Fundamental flame characteristics of premixed H2–air combustion in a planar porous micro-combustor

Li, Jun; Li, Qingqing; Wang, Yuantao; Guo, Zhaoli; Li, Xueling

doi:10.1016/j.cej.2015.08.056

Cited by 123 publications

(13 citation statements)

References 38 publications

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“…Yan et al 18 studied the combustion characteristics in a micro‐combustor with both sides slitted body, and the investigations illustrated that proper reduce slit width could enlarge the recirculation zone which could increase combustion stability effectively. Li et al 19 added porous media into combustor, and the results showed that porous medium could increase the uniform distribution of temperature and hydroxide concentration which was conductive to enhance wall temperature and flame temperature. Furthermore, the catalytic reaction could increase the temperature in combustor, so as to improve the combustion efficiency, by Pan et al 20 investigation.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigations on the emitter power and energy conversion efficiency improvement of micro‐cylindrical combustor by an internal spiral fin for micro‐thermophotovoltaic systems

Zhao

Yan

et al. 2021

Int J Energy Res

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Aiming at improving the energy output and energy conversion efficiency of thermophotovoltaic systems, a micro-combustor with high and uniform outer wall temperature is desirable. Therefore, the micro-cylindrical combustor with a novel micro-spiral fin is proposed to improve the thermal performance. The effect of inlet velocities of premixed hydrogen/air, the critical design parameters of the spiral fin length (L) and the spiral fin pitch (W) on the thermal performance of the micro-cylindrical combustor are numerically investigated.Results show that micro-spiral fin is beneficial to improve the outer wall temperature value and uniformity, which can significantly increase the emitter power and energy conversion efficiency of micro-cylindrical combustor. However, the improvement of thermal performance is at the cost of higher pressure loss. Furthermore, compared with all the investigated geometrical models, the micro-cylindrical combustor with spiral fin length at the size of 14 mm and spiral fin pitch at the size of 2.355 mm obtains the best comprehensive heat transfer performance.

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Section: Introductionmentioning

confidence: 99%

Numerical investigations on the emitter power and energy conversion efficiency improvement of micro‐cylindrical combustor by an internal spiral fin for micro‐thermophotovoltaic systems

Zhao

Yan

et al. 2021

Int J Energy Res

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“…In theoretical analysis and numerical studies, the VAM is commonly applied to study porous media combustion. The VAM assumes a local thermal equilibrium between the gas and solid phases (the one-temperature model) [18,19] or allows for a thermal nonequilibrium (the two-temperature model) [15,20], which typically treats porous media as an equivalent fluid with similar thermophysical properties, and pore-scale geometric characteristics lumped into the equivalent fluid. The simplicity of the calculation model and lower computational expense of the VAM provide a foundation for understanding the global fluid flow and heat recirculation characteristics in porous media.…”

Section: Introductionmentioning

confidence: 99%

Fundamental Numerical Analysis of a Porous Micro-Combustor Filled with Alumina Spheres: Pore-Scale vs. Volume-Averaged Models

Wang

et al. 2021

Applied Sciences

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Inserting porous media into the micro-scale combustor space could enhance heat recirculation from the flame zone, and could thus extend the flammability limits and improve flame stability. In the context of porous micro-combustors, the pore size is comparable to the combustor characteristic length. It is insufficient to treat the porous medium as a continuum with the volume-averaged model (VAM). Therefore, a pore-scale model (PSM) is developed to consider the detailed structure of the porous media to better understand the coupling among the gas mixture, the porous media and the combustor wall. The results are systematically compared to investigate the difference in combustion characteristics and flame stability limits. A quantified study is undertaken to examine heat recirculation, including preheating and heat loss, in the porous micro-combustor using the VAM and PSM, which are beneficial for understanding the modeled differences in temperature distribution. The numerical results indicate that PSM predicts a scattered flame zone in the pore areas and gives a larger flame stability range, a lower flame temperature and peak solid matrix temperature, a higher peak wall temperature and a larger Rp-hl than a VAM counterpart. A parametric study is subsequently carried out to examine the effects of solid matrix thermal conductivity (ks) on the PSM and VAM, and then the results are analyzed briefly. It is found that for the specific configurations of porous micro-combustor considered in the present study, the PSM porous micro-combustor is more suitable for simplifying to a VAM with a larger Φ and a smaller ks, and the methods can be applied to other configurations of porous micro-combustors.

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“…Li et al. 25 observed that by adding the porous medium to micro-combustor, the thermal transport and flame stability were improved. Wan et al.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigations on the liftoff velocity of H₂-air premixed combustion in a micro-cylindrical combustor with gradually changed section area

Naeemi

Hashemi

2020

Proceedings of the Institution of Mechanical Engineers, Part C:

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Sustaining and stabilizing flames are crucial issues in micro-combustion. In some micro-electro-mechanical systems such as the micro-thermophotovoltaic system, the flame should be formed in the combustion chamber, not outside it (combustion without liftoff). So, study of the liftoff phenomenon is important and vital in these systems. The aim of this study is to evaluate effect of changing combustor section area on the critical liftoff velocity in a micro-cylindrical combustor. For this purpose, the critical liftoff velocities are numerically identified for four combustor configurations (convergent, divergent, convergent-divergent and divergent-convergent combustion chamber). Premixed mixture of hydrogen-air has been used as reactants for the current investigation. Turbulence model implemented in this paper is RNG k-epsilon and combustion reaction was modeled with 10 species and 21 steps scheme using Eddy Dissipation Concept model. Two non-dimensional numbers d1/d2 (inlet to outlet diameter ratio) and d1/d3 (inlet to throat diameter ratio) are defined. For d1/d2 > 1.0, the combustion chamber is convergent, otherwise it is divergent. When d1/d3 > 1.0, the micro combustor is convergent-divergent and for d1/d3 < 1.0, the micro combustor is divergent-convergent. The results indicate that with increasing d1/d2, the liftoff occurs in a lower inlet flow velocity. With varying d1/d3, from 0.71 (2.0/2.8) to 1.0 (2.0/2.0), the liftoff velocity is reduced. Based on the numerical results, it can be said that the use of convergent and convergent-divergent combustion chamber decreases liftoff velocity. Meanwhile, the combustor with diverging and diverging-converging structure can enhance liftoff velocity. In the same condition, critical liftoff velocity of divergent-convergent micro combustor is the highest among all cases and this configuration is appropriate for Micro Electro-Mechanical Systems that work with high inlet velocity.

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Fundamental flame characteristics of premixed H2–air combustion in a planar porous micro-combustor

Cited by 123 publications

References 38 publications

Numerical investigations on the emitter power and energy conversion efficiency improvement of micro‐cylindrical combustor by an internal spiral fin for micro‐thermophotovoltaic systems

Numerical investigations on the emitter power and energy conversion efficiency improvement of micro‐cylindrical combustor by an internal spiral fin for micro‐thermophotovoltaic systems

Fundamental Numerical Analysis of a Porous Micro-Combustor Filled with Alumina Spheres: Pore-Scale vs. Volume-Averaged Models

Numerical investigations on the liftoff velocity of H₂-air premixed combustion in a micro-cylindrical combustor with gradually changed section area

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Fundamental flame characteristics of premixed H2–air combustion in a planar porous micro-combustor

Cited by 123 publications

References 38 publications

Numerical investigations on the emitter power and energy conversion efficiency improvement of micro‐cylindrical combustor by an internal spiral fin for micro‐thermophotovoltaic systems

Numerical investigations on the emitter power and energy conversion efficiency improvement of micro‐cylindrical combustor by an internal spiral fin for micro‐thermophotovoltaic systems

Fundamental Numerical Analysis of a Porous Micro-Combustor Filled with Alumina Spheres: Pore-Scale vs. Volume-Averaged Models

Numerical investigations on the liftoff velocity of H2-air premixed combustion in a micro-cylindrical combustor with gradually changed section area

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Numerical investigations on the liftoff velocity of H₂-air premixed combustion in a micro-cylindrical combustor with gradually changed section area