Ignition Delay Time Research Articles

In-situ heteroatoms stabilization of zero-dimensional boron nanospheres for high-energy nanofluid fuels combustion enhancement

Since boron powder has the highest volume energy density, it has long been desired for use as fuel in aerospace and other fields. However, boron has poor ignition performance and low combustion efficiency due to uneven microstructure and oxide layers of boron. Here, we report a facile strategy to prepare zero-dimensional boron nanospheres from micrometer-scale amorphous boron through ultrasound-assisted in-situ stabilization of heteroatoms for inhibition of boron oxide layer by using hexachlorocyclotriphosphazene (HCCP) and 4,4′-sulfonyldiphenol (BPS) polycondensation and carbonization. The diameter of the obtained boron nanospheres was in the range of 500–800 nm, which is the smallest reported diameter of regular boron nanoparticles. The initial reaction temperature of CPZS@B-1.0 decreased from 791.1 to 641.7 °C, and the ignition delay time of 20 wt% CPZS@B-1.0/RP-3 nanofluid fuel decreased to 393 ms. The addition of CPZS@B promoted RP-3 oxidation at both low temperatures (<200 °C) and high temperatures (>200 °C) by in-situ FTIR analysis. Notably, the prepared zero-dimensional nano-boron exhibited removal of surface oxidation and complete combustion degree (from 42.06 % to 80.36 %). This work provides a new method for the preparation of nano-boron and a solution for increasing the fuel energy density of hydrocarbon fuels.

Experimental Combustion of Different Biomass Wastes, Coals and Two Fuel Mixtures on a Fire Bench

When designing settlements according to the “Green Building” principle, it is necessary to develop a heating system based on climatic conditions. For example, in areas with a sharply continental climate (cold and prolonged winters), it is sometimes necessary to use solid fuel boilers (in the absence of gas). However, to use these, it is necessary to use biomass or biomass-coal blends as fuel to increase their combustion heat. The addition of biomass waste to coal can be aimed at achieving various objectives: utilization of biomass waste; reduction of solid fossil fuel consumption; improvement of environmental performance at coal-fired boiler houses; improvement of the reactivity of coals or to improve the technical and economic performance of heat-generating plants due to the fact that biomass is a waste from various types of production, and its cost depends only on the distance of its transportation to the boiler house. In this work, combustion of various biomass wastes, including sewage sludge, was carried out on a fire bench emulating the operation of a boiler furnace. Fuel particles were ignited by convective heat transfer in a stream of hot air at a velocity of 5 m/s in the temperature range of 500–800 °C, and the experimental process was recorded on a high-speed, color video camera. The obtained values were compared with the characteristics of different coals used in thermal power generation (lignite and bituminous coal). The aim of the work is to determine the reactivity of various types of biomass, including fuel mixtures based on coal and food waste. The work presents the results of technical and elemental analysis of the researched fuels. Scanning electron microscopy was used to analyze the fuel particle surfaces for the presence of pores, cracks and channels. It was found that the lowest ignition delay is characteristic of cedar needles and hydrolyzed lignin; it is four times less than that of lignite coal and nine times less than that of bituminous coal. The addition of hydrolysis lignin to coal improves its combustion characteristics, while the addition of brewer’s spent grain, on the contrary, reduces it, increasing the ignition time delay due to the high moisture content of the fuel particles.

Ignition and energy release performance of dual‐oxidant Al/MnO2/CuO ternary thermites under rapid heating conditions

AbstractTailoring the energy release performance of the thermites is crucial for their application in various fields. In this article, dual‐oxidant Al/MnO2/CuO ternary thermites with varying compositions were prepared and systematically evaluated. The ignition delay time, heat of reaction, self‐sustained burning rate, and pressure performance of the thermites were evaluated. As the Al/CuO content increased, the ignition delay time and heat of reaction decreased, while the reaction efficiency, burning rate, pressure peak, and pressurization rate increased. Furthermore, the synergistic addition of the MnO2 and CuO led to enhanced relative flame intensity and maximum flame temperature in the ternary thermite. Our work demonstrates an effective strategy for regulating the energy performance of the thermites by co‐adding of metal oxides. This approach opens avenues for tailoring thermite properties to meet the diverse requirements of various applications.

Development of a reduced primary reference fuel – oxymethylene dimethyl ether (PRF-OMEx) mechanism for diesel engine applications

Oxymethylene dimethyl ethers (OMEx), having a chemical formula of CH3O-(CH2O)x-CH3 where x varies from 1 to 5, have been widely considered as a promising fuel to partially replace diesel in CI engines in terms of reducing soot emissions. This work is focused on developing a reduced primary reference fuel (PRF)-OMEx chemical mechanism to better describe the combustion and emission characteristics of gasoline/diesel blends with OMEx. The novelty of this work lies in the fact that the OMEx part of the mechanism is represented not only by OME3 as done in most studies found in literature, but also with other OME chain lengths that is, OME2-4 which are considered to be optimum and better represent the commercial OMEx blends. For this purpose, a detailed OMEx mechanism is reduced by applying different reduction techniques considering a wide range of operating conditions including pressure, temperatures, equivalence ratios and fuel compositions. The result is merged with an already validated PRF mechanism to form a reduced PRF-OMEx mechanism consisting of 213 species and 840 reactions. The newly formed mechanism is validated against a wide set of experimental data including ignition delay times, laminar flame speeds and species concentration profiles. Furthermore, a rigorous set of numerical simulations for various diesel-OMEx blends in a compression ignition engine are carried out at two different operating points to validate the developed mechanism. Simulation results highlight that the developed mechanism not only replicates the experimental behavior in terms of in-cylinder pressure and heat release rate but exhibits a better combustion phasing closer to experimental data when compared with other mechanisms where only OME3 is utilized to represent OMEx. Overall, the developed PRF-OMEx mechanism proves to be realistic and suitable for application in engine combustion simulations involving gasoline/diesel and OMEx blends.

Importance of Spin Channels from Radical-Radical Reactions in Hydrogen-Oxygen Combustion Mechanisms at High Temperatures.

Radical-radical reactions can generate two channels with high and low spins. In this work, ten radical-radical reactions with different spin channels and four radical-molecule reactions in hydrogen-oxygen combustion were systematically investigated from a theoretical perspective. The potential energy surface (PES) of radical-radical reactions reveals that the high- and low-spin states of the reactant are energetically degenerate and the two channels are energetically feasible. The difference in rate constants between the high- and low-spin channels gradually decreases as the temperature increases. Then, the kinetic parameters of the 14 bimolecular reactions in the hydrogen-oxygen mechanism of the University of California, San Diego (UCSD), were replaced to simulate the ignition delay time and laminar flame speed. The simulation results agree well with the available experimental findings, indicating the necessity of considering both high- and low-spin channels for kinetic simulation.

Using methane hydrate to intensify the combustion of composite slurry fuels

Combustion of composite slurry fuels based on industrial and municipal waste is an effective way to both recover the said waste and address the problem of fossil fuel depletion. The flexible composition of such fuels can be adjusted to include raw materials available in any specific region of the world. Another benefit they provide is the opportunity to recover waste in different proportions to conventional fuels. There is, however, a problem of long ignition delay times of composite slurry fuels, especially if they contain a significant proportion of water or high-moisture wastes. Here we suggest intensifying their ignition by involving methane released from gas hydrates. Gas hydrates contain a large amount of water that reduces the concentrations of sulfur, nitrogen, and carbon oxides in flue gases. The experimental findings have shown that the involvement of gas hydrate reduces the ignition delay time of a coal-water slurry droplet by more than four times. Adding gas hydrate also contributes to higher combustion temperature and degree of fuel combustion. On the basis of the results obtained, we propose a coal-water slurry/gas hydrate co-combustion system for energy production facilities.

The premixed flame structure and combustion mechanism of clean hydrogen mixed with multi-component natural gas

Hydrogen is widely taken for the most potential clean energy for the moment. Currently, pipeline transport of natural gas mixed with hydrogen is one of the primary approaches of hydrogen transportation. However, compared to pure natural gas (CH4), the explosion and combustion of natural gas mixed with hydrogen may lead to more severe consequences, and its reliability needs to be considered. Existing research of combustion and explosion using methane instead of natural gas have yet to be considered for application to real multi-component natural gas. To address this issue, real multi-component natural gas is configured, and the premixed flame and combustion characterization parameters of natural gas/H2/air are obtained through experiment. The chemical reaction kinetics of natural gas/H2/air mixtures are analyzed using Chemkin Pro software. These results prove that the laminar burning (LB) velocity varies between 0.33 m/s and 2.34 m/s by adding H2. The primitive reactions R1 (H2 + OH → H + H2O) and R3 (H + O2 → O + OH) predominantly contribute to enhancing the LB velocity. The Markstein lengths rang from −0.19 mm to −0.049 mm, most lewis numbers are less than 1, the flame thicknesses and critical destabilization radii are reduced. Additionally, hydrodynamic instability and thermal-diffusion instability are strengthened by adding the hydrogen. As for smaller hydrogen content, the average size of flame cell from about 8 mm program first rises and then falls cyclic fluctuations, fluctuation amplitude gradually reduces, fluctuation frequency accelerates. In larger hydrogen content, this fluctuation amplitude is reduced and the average size of flame cell decreases. In addition, H2 enhances the explosive strength of natural gas. Finally, methane instead of natural gas may exaggerate the velocity of laminar burning and exaggerate or weaken the ignition time delay of natural gas with different hydrogen contents. The current research might provide crucial information for the safe transport of hydrogen mixed with natural gas.

Large eddy simulation investigation of the effect of radiative heat transfer on the ignition progress in a model combustor

Radiation significantly influences turbulent combustion. This paper investigates the impact of radiative heat transfer on the ignition process in a multi-staged model combustor. The ignition process is simulated both without and with consideration of radiation. Large Eddy Simulations based on the Euler-Lagrange description of the liquid spray and the Dynamic Thickened Flame model coupled with a skeletal chemical reaction mechanism are employed. The Weighted Sum of Gray Gases method are employed to solve the spectral properties and the Discrete Ordinates method is employed to solve the radiative transfer equation. The results indicate that radiative heat transfer influences the flame structure during the ignition process. In the flame propagation phase, both the total heat transfer and the exit average temperature are higher, with the radiative heat transfer during ignition being less than 15% of the total heat transfer. During the kernel generation phase, radiative heat transfer leads to a 7.24% increase in the maximum temperature of the flame kernel, a 7.74% expansion of the flame surface area, and outward movement of the position of the maximum heat release rate. Additionally, the ignition delay time extends by 14.91%. In the flame propagation phase, the flame transfers heat to the mixed gas and droplets near the flame surface through radiation, promoting flame spread.

Exploring the first-stage ignition and model optimization in the comprehensive study of n-dodecane oxidation

n-Dodecane is commonly employed as a surrogate for investigating the combustion characteristics of jet and diesel fuels. Enhancing comprehension of its combustion behavior and developing accurate chemical kinetics models for simulating combustion is of paramount importance in engine development. This study focuses on a detailed exploration of n-dodecane oxidation kinetics under low-temperature conditions and presents a novel dataset concerning the first-stage ignition delay time. A broad spectrum of experimental conditions is investigated, encompassing a range of temperature (600 ∼ 1350 K), pressure (5 ∼ 20 atm), equivalence ratios (0.5 ∼ 1.0), and dilution gases (N2 and Ar). Additionally, combustion experiments in a pure oxygen environment are performed, contributing valuable data to existing research. To enhance the precision of the chemical reaction kinetics model of n-dodecane, this study integrates updated rate coefficients obtained from the latest theoretical calculations for specific reaction classes. The improved rate rule provides a more accurate reference for the construction of the chemical reaction kinetics model of long straight alkane. The resulting improved model excels in accurately predicting both the first-stage ignition delay time and the total ignition delay time under a wide range of operational conditions. Additionally, the model performance is rigorously evaluated through a comprehensive assessment against a diverse array of datasets gathered from various literature references. The results show that, in contrast to the previously proposed model, this enhanced model provides highly reliable predictions over a broad range of parameters.

Ignition energy, explosion flame propagation, and particle movement process of coal dust cloud in vertical Hartmann tube

To discuss the ignition energy, explosion flame propagation, and particle movement process of coal dust in vertical glass tube, experimental analysis and numerical simulation methods are used to carry out research. The experimental research results show that the optimal ignition delay time is 1 s, under this condition, the dust cloud near the ignition electrode has the highest turbulence, making it easier to ignite. When the dust cloud mass concentration is 2500 g/m3, the ignition energy is the smallest, resulting in the highest risk of explosion. The simulation results show that the propagation speed of flame is 4 m/s, due to the small amount of suspended dust used, the intensity of the explosion is not significant. The further away from the explosion source, the more energy is lost, the lower the temperature of the flame. Within 30∼50 ms after the ignition, the temperature near the explosion source rapidly increases, from 900 K to 1300 K. During the period of 0.2–0.5 s after dust injection, most particles move upwards along the tube. At 1 s after the dust injection, most particles move downwards and gather near the ignition electrode, forming a suspended dust cloud that is easily ignited, which is consistent with the optimal ignition delay time of 1 s obtained from the experiment.

Relative reactivity of methyl anisole isomers: An experimental and kinetic modelling study

Due to the current interest in biomass derived carbon neutral fuels and fuel additives for gasoline engines and to the growing need of understanding the fundamentals of gas phase combustion in the context of wildfires, this study investigates the combustion behavior of key components of biomass pyrolysis oils, namely the three methylanisole isomers (ortho-, meta- and para-methylanisole). Specifically, this study presents the first experimental ignition delay time measurements for such fuels using a shock tube and a rapid compression machine. Ignition experiments were carried out for stoichiometric fuel/air mixtures (φ = 1) at compressed pressure pc = 10 and 20 bar, covering a temperature range Tc = 880–1220 K. A kinetic model based on previous efforts in the area of oxygenated aromatic hydrocarbon fuels is proposed to reproduce and interpret the experimental findings, specifically focusing on capturing the observed different reactivity of the three isomers. To this aim, thermodynamic properties of primary intermediates and bond dissociation energies were calculated highlighting relevant differences originated from the relative position of the O–CH3 and –CH3 substituents. In addition, an isomerization pathway specific to the ortho isomer was theoretically investigated and found to motivate the observed higher reactivity with respect to the meta and para isomers

Heat and mass transfer mechanistic investigation of wall intervention on spray ignition characteristics under aviation piston engine-like conditions

The interaction between spray and walls significantly influences the mixture formation and ignition characteristics in aviation piston engines, primarily due to the dynamics of heat and mass transfer. To elucidate the wall’s influence on the impingement spray ignition process and reconcile discrepancies in the extant literature, we conducted a comprehensive suite of optical experiments encompassing free and impinging sprays with wide ambient temperature conditions (680 to 1200 K). Numerical simulations were utilized to dissect the flow field’s distribution patterns, as well as heat and mass transfer dynamics. Our investigation reveals that impinging sprays exhibit markedly shorter ignition delay times than free sprays under comparable conditions, with this divergence becoming more pronounced at lower ambient temperatures. Notably, impingement sprays are capable of auto-ignition at reduced ambient temperatures. The spray-wall interaction effect accelerates the accumulation of heat from the low-temperature reaction, facilitating swifter attainment of the threshold temperature for the high-temperature reaction. This is attributable to the generation of a higher quantity of high-temperature mixtures with a diminished local equivalence ratio. The disparity in the ignition delay times between impinging and free sprays is exacerbated by the elevated heat demand for the transition from low-temperature reaction to high-temperature reaction at lower ambient temperature conditions, predominantly driven by the exothermic nature of low-temperature reaction.

Impact of Intermediate Species in Simulating Oblique Detonation with Pre-Vaporized N-Decane/air Mixtures Substituting for Kerosene/Air Mixtures

ABSTRACT A renewed two-step n-decane mechanism is presented to improve reliable and robust simulation results, substituting for kerosene. This mechanism demonstrates that effective control of ignition delay time and heat release, based on the Chapman – Jouguet condition, enables successful simulation of oblique detonation waves. Chain reactions influence the overall reaction heat and explosion temperature, especially in simplified mechanisms with few steps. Therefore, carbon monoxide (CO) generation is crucial for balancing the overall reaction heat and reducing species sensitivity to pressure, a factor previously not discussed in simplified models. The computational time for solving detailed chemical kinetics increases exponentially with species count, driving the pursuit for further reduction in kinetic mechanism size. The sensitive interaction between density and temperature during the fuel/air mixture explosion process affects initiation zone formation and cellular structure. Analyzing the distribution of CO can provide insights into structural details. The study considers applying the Rankine – Hugoniot curve to confirm detonation speeds, temperatures, and kinetic energy changes induced by chemical reactions.

Spray combustion characteristics and soot formation potential of Nano-Al2O3 diesel at low ambient temperatures

Nanoparticle additives have the potential to enhance combustion efficiency and reduce emissions in liquid combustion processes. This study thoroughly investigates the spray evaporation, ignition, and combustion characteristics of nanoparticle/fuel blends, especially under challenging environmental conditions, to improve combustion efficiency and reduce emissions. Employing diffused background illumination, shadowgraph, Mie scattering, high-speed natural luminosity, and two-color method, the spray combustion dynamics of thermally stable nano-Al2O3/diesel (NAD) blends were examined within a constant volume combustion chamber. Diesel, a prevalent primary or auxiliary fuel, represents other highly volatile renewable fuels, while Al2O3, a significant component in combustion fly ash, is noted for its specific catalytic properties and ability to re-burn, eliminating organic toxic elements. The results indicated that NAD blends exhibit a faster evolution rate for both liquid and vapor sprays compared to pure diesel, attributed to the increased kinetic energy of breakup droplets. Under most experimental conditions, incorporation of nano-Al2O3 slightly reduced the ignition delay time due to enhanced heat transfer. Notably, nano-Al2O3 altered the ignition mechanism of the diesel spray, transitioning it from partially premixed to diffusion combustion and relocating the ignition point nearer to the injector. The combustion flame of NAD blends demonstrated increased luminosity, a shorter flame lift-off length, and variations in start-of-injection and total-injection-nozzle-lift-off. However, due to a high equivalence ratio mixture between the liquid phase spray and combustion region, the soot concentration in NAD blends was higher than that in diesel. Additionally, the elevated flame temperature in NAD blends significantly increased the soot concentration. Overall, nano-Al2O3 markedly enhances diesel combustion, especially in low ambient temperatures, suggesting its impressive potential for the high-efficiency and low-emission utilization of renewable fuels or the combustion of recycled waste solvents.

Hypergolic Ignition by Off-Center Binary Collision of Monoethanolamine-NaBH4 and Hydrogen Peroxide Droplets

Hypergolic ignition of H2O2 and MEA-NaBH4 by off-center collision of their droplets was experimentally studied, focusing on the characteristics and mechanism of droplet mixing, droplet heating and evaporation, and gas-phase ignition. The whole collision ignition process was divided into five stages, which were compared, respectively, with that of head-on collision. Under the condition of a slightly off-center collision (for cases where B &lt; 0.35), H2O2 droplets penetrate MEA-NaBH4 droplets after the collision and coalesce with it, but the internal H2O2 drop inside the MEA-NaBH4 droplet does not form a stable sphere. Instead, it rotates and expands inside the mixed droplet. With B increasing to 0.59, the droplets no longer coalesce after collision but separate away, forming satellite droplets. In such cases, multi-ignition mode is observed. When B increases to a certain extent, specifically, 0.85, a grazing collision is observed such that no mass transfer exists during the interaction of droplets, which leads to ignition failure. A theoretical model quantifying droplet swelling rate was established to calculate the volume change of the droplet. It was found that the swelling can be attributed to the flash boiling of superheated internal H2O2 fluid. Meanwhile, the ignition delay time was found to linearly decrease with B at various Wes until the extent where the chemical reaction takes over control, leading to an almost constant time delay defined as RDT. Additionally, the regime of ignition modes corresponding to different droplet mixing features is summarized in the We-B parametric space.

Numerical study on ignition start-up process of an underwater solid rocket motor across a wide depth range

Solid rocket motors have important applications in the propulsion of trans-media vehicles and underwater launched rockets. In this paper, the ignition start-up process of an underwater solid rocket motor across a wide depth range has been numerically studied. A novel multi-domain integrated model has been developed by combining the solid propellant ignition and combustion model with the volume of fluid multiphase model. This integrated model enables the coupled simulation of the propellant combustion and gas flow inside the motor, along with the gas jet evolution in the external water environment. The detailed flow field developments in the combustion chamber, nozzle, and wake field are carefully analyzed. The variation rules of the internal ballistics and thrust performance are also obtained. The effects of environmental medium and operating depth on the ignition start-up process are systematically discussed. The results show that the influence of the operating environment on the internal ballistic characteristics is primarily reflected in the initial period after the nozzle closure opens. The development of the gas jet in water lags significantly compared with that in air. As the water depth increases, the ignition delay time of the motor is shortened, and the morphology evolution of the gas jet is significantly compressed and accelerated. Furthermore, the necking and bulging of the jet boundary near the nozzle outlet and the consequent shock oscillations are intensified, resulting in stronger fluctuations in the wake pressure field and motor thrust.

Synergistic Enhancement on Ignition and Combustion Properties of Boron via Viton Core-Shell Coating.

The high gravimetric (58.74 kJ/g) and volumetric (137.45 kJ/cm3) heat values loaded in boron (B) offer significant potential for application in solid propellants and explosives. However, the high melting (2076 °C) and boiling (3927 °C) points of boron powder and the low melting point (450 °C) of oxidation products affect the energy performance and application of boron. Fluorine-containing polymers have high oxidation potential and excellent mechanical properties and can produce expectant gaseous products through the combustion reaction with boron oxide, but research examining the interaction between purified boron powder and fluoropolymers and the optimal selection of the fluoropolymer remains scarce. Herein, the binding energy between typical fluoropolymers [Viton, polyvinylidene fluoride, poly(vinylidene fluoride-co-chlorotrifluoroethylene), and vinylidene fluoride] and boron was calculated via molecular dynamics simulations, which shows that Viton is an appropriate candidate for coating boron powder. In the experiment, The Bw@Viton core-shell composites were prepared using Viton as the coating layer, and boron powder was pre-purified with acetonitrile. Its structure, thermal properties, ignition, and combustion characteristics were then characterized. The results revealed successful removal of the oxide layer, and the hydrophobicity was significantly improved after Viton coating. Purification and coating synergistically enhance the energy release of boron powder, and the composites demonstrated excellent thermal, ignition, and combustion performances. In particular, the heat of oxidation and heat of combustion were increased by 26.6 and 32.7%, respectively. The ignition delay time was reduced by 53.2% compared to raw boron. A prospective reaction mechanism between boron and Viton is thus proposed.

Iron powder particles as a clean and sustainable carrier: Investigating their impact on thermal output

The utilization of iron powder as a sustainable energy carrier, conducive to a carbon-free future, has garnered substantial attention due to its commendable attributes such as high energy density, widespread availability, and absence of emissions. To harness its potential optimally, a comprehensive understanding of the combustion behavior of iron powder and the development of corresponding combustion technologies are imperative. This study endeavors to investigate the influence of iron powder particle size, as well as the flow rate of air and iron powder, on the temperature at the exit of the ignition chamber. Experimental trials were conducted utilizing a metal cyclonic combustor (MC2) equipped with a system for feeding iron powder. The findings reveal that an increase in the diameter of iron particles corresponds to an elongation of the path from the ignition chamber to the outlet. Consequently, this elongation induces prolonged ignition delay time and burning duration. Notably, larger particles exhibit enhanced combustion efficiency in comparison to their smaller counterparts. The outcomes demonstrate that particles approximately 50 µm in size achieve an efficiency of 94%, as opposed to 72% for particles below 20 µm. Temperature measurements and spectrometric analysis expose a discernible relationship between particle size and temperature during combustion, elucidating that larger particles yield higher temperatures. Comprehending the intricate correlation between particle size and combustion behavior is crucial for optimizing combustion systems when utilizing iron powder as an energy carrier. By controlling particle size and combustion conditions, the efficiency and efficacy of iron powder combustion processes can be enhanced, thereby contributing to cleaner and more sustainable energy solutions. The implications of this study extend to the enhancement of burner system design and functionality, along with an overall improvement in combustion efficiency. These findings hold significance within the realm of combustion science, presenting opportunities for the development of more sustainable and environmentally friendly energy solutions. Implementing the insights derived from this research empowers researchers to harness the potential of iron powder as an energy carrier, thereby advancing progress toward a greener future through environmentally conscious combustion processes.

Experimental investigation on the combustion characteristics of electrolyte jets containing flame retardant tris (2-chloroethyl) phosphate

Abstract It is critical to well understand the combustion characteristics of the electrolytes inside lithium-ion batteries for safety concerns, particularly the electrolyte jet flames after thermal runaway. An electrolyte jet fire setup is developed in this study to investigate the combustion characteristics of electrolyte jets with the flame-retardant additive tris (2-chloroethyl) phosphate (TCEP) under high-temperature circumstances. Jet and ignition delay times and flammability are defined to characterize the flame-retardant effects. The fundamental parameters of self-extinguishing time and propagation rate are also measured for a comprehensive comparison. The experimental results show that the propagation of electrolyte flame at ambient temperature can be entirely stopped with 40 wt % of TCEP additives and 50 wt % can make the electrolyte nonflammable. Owing to the high boiling temperature and vaporization enthalpy of TCEP, more heat is required for the decomposition of electrolytes and TCEP mixtures, resulting in lower decomposition reaction rates and heat release rates. Thus, both the jet delay times and the ignition delay times significantly increase with the TCEP additives. Moreover, analyses on the spectrum of electrolyte jet flame reveal that the suppressing effects of TCEP on the combustion of electrolyte jets are operated by scavenging the OH radical and heat release.

Thermal decomposition and combustion of interior design materials

Research findings on the patterns of thermal decomposition and combustion are reported for widely used interior design materials. The experiments were conducted using a hardware and software system including a thermogravimetric analyzer (to record the characteristics of thermal decomposition), a gas analyzer (with H2, CH4, H2S, SO2, CO and CO2 sensors) and a high-speed camera (to record the characteristics of ignition and combustion). The temperature of the oxidizing medium ranged from 500 to 900°C to investigate the conditions of thermal decomposition initiation and sustained combustion. It was established that the highest concentrations of toxic emissions were typical of the combustion of polypropylene at a maximum temperature of the oxidizing medium (900°C). Wood showed the shortest ignition delay time and the longest duration of combustion. The experimental data were used for a physical problem statement and mathematical model of heat and mass transfer to explore the thermal decomposition and combustion of interior design materials in different rooms. A comparison of the experimental findings with the mathematical modeling results validates the developed model. The growth rates of carbon monoxide and carbon dioxide concentrations were determined for construction (wooden) and interior design (polymer) materials. The maximum concentrations of CO and CO2, and the minimum times taken to reach their threshold values corresponded to wood and polyvinyl chloride panels. This research provides a deeper insight into the thermal decomposition of a wide range of fuels and the formation of gaseous pyrolysis products of these fuels. The results obtained can be used to evaluate the toxicity of construction and interior design materials during compartment fires as well as to estimate the safe egress time and risks involved in the process. They can also serve as a database for the development and testing of mathematical models describing fire outbreaks and propagation in confined spaces.