• Title/Summary/Keyword: Combustion Kinetics

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Evolution, Fields of Research, and Future of Chemical-Looping Combustion (CLC) process: A Review

  • Shahrestani, Masoumeh Moheb;Rahimi, Amir
    • Environmental Engineering Research
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    • v.19 no.4
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    • pp.299-308
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    • 2014
  • This study presents a review on Chemical looping combustion (CLC) development, design aspects and modeling. The CLC is in fact an unmixed combustion based on the transfer of oxygen to the fuel by a solid oxygen carrier material avoiding the direct contact between air and fuel. The CLC process is considered as a very promising combustion technology for power plants and chemical industries due to its inherent capability of $CO_2$ capturing, which avoids extra separation costs of the of $CO_2$ from the rest of flue gases. This review covers the issues related to oxygen carrier materials. The modeling works are reviewed and different aspects of modeling are considered, as well. The main drawbacks and future research and prospects are remarked.

A Numerical Analysis of the Characteristics with High Temperature Air Combustion in Counterflow Diffusion Flame (대향류 확산화염의 고온공기 연소특성에 관한 수치해석)

  • Cho, Eun Seong;Kobayashi, Hideaki;Chung, Suk Ho
    • Journal of the Korean Society of Combustion
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    • v.8 no.4
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    • pp.9-14
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    • 2003
  • High temperature air combustion technology has been utilized by using preheated air over 1100 K and excessive exhaust gas recirculation. Numerical analysis was performed to investigate the combustion characteristics with high temperature deficient oxygen air combustion by adopting a counterflow as a model problem accounting for detailed chemical kinetics. Methane($CH_4$) was used as a test fuel and calculated oxidizer conditions were low temperature high oxygen (300K, $X_{O2}=0.21$) and high temperature low oxygen (1300K, $X_{O2}=0.04$) conditions. The latter case showed that the flame temperature is lower than the former case and its profile showed monotonic decrease from oxidizer to fuel side, without having local maximum flame temperature at high stretch rate. Also, heat release rate was one order lower and it has one peak profile because of low oxygen concentration and heat release rate integral is almost same for stretch rate. High temperature low oxygen air combustion shows low NO emission characteristics.

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A Study on the Detailed Diesel Surrogate Chemical Mechanism for Analysis of HCCI Engine (HCCI 엔진 해석을 위한 Diesel Surrogate 반응 기구에 관한 연구)

  • Lee, Won-Jun;Lee, Seung-Ro;Lee, Chang-Eon
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.4
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    • pp.64-71
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    • 2011
  • Homogeneous charge compression ignition (HCCI) was the best concept able to provide low NOx and PM in diesel engine emissions. This new alternative combustion process was mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engine. In this paper, detailed kinetic reaction mechanisms of diesel surrogate was investigated to understand the diesel HCCI engine combustion. It was tested two existing mechanisms and two new mechanisms for the comparison of experimental result. The best mechanism for diesel surrogate was suggested through this comparison.

Catalytic Activity of Commercial Metal Catalysts on the Combustion of Low-concentration Methane (저농도 메탄 연소에서 상용 금속촉매의 활성)

  • Lee Kyong-Hwan;Park Jae-Hyun;Song Kwang-Sup
    • Journal of Korean Society for Atmospheric Environment
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    • v.21 no.6
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    • pp.625-630
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    • 2005
  • This study was focused on the catalytic activity for the combustion of low-concentration methane using various commerical catalysts (six transition metal catalysts in Russia and one rare earth metal (Honeycomb) catalyst in Korea). Catalytic activity was strongly influenced by the type and loading content of metal supported in catalyst. Catalytic performance showed the highest activity in Honeycomb catalyst including rare earth metal, which was the most expensive catalyst, while the next was the catalyst supported Cu with high content (AOK-78-52) and also that supported Cr and Co (AOK-78-56). However, both AOK-78-52 and AOK-78-56 catalysts that were very cheap had lower activation energy than Honeycomb catalyst. In the economical field, both AOK-78-52 and AOK-78-56 catalysts with transition metals showed a good alternative catalyst on the combustion of methane.

EFFECT OF ADDITIVES ON THE PYROLYSIS AND COMBUSTION OF CELLULOSE (셀룰로오스의 열분해에 대한 첨가제의 영향)

  • 심철호;박영수
    • Journal of the Korean Society of Tobacco Science
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    • v.7 no.2
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    • pp.169-178
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    • 1985
  • In the previous paper, the kinetics of cellulose were described. In this study, the ability of some additives to act as a flame promoter for cellulose was investigated using dynamic thermogravimetry and differential scanning calorimetry. The treated cellulose was thermally decomposed through the two model as previously noted with the untreated cellulose. The first step was associated with the flaming combustion of volatile material released in the fraunentation process and the second was caused by the glowing combustion of carbonaceous residue. The first group of the additives, which could be divided into two groups by the pyrolytic mechanism of cellulose, appeared to catalyze the fragmentation, maximizing the degradation to produce tarry products, with gaseous flammable substrate. The heat evolved in flaming combustion mode was increased significantly by the treatment of the cellulose retained 1-5% of the first group additives.

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Numerical Analysis of Effect of Inhomogeneous Pre-mixture on Pressure Rise Rate in HCCI Engine by Using Multizone Chemical Kinetics (화학반응수치해석을 이용한 HCCI기관의 예혼합기의 성층화성이 연소시의 압력 상승률에 미치는 영향)

  • Lim, Ock-Taeck
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.5
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    • pp.449-456
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    • 2010
  • The HCCI engine is a prospective internal combustion engine with which high diesel-like efficiencies and very low NOx and particulate emissions can be achieved. However, several technical issues must be resolved before HCCI engines can be used for different applications. One of the issues concerning the HCCI engine is that the operating range of this engine is limited by the rapid pressure rise caused by the release of excessive heat. This heat release is because of the self-accelerated combustion reaction occurring in the engine and the resulting engine knock in the high-load region. The purpose of this study is to evaluate the role of thermal stratification and fuel stratification in reducing the pressure rise rate in an HCCI engine. The concentrations of NOx and CO in the exhaust gas are also evaluated to confirm combustion completeness and NOx emission. The computation is carried out with the help of a multizone code, by using the information on the detailed chemical kinetics and the effect of thermal and fuel stratification on the onset of ignition and rate of combustion. The engine is fueled with dimethyl ether (DME), which allows heat release to occur in two stages, as opposed to methane, which allows for heat release in a single stage.

Characteristics of the Ignition Delay for Hydrocarbon Fuels by Reduced Chemical Kinetics Modeling (축소 화학반응 모델링에 의한 탄화수소 연료의 점화지연 특성)

  • 김형욱;배상수;민경덕
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.4
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    • pp.44-49
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    • 2001
  • Reduced chemical kinetics mechanism has been derived, which can be applicable for autoignition model of hydrocarbon fuels, and contains 23 reactions and 18 species. The present model is validated with the experimental data, where the ignition delays of several hydrocarbon fuels, such as n-heptane, i-octane, n-decane and DME(dimethylether) are measured as equivalence ratios are varied. Especially, the effects of different fuels on ignition delays can be explained by changing the rate constants of three reactions among the present model. As a result, the proposed model can be applicable to two stage ignition model of Diesel combustion.

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Kinetics analysis of energetic material using isothermal DSC (등온 DSC를 이용한 고에너지 물질의 정밀 반응 모델 기법 개발)

  • Kim, Yoocheon;Park, Jungsu;Kwon, Kuktae;Yoh, Jai-ick
    • 한국연소학회:학술대회논문집
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    • 2015.12a
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    • pp.219-222
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    • 2015
  • The kinetic analysis of energetic materials using Differential Scanning Calorimetry (DSC) is proposed. Friedman Isoconversional method is applied to DSC experiment data and AKTS software is used for analysis. The frequency factor and activation energy are extracted as a function of product mass fraction. The extracted kinetic scheme does not assume multiple chemical steps to describe the response of energetic materials; instead, multiple set of Arrhenius factors are used in describing a single global step. The proposed kinetic scheme has considerable advantage over the standard method based on One-Dimenaionl Time to Explosion (ODTX). Reaction rate and product mass fraction simulation are conducted to validate extracted kinetic scheme. Also a slow cook-off simulation is implemented for validating the applicability of the extracted kinetics scheme to a practical thermal experiment.

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Combustion Characteristic of Paper Sludge Using TGA Reactor (열중량 반응기를 이용한 제지슬러지의 연소 특성)

  • Yook, Chan-Nam;Kim, Jung-Soo;Han, Kwang-Soo
    • Journal of environmental and Sanitary engineering
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    • v.18 no.3 s.49
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    • pp.48-58
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    • 2003
  • To obtain the preliminary design data for combustion of paper sludges, decomposition characteristics and combustion kinetics of paper sludges reactor have been determined in a TGA reactor. Also, the combustion characteristics of paper sludges have been determined in a fluidized bed reactor. The data obtained from the TGA reactor indicate that dewatering of paper sludge is terminated at temperature below 130${\circ}$C. With heating rate of 20${\circ}$C/min, combustion is terminated at temperature below 340${\circ}$C .The combustion rate is found to be first order with respect to temperature and oxygen concentration. Activation energies for paper wastes are found to be 570, 700, 2600, 4600 Kcal/mole, respectively. The calcination conversions were investigated with the operating temperature and residence time. In this investigation, it was found that calcination conversion was affected by the operating temperature and residence time. The optimum conditions of operating temperature and mean residence time were 850${\circ}$C and 6 minutes of respectively.

The Research about Engine Speed change Effect on HCCI Engine Combustion by Numerical Analysis (엔진회전속도의 변화가 HCCI엔진연소에 미치는 영향에 관한 수치해석 연구)

  • Lim, Ock-Taeck
    • Journal of ILASS-Korea
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    • v.16 no.3
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    • pp.126-133
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    • 2011
  • In HCCI Engine, combustion is affected by change of compression speed corresponding to engine speed. The purpose of this study is to investigate the mechanism of influence of engine speed on HCCI combustion characteristics by using numerical analysis. At first, the influence of engine speed was shown. And then, in order to clarify the mechanism of influence of engine speed, results of kinetics computations were analyzed to investigate the elementary reaction path for heat release at transient temperatures by using contribution matrix. In results, as engine speed increased, in-cylinder gas temperature and pressure at ignition start increased. And ignition start timing was retarded and combustion duration was lengthened on crank angle basis. On time basis, ignition start timing was advanced and combustion duration was shortened. High engine speed showed higher robustness to change of initial temperature than low engine speed. Because of its high robustness, selecting high engine speed was efficient for keeping stable operation in real engine which include variation of initial temperature by various factors. The variation of engine speed did not change the reaction path. But, as engine speed increased, the temperature that each elementary reaction would be active became high and reaction speed quicken. Rising the in-cylinder gas temperature of combustion start was caused by these gaps of temperature.