• Fire Science and Engineering
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• v.13 no.1
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• pp.37-47
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• 1999

The spreading fire of very small floating particles after they are ignited is fast and t therefore dangerous. The research on this area has been limited to experiments and global simulations which treat them as dusts or gaseous fuel with certain concentration well m mixed with air. This research attempted micro-scale analysis of ignition of those particles modeling them as liquid droplets. For the beginning, the in-line array of fuel droplets is modeled by two-dimensional, unsteady conservation equations for mass, momentum, energy and species transport in the gas phase and an unsteady energy equation in the liquid phase. They are solved numerically in a generalized non-orthogonal coordinate. The single step chemical reaction with reaction rate controlled by Arrhenius’ law is assumed to a assess chemical reaction numerically. The calculated results show the variation of temperature and the concentration profile with time during evaporation and ignition process. Surrounding oxygen starts to mix with evaporating fuel vapor from the droplet. When the ignition condition is met, the exothermic reactions of the premixed gas initiate a and burn intensely. The maximum temperature position gradually approaches the droplet surface and maximum temperature increases rapidly following the ignition. The fuel and oxygen concentration distributions have minimum points near the peak temperature position. Therefore the moment of ignition seems to have a premixed-flame aspect. After this very short transient period minimum points are observed in the oxygen and fuel d distributions and the diffusion flame is established. The distance between droplets is an important parameter. Starting from far-away apart, when the distance between droplets decreases, the ignition-delay time decreases meaning faster ignition. When they are close and after the ignition, the maximum temperature moves away from the center line of the in-line array. It means that the oxygen at the center line is consumed rapidly and further supply is blocked by the flame. The study helped the understanding of the ignition of d droplet array and opened the possibility of further research.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.273-273
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• 1997

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.1
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• pp.75-82
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• 2011

The numerical analysis of the reduction of reaction mechanism for the ignition of dimethyl ether (DME) was performed. On the basis of a detailed reaction mechanism involving 79 species and 351 reactions, the peak molar concentration and sensitivity analysis were conducted in a homogeneous reactor model. The reduced reaction mechanism involving 44 species and 166 reactions at the threshold value $7.5{\times}10^{-5}$ of the molar peak concentration was established by comparing the ignition delays the reduced mechanism with those the detailed mechanism. The predicted results of the reduced mechanism applied to the single-zone homogeneous charge compression ignition (HCCI) engine model were in agreement with those of the detailed mechanism. Therefore, this reduced mechanism can be used to accurately simulate the ignition and combustion process of compression ignition engine using DME fuel.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.04a
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• pp.308-312
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• 2008

In this study, we have carried out test to examine the ignition characteristics, such as a relation of moisture content and combustibility, and ignition temperature using KRS-RG-9000 tester, of significant part of above trees which are representative species of Young Dong Province of Korea. After rainfall, the percentage of moisture content of living leaves and branches was between 52 and 70%. But it was just between 17 and 33% after 144 hours drying at normal temperature. For dead leaves, it was 10% lower than of first. There was a significant difference on ignition characteristics. The hazard of ignition is highest on dead leaves. The ignition temperature of barks and branches is higher so a retard time is long than of living and dead leaves at normal temperature.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.256-260
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• 2014

Interior of the building is used as a MDF plywood if there is a fire in order to delay the ignition, flame retardant paint, flame retardant solution and flame retardant film are being handled by the flame retardant. Combustion characteristics anf flame retardant performance results can be summarized as follows: General film with a sample showed that short of the criteria in terms of carbonation area, and the results of flame retardant paint, flame retardant solution and flame retardant film products satisfied the criteria. Toxic gases generated in the combustion process results in a film samples using a high incidence of carbon monoxide and the creation of a smoke could be seen. This confirm that is estimated that result from incomplete combustion of PVC film that attach, and displays high toxicity index and hazard class relatively.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.97-103
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• 2010

The four combustion stages in a diesel engine have close correlation among them. Especially, the ignition delay period has significant effect on the following combustion stage. And the period is also one of inevitable combustion processes in the diesel engine. For example, the diesel knocking is a well-known phenomenon due to the long ignition delay period. The interval of the ignition delay period is affected by the mixture formation process in the cylinder. However, in the case of the D.I. diesel engine, the available duration to make the mixture formation of air-fuel is very short. In addition, the means of the mixture formation mainly depends on the injection characteristics and properties of the fuel. It is difficult to make complete mixture. Therefore, an early stage of combustion is violent, which leads to the weakness of noise and vibration. In this study, using the visible engine, we measured the ignition delay period by photo sensor which detect occurrence of flame and presented the factors of the injection characteristics such as kinds of injection system, the injection pressure and the injection timing. The relation between the ignition delay period and cylinder pressure diagram which was concurrently obtained was also estimated.

• Journal of Institute of Convergence Technology
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• v.9 no.1
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• pp.13-19
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• 2019

The purpose of this study is to suggest a new method to determine a combustion phase (start of combustion and end of combustion) using a combustion pressure data. Unlike previous research method that used heat release amount, the difference between the combustion pressure measured in the combustion chamber and the motoring pressure was used to determine the combustion phase. This research was conducted using a single-cylinder diesel engine with a compression ratio of 17.7. The test was conducted under various injection timing. The newly proposed method showed high accuracy in combustion mode with early injection, as well as the conventional combustion mode. It is expected that this method will be used to study new combustion strategies such as HCCI (homogeneous charge compression ignition) and RCCI (reactivity controlled compression ignition) that are applying early injection strategies as well as existing combustion modes.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.868-876
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• 2014

The objective of this study is focused on the analyzing combustion, carbon monoxide and hydrocarbon emission characteristics of marine diesel oil, utilized for naval propulsion engine, with varying pre-post injection timing of an optically accessible single cylinder engine. And also the combustion process is analyzed by means of a high speed camera visualization. On the result of retarding pre-injection timing toward main injection timing, the mean effective pressure and maximum pressure of combustion chamber are increased; however, the heat release rate is decreased. Furthermore, the emission rates of carbon monoxide and hydrocarbon are reduced in this case. In hence, when a post-injection timing is advanced, the mean effective pressure and maximum pressure are increased, because the combustion has been performed under the high temperature and high pressurized environment during main injection time, and the emission rates of carbon monoxide and hydrocarbon are increased. From the experimental results, it considered that retarding of pre-injection timing affects to shorten the ignition delay of main injection clearly, and to raise the flame intensity comparing to the advanced state. The ignition delay during post-injection is not appeared at any post-injection time, but the flame intensity has been weakened gradually according to the retarding of post-injection timing.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.60-65
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• 1998

핵융합로 증식재용 Li$_2$TiO$_3$ 분말을 자발착화연소합성법으로 합성하였다. Li질산염과 Ti 질산염이 혼합된 전구용액은 연소반응을 위하여 가열되는 동안 침전물이 형성 되었지만 카르복실산기(carboxylic acid group)와 아민기(amine group)를 지닌 글라이신(glycine)이나 카르복실산기만을 가진 구연산(citric acid)과 아민기만을 가진 우레아(urea)를 흔합한 연료를 사용한 경우에는 연소합성반응이 일어나 분말을 쉽게 합성할 수 있었다. 또한 형성된 분말은 별도의 하소공정이 없더라도 원하는 결정상이 형성되었으며, 합성편 Li$_2$TiO$_3$ 분말은 비표면적이 15 $m^2$/g으로 약 30nm의 크기를 지닌 미세한 입자이었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.749-757
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• 2017

To cope with the development of alternative fuels and international environmental regulations, this study provides a numerical analysis of the effects of composition and temperature changes of n-decane and ethanol on auto-ignition characteristics. CHEMKIN-PRO is used as the analysis program and the LLNL model is used as the reaction model. The numerical results show that the ignition delay time increases as the mole fraction of ethanol increases for temperatures below 1000 K, where low temperature reactions occur. Because of the high octane number of ethanol, the high percentage of ethanol delays the increase in the concentration of OH radicals that cause ignition. The oxygen concentration in the mixture is changed to apply the exhaust gas recirculation and a numerical analysis is then performed. As the oxygen concentration decreases, the total ignition delay time increases because the nitrogen gas acts as a thermal load in the combustion chamber.