Impact of co-flow air on buoyant diffusion flames flicker

Darabkhani, Hamidreza Gohari; Wang, Q.; Chen, L.; Zhang, Y.

doi:10.1016/j.enconman.2011.04.011

Cited by 25 publications

(4 citation statements)

References 27 publications

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“…Current understanding of the influence of pressure on instability behaviour and thermo-physical properties of sooty diffusion flames is still limited. [5][6][7] The recent studies 8,9,10 also show that the increase in co-flow air velocity can modify the dynamics of a flickering methane diffusion flame to such an extent that the flame oscillations are completely suppressed (stabilised). In order to explain the physical interpretation of this interesting phenomenon, high speed photography and photomultipliers, high speed schlieren and Particle Imaging Velocimetry (PIV) have been employed in order to investigate the flame structure and its interaction with the flow field.…”

Section: Introductionmentioning

confidence: 89%

“…Schlieren and PIV systems can help to visualize the outer flame vortex dynamics and their interactions with the visible flame and also hot plume of gases above the flame. 9,10 Accurate and reliable measurements of soot temperature and distribution in the flame by non-intrusive means are highly desirable to achieve in-depth understanding of combustion and pollutant formation processes. Consequently, a variety of optical laser methods such as Rayleigh Scattering, Mie Scattering and Particle Image Velocimetry (PIV) for flow visualisation in the reaction zone and combustion environment.…”

Section: Introductionmentioning

confidence: 99%

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Study of the Flame Structure and Dynamics Using Non-intrusive Combustion Diagnostic Techniques

Darabkhani

Oakey

Yang

et al. 2013

43rd Fluid Dynamics Conference

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This work investigates the implementation of non-intrusive optical combustion diagnostic techniques to study the influence of elevated pressures, on the flame structure and dynamics of the gaseous co-flow diffusion flames. Photomultipliers, high speed photography accompanied with digital image processing techniques have been used to study the structure of stable and unstable flame characteristics. Methane and Ethylene laminar flames have been studied at the same flow rates of fuel and co-flow air (0.15 l/min and 15 l/min, respectively) and at elevated pressures of up to 10 bar. It has been observed that the flame properties respond very sensitively to both the fuel type and pressure. In the Ethylene flame as the pressure is increased, the flame diameter decreased at all flame heights i.e. the average cross-sectional area of the flame shows an inverse dependence on pressure. This flame however, remains stable (non-flickering) within the entire pressure range. In contrast, Methane flame started to flicker at the pressures above 2 bar with one dominant frequency and as many as six harmonic modes. It was found that the pressure enhances the outer vortices to induce stronger flame oscillations.

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Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Study of the Flame Structure and Dynamics Using Non-intrusive Combustion Diagnostic Techniques

Darabkhani

Oakey

Yang

et al. 2013

43rd Fluid Dynamics Conference

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“…As to the effect of coflow, the forced convection is enhanced with higher coflow air velocity. This also promotes the air mixing and mitigates the relative importance of buoyancy effect [37] , resulting in the decrease in the flame length and the difference in the flame lengths between the normal-and micro-gravities. However, even though the difference of the flame length in Fig.…”

Section: Flame Length Liftoff Height and Blowoutmentioning

confidence: 99%

Blowout of non-premixed turbulent jet flames with coflow under microgravity condition

Wang

et al. 2019

Combustion and Flame

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The blowout behavior of non-premixed turbulent coflow jet flames under microgravity environment was studied experimentally by utilizing a 3.6 s drop tower. Variations of flames leading to liftoff as well as blowout were examined by varying the coflow velocity and compared with those obtained under the normal gravity condition. A modeling work was conducted to incorporate the effects of the gravity (buoyancy) and coflow velocity on blowout behavior. Major findings include: (1) the flame length in microgravity was longer than that in normal gravity and decreased with increasing coflow velocity. The flame in microgravity showed more intense yellow luminosity with larger sooting zone; (2) the flame liftoff height increased with increasing coflow velocity in both gravity levels. The flame base was closer to the burner in microgravity as compared with that in normal gravity; (3) the blowout velocity in microgravity was appreciably larger than that obtained in normal gravity; and (4) a physical model based on Damköhler number was developed by using similarity solutions to characterize the differences in the blowout limits considering both the coflow and gravity (buoyancy) effects. The proposed model can successfully predict the experimental data. This work provided new data and basic scaling analysis for blowout limit of non-premixed turbulent jet flames considering both the coflow and gravity (buoyancy) effects.

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“…In the absence of wind conditions, the oscillation of the flame can be described by a periodic variation of the flame height in the vertical direction. Under the action of wind, the influence of the external air force and its own buoyancy not only changes the shape of the flame (including height, area, and tilt angle) [20,21], but also the vortex formed at the periphery of the flame. The shear layer vortex generated by the cross wind was mainly caused by the formation of Kelvin-Helmholtz instability [7], i. e., when air and flame of these two different density fluids met on the interface, the difference of speed caused a pressure difference, then forming torque and growing into a vortex.…”

Section: Turbulent Fluctuation Of Flamementioning

confidence: 99%

Association of flame-oscillation frequency under cross wind diffusion

Lou

Zeng

et al. 2019

THERM SCI

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Turbulent flame-oscillation frequency and combustion efficiency are the important parameters in combustion. It is a useful study to judge combustion efficiency by intuitive flame frequency. Based on a combustion wind tunnel experimental setup , the variation law of combustion flame-oscillation frequency and combustion efficiency using external wind speeds was studied via the color flames image sequence of oil pan combustion and flue gas composition. The oscillation frequency was calculated with the upper edge of the fire plume which recorded flame image sequence using a high-speed video, combined the MATLAB image processing technique. The combustion efficiency was calculated combined with the C and H element mass of the liquid fuel in the oil pool and CO 2 and H 2 O concentrations in the flue gas. The results show that the oscillation frequency of the flame revealed a tendency to increase followed by a decrease with increasing wind speed, while the overall trend of combustion efficiency increased first and then decreased. The combustion efficiency could be judged by observing the oscillation frequency of the flame image. In addition, the combustion efficiency may ensure in right way when the turbulence oscillation frequency of the oil pan flame ranged between 15 Hz and 18 Hz.

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Impact of co-flow air on buoyant diffusion flames flicker

Cited by 25 publications

References 27 publications

Study of the Flame Structure and Dynamics Using Non-intrusive Combustion Diagnostic Techniques

Study of the Flame Structure and Dynamics Using Non-intrusive Combustion Diagnostic Techniques

Blowout of non-premixed turbulent jet flames with coflow under microgravity condition

Association of flame-oscillation frequency under cross wind diffusion

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