On the mechanism of laminar flame propagation at high pressures

Babkin, V. S.; V'yun, A. V.

doi:10.1007/bf00748973

Cited by 4 publications

(2 citation statements)

References 5 publications

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“…Experimental data on SL were collected from [9][10][11][12][13][14][15][16][17][18][19][20]. For each type of mixture an appropriate analytical function was chosen to describe dependencies of SL on hydrogen concentration ( or diluent concentration).…”

Section: Mixture Propertiesmentioning

confidence: 99%

Evaluation of limits for effective flame acceleration in hydrogen mixtures

Dorofeev

Кузнецов

Алексеев

et al. 2001

Journal of Loss Prevention in the Process Industries

105

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Results of experimental data analysis on turbulent flame propagation in obstructed channels is presented. The data cover a wide range of mixtures: H 2 /air and H2/air/steam mixtures (from lean to rich) at normal and elevated initial temperatures (from 298 to 650K) and pressures (from 1 to 3 bars); and stoichiometric H 2 /02 mixtures diluted with N2, Ar, He, and C02 at normal initial conditions. The data set chosen covers, also, a wide range of scales exceeding two orders of magnitude. It is shown that basic flame parameters, such as mixture expansion ratio 0', Zeldovich number ß, and Lewis number Le, can be used to estimate a priori a potential for effective flame acceleration for a given mixture. The critical conditions for effective flame acceleration are suggested in the form f3 > l3*(Le, ß) on the basis of experimental correlations. Critical l3*-values are found tobe in the range from 3.5 to 4.0, for stable flames (ß(Le-I)> -2). For unstable flames (ß(Le-I)< -2), f3* is given by a function of Zeldovich number ß. The requirement of large enough mixture expansion ratio (J > l3*(Le, ß) can be used in practical applications as the necessary condition or criterion for possible development of fast combustion regimes. On this basis, limits for effective flame acceleration can be defined for hydrogen combustibles. Uncertainties in determination ofcritical f3*-values, which should be taken into account in practical applications, are discussed. 5. ZUSAMMENFASSUNG Bestimmung der Bedingungen für Flammenbeschleunigung in Wasserstoffhaitigen BrenngasenPractical applications and uncertainties 10Summary and conclusions 12References 13 NOMENCLATURE LatinA -elementary area of the flame surface;Csr -sound speed in reactants;Csp -sound speed in combustion products;d -size of orifice;Ea -effective activation energy;h -height of obstacles;L-characteristic geometrical size (e.g., obstacle spacing);Lr-integrallength scale of turbulence;Le -Lewis number;Le1-Lewis number defined by fuel diffusion coefficient in stoichiometric mixture;Leo -Lewis number defined by oxidizer diffusion coefficient in stoichiometric mixture;Mab -Markstein number defined relative to burned mixture; n1-reaction order for fuel;no -reaction order for oxidizer; R -gas constant;SL -laminar burning velocityrelative to unburned mixture;Tb -maximum flame temperature;Tu -initial mixture temperature;Un -normal burning velocity of stretched flames relative to burned mixture; UL -laminar burning velocity relative to burned mixture; a-ratio of densities of reactants and products ( expansion ratio);X-temperature diffusivity.

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Section: Mixture Propertiesmentioning

confidence: 99%

Evaluation of limits for effective flame acceleration in hydrogen mixtures

Dorofeev

Кузнецов

Алексеев

et al. 2001

Journal of Loss Prevention in the Process Industries

105

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“…Catalytic suppressants reduce concentrations of flame radicals through a regenerative cycle in which one molecule of suppressant recombines several flame radicals, whereas non-catalytic chemical suppressants reduce concentrations of flame radicals by scavenging and are generally less effective [22]. All chemical suppressants exhibit saturation effects [18,19,21] when the reduction of reactive radicals reaches an equilibrium concentration and the additional chemical agents only leads to a thermal effect [23]. CF 3 Br is a typical chemical suppressant with two chemical inhibiting moieties Br and CF 3 , of which Br moiety is a catalytic suppressant and CF 3 moiety is a non-catalytic suppressant.…”

Section: Chemical Saturation Effectivenessmentioning

confidence: 99%

Numerical Investigation of the Chemical Effect and Inhibition Effect Improvement of C3H2F3Br (2-BTP) Using the Perfectly Stirred Reactor Model

Zhang

et al. 2018

Energies

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The overall chemical rate and chemical effect of CF3Br, 2-BTP and 2-BTP/CO2 with hydrocarbon flames are calculated using the perfectly stirred reactor (PSR) model. The chemical effects of CF3Br with CH4/air flames always inhibit combustion. The chemical saturation concentration of CF3Br in stoichiometric and lean (Φ = 0.6) CH4/air flames at 298 K and 1 bar is roughly 2.5% and 0.8%, respectively. The overall chemical rate of 2-BTP with moist C3H8/air flames is always less than the uninhibited condition and fluctuates with sub-inerting agent additions. The net chemical effect variation of 2-BTP is more complicated than experimented and calculated flame speeds with 2-BTP added to lean hydrocarbon flames. There are negative chemical effects (chemical combustion effects) with certain sub-inerting 2-BTP concentrations (0.015 ≤ Xa ≤ 0.034), which result in the experimented unwanted combustion enhancement in lean moist C3H8/air flames. CO2 can obviously improve the inhibition effect of 2-BTP in lean moist C3H8/air flames, driving negative chemical effects (enhance combustion) into positive chemical effects (inhibit combustion) with lean moist C3H8/air flames. No enhanced combustion would occur with the blends (2-BTP/CO2) when CO2 addition is larger than 4% in Φ = 0.6 moist C3H8/air flames at 298 K and 1 bar.

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Zamashchikov

Bunev

2003

Combustion, Explosion, and Shock Waves

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On the mechanism of laminar flame propagation at high pressures

Cited by 4 publications

References 5 publications

Evaluation of limits for effective flame acceleration in hydrogen mixtures

Evaluation of limits for effective flame acceleration in hydrogen mixtures

Numerical Investigation of the Chemical Effect and Inhibition Effect Improvement of C3H2F3Br (2-BTP) Using the Perfectly Stirred Reactor Model

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