Regime diagrams and characteristics of flame patterns in radial microchannels with temperature gradients

Fan, Aiwu; Minaev, Sergey; Kumar, Sudarshan; Liu, Wei; Maruta, Kaoru

doi:10.1016/j.combustflame.2007.10.015

Cited by 88 publications

(28 citation statements)

References 31 publications

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“…8, from which we can see that there is some leakage of unburned fuel. This was verified by the measurement of exhaust gas conducted in [23,24]. The gas temperature distributions at the same moments are given in Fig.…”

Section: Numerical Simulationsupporting

confidence: 59%

“…Before fuel supply, wall temperature profiles were created by using cold airflow. This approach was also employed in the series of previous studies [17][18][19][20][21]23,24]. Figure 4 shows the typical wall temperature profiles at an inlet airflow velocity of 4.0 m/s.…”

Section: Experimental Setup and Methodsmentioning

confidence: 99%

“…Movie recordings of various flame patterns were carried out with an image-intensified high-speed video camera right after the mixture was ignited in the microchannel. Other details about the experimental method could be found elsewhere [19][20][21]23,24].…”

Section: Experimental Setup and Methodsmentioning

confidence: 99%

“…In addition to conventional stable circular flame, various non-stationary flame patterns, such as rotating pelton-like flame (this is termed since flame shape resembles a Pelton-wheel [19][20][21]), traveling flame, and so forth, were observed. More recently, Fan et al [23,24] extended the mixture equivalence ratio to a much wider range. Some new flame patterns were observed and the regime diagrams of those flame patterns in the radial microchannels with a gap width of 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mm were drawn based on their experimental findings.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Experimental and numerical investigations of flame pattern formations in a radial microchannel

Fan

Minaev

Sereshchenko

et al. 2009

Proceedings of the Combustion Institute

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Section: Numerical Simulationsupporting

confidence: 59%

Section: Experimental Setup and Methodsmentioning

confidence: 99%

Section: Experimental Setup and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experimental and numerical investigations of flame pattern formations in a radial microchannel

Fan

Minaev

Sereshchenko

et al. 2009

Proceedings of the Combustion Institute

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“…Fan et al [63][64][65] experimentally studied premixed methane/air flame behaviours in a radial channel between two parallel circular quartz plates with the gap of 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mm and the diameter of 50 mm. External heating was applied to obtain positive temperature gradients along flow direction.…”

Section: Fundamental Studiesmentioning

confidence: 99%

Micro/mesoscale combustion based portable power generating system

Kang¹

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Micro/mesoscale combustion-driven power generation is a promising alternative to replace traditional batteries for powering small scale electronics owing to its much higher energy densities. However, the considerable heat losses from the combustor walls due to the dramatically increased surface-tovolume ratio, as well as the short flow residence time at small scales pose a technical challenge in stabilising the flame inside the micro/mesoscale combustor. On the other hand, the significantly enhanced flame-wall thermal coupling at small scales can also lead to some unique flame characteristics.Recently, solid state power conversion of the heat released in the micro/mesoscale combustor such as thermoelectric (TE) and thermophotovoltaic (TPV) has been favoured over traditional power conversion methods such as micro-turbines. This is due to the excessive mechanical and viscous losses that rotating machinery suffers from upon miniaturisation.One of the main aims of this thesis is to perform numerical simulations to investigate the fundamental aspects of micro/mesoscale combustion, such as micro-flame behaviours of propagation and stabilisation, the conditions under which flame dynamics occur and the choices that suppress them. A set of modelling techniques that gives guidelines and practices for performing the time-accurate micro/mesoscale combustion simulations has been developed through investigation. Knowledge on standard and well-accepted numerical methods in literature are collected in a cohesive document. The less well-established modelling choices have been thoroughly evaluated and discussed.Using the developed numerical models, the effects of hydrogen and carbon monoxide addition on premixed methane/air flame dynamics is investigated. Results show that the flame instabilities which exist in pure methane/air flames could be effectively suppressed via a small amount of additives. Deep understanding of the underlying physics and chemistry has been gained. The effects of wall temperature profiles on the simulated micro-flame behaviours are also studied. The role of the combustion heat release and the gas-solid heat transfer in determining the micro-flame propagation speed is identified.Experimental works are also carried out, towards a full system demonstration for micro-power generation. The focus is placed on the "wall thermal engineering" on the improvement of the combustor performance and power output. The thermally-orthotropic pyrolytic graphite for the combustor wall material is explored. Compared to an isotropic material of stainless steel, a widened flame stability limit with pyrolytic graphite is demonstrated. Moreover, a uniform and moderate temperature distribution over the combustor surface is achieved, which is favourable for thermoelectric power conversion applications. Meanwhile, a novel, compact mesoscale thermophotovoltaic power generating system using a combination of porous media combustion and a simple band-pass filtering method is developed. The use of the porous media effectively enh...

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Combustion characteristics of hydrogen‐air mixture in a radial micro combustor for using in thermophotovoltaic devices

2021

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Requirement of a fast rechargeable and powerful energy source for micro scale devices leads to increase attentions to various micro combustors for usage as heat source in micro thermophotovoltaic devices. Meanwhile, extracting as much thermal energy as possible from chemical energy of fuel by testing a variety of shapes of micro combustion chambers is at the heart of micro combustion subject. Present research has been purposed to find out performance and feasibility of a radial micro combustion chamber by numerical study of combustion characteristics of H 2 -air pre-mixture and calculation of emitter and total efficiency of the system. Governing equations are considered three-dimensional, incompressible, and steady state for turbulent combustion. In addition, detailed kinetics of H 2 -air combustion is chosen for the combustion mechanism. Inlet velocity, equivalence ratio, and wall material properties consisting of emissivity and thermal conductivity with external thermal convection coefficient are parameters, which have been chosen for investigations. Results indicated drastic effect of inlet velocity on the location of combustion zone. In fact, increasement of the inlet velocity causes to transfer combustion zone to the wall, which leads to increase wall temperature and consequently, emitter and total efficiency of the system. Equivalence ratio has more impact on the combustion temperature. While wall thermal conductivity and wall radiation emissivity play a decisive role in the total efficiency of the system. It was founded as the wall radiation emissivity decreases, heat recirculation increases. It causes to expand high temperature zone through the fluid and wall so that the total efficiency increases.By considering the present radial micro combustion chamber as a heat source for a micro thermophotovoltaic device, it was founded that maximum total efficiency of 3.14% is accessible for the condition in which the outer wall surface has maximum average temperature. Highlights• The inlet velocity has drastic impact on the radiation heat transfer rate.• Existence of the vortexes is suitable for intensifying the reactions.• Wall thermal conductivity has maximum effect on the emitter and total efficiency.

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Regime diagrams and characteristics of flame patterns in radial microchannels with temperature gradients

Cited by 88 publications

References 31 publications

Experimental and numerical investigations of flame pattern formations in a radial microchannel

Experimental and numerical investigations of flame pattern formations in a radial microchannel

Micro/mesoscale combustion based portable power generating system

Combustion characteristics of hydrogen‐air mixture in a radial micro combustor for using in thermophotovoltaic devices

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