Mechanism Of Flame Acceleration Research Articles

Velocity match between plasma and flame in microwave-assisted spark ignition

As a prospective ignition technique, microwave-assisted spark ignition (MAI) can accelerate flame and thus satisfy the demand for effective ignition. However, its acceleration mechanism on flame velocity is still unclear, which hinders its application and optimizations. Therefore, this research focuses on understanding the flame acceleration mechanism behind MAI. In this paper, MAI is achieved through radiating a microwave pulse after spark ignition. The flame velocity and the precise absorbed energy under different combustion conditions are investigated with flame kernel's Schlieren images and microwave energy diagnostics, respectively. The results show that MAI accelerates flame primarily by the interaction between microwave plasma and flame front, rather than the free electrons within the flame. Specifically, microwave accelerating flame takes two processes: energy absorption, and velocity match. Energy absorption refers to the microwave energy absorbed by residual electrons after ignition to generate and sustain microwave plasma, while velocity match involves the outward plasma with faster velocity propelling the slower flame front. Moreover, the plasma velocity shows a positive relationship with absorbed microwave energy. The velocity match between microwave plasma and flame is important to successful flame acceleration. Besides, the efficiency of energy absorption and flame acceleration varies with plasma type (glow or incandescent). Glow plasma is characterized by effective flame acceleration but relatively low absorption efficiency, and incandescent plasma is in reverse. The maximum absorption efficiency can be elevated to 70 % with incandescent plasma occurring. Ultimately, the plasma velocity declines with its traveled distance, which might impair the flame acceleration.

Mechanism of accelerating premixed hydrogen/methane flame with flexible obstacles

Low-velocity laminar flames gradually accelerates under the joint action of various mechanisms, and develops from deflagration to detonation, and the mechanism in this process is the focus of explosion dynamics research. This article presents experimental results of the propagation of premixed hydrogen/methane flames in square-section channels with flexible and rigid obstacles at a blockage ratio (BR) of 0.3. Theory and experiment show that the acceleration effect of flexible obstacles on flame is weaker than that of rigid obstacles. The results show that there are many differences in the physical mechanism of flame acceleration. It is mainly reflected in the difference between the two obstacles on turbulence guidance, and the difference in the peak pressure of flame propagation. The flexible obstacles create smaller turbulence and absorbs the transverse waves within the pipe that continuously accelerate the flame. At the same time, compared with rigid obstacles, flexible obstacles can effectively reduce the peak flame tip speed Vmax, and the peak flame tip speed reduction rate is the highest by 22.86%. In addition, unburned pockets formed by obstacles play a key role in the acceleration of the flames. The expansion of gas in the flexible obstacle pocket expands the obstacle spacing, accelerates the fuel combustion in the pocket, and avoids the concentrated release of fuel energy. The intensity of the turbulence and the velocity of the flame are lower after passing through the obstacle area, showing a lower explosion risk than rigid obstacles.

Design and Development of Explosion-Proof Cavity of Hydraulic System Power Unit Applied in Explosion-Proof Area

The construction machinery and vehicles, especially the explosion-proof and explosion-isolation ability of the vehicles are playing an increasingly important role in the complex and unpredictable emergency rescue field. In this paper, the explosion-proof housing of hydraulic system power unit applied in engineering machinery is investigated, wherein the power unit includes motor, power supply and control element. Motor-driven hydraulic pump provides the necessary power for the hydraulic system. The gas explosion process, basic parameters, flame acceleration mechanism and the theory model of gas explosion in finite space are analyzed. Relevant mathematical models of the experimental gas explosion for explosion-proof cavity are established. Furthermore, the models are analyzed by numerical method. We simulate the dynamic process of explosion by software. The analysis, examination and simulation of structural strength are conducted on the explosion-proof cavity according to the maximum explosion pressure obtained from the simulation results. The reasonable design parameters satisfying the explosion-proof requirements are obtained. The explosion-proof cavity which is processed according to the design parameters is tested. The explosion-proof performance is verified by analyzing the experimental results. According to the test standard, the impact test, thermal test, pressure test, overpressure test and propagation test under internal ignition for the cavity are conducted. The results show that the pressure test coincides with the simulation results. The remaining test results also satisfy the experimental purpose. The reasonableness of the design of the explosion-proof cavity is verified, which can meet the actual requirements of the equipment.

Coupling effect of side explosion vent and wire mesh on suppressing methane explosion in a closed duct

The coupling effect of the side explosion vent and wire mesh on suppressing methane explosion has been investigated in this study, aiming to prevent huge losses caused by a methane explosion in industrial organic waste gas treatment. It constructed a closed simulation duct with a length of 3000 mm and an internal dimension of 120 mm × 120 mm containing a side explosion vent at different positions, in which flame behaviours and overpressure characteristics accompanying methane explosion were analyzed to get conclusions. The results indicate that side explosion vents located in the same duct section have a similar explosive flame development trend, and the suppression effect is better as closer to the ignition source. Besides, it is necessary to avoid the redevelopment of flame and the backfire downstream of a side explosion vent. In addition, the overpressure released through side explosion vents is significantly suppressed. However, the wave-absorbing and heat-absorbing properties of the wire mesh installed in the duct are only effective for some configurations with low flame speeds. Moreover, the side explosion vent closed to the ignition source effectively suppresses undeveloped flame. In this case, it leads to a complete application of the porous media quenching performance. To sum up, the coupling suppression effect of the side explosion vent and wire mesh on flame is complementary. However, there is an opposite conclusion for the experimental configurations where side explosion vents are downstream of the duct; a high-speed turbulent flame is difficult to be suppressed by the wire mesh and side explosion vent in a flame acceleration mechanism.

Modelling and computation of large-scale open atmosphere hydrogenair deflagration

Studying of gas deflagration is important for a safety purpose in gas industry. A modelling approach based on large eddy simulation (LES) technique for modelling turbulent flow combined with the species mass fraction equations for modelling combustion is used. Different flame acceleration mechanisms, hydrodynamic & thermo-diffusive instabilities, turbulence, and their interaction in addition to flame quenching model are used to model chemical reaction rate. An algebraic model for flame-generated turbulence is incorporated. The model is tested against large scale open atmosphere hydrogen-air experiment. The flame propagation radius and the overpressures are qualitatively compared well with experiment and the state-of-the-art simulations.

Effect of DME addition on flame dynamics of LPG/DME blended fuel in tail space of closed pipeline

In order to recognize and reveal the explosion characteristics and hazards of LPG blended fuel with active fuel additions, flame dynamics of liquefied petroleum (LPG)/dimethyl ether (DME) blended fuel in the tail space of a closed pipeline was experimentally investigated. A high-speed camera and a pressure transducer were used to acquire the flame structure and explosion overpressure, and the displacement and speed were further calculated by MATLAB programming. The research results show that the flame under the conditions of stoichiometric and lean-fuel concentration presents a more remarkable local suppressive propagation compared with the rich-fuel condition. In the vicinity of stoichiometric concentration, the increase of equivalence ratio leads to the increase of flame front temperature, meanwhile, the process also improves the molecular diffusion coefficient and heat transfer efficiency. The reverse propagation of flame brings obvious temperature loss to fuel system. The existence of reflected reverse flow makes it difficult for the flame to propagate to the end of the closed space. The increase of equivalence ratio and DME blended ratio is helpful for the improvement of flame suppressive mechanism and flame acceleration mechanism, and the effect of the latter is more obvious. The knowledge obtained about flame dynamic characteristics can improve the assessment and recognition of explosion hazards of blended fuel.

Shock wave evolution and overpressure hazards in partly premixed gas deflagration of DME/LPG blended multi-clean fuel

In order to reveal the shock wave propagation and overpressure hazards of DME (dimethyl ether)/LPG (liquefied petroleum gas) blended fuel in the process of partly premixed gas deflagration, both experimental apparatus and numerical model for multiple-gas explosion and propagation are established. The results show that the overpressure in the sharp-dropping overpressure hazards zone are generally more than 200 kPa, and the distribution range was 5.75–6.75 times of the maximum overpressure hazards zone. The overpressure in the gentle-dropping overpressure hazards zone is the smallest, but its propagation and influence distance is the largest, which can cause certain damage to people and buildings in the far field. The participation of DME at lean-fuel concentration had the greatest effect on the increase of overpressure hazards in the original premixed zone, which could reach 306.6%. The increase of equivalence ratio and the addition of DME fuel both accelerate the superposition of multiple pressure waves. High overpressure risk is always accompanied by high overpressure evolution speed. As equivalence ratio increases, the relationship between the average shock wave velocity and the DME blended ratio was linear, quadratic and cubic, also the flame acceleration mechanism by high burning rate and the flame deceleration mechanism by low combustion heat successively dominates.

Further insight into the gas flame acceleration mechanisms in pipes. Part I: Experimental work

Some years ago, one of the authors (Proust, 2015) published the conclusions of a rather large experimental work devoted to the gas flame acceleration down a long pipe. It was concluded that the flame propagation could be represented by a constantly accelerating piston. The acceleration parameter seems to be primarily linked to the expansion velocity of the burnt product. Other parameters seemed of secondary importance questioning in particular the respective roles of the turbulence of the flame and of the instabilities.Further experiments were performed using perfectly smooth and rough tubes (Fig. 1), varying the diameter of the pipe (150 and 250 mm) and the reactivity of the mixtures (methane-air and hydrogen air at various equivalence ratios). The smooth pipe is transparent enabling a direct visualization of the flame during the flame propagation and a refined resolution of the flame trajectory (in the steel pipes standard flame sensors were used). The pressure was measured at various locations but also the flow velocities in the boundary to try and detect any turbulence development. Only homogeneous and quiescent mixtures were studied and the flame was propagated from a closed ignition end toward the other open end. The results of the parametric study are presented in this paper.

Further insight into the gas flame acceleration mechanisms in pipes. Part II: Numerical work

This paper is the second part of a global study investigating the physics of premixed flame propagation in several kinds of long pipes. It focuses on the potential of CFD for modelling such cases. Four tests among the database detailed in the first part are selected. In each case, the pipe is straight, open at one end and closed at the other where ignition is triggered. The pipe is filled with a stoichiometric methane/air mixture at rest. The parameters which are varied are the inner pipe diameter and the pipe material.CFD computations based on a URANS framework are carried out and enable to recover several physical trends, such as the role of acoustics and boundary layer turbulence on the flame dynamics. Although most orders of magnitude of the measured overpressure peaks can be predicted numerically, the computed flames are quicker than the measured ones. It could be explained by the chosen turbulent model, the k-ω SST model, known to be adapted for wall-bounded flows but to produce too much turbulence for accelerating flows. The criterion for the cells size near wall (y+<200) might also be too loose.

Mechanism of flame acceleration and detonation transition from the interaction of a supersonic turbulent flame with an obstruction: Experiments in low pressure propane–oxygen mixtures

The present paper seeks to determine the mechanism of flame acceleration and transition to detonation when a turbulent flame preceded by a shock interacts with a single obstruction in its path, taken as a cylindrical obstacle or a wall in the present study. The problem is addressed experimentally in a mixture of propane–oxygen at sub-atmospheric conditions. The turbulent flame was generated by passing a detonation wave through a perforated plate, yielding flames with turbulent burning velocities 10 to 20 larger than the laminar values and incident shock Mach numbers ranging between 2 and 2.5. Time resolved schlieren videos recorded at approximately 100 kHz and numerical reconstruction of the flow field permitted to determine the mechanism of flame acceleration and transition to detonation. It was found to be the enhancement of the turbulent burning rate of the flame through its interaction with the shock reflection on the obstacle. The amplification of the burning rate was found to drive the flame burning velocity close to the speed of sound with respect to the fresh gases, resulting in the amplification of a shock in front of the flame. The acceleration through this regime resulted in the strengthening of this shock. Detonation was observed in regions of non-planarity of this internal shock, inherited by the irregular shape of the turbulent flame itself. Auto-ignition at early times of this process was found to be negligibly slow compared with the flow evolution time scale in the problem investigated, suggesting that the relevant time scale is primarily associated with the increase in turbulent burning rate by the interaction with reflected shocks.

Experimental studies on pressure dynamics of C2H4/N2O mixtures explosion with dilution

Safety concerns of N2O has arisen due to its extensive existence in nuclear waste and aerospace applications. In present study, the stoichiometric mixtures of C2H4/N2O with N2 or CO2 dilution were examined to know the explosion mechanism and hazard. The experiments were carried out in a standard 20-L spherical explosion vessel with pressure sensor at initial pressures of 0.2 bar, 0.35 bar and 0.5 bar. The results show that, with less than 30% dilution (N2 or CO2, in mass fraction), there exists a flame acceleration mechanism or transition to detonation with measured maximum explosion pressure approaching Chapman-Jouguet (CJ) detonation pressure. Furthermore, at initial pressure of 0.2 bar, the explosion process presents three distinct stages, while at 0.35 bar or 0.5 bar, the third stage is hard to be distinguished, which indicates less accomplished transition to detonation due to the shorter combustion duration in the vessel. Besides, both N2 and CO2 dilutions can inhibit the explosion through constraint to N2O decomposition via enhanced trimolecular reaction, O + N2 + M → N2O + M (R4). But compared to CO2, N2 is more effective in R4, which results in better inhibition effect. By contrast, with 30% or more dilution, the explosion agrees well with the prediction by chemical equilibrium method at adiabatic condition. Sharp peak (SP) and broad peak (BP) were observed and interpreted.

Turbulent flame augmentation using a fluidic jet for Deflagration-to-Detonation

Detonation is a high energetic mode of pressure gain combustion that exploits total pressure rise to augment high flow momentum and thermodynamic efficiencies. Detonation is initiated through flame acceleration driven by turbulence interaction and induction for Deflagration-to-Detonation Transition (DDT). There is a broad desire to unravel the physical mechanisms of turbulence induced DDT. The study examines the role of turbulence induced by a fluidic jet on turbulent accelerating flames. The investigation aims to classify the turbulent flame dynamics and temporal evolution of the flame stages throughout the turbulent regimes. The flame-flow interactions are experimentally studied in a detonation facility using high-speed particle image velocimetry (PIV) and Schlieren imaging. The analysis explores the local turbulence and flame acceleration mechanisms that result from the high level of turbulent transport induced by the jet. Higher flame acceleration is observed for the turbulent flame relative to the laminar flame. The turbulent flame experiences high propagation of turbulence intensities in the lower flame boundary. An increase in vorticity generation, velocity fluctuation, and turbulent strain-rate is experienced throughout the interaction. The turbulent flame regime is characterized showing an evolution between the thin-to-broken reactions.

GASFLOW-MPI: A new 3-D parallel all-speed CFD code for turbulent dispersion and combustion simulations: Part I: Models, verification and validation

The objective of the presented work is to develop an efficient and validated approach based on a multi-dimensional computational fluid dynamics (CFD) code for predicting turbulent gaseous dispersion, conjugated heat and mass transfer, multi-phase flow, and combustion of hydrogen mixtures. Applications of interest are accident scenarios relevant to nuclear power plant safety, renewable energy systems involved in hydrogen transport, hydrogen storage, facilities operating with hydrogen, as well as conventional large scale energy systems involving combustible gases. All model development is conducted within the framework of the high-performance scientific computing software GASFLOW-Multi-Physics-Integration (MPI). GASFLOW-MPI is the advanced parallel version of the GASFLOW sequential code with many newly developed and validated models and features. The code provides reliability, robustness and excellent parallel scalability in predicting all-speed flow-fields associated with hydrogen safety, including distribution, turbulent combustion and detonation. In the meanwhile, it has been well verified and validated by many international blind and open benchmarks.The recently developed combustion models in GASFLOW-MPI code are based on the transport equation of a reaction progress variable. The sources consist of turbulence dominated and chemistry kinetics dominated terms. Models have been implemented to compute the turbulent burning velocity for the turbulence controlled combustion rate. One-step and two-step models are included to obtain the chemical kinetics controlled reaction rate. These models, combined with the efficient and verified all-speed solver of the GASFLOW-MPI code, can be used for simulations of deflagration, detonation and the important transition processes like flame acceleration (FA) and deflagration-to-detonation-transition (DDT), without additional need for expert judgment and intervention. It should be noted that the major goal is to develop a reliable and efficient numerical tool for large-scale engineering analysis, instead of resolving the extremely complex physical phenomena and detailed chemistry kinetics on microscopic scales. During the course of this development, new verification and validation studies were completed for phenomena relevant to hydrogen-fueled combustion, such as shock wave capturing, premixed and non-premixed turbulent combustion with convective, conductive and radiation heat losses, detonation of unconfined hydrogen–air mixtures, and confined detonation waves in tubes. Excellent agreements between test data and model predictions support the predictive capabilities of the combustion models in GASFLOW-MPI code. In Part II of the paper, the newly developed CFD methodology has been successfully applied to a first analysis of hydrogen distribution and explosion in the Fukushi Daicchi Unit 1 accident.The major advantage of GASFLOW-MPI code is the all-speed capability of simulating laminar and turbulent distribution processes, slow deflagration, transition to fast hydrogen combustion modes including detonation, within a single scientific software framework without the need of transforming data between different solvers or codes. Since the code can model the detailed heat transfer mechanisms, including convective heat transfer, thermal radiation, steam condensation and heat conduction, the effects of heat losses on hydrogen deflagrations or detonations can also be taken into account. Consequently, the code provides more accurate and reliable mechanical and thermal loads to the confining structures, compared to the overly conservative results from numerical simulations with the adiabatic assumptions.Predictions of flame acceleration mechanisms associated with turbulent flames and flow obstacles, as well as DDT modeling and their comparisons to available data will be presented in future papers. A structural analysis module will be further developed. The ultimate goal is to expand the GASFLOW-MPI code into an integral high-performance multi-physics simulation tool to cover the entire spectrum of phenomena involved in the mechanistic hydrogen safety analysis of large scale industrial facilities.

Effectiveness of diluent gases on hydrogen flame propagation in tee pipe (part II) – Influence of tee junction position

Gas explosions in obstructed vessels have been investigated for many years. However, the flame acceleration mechanism of enriched-hydrogen fuels with diluents in the piping system has received little systematic study in the literature. This particular study aimed to analyse the flame front mechanism of hydrogen-diluents/air explosion inside the pipe by considering the influence of tee junction distance from the ignition points. The tests were performed using H2/diluents-air at different concentrations and ignition positions, in two different tee junction pipe configurations. From the results, the worst case of explosion severity was found in 95% H2–2.5% Ar–2.5% N2/air for all ignition positions. In general, if ignition happened at the tee junction, the overpressure and rate of pressure rise profiles showed almost a similar trend on both configurations. Similar trend was also observed for the flame flow characteristic analysis. Overall, it was clearly demonstrated that a shorter distance between ignition point and obstacles resulted in higher explosion severity.

Theoretical and computational studies of wall friction flame acceleration mechanism with linear variation of planar flame speed.

Majority of theories, associated with the variety of flame acceleration scenarios, are based on the "geometrical formulation”: namely, the wrinkled to planar flame speeds ratio, Sw / SL , is evaluated as the scaled increase in the flame surface area, while the entire combustionchemistry is immersed inSL , which is assumed to be constant. However, in the practical reality,SL may experience spatial and temporal variations; at least, due to the associated pressure andtemperature distribution within a combustor, and their evolution during burning. In the present work, we initiate the systematic study of a much more intriguing situation – when SL - variations are externally imposed in a manner being a free functional of the formulation. This is relevant, in particular, to multi-phase combustion in dusty environment, with a non-uniform distribution of combustible and/or inert dust; as well as to the event of spatial variations of the equivalenceratio. First, linear variation of spatialSL - distribution is incorporated into the Bychkov theories offlame acceleration due to wall friction [Physical Review E 72 (2005) 046307] and solved analytically. Second, we implement linear variation of flame speed into computational platform. A backbone for the platform is a fully compressible, finite-volume Navier-Stokes code solving for the hydrodynamics and combustion equations in a homogenously and non-homogeneously - gaseous, laminar environment. It is investigated how linear variation of flame speed can affect the flame acceleration mechanism. Theory also validated by means of computational simulations. This work is supported by the Alpha Foundation for the Improvement of Mine Safety and Health as well as West Virginia University’s Program to Stimulate Competitive Research (PSCoR) and West Virginia University’s Senate Award for Research and Scholarship.

Sectioning of Potential Explosion Domains to Reduce the Overall Severity of a Vapor Cloud Explosion

Medium scale vapour cloud explosion experiments demonstrated that the severity of a vapour cloud explosion (VCE) can be reduced substantially by initiating counter fires within a vapour cloud as soon as a developing flame can be detected within the vapour cloud. For instance, experiments with two simultaneous ignitions at opposite sides of the used symmetrical test rig resulted in explosion pressures which were reduced by a factor of three to five compared to single point ignition at one side.A later re-analysis of the test findings drew the attention to a flame acceleration mechanism, which had been known before, but its contribution to the severity of a VCE had not been fully appreciated. The generally accepted theory is that flame acceleration occurs as the flame passes obstacles. In addition to that, the contribution of the expanding combustion gas has been found to play a paramount role as well.A big part of the strong reduction of the explosion severity with two-point ignition could be related to the fact that the two developing flames were acting against each other, creating a kind of expansion barrier against each other. This prevented the expanding combustion gas to push into the rig, which otherwise would have added to the flame speed.In the past, walls in a congested area had been assumed to increase the severity of a VCE. The test findings suggest, however, that barriers could be implemented in a way such that they slow down the acceleration of a flame front.It is expected that such barriers can be effective in particular when they are installed perpendicular to the anticipated direction of flame front acceleration. Process equipment is typically installed in rows 8 to 15 m wide, often extending over a length of more than 50 m, with access corridors at both sides. Horizontal equipment such as drums and heat exchangers are typically arranged perpendicular to the longitudinal direction.For such an arrangement, a flame can be assumed to accelerate preferentially in the longitudinal direction, perpendicular to the obstacles in its way, and to speed up as it passes gaps between and below equipment, pushed through the gaps by the expanding gas behind. By closing such gaps or by installing barriers, the longitudinal hot gas expansion could be partly suppressed and its contribution to the flame speed would be reduced substantially. In addition, the barriers would force the hot gas to vent towards the uncongested space aside and above the equipment and they would force the flame front to “take a detour” around the barriers. Together, these effects would reduce the burning rate.Hence, properly arranged barriers are expected to subdivide larger congested domains into smaller explosion cells, where less severe explosions occur. Because of the time needed for the flames to proceed from one cell to another, the pressure waves from these cells would be spread out over time, resulting in a lower overall explosion pressure, but continuing over a longer time period.

Effect of pipe configurations on flame propagation of hydrocarbons–air and hydrogen–air mixtures in a constant volume

It is commonplace in industrial installations to have different piping arrangements for the efficient transport of substances/materials. However, the processing industry has raised some major concerns in terms of safety, due to the accidental gas explosions that have occurred frequently and caused serious damage. It is the aim of this study to comprehensively analyse the governing factors involved in flame propagation inside different pipe configurations. This research investigates confined pipe explosions using straight, 90-degree bending, and tee-junction pipes with different obstacle placements. Hydrogen-, ethylene-, propane- and natural gas–air mixtures, over a range of concentrations (equivalence ratio, Ф = 0.6–1.4) have been used. The results show that, while there is no significant difference in the maximum pressure and rate of pressure rise in both tee-pipe arrangements investigated, the bending pipe consistently produces the worst set of results in terms of maximum pressure and flame speed in gas explosions, involving the most reactive mixtures. In addition, the detailed records of pressure traces and blast waves show that the duration of flame acceleration, the flame direction and the initial ignition point depend on the tee junction placement along the pipe length, resulting to different overall profile of the flame acceleration mechanism.

The acoustic–parametric instability for hydrogen–air mixtures

Acoustic–parametric instabilities are a significant acceleration and self turbulization mechanism which may increase noticeably the propagation velocity of flames. Therefore, the acoustic–parametric instabilities for H2–air mixtures at normal conditions have been investigated. The simplified analytical model proposed by Bychkov as well as the numerical solutions of the Searby and Rochwerger formulation were taken into account. The growth rate of the instabilities and the influence of different fuel concentrations and sound frequencies on the existence of spontaneous transition from the acoustic to the parametric instability were analyzed. The existence of a wavenumber range in which flames will be unstable for all intensities of sonic perturbations with adequate frequencies was postulated as a consequence of analytic investigation. This constitutes a significant flame acceleration mechanism with major impact on stability and flame development phenomena.

Flame acceleration and explosion safety applications

Accidental explosions of flammable gases and reactive gas mixtures remain a significant concern in process industries. The present paper reviews the basic mechanism of Flame Acceleration (FA), the results of recent studies on FA, and their application to explosion safety. A short overview of the physical phenomena involved in FA is followed by the description of FA and flame propagation regimes in smooth tubes, obstructed channels, unconfined and semi-confined mixtures with or without congestion. A framework is summarized that may be used to evaluate the potential for FA and the onset of detonation. Advances made over recent years in the understanding of FA are discussed. These advances include: new theoretical models that address various aspects of the phenomena involved in FA, high resolution numerical simulations and new detailed experimental studies. A combination of the results of these studies is shown to allow for a significant improvement of our ability to address practical problems. Areas where additional research is required to improve reliability of predictions of FA for industrial safety applications are also discussed.

The flame-acceleration mechanism and transition to detonation of a hydrogen-oxygen mixture in a channel

The flame-acceleration mechanism and transition to detonation of a hydrogen-oxygen mixture in a channel