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: A technique for acquiring two-dimensional soot-volume-fraction measurements in laminar flames has been demonstrated and the optical arrangement to minimize the effect of beam steering is described, which had no effect on the soot measurements in the flames examined.
Abstract: A technique for acquiring two-dimensional soot-volume-fraction measurements in laminar flames has been demonstrated. The technique provides a map of very low noise concentration over a range of wavelengths (250-1100 nm). A noise level of 0.0007 in extinction and a spatial resolution of 30-40 microm for soot concentration were achieved with an arc lamp source that was filtered to provide greater spatial coherence and a CCD detector. The broadband arc lamp source also allowed us to avoid the added noise resulting from speckle with coherent laser sources. Beam steering, due to refractive-index gradients in the flame, was measured and compared with theoretical predictions. The optical arrangement to minimize the effect of beam steering is described. As a result the beam steering had no effect on the soot measurements in the flames examined. Flame-transmission maps obtained with this system in an ethylene/air laminar diffusion flame are presented. Tomographic analysis from use of an Abel inversion of the line-of-sight data to obtain radial profiles of soot concentration is described.
186 citations
TL;DR: A recently developed laser-induced incandescence technique is used to make novel planar measurements of soot volume fraction within turbulent diffusion flames and droplet flames, finding that approximately an 80% reduction was found when the Reynolds number of the fuel jet increased from 4000 to 8000.
Abstract: A recently developed laser-induced incandescence technique is used to make novel planar measurements of soot volume fraction within turbulent diffusion flames and droplet flames. The two-dimensional imaging technique is developed and assessed by systematic experiments in a coannular laminar diffusion flame, in which the soot characteristics have been well established. With a single point calibration procedure, agreement to within 10% was found between the values of soot volume fraction measured by this technique and those determined by conventional laser scattering-extinction methods in the flame. As a demonstration of the wide range of applicability of the technique, soot volume fraction images are also obtained from both turbulent ethene diffusion flames and from a freely falling droplet flame that burns the mixture of 75% benzene and 25% methanol. For the turbulent diffusion flames, approximately an 80% reduction in soot volume fraction was found when the Reynolds number of the fuel jet increased from 4000 to 8000. In the droplet flame case, the distribution of soot field was found to be similar to that observed in coannular laminar diffusion flames.
185 citations
TL;DR: In this paper, the authors studied the characteristics of triple flames in a hydrogen-air mixing layer using direct numerical simulation with detailed chemistry and found that the triple point, defined as the location of maximum heat release, is always in the proximity of the stoichiometric mixture fraction line.
184 citations
01 Jan 1991
TL;DR: In this article, a study of carbon dioxide and oxygen addition on soot formation has been performed such that the effects of dilution, temperature and direct chemical participation have been isolated for the additives on both the fuel and oxidizer sides.
Abstract: A study of carbon dioxide and oxygen addition on soot formation has been performed such that the effects of dilution, temperature and direct chemical participation have been isolated for the additives on both the fuel and oxidizer sides. By measuring soot inception limits in the counterflow flame and integrated soot volume fractions in the coflow flame, the influence of the additives on soot inception, growth and burnout has also been ascertained. Results demonstrate that carbon dioxide, whether added to the fuel or oxidizer side, can suppress soot formation chemically. The effect of oxygen addition is more complex. When added to the fuel side of an ethylene flame, the addition leads to an abrupt increase in the inception limit, indicating that the inception chemistry has been accelerated. The addition to propane, however, is initially suppressive and results in a significant reduction in the soot inception limit which is more than can be accounted for by dilution. The addition becomes promoting as the oxygen mole fraction approaches 40%. Finally, the effect of oxygen concentration on the oxidizer side, for both ethylene and propane flames, is almost totally thermal.
183 citations
TL;DR: In this paper, the steady-state flame spread over a thermally thin solid fuel is investigated, and qualitative agreement is obtained with experimental results in the near-extinction limit region.
183 citations