The use of expanding spherical flames to determine burning velocities and stretch effects in hydrogen/air mixtures

Dowdy, David R.; Smith, David Barton; Taylor, Simon; Williams, Alan

doi:10.1016/s0082-0784(06)80275-4

Cited by 271 publications

(121 citation statements)

References 19 publications

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“…This may be seen most clearly in Fig. 1, where the predictions of the San Diego mechanism are compared with the most recent accurate experiments [3][4][5][6]. Although the computations, described previously [2], are based on one particular chemical-kinetic mechanism, with other mechanisms the direction of the discrepancies is the same, and the magnitudes of the discrepancies are comparable or larger.…”

Section: Introductionmentioning

confidence: 81%

“…[13,14], as useful reviews [15,16] describe in greater detail. The papers reporting the burning-velocity measurements specifically comment on observed cell formation for spherical flames at sufficiently lean conditions [3,5,6], but the flames in the steady counterflow experiment were said to be very flat [4] and yet produced velocities in agreement with the other measurements. Although the strain in the counterflow is known to suppress visible cells, it nevertheless may not be sufficient to eliminate transverse preferential diffusion that may result in similar burning velocities.…”

Section: Introductionmentioning

confidence: 99%

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A hypothetical burning-velocity formula for very lean hydrogen–air mixtures

Williams¹,

Grcar²

2009

Proceedings of the Combustion Institute

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Very lean hydrogen-air mixtures experience strong diffusive-thermal types of cellular instabilities that tend to increase the laminar burning velocity above the value that applies to steady, planar laminar flames that are homogeneous in transverse directions. Flame balls constitute an extreme limit of evolution of cellular flames. To account qualitatively for the ultimate effect of diffusive-thermal instability, a model is proposed in which the flame is a steadily propagating, planar, hexagonal, close-packed array of flame balls, each burning as if it were an isolated, stationary, ideal flame ball in an infinite, quiescent atmosphere. An expression for the laminar burning velocity is derived from this model, which theoretically may provide an upper limit for the experimental burning velocity.

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Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

A hypothetical burning-velocity formula for very lean hydrogen–air mixtures

Williams¹,

Grcar²

2009

Proceedings of the Combustion Institute

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“…The constant-pressure spherical flame method involves capturing Schlieren images of an expanding spherical flame and calculating the instantaneous flame speed and stretch from radiustime data [27,28]. Most studies employ the relations given by Strehlow and Savage [30] for an unconfined outwardly propagating spherical flame, in which the burned gas is assumed to come to rest after crossing the flame and the flame is taken to be infinitesimally thin:…”

Section: Effect Of Cylindrical Confinement On Laminar Flame Speed Meamentioning

confidence: 99%

“…There are various methods found in the literature for relating stretch rate and stretched flame speeds such that the fundamental mixture parameters, the unstretched laminar burning velocity, s u o , and Markstein length, L u , can be extracted as described in Refs. [27,[31][32][33][34]. The present study uses a commonly employed relation, first postulated by Markstein [31]: …”

Section: Effect Of Cylindrical Confinement On Laminar Flame Speed Meamentioning

confidence: 99%

Reduced and Validated Kinetic Mechanisms for Hydrogen-CO-sir Combustion in Gas Turbines

Ju¹,

Dryer²

2009

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Rigorous experimental, theoretical, and numerical investigation of various issues relevant to the development of reduced, validated kinetic mechanisms for synthetic gas combustion in gas turbines was carried out -including the construction of new radiation models for combusting flows, improvement of flame speed measurement techniques, measurements and chemical kinetic analysis of H 2 /CO/CO 2 /O 2 /diluent mixtures, revision of the H 2 /O 2 kinetic model to improve flame speed prediction capabilities, and development of a multi-time scale algorithm to improve computational efficiency in reacting flow simulations. Executive SummaryRigorous experimental, theoretical, and numerical investigation of various issues relevant to the development of reduced, validated kinetic mechanisms for synthetic gas combustion in gas turbines was carried out -including the construction of new radiation models for combusting flows, improvement of flame speed measurement techniques, measurements and chemical kinetic analysis of H 2 /CO/CO 2 /O 2 /diluent mixtures, revision of the H 2 /O 2 kinetic model to improve flame speed prediction capabilities, and development of a multi-time scale algorithm to improve computational efficiency in reacting flow simulations.An accurate spectral dependent radiation model is developed to predict flame speed and flammability of H 2 /CO/CO 2 /H 2 O/Air mixtures. The results showed that radiation reabsorption significantly extended the flammability limits. It was also demonstrated that accurate prediction of coal syngas flammability is not possible without appropriate consideration of radiation absorption by CO 2 and H 2 O.Methodologies to improve flame speed measurement were developed by experimental and theoretical investigation of the effect of non-spherical (i.e. cylindrical) bomb geometry on the evolution of outwardly propagating flames and the determination of laminar flame speeds. The cylindrical chamber boundary modifies the propagation rate through the interaction of the wall with the flow induced by thermal expansion across the flame (even with constant pressure), which leads to significant distortion of the flame surface for large flame radii. It was determined that these departures from the unconfined case, especially the resulting non-zero burned gas velocities, can lead to significant errors in flame speeds calculated using the conventional assumptions, especially for large flame sizes.The methodology to estimate the effect of nonzero burned gas velocities is applied to correct the flame speed for non-zero burned gas speeds, in order to extend the range of flame radii useful for flame speed measurements. Under the proposed scaling, the burned gas speed can be well approximated as a function of only flame radius for a given chamber geometry -i.e. the correction function need only be determined once for an apparatus and then it can be used for any mixture. Results indicate that the flow correction can be used to extract flame speeds for flame radii up to 0.5 times the wall radius wi...

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“…engines and gas turbine combustors is the knowledge of laminar combustion properties: they offer the basis for modelling and simulation of flame-turbulence interaction. Data on the combustion properties of pure gaseous fuels are widely available in the literature [1][2][3][4][5][6][7][8][9][10][11][12], but hardly in a systematic form; moreover, data for multi-component fuels at high pressure are even scarcer: filling this gap is the scope of the Device for Hydrogen-Air Reaction Mode Analysis (DHARMA) project, aiming at generating a comprehensive and coherent grid of data on the combustion properties of CH 4 and H 2 , obtained in conditions as close as possible to those of actual engines.…”

Section: Introductionmentioning

confidence: 99%

Burning Behaviour of High-Pressure CH4-H2-Air Mixtures

Moccia

D'Alessio

2013

Energies

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Experimental characterization of the burning behavior of gaseous mixtures has been carried out, analyzing spherical expanding flames. Tests were performed in the Device for Hydrogen-Air Reaction Mode Analysis (DHARMA) laboratory of Istituto Motori-CNR. Based on a high-pressure, constant-volume bomb, the activity is aimed at populating a systematic database on the burning properties of CH 4 , H 2 and other species of interest, in conditions typical of internal combustion (i.c.) engines and gas turbines. High-speed shadowgraph is used to record the flame growth, allowing to infer the laminar burning parameters and the flame stability properties. Mixtures of CH 4 , H 2 and air have been analyzed at initial temperature 293÷305 K, initial pressure 3÷18 bar and equivalence ratio  = 1.0. The amount of H 2 in the mixture was 0%, 20% and 30% (vol.). The effect of the initial pressure and of the Hydrogen content on the laminar burning velocity and the Markstein length has been evaluated: the relative weight and mutual interaction has been assessed of the two controlling parameters. Analysis has been carried out of the flame instability, expressed in terms of the critical radius for the onset of cellularity, as a function of the operating conditions.

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The use of expanding spherical flames to determine burning velocities and stretch effects in hydrogen/air mixtures

Cited by 271 publications

References 19 publications

A hypothetical burning-velocity formula for very lean hydrogen–air mixtures

A hypothetical burning-velocity formula for very lean hydrogen–air mixtures

Reduced and Validated Kinetic Mechanisms for Hydrogen-CO-sir Combustion in Gas Turbines

Burning Behaviour of High-Pressure CH4-H2-Air Mixtures

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