Effect of diluents of various chemical nature on the flammability limits of gas mixtures

Azatyan, V. V.; Shebeko, Yu. N.; Bolod’yan, I. A.; Navtsenya, V. Yu.

doi:10.1007/s10573-006-0105-8

Cited by 11 publications

(6 citation statements)

References 11 publications

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“…Note that, according to published data, 3,11,12 the activation energy of the reaction of hydrogen atoms with the molecules of active additives is much lower than that corresponding to the chain-branching step H + O 2 ® O + OH. 4 Thus, utilizing the narrow-reaction-zone model, one may consider a termination reaction by an inhibitor as temperature independent.…”

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confidence: 74%

“…One promising solution to such a problem is maintaining the safety of hydrogen production, storage and transportation through employing small quantities of chemically active additives (inhibitors). [1][2][3] Therefore, obtaining key parameters, which determine critical conditions of ignition and hydrogen flame propagation in the presence of these additives, is important.…”

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confidence: 99%

“…4 Experimental data 3,11,12 [Figures 1(a) and 2(a)] have been processed for a number of inhibitors, and the results are shown in Figures 1(b) and 2(b) in the [In] 0,FPL -u 2 T b 2 /[O 2 ] 0,FPL coordinates. In order to construct straight lines for the corresponding inhibitors on the basis of equation (3), we used the following effective values of reaction rate constants for a hydrogen atom and an inhibitor molecule: for CHF 3 , 0.1×10 -11 ; for C 2 F 4 Br 2 , 0.23×10 -11 ; for hexene, 0.47×10 -11 [ Figure 1(b)], for ethanol, 0.93×10 -12 ; for n-butanol, 0.27×10 -11 , for prop-2-en-1-ol, 0.45×10 -11 cm 3 molec -1 s -1 [ Figure 2(b)].…”

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confidence: 99%

“…The narrow-reaction-zone model used in this work implies that the action of a chemically active additive is determined by the reaction-chain termination by the molecules of the additive in a pre-flame zone. Thus, Influence of inhibitors on FPL in hydrogen-air mixtures at atmospheric pressure: (a) experimental data,3 flame propagation does not occur to the right of each curve and occurs to the left of each curve; Influence of alcohols and C 2 F 4 Br 2 on FPL in hydrogen-air mixtures at atmospheric pressure: (a) experimental data, 11,12 flame propagation does not occur to the right of each curve and occurs to the left of each curve; (1) ethanol, (2) C 2 F 4 Br 2 , (3) n-butanol, (4) isopropanol and (5) prop-2-en-1-ol; (b) the data from Figure 2(a) calculated using equation (3) for ethanol, n-butanol and prop-2-en-1-ol.…”

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confidence: 99%

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Concentration limits of combustion in rich hydrogen–air mixtures in the presence of inhibitors

Рубцов

Seplyarskii

2010

Mendeleev Communications

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confidence: 74%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Concentration limits of combustion in rich hydrogen–air mixtures in the presence of inhibitors

Рубцов

Seplyarskii

2010

Mendeleev Communications

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“…Such a mechanism is quite viable, though it is fraught with diffi culties of comparing theoretical results with experimental data. The fact that the branching-chain mechanism dominates over the thermal one in mixture combustion was indicated by experimental data obtained on oxygen-hydrogen mixtures in [9,10]. These data were the basis for the conclusion on the secondary role of the thermal factor in the occurrence of the concentration limit in slow burning of a mixture resulting in the suggestion of the mechanism underlying the stopping of a branching reaction with involvement of the primary components of a reaction mixture [1,11].…”

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Thermal Nature of Concentration Limits of Combustion

Сабденов

Baitasov

2015

J Eng Phys Thermophy

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An explanation is proposed for the concentration limits of slow combustion of gas mixtures due to the diffusionalthermal instability of a fl ame and the leading role of the thermal effect of mixture combustion. Basic to this explanation are the following experimental facts obtained for a wide class of mixtures: the concentration limits of slow combustion of a mixture and of its detonation are closely coinciding and depend strongly on the stoichiometric composition of mixture; there is an approximate symmetry relation between the upper and lower combustion limits. It is shown that the fl ame temperature of gas mixtures depends on their stoichiometric composition and that as their stoichiometric relation deviates from unity, the state of mixture combustion approaches the stability threshold beyond which a stationary fl ame cannot exist.Introduction. The concentration limit of combustion of a mixture with stoichiometric composition is manifested as a sudden disappearance of a fl ame when the concentration of a combustible (or of an oxidant) reaches its maximum or minimum value [1]. Despite the great practical importance of this phenomenon, it has not yet found any satisfactory theoretical explanation.At the present time several theories have been advanced that explain the existence of the combustion concentration limit and that can be subdivided into two classes. In the models falling into the fi rst class, the concentration limit is reached through the heat losses from the fl ame zone, with these losses being due to radiation, molecular transfer, and convection. The second class consists of models according to which the mixture combustion concentration limit ensues on violation of the balance between the branching and breaking of the chains of a corresponding chemical reaction and of the balance between heat and mass transfer, as well as at a great difference between the diffusion coeffi cients of the atoms, radicals, and molecules participating in the chemical reaction. Despite the abundance of various explanations for the existence of the combustion limit, none of the theories developed so far has gained wide acceptance. Theory of the Combustion Concentration Limit.The assumption on the occurrence of the mixture combustion concentration limit due to the loss of heat by radiation was made by D. B. Spalding [1], Ya. B. Zel′dovich, and V. V. Voevodskii [2]. Subsequently this idea underwent development in the works of A. I. Rozlovskii [3]. According to the radiative mechanism of the mixture combustion concentration limit, which in many ways is similar to the mechanism underlying the onset of gas combustion limit in narrow tubes [4], the extinction of fl ame in the course of mixture combustion occurs when the fl ame temperature is decreased by a value equal to N. N. Semenov′s interval. The rate of fl ame decreases in this case by a factor of e 1/2 (e ≈ 2.72) compared to the value corresponding to mixture combustion under adiabatic conditions. The theory of the occurrence of the mixture combustion concentration limit d...

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