Detailed measurement and assessment of laminar hydrogen jet diffusion flames

Abstract.A zero-dimensional kinetic model has been developed to investigate the coupled electron and heavy-particle kinetics in Ar-O 2 surface-wave microwave discharges generated in long cylindrical tubes, such as those launched with a surfatron or a surfaguide. The model has been validated by comparing the calculated electron temperature and species densities with experimental data available in the literature for different discharge conditions. Systematic studies have been carried out for a surfacewave discharge generated with 2.45 GHz field frequency in a 1 cm diameter quartz tube in Ar-O 2 mixture at 0.5-3 Torr pressures, which are typical conditions found in different applications. The calculations have been performed for the critical electron density n e =3.74×10 11 cm −3 . It has been found that the sustaining electric field decreases with Ar percentage in the mixture, while the electron kinetic temperature exhibits a minimum at about 80%Ar. The charged and neutral species densities have been calculated for different mixture compositions, from pure O 2 to pure Ar, and their creation and destruction processes have been identified. The O 2 dissociation degree increases with Ar addition into O 2 and dissociation degrees as high as 60% can be achieved. Furthermore, it has been demonstrated that the dissociation degree increases with the discharge tube radius, while decreases with the atomic surface recombination of O-atoms. The density of O − negative ions is very high in the plasma, the electronegativity of the discharge can be higher than 1, depending on the discharge conditions. §

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“…Note that τ The diffusion coefficients D i of species i in the mixture were calculated from the simplified Wilke's formula, as given in [59],…”

Section: Model Descriptionmentioning

confidence: 99%

Theoretical insight into Ar–O₂surface-wave microwave discharges

Kutasi

Guerra²,

Sá

2010

J. Phys. D: Appl. Phys.

104

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“…Unlike in case of the hydrocarbon microflame, a hydrogen microflame showed unique behavior at near extinction limit. Cheng, et al investigated the characteristics of the small-jet diffusion flames of hydrogen (Cheng, et al, 2005;Cheng, et al, 2006b). Discussions were made based on a comparison between experimental results using a UV Raman/LIPF system and numerical simulation results.…”

Section: Non-premixed Combustion 331 Lower-limiting Flame Behaviormentioning

confidence: 99%

Progress in small-scale combustion

Nakamura

Gao

Matsuoka

2017

JTST

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This article briefly reviews the recent works related to small-scale combustion and its potential impact into combustion science and engineering is presented. Followed by a simple description of the scale effect on combustion to highlight its "unique" feature, past related works are then summarized. The impact of heat recirculation appearing in combustion systems, which is the most prominent feature of a micro-or small-scale combustion system, is focused upon and is understood that exactly the same strategy promising better combustion performance is confirmed irrespective of flame type (either premixed or non-premixed). With respect to this, paying attention to the entire combustor design, to optimize within the target working range is a crucial matter when micro-scale combustion is adopted. Potential subjects to be covered to further promote these aspects in this field are then presented.

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“…Cheng et al [13] investigated the effects of thermal diffusion in laminar jet diffusion flames using CFD-ACE with Reynolds number (Re) ¼ 30 and 330. Comparisons of computed temperature and species concentration profiles of the flames with experimental measurements are in good agreement.…”

Section: Cavity Typementioning

confidence: 99%