combustors, such as those in industry. Some attributes of power-spectral diagrams and cross-correlations of pressure signals are provided as potential indicators.

碩士
國立臺灣科技大學
材料科學與工程系
101
In this study, we focus the research on the mechanical properties of wood plastic composite (WPC) and miscible of epoxy resin and bamboo flour blending. In addition, the introduction of polyurethane toughens the WPC to improve the impact resistance, and addition of halogen-free flame retardant results in fire resistant. First of all, the DSC (Differential Scanning Calorimetry) and rheometer were utilized for analyzing the curing rate and process conditions.Moreover, we empolyed three point bening test,izod test, falling ball test,creep test,dynamics properties,morphology and combusion test for the composites,and the following results were obtained. As the result, bamboo fiber can enhance the flexural modulus and lower the creep behavior. The flexural modulus and resin dispersiblity reach the optimum as the content of bamboo powder is 100phr. The purpose of epoxy/polyurethane/bamboo powder composite is to improve the impact resistance, and addition of 20phr PU content has obvious improvement. Toughness lead to lower flexural stress and modulus, the creep test was used for durability evaluation. However, no obvious creep behavior under 100 Kgf was observed. The retardant effect can reach the UL94-V0 grade after adding 20 phr flame retardant. The dynamics properties divided into three parts: (1) filler effect (epoxy/bamboo powder composite) : bamboo powder hinder the curing reaction. The decrease of cross-linking density and pot can lead Tg to move to lower temperature. (2) PU content (epoxy/PU composite): The cured epoxy and PU blending result in higher PU Tg temperature and lower epoxy Tg temperature, which means the Interpenetrate network structure formed in the composite. (3)PU content (epoxy/PU/bamboo powder composite): As increasing PU content, the higher epoxy Tg temperature was obtained. The results represent that the miscible of epoxy and bamboo powder can be enhanced effectively due to PU addition.

碩士
國立成功大學
航空太空工程學系
102
The purpose of this study is to develop a standard procedure for artificially synthesize the methane hydrate with consistent and uniform properties for further observation and experiments of the combustion phenomena of methane hydrate. The synthesis procedure is based on ice-seed method, and adding the ethanol as the catalyst to shorten the processing time, if necessary. By packing the ice-seed into different porosity, the synthesized hydrates will also have different porosity. With the larger porosity of the ice-seed, the porosity of the synthesized hydrates will also be greater. In this study, the grain size of the ice-seed is between 180~250μm. The largest packing porosity of ice-seed is between 63.3~66.4%, and the resultant porosity of synthesized hydrate is between 46.62~51.1%. The smallest packing porosity of ice-seed is between 51.8~55.8%, and the porosity of synthesized hydrate is between 40.7~44.9%. Experimental results show that the hydration number of methane hydrate samples that synthesized by ice-seed method is between 6.28~6.6, the hydrate samples have a uniform conversion rate between 87~91%. In addition, the mass release rate of methane hydrate sample per unit area or unit volume can be related to the surface/volume ratio of the sample, the larger surface/volume ratio, the faster release rate of methane per unit area or unit volume. Finally, the combustion phenomena of methane hydrate samples show that both the larger porosity of the methane hydrate sample with the same radius and the smaller radius of the methane hydrate sample with the same porosity can be ignited earlier with shorter ignition delay time and the flame extinguishes earlier with shorter flame lifespan.

碩士
國立臺灣科技大學
纖維及高分子工程技術研究所
85
This study is interested in using Differential Scanning Calorimetry (DSC) to examine and simulate the behavior of cure reaction, to calculate and estimate the cure reaction rate, cure temperature, extent of cure conversion and the variance of glass transition temperature (Tg) with various degree of cure achieved of UPRs/Modar blends that expect to find the best mold process parameter. In order to understand miscibility of UPRs/Modar blends after cured. We used Dynamic Mechanical Analysis (DMA) to approached the Network Aggregate structure and used Scanning Electron Microscopy (SEM) to observe the fractured surfaces of UPRs/Modar blends. On the other hand, the behavior of thermal decomposition of UPRs/Modar blends were studied using Thermal Gravity Analysis (TGA). The combustibility analysis was carried out using NBS smoke density test to study smoke evolution. On the other hand, for analysis of CO gas and Heat Release Rate (HRR) on the combustion procedure, using Cone Calorimetry Dynamic Flammability Evaluation System under 579℃ to research emission of CO gas and variance of HRR of UPRs/Modar blends. The modified unsaturated polyester used synthetic method that reaction with dicyclopenetadiene. The reaction temperature of modified DCPD unsaturated polyester forecast by estimation of the DSC-dynamic scanning. The flame-resistant properties of modified DCPD unsaturated polyester can by using NBS smoke density test under non-flaming process and using Cone Calorimetry Dynamic Flammability Evaluation System.

博士
國立臺灣科技大學
機械工程系
106
The flame behavior and thermal structure of combusting non-premixed plane jets with and without self-excited transverse oscillations were investigated experimentally. The transversely-oscillating plane jet was generated by a specially designed fluidic oscillator. The flame behavior was studied using the instantaneous- and long-exposure photography techniques. Temperature and combustion-product concentration distributions were measured using a fine-wire type-R thermocouple and a gas analyzer, respectively. The results showed that the combusting transversely-oscillating plane jets had distributed blue flames with plaited-like edges, while the corresponding combusting non-excited plane jet had laminar blue-edged flames in the near field. The transversely-oscillating plane jet flames were categorized into three characteristic flame modes: attached flame, transitional flame, and lifted flame. The non-excited plane jet flames showed three flame modes, viz; momentum-deficit flame, transitional flame, and momentum-dominated flame. At high Reynolds number (Rej > 1204), the transversely-oscillating jet flames were significantly shorter and wider with shorter reaction-dominated zones than those of the non-oscillating plane jet flames. In addition, the transversely-oscillating combusting jets presented larger carbon dioxide and smaller unburned hydrocarbon concentrations, as well as portrayed characteristics of partially premixed flames. The non-oscillating combusting jets presented characteristics of diffusion flames. Generally, the transversely-oscillating jet flame had combustion performance characteristics that were superior to its non-oscillating plane jet flame counterpart. The improved combustion performance of the transversely-oscillating jet was due to the enhanced entrainment, mixing, and lateral spreading of the jet flow, which were induced by the vortical flow structure generated by lateral periodic jet oscillations, as well as the high turbulence created by the breakup of the vortices. The effects of co-flowing air streams and aspect ratios on the flame behavior and thermal structure of gaseous fuel jets issued from rectangular nozzles were additionally investigated and discussed.

Background: Organophosphate (OP) pesticides are well-known developmental neurotoxicants that have been linked to abnormal cognitive and behavioral endpoints through both epidemiological studies and animal models of behavioral teratology, and are implicated in the dysfunction of multiple neurotransmitters, including dopamine. Chemical similarities between OP pesticides and organophosphate flame retardants (OPFRs), a class of compounds growing in use and environmental relevance, have produced concern regarding whether developmental exposures to OPFRs and OP pesticides may share behavioral outcomes, impacts on dopaminergic systems, or both. Methods: Using the zebrafish animal model, we exposed developing fish to two OPFRs, TDCIPP and TPHP, as well as the OP pesticide chlorpyrifos, during the first 5 days following fertilization. From there, the exposed fish were assayed for behavioral abnormalities and effects on monoamine neurochemistry as both larvae and adults. An experiment conducted in parallel examined how antagonism of the dopamine system during an identical window of development could alter later life behavior in the same assays. Finally, we investigated the interaction between developmental exposure to an OPFR and acute dopamine antagonism in larval behavior. Results: Developmental exposure to all three OP compounds altered zebrafish behavior, with effects persisting into adulthood. Additionally, exposure to an OPFR decreased the behavioral response to acute D2 receptor antagonism in larvae. However, the pattern of behavioral effects diverged substantially from those seen following developmental dopamine antagonism, and the investigations into dopamine neurochemistry were too variable to be conclusive. Thus, although the results support the hypothesis that OPFRs, as with OP pesticides such as chlorpyrifos, may present a risk to normal behavioral development, we were unable to directly link these effects to any dopaminergic dysfunction.

Dissertation