1,3-Cyclopentadiene (c-C5H6) is one of the important intermediate species in the combustion of cyclic hydrocarbon fuels and the formation of aromatics. In this study, the thermodynamic properties and the chemical kinetics for the hydrogen abstraction and addition of c-C5H6 and the associated reactions on the C5H7 potential energy surface (PES) are investigated by high-level quantum chemistry calculations

For turbulent flames involving intense turbulence-chemistry interaction, quantifying the uncertainty originating from the parameters of chemical kinetics and physical models leads to a more rigorous assessment of the predictability of simulations. In the present work, a successive dimension reduction framework based on the active subspace (AS) method is formulated to efficiently quantify modeling uncertainties

A high pressure combustion chamber, housing a co-flow burner and a novel thermophoretic soot sampling system, was used to collect soot samples from methane-air diffusion flames at pressures from 5 bar to 30 bar. To have tractable diffusion flames with the same residence times, constant methane flow rate of 0.55 mg/s was maintained throughout the experiments. Soot aggregates were collected on 3 mm diameter

Cool flames propagating in autoignitive mixtures may be characterized as deflagrations or spontaneous ignition fronts depending on the relative importance of diffusion. In this paper, it is shown that, for certain thermochemical conditions in the negative temperature coefficient (NTC) regime, including at the Engine Combustion Network’s (ECN’s) baseline Spray A conditions, the cool flame products’

Knock remains one of the main limitations for increased internal combustion engine efficiency. Recent trends in light-duty vehicles towards downsized, boosted engines highlight the need to improve predictive knock models which incorporate contributing fuel chemistry and thermodynamic effects. Previous studies have shown the importance of end-gas thermodynamic conditions on knock onset and behavior

Blends of diesel and gasoline can be used to achieve certain desired ignition characteristics in advanced compression ignition engine concepts. In this work, ignition delay times were measured for two blends of diesel and gasoline in two shock tubes and in a rapid compression machine. These blends comprised of 50/50 and 25/75 volumetric% of diesel and gasoline, respectively. To ensure complete vaporization

This paper investigates experimentally and numerically pressure effects on soot production and radiative heat transfer in non-buoyant opposed-flow flames spreading over wires coated by Low Density PolyEthylene (LDPE). Experiments, conducted in parabolic flights, consider pressure levels ranging from 50.7 kPa to 121.6 kPa and an oxidizer flowing parallel to the wire's axis at a velocity of 150 mm/s

The sensitizing effect of cavities in the form of microbubbles on the shock initiation of a homogeneous liquid explosive is studied computationally. While the presence of voids in an explosive has long been known to induce so-called hot spots that greatly accelerate the global reaction rate, the ability to computationally resolve the details of the interaction of the shock front with heterogeneities

Numerical simulations of laminar premixed flames burning hydrogen and methane in spontaneous ignition mode are performed by harmonically exciting the reactants’ temperature at the domain inlet. The results are compared to an analytical model representing the same reactive flow configuration. The model provides a simplified but nevertheless accurate representation of reheat combustion taking place in

n-decane and n-dodecane are important components in transport fuels and detailed combustion mechanisms with a large number of species and reactions applicable to combustion over a wide range of conditions have been developed. DRGASA and DRGEPSA are usually capable of achieving compact skeletal mechanisms, but they are too expensive since species are deleted in a one-by-one manner. An improved sensitivity

Complex-chemistry direct numerical simulation (DNS) data obtained earlier from lean hydrogen-air flames associated with corrugated flame (case A), thin reaction zone (case B), and broken reaction zone (case C) regimes of turbulent burning are analysed to directly assess capabilities of the flamelet approach to predict mean concentrations of species in a premixed turbulent flame. The approach consists

In the present study, direct detonation initiation by a point energy source in a rich H2–NO2/N2O4–Ar mixture has been investigated using high-resolution one-dimensional numerical simulations performed with detailed chemistry. In particular, the effect of the 2-step energy release profile on the critical initiation energy and the dynamics of the failure process has been studied for the first time. Three

This article reports Large Eddy Simulation (LES) of 30 cm diameter methanol pool fires in order to investigate the effects of the burner boundary conditions on the pool dynamics. The numerical model involves state-of-the-art subgrid scale (SGS) sub-models for mixing, combustion and turbulence-radiation interaction with all the model constants computed dynamically. The non-adiabatic steady laminar flamelet

We study the variability in the ignition delay time, τign, of n-butanol due to uncertainty in the enthalpies and entropies of the fuel and fuel radicals. A stoichiometric mixture reacting adiabatically at constant volume is considered, over a range of initial temperatures (700–1000 K) and pressures (10–80 bar). We develop a thermodynamic class approach to account for the variability in the thermodynamic

Aliphatic polymers such as polyethylene or polypropylene are widely used in spite of their high flammability and forces the introduction of flame retardants (FR), e.g. metal phosphinates, into the polymers. These flame retardants usually act in the condensed phase or may influence the gas phase mechanism of combustion. However, the modes of action are not yet understood in detail and require increasing

Internal structure of extremely turbulent flames is investigated experimentally using simultaneous planar laser-induced fluorescence of formaldehyde molecule and hydroxyl radical as well as stereoscopic particle image velocimetry. The mean bulk flow velocity is changed from 5 to 35 m/s. The fuel-air equivalence ratio is 0.7 for all tested conditions. Three different turbulence generating mechanisms

A TRAnsparent cylindrical (TRAC) shock tube test section has been developed to explore the ignition structure behind reflected shockwaves via simultaneous lateral and endwall high-speed imaging using three fuel/oxidizer mixtures: 0.1% n-C7H16/1.10% O2/4.14% N2/94.66% Ar, 0.1% iC8H18/1.25% O2/4.69% N2/93.96% Ar, and 5% CH4/10% O2/85% CO2. During mild ignition, the first exothermic centers were located

Reliable ignition of reactant mixtures containing combustion products is important to the function of many practical combustion devices. Prior work has considered the influence of CO2 on ignition delay times and laminar flame speeds. This work examines the effects of dilution with CO2 on forced ignition and development of ignition kernels in CH4/air mixtures. Ignition kernels were initiated by a high

Flammable liquid fuels are potential candidates to replace hydrazine derivatives as hypergolic fuel and to promote ignition and combustion of high-density fuels as additives. Here 1,4-dicyclopropylbuta-1,3-diyne (DCPB) with high density (0.932 g/mL) and net heating value (42.47 MJ/kg) was synthesized by simple copper-catalyzed alkyne coupling reaction. As hypergolic fuel, DCPB has a short ignition

1-butene is an important intermediate in combustion of various hydrocarbon fuels and oxygenated biofuels (e.g., butanol). Understanding its oxidation chemistry can help improve ignition and combustion process in advanced engines and provide better emission control. This work addresses a discrepancy between experiments and simulations in 1-butene oxidation at low temperatures, wherein simulations with

Small-scale superadiabatic combustors with counter-flow heat exchange segments of finite length are studied using irreversible Arrhenius kinetics. First, the complete two-dimensional conservation equations for the gas phase and the solid walls separating the channels are investigated numerically. Next, a simplified one-dimensional model, also known as the narrow-channel approximation, is derived asymptotically

A surface evolution model is developed for the detonation propagation dynamics of the HMX-based conventional high explosive PBX 9501, which relates the normal surface speed Dn to its local surface curvature κ. Such surface evolution models are important for the understanding and modification of engineering design calculations for high explosive applications. We describe a series of unconfined PBX 9501

This work represents a detailed investigation of combustion and oxidation of methyl-3-hexenoate (CAS Number 2396-78-3), including experimental studies of combustion and oxidation characteristics, quantum chemistry calculations and kinetic model refinement. Following experiments have been carried out: Speciation measurements during oxidation in a jet-stirred reactor at 1 atm; chemical speciation measurements

The thermochemistry of gaseous Cellulose, Cellulosedinitrate and Cellulosetrinitrate basic cells, was calculated and is presented as numerical values and as NASA-7-term polynomials. The problem of representing and calculating thermochemical values of cell polymers is discussed.

The continuous development of a core C0 – C4 kinetic mechanism generally involves updating it using reliable kinetics and thermodynamics and may also involve the inclusion of missing reaction pathways to improve the integrity, prediction accuracy and applicability of the mechanism over a wider range of combustion relevant conditions. Accurate kinetic descriptions of the core mechanism can have a substantial

Spark-assisted compression ignition (SACI) has a promising potential to substantially improve engine's fuel efficiency. To this end, two exothermic stages in SACI combustion, flame propagation and auto-ignition, need to be well organized to increase control authority of bulk ignition timing especially in lean burn. In this study, three gasoline surrogates, namely EPRF, ETPRF and TPRF, formulated through

Diluent gases are used in practical industrial applications that involve flame propagation and detonation. In this study, we investigated the effect of diluent gases on end-gas autoignition and detonation development in a constant volume combustion chamber. High-speed Schlieren photography was employed to capture the flame–shock wave interaction and detonation evolution. Two reactants (hydrogen and

Laminar flame speed and autoignition properties of gasoline play key role in the overall performance of spark-ignition and modern engines. Since gasoline is a complex fuel containing hundreds of species, it is not feasible to model all components present in gasoline. Researchers tend to employ surrogates, comprising of few components, that mimic targeted physical and chemical properties of gasoline

A detailed study of ignition mechanisms in aeronautical burners is presented. Even in global lean conditions, liquid fuel injection leads to a strong stratification of the mixture and the whole range of equivalence ratio may be encountered in the burner. The observation of ignition sequences in a representative lab-scale combustion chamber, from both experiment and numerical simulation, reveals a variety

Catalytic combustion of natural gas has a growing interest to improve the flame stability and conversion efficiency in microcombustors. In automotive industry, the improvement of the efficiency of catalytic after-treatment systems are one solution to reduce drastically pollutant emissions. These devices present a honeycomb shape which consists in a grid of millimeter-scale narrow channels whose interior

The use of metal powder as a fuel in the high-energy materials (HEMs) for the propulsion is the most energy-efficient method to increase the specific impulse and improve the combustion characteristics in the chamber. HEMs typically contain aluminum powders with different particle size distribution. To improve the ignition characteristics of the Al-based HEMs, it is advisable to use nonmetals, metals

Microwave Assisted Spark Ignition (MAI) is a potential technology to improve lean combustion characteristics in spark ignition engines. This paper investigates the MAI performance with C2H2-Air spherical expanding flames in a Constant Volume Combustion Chamber (CVCC) system under ambient pressures from 0.1 to 0.6 MPa and equivalence ratios (φ) from 0.5 to 1.9. Results show that MAI greatly increases

Pyrolysis and low-temperature oxidation of dimethoxymethane (methylal, MeOCH2OMe) play an important role in the ignition of blended diesel fuels, but the underlying mechanisms are still debated. In these kinetic models, bimolecular hydrogen abstraction or unimolecular C–O bond fission are considered as the primary initial steps, while MeOCH2OMe isomerization is sometimes disregarded. In this work,

The oxidation of di-n-butyl-ether (DBE) was performed in a jet-stirred reactor (JSR) at 1 atm, 520 and 530 K, and from 480 to 670 K at 10 atm, at a residence time of 1 s, an equivalence ratio of 0.5, and an initial fuel concentration of 5000 ppm. Ignition experiments on DBE/air mixtures were also performed in a rapid compression machine (RCM) under stoichiometric conditions, 5 bar, and from 550 to

The effects of diluents including CO2, N2, and He on the lifted flame characteristics of laminar coflow propane jets are experimentally investigated by measuring their liftoff heights, HL, and visualizing flow fields with oil mist. For lifted flames at a specified diluent mole fraction, XD, HL increases in the order of He, N2, CO2 when the diluent is added to the coflow stream. However, the order of

This paper examines the effect of gradients in reactivity on the propagation of detonations in a relatively large ( ~ 1 m high) channel by studying detonation transmission from stoichiometric to fuel-lean mixtures of methane and air. The numerical model solves the fully compressible, reactive Navier–Stokes equations. The chemical heat release, mass diffusion and species-production rates are modeled

The effects of NO addition (1000, 2000 ppm) on the low-temperature oxidation of dimethyl ether (DME) and dimethoxymethane (DMM), as particular cases of oxymethylene ethers (OMEn) with n = 0 and 1, have been investigated in a plug-flow reactor at near-atmospheric pressure in a temperature range of 400–1000 K. An in-situ electron ionization molecular-beam mass spectrometer (EI-MBMS) was used to measure

Laser-induced fluorescence (LIF) technique has been widely applied in PAH measurement in sooting flames, but it is still a big challenge to quantitatively identify the specific PAH species due to the complexities of spectral characteristics and calibration method. In this study, we aimed at developing a spectral-resolved LIF analytic model that can obtain PAH mole fractions in flames. A comprehensive

Microgravity experiments of polyethylene (PE) droplet combustion were conducted by a 3.6-s drop tower with the gravity level of 10−3~10−4 g to investigate the burning behaviors and fire hazards of molten thermoplastics in the spacecraft. Pre-ignited droplets with a diameter of about 3 mm were continually generated and detached from burning PE tubes. Once the drop capsule started free-fall, droplets

Engineered smouldering applications require self-sustaining conditions where the fuel is consumed without any addition of energy beyond ignition. In practical applications, it is preferred to create scenarios that are robust (i.e., far from extinction). In this work, smouldering column experiments were conducted, spanning conditions from robust self-sustaining through weak self-sustaining and to extinction

Modern societies require cleaner and more efficient internal combustion engines. Low-temperature combustion (LTC) has been proved to be a good step toward this goal. This study aims at investigating the promoting effect of a cetane booster additive named 2-ethylhexyl nitrate (EHN) on the reactivity of a low-octane gasoline at LTC-relevant conditions. Rapid compression machine experiments were conducted

Smoke release in the limited volume of a spaceship poses a major threat to the life of astronauts in long range exploration missions. If the absence of buoyant flows fundamentally affects combustion mechanisms, the possibility of atmospheric design in spacecraft environment provides a new leverage, not usually available on Earth. Investigating a non-buoyant flame spreading over the polyethylene coating

In this work, three different combustion modes were obviously observed under different oxygen concentrations, including normal combustion without end-gas autoignition, end-gas autoignition without detonation, and end-gas autoignition with developing detonation for gasoline. The results indicate that the intensities of pressure and pressure oscillation depend on the combustion mode. Compared with hydrogen

The objective of this study was to determine the combustion mechanism of cellulose paper impregnated with Mg(NO3)2, Ni(NO3)2, glycine solutions, and their different combinations. It was established that the combustion mechanism changes as a function of the impregnated media composition. In the Mg(NO3)2-cellulose system, Mg2+ ions strongly catalyze cellulose pyrolysis; hence no atmospheric oxygen is

The sooting propensity of a fuel is closely coupled with the fuel composition and chemistry. A detailed understanding of their effects is, therefore, needed to develop next-generation fuels which can minimize particulate emissions. With this overarching goal, the present work numerically investigates the effects of fuel composition and octane sensitivity (S) on polycyclic aromatic hydrocarbons (PAH)

Recently, reconstruction integrating view registration (RIVR) has been demonstrated as an improved method to significantly enhance the accuracy of three-dimensional (3D) measurements in nonreactive flows. This work extended the RIVR method to 3D measurements of highly turbulent reactive flows with two specific goals. The first goal was to examine if the RIVR method can be effectively applied to highly

The kinetic parameters of condensed phase global reaction are required to calculate temporal and energetic characteristics of the ignition and combustion of energetic materials (EMs). The heating rate of EM in these processes exceeds 1000 K/s and therefore the kinetic data obtained via using classical thermal analysis methods with heating rate of 1–50 K/min may not provide the processes adequate description

Homogeneous Charge Compression Ignition (HCCI) is a promising advanced combustion technology with high thermal efficiencies and low exhaust emissions, and thus, is a potential solution for future transportation applications. Quasi-dimensional multi-zone models with detailed chemical kinetics have reasonable computational cost and high accuracy for HCCI studies. However, they require significant tuning

We pursued a quantitative comparison of the continuum and mesoscale simulations of metal particle reactions in a condensed explosive. The continuum or homogeneous approximation assumed a single combustible mixture; contrastingly, in the present heterogeneous treatment of a mixture, aluminum and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane were considered independent reactive granules of micron size with

The coexistence of two regimes of aluminum (Al) particle combustion is discussed. A slower regime occurs at a low energy accommodation coefficient (EAC) and is usually observed in Al combustion experiments. A faster regime at high EAC is also possible. The combustion enhancement observed for pre-treated Al particles can be interpreted as a switch from the slower combustion regime to the faster regime

The paper analyses numerically the scenarios of ignition kernels formation in the shock tube in the intermediate temperature range. Three modes of mild ignition are distinguished among which are: ignition related to the shear heating in the developed boundary layer, ignition due to the shear heating in the recirculation zone behind the reflected shock and ignition in the central region of the tube

Conventional ammonium perchlorate (AP) based solid propellant system has been used in rocket boosters and most tactile missiles. But the toxic chloride emissions from the combustion of AP during the rocket launch increase the air pollution by 1%. For the conversion of conventional AP based propellant into Green propellant there approaches can be used. These are scavenging propellants, Neutralizing

The main objective of this work is to analyze the effects of gas radiative property models on the radiative outputs and flame structure in a 1 m diameter methanol pool fire. Large Eddy Simulation (LES) are run with the non-adiabatic steady laminar flamelet (SLF)/presumed filtered density function (FDF) model to close subgrid-scale (SGS) turbulence-chemistry and turbulence-radiation emission interactions

An experimental and numerical investigation of the thermochemical structure of piloted premixed jet flames was conducted, encompassing laser absorption tomography measurements and large-eddy simulations (LES). The investigation was performed holding laminar flame speed, jet Reynolds number, and surrounding flow conditions constant while considering three different fuel types, namely an alkene, a normal

Laminar diffusion flames present an elementary configuration for investigating soot formation and validating kinetic models before these are transferred to turbulent combustors. In the present article, we present a joint experimental and modelling investigation of soot formation in a laminar co-flow burner. The diffusion flames are analysed with the aid of laser diagnostic techniques, including elastic

All models invoke assumptions that result in model errors. The objective of model form uncertainty quantification is to translate these assumptions into mathematical statements of uncertainty. If each assumption in a model can be isolated, then the uncertainties associated with each assumption can be independently assessed. In situations where a series of assumptions leads to a hierarchy of models

The flame expansion process (“light-round”) during the ignition transient in annular combustors depends on a number of parameters such as equivalence ratio (and hence laminar burning velocity, SL, of the mixture), turbulent intensity, mean flow magnitude and direction, geometry, and spark location. Here, an experimental study on a fully premixed, swirled, bluff body stabilised annular combustor is

COS is the most abundant sulfur containing compound in the atmosphere that could cause serious adverse effects on human health and environment. Understanding the oxidation mechanism of COS is with great significance in controlling and utilization reduced sulfur (CS2 and COS). In this study, density function theory (DFT) and multi-reference configuration interaction with Davidson correction (MRCI+Q)

In most scenarios where detonations in fuel–air mixtures can present a hazard, such as in industrial accidents, or where they can be used for practical purposes, like detonative propulsion applications, the mixture is essentially non-uniform. For industrial accidents, it is important to understand what fraction of the mixture can detonate in order to limit the consequences of an explosion event by

A high-pressure shock tube was used to study ignition delay times (IDT) of CH4/O2/Ar and natural gas/O2/Ar mixtures behind reflected shock waves. Reaction progress was monitored using sidewall pressure and direct laser absorption diagnostics of CH4 near 3.175 µm and ethylene near 10.532 µm. Stoichiometric, fuel-rich and fuel-lean mixtures of CH4/O2, highly dilute in argon, were studied over a temperature