Ignition Regions of Hydrocarbons.

Townend, D. T. A.

doi:10.1021/cr60069a005

Cited by 55 publications

(12 citation statements)

References 13 publications

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“…Cool flames have long been considered a key process responsible for engine knock and are also an important phenomenon for fire safety [1,2,3,4,5,6]. Since the first discovery of cool flames two centuries ago [7,8], extensive efforts have been made to observe cool flames by using various flame geometries including heated surfaces and heated burners [8, 9 , 10 , 11 ], stirred reactors [12,13,14], heated flow reactors [1,8,15,16,17], rapid compression machines [18], counterflow flames [19], droplets [6,20,21], and plasma-assisted flames [22,23]. Despite that many of the observed cool flames were oscillatory, transient, and strongly affected by flame-surface interaction, insights into cool flame spectroscopy, negative temperature coefficient (NTC) chemistry, heat release, and the cool flame peninsula in the temperature/pressure domain were obtained [12,14].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations of premixed cool flames of dimethyl ether/oxygen mixtures

Reuter

Won

2015

Combustion and Flame

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The formation and dynamics of premixed cool flames are numerically investigated by using a detailed kinetic mechanism of dimethyl ether mixtures in both freely-propagating and stretched counterflow flames with and without ozone sensitization. The present study focuses on the dynamics and transitions between cool flames and high temperature flames. The impacts of mixture temperature, inert gas temperature, and ozone concentration on low temperature ignition, cool flame formation, and flammable regions of different flame regimes are investigated. For the freely-propagating flames, three different flame structures (high temperature flames, double flames, and cool flames) are found. The present study shows that the flammability limit of dimethyl ether is significantly extended by the appearance of cool flames and that the conventional concept of the flammability limit of a high temperature flame ought to be reconsidered. Furthermore, the results demonstrate that the cool flame propagation speed can be significantly higher than that of near-limit high temperature flames and that ozone addition dramatically accelerates the formation of cool flames at low temperatures and extends the flammability limit. A schematic of a modified flammability limit diagram including both high temperature flames and cool flames is proposed. For stretched counterflow flames, the results also show that multiple flame regimes exist with and without ozone addition. It is demonstrated that at the same mixture enthalpy, ozone addition kinetically extends the cool flame extinction limit to a higher stretch rate. Moreover, with ozone addition, two different cool flame transition regimes: a low temperature ignition transition and a direct cool flame transition without an ignition limit at higher temperature, are predicted. The present results suggest that cool flames can be an important combustion process in affecting flammability limits and flame regimes as the mixture temperature, turbulent mixing, and radical production/recirculation are increased. The results also provide guidance in observing self-sustaining premixed cool flames in experiments.

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Section: Introductionmentioning

confidence: 99%

Numerical simulations of premixed cool flames of dimethyl ether/oxygen mixtures

Reuter

Won

2015

Combustion and Flame

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“…1-холодное пламя, 2-горячее пламя дом 12 , Нейманом 21 и Кэйном 22 . Собственно взрыву в этом случае предшествует образование холодного пламени, дающего продукты неполного окисления углеводорода.…”

Section: повышение давления (е-/)unclassified

Самовоспламенение И Сгорание В Газах

Sokolik¹

1940

Usp. Fiz. Nauk

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Чрезвычайное многообразие явлений сгорания и значение их для важнейших областей современной техники вызвали к жизни мощный поток исследований -экспериментальных и теоретических, пытаю-щихся дать объективное физико-химическое описание различных типов горения. Наиболее актуальной и в то же время наиболее сложной задачей является нахождение связи между протеканием различных явлений сгорания (например, самовоспламенения, распространения пламени, детонации) и кинетикой химических процессов (т. е. слож-»лной цепи окислительных реакций), лежащих в основе всякого явле-ния сгорания и предшествующих возникновению пламени. В этом Цд направлении сделаны только первые шаги, большей частью лишь Д \ ставящие проблему исследования и намечающие его пути, но еще чрезвычайно далекие от таких теоретических обобщений, которые • дают возможность предвычисления, хотя бы для простейших случаев, например, для определения расчетом температуры, предельного дав-ления или задержки самовоспламенения, скорости распространения пламени, детонационных пределов и т. п. при любых заданных физико-химических условиях. Создание общей теории сгорания затрудняется не только слож-ностью явления, связанного с влиянием одновременно и чисто физи-ческих факторов (теплопередачи и гидродинамики) и химизма пред-пламенных процессов, но и с современным состоянием самой кине-тики химических реакций.Несмотря на успехи в развитии этой области физической химии, особенно в разработке общей теории цепных реакций, мы до сих пор принуждены пользоваться более или менее гипотетическими схемами, даже при рассмотрении простейших химических систем, как Н 2 -f-О 2 или СН 4 -j-O 2 . Рассмотрим в качестве примера одну из схем, дающую последовательность элементарных реакций для сго-рания метана, предложенную Семеновым 2 и Норричем 2 . Реакционную цепь по этой схеме начинает реакция молекул СН 4 с атомным кислородом (что, следовательно, предполагает предвари-тельную диссоциацию молекул кислорода на атомы):CH 4 +-i0 2 -CH 2 + H 2 O.

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“…In previous papers , 1966, studies have been reported of the influence of pressure, temperature, fu e l: oxidant ratio and the nature, shape and extent of the surface of the containing vessel on the ignition behaviour of w-heptane + oxygen + inert gas mixtures at temperatures from 440 to 650 °C. The chemical nature of the fuel is of course also an im portant factor determining the tendency to ignite, and studies have been reported of the spontaneous ignition of a wide variety of hydrocarbon fuels, some of which are simple and others relatively complex (see, for example, Townend 1937;Sokolik 1963;Fish 1968a). H itherto, however, relatively little attention has been paid to the ignition characteristics of binary mixtures of pure hydrocarbons (see, for example, Voinov, Skorodelov & Sokolov 1964).…”

Section: Introductionmentioning

confidence: 99%

The spontaneous ignition of mixtures of n -heptane and 1-heptene in oxygen

Cullis

Fish

Gibson

1969

Proc. R. Soc. Lond. A

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Studies of the ignition in oxygen of binary mixtures of n -heptane and 1-heptene at temperatures below 400°C show that under all conditions investigated both hydrocarbons are consumed during ignition. However, below ca . 300°C, where 1-heptene is considerably less reactive than n -heptane, the alkene is not involved in the process leading to ignition and the ignitability of mixtures is controlled effectively by the concentration of the alkane. In contrast, above 300 °C, 1-heptene is at least as ignitable as n -heptane and the alkene appears to contribute to the process leading to ignition. This shows that, although at relatively high temperatures conjugate alkenes maybe among the principal intermediates involved in the ignition of alkanes, this is not the case at lower temperatures. Here, the reaction between heptyl radicals and oxygen is additive leading to the formation of the corresponding heptylperoxy radicals and ignition then results from further reactions of these latter radicals. Comparison of the results obtained in stainless steel and vitreous vessels shows that the nature of the surface has little effect on limiting ignition pressures but does affect the multiplicity of cool flames. It thus appears that the surface exerts a considerable influence on the course of the reaction following the passage of a cool flame but not on the processes leading to the first cool flame and to ignition.

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Ignition Regions of Hydrocarbons.

Cited by 55 publications

References 13 publications

Numerical simulations of premixed cool flames of dimethyl ether/oxygen mixtures

Numerical simulations of premixed cool flames of dimethyl ether/oxygen mixtures

Самовоспламенение И Сгорание В Газах

The spontaneous ignition of mixtures of n -heptane and 1-heptene in oxygen

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