Isolated stable cool flames of hydrocarbons

Ballinger, P. R.; Ryason, P. R.

doi:10.1016/s0082-0784(71)80030-9

Cited by 19 publications

(11 citation statements)

References 2 publications

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“…Ignition in such systems is often a complex, two-stage process [9] in which the heat release by the first stage, the cool flame, strongly affects the ignition timing of the second stage [10,11]. These low-temperature cool flames have also been shown to be an important influence on engine knock [12] and can extend the lean flammability limit [13][14][15]. Even in continuous combustion systems such as gas turbines, the low-temperature chemistry can significantly modify the fuel composition, which in turn may affect the turbulent burning velocity [16,17] or stabilization mechanism [18,19] of the main flame and possibly contribute to phenomena such as lean blow off [20].…”

Section: Introductionmentioning

confidence: 99%

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Reuter

Lee

Won

et al. 2017

Combustion and Flame

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The low-temperature oxidation of hydrocarbon fuels has received increasing attention as advanced engines seek to operate in less conventional combustion regimes. Large n-alkanes are a notable component of many real transportation fuels and possess strong reactivity in this important low-temperature range. These n-alkanes have been studied extensively in various canonical kinetic experiments but seldom in systems with strong coupling between lowtemperature chemistry, transport, and heat release. To address this issue, the present study investigates self-sustaining n-alkane cool diffusion flames in a counterflow burner. The extinction limits of both hot diffusion flames and cool diffusion flames are measured at atmospheric pressure for a range of n-alkanes from n-heptane to n-tetradecane. It is observed that while these fuels behave similarly for hot flames, the larger n-alkanes are substantially more reactive in the low-temperature cool flame regime. Moreover, ozone addition strongly enhances the low-temperature chemistry to the point where the differences in fuel reactivity are nearly suppressed.The experimental measurements are compared with numerical simulations employing both detailed and reduced chemical kinetic models of various sizes. Although the different kinetic models adequately predict the extinction limits of the hot flames, a large scatter is present in the model results for cool flames, and a general overprediction of the measured cool flame extinction limit is observed for all of the fuels studied. This implies that the cool flame heat release is not well agreed upon by the current chemical kinetic models, despite their capability to reproduce many homogeneous reactor experiments at low temperatures. Furthermore, it is observed that the cool flame heat release is spread over a substantial number of reactions involving large molecules, a trait that makes it particularly difficult to create reduced kinetic models that can accurately describe cool flame behavior. The results of this study suggest that the cool flame platform can provide crucial validation of the coupling between chemistry, transport, and heat release in flames at low temperatures. 2 3 4 5 6 7 8

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Section: Introductionmentioning

confidence: 99%

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Reuter

Lee

Won

et al. 2017

Combustion and Flame

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“…The main challenge in studying the dynamics of cool flames originates from the difficulty to create a stable cool flame experimentally. Efforts of previous cool flame studies have been focused on using heated surfaces and heated burners [11][12][13], jet stirred reactors [14], heated flow reactors [15,16], rapid compression machines [17], counterflow flames [5,6,[18][19][20][21], propagating flames [7,22], and droplets [3,4,23].…”

Section: Introductionmentioning

confidence: 99%

On the propagation limits and speeds of premixed cool flames at elevated pressures

2017

Combustion and Flame

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The flame speeds and propagation limits of premixed cool flames at elevated pressures are numerically modelled using dimethyl ether mixtures. The primary focus is paid on the effects of pressure, mixture dilution, computation domain, and heat loss on cool flame propagation. The results showed that cool flames exist on both fuel lean and fuel rich sides and dramatically extend the lean and rich flammability limits of conventional hot flames. There exist three different flame regimes: the hot flames, lean and rich cool flames, and double flames. A new flame flammability diagram including both cool flames and hot flames at elevated pressures is obtained. The results show that pressure significantly changes cool flame propagation and burning limits. It is found that the increase of pressure affects the propagation speeds of lean and rich cool flames differently due to the negative temperature coefficient effect. On the lean side, the increase of pressure accelerates the cool flame chemistry and shifts the transition limit of cool flame to hot flame to a lower equivalence ratio. At lower pressure, there is an extinction transition from hot flame to cool flame. However, above a critical pressure, the hot flame directly transfers to a cool flame without hot flame extinction. Moreover, increases in dilution reduce the heat release of the hot flame and promote cool flame formation. Furthermore, the results show that a smaller downstream computation domain and higher heat loss also extend the cool flame transition limit and promote cool flame formation.

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“…There are about ten works in which profiles of stable initial, final and intermediate compounds distribution have been obtained. Still less reserches are devoted to the determination and distribution of active intermediate radicals and atoms [24-341. In stabilized cool flames at the certain initial temperature and flow rate a spacing evolution of the conversion of initial, intermediat and final substances arises, that allow to measure temperatures and conduct zond samples [24,26,30 ] which are impossible under the static conditions due to extremely short duration of the process.…”

Section: Short Analytical Literature Surveymentioning

confidence: 99%

“…The stabilization of cool flames of hydrocarbons, particularly lower hydrocarbons, is possible at preliminary heating of the fuel mixture, heating value being increased at transition from butane to metane [26].…”

Section: Mb Neiman and His Co-workers [171831mentioning

confidence: 99%

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Pentan isomers compound flame front structure

Мансуров¹,

Mironenko²,

Bodikov³

et al. 1995

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as part of a collaboration with LLNL in the field of combustion chemistry. The fuels considered in this study, and the temperatures and pressures investigated, are extremely relevant to ongoing projects at LLNL related to chemistry of engine knock in spark-ignition, internal combustion engines. In the present paper, the group led by Professor Mansurov provides a review of the field of low temperature hydrocarbon oxidation and experiments carried out in the past at the Kazakh State National University. In future reports, the same group will discuss new experimental studies of oxidation under the same conditions of isomers of pentane. This work is intended to investigate the role that fuel molecular structure plays in determining knock tendency in engine combustion.

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Isolated stable cool flames of hydrocarbons

Cited by 19 publications

References 2 publications

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

On the propagation limits and speeds of premixed cool flames at elevated pressures

Pentan isomers compound flame front structure

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