Firebrands are a significant source leading to structures ignited and lost in large outdoor fires, such as Wildland-Urban Interface (WUI) fires, a large international problem, and urban fires, common in Japan. Sadly, hardly any information is available with regard to firebrand production from burning structures or actual large outdoor fires in general. To this end, an experimental database is being

Pulverized bituminous coal was burned in a 10W externally heated entrained flow furnace under air-combustion and three oxy-combustion inlet oxygen conditions (28, 32, and 36%). Experiments were designed to produce flames with practically relevant stoichiometric ratios (SR=1.2-1.4) and constant residence times (2.3s). Size-classified fly ash samples were collected, and measurements focused on the soot

An experimental ignition delay time study for the promising biofuel 2-methyl furan (2MF) was performed at equivalence ratios of 0.5, 1.0 and 2.0 for mixtures of 1% fuel in argon in the temperature range 1200-1800 K at atmospheric pressure. Laminar burning velocities were determined using the heat-flux method for mixtures of 2MF in air at equivalence ratios of 0.55-1.65, initial temperatures of 298-398

The oxidation of two blends, benzene/n-decane and toluene/n-decane, was studied in a jet-stirred reactor with gas chromatography analysis (temperatures from 500 to 1100 K, atmospheric pressure, stoichiometric mixtures). The studied hydrocarbon mixtures contained 75% of aromatics in order to highlight the chemistry of the low-temperature oxidation of these two aromatic compounds which have a very low

While it is well documented iron oxide can reduce soot through burnout in the oxidative regions of flames, it may also impact molecular growth and particle inception. The role of Fe2O3 nanoparticles in mass growth of soot from 1-methylnapthalene (1-MN) was studied in a dual-zone, high-temperature flow reactor. An iron substituted, dendrimer template was oxidized in the first zone to generate ~5 nm

The formation of hydroperoxides postulated in all the kinetic models for the low temperature oxidation of alkanes have been experimentally proved thanks to a new type of apparatus associating a quartz jet-stirred reactor through a molecular-beam sampling system to a reflectron time-of-flight mass spectrometer combined with tunable synchrotron vacuum ultraviolet photoionization. This apparatus has been

The modeling of the low temperature oxidation of large saturated methyl esters really representative of those found in biodiesel fuels has been investigated. Models have been developed for these species and then detailed kinetic mechanisms have been automatically generated using a new extended version of software EXGAS, which includes reactions specific to the chemistry of esters. A model generated

An improved chemical kinetic model for the toluene oxidation based on experimental data obtained in a premixed laminar low-pressure flame with vacuum ultraviolet (VUV) photoionization and molecular beam mass spectrometry (MBMS) techniques has been proposed. The present mechanism consists of 273 species up to chrysene and 1740 reactions. The rate constants of reactions of toluene decomposition, reaction

We demonstrate that stable and relatively unreactive "environmentally persistent free radicals (PFRs)" can be readily formed in the post-flame and cool-zone regions of combustion systems and other thermal processes. These resonance-stabilized radicals, including semiquinones, phenoxyls, and cyclopentadienyls, can be formed by the thermal decomposition of molecular precursors including catechols, hydroquinones

A detailed chemical kinetic mechanism is developed for the gas-phase combustion of a liquid monopropellant, which is a blend of propylene-glycol-dinitrate, dibutyl-sebacate, and 2-nitro-diphenylamine (Otto Fuel II). The combustor is modeled as a steady-state burner-stabilized flame. The simulations reveal that not all of the dibutyl-sebacate is consumed in the flame, with approximately 5% persisting

This present study explores possible stabilization mechanisms in flickering, sooting, ethylene flames burning in varying density coflow and exposed to different levels of an upward gradient of the square of the magnetic flux density (∇(B2)). In normal gravity, flame flickering defines a natural large scale and low frequency flame oscillation that is induced by a so called modified Kelvin–Helmholtz

To control the ignition and stabilization location of the second stage flame in a sequential combustor, nanosecond repetitively pulsed discharges (NRPD) were generated between three cylindrical electrodes. The NRPD were obtained by repetitively applying high voltage pulses to the central electrode. At operating conditions where the sequential flame was nearly quenched or weakly anchored, it was possible

Toward a precise modeling for wall chemical effects in flame-wall interactions, radical adsorption on different wall surfaces are directly evaluated through a newly-developed molecular beam scattering technique using a non-equilibrium plasma–driven beam source as well as an ultra-high vacuum chamber. Firstly, sensitivities of adsorption rates for each radical species to the wall chemical effect are

This paper presents a large eddy simulation (LES) of a generic sequential combustor that was operated at atmospheric pressure and that features a thermoacoustic instability at 145 Hz. The full test rig consisting of a first stage plenum, burner and combustion chamber, of an air dilution section and of a sequential stage combustor was modeled. A compressible reactive 3-D LES was performed with semi-detailed

We present an experimental study on characterizing the dynamic behavior of flow velocity field during combustion noise from the viewpoints of statistical complexity and complex-network theory, involving the detection of a precursor of blowout. The multiscale complexity-entropy causality plane clearly shows the possible presence of two dynamics, (1) stochastic dynamics in the injector rim region and

Combustion instabilities are one of the major challenges in developing and operating propulsion and power generating gas-turbine engines. More specifically, techniques for managing the increasingly stringent emissions regulations and efficiency demands have often given rise to thermo-acoustic instabilities, particularly for annular combustors operating in a lean premixed mode. In this paper, we combine

Combustion pyrolysis of natural gas is a promising process for high value-added chemicals such as alkynes and olefins. This work introduces recent experimental and computational studies of a 2.5 kTA (thousand metric ton per year) two-stage combustion pyrolysis unit, and focuses on the role of mixing on pyrolysis. Temperature, pressure, and gas composition measurements were experimentally obtained at

Higher-value chemicals can be produced from methane with small exergy losses by partial oxidation if the chemical conversion proceeds in an internal combustion engine (ICE) as a polygeneration process (Gossler and Deutschmann, 2015). Kinetics models are not sufficiently validated for the very fuel-rich and high-pressure conditions relevant for this process. Therefore, ignition delay times of fuel-rich

Porous media burners (PMBs) enable enhanced combustion performance by internally recirculating heat released from the combustion products upstream to the reactants via an inert solid matrix. Compared to conventional free-flame systems, PMBs are characterized by higher burning velocities, extended flammability, and lower emissions of NOx. Current PMB implementations utilize a two-zone concept in which

This study describes the performance and stability characteristics of a Hybrid Solar Receiver Combustor operated in the Moderate or Intense Low oxygen Dilution (MILD) combustion regime, in which the functions of a solar receiver and a combustor are integrated into a single device. The device was built and tested at a nominal capacity of 20 kWth for both the combustion-only (MILD and conventional combustion)

In this work, the functionalized form of a highly-conductive, porous, three-dimensional graphene foam (F-GF) was used to enhance the flame speed of a solid propellant, nitrocellulose (NC). The graphene foam (GF) micro-structures, synthesized by the chemical vapor deposition (CVD) technique, were coated with a transition metal oxide (TMO), manganese dioxide (MnO2), using a hydrothermal approach. Average

Temperature profiles and effluent concentrations were measured during combustion of aqueous urea and ammonium nitrate at pressures of 1–15 MPa. Pollutant levels decreased, while the combustion temperature showed a non-monotonic change with increasing pressure. Experimental temperature profiles were applied in kinetic gas-phase simulations, and resulting species concentrations were in good agreement

Wall chemical effect on DME/air weak flames (Uin = 1.5 cm/s, ϕ = 0.85) was investigated using a micro flow reactor with a streamwise temperature gradient experimentally. The quartz channel used in this study has a rectangular cross-section of 1.5 × 5 mm, which offers a good optical access for the planar laser-induced fluorescence (PLIF) measurement. The walls can be replaced for examining wall chemical

Inserting porous medium into micro-combustors is able to further enhance heat recirculation, thus favoring the extension of flame stability limits. Both experimental and numerical studies have shown that extended standing-wave combustion regimes exist in micro-combustors filled with porous medium. However, the underlying mechanism that dictates the critical flame stability limits is not well understood

A burner design with integrated electrodes was used to couple a gliding arc (GA) discharge to a high-power and large-scale turbulent flame for flame stabilization. Simultaneous OH and CH2O planar laser-induced fluorescence (PLIF) and CH PLIF measurements were conducted to visualize instantaneous structures of the GA-assisted flame. Six different regions of the GA-assisted flame were resolved by the

Microwave Discharge Igniter (MDI) is an ignition device that operates based on the microwave resonance phenomenon. Receiving the microwave pulses from a semiconductor generator, the MDI generates non-thermal plasma to enhance the combustion. A new igniter plug consists of multiple MDIs in its structure is developed to achieve leaner operation limit as well as higher dilution limit, which are essential

This study evaluates the ignition performance of a new miniaturised igniter that operates based on microwave resonance phenomenon. This igniter, named Flat Panel Igniter (FPI), consists of a flat ceramic panel with a metal strip inlay on the top surface acting as a resonance cavity. The FPI and a standard spark plug is used to ignite air–propane mixtures at various equivalence ratio inside a constant

Ignition of fuel-lean premixed methane-air flow was investigated using single-pulse laser-induced spark (SPLIS) and dual-pulse laser-induced spark (DPLIS). Ignition enhancement was quantified with ignition probability in flow speeds and equivalence ratios of 3.75 m/s–12.5 m/s and 0.53–0.57, respectively. The range of total laser pulse energy per ignition event was 20–30 mJ. For DPLIS, the energy per

The present study explores the chemical kinetics of low temperature oxidation and pyrolysis of pentane/O2/He mixtures in a nanosecond repetitively-pulsed DBD discharge. Time-dependent TDLAS measurements and steady state GC sampling are conducted to quantify species evolution in a plasma discharge. An improved kinetic model of plasma assisted combustion and pyrolysis of pentane is developed with updated

A new experimental setup coupled a dielectric barrier discharge flow reactor with a molecular beam mass spectrometer (MBMS) was developed for detailed species diagnostics on plasma assisted oxidation and pyrolysis system. The mixture of methane and oxygen diluted by argon was selected as the feed gas. The MBMS technique with photoionization or electron ionization provided access to not only stable

Nanosecond pulsed high frequency discharges (NPHFD) have attracted interest as a means of enhancing ignition probability and ignition kernel growth rates. Previous studies have shown that increasing the pulse repetition frequency (PRF) of a NPHFD burst can result in enhanced probability of ignition relative to lower values of PRF. The cause of this enhanced ignition probability is not well understood

This work aims to provide a better understanding of the cumulative effect of successive nanosecond repetitively pulsed (NRP) discharges on the ignition process. Fast chemiluminescence imaging of both the post-discharge and the following flame was used to analyze the ignition of a lean propane/air mixture (ϕ = 0.7) by a train of 82 NRP discharges at a pulse repetition frequency (PRF) of 30 kHz, in comparison

Ignition enhancement using a hybrid repetitive nanosecond and DC discharge is studied in CH4/O2/He mixtures at atmospheric pressure by using a hybrid ZDPlasKin-CHEMKIN method. Special attention is placed on the control of vibrational and electronic excitations of methane and oxygen using different electric field strengths. A plasma-ignition kinetic mechanism incorporating the reactions involving both

Recent investigations suggested that the primary influence of an electric field on a flame is flow modification caused by ionic wind, and that negative ions produced by the electron impact attachment should play a key role in the bi-directional ionic wind. In order to prove this hypothesis in electric fields parallel to the propagating flames, we designed a coflow experiment with laminar lifted flames

In this paper, we demonstrate CO2 thermochemical reduction to CO in a La0.9Ca0.1FeO3-δ oxygen ion transport membrane reactor. For process intensification, we also show that methane can be used on the sweep side, producing two streams: a CO stream from CO2 reduction on the feed side, and a syngas stream on the other. We show that surface reactions are the rate-limiting steps for fuel-assisted CO2 reduction

The self-sustained combustion of carbon monoxide (CO) has been studied over the CuCe0.75Zr0.25Oδ catalyst by sol–gel method, and compared with the CuCe0.75Zr0.25Oδ(H) and Ce0.75Zr0.25Oδ to investigate sensitivity of different active sites, such as dispersed CuO, Cu–Ce and Ce–Zr solid solution. The CuCe0.75Zr0.25Oδ(H) is obtained via CuCe0.75Zr0.25Oδ sonicated in nitric acid to remove surficial CuO

In this work, CuO-TiO2 nanoparticles with different CuO mass contents of 2%, 8%, 12%, and 20% are synthesized by flame spray pyrolysis (FSP) method and applied to catalytic combustion of lean CO. The nano-catalyst is characterized by N2-physisorption isotherms, X-ray diffraction (XRD), transmission electron microscopy (TEM), H2-TPR (temperature-programmed reduction) and X-ray photoelectron spectroscopy

Three-dimensional direct numerical simulations of turbulent catalytic and gas-phase H2/air combustion at a fuel-lean equivalence ratio φ=0.18 were performed in platinum-coated planar channels at two industrially-relevant flow conditions (inlet friction Reynolds numbers Reτ= 182 and 385) using detailed hetero-/homogeneous chemical reaction mechanisms. The preferential diffusion of hydrogen and oxygen

H2-rich gas production from CH4 at mild temperature (673 K), was achieved in a single step without introducing a separate oxygen stream. This was conducted in a plasma-assisted packed bed reactor in the presence of Ni-based catalysts doped on an active support, i.e. Fe2O3. Among the tested materials, NiO/Fe2O3 was found to be very promising and its excellent catalytic properties seemed to be induced

Platinum-decorated functionalized graphene sheet (Pt@FGS) is a promising nanoparticle additive for catalytic fuel combustion. In this study, four cases involving pure methane oxidation and methane oxidation in the presence of various Pt/graphene-based nanoparticle catalysts are investigated using the reactive force field molecular dynamics (ReaxFF MD) simulations to reveal catalytic mechanisms and

The heterogeneous and homogeneous combustion of fuel-lean CH4/O2/N2 mixtures over PdO was investigated experimentally and numerically at equivalence ratios φ = 0.27–0.44, pressures 1–12 bar and surface temperatures 710–1075 K. In situ Raman measurements of major gas-phase species concentrations across the boundary layer of a channel-flow catalytic reactor assessed the heterogeneous reactivity, while

In this study, we investigated the redox reaction between a hydrocarbon (HC) and adsorbed NOx over CuPtBa/Al2O3 lean NOx trap (LNT) catalyst. Experimental characterizations included temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), in situ diffuse reflectance Fourier transform spectroscopy (in situ DRIFTs) and Raman spectroscopy. Density functional theory (DFT) calculations

Single (α-Fe2O3 and Fe3O4) and composite iron oxides (α-Fe2O3@Fe3O4) have been prepared by chemical vapor deposition for clean combustion. The physio-chemical properties of the obtained thin films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and the redox properties via temperature programmed reduction analyses. The catalytic performance for

Soot production processes and their interaction with the swirling flow field were studied experimentally in turbulent spray flames in a model gas turbine combustor. Two Jet A-1/air spray flames with two different air flow rates both with constant fuel flow corresponding to a thermal power of 10 kW were stabilized in the combustor with a swirl number of 0.55. Soot measurements were collected using auto-compensating

Expected stringent legislation on particulate matter (PM) emission by gas turbine combustors is currently motivating considerable efforts to better understand, model and predict soot formation. This complex phenomenon is very difficult to study in detail with experiment, and numerical simulation is an essential complementary tool. Considering that the chemistry of soot particles strongly depends on

The mechanisms of transient formation and oxidation of soot in an aero-engine model combustor at elevated pressure are studied for the first time using a combination of high-speed simultaneous stereo-PIV and OH-PLIF and results from a recent detailed LES. A combined analysis of experiment and LES shows that the highly transient and intermittent evolution of soot in this combustor is governed by an

The design of new low-emission systems requires the development of models providing an accurate prediction of soot production for a small computational cost. In this work, a three-equation model is developed based on mono-disperse closure of the source terms from a sectional method. In addition, a post-processing technique to estimate the particles size distribution (PSD) from global quantities is

This paper describes NOx measurements from reacting jets in crossflow (RJICF). This work is motivated by interest in axial staging of combustion as a means of reducing NOx emissions at high flame temperatures (>1900 K), where thermal NOx production rates are high. In this approach, the majority of the fuel is burned in a conventional lean-premixed flame, but additional fuel is injected from the combustor

This paper presents a systematic experimental study of the relative contributions of various near-wall flame dynamics to exhaust CO emissions. Exhaust carbon monoxide (CO) emissions and quenching distance measurements are reported for a laminar forced premixed propane flame undergoing flame-wall interaction. A vehicle-certification grade emissions bench was used to measure exhaust CO emissions at two

The present article investigates the correlation between flame macrostructures and thermoacoustic combustion instabilities in stratified swirling flames. Experiments are carried out in a laboratory scale longitudinal test rig equipped with the Beihang Axial Swirler Independently-Stratified (BASIS) burner, a novel double-swirled combustion system developed by adapting an industrial lean premixed prevaporized

Models based on the linearized G-equation for the response of a premixed flame to acoustic perturbations often rely on a convective velocity model, where a convective wave generates local perturbations of flame shape and surface. The present study scrutinizes the origin and nature of such convective perturbations in flow-flame-acoustic interactions. Given that vortical structures are convected flow

A new mechanism of thermo-acoustic destabilization of combustors powered by burning droplets is investigated. Acoustic induced heat release disturbances are found to be driven by oscillations of droplet lifetime during the final stage of the droplet combustion before their extinction. The mechanism is the following. Synchronized acoustic disturbances alter the droplet evaporation rate and modify their

This paper shows the importance of considering the thermal state of a combustor to investigate or predict its thermoacoustic stability. This aspect is often neglected or regarded as less important than the effect of the operating parameters, such as thermal power or equivalence ratio, but under certain circumstances it can have a dramatic influence on the development of the instabilities. The paper

Nonlinear coupling between azimuthal and axisymmetric modes in annular combustors is studied analytically. Based on the thermoacoustic wave equation, a model featuring three nonlinearly coupled oscillators is derived. Two oscillators represent the dynamics of an azimuthal mode, and the third accounts for the axisymmetric mode. A slow-time system for the evolution of the mode amplitudes and phases is

A joint experimental and computational study of thermoacoustic instabilities in a model swirl-stabilised combustor is presented. This paper aims to deliver a better characterisation of such instabilities through the examination of measurements in conjunction with the numerical results obtained via Large Eddy Simulation (LES). The experimental configuration features a cylindrical combustion chamber

Open-loop forcing is known to be an effective strategy for controlling self-excited thermoacoustic oscillations, but the details of this synchronization process have yet to be comprehensively explored. In this study, we experimentally examine the synchronization dynamics of a laminar conical premixed flame in a tube combustor subjected to periodic acoustic forcing. We compare the response of this forced

In this paper, the dynamics and thermoacoustic stability of a laminar premixed flame are analyzed using a linearized reactive flow (LRF) solver. The LRF solver is based on linearized compressible Navier-Stokes and reacting species transport equations and thereby includes a model for the dynamic response of the flame to flow perturbations in an inherent manner. The equations are discretized using the

The flame response to upstream velocity perturbations is properly described by a Finite Impulse Response (FIR) model. When combining an FIR model with acoustic tools to predict thermoacoustic modal growth rates, uncertainties contained in the FIR model coefficients would propagate through the acoustic model, inducing deviations of the modal growth rate from its nominal value. Therefore, an associated