Self-Generated Acceleration of Confined Deflagrative Flame Fronts∗

Leisenheimer, Bert; Leuckel, Wolfgang

doi:10.1080/00102209608951976

Cited by 13 publications

(9 citation statements)

References 16 publications

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“…Also, a wrinkled exothermic propagating front generates some fluid dynamic diturbances which in turn change the flame propagation speed. These disturbances (termed flame generated turbulence) add onto the incoming turbulence and one can define an "effective turbulence intensity" [26] that determines the flame structure. Leisenheimer and Leuckel [27] were able to measure this effective intensity in a premixed flame propagating radially.…”

Section: Resultsmentioning

confidence: 99%

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Characteristics of a subgrid model for turbulent premixed flames

Chakravarthy

Menont

1997

33rd Joint Propulsion Conference and Exhibit

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A modified version of the linear eddy model (LEM) for subgrid combustion is developed and used for studying the properties of turbulent premixed flames in the core region of Couette flow. The handling of the burning (diffusion/reaction) and specie transport, in this new approach, is fully deterministic. The model is, therefore, found to predict the correct laminar flame speed in the limit of zero turbulence. The effect of three dimensional eddies on scalar fields at the subgrid scales is modeled using a stochastic Lagrangian rearrangement procedure. The derivation of this procedure from the inertial range scaling laws necessitates a calibration procedure since the numerical values of the constants in these laws are unknown. The present LEM approach relates the constant needed to the coefficient of eddy viscosity that is evaluated in a LES, under the assumption of constant turbulent Prandtl and Schmidt numbers. The new approach is found to predict the turbulent flame speed with fair amount of accuracy. The chemistry is modeled using a self propagating scalar field (G-equation) approach and within the limitations of this model, LEM is found to capture the right trends in evolution of flame structure, effects of heat release and turbulence. The encouraging results obtained here warrant further research into extending this subgrid model for cases of finite rate chemistry and inclusion of thermodiffusive mechanisms such as the Lewis number effects.

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Section: Resultsmentioning

confidence: 99%

“…Bradley et al [25] in their survey of available of experimental results for characterizing turbulent flame speed against inflow turbulence, found it necessary to consider the dimensionless Karlovitz stretch factor as a relevant parameter. It is a measure of chemical time against the eddy time and is given as [26]:…”

Section: Resultsmentioning

confidence: 99%

Characteristics of a subgrid model for turbulent premixed flames

Chakravarthy

Menont

1997

33rd Joint Propulsion Conference and Exhibit

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“…The pressure data acquisition rate was 20 kHz. To avoid variations in the burning rate induced by the temperature and pressure rise during the explosion, the measurements were restricted to the "pre-pressure period," during which the pressure rise did not exceed 0.2p 0 , consistently with other similar measurements [9][10][11][12]. A pressure increase above 0.2p 0 was achieved (under present conditions) when the flame radius reached approximately half of the bomb radius, r sch ≈ 10 cm, and was about double the radius of the optical access windows.…”

Section: Apparatus Experimental Procedure and Data Interpretationmentioning

confidence: 99%

“…The turbulence in such a bomb is a good approximation to ideal homogeneous and isotropic conditions, and the method is a wellestablished means to obtain burning rates and flame speeds under both laminar and turbulent conditions [8][9][10][11][12][13]. The bomb was equipped with pressure transducers mounted flush with the wall.…”

Section: Apparatus Experimental Procedure and Data Interpretationmentioning

confidence: 99%

Experimental studies of the role of chemical kinetics in turbulent flames

Burluka

Griffiths

Liu

et al. 2009

Combust Explos Shock Waves

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Flames of di-t-butyl-peroxide (DTBP) decomposition in a 0.376DTBP + 1.0N 2 mixture are studied in laminar and turbulent media. The observed values of unstretched laminar burning velocity are in reasonable agreement with the value obtained from the Zel'dovich-Semenov-Frank-Kamenetsky theory. Turbulent explosions in this particular mixture are characterized by a number of features that are believed to be common for all developing turbulent flames and have relevance to spark-ignition engine combustion of lean mixtures. Flame propagation is unsteady and is characterized by a mass burning rate that increases in time. The rate of the flame acceleration varies from one explosion to another. If the burning rate is related to the average flame radius, however, it exhibits much smaller variations. This phenomenon bears a striking resemblance to cycle-to-cycle variations in a spark-ignition engine. Comparisons of the present results with mixtures of significantly different composition, chemical kinetics, and exothermicity, but with similar laminar flame speed and Lewis number show that the data obtained in closed-volume explosions are in good agreement if the unsteady character of the flame is taken into account. The differences in details of the kinetic mechanisms and thermochemistry appear to be responsible for the flame behaviour only near the limit of extinction by turbulence.

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“…It includes rapid combustion reactions when the methane/air mixture is ignited by an unexpected energy release, such as sparks, electrical arc, or lightning in a confined space. A transition from laminar to turbulent combustion enables a positive feedback process which leads to obvious flame acceleration and extremely high blast overpressure [3][4][5]. Geometric changes on an airway could have a significant impact on the propagation of the blast-wave induced by a methane explosion.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Geometric Change Influence on Blast-Wave Propagation in Underground Airways Using a 2D-Transient Euler Scheme

et al. 2016

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Abstract:The impact of methane explosions on mining operations can never be over-emphasized. The safety of miners could be threatened and local ventilation facilities are likely to be damaged by the flame and overpressure induced by a methane explosion event, making it essential to understand the destructiveness and influence range of a specific explosion. In this paper, the attenuation effect of geometric changes, most commonly bends, obstacles, and branches, present in the way of blast-wave propagation and the capability of the selected numerical model were studied. Although some relevant experimental research has been provided, quantitative analysis is insufficient. This paper investigates the attenuation factors of seven bends, three obstacles, and two T-branch scenarios to ascertain a better insight of this potentially devastating event quantitatively. The results suggest that (1) the numerical model used is capable of predicting four of the seven validated scenarios with a relative error less than 12%; (2) the maximum peak overpressure is obtained when the angle equals 50˝for bend cases; and (3) the selected numerical scheme would overestimate the obstacle cases by around 15%.

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Self-Generated Acceleration of Confined Deflagrative Flame Fronts∗

Cited by 13 publications

References 16 publications

Characteristics of a subgrid model for turbulent premixed flames

Characteristics of a subgrid model for turbulent premixed flames

Experimental studies of the role of chemical kinetics in turbulent flames

Modeling of Geometric Change Influence on Blast-Wave Propagation in Underground Airways Using a 2D-Transient Euler Scheme

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