Topic
Diffusion flame
About: Diffusion flame is a research topic. Over the lifetime, 9266 publications have been published within this topic receiving 233522 citations.
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TL;DR: It is shown that uncertainty about mixture composition or the values of nonresonant susceptibilities of individual constituents need not have a significant effect on CARS temperature measurement.
Abstract: Experimental and theoretical investigations of N2 coherent anti-Stokes Raman scattering (CARS) thermometry in laboratory ethylene–air diffusion flames have revealed significant nonresonant susceptibility effects in fuel-rich regions of the flames. The effects appear to be due to the size of the nonresonant susceptibility for typical hydrocarbon fuels and can give rise to significant temperature errors if not accounted for. An efficient theoretical algorithm for reducing spectra affected by nonresonant interference is presented and shown to give excellent agreement with experiment. It is shown that uncertainty about mixture composition or the values of nonresonant susceptibilities of individual constituents need not have a significant effect on CARS temperature measurement.
82 citations
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TL;DR: In this article, the authors measured the laminar smoke point properties of non-buoyant flames, due to their relevance to many industrial processes where effects of buoyancy are small.
82 citations
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01 Jan 1989TL;DR: In this paper, it was shown that the fuel-rich branch necessarily extends ahead of any plane, penetrating to upstream infinity, and this corresponds to an anchored flame rather than one that is freely propagating, and appears to be a consequence of the stretch effects that are possible when Le f > 1.
Abstract: Tribrachial (three-armed) flames are generated when a premixed flame propagates into a nonuniform mixture, and consist of a fuel-rich branch joined to a fuel-lean branch, with a diffusion flame trailing from the junction (the stoichiometric point). They are important in the context of ‘laminar flamelet’ models of turbulent non-premixed flames. We provide a theoretical description of these flames, valid when the upstream concentration gradient is small. In addition, we assume that the Lewis number of the oxidizer is 1, but that of the fuel (Le f ) is greater than 1. Solutions are sought corresponding to steady, unbounded propagation into unburnt mixture, where we would expect—nominally—that all three arms of the flame trail behind the junction, so that to the left of some plane perpendicular to the oncoming flow there is everywhere no reaction. Instead, we find that the fuel-rich branch necessarily extends ahead of any plane, penetrating to upstream infinity. This corresponds to an anchored flame rather than one that is freely propagating, and appears to be a consequence of the stretch effects that are possible when Le f >1; a decrease in the mixture strength does not necessarily lead to a decrease in the local flame speed if flame curvature generates negative stretch. If we assume that extinction occurs at sufficiently low flame temperatures, the flame is bounded and our solution can be reinterpreted as a freely-propagating flame, albeit with unexpected shape.
82 citations
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TL;DR: In this article, a laminar diffusion flame of methane was investigated using time-of-flight mass spectroscopy with two-photon UV laser ionization, and polycyclic aromatic hydrocarbons (PAHs) up to 788 amu (C64H20) were detected in the combustion gases.
Abstract: A laminar diffusion flame of methane was investigated using time-of-flight mass spectroscopy with two-photon UV laser ionization. Benzenoid polycyclic aromatic hydrocarbons (PAHs) up to 788 amu (C64H20) were detected in the combustion gases. Only the most compact PAHs are formed in the flame. The observed groups of PAH peaks with 24 amu spacings belong to PAHs with constant hydrogen content and are separated by 26 amu gaps. The sequences of PAH peaks with 24 amu spacing are explained by a repetitive bay closure mechanism. The first PAH of a constant H-sequence is proposed to form by a dimerization process. The PAHs observed can be arranged in a repetitive pattern in Dias’s formula periodic system.
82 citations
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TL;DR: In this article, a detailed regime diagram for bluff-body stabilized flames is proposed for the flame lift-off and stabilization limits, where the flame structure is classified into three stable modes: recirculation zone flames, jet-dominated flames, and jet-like flames according to the velocity ratio of annular to central jets.
82 citations