An innovative kinetic mechanism reduction method, Species’ Participation in Element Fluxes (SPEF), is developed in this study. It utilises species’ participation in element fluxes to evaluate the importance of the species during the combustion process. The SPEF method has two main benefits: (1) it targets at C, H and O elements instead of pre-selected target species and has only one variable threshold

In advanced propulsion systems such as scramjet engines, endothermic decomposition of onboard large hydrocarbon fuels can be used effectively for cooling and active thermal protection. During the cooling process, large hydrocarbon fuels absorb heat and decompose into small fragments. Since fuel decomposition changes the chemical and transport properties of the reactants, it is expected to affect the

(2021). Correction. Combustion Theory and Modelling. Ahead of Print.

This work proposes new analytical expressions for gaseous flames in inert porous media, based on the existing modelling strategies. The central hypothesis is that interphase heat transfer has negligible impact on the local flame structure. This requires a gradual separation between the length scales of chemical reactions, gas diffusion, and interphase thermal re-equilibriation. By resolving the gas

We investigate the effect of Taylor dispersion on the thermo-diffusive instabilities of premixed flames. This is a physically interesting and analytically tractable problem within a relatively unexplored class of problems pertaining to the interaction between Taylor dispersion (or flow-enhanced diffusion) and Turing-like instabilities in reaction–diffusion systems. The analysis is carried out in the

The spray combustion of LOX/GCH4 in the pintle injector is simulated to study the combustion characteristics at a subcritical condition by considering the effects of pintle opening distance and pintle tip angle. To perform the simulation, first, the VOF simulation was used to estimate the LOX sheet thickness and breakup length. Second, the breakup constants for the secondary breakup model were calculated

To study the influence of flame-spreading behaviour in the ignition process of different charging structures in high-density charge chambers, a visualisation device was designed, and the ignition process of the two charging structures was researched. The flame-spreading process was observed by a high-speed digital camera system and the pressure data was recorded by a data acquisition instrument. According

In order to better explore the spontaneous combustion characteristics of lignite, a low-temperature heating experimental device was used to study the changes in the physical and chemical structure of lignite in an air atmosphere of 50–350°C. Through FTIR, XRD and SEM, the coal sample's chemical structure and surface microstructure change at low temperature are correlated and analysed, and the physical

Effective dimension reduction is a key factor in facilitating large-scale simulation of high-dimensional dynamical systems. The behaviour of low-dimensional surrogate models often relies on accurate reconstruction of quantities that can be nonlinear functions of the original parameters. For instance, in low-dimensional combustion models, source terms representative of complex chemical kinetics must

Side-wall quenching (SWQ) is one of the generic configurations for flame-wall interaction and has been widely investigated through simulations using detailed and reduced chemical kinetics. In all previous related studies using manifold-based reduced kinetic models, the reduced model equations are solved in thermokinetic coordinates. This study, by contrast, will for the first time conduct SWQ simulations

A numerical experiment is conducted to examine the ignition of a near-flammability-limit low-Lewis-number mixture and the evolution processes of the resulting premixed flames in a circular thermally-conductive narrow channel. A diffusive-thermal model is adopted to describe the fuel mass conservation in the gas phase and energy conservation in both the gas and the channel wall. Spalding's ‘one-dimensional

A simplified 2D axisymmetric computational fluid dynamics simulation of oxy-coal combustion is performed to address the influence of swirl strength and the combustion environment on the flow field and combustion characteristics. A quantitative analysis of the internal recirculation zone length and flame length under various operating conditions is studied by employing developed numerical models. The

This paper presents a numerical investigation of the effects of steam and water mist/spray addition on NO formation in a methane–air counterflow diffusion flame. A detailed chemical mechanism (Glarborg et al. Modeling nitrogen chemistry in combustion, Prog. Energy Combust. Sci. 67 (2018), pp. 31–68) which contains 1397 reactions and 151 species has been employed to investigate the NO formation in a

The assumption that the gradient of temperature at the burned-side edge of a premixed flame front is zero has been usually imposed in investigating the adiabatic profile of flames for quasi-isobaric flow or in the zero-Mach-number limit. However, the non-monotonic behaviour of temperature is also observed for flames, or deflagrations, in the process of deflagration-to-detonation transition inside tubes

Combustion instability is one of the most plaguing challenges for general industrial thermal facilities, such as furnaces, gas turbine and hot air heaters. Considerable researches have been reported on developing effective active control means to mitigate combustion instability. The quick and accurate prediction of oscillating combustion characteristics is the premise of developing an active control

This paper investigates how the choice of progress variable in tabulated chemistry affects the mass burning rates of premixed laminar flames. Simulations are carried out using finite rate, detailed chemistry (DC) and Flamelet Generated Manifolds (FGM). Through comparison of detailed chemistry and FGM (using different progress variable definitions), it is found that for FGM the mass burning rate depends

This article is dedicated to Moshe Matalon on the occasion of his 70th birthday, for his numerous contributions to the field of combustion and, in particular, to the rich and varied topic of premixed flame stability. Here, we follow in his footsteps and propose a subfilter modelling framework for thermo-diffusively unstable premixed flames, such as lean hydrogen–air flames. Performing an optimal estimator

The article addresses the implications of adopting (a) non-kinetic theory-based correlations for the estimation of thermodynamic and transport properties and (b) over-simplifying assumptions, as reported in literature, in the numerical simulation of thermo-chemical conversion of char. A one-dimensional char thermo-chemical conversion model with discretisation to capture intra-particle gradients of

We report a theoretical analysis of the propagation and structure of the planar adiabatic/radiative flame in supercritical fluids, employing the Van der Waals and the Redlich-Kwong equations of state to describe the fluid properties. It is demonstrated that the effective molecular volume and attractive force terms in these non-ideal equations of state show opposite effects on the density modification

ABSTRACT Edge flames are a canonical two-dimensional flame structure appearing in lifted jet flames and in the growth and repair of flame holes in nonpremixed turbulent combustion. Computational studies of edge flames with hydrodynamic-coupling at high strains are difficult owing to difficulties defining a stationary state. A wedge-shaped counterflow configuration is here used to provide control over

Premixed flames in a narrow slot with a prescribed wall temperature subject to a Poiseuille flow are investigated for various Lewis numbers within a constant density model and using irreversible Arrhenius kinetics. A global stability analysis of steady-state solutions is carried out together with time-dependent direct numerical simulations. The unsteady results are found in good agreement with the

In order to obtain physical insights on ammonia combustion, which is characterised by exceptionally long ignition delays and increased NOx emissions, the autoignition dynamics of an ammonia/air mixture is analysed using the diagnostics tools derived from the Computational Singular Perturbation (CSP) methodology. The results are compared to the autoignition dynamics of a methane/air mixture of same

Continuum models of two-phase flow have been employed to investigate a wide variety of physical phenomena, ranging from bubbly-gas and solid-loaded liquid flows to detonation waves in granular explosives. The set of governing equations consists of mass, momentum and energy balance for each phase, and an equation for the evolution of volume fraction of either phase. The set is closed by providing an

We present 3D numerical results on tri-fuel (TF) combustion using large-eddy simulation and finite rate chemistry. The TF concept was recently introduced by Karimkashi et al. (Int. J. Hydrogen Energy, 2020) in 0D. Here, the focus is on spray-assisted ignition of methane–hydrogen blends. The spray acts as a high-reactivity fuel (HRF) while the ambient premixed methane-hydrogen blend acts as a low-reactivity

Laminar diffusion flames have been employed extensively to investigate the effects of physical and chemical-related parameters on combustion phenomena. Attention has been given to improve combustion models while keeping the two-dimensional (2D) axisymmetric approach and simplified boundary conditions. The flow structure due to the discrete jet nature of the reactants claims a more realistic inlet boundary

We present a data-driven blended equation of state (EOS) approach for condensed phase high explosive materials. We first calibrate four different high explosive materials (Nitromethane, HMX, PETN and TATB) using a single or blending multiple Fried Howard Gibbs (FHG) EOS by an ad hoc trial and error method that has been used in the past, and which leads to a predictive model that can be used in engineering

In most simulations of fine particles in reacting flows, including sooting flames, enthalpy exchanges between gas and particle phases and differential diffusion between the two phases can be neglected, since the particle mass fraction is generally very small. However, when the nanoparticles mass fraction is very large representing up to 50% of the mixture mass, the conservation of the total enthalpy

The localised forced ignition and subsequent flame propagation have been analysed for stoichiometric CH4−CO2−air mixtures with different spatial distributions and mean levels of CO2 dilution (i.e. mole fraction of CO2 in CH4/CO2 blend) for different flow conditions (e.g. quiescent laminar condition and different turbulence intensities) using three-dimensional Direct Numerical Simulations. The CH4+CO2

A technique called the Direct Simulation Monte Carlo (DSMC) method is used for simulating laminar one-dimensional hydrogen-air flames with an aim to establish the feasibility of molecular-level simulations for combustion using the Quantum-Kinetic (QK) reaction model. In DSMC, simulation particles are employed which represent many molecules with similar properties. The DSMC method effectively solves

In order to overcome the drawback (tuning reaction rate coefficients) of using a single mechanism in the chemical-kinetics-based turbulent premixed combustion modelling approach, a mechanism-dynamic-selection turbulent premixed combustion model has been developed, validated, and successfully applied to the combustion and emissions simulation of spark ignition gasoline engines. In this new model, based

In order to overcome the drawback (tuning reaction rate coefficients) of using a single mechanism in the chemical-kinetics-based turbulent premixed combustion modelling approach, a mechanism-dynamic-selection turbulent premixed combustion model has been developed, validated, and successfully applied to the combustion and emissions simulation of spark ignition gasoline engines. In this new model, based

A technique called the Direct Simulation Monte Carlo (DSMC) method is used for simulating laminar one-dimensional hydrogen-air flames with an aim to establish the feasibility of molecular-level simulations for combustion using the Quantum-Kinetic (QK) reaction model. In DSMC, simulation particles are employed which represent many molecules with similar properties. The DSMC method effectively solves

The external structure of the spray-flamelet can be described using the Schvab–Zel'dovich–Liñan formulation. The gaseous mixture-fraction variable as function of the physical space, Z ( x i ) , typically employed for the description of gaseous diffusion flames leads to non-monotonicity behaviour for spray flames due to the extra fuel supplied by vaporisation of droplets distributed into the flow. As

The external structure of the spray-flamelet can be described using the Schvab-Zel'dovich-Linan formulation. The gaseous mixture-fraction variable as function of the physical space, Z(x_i), typically employed for the description of gaseous diffusion flames leads to non-monotonicity behaviour for spray flames due to the extra fuel supplied by vaporisation of droplets distributed into the flow. As a

Steady laminar flow structures with mixing, chemical reaction, and normal strain qualitatively representative of turbulent combustion at the small scales are analysed. A contrived counterflow configuration is examined to focus more easily on the premixed flames that are known to occur in multiple-flame structures; the premixed flame can be driven by a controlled heat source which is a surrogate for

Turbulent dilute acetone spray flames are simulated in an Eulerian–Lagrangian framework using Conditional Source-term Estimation (CSE) for closure of the mean reaction rate. The objective of this work is to assess the performance of the coupled CSE-spray approach, investigated for the first time for the selected configuration. One non-reacting case and four non-premixed flames, AcF1–AcF3 and AcF5 are

This paper presents a step-forward extension of the well-known chemistry/flow interaction Eddy Dissipation Concept approach for modelling both, non-premixed and premixed, combustion regimes in a Reynolds-Averaged Navier Stokes framework. The Eddy Dissipation Concept approach and its extended versions (e.g. Partially Stirred reactors, PaSR) are widely used for CFD modelling of a variety of combustion

This paper presents a step-forward extension of the well-known chemistry/flow interaction Eddy Dissipation Concept approach for modelling both, non-premixed and premixed, combustion regimes in a Reynolds-Averaged Navier Stokes framework. The Eddy Dissipation Concept approach and its extended versions (e.g. Partially Stirred reactors, PaSR) are widely used for CFD modelling of a variety of combustion

This paper analyses the effect of injection pressures on spray and flame structures under high-pressure diesel spray conditions using a three-dimensional Reynolds-Average Navier-Stokes (RANS) model. The simulations are conducted using three kinetic mechanisms known as Luo (106 species), Cai (57 species) and Yao (54 species). Tabulation and Dynamic Adaptive Chemistry (TDAC) solver is adopted to reduce

Numerical methods for predicting the primary breakup length, the ligament and droplet diameter of fuels are a suitable substitute for experimental work. Mazut, diesel, biodiesel and water fluids are selected for the study. A linear instability model has been applied for the analysis of various liquid sprays. The effects of velocity (axial and swirl), viscosity and temperature on the atomisation of

Numerical methods for predicting the primary breakup length, the ligament and droplet diameter of fuels are a suitable substitute for experimental work. Mazut, diesel, biodiesel and water fluids ar...

In this work, we formulate a simple one-dimensional model as a framework for studying the influence of water-in-fuel emulsions on spray diffusion flames. The special contribution of these emulsions...

Simulations of pulverised coal combustion rely on various models, required in order to correctly approximate the flow, chemical reactions, and behaviour of solid particles. These models, in turn, r...

Compared to partially premixed combustion (or combustion of non-homogeneous reactants in general), fully premixed and diffusion flames represent only two asymptotic limits of combustion modes. Howe...

Stabilising a flame in scramjet engines is a current technological challenge. Indeed, the residence time in the combustion chamber is very short, thus limiting the mixing efficiency and consequentl...

Reasonable recycling low concentration methane, especially the ultra-lean methane (the concentration lower than 5%), is significant to resource saving and environment protection. Nowadays, low conc...

An a priori assessment of the disparities in estimating the filtered chemical reaction rates in Large-Eddy Simulations (LES) is performed using two Direct Numerical Simulations (DNS) of turbulent premixed flames. DNS of turbulent premixed flames with the same turbulent Reynolds number but different Karlovitz numbers are carried out using semi-detailed finite-rate chemistry to represent different flame

Large Eddy Simulation (LES) of the lab-scale methane fire plumes investigated experimentally by McCaffrey is performed using the steady laminar flamelet/presumed beta filtered density function mode...

This paper presents numerical and asymptotic analytical solutions for the current–voltage characteristic of a flame using a one-dimensional ion transport model with boundary conditions that include...

The objective of this study is to bring fundamental information on the coupling between combustion and thermal radiation occurring at flame scale. The study considers a simplified configuration cor...

This study presents careful measurements from lab-scale experiments and predictions from comprehensive numerical model for the burning characteristics of laminar flames over MMA pools of different diameters with varying ullages or lip heights. Lab-scale experiments for steady burning of MMA pool are conducted, and temperature and concentrations of major species, have been measured for 3 mm ullage case

A series of two dimensional (2D) detailed numerical simulations of premixed cylindrical expanding ethanol/air flames in a constant volume encloser under elevated pressures and equivalence ratios are performed to investigate cellular flame instability. The results demonstrate that at pressure of 10 atm and temperature of 358 K, ethanol/air flame cellular instability increases non-monotonically with

Continuation computations were performed to generate the S-curve as well as the flammability limit. Transient simulations using detailed fuel chemistry and transport models were conducted to reproduce the oscillatory extinction process. It was found that the cool spherical diffusion flame (SDF) had a much extended extinction limit than the hot SDF. The cool SDF with double-reaction-zone structure had

Due to the increasing attention of low temperature combustion, more precise and convenient low temperature chemical reaction mechanism is needed in the combustion reaction flow modelling. However, most of the conventional mechanism reduction methods are difficult to deal with the low temperature mechanism. In order to reduce the low temperature combustion mechanisms of hydrocarbon fuel efficiently

Shuttle kilns are widely used in the sanitary ware industry. A key parameter to reduce energy consumption and increase their overall performance is temperature uniformity. Therefore, in this paper a systematic and statistical study of the effect of the position of burners and their interactions on the temperature uniformity of a shuttle kiln is performed. CFD simulations and a 4k factorial analysis

Flame front identification and analysis in premixed turbulent combustion often relies on some scalar iso-surface as a flame marker, and the quest for a suitable scalar, and an appropriate flame-identifying iso-value, then becomes important. In an effort to contribute to this field, we study the suitability of various flame front identification approaches using the concept of ridge analysis. This serves

An analysis is presented for the Burke–Schumann flame established when a fuel tank discharges with mean velocity U along a circular duct of radius a filled initially with air. Attention is focused on effects of interactions of shear with transverse diffusion resulting in enhanced longitudinal dispersion. The analysis accounts for preferential-diffusion effects arising for non-unity values of the fuel

In this work we investigate the linear stability of combustion waves propagating in a system of two layers of different exothermic reacting materials under conditions of thermal contact between them through the common interface using the reaction sheet approximation. The dispersion relations are found and the dependence of the stability boundary on the parameters of the model is studied. It is demonstrated

Experimental data and detailed numerical modelling are presented on the burning characteristics of a model gasoline/biofuel mixture consisting of n-heptane and iso-butanol. A droplet burning in an environment that minimises the influence of buoyant and forced convective flows in the standard atmosphere is used to promote one-dimensional gas transport to facilitate numerical modelling of the droplet

Experimental data and detailed numerical modelling are presented on the burning characteristics of a model gasoline/biofuel mixture consisting of n-heptane and iso-butanol. A droplet burning in an environment that minimises the influence of buoyant and forced convective flows in the standard atmosphere is used to promote one-dimensional gas transport to facilitate numerical modelling of the droplet