The blowout mechanism of turbulent jet diffusion flames

Wu, Chia Ching; Chao, Yei Chin; Cheng, T. S.; Li, Yueh Heng; Lee, Kuo Yuan; Yuan, Tony

doi:10.1016/j.combustflame.2006.01.004

Cited by 48 publications

(36 citation statements)

References 36 publications

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“…Also, no continuous lift-off near the bluff body surface is seen before complete blow-off, consistent with experiment [15] and similar to other findings in blow-out of unconfined swirl-stabilized non-premixed flames [22]. However, this is different from the phenomenological observations of blow-out process in turbulent non-premixed jet fame, in which case the flame base is continuously pushed far from the burner and the extinction happens between the flame base and burner exit [17]. As such, the blow-off transient in Fig.…”

Section: Fig 10supporting

confidence: 90%

“…The blow-out dynamics in turbulent non-premixed jet flames have been investigated theoretically and experimentally, such as their transient behaviors and the intrinsic mechanisms [17,18]. The estimated blow-out correlations, parameterized by critical flame base locations and/or mixture flow rates, were proposed in Refs.…”

Section: Introductionmentioning

confidence: 99%

“…The estimated blow-out correlations, parameterized by critical flame base locations and/or mixture flow rates, were proposed in Refs. [17][18][19] based on the simplified theoretical models for lift-off of turbulent non-premixed jet flames [20]. The blow-out limits (i.e.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Zhang

Mastorakos

2015

Flow Turbulence Combust

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The Large Eddy Simulation (LES)/three-dimensional Conditional Moment Closure (CMC) model with detailed chemistry is applied to predict the operating condition and dynamics of complete extinction (blow-off) in swirling non-premixed methane flames. Using model constants previously selected to provide relatively accurate predictions of the degree of local extinction in the piloted jet flames Sandia D−F, the error in the blow-off air velocity predicted by LES/3D-CMC in short, recirculating flames with strong swirl for a range of fuel flow rates is within 25 % of the experimental value, which is considered a new and promising result for combustion LES that has not been applied before for the prediction of the whole blow-off curve in complex geometries. The results also show that during the blow-off transient, the total heat release gradually decreases over a duration that agrees well with experiment. The evolution of localized extinction, reactive scalars and scalar dissipation rate is analyzed. It has been observed that a consistent symptom for flames approaching blow-off is the appearance of high-frequency and high-magnitude fluctuations of the conditionally filtered stoichiometric scalar dissipation rate, resulting in an increased fraction of local extinction over the stoichiometric mixture fraction iso-surfaces. It is also shown that the blow-off time changes with the different blow-off conditions.

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Section: Fig 10supporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Zhang

Mastorakos

2015

Flow Turbulence Combust

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“…However, this method introduces error due to the inability to accurately record the changes in the flow rate at the jet exit. Wu et al (2006) studied the changes in the stoichiometric contour at the flame front using acoustic excitation to control blowout in an easily repeatable procedure. Repeatability for the current study is achieved by keeping the flow rates constant and igniting the flame at the burner.…”

Section: Methodsmentioning

confidence: 99%

Flame Propagation and Blowout in Hydrocarbon Jets: Experiments to Understand the Stability and Structure

Lyons¹

2012

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. This research supported by the U.S. Army Research Office examines a myriad of facets of lifted hydrocarbon jet flames in the presence of air co-flow. At a certain jet exit velocity, a flame will lift from the fuel nozzle and stabilize at some downstream position. The partially-premixed flame front of the lifted flame oscillates, with the oscillations becoming greater in flames stabilized further downstream. These Inventions (DD882) Scientific ProgressThe main advances in jet flame flow interaction in oblique jet/air flows, as well as flame blowout, are detailed in the attachment. blowout were compared against two parameters: nozzle angle and coflow velocity. The resulting correlations indicated that flames at more oblique angles have a greater upper stability limit and were more resistant to changes in coflow velocity. This behavior occurs due to a lower effective coflow velocity at angles more oblique to the coflow direction.Additionally, stability limits were determined for flames in crossflow and mild counterflow configurations, and a relationship between the liftoff and blowout velocities was observed.For flames in crossflow and counterflow, the stability limits are higher. Further studies may include more angle and coflow combinations, as well as the effect of diluents or different fuel types. IntroductionA multitude of studies have been performed on lifted jet flames and their behavior in various air flow configurations. In such partially-premixed flames, the characteristics of the surrounding air flow (velocity, temperature) can strongly impact the overall combustion process and the stability parameters. As fuel flows from a nozzle and mixes with the air, the fuel and oxidizer concentrations vary throughout space and time. The extent of mixing due to turbulence also changes depending on the surrounding flow. The perpetually varying concentrations help to determine the overall behavior of a flame: its shape, velocity, size, color, temperature, and composition. In parallel, the heat release serves to laminarize regions, and serves to limit reducing mixing.In particular, two important behavioral parameters are liftoff and blowout velocity.Initially, a jet flame will remain attached to the nozzle at low fuel velocities. However, at a critical jet velocity, the flame will lift off from the nozzle and stabilize at a position While jet behavior in coflow has been extensively studied, less attention has been devoted to jets in crossflow. In a review, Bandaru and Turns included a comprehensive list of all major crossflow research to date [9]. Many of the works relevant to this study were observation-based experiments performed by Kalghatgi, whosecrossflow flame experiments were conducted in a wind tunnel and involved propane, ...

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“…Burgess and Lawn [17], Brown et al [18], Dahm and Mayman [19] and Montgomery et al [20] discussed related elements of flame blowout; a recent overview of this previous research in blowout is contained in Chao et al [9]. More recently, Wu et al [21] report on lifted flames near blowout, with detailed comments on triple flames in the pulsating region, and describe a proposed mechanism of flame pulsation and blowout.…”

Section: Introductionmentioning

confidence: 99%

Observations on Jet-Flame Blowout

Moore

McCraw

Lyons

2008

International Journal of Reacting Systems

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The mechanisms that cause jet-flame blowout, particularly in the presence of air coflow, are not completely understood. This work examines the role of fuel velocity and air coflow in the blowout phenomenon by examining the transient behavior of the reaction zone at blowout. The results of video imaging of a lifted methane-air diffusion flame at near blowout conditions are presented. Two types of experiments are described. In the first investigation, a flame is established and stabilized at a known, predetermined downstream location with a constant coflow velocity, and then the fuel velocity is subsequently increased to cause blowout. In the other , an ignition source is used to maintain flame burning near blowout and the subsequent transient behavior to blowout upon removal of the ignition source is characterized. Data from both types of experiments are collected at various coflow and jet velocities. Images are used to ascertain the changes in the leading edge of the reaction zone prior to flame extinction that help to develop a physically-based model to describe jet-flame blowout. The data report that a consistent predictor of blowout is the prior disappearance of the axially oriented flame branch. This is witnessed despite a turbulent flames' inherent variable behavior. Interpretations are also made in the light of analytical mixture fraction expressions from the literature that support the notion that flame blowout occurs when the leading edge reaches the vicinity of the lean-limit contour, which coincides approximately with the conditions for loss of the axially oriented flame structure.

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The blowout mechanism of turbulent jet diffusion flames

Cited by 48 publications

References 36 publications

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Flame Propagation and Blowout in Hydrocarbon Jets: Experiments to Understand the Stability and Structure

Observations on Jet-Flame Blowout

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