Subsequent Ignition Research Articles

Stimulated Raman scatter analyses of experiments conducted at the National Ignition Facility

Recent experiments conducted at the National Ignition Facility achieved two main goals: providing radiation drive and symmetry suitable for subsequent ignition experiments. Of the many diagnostics fielded, one provided a time-resolved wavelength spectrum of light reflected from the target by stimulated Raman scatter (SRS). SRS occurs when incident light reflects off self-generated electron plasma waves. Analyses indicate that synthetic SRS spectra better match those of experiments when an atomic physics model with greater emissivity is utilized in target modeling, along with less inhibited electron transport (higher flux, with, ideally, nonlocal electron transport). With these models, SRS occurs in a target region where nearest-neighbor quads of laser beams significantly overlap the diagnosed quad. This increases SRS gain at lower density (lower wavelength), a feature consistent with experimental results. Inclusion of this effect of multiple quads sharing a reflected SRS light wave has resulted in improved capabilities used to successfully predict (preshot) the SRS spectrum from the first target driven with 1.25 MJ of laser energy. Additional resonant amplification of SRS light in the overlap intensity region is demonstrated in beam propagation simulations. Such effects will be reduced in a target optimized for these less dense and cooler plasma conditions.

The determination of liothyronine and thyroxine in thyroid preparations.

Abstract A procedure is described for determining liothyronine and thyroxine in thyroid substances. This involves stepwise hydrolysis with barium hydroxide, extraction of combined iodinated amino-acids by n-butanol, separation and isolation of liothyronine and thyroxine by paper chromatography, subsequent ignition of their separated chromatograms by oxygen flask combustion and estimation of evolved iodine in benzene solution by spectrophotometric absorption at 295 mμ. The method is suitable for routine quality control of thyroid products.

Numerical Analysis of Supersonic Combustion by Strut Flat Duct Length with S-A Turbulence Model

In this numeri cal study, of hydrogen has been presented with strut flat duct length. The combustor has a single fuel injection parallel to the main flow from the base. Finite rate chemistry model with S-A Model have been used for modeling of combustion. In this paper strut at 60 with flat duct length analyzed for without hydrogen injection, with hydrogen injection and hydrogen injection with combustion. The investigation of the shock system produced by a strut injector with subsequent mixing, ignition and flame stabilization showed that the characteristics of the ignition process is considerably different from the shock induced ignition which has been postulated in the past. The ignition is achieved through the irreversible total pressure loss in the wake of Strut due to flat duct length. Flat duct lengths allow the ignition delay to occur before the pressure and temperature is decreased by the expansion. The presence of a boundary layer in the chamber changes the shock system and the ignition conditions in the chamber considerably. Index Term—supersonic combustion, S-A model, finite rate, stagnation temperature, flame speed, Mach number. I. INTRODUCTION Superson ic is the key enabling technology for sustained hypersonic flights. In scramjet engines of current interest, the combustor length is typically of the order of 1 m, and the residence time of the mixture is of the order of Milliseconds. Due to the high flow speed in the chamber, problems arise in the mixing of the reactants, flame anchoring and stability and completion of within the limited combustor length. The flow field in the scramjet combustor is highly complex. It is shown that when the flight speed is low, the kinetic energy of the air is not enough to be used for the optimal compression. Further compression by machines is needed in order to obtain a higher efficiency. For example, a turbojet employs a turbine machine for further compression. When the flight speed is higher than a certain value, the air flow entering a combustor will remain to be after the optimal compression. With a further compression ( i. e. deceleration), the efficiency of the engine will decrease. Therefore the has to take place under the flow condition. This kind of air-breathing engine, which works under hypersonic flight condition, is called the ramjet (Scramjet). The term of supersonic combustion applied here means the

Forensic Engineering Analysis Of A Propane fueled Residential Gas Explosion

The Use Of Liquid Petroleum Or Commercial Propane Gas (Hereafter Referred To As Propane) For Residential heating And Cooking Is Common In The Rural United States Where Providing The Infrastructure For natural Gas Distribution Would Be Too Costly. A Typical Installation May Include A 500 Gallon Pressurized vessel Containing A Mixture Of Liquid And Vapor Propane With The Vapor Fed To An Individual Residence through An Underground Line. Safety Features, Such As Odorization Of The Propane, Multi-Regulator Installations, prudent Selection Of Gas Line Components, And System Leak Checks Are Utilized To Prevent And/Or recognize Fugitive Gas Leaks. in 2005 An Event Occurred In Michigan Which Involved A Flammable Gas Leak, Corrosion, Gas Migration through Soil, A Buildup Of The Flammable Gas, And Subsequent Ignition Resulting In An Explosion which Destroyed A Two Story Home. This Forensic Investigation Eventually Revealed That The Root Cause Of the Incident Lay In Actions Taken During The Original Construction. Some 16 Years After The Installation Of the Subject Gas System Circumstances Came Together To Create An Explosion.

Effects of hydrogen preconversion on the homogeneous ignition of fuel-lean H 2/O 2/N 2/CO 2 mixtures over platinum at moderate pressures

The impact of fractional hydrogen preconversion on the subsequent homogeneous ignition characteristics of fuel-lean (equivalence ratio φ = 0.30) H 2/O 2/N 2/CO 2 mixtures over platinum was investigated experimentally and numerically at pressures of 1, 5 and 8 bar. Experiments were performed in an optically accessible channel-flow reactor and involved Raman measurements of major species over the catalyst boundary layer and planar laser induced fluorescence (LIF) of the OH radical. Simulations were carried out with a 2-D elliptic code that included detailed hetero-/homogeneous chemistry. The predictions reproduced the LIF-measured onset of homogeneous ignition and the Raman-measured transport-limited catalytic hydrogen consumption. For 0% preconversion and wall temperatures in the range 900 K ⩽ T w ⩽ 1100 K, homogeneous ignition was largely suppressed for p ⩾ 5 bar due to the combined effects of intrinsic gas-phase hydrogen kinetics and the competition between the catalytic and gas-phase pathways for fuel consumption. A moderate increase of preconversion to 30% restored homogeneous combustion for p ⩾ 5 bar, despite the fact that the water formed due to the upstream preconversion inhibited homogeneous ignition. The catalytically-produced water inhibited gas-phase combustion, particularly at higher pressures, and this kinetic inhibition was exacerbated by the diffusional imbalance of hydrogen that led to over-stoichiometric amounts of water in the near-wall hot ignitable regions. Radical adsorption/desorption reactions hindered the onset of homogeneous ignition and this effect was more pronounced at 1 bar. On the other hand, over the post-ignition reactor length, radical adsorption/desorption reactions significantly suppressed gas-phase combustion at 5 and 8 bar while their impact at 1 bar was weaker. By increasing hydrogen preconversion, the attained superadiabatic surface temperatures could be effectively suppressed. An inverse catalytically stabilized thermal combustion (CST) concept has been proposed, with gas-phase ignition achieved in an upstream porous burner via radiative and heat conduction feedback from a follow-up catalytic reactor. This arrangement moderated the superadiabatic surface temperatures and required modest or no preheat of the incoming mixture.

Influence of substrate on fire performance of wall lining materials

This study assessed the fire risk of attaching a qualified surface wall lining to an unqualified combustible substrate. Experimental materials were gypsum, magnesium oxide, calcium silicate board and fire-retardant plywood, which were attached to a non-fire-retardant plywood panel. The CNS 6532 Surface Test and the ISO 5660 Cone Calorimeter Test were applied. The former simulates the heating environment in the early fire stage and the latter simulates a fully developed fire. Experimental data show that when a qualified surface material was attached to a non-qualified substrate, the temperature rise in the Surface Test decreased. The substrates consequently enhance fire safety performance in the early stage of fire growth mainly due to crake prevention and a decrease in the amount of heat stored in surface materials for subsequent ignition. Additionally, the heat release rate in the Cone Calorimeter Test increased or decreased when a qualified surface material was attached to a non-qualified substrate. Therefore, the existence of substrates enhances or reduces a material’s combustibility rank when a fire is fully developed. The key mechanism is the crake or flame penetration of surface wall lining, which can lead to substrate ignition. The change of combustibility rank depends on the time at which a crake develops or flames penetrate a substrate.

Experimental and Numerical Study of the Influence of Temperature Heterogeneities on Self-Ignition Process of Methane-Air Mixtures in a Rapid Compression Machine

The self-ignition of methane-air mixtures is analyzed in conditions relevant for Homogeneous Charge Compression Ignition (HCCI) engines from both (i) experimental, and (ii) numerical modeling points of view. On the one hand, a Rapid Compression Machine (RCM) is retained as a pertaining experimental setup to carry out the first part of the study. On the other hand, the PDF method is the modeling framework chosen to describe the coupling between detailed chemical description and turbulent fluctuations. The emphasis is on the influence of the temperature heterogeneities induced by heat transfer during the compression stroke on the subsequent ignition process. Such temperature heterogeneities have already been observed in RCMs (Mittal and Sung, 2006), and they are qualitatively assessed by schlieren imaging in the present study. The simultaneous analysis of the pressure traces and direct visualizations allows to discriminate two distinct modes of ignition exhibiting different levels of coherence of the exothermic process. It is shown that the appearance of one or the other of these two modes is directly related to the temperature distribution at the onset of ignition. Then, the information gathered through the experimental results is used to check the ability of a simplified model to reproduce both qualitatively and quantitatively the observed results. The comparison with the experimental data suggests that the proposed modeling approach provides a well suited framework for further modeling studies of HCCI combustion.

Detailed investigation of ignition by hot gas jets

Experimental and numerical investigations of the ignition of hydrogen/air mixtures by jets of hot exhaust gases are reported. An experimental realisation of such an ignition process, where a jet of hot exhaust gas impinges through a narrow nozzle into a quiescent hydrogen/air mixture, possibly initiating ignition and combustion, is studied. High-speed laser-induced fluorescence (LIF) image sequences of the hydroxyl radical (OH) and laser Schlieren methods are used to gain information about the spatial and temporal evolution of the ignition process. Recording temporally resolved pressure traces yields information about ambient conditions for the process. Numerical experiments are performed that allow linking these observables to certain characteristic states of the gas mixture. The outcome of numerical modelling and experiments indicates the important influence of the hot jet temperature and speed of mixing between the hot and cold gases on the ignition process. The results show the quenching of the flame inside the nozzle and the subsequent ignition of the mixture by the hot exhaust jet. These detailed examinations of the ignition process improve the knowledge concerning flame transmission out of electrical equipment of the type of protection flameproof enclosure.

Predicting the ignition of crown fuels above a spreading surface fire. Part II: model evaluation

A crown fuel ignition model (CFIM) describing the temperature rise and subsequent ignition of the lower portion of tree crowns above a spreading surface fire was evaluated through a sensitivity analysis, comparison against other models, and testing against experimental fire data. Results indicate that the primary factors influencing crown fuel ignition are those determining the depth of the surface fire burning zone and the vertical distance between the ground/surface fuel strata and the lower boundary of the crown fuel layer. Intrinsic crown fuel properties such as fuel particle surface area-to-volume ratio and foliar moisture content were found to have a minor influence on the process of crown fuel ignition. Comparison of model predictions against data collected in high-intensity experimental fires and predictions from other models gave encouraging results relative to the validity of the model system.

Measurements of combustion efficiency in nonequilibrium RF plasma-ignited flows

The paper presents results of combustion efficiency measurements using Fourier transform infrared absorption spectroscopy in premixed hydrocarbon–air and CO–air flows excited by a low-temperature transverse radiofrequency (RF) discharge plasma. The results demonstrate that significant fractions of these fuels are burned in RF plasma-generated and -stabilized flames (up to 100% of ethylene, 70% of methane, and 40% of CO). The results also show that fuel oxidation in the RF plasma-excited flows is most efficient in lean mixtures. Measurements of reaction product concentrations in hydrocarbon–air and CO–air mixtures show that significant amounts of fuel react under conditions when there is no flame detected in the test section. Under these conditions, fuel species oxidation occurs in plasma chemical reactions, without producing ignition. Also, experiments in CO–air flows demonstrated ignition and combustion at the equivalence ratios well below the lean flammability limit for CO. Finally, experiments in higher power RF discharges (500 W) showed that nonequilibrium plasma ignition occurs at flow velocities up to at least u = 60 m / s and at flow residence times exceeding ∼ 1 s . The effect of significant fuel oxidation, which is observed for lean fuel–air mixtures outside the flammable range, before the ignition occurs, provides additional evidence for the nonthermal fuel oxidation triggered by plasma-generated radicals. The present results, combined with previous experiments in which RF plasma ignition was demonstrated to occur in a low-temperature plasma, suggest the following nonequilibrium plasma ignition mechanism: (i) active radical species generation by the nonequilibrium plasma, (ii) plasma chemical reactions of fuel species oxidation with participation of these radicals, (iii) flow heating due to net exothermal plasma chemical fuel oxidation process, and (iv) subsequent thermal ignition and combustion.

High-speed fuel tracer fluorescence and OH radical chemiluminescence imaging in a spark-ignition direct-injection engine

An innovative technique has been demonstrated to achieve crank-angle-resolved planar laser-induced fluorescence (PLIF) of fuel followed by OH* chemiluminescence imaging in a firing direct-injected spark-ignition engine. This study used two standard KrF excimer lasers to excite toluene for tracking fuel distribution. The intensified camera system was operated at single crank-angle resolution at 2000 revolutions per minute (RPM) for 500 consecutive cycles. Through this work, it has been demonstrated that toluene and OH* can be imaged through the same optical setup while similar signal levels are obtained from both species, even at these high rates. The technique is useful for studying correlations between fuel distribution and subsequent ignition and flame propagation without the limitations of phase-averaging imaging approaches. This technique is illustrated for the effect of exhaust gas recirculation on combustion and will be useful for studies of misfire causes. Finally, a few general observations are presented as to the effect of preignition fuel distribution on subsequent combustion.

ATMOSPHERIC, CLIMATIC, AND ECOLOGICAL CONTROLS ON EXTREME WILDFIRE YEARS IN THE NORTHWESTERN UNITED STATES

Wildland fire is an important disturbance agent in forests of the American Northwest. Historical fire suppression efforts have contributed to an accumulation of fuels in many Northwestern forests and may result in more frequent and/or more severe wildfire events. Here we investigate the extent to which atmospheric and climatic variability may contribute to variability in annual area burned on 20 National Forests in Washington, Oregon, and Idaho. Empirical orthogonal function (EOF) analysis was used to identify coherent patterns in area burned by wildfire in the Pacific Northwest. Anomaly fields of 500-hPa height were regressed onto the resulting principal-component time series to identify the patterns in atmospheric circulation that are associated with variability in area burned by wildfire. Additionally, cross-correlation functions were calculated for the Palmer drought severity index (PDSI) over the year preceding the wildfire season. Parallel analyses based on superposed epoch analysis focused only on the extreme fire years (both large and small) to discriminate the controls on extreme years from the linear responses identified in the regression analyses. Four distinct patterns in area burned were identified, each associated with distinct climatic processes. Extreme wildfire years are forced at least in part by antecedent drought and summertime blocking in the 500-hPa height field. However the response to these forcings is modulated by the ecology of the dominant forest. In more mesic forest types antecedent drought is a necessary precondition for forests to burn, but it is not a good predictor of area burned due to the rarity of subsequent ignition. At especially dry locations, summertime blocking events can lead to increases in area burned even in the absence of antecedent drought. At particularly xeric locations summertime cyclones can also lead to increased area burned, probably due to dry lightning storms that bring ignition and strong winds but little precipitation. These results suggest that fuels treatments alone may not be effective at reducing area burned under extreme climatic conditions and furthermore that anthropogenic climate change may have important implications for forest management.

Simplified Modelling for Risk Assessment of Hydrocarbon Spills in Port Area

Several authors, on the basis of mathematical models of different complexity, have faced the study of dispersion and transformations following an open sea oil spill. The different phenomena involved in the release evolution were quantified: convective transport by sea currents; wave action; turbulent diffusion; buoyant action on dispersed particles; superficial spreading of the oil due to different density between sea water and hydrocarbon; and evaporation and emulsification rates. In dealing with a release in the port area, besides the environmental consequences, the most severe hazards are linked to fires and explosions due to the formation of a flammable cloud by evaporated hydrocarbons and air and subsequent ignition. If a cloud of sufficient size is formed and ignition occurs instantly, a large fire, jet flame or fireball may occur, but significant blast-pressure damage is unlikely. Instead, the blast effect produced by vapour cloud explosion (i.e. cloud formation and ignition delayed typically by some minutes) can vary greatly depending on the flame propagation velocity, confinement and turbulence and can result in extensive damage. This paper considers such events in confined areas, focusing on individual intervention time and types more suitable for containing the risk on an acceptable level. Considering that intervention time and dispersion time are comparable, the basic variables allowed for in developing the mathematical model were oil spill spreading rate, hydrocarbon evaporation rate, cloud transport and dispersion into the atmosphere. The simplified model allows identifying risk areas and intervention times in confined regions and ports of relative simple geometry. The same model can also be applied to more complex geometry, typical of port areas, obtaining conservative results for a preliminary risk evaluation. The results of the model, even if conservative, have not yet been tested with laboratory or full-scale data.

Characterization of an in-cylinder flow structure in a high-tumble spark ignition engine

A strong in-cylinder tumbling flow, which was produced by partially shrouding the lower periphery of the inlet valves, was measured in a three-valve twin-spark spark ignition (SI) engine using digital particle image velocimetry (PIV). Characteristics of the bulk flow, cyclic variation, frequency spectrum of velocity fluctuation, large- and small-scale fluctuation kinetic energy and integral length scale are analysed in detail. The possible effects of these flow characteristics on the charge stratification and subsequent ignition and combustion processes are also discussed. The results have shown that the strong tumble field was characterized by a very small velocity component in the direction of the tumble rotational axis until the late stage of the compression stroke. The cyclic variation of the bulk flow, though still present, was significantly reduced. Towards the end of the compression process, both low- and high-frequency velocity fluctuations were found to be high after the tumble had collapsed. The velocity fluctuation component along the cylinder axis was characterized by higher frequencies. An integral length scale was found in the range of 4–9 mm during the compression stroke.

Nonuniform laser ignition in energetic materials

Laser ignition of energetic materials is typically described in terms of a one-dimensional homogeneous ignition model. However, the Gaussian energy distribution from a laser can induce multidimensional effects on ignition. A two-dimensional numerical model that simulates radiant heating and subsequent ignition of energetic materials was developed. A laser with a Gaussian energy distribution was used as the external energy source applied to the flat surface of a cylindrical pellet. The nonuniform behavior of thermal ignition leads to radially dependent ignition times, temperatures, and energy associated with the front surface of the pellet. Existing experimental ignition data was compared to the numerical results. The model shows the importance of a two-dimensional analysis for ignition because the nonuniform external heat source can result in the formation of localized heating that will develop into nonplanar flame propagation. The model is compared to experimental results that further validate the importance of a two-dimensional ignition model and show that ignition occurs first in the center of the pellet where the Gaussian beam intensity is greatest.

Numerical study of fast ignition of ablatively imploded deuterium–tritium fusion capsules by ultra-intense proton beams

Compression and ignition of deuterium–tritium fuel under conditions relevant to the scheme of fast ignition by laser generated proton beams [Roth et al., Phys. Rev. Lett. 86, 436 (2001)] are studied by numerical simulation. Compression of a fuel containing spherical capsule driven by a pulse of thermal radiation is studied by a one-dimensional radiation hydrodynamics code. Irradiation of the compressed fuel by an intense proton beam, generated by a target at distance d from the capsule center, and subsequent ignition and burn are simulated by a two-dimensional code. A robust capsule, absorbing 635 kJ of 210 eV (peak) thermal x rays, with fusion yield of almost 500 MJ, has been designed, which could allow for target gain of 200. On the other hand, for a reasonable proton spectrum the required proton beam energy Eig, exceeds 25 kJ (for d=4 mm), even neglecting beam losses in the hohlraum and assuming that the beam can be focused on a spot with radius of 10 μm. The effects of proton range lengthening due to the increasing plasma temperature and of beam temporal spread caused by velocity dispersion are discussed. Ways to reduce Eig to about 10 kJ are discussed and analyzed by simulations.

Simultaneous laser raman-rayleigh-lif measurements and numerical modeling results of a lifted turbulent H 2/N 2 jet flame in a vitiated coflow

An experiment and numerical investigation is presented of a lifted turbulent H2/N2 jet flame in a coflow of hot, vitiated gases. The vitiated coflow burner emulates the coupling of turbulent mixing and chemical kinetics exemplary of the reacting flow in the recirculation region of advanced combustors. It also simplifies numerical investigation of this coupled problem by removing the complexity of recirculating flow. Scalar measurements are reported for a lifted turbulent jet flame of H2/N2 (Re = 23,600, H/d = 10) in a coflow of hot combustion products from a lean H2/Air flame ((empty set) = 0.25, T = 1,045 K). The combination of Rayleigh scattering, Raman scattering, and laser-induced fluorescence is used to obtain simultaneous measurements of temperature and concentrations of the major species, OH, and NO. The data attest to the success of the experimental design in providing a uniform vitiated coflow throughout the entire test region. Two combustion models (PDF: joint scalar Probability Density Function and EDC: Eddy Dissipation Concept) are used in conjunction with various turbulence models to predict the lift-off height (H(sub PDF)/d = 7,H(sub EDC)/d = 8.5). Kalghatgi's classic phenomenological theory, which is based on scaling arguments, yields a reasonably accurate prediction (H(sub K)/d = 11.4) of the lift-off height for the present flame. The vitiated coflow admits the possibility of auto-ignition of mixed fluid, and the success of the present parabolic implementation of the PDF model in predicting a stable lifted flame is attributable to such ignition. The measurements indicate a thickened turbulent reaction zone at the flame base. Experimental results and numerical investigations support the plausibility of turbulent premixed flame propagation by small scale (on the order of the flame thickness) recirculation and mixing of hot products into reactants and subsequent rapid ignition of the mixture.

Residual Gasoline in a Turbulent Pacific Northwest Stream Following Release and Subsequent Ignition

ABSTRACT Approximately 5,500 barrels of unleaded gasoline escaped from a ruptured pipeline in Bellingham, Washington on June 10, 1999. The majority of the product entered Whatcom Creek, with a flow of approximately 0.3 m3/s (10 cfs). The gasoline affected approximately 4.8 km (3 miles) of the creek. After a period of approximately 4 hours, the product contacted an ignition source. Twenty hours following the incident, a water-sampling program at 8 stations in Whatcom Creek and 12 stations in Bellingham Bay was implemented. Ultimately, nearly 400 water-column samples were analyzed for gasoline range hydrocarbons (GRHs), including BTEX compounds and MTBE. Samples were collected every 4 hours for the first 5 days, daily for the next 17 days, and 16 of the following 32 days. Initial maximum concentrations found in water samples were 20,800 ug/L GRH, 2,600 ug/L total xylenes, 1,300 ug/l toluene, 340 ug/L ethylbenzene, 110 ug/L benzene, and 6.9 ug/L MTBE. Product concentrations in the stream declined rapidly. Within 140 hours of the incident, GRHs subsided two orders of magnitude. Instream waters met State of Washington Groundwater Cleanup Standards (Washington Administrative Code, Chapter 173–340.) in an average of 131 hours from the time of the release for benzene, 127 hours for ethylbenzene, 66 hours for toluene, and 207 hours for xylene. Volatilization of BTEX during transport downstream was evidenced by a consistent gradient of reduced concentrations with distance from the source. Sediment pore water and bulk sediments were also sampled. Initial pore-water GRH ranged widely from nondetect to 110,000 ug/L. GRH in bulk sediment samples ranged from nondetect to 447,000 ug/L. A remediation program was conducted to release product trapped in the streambed that reduced contaminants to levels deemed acceptable by a risk-based approach for survival of salmonid fry populations. This approach and resultant guidelines are described.

Convection Effects on the Endothermic Gasification and Piloted Ignition of a Radiatively Heated Combustible Solid

A study is presented on the effect of convective conditions on the endothermic gasification and subsequent ignition of a slab of solid material heated by a radiant flux. A simple solid-phase thermal model is numerically integrated to approximately reproduce results of a previous experimental study of piloted ignition. The model is formulated in terms of the transient energy equation including endothermic Arrhenius-type pyrolysis and Beer-law in-depth absorption of the radiant flux. Temperature evolution curves are obtained for different values of the heat flux and convective coefficient, and are shown to accurately predict experimental surface temperature measurements prior to ignition. Material gasification rates are calculated and used in conjunction with the experimental ignition results to show that the piloted ignition delay closely corresponds to the time required by the solid to reach a critical value of the gasification rate. The critical gasification rate is nearly constant and independent of the heat flux for given convective conditions, and increases linearly with the convective coefficient. It is shown that the graphs of piloted ignition delay vs. heat flux may be accurately determined from this critical gasification criterion. Finally, a non-dimensional parameter that represents the relative amount of gasified fuel transported by the oxidizer stream is presented as a suitable measure of the flammability of the material.

Fluidized-bed combustion synthesis of titanium nitride

A detailed experimental study of the self-propagating high-temperature synthesis of titanium nitride was conducted to improve the conversion yield and illustrate the mechanism of formation of titanium nitride. The investigation was performed at atmospheric pressure, room temperature, and normal gravity conditions in a fluidized bed of gaseous nitrogen and solid titanium particles of approximately 50 μm. This fluidized-bed combustion system successfully produced a homogeneous dispersion of titanium particles in the nitrogen stream via a dual-syringe particle injection system, and subsequent particle ignition led to the gradual propagation of a combustion wave. From the combustion reaction, a maximum conversion yield of titanium nitride was obtained of approximately 60%. The high conversion yield was ascribed to increased introgen accessibility to the precursor particle surface by increasing the interstitial distances between particles in fluidization. The composition of the product particles was analyzed both qualitatively and quantitatively by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and X-ray diffraction. Based on the measurement of combustion temperature and subsequent calculation of heat transfer, a liquid mechanism is indicated for the formation of titanium nitride obtained in the combustion synthesis system.