Most computational fluid dynamics simulations of practical combustion applications employ operator-splitting schemes, where chemistry and transport are separated and integrated with distinct numerical methods. The changes in composition due to chemistry are evaluated by solving ordinary differential equations (ODE) in each cell of the computational domain, which typically dominates the computational

We have developed a continuum modeling approach, grounded in classical physical chemistry, based on the following assumptions: (1) That the states in the material can be represented by local stationary averages of the pressure (stress), temperature, and mass fractions computed from atomistic simulation, (2) and that the mixture has well-defined molecular components, each with a complete equation of

Carbon monoxide (CO), as one of the major gaseous product in the oxy-fuel combustion boiler, is found to exert great influence on nitric oxide (NO)-char reactions. Unfortunately, the detailed mechanism of CO enhancement still remains obscure. In this work, starting from the armchair model with embedded nitrogen, we propose some updated mechanisms with details at the molecular level that can describe

A chemistry reduction approach based on machine learning is proposed and applied to direct numerical simulation (DNS) of a turbulent non-premixed syngas oxy-flame interacting with a cooled wall. The training and the subsequent application of artificial neural networks (ANNs) rely on the processing of ‘thermochemical vectors’ composed of species mass fractions and temperature (ANN input), to predict

The present study primarily concerns itself to validate the novel technique presented by Vijay and Ramakrishna (2020) to predict the initial temperature sensitivity of non-aluminized composite propellant compositions. The technique is used here to predict the combustion characteristics of non-aluminized propellants with 86% loading. The coarse to fine ratio of 1:1 and 4:1 for the AP particles was used

The hydrazine-derived ionic liquid 2-hydroxyethylhydrazinium nitrate (HEHN) is a promising fuel component of green monopropellants. For successful implementation of these propellants, it is necessary to understand the kinetics and mechanism of HEHN decomposition, but the available data are scarce. The objective of the present work was to investigate the kinetics of HEHN thermal decomposition using

Theoretical and experimental works have been carried out to clarify the effect of core material on the extinction characteristics of the flame spreading over electric wires. Additionally, an attempt has been made to explain previous experimental results (Takahashi et al., 2013 [1]) which found that Limiting Oxygen Concentration (LOC) of copper (Cu) wire is higher than that of nickel-chrome (NiCr) wire

The sensitivities of turbulent combustion simulations to chemical kinetic parameters can be analyzed to understand the controlling reactions in turbulent flames and to quantify the uncertainties in simulations. However, computing the sensitivity of turbulent combustion simulations to a large number of kinetic parameters is still challenging. A promising approach is to estimate the sensitivity from

A synergistic effect on low-temperature autoignition reactivity of blending two high-octane compounds, i.e. cyclopentane and diisobutylene, was observed in engine experiments and ignition delay time measurements at 700–880 K and up to 25 bar with a rapid compression machine. Results show that the low-temperature ignition delay and RON of a cyclopentane-diisobutylene blend are inferior to those of its

Pressurized oxy-fuel combustion is considered to be a new generation of oxy-fuel combustion technology owing to its low emission and high efficiency. In this study, the ignition delay times (IDTs) for propane under O2/CO2/Ar atmospheres were measured in a shock tube at varying pressures and equivalence ratios. A chemical kinetic model (OXYMECH 2.0) for pressurized oxy-fuel combustion was developed

Flameless combustion, also called MILD combustion (Moderate or Intense Low Oxygen Dilution), is a technology that reduces NOx emissions and improves combustion efficiency. Appropriate turbulence-chemistry interaction models are needed to address this combustion regime via computational modelling. Following a similar analysis to that used in the Extended EDC model (E-EDC), the purpose of the present

This study investigated the burning characteristics of PMMA with varied stretch rates under stagnation-point diffusion flames both theoretically and experimentally, focusing on the manner in which the surface energy balance and heat losses affected burning rate with varied stretch rates. The burning rate versus stretch rate was firstly investigated by introducing a modified Spalding B number, where

Laminar flame speeds of formic acid were measured at equivalence ratios of 0.4–1.6, initial temperature of 423–453 K and atmospheric pressure. Chemical kinetic models (Glarborg model and AramcoMech 3.0) were validated against the present experimental data. Deep kinetic insight was investigated using the present models. In addition, detailed analysis was carried out according to transport, thermal and

This study reports an experimental and numerical investigation of droplet combustion of a miscible n-heptane/iso-octane mixture at a fixed mixture fraction (equi-volume) for initial diameters (Do) in the range of 0.8 mm ≤ Do < 5 mm. This range encompasses burning transitions from hot flame (HF) combustion to the cool flame (CF) regime where radiative extinction can occur. The simulations assume spherically

To reduce the size inconvenience of airbag systems employed in human-body protection devices while maintaining comparable gas generation performance, a new family of gas-generating energetic composites are proposed mixing Al/CuO nanothermite with copper complex (Cu(NH3)4(NO3)2) known for its propensity to generate gases (0.03 mol/g) such as N2, O2, N2O through exothermic chemical decomposition (300

For decades, experimental investigations of turbulent droplet evaporation have generally followed one of two distinct paths: wind tunnel experiments, which generate significant mean flow but low turbulence intensity, and stirred chamber configurations, which yield the opposite characteristics. The present study bridges the gap between these two established techniques by modifying a fan-stirred spherical

In order to gain insight into aluminum agglomeration behaviors and agglomeration processes, the aluminized fuel-rich propellants in solid fuel ramjet are investigated by using sampling method followed by scanning electron microscopy and laser scattering experimental technique on the small-scale combustion experimental system and connected-pipe experimental system. It is observed that the aluminum particles

Pyrolysis of 1,2,4-trimethylcyclohexane (T124MCH) at 30 and 760 Torr has been investigated by using VUV-synchrotron photoionization molecular-beam mass spectrometry. In general, the ambient pressure leads to peak-shaped profiles of light hydrocarbons, while the monotonically increasing curves are observed for light hydrocarbons and aromatics in pyrolysis of T124MCH at low pressure. A detailed mechanism

A single-pulse shock tube study of the pyrolysis of 2% C2–C6 1-alkenes is presented at 2 bar in the temperature range 900–1800 K in the current study. Reactant, intermediate and product species are obtained and quantified using gas chromatography-mass spectrometry (GC–MS) analysis. MS is used for species identification and a flame ionization detector is used for quantification. The experiments show

Solid energetic nanocomposites, consisting of reactive metal particles and oxidizers, find broad applications ranging from pyrotechnics to solid rocket propellants and solid ramjet fuels. In particular, nano-aluminum (n-Al) and polyvinylidene fluoride (PVDF) are attractive fuel and oxidizer materials, due to the high energy density of n-Al, and the high oxidizing potential and excellent mechanical

The paper is concerned with identification of the key mechanisms controlling deflagration-to-detonation transition in unconfined gaseous systems. The issue of thermal runaway triggered by positive feedback between the advancing flame and the flame-driven precompression wave is discussed in the context of expanding spherical flames. Depending on parameters of the system the transition may occur either

In the mathematical modeling of solid fuel combustion, thermal losses are commonly neglected to allow a rigorous analysis. In this work, different choice of simplifications was made, making the model more physically realistic. Besides the analysis of the solutions including existence and uniqueness, a classification in the combustion regimes as a function of thermal losses was obtained. Some examples

Plasma decay after a high-voltage nanosecond discharge was experimentally and numerically studied in pure hydrocarbons (C2H6 and C3H8), and H2O:N2 and C3H8:O2 mixtures for pressures in the range 2–4 Torr and gas temperatures from 300 to 600 K. In a stoichiometric C3H8:O2 mixture, plasma decay was also studied in a repetitively pulsed discharge for varing numbers of discharge pulses (varying degrees

Elucidating the formation of combustion intermediates is crucial to validate reaction pathways, develop reaction mechanisms and examine kinetic modeling predictions. While high-temperature pyrolysis and oxidation intermediates of alkanes have been thoroughly studied, comprehensive analysis of cool flame intermediates from alkane autoxidation is lacking and challenging due to the complexity of intermediate

The effect of laser ignition on the deflagration-to-detonation transition (DDT) was experimentally investigated. Explosive gas, which was 0.87[(1/4)C2H4+(3/4)O2]+0.13N2 contained in a smooth-wall tube at 100 kPa and approximately 20 °C, was ignited by a 1064-nm 12-ns laser at either 8 or 88.8 mm from the closed tube end connected to the gas-feeding pipe, where the incident laser energy was either 40

The concept of an edge flame structure has been adopted to explain the laminar lifted flames in a non-premixed jet. Two similarity solutions of velocity and fuel concentration have been used to explain flame stability. Recently, it was shown that the experimental results from studies of jet velocities and lift-off heights could be converted to a relationship between the edge flame speed and the fuel

A numerical investigation is carried out to understand the role of fuel Lewis number (LeF=α/DF) on flame spread over thin solid fuel in a quiescent microgravity environment. A three-dimensional numerical model was used wherein fuel Lewis number, LeF was split into directional components along and perpendicular to the fuel surface to elucidate the directional effect of fuel vapor diffusion on flame

Soot particles and their precursor polycyclic aromatic hydrocarbon (PAH) species, formed during combustion, are responsible for particulate emissions in gasoline direct injection (GDI) engines. To better understand the effects of fuel composition on formation of soot in GDI engines, the pyrolysis of several gasoline surrogates was studied in a jet-stirred reactor across a broad temperature range at

The chemical reaction between a graphite model edge and H2O is crucial in steam gasification. This study used density functional theory (DFT) calculations to systematically evaluate the reaction path of steam gasification. The research results indicate that a graphite model edge without active cites is more suitable for use as an initial model for steam gasification. The aromaticity of the graphite

Detailed one-dimensional computations of unsteady unstrained laminar flames subjected to sinusoidal equivalence ratio perturbations are presented. The responses of the flame thickness, flame speeds, species concentrations and the species reaction rates to equivalence ratio variations are investigated. The effect of stratification is quantified by comparing the structure of a stratified flame to that

The dynamics of combustion waves propagating in a solid reacting material is investigated in the presence of radiative heat losses within the one-step Arrhenius reaction mechanism and the narrow sample approximation. As expected, a C-shaped response curve caused by the competition of heat release and heat dissipation is found where the lower branch of the response curve is unstable. Along the upper

For regulatory and certification purposes the indices that characterize the ignition propensity for a fuel, Research Octane Number (RON) and Motor Octane Number (MON), are measured in a Cooperative Fuel Research (CFR) engine. In an effort to reduce the cost and time of CFR engine testing, computer simulation based work capable of predicting the octane numbers for any fuel blend has received increased

Ignition initiation by a turbulent hot jet involves complex transport and chemical processes with disparate and sensitive time scales. Its understanding is important for improved ignition in advanced and novel combustion engines and in ignition avoidance for explosion safety measures. This study is aimed at the modeling of turbulent hot jet ignition of stoichiometric hydrogen-air mixture with fast

Spray combustion of Jet A-1 and a Jet A-1/10% m-xylene blend was investigated to assess the influence of m-xylene addition on the spray characteristics and soot formation in a swirl-stabilized model combustor with dimensions of 94 mm × 94 mm cross-section and 188 mm length. Keeping the thermal power output constant at 10 kW, globally fuel lean flames were established for the neat Jet A-1 and 10% m-xylene

A combustion regime identification based on convolutional neural networks (CNNs) is developed using the recently proposed gradient-free regime identification (GFRI) approach applied to two turbulent CH4/air jet flames featuring multi-regime characteristics. The training and the subsequent application of the CNN rely on the processing of one-dimensional Raman/Rayleigh line measurements of species mass

Meso-scale modeling of heterogeneous energetic materials requires accurate description of the chemical reaction model that governs the decomposition of solid energetic crystals to gaseous products. For HMX, various 1-step and multi-step Arrhenius based chemical kinetic models are available; these chemical kinetics models for HMX have been calibrated against macro-scale experimental data under different

There is a growing interest in leaner burning internal combustion engines as an enabler for higher thermodynamic efficiency. The extension of knock-limited compression ratio and the increase in specific heat ratio with lean combustion are key factors for boosting efficiency. Under lean burning conditions, there is emerging evidence that certain fuels exhibit unusual heat release characteristics. It

Multimode space propulsion systems are being proposed that integrate high specific impulse electric propulsion and high thrust chemical propulsion. The most important attribute of this concept is a shared propellant capable of both modes of propulsion, which enables mission flexibility. One promising approach is a catalytic monopropellant thruster paired with an electrospray electric thruster. Previous

Centrally staged lean premixed pre-evaporation combustion technology has been used in aero engines for its capability in effectively reducing NOx emissions while still providing stable flames. Previous work has shown the “ignition delay” phenomenon in the forced ignition process, revealing that the burner ignition process is complex and needs further exploration. In this work, the spark ignition and

As federal programs require increasingly stringent engine emissions and fuel economy standards, these ambitions can only be met if next-generation combustion technology is developed focusing on high-efficiency and low-emissions engines. Recent research has indicated the need to operate engines at higher compression ratios and with low temperature combustion (LTC) to achieve the needed gains in engine

We present a mathematical model that describes thermo-mechanical deformations and thermal gradients on the unsteady burning of a heterogeneous solid propellant. A scaling study shows that the deformations in solid at combustion timescales can be treated as quasi-static. The resulting thermo-mechanical formulation is formulated on a Cartesian grid and makes use of a weak form of Chorin-type projection

In this study, tantalum network nanoparticles are prepared from a Ta2O5+kMg system via a liquid magnesium-controlled combustion reaction. Super-stoichiometric amounts of magnesium are used in the preparation of a reaction mixture to produce a liquid magnesium pool capable of lowering the combustion temperature and leading to the formation of Ta network structures. The heat transfer kinetics from the

The kinetics and thermochemistry for the fundamental reactions involved in low temperature autoignition of 2-pentanone were investigated by computational methods. CBS-QB3, a complete basis set method, was employed to calculate the thermodynamic parameters for the various species involved. The present study involves the decomposition pathways of alkylperoxy (ROO•), hydroperoxyalkyl (•QOOH) and hydroperoxyalkylperoxy

The mechanical properties and internal structure of soot nanoparticles is investigated using reactive molecular dynamics simulations of nanoindenting model soot particles. The particles that are provided as inputs to the simulations are generated using reactive molecular dynamics to create 3D networks of crosslinked coronene, circumanthracene and core-shell mixtures of coronene and circumanthracene

The synthesis and development of novel energetic materials is a costly, challenging process. Rather than synthesizing new materials, cocrystallization provides the potential opportunity to achieve improved properties of existing energetic materials. This work examined the effects of cocrystallization on the deflagration of a 2:1 molar cocrystal of CL-20 and HMX as well as a 1:1 molar cocrystal of CL-20

Neglecting the effect of thermal diffusion (Soret effect), we consider different formulations of multicomponent diffusion as proposed by Arias-Zugasti et al. (2016), for mixtures of dilute gases with large numbers of components. In particular, we detail the practical implementation of Model 1+M (loc.cit.) using the lowest order approximation. This is a simple and easy to implement approach, where the

Turbulent non-premixed flames with local extinction and re-ignition exhibit multiple combustion modes including ignition waves, diffusion flames, partially premixed flames, and ignition-assisted partially premixed flames. The mechanisms of local extinction and re-ignition are not well understood and numerical modeling of multi-mode combustion is a challenging task. In this work, a specially designed

The Michigan State University Narrow Channel Apparatus (MSU-NCA) was used to investigate opposed flow flame spread over samples of thermally thick Polymethylmethacrylate (PMMA). Three different fuel thicknesses were tested for mean airflow velocities 8-58 cm/s. The sample thicknesses were 6.6 mm, 12.1 mm and 24.5 mm, respectively. The measured flame position versus time determined the spread rate.

Computational prediction of thermoacoustic instabilities arising in gas turbine and aero-engine combustors still remains a challenge especially if fuel is injected in a liquid spray form. This study shows that, in LES of such a combustor, the treatment of the liquid fuel film created on the walls of the injection system affects the mean flame weakly, but modifies the flame dynamics strongly. The configuration

Due to the size and complexity of industrial-scale systems and computing limitations, semi-empirical soot models are often employed in CFD simulations rather than computationally-expensive detailed models. Many of these models were developed for specific applications with unique characteristic timescales and/or validated only under fuel-air combustion conditions. Hence, their use in different contexts

Aluminum (Al) has been widely used in solid composite propellants (SCPs) to increase the specific impulse. However, Al always subjects to coalescence, sintering to large agglomerations during combustion of SCPs resulting in larger two-phase flow losses. Herein, core-shell μ[email protected](IO3)x composites have designed and synthesized as a replacement for micron-sized Al (μ-Al) in the Al/AP/RDX/HTPB

Although the majority of existing combustion devices operate at high pressure conditions, most of our understanding of the soot formation process and soot physicochemical properties rely on studies performed at atmospheric pressure. Pressure is known to have nonlinear effects on combustion processes and a significant influence on soot formation; soot loading increases with increasing combustion pressure

n-Pentanol has been considered as a promising alternative fuel for compression-ignition engines due to its potential to reduce greenhouse gases and pollutant emissions. Engine performance is strongly dominated by fuel oxidation chemistry, and thus a more accurate determination of the coefficients of the reactions ruling its oxidation is essential for the utilization of n-pentanol in combustion engines

In the near future, lean-premixed hydrogen combustion technology for low-emission gas turbine engines is expected to be crucial in the effort to mitigate greenhouse gas emissions, in association with energy system decarbonization. In this study, we examine combustion instabilities in lean fully-premixed hydrogen-air flames in a mesoscale multinozzle array; little is currently known about how these

In the controllable combustion field, hydroxyl ammonium nitrate (HAN)-based electrically controlled solid propellants (ECSPs) is of growing interest in green fuels with safety, throttle- ability and at-will on-off capability. However, the current research is confined to the ignition characteristics and ablation process of basic ECSP formulations (75 wt% HAN ionic liquid oxidizer, 5 wt% ammonium nitrate

Piston creep and rebound are two non-ideal piston stopping behaviors in the rapid compression machine. Compared to nominal piston stopping, piston rebound/creep will result in a smaller/bigger ‘adiabatic’ core zone volume in the reaction chamber and length/shorten the ignition delay time measurements. However, the ‘adiabatic core’ hypothesis can still be validated under these compressions and ensures

In this study, the effect of sodium chloride (NaCl) on the evolution of size, mixing state, and optical properties of particle emissions was investigated. A smoking laminar diffusion flame of methane with flame length of ~100 mm was used, with and without NaCl particles introduced into the fuel stream. Extractive probe sampling with high dilution was used to sample particles and characterize their

Hydrogen and deuterium combustion over Rh, Ru, Pd and Pt wires at total pressures up to 200 Torr and initial temperatures up to 500°C is investigated in order to establish the temperature dependencies of autoignition limits over noble metal surfaces and to indicate the governing factors of gas ignition by a catalytic surface. It was found that Rh, Ru and Pd surfaces treated with 2H2 + O2 ignitions

In this work an experimental and kinetic modeling study on n-propanol and i-propanol combustion has been performed. New burning velocity measurements were carried out using the heat flux method at 1 atm over the temperature range of 323–393 K. Analysis of the temperature dependence was conducted with to verify the data consistency of the new and available data from the literature. Important inconsistencies