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.

Em motores de combustão interna, o entendimento do processo de combustão é de fundamental importância para o desenvolvimento de modelos de queima empregados em simuladores de ciclos termodinâmicos, sendo a curva de pressão medida na câmara uma das principais fontes de informações a respeito deste processo. Além disto, este entendimento fornece subsídios valiosos para o projeto e desenvolvimento de novas câmaras de combustão, de componentes e do próprio motor. O objetivo deste trabalho é, a partir da medição da pressão na câmara de combustão de motores de ignição por centelha, obter informações a respeito da evolução da combustão, tais como taxa de liberação de calor e fração de massa queimada em função da posição angular do virabrequim. Para tanto, supõe-se a câmara de combustão dividida em três zonas, a saber: a de gases não queimados, composta pela mistura fresca admitida pelo motor e uma fração de gases residuais; a de gases queimados resultantes da combustão e a de gases não queimados contidos em frestas. Uma frente de chama adiabática, com formato esférico e interagindo com as paredes da câmara é admitida como interface entre as zonas queimada e não queimada. São também considerados os efeitos da dissociação química dos produtos da combustão, de troca de calor com as paredes e os de vazamento de gases da câmara para o cárter (blow-by). O modelo construído a partir destas hipóteses foi traduzido em um código computacional e aplicado a curvas de pressão geradas por um simulador e obtidas experimentalmente em um motor específico. / Understanding the combustion process in IC engines is very important to develop combustion models used in thermodynamic cycle simulators, and the in-cylinder pressure history is the basic source of information about this process. Besides, this understanding provides valuable knowledge to design and develop new combustion chambers, components and the engine itself. The purpose of the present work is to obtain information about combustion development in SI engines from in-cylinder pressure measurements, in terms of variables such as heat release and mass fraction burned as a function of crank angle. The combustion chamber is divided into three zones, comprising burned gases, mixture of fresh charge and residual gases, and gases in crevices. A spherical and adiabatic flame front that interacts with the chamber walls is assumed to separate the burned and unburned zones. The proposed model considers chemical dissociation at high temperatures, heat transfer and blow-by as well. The model built from the assumptions above was implemented as a numerical code and applied to a specific engine, using both cylinder gas pressure data from a cycle simulator and experimentally obtained.

Les incendies de végétation sont caractérisés par de nombreuses échelles de temps et d’espace. Une approche multi-physique et multi-échelle est donc nécessaire pour aborder la complexité de ces phénomènes. Ce travail de thèse est une contribution expérimentale à l’étude des effets d’échelle et du système sur la dynamique de combustion des végétaux et les fumées émises. Notre objectif principal a été de déterminer quels protocoles expérimentaux et plus particulièrement quelles échelles permettent de caractériser au mieux la combustion des végétaux en laboratoire. Nous avons ainsi étudié le comportement au feu des aiguilles de deux espèces de pin représentatives de l’écosystème méditerranéen, Pinus pinaster et Pinus laricio. Les litières d’aiguilles de pin représentent un enjeu important car elles entretiennent la propagation des incendies et elles participent à la transition d’un feu de surface à un feu total. Trois configurations expérimentales ont été étudiées au cours de cette thèse, l’échelle du cône calorimètre, l’échelle du grand calorimètre ou LSHR (permettant la combustion statique de masses plus importantes que le cône) et enfin, la propagation dans le LSHR permettant d’étudier l’effet du système sur la dynamique de la combustion et sur la production des fumées. Pour comparer ces trois configurations les protocoles expérimentaux ont été adaptés tout en maintenant la charge de combustible. Différents paramètres ont été étudiés pour analyser la dynamique de combustion tels que l’efficacité de la combustion, l’énergie dégagée ou encore la vitesse de perte de masse. La production des fumées a été étudiée par la mesure du coefficient d’extinction qui caractérise leur opacité et permet d’obtenir le facteur d’émission des suies. Les facteurs d’émissions des principaux composés émis lors de la combustion de ces deux types d’aiguilles de pin ont été mesurés en continu à partir d’un analyseur Infrarouge à Transformée de Fourier et d’un analyseur Infrarouge Non Dispersif. Des analyses par chromatographie en phase gazeuse couplée à un détecteur à ionisation de flamme et un spectromètre de masse nous ont permis de compléter ces mesures. Un bilan massique de carbone a également été réalisé afin de quantifier le carbone total mesuré dans nos analyses. Les principales contributions de notre travail sont les suivantes : l’étude du comportement au feu des aiguilles de P. pinaster a révélé des différences importantes pour la puissance dégagée aux échelles du cône calorimètre et du LSHR. En revanche, le système de combustion (propagation) n’influence pas cette grandeur. L’efficacité de la combustion est apparue peu dépendante de l’échelle et du système de combustion. Nous avons observé une influence de l’échelle de combustion sur la production totale des fumées (RSR) et sur le facteur d’émission des suies. Nous avons également montré que le système de combustion (la propagation) influence la dynamique et la valeur des facteurs d’émission de dioxyde et de monoxyde de carbone, composés majoritairement émis par ces combustions. Une influence de l’échelle et du système est également à noter sur les facteurs d’émissions des composés azotés et des COV émis pour les trois configurations expérimentales. Nous avons attribué les différences observées aux valeurs de températures des fumées. Enfin, une influence de la géométrie des particules a été mise en évidence par comparaison des combustions réalisées avec le cône calorimètre et le LSHR pour les deux types d’aiguilles de pin. La dynamique de combustion des aiguilles de Pinus laricio est moins affectée par le changement d’échelle que celle des aiguilles de Pinus pinaster (plus faible variation de la puissance de combustion). Nous avons également observé que les aiguilles de Pinus laricio, thermiquement plus fines que les aiguilles de Pinus pinaster présentent une valeur plus faible pour le facteur d’émission des suies. / Wildfires are characterized by a lot of scales of time and space. A multi-physics and multi-scale approach is required to consider the complexity of these phenomena. This thesis is an experimental contribution to the study of the scale effects and the effects of the system on the combustion dynamics of forest fuels and smoke emission. The aim of this work was to determine which experimental protocols and specifically which scales can be used to characterize the combustion of vegetal fuels in the laboratory. The reaction to fire of pine needles species representative of the Mediterranean ecosystem, (Pinus pinaster and Pinus laricio) has been studied. Litters of pine needles are an important issue because they sustain fire spread and are involved in the transition from a surface fire to a total fire.Three experimental configurations were studied in this thesis: the cone calorimeter scale; the large scale calorimeter or LSHR (allowing static combustion with larger masses than used with the cone); a fire spread in the LSHR, allowing to study the effect of the system on the dynamics of combustion and release of smoke. To compare these configurations, experimental protocols have been elaborated while keeping the same fuel load. Different parameters were studied to analyze the combustion dynamics such as combustion efficiency, heat released rate and mass loss rate. Smoke production was studied by measuring the coefficient of extinction to characterize their opacity and an estimation of the soot emission factor was derived. The emission factors of the main compounds emitted during the combustion of these two pines needles were measured with a Fourier Transform Infrared analyzer and a Non-dispersive infrared analyzer. Analysis by gas chromatography coupled with a flame ionization detector and a mass spectrometer allowed us to complete these measurements. A mass balance of carbon was also performed to quantify the total carbon measured through our analyzes.The main contributions of our work can be summarized as follow: the study of the burning of Pinus pinaster needles reveals significant differences for heat release rate (HRR) at both cone calorimeter and LSHR scales. However, the combustion system (fire spread) does not influence the HRR value at the LSHR scale. The combustion efficiency appeared to be independent with regard to the scale and the system. We observed a wide influence on the rate of smoke release and the emission factor of soot. We also shown that the combustion system (fire spread) influences the dynamics and value of emissions factors of carbon dioxide and carbon monoxide (major compound emitted for these combustions). An influence of the three experimental configurations on the emission factors of nitrogen compounds and VOC emissions was also noted. This difference was attributed to the level of smoke temperature. Finally, an effect of particles geometry was also pointed out by the comparison between the burnings performed with the cone calorimeter and the LSHR for both types of pine needles. The combustion dynamics of Pinus laricio needles was slighlty affected by changing scale in comparison to needles of Pinus pinaster (weak variation of HRR). We also observed that Pinus laricio’s needles, which are thermally thiner than Pinus pinaster ones have the lowest soot emission factor.

The fire development and flame spread in the railway carriages are investigated by performing a set of simulations using a widely accepted simulation software called &amp / #8216 / Fire Dynamics Simulator&amp / #8217 / . Two different rolling stock models / representing a train made up of physically separated carriages, and a 4-car train with open wide gangways / have been built to examine the effects of train geometry on fire development and smoke spread within the trains. The simulations incorporate two different ignition sources / a small size arson fire, and a severe baggage fire incident. The simulations have been performed incorporating variations of parameters including tunnel geometry, ventilation and evacuation strategies, and combustible material properties. The predictions of flame spread within the rolling stock and values of the peak heat release rates are reported for the simulated incident cases. In addition, for a set of base cases the onboard conditions are discussed and compared against the tenability criteria given by the international standards. The predictions of heat release rate and the onboard conditions from the Fire Dynamics Simulator case studies have been checked against the empirical methods such as Duggan&amp / #8217 / s method and other simulation softwares such as CFAST program.

Fire is a complex phenomenon including many parameters. The nature of fire makes it a very dangerous and hazardous. For many reasons the number of tunnels are increasing on earth and fire safety is one of the major problem related to tunnels. This makes important to predict and understand the behavior of fire, i.e., heat release rate, smoke movement, ventilation effect etc. The literature includes many experimental and numerical analyses for different conditions for tunnel fires. This study investigates pool fire of three different fuel sources: ethanol, gasoline and their mixture for different ventilation conditions, different geometries and different amounts. Combustion gases and the burning rates of the fuel sources are measured and analyzed. The numerical simulation of the cases is done with Fire Dynamics Simulator (FDS), a CFD code developed by NIST.

Information from the TRMM-CSH and TRMM-2A12 datasets is used to examine the four-dimensional latent heating (LH) structures over the Asian monsoon region between 1998 and 2006. High sea surface temperatures, ocean-land contrasts and complex terrain produce large precipitation and atmospheric heating rates whose spatial and temporal characteristics are relatively undocumented. Analyses identify interannual and intraseasonal LH variations, with a large fraction of the interannual variability induced by internal intraseasonal variability. Also, the analyses identify a spatial dipole of LH anomalies between the equatorial Indian Ocean and the Bay of Bengal regions occurring during the summer active and suppressed phases of the monsoon intraseasonal oscillation. Comparisons made between the TRMM-CSH and TRMM-2A12 datasets indicate significant differences in the shape of the vertical profile of LH. Comparison of TRMM-LH retrievals with sounding budget observations made during the South China Sea Monsoon experiment shows a high correspondence in the timing of positive LH episodes during rainy periods. Negative values of LH, associated with radiative cooling and with higher troposphere cooling from non-precipitating clouds, are not captured by any of the TRMM datasets. In summary, LH algorithms based on satellite information are capable of representing the spatial and temporal characteristics of the vertically integrated heating in the Asian monsoon region. The TRMM-CSH presents better performance than TRMM-2A12. However, the vertical distribution of atmospheric heating is not captured accurately throughout all different convective phases. It is suggested that satellite derived radiative heating/cooling products are needed to supplement the LH products in order to give an overall better depiction of atmospheric heating.

<p>The theme of this thesis is the reaction to fire performanceof wood and other building products, andparticularly thematerial fire properties time to ignition, rate of heat releaseand smoke production. These properties have been measured by asmall-scale fire test method, the Cone Calorimeter, andpresented for different types of building products.</p><p>Uncertainty analysis, included instrument and assumptionuncertainty, has been performed for the case that both O2 andCO2 are measured for calculation of the rate of heat release inthe Cone Calorimeter. The partial derivatives for theuncertainty analysis are given. The relative uncertainty forthe rate of heat release measurements in the Cone Calorimeteris between ±5% to ±10% for rate of heat releasevalues larger than about 50 kW/m2.</p><p>The time to ignition in the Cone Calorimeter is compatiblewith the time to ignition in the ISO Ignitability test, whichis the main test method for measuring time to ignition. Thetime to ignition is an increasing linear function of density.The rate of heat release in the Cone Calorimeter is dependentof material thickness and of use of retainer frame. Thematerial thickness gives the heat release curve duration andshape. Thin materials have short burning time and two maximumvalues. Thick materials have long burning time and when thematerial is thicker than about 35 mm no second maximum appears.When the retainer frame is used the actual exposed surface isreduced from 0.01 m2 to 0.0088 m2, the rate of heat release isreduced and the burning time is increased. A comparison ofresults with and without use of the retainer frame gives thenequal results when the exposed area is set to 0.0088 m2 in thecase of using the retainer frame.</p><p>The time to flashover in the full-scale room corner test waspredicted on the basis of Cone Calorimeter data at 50 kW/m2 bya power law of ignition time, the total heat release calculatedover 300 s after ignition and the density of the product. Therelation gives a simple relation to evaluate if a productreaches flashover in the room corner test.</p><p>The smoke production has also been measured in the ConeCalorimeter. The white light and the laser smoke measurementsystems have shown similar results. There is a correlationbetween Cone Calorimeter and room corner test smoke productionwhen the products are divided into groups: those that reachflashover in the room corner test in less than 10 min and thosethat have more than 10 min to flashover. Temperature profilesin wood have been measured in the Cone Calorimeter by a simpletechnique. The effect of fire protective gypsum plasterboardson the charring of wood frame members has been determined andcompared with fullscale furnace wall tests. The protectiveeffects of twenty different boards have been presented. ConeCalorimeter and furnace tests show similar charring of wooduntil the boards fall down in furnace tests. After that, thecharring of wood is higher in the furnace, because the wood isexposed directly to the fire.</p><p><b>Keywords:</b>building products, charring of wood, ConeCalorimeter, fire retardant treated wood, fire tests,ignitability, mass loss, rate of heat release, reaction tofire, smoke production, wood products</p>

The present thesis deals with the fundamental aspects of turbulent mixing and non-premixed combustion in the wall-jet flow, which has a close resemblance to many industrial applications. Direct numerical simulations (DNS) of turbulent wall-jets with isothermal and exothermic reactions are performed. In the computational domain, fuel and oxidizer enter separately in a nonpremixed manner and the flow is compressible, fully turbulent and subsonic. The triple “turbulence-chemistry-wall” interactions in the wall-jet flow have been addressed first by focusing on turbulent flow effects on the isothermal reaction, and then, by concentrating on heat-release effects on both turbulence and flame characteristics in the exothermic reaction. In the former, the mixing characteristics of the flow, the key statistics for combustion and the near-wall effects in the absence of thermal effects are isolated and studied. In the latter, the main target was to identify the heat-release effects on the different mixing scales of turbulence. Key statistics such as the scalar dissipation rates, time scale ratios, two-point correlations, one and two-dimensional premultiplied spectra are used to illustrate the heat release induced modifications. Finer small mixing scales were observed in the isothermal simulations and larger vortical structures formed after adding significant amounts of heat-release. A deeper insight into the heat release effects on three-dimensional mixing and reaction characteristics of the turbulent wall-jet flow has been gained by digging in different scales of DNS datasets. In particular, attention has been paid to the anisotropy levels and intermittency of the flow by investigating the probability density functions, higher order moments of velocities and reacting scalars and anisotropy invariant maps for different reacting cases. To evaluate and isolate the Damkohler number effects on the reaction zone structure from those of the heat release a comparison between two DNS cases with different Damkohler numbers but a comparable temperature rise is performed. Furthermore, the wall effects on the flame and flow characteristics, for instance, the wall heat transfer; the near-wall combustion effects on the skin-friction, the isothermal wall cooling effects on the average burning rates and the possibility of formation of the premixed mode within the non-premixed flame are addressed. The DNS datasets are also used for a priori  analysis, focused on the heat release effects on the subgrid-scale (SGS) statistics. The findings regarding the turbulence small-scale characteristics, gained through the statistical analysis of the flow have many phenomenological parallels with those concerning the SGS statistics. Finally, a DNS of turbulent reacting wall-jet at a substantially higher Reynolds number is performed in order to extend the applicability range for the conclusions of the present study and figuring out the possible differences. / <p>QC 20150225</p>

Flame chemiluminescence has received increasing attention for its potential sensor and diagnostic applications in combustors. A number of studies have used flame chemiluminescence to monitor flame status, and combustor performance. While most of these studies have been empirical in nature, chemiluminescence modeling has the potential to provide a better understanding of the chemiluminescence processes and their dependence on various combustion operating conditions. The primary objective of this research was to identify and validate the important chemiluminescence reaction mechanisms for OH*, CH* and CO2*. To this end, measurements were performed at various operating conditions, primarily in laminar, premixed flames, fueled with methane, syngas (H2/CO) and Jet-A. The results are compared to 1-d laminar flame simulations employing the chemiluminescence mechanisms. The secondary objective was to use the experiments and validated chemiluminescence reaction mechanisms to evaluate the usefulness of flame chemiluminescence as a combustion diagnostic, particularly for heat release rate and equivalence ratio. The validation studies were able to identify specific mechanisms for OH*, CH* and CO2* that produced excellent agreement with the experimental data in most cases. The mechanisms were able to predict the variation of the chemiluminescence signals with equivalence ratio but not with pressure and reactant preheat. The possible reasons causing this disagreement could be due to the inaccuracies in the basic chemical mechanism used in the simulations, lack of accurate quenching data (for CH*), thermal excitation (for OH*) and radiative trapping (for OH* and CO2*) and interference from the emissions of other species (such as HCO and H2O), for CO2*. Regarding the utility of chemiluminescence for sensing, a number of observations can be made. In syngas-air flames, CO2* is a reasonable heat release rate marker, at least for very lean conditions. OH* shows some advantage in atmospheric-pressure methane and Jet-A flames in general, while CH* is advantageous at high pressure and very lean conditions at atmospheric pressure. The CO2*/OH* intensity ratio is not useful for sensing equivalence ratio in syngas flames, except maybe at very lean conditions. However, the CH*/OH* signal ratio is a promising approach for sensing equivalence ratio at low or very high pressure conditions in hydrocarbon flames. Thermal excitation and self-absorption processes for OH* chemiluminescence can become important for combustors operating at high pressure, high preheat and near stoichiometric conditions. Background subtracted chemiluminescence signals are recommended for sensing purposes.

This thesis describes computational and theoretical studies of fundamental physical processes that influence the heat-release response of turbulent premixed flames to acoustic forcing. Attached turbulent flames, as found in many practical devices, have a non-zero mean velocity component tangential to the turbulent flame brush. Hence, flame surface wrinkles generated at a given location travel along the flame sheet while being continuously modified by local flow velocity disturbances, thereby, causing the flame sheet to respond in a non-local manner to upstream turbulence fluctuations. The correlation length and time scales of these flame sheet motions are significantly different from those of the upstream turbulence fluctuations. These correlation lengths and times increase with turbulence intensity, due to the influence of kinematic restoration. This non-local nature of flame sheet wrinkling (called 'non-locality') results in a spatially varying distribution of local consumption speed (i.e. local mass burning rate) even when the upstream flow statistics are isotropic and stationary. Non-locality and kinematic restoration result in coupling between the responses of the flame surface to coherent acoustic forcing and random turbulent fluctuations respectively, thereby, causing the coherent ensemble averaged component of the global heat-release fluctuation to be different in magnitude and phase from its nominal (laminar) value even in the limit of small coherent forcing amplitudes (i.e. linear forcing limit). An expression for this correction, derived from an asymptotic analysis to leading order in turbulence intensity, shows that its magnitude decreases with increasing forcing frequency because kinematic restoration limits flame surface wrinkling amplitudes. Predictions of ensemble averaged heat release response from a different, generalized modeling approach using local consumption and displacement speed distributions from unforced analysis shows good agreement with the exact asymptotic result at low frequencies.