Eddy Break-up Model Research Articles

Combustion simulation in a spark ignition engine cylinder: Effects of air-fuel ratio on the combustion duration

Combustion is an important subject of internal combustion engine studies. To reduce the air pollution from internal combustion engines and to increase the engine performance, it is required to increase combustion efficiency. In this study, effects of air/fuel ratio were investigated numerically. An axisymmetrical internal combustion engine was modeled in order to simulate in-cylinder engine flow and combustion. Two dimensional transient continuity, momentum, turbulence, energy, and combustion equations were solved. The k-e turbulence model was employed. The fuel mass fraction transport equation was used for modeling of the combustion. For this purpose a computational fluid dynamics code was developed by using the finite volume method with FORTRAN programming code. The moving mesh was utilized to simulate the piston motion. The developed code simulates four strokes of engine continuously. In the case of laminar flow combustion, Arrhenius type combustion equations were employed. In the case of turbulent flow combustion, eddy break-up model was employed. Results were given for rich, stoichiometric, and lean mixtures in contour graphs. Contour graphs showed that lean mixture (l = 1.1) has longer combustion duration.

In-depth numerical analysis on the determination of amount of CO2 recirculation in LNG/O2/CO2 combustion

Abstract The determination of proper amount of CO 2 recirculation is one of the critical issues in oxy-fuel combustion technology for the reduction of CO 2 emissions by the capture and sequestration of CO 2 species in flue gas. The objective of this study is to determine the optimum value of O 2 fraction in O 2 /CO 2 mixture to obtain similar flame characteristics with LNG–air combustion. To this end, a systematic numerical investigation has been made in order to resolve the physical feature of LNG/O 2 /CO 2 combustion. For this, SIMPLEC algorithm is used for the resolution of pressure velocity coupling. And for the Reynolds stresses and turbulent reaction the popular two-equation ( k – e ) model by Launder and Spalding and eddy breakup model by Magnussen and Hjertager were incorporated, respectively. The radiative heat transfer is calculated from the volumetric energy loss rate from flame, considering absorption coefficient of H 2 O, CO 2 and CO gases. A series of parametric investigation has been made as function of oxidizer type, O 2 fraction and fuel type for the resolution of combustion characteristics such as flame temperature, turbulent mixing and species concentration. Further the increased effect of CO 2 species on the flame temperature is carefully examined by the consideration of change of specific heat and radiation effect. Based on this study, it was observed that the same mass flow rate of CO 2 with N 2 appears as the most adequate value for the amount of CO 2 recirculation for LNG fuel since the lower C p value for the CO 2 relative to N 2 species at lower temperatures cancels the effect of the higher C p value at higher temperatures over the range of flame temperatures present in this study. However, for the fuel with high C/H ratio, for example of coal, the reduced amount of CO 2 recirculation is recommended in order to compensate the increased radiation heat loss. In general, the calculation results were physically acceptable and consistent with reported data in literature. Further work is strongly recommended for a large-scale combustor such as coal-fired power plant to figure out important parameters caused by the effect of increased combustor size and the presence of particle phase, etc.

Comparison of Combustion Models in Cleanroom Fire

AbstractIn this paper, the cleanroom fire simulation in a semi-conductor factory is investigated by using the commercial computational fluid dynamics (CFD) code. We using three different combustion models in the fire simulation. The combustion models including the volume heat source (VHS) model, the eddy break-up (EBU) model and the presumed probability density function (prePDF) model are considered to predict the cleanroom fire. The turbulence models coupled with different combustion models, while the radiation model is coupled with the turbulent combustion processes. Additionally, the discrete transfer radiation method (DTRM) is used in the global radiation heat exchange. For the fire simulation, the different combustion models are evaluated for their performance and compared with the experimental data from the literature to verify. Thus, these numerical simulations can be adopted as a useful tool to design and optimize the smoke control strategy in cleanroom fire.

Numerical Analysis of the Combustion Process in a Compressed Natural Gas Direct Injection Engine

The design, development and optimization of an internal combustion engine require the application of a modern sophisticated analysis tool. In addition to experimental work, numerical calculations are now necessary to provide an insight into the complex in-cylinder process. The combustion process and its emission characteristics in a compressed natural gas direct injection engine were analyzed and investigated. The numerical studies were performed on a single cylinder of a 1.6-liter engine running at wide open throttle. The grid generation was established through an embedded algorithm for moving mesh and boundary in order to provide a more accurate transient condition. The combustion process was modelled with the eddy break-up model of Magnussen for unpremixed or diffusion reaction with three global reaction scheme. The computational fluid dynamics (CFD) simulations at two baseline conditions are carried out to examine the fluid flow, air-fuel mixing formation, combustion process, carbon monoxide emission distribution as well as NO emission formation occurred inside engine cylinder. The CFD results were compared with the experimental data and showed a very good agreement for two baseline conditions. A set of parametric studies were carried out by varying the timings of start of injection (SOI) and start of ignition (SI). The examined engine performance is in-cylinder pressure, while the considered emissions to be minimised are CO and NO levels. In order to study the effect of injection timing, the SOI timing was varied from 120o -140o with fixed ignition timing at 19o bTDC. On the other hand, SI timing was positioned from 15o-23o bTDC with fixed SOI timing for studying its influences. The CFD results indicated that slightly retarded SOI and SI timing can be chosen to reduce CO and NO levels while increasing engine performance.

Numerical Simulation Of Diluent Effect On NOx Emission In A X Turbulent Premixed Methane Flames

The stringent requirement to reduce the NO x from various combustion devices while maintaining the combustor performance is of paramount motivation for the current study. Partially premixing, fuel blends and fuel diluents represents promising approaches for reducing NO x from flames. A detailed two dimensional, transient numerical study on the later aspect of fuel diluents (helium) to reduce the NO x emission in a back ward facing step geometry has been carried out using CFX 5.7. The equivalence ratio has been varied from 0.85-1, to study the effect of excess air on NO x emission. The methane flame is simulated using Eddy break-up model with Zeldovich thermal mechanism for NO x formation and the turbulence model is w-RSS (Reynolds Shear Stress). The simulation results indicate that considerable reduction in NO x emission and increase in flame stability can be achieved for a predetermined addition of inert in to the fuel air mixture.

Numerical study on the SNCR application of space-limited industrial boiler

Considering that the direct application of SNCR method to existing industrial boiler is usually known as not quite satisfactory mainly due to the insufficient residence time by the limitation of SNCR application space, it is quite interesting to examine whether it is possible to improve the efficiency of SNCR reaction by the adjustment of design and operational parameters. Especially one of novel concepts is the introduction of auxiliary air employed for the increase of turbulence mixing of reduction material in SNCR injection system. To this end a comprehensive computer program is developed using SIMPLE algorithm by Patankar in order to evaluate the efficiency of SNCR system for the boiler with 40 tons of steam/h using heavy oil. The computer program is made in 3-D rectangular coordinate using various phenomenological models. For example, standard k– ε turbulence model and typical eddy breakup model are incorporated for the Reynolds stresses and turbulent reaction of major fuel species, respectively. However, detailed data of chemical kinetics are also incorporated for the process of NO formation together with the NH 3 reduction reaction of SNCR system. The complex coupling phenomena between combustion chemistry and turbulence are resolved by the strategy of harmonic mean expression assuming proper empiricism. Further, the calculation of droplet trajectory and volatilization is incorporated in Lagrangian frame assuming eight possible trajectories in each grid by the consideration of the calculation efficiency and accuracy. The validation of program developed was made by the comparison with the measured temperature profile and a series of parametric investigations have been performed to enhance the NO removal efficiency. The major variables considered in this study are droplet diameter, the injection location and amount of reduction agent together with the introduction of auxiliary mixing-enhanced air for the reduction material. Based on the results of the calculation, it is found that the removal efficiency of NO was improved to a significant amount by the increase of penetration depth of the reducing agent into the center region of boiler. The increase of penetration distance and thereby the enhancement of mixing efficiency was obtained either by the employment of the mixing air together with the increase of the injection velocity and droplet size, respectively. Based on this study, the successful application of SNCR method even for the space-limited industrial boiler can be achieved by the proper increase of the mixing of reducing agents.

Subgrid Modeling for Simulation of Spray Combustion in Large-Scale Combustors

Simulations of spray combustion in full-scale combustors under different operating conditions are conducted using large-eddy simulations (LES). The current methodology attempts to capture not only spray-turbulence interactions but also subgrid fuel-air mixing and finite-rate kinetics occurring at scales below the LES resolution. Reduced finite-rate kinetics for n-heptane and kerosene fuels are used in these studies to predict pollutant emission. Comparison of LES predictions with measurements for a single-cup swirl combustor shows reasonably good agreement. Results for spray combustion in a realistic two-cup combustor sector show a complex vortex breakdown process that creates multiple recirculation regions in the combustor. These regions of recirculation provide multiple sites to stabilize the spray and the flame. Because of the shape of the combustor, significant three-dimensional effects are apparent with no similarity between flame structures, vortex breakdown bubbles, and outflow between the two cups. Spray combustion is quite efficient during full power operation because of the distributed injection process. It is also shown that in the current subgrid mixing and combustion approach flame stabilization is more physical, and the flame anchors downstream of the dump plane. In contrast, a conventional LES study using a subgrid eddy breakup model shows a flame anchored inside the inlet, Immediately downstream of the spray injector, which is unphysical.

CFD PREDICTION OF POOL FIRE BURNING RATES AND FLAME FEEDBACK

A computational fluid dynamic model with full coupling between gaseous and liquid phases is developed to predict burning rates of small- to medium-size pool fires. Rates of fuel release are calculated using predictions of flame feedback to the surface of the pool. Favre-averaged Navier–Stokes equations are solved to describe flow in the gaseous phase. Hydrocarbon combustion is described using an eddy breakup model. The heat conduction equation in the region with a regressing surface is solved to model liquid vaporization. A pool fire is modeled as an unsteady process, from the time of ignition until convergence to a quasi-steady burning rate. Comparisons are made to a number of experiments reported in the literature and include burning rates for different fuels, as well as total and radiative flame feedback to the burning surface.

On the effect of the local turbulence scales on the mixing rate of diffusion flames: assessment of two different combustion models

A mathematical model for the prediction of the turbulent flow, diffusion combustion process, heat transfer including thermal radiation and pollutants formation inside combustion chambers is described. In order to validate the model the results are compared herein against experimental data available in the open literature. The model comprises differential transport equations governing the above-mentioned phenomena, resulting from the mathematical and physical modelling, which are solved by the control volume formulation technique. The results yielded by the two different turbulent-mixing physical models used for combustion, the simple chemical reacting system (SCRS) and the eddy break-up (EBU), are analysed so that the need to make recourse to local turbulent scales to evaluate the reactants' mixing rate is assessed. Predictions are performed for a gaseous-fuelled combustor fired with two different burners that induce different aerodynamic conditions inside the combustion chamber. One of the burners has a typical geometry of that used in gaseous fired boilers—fuel firing in the centre surrounded by concentric oxidant firing—while the other burner introduces the air into the combustor through two different swirling concentric streams. Generally, the results exhibit a good agreement with the experimental values. Also, NO predictions are performed by a prompt-NO formation model used as a post-processor together with a thermal-NO formation model, the results being generally in good agreement with the experimental values. The predictions revealed that the mixture between the reactants occurred very close to the burner and almost instantaneously, that is, immediately after the fuel-containing eddies came into contact with the oxidant-containing eddies. As a result, away from the burner, the SCRS model, that assumes an infinitely fast mixing rate, appeared to be as accurate as the EBU model for the present predictions. Closer to the burner, the EBU model, that establishes the reactants mixing rate as a function of the local turbulent scales, yielded slightly slower rates of mixture, the fuel and oxidant concentrations which are slightly higher than those obtained with the SCRS model. As a consequence, the NO concentration predictions with the EBU combustion model are generally higher than those obtained with the SCRS model. This is due to the existence of higher concentrations of fuel and oxygen closer to the burner when predictions were performed taking into account the local turbulent scales in the mixing process of the reactants. The SCRS, being faster and as accurate as the EBU model in the predictions of combustion properties appears to be more appropriate. However, should NO be a variable that is predicted, then the EBU model becomes more appropriate. This is due to the better results of oxygen concentration yielded by that model, since it solves a transport equation for the oxidant concentration, which plays a dominant role in the prompt-NO formation rate. Copyright © 2002 John Wiley & Sons, Ltd.

Modeling and simulation of coal dust explosions

Existed work of former researchers on dust explosion/detonation modeling is reviewed. A coal dust explosion model is developed. Validation of the model is carried out for a type of coal with wide range of size distribution. The characteristics of presented model is: 1. Eulerian-Lagrangian two phase flow model; 2. Non-elemental Arrhenius model and Eddy Breakup model for gas reactions; 3. Detail mechanisms of water vaporization, volatile decomposition and surface reaction of carbon; 4. The κ - ∈ turbulence model for gas phase and random trajectory model for particle phase. Operator splitting method is employed to solve the governing equations. Flux Corrected Transport scheme is used to solve convective parts of the gas equations, and implicit scheme is used to solve the diffusion parts. The source terms are solved using an anti-stiff ordinary equation solver.

Turbulent Combustion

The book Turbulent Combustion by Norbert Peters is a concise monograph on single-phase gaseous low Mach number turbulent combustion. It is compiled from the author's review papers on this topic plus some additional material. Norbert Peters characterizes turbulent combustion both by the way fuel and air are mixed and by the ratio of turbulent and chemical time scales. This approach leads naturally to detailed models, which are based on results of turbulence modelling and asymptotic flame theory. In both areas Norbert Peters has contributed significantly over the last two decades. The book has four sections. In chapter 1 he discusses briefly the state of the art of combustion models as they are used by different authors. Important turbulent and chemical scales are introduced, which are then used to introduce and explain the different combustion models. He distinguishes between premixed and non-premixed combustion and also between infinitely fast and finite rate chemistry. The current turbulent combustion models are described in order of their complexity and physical accuracy. He explains Eddy BreakUp and Eddy Dissipation Models, the fundamentals of the PDF transport equation, and the laminar flamelet concept applied to non-premixed and premixed turbulent combustion. Then, the Conditional Moment Closure, the Linear Eddy Model, and combustion models used in Large Eddy Simulations are described very briefly. Chapter 2 is devoted to premixed turbulent combustion. After introducing some characteristic dimensionless numbers Peters uses the level set approach and the flamelet concept to formulate a combustion model valid in the thin zone and corrugated reaction zone regimes. He shows parallels between this more fundamental model and standard models like the Bray-Moss-Libby model. He also presents models for the turbulent burning velocity, the Flame Surface Area Ratio, and discusses the effects of gas expansion. Very helpful for the reader's understanding is the presentation of three worked examples of a slot burner, a propagating spherical flame and an oscillating counter flow. Peters' model for premixed turbulent combustion is based on the equations for the mean and the variance of the $G$-equation, some closure relations as well as the flamelet equation for premixed combustion. A numerical example is used to discuss its accuracy. Non-premixed turbulent combustion is the subject matter of chapter 3. Peters uses the mixture fraction variable and asymptotic flame theory to explain the regimes of non-premixed turbulent combustion. Two worked examples of a counterflow diffusion flame and the one-dimensional unsteady laminar mixing layer help the reader to understand the theory. After discussing turbulent jet diffusion flames and introducing the flamelet equation he develops steady and unsteady flamelet models for non-premixed turbulent combustion. In particular, the Eulerian Particle Flamelet Model and the RIF (Representative Interactive Flamelet) Model are discussed. These models have been used to predict pollutant formation in a gas turbine and a direct injection Diesel engine, respectively. Finally, partially premixed combustion is discussed in chapter 4. Lifted turbulent diffusion flames are reviewed and the prediction of the lift-off height is identified as a key problem. This leads directly to the introduction of the concept of a triple flame. Different models for partially premixed combustion are then presented and the numerical simulation and the scaling of lift-off heights in turbulent jet flames are studied. There is no doubt that this book is well written and is an important contribution to combustion literature. Peters uses asymptotic theory and scale separation to develop combustion models from first principles. Also, the book contains a comprehensive review of the current literature on turbulent combustion. It is clearly a `must have' for experienced combustion modellers and experimentalists. The book has not been written for non-experts and beginners; these readers would probably have liked more worked examples and exercises, a list of symbols, some material on the mathematical techniques of asymptotic analysis, and a more detailed discussion of the standard combustion models that are often used in the literature. Also, the numerical aspects of turbulent combustion modelling are not discussed in the book. Nevertheless, the book will be a useful source for advanced courses on combustion. Markus Kraft

Numerical study on the coal gasification characteristics in an entrained flow coal gasifier

The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The k– ε turbulence model was used for the gas phase flow while the Random-Trajectory model was applied to describe the behavior of the coal slurry particles. The unreacted-core shrinking model and modified Eddy break-up (EBU) model, were used to simulate the heterogeneous and homogeneous reactions, respectively. The simulation results obtained the detailed information about the flow field, temperature and species concentration distributions inside the gasifier. Meanwhile, the simulation results were compared with the experimental data as a function of O 2/coal ratio. It illustrated that the calculated carbon conversions agreed with the measured ones and that the measured quality of the syngas was better than the calculated one when the O 2/coal ratio increases. This result was related with the total heat loss through the gasifier and uncertain kinetics for the heterogeneous reactions.

Comparison of different combustion models in enclosure fire simulation

In this study, three combustion models, the volumetric heat source (VHS) model, the eddy break-up model and the presumed probability density function (prePDF) model, are examined in enclosure fire simulation. The combustion models are compared and evaluated for their performance in predicting three typical enclosure fires, a room fire, a shopping mall fire and a tunnel fire. High Reynolds number turbulence k– ε model with buoyancy modification and the discrete transfer radiation model (DTRM) are used in the simulation. Corresponding experimental data from the literature are adopted for validation. The results show satisfactory prediction in flow patterns and features in the complex enclosure fires. However, it is shown that these combustion models are not able to show consistent performance over the different locations and enclosure fires. The needs for adequate turbulent combustion models in enclosure fires are discussed.

Possibilities and limitations of the Eddy Break-Up Model

Possibilities and limitations of the Eddy Break-Up Model

A turbulent reaction rate model for premixed turbulent combustion in spark-ignition engines

A new reaction rate model has been developed and validated for premixed turbulent combustion in spark-ignition (SI) engines. The formulation is within the context of the Bray–Moss–Libby (BML) formalism for turbulent transport in premixed flames. The laminar flamelet concept is employed to split the volumetric reaction rate into a reaction rate per unit surface area and a surface area per unit volume. The development has involved the implementation of an algebraic functional dependence of the laminar burning velocity on the reaction mixture strength, temperature, and pressure [1]. Also, the flame surface area per unit volume is modeled in a novel and physically reasonable manner that avoids any explicit dependence on local turbulent length and time scales, by modeling the laminar flamelet wrinkling length scale as a function of laminar flame properties as well as turbulent quantities. The resulting expression for the mean turbulent reaction rate is implemented in a computer code together with the BML second moment model for turbulent transport. Second-order accurate bounded spatial discretization is employed. The governing equations have been transformed into a moving coordinate system to take into account the piston motion. A feasibility study is carried out on the application of the new model to computation of flame propagation in SI engines. The empirical constants of the new modification of the model have been tuned and evaluated by capturing experimental engine cylinder pressure histories. A comparison between the present calculations and identical computations of engine cylinder pressure demonstrates the validity of applying the model in SI engine computations. Also, and unlike the standard Eddy Break-up (EBU) and basic flamelet models, the new model displays no tendency to produce excessive reaction rates in the presence of solid walls. A parametric study shows the model to behave in a satisfactory manner in response to changes in fuel type, equivalence ratio, ignition timing, compression ratio, and engine speed.

Numerical Analysis of Ignition Transient in an Axisymmetric Solid Rocket Motor Equipped with Rear Ignition System

A numerical simulation is completed to analyze the ignition transient in a solid rocket motor with rear ignition system. Time-dependent compressible SIMPLER algorithm for gas phase governing equations and finte volume method (FVM) for radiative transfer equation are employed, respectively. Two dimensional conduction equation for propellant grain is combined as well. While the standard k - ε model with wall function is used for turbulence, the eddy break-up (EBU) model is used for gas phase reaction rate. A detailed development of unsteady flow and temperature fields is obtained. Especially, the radiation is found to play a significant role in igniting the solid propellant by promoting the heat feedback to propellant surface. When the radiation transport was not considered, the predicted ignition and flame spreading sequence was in error, based on a limited experimental data.

CFD modelling of confined jet fires under ventilation-controlled conditions

This paper presents field predictions for two confined jet fires under ventilation-controlled conditions. Three different combustion models, namely the laminar flamelet model, the constrained equilibrium (CE) method and the eddy break-up (EBU) model, are used and compared. The laminar flamelet model and the CE method are coupled with Lindstedt's soot model, while the EDU model is coupled with the soot model of Magnussen. The global radiative heat exchange is considered by using the discrete transfer radiation method (DTRM) and the calculation of the microscopic radiative heat exchange within the flamelet is embeded in RUN-1DL. For both the flamelet and CE methods, the energy equation is solved so that the radiation calculation is coupled with the computation of the turbulent combustion processes. Comparisons are made between the experimental data and the predictions of different sub-model combinations for two propane jet fires in enclosures of 135 and 415 m 3. It is found that all the sub-model combinations predict the correct trends of distributions for field variables such as velocity, temperature, soot, and CO. The predicted temperature distributions from the flamelet approach, which includes both the microscopic and global radiative heat losses, are found to be in close agreement with the experimental data. Modifications are made to the convective heat transfer coefficients between the wall and the gaseous products in the impinging region and this is found to have improved the predictions for the wall heat fluxes.

Numerical simulation of dump combustor with auxiliary fuel injection

Solutions of the steady, two-dimensional Navier-Stokes, thermal energy, radiation flux, and species conservation equations have been computed for a dump combustor geometry with downstream constriction. The equations are solved in the conservative finite-difference form on a nonuniform rectilinear grid of sufficient resolution to capture the momentum/thermal boundary layers accurately. The numerical procedure, SIMPLEST, which is a variation of SIMPLE, is used to ensure more rapid convergence. A κ−e model is incorporated for the enclosure of turbulence with a wall function. The combustion model, ESCRS (extended simple chemically-reacting system) with eddy break-up model for the reaction rates of species conservation equation or energy equation is also used. For the good destruction of hazardous waste, it is effective that the waste is injected in the recirculation zone of high temperature with the condition not disturbing the combustion cavity. Excess oxygen from a lean core flame can be effectively utilized for waste destruction with the hydrocarbon waste injection as fuel-rich condition. The core flame has a significant impact on the structure of recirculation cell, in some cases completely changing the nature of the flow within the cavity. The optimum velocity of waste injection exists for the highest temperature at the recirculation zone. A premixed flame type for the auxiliary fuel is good for high temperature and long residence time to be large cavity in the recirculation zone.

Application of a Detailed Emission Model for Heavy Duty Diesel Engine Simulations

A detailed chemical model describing the formation of soot and NO is applied to simulate emission formation in a heavy duty diesel engine. Cylinder flow and spray development is simulated using an engine CFD code - Speedstar. Combustion is described using a simple eddy break-up model. Modeling of the emission-chemistry/turbulent-flow interaction is based on a flamelet approach. Contrary to a typical flamelet concept, transport equations are solved for mass fractions of soot and NO. The reason being that these major emission constituencies are assumed to change slowly in comparison to typical time scales for chemical processes or transport processes important for combustion. Chemical reactions leading to production and destruction of soot and NO are, however, assumed to be fast. Soot and NO source terms are therefore evaluated from a flamelet library using a presumed probability density function and integrating over mixture fraction space. Results from simulations are compared to engine measurements inform of exhaust emission data and cylinder pressure.

Numerical modelling of combustion in a zinc flash smelter

The development of a mathematical model for the flash smelting of zinc concentrate is described. A commercial computational fluid dynamics package, CFX4.1, has been used and additional codings for zinc concentrate smelting and combustion of natural gas have been developed and incorporated into the package. In the simulation, gas is combusted using the eddy break-up model and the gas–particle reactions are limited by a combination of heat transfer and mass diffusion. For the zinc concentrate combustion submodel, the concept of a composite particle was adopted to include the contributions from all minerals present in the concentrate. It is assumed that after heating to a temperature of 803 K, the pyrite in the composite particle decomposes and ignites. When the particles are further heated to a temperature of 1873 K, they melt and zinc sulphide vaporizes to form gaseous sulphur and zinc. The sulphur combusts to form sulphur dioxide and heat is released to the gas phase. The rate of vaporization is limited by the supply of heat to the particle. After all the zinc has left the particle, the oxidation of FeS in the concentrate commences and is controlled by the rate of oxygen diffusion to the particle surface. Modelling results of the combustion within the environment of a gas-fired furnace are presented as an example of the simulations performed for flash smelting of zinc concentrate.