• Journal of the Korean Society of Combustion
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• v.2 no.1
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• pp.1-8
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• 1997

Premixed combustion within porous ceramic media is numerically studied to understand burning characteristics and to find best configurations for burner implementations. Among many parameters, critical to burner performance, flame location and extinction coefficient are selected as major parameters for this study. The flame structure and burner performance with respect to these two parameters are observed. In the study, it is found that the location of flame is the most important in porous burner operation since it affects the rate of heat transfer and flame structure. Stability of the flame within the porous ceramic burner is discussed with respect to the flame location. It is found that to obtain high radiative output, the flame should be located downstream section of the burner. But the flame is to be unstable at most of downstream section except near the exit plane. To overcome this problem, new porous ceramic burner, using different ceramic properties in one burner instead of single property ceramic, is made and tested. With a combination of ceramics of high extinction coefficient at upstream and another material of low extinction coefficient at downstream of the burner, the flame can be stabilized at wider region of the burner with higher radiative output compared to the original burner configuration.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.4
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• pp.518-524
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• 1997

Experimental studies on combustion phenomena within a porous ceramic burner are reported. Main interest of the present work is to investigate fundamental flame behaviors and their effects on the burner operation. Due to high thermal capacity of the porous ceramic materials, the response of flame to burning condition changes is slow and thus to have a stabilized flame is quite difficult and takes much time. It is found that the temperature profile obtained at downstream of the flame zone is not much sensitive to the movement of flame and the speed of flame movement is less than 0.1 mm/sec for the conditions tested. With the premixed LPG/air flame imbedded within the porous ceramic burner, stable combustion regions and unstable combustion regions leading to blowoff or flashback phenomena are observed and mapped on flow velocity versus equivalence ratio diagram. For the development of burner operation technique which is more practical and safe, intermittent burning technique, where the fuel or/and air is supplied to the burner intermittently, is proposed as one of the flame control methods for the porous ceramic burner and tested in this study. Through the experiment, it is realized that the proposed method is acceptable in respect to burner performance and give much flexibility in the operation of porous ceramic burner.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.162-172
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• 1998

A numerical study of premixed combustion within a porous ceramic burner (PCB) is performed to understand flame behavior with respect to various model parameters. Basic flame structure within the porous ceramic burner and species profiles such as NO and CO are examined. Sensitivity analysis of flame speed, gas and solid temperature, NO and CO emission from the burner with respect to reaction steps and various physical properties of the ceramic material is applied to find the most significant parameters in selection of porous materials for the porous ceramic burner. Effects of thermal conductivity, extinction coefficient and scattering albedo on the burner characteristics are studied through the sensitivity analysis. The results of sensitivity study reveal the order of importance in ceramic material properties to get suitable burner performance. Scattering albedo, which governs the ratio of absorbed energy by the ceramic material to total radiative energy transferred, is one of the most important parameters in the material properties since it affects the actual absorbed radiation rate and thus it largely affects the flame structure. Through the study, it is found that the sensitivity study can be used to estimate the flame behavior within the porous ceramic burner more effectively.

• Coupled systems mechanics
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• v.1 no.3
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• pp.285-295
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• 2012

In this paper, two types of porous burners with radial and axial flow have been modeled numerically and compared. For this purpose, governing equations were solved one-dimensionally for methane-air premix gas. The mechanism used in simulating combustion phenomenon was 15 stage reduced mechanism based on GRI3.0. In order to compare the two burners, the inlet flow rate and fuel-air ratio have been assumed equal for the two burners. The results of the study indicated that reduction in speed and increase in cross-section area in the direction of flow have a considerable influence on the behavior of radial burner in comparison to axial burner. Regarding temperature distribution inside the burner, it was observed that the two above mentioned factors can be influential in temperature of flame propagation region. Also, regarding distribution of CO and NO emission, the results indicate that the porous radial burner has lower emissions in comparison to the axial once. The output radiative heat transfer efficiency of the two burners was also compared and in this case also even the radial porous burner was found to be preferable.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.398-403
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• 2000

Experimental study on the porous ceramic burner for oil burning has been performed. Temperature profile of the combustor and CO and NOx emission have been obtained for with and without porous ceramic plate. It is found that very uniform and high temperature region with porous ceramic plate can be realized due to high radiation emission from the plate and also obtained lower CO and soot particulate emission, when compared to the conventional burner. When this burning method is applied to conventional boiler of small heating capacity, it is found that near 6 and 7 percent increase in thermal efficiency could be obtained without a proper calibration for optimization.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.559-567
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• 1995

The combustion process within a porous inert medium (PIM) burner is numerical studied. A detailed chemical reaction scheme including thermal and prompt NO$_{x}$ reactions is used to predict the formation and destruction of pollutants such as NO$_{x}$ and CO. The reaction paths for NO$_{x}$ formation are divided to quantify the amount of NO$_{x}$ formed through thermal NO$_{x}$ reaction or through prompt NO$_{x}$ reaction. Emission index is calculated to compare the actual mass of NO$_{x}$ or CO produced through the combustion of unit mass of fuel. It is found NO formation in PIM burner is confined in flame zone and formation is suppressed due to heat loss at down-stream of the flame. Higher production of NO through prompt NO reaction path is observed due to the higher concentration of fuel derivative species and its higher diffusion at flame front. For all equivalence ratios, CO emission within PIM burner is lower than that from the one-dimensional freely-propagating flame. PIM burner flame has better NO$_{x}$ emission index from .psi. = 0.75 to .psi. = 1.1. to .psi. = 1.1.

• Journal of the Korean Society of Combustion
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• v.6 no.1
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• pp.29-35
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• 2001

The surface flames in porous ceramic burner are experimentally characterized to investigate the effects of equivalence ratio and firing rates. The results show that the surface flames are classified into green, red radiant and blue surface flame as decrease of equivalence ratio. And each flame is maintained very stably and shows the same flame characteristics at any orientation of ceramic burner. Particularly the blue surface flame was found to be very stable at very lean equivalence ratio at 200 to $800\;kw/m^2$ firing rates. And the exhausted NOx was analysed to find out which flame has lower NOx emission. The blue surface flame showed the lowest NOx emission regardless of the location of burner since it sustained very stable at lean mixture ratio.

• Journal of Power System Engineering
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• v.20 no.4
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• pp.12-18
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• 2016

Typical boiler system consists of combustion chamber and heat exchanger in one housing, therefore the size of boiler system is large and the heat exchanging efficiency becomes low. At these boiler systems, because the combustible mixture fires as free flame in the combustion chamber, consequently the combusted hot gas heats the heat exchanger only as conductive and convective heat transfer. The present Porous Ceramic Burner concept is that combustion process is occurred at the gaps of the porous ceramic materials, and the heat exchanger is placed in the same porous materials. Therefore we can reduce the boiler size, and we can also use radiative heat transfer from ceramic material with conductive and convective heat transfer from combusted gas throwing the porous materials. The purpose of this study is to search the flame stability ranges at different fuel flow rate and excess air ratio burning in the $Al_2O_3$ ceramic balls. We found out the stable excess air ratio range on given combustion intensity. And we can get clean porous ceramic combustion results compared with free flame.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.19-25
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• 2006

Energy efficient and low pollution combustion systems the use gaseous fuels have been in great demand in recent year. Radiant burner in many different forms are emerging as very desirable combustion systems for same reason. Porous radiant burners are used in drying, preheating and curing, and in other type of materials processing and manufacturing processes. However, little knowledge is available about the operating characteristics and the structure of flames in porous ceramic fiber radiant burners. The objective of the present work is to investigate the global performance characteristics of the ceramic fiber burner. A detailed study which includes the spectral intensity, gas temperature, radiation efficiency and global pollutant emissions. Another objective is to study the flame structure of the ceramic fiber burner by measuring the local gas temperature. The results indicate that ceramic fiber burner do offer a 19-44% gain in radiant efficiency. The ceramic fiber burner exhibit significant spectral intensity peaks in the band at $2.0-2.5{\mu}m$. The local temperature distribution inside the mat and near the mat surface as a function of the equivalence ratio can be reasonably interpreted by the relation of the heat balance in the mat and movement of the reaction zone. Nox emission from ceramic fiber burner is less than 25ppm throughout the operating range.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.157-159
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• 2014

This article describes an investigation of basic combustion characteristics of radiant burner with various firing rate and equivalence ratios in porous metal. As a main experimental condition, firing rates and equivalence ratios each were adjusted from 204 to $408kW/m^2$ and 0.6 to 1.3. The purpose of this study is to investigate radiation efficiency using two experiment methods. The first way is to calculate the radiation efficiency by measuring the temperature of the burner surface, and the second is to compute the radiation efficiency by measuring the radiation intensity of the burner surface with a radio meter. The value of the radiation efficiency did not exactly match in the two cases. But we figured out that in accordance with increasing heat power, radiation efficiency was decreased. And additional complementary experiment on the relationship between these values is needed.