• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.602-614
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• 1997

In order to evaluate the effects of equivalence ratio, initial pressure and temperature on the laminar flame propagation process, and combustion radicals characteristics, experimental approaches are carried out in methane-air premixture using a constant volume chamber. Local and average radical intensities were measured to determine the time and spatial correlations between each radicals; C $H^{*}$(431 nm), $C_{2}$$^{*}$ (517 nm) and O $H^{*}$(309 nm) . The results are showed that two kinds of equation were proposed for the cases of continuous flame and intermittent flame type to evaluate actual equivalence ratio using relative intensities with each radicals. Both equations were agreed with actual equivalence ratio within 10% errors range. And schlieren photo and CCD image were compared with flame sizes at equivalence ratio 1.0.o 1.0.

• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.51-60
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• 1997

축대칭 곡면벽 제트 버너를 제작하여 화염의 안정화 특성을 실험적으로 연구하였다. 축대칭 곡면벽 제트 유동은 난류 강도의 증가와 더불어 버너 선단 부근에 재순환 영역을 형성하여 화염의 안정화를 촉진시킴으로서 기존의 튜브 버너에 비하여 화염의 안정화 특성이 향상되었다. 시간적으로 화염의 위치가 변동하는 난류 화염에서 화염의 안정화 특성과 밀접한 관계가 있는 OH 라디칼과 온도를 PLIF와 CARS를 각각 적용하여 측정하였다. 고유속으로 연소시키는 경우에 버너 선단에 형성된 재순환 영역에 OH 라디칼이 상당량 분포하고 있었으며 통계적으로 고온을 유지하였다. 이는 버너 선단에 형성되는 재순환 영역에 고온의 기연 가스가 점화원 역할을 하여 화학 반응이 활발하게 일어나고 있음을 의미한다. 이러한 결과로부터 고속의 출구유속에서 화염 안정화 특성은 재순환 영역에 의하여 영향을 받고 있음을 확인하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.45-53
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• 2004

An experimental study was carried out to obtain the fundamental data about the effects of radicals induced injection on premixture combustion. A constant volume combustor divided to the sub-chamber and the main chamber was used. The volume of the sub-chamber is set up to occupy less than 1.5％ of that of whole combustion chamber. Radial twelve narrow passage holes are arranged between the main chamber and the sub-chamber. The products including radicals generated by spark ignition in the sub-chamber will derive the simultaneous multi-point ignition in the main chamber. While the equivalence ratio of pre-mixture in the main chamber and the sub-chamber is uniform. We have examined the effects of the sub-chamber volume, the diameter of passage hole, and the equivalence ratio on the combustion characteristics by means of burning pressure measurement and flame visualization. In the case of radical ignition method(RI), the overall turning time including the ignition delay became very short and the maximum burning pressure was slightly increased in comparison with those of the conventional spark ignition method(SI), that is, single chamber combustion without the sub-chamber. The combustible lean limit by RI method is extended to more ER=0.25 than that by SI method. Therefore the decrease of every emission including NOx and the improvement of fuel consumption is anticipated due to lean burn.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.58-65
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• 2004

A cylindrical constant volume combustion chamber was used to investigate the combustion characteristics of stratified methane-air mixture under several initial charge conditions in the author's previous reports. The results showed that the improvement of thermal efficiency and reduction of heat loss was realized simultaneously by using 2-stage injection method. This paper deals with the reason why the stratified combustion has showed better combustion rate through the measurement and analysis of chemiluminescence of C $H^{*}$ and $C_{2}$$^{*}$ radicals. An optic fiber bundle is used to measure the local emission of C $H^{*}$ and $C_{2}$$^{*}$ radicals to map the relationship between the excess air ratio and local radical intensity ratio in the combustion vessel at 5 mm apart form the geometric center. The results show that there exist a relationship between the intensity ratio and the air-fuel ratio. It is revealed that the improvement of combustion rate in a lean-stratified mixture is realized through the 2-stage injection method. method.

• Journal of the Korean Society of Combustion
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• v.8 no.1
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• pp.9-16
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• 2003

Carbon soot emission from combustion processes, especially from diesel engines, is a subject of growing concern since soot is known to seriously affect human health. Efforts have been made to oxidize soot particles utilizing Non-Thermal Plasma(NTP) techniques. When oxygen is carried into a plasma device, electrons generated by the plasma dissociate the oxygen, resulting in the formation of oxygen atoms. These highly activated atoms, called O radicals, are known as strong oxidizing agent. This paper presents concentration variations of CO and $CO_2$ at the exit of the plasma device, resulting from the soot oxidation by O radicals, with variations of inlet oxygen concentration, gas temperature, and gas flow rate. Based on the data, Arrehenious rate constants of reactions between C(s)+O and C(s)+O+O were proposed.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.506-513
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• 2008

The engine containing a radical injector has been studied to improve the performances of efficiency and to reduce the exhaust emissions recently. The engine is far different from general compression ignition engines or spark ignition engines for the concept of combustion process. The inflow characteristic from main chamber into radical chamber during compression stroke is important because the radical chamber must have enough fresh air to generate appropriate radicals. The numerical simulation is performed in each specific shape and the engine speed by using KIVA code. The result shows that the fresh air inflow from main chamber into the radical chamber is the best at 45 degree of the hole angle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1309-1316
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• 2003

A premixed-compression-ignition engine has been studied to improve the efficiency and to decrease exhaust emissions. However those systems have some difficulties for controlling combustion process. Radical is an activated chemical species formed by a chemical chain reaction between reactant and product. When the chain reactions occur, the energy bond of species is broken easily by the released radicals. The combustion chamber of the premixed-compression-ingnition engine is consist of a main chamber with lean premixture and a subchamber with rich premixture. Those are connected by narrow cylinderical connections. With ignition start in the subchamber, many different kinds of radical is jetted into the main chamber. The premixed gas in main chamber is quickly burned up by the radical ignition in multi-pionts. In this paper, the combustion phenomena in a constant volume combustor having a radical injector are numerically analyzed. The some constants in the reaction rate equation are adjusted by the experimental results tested in the same geometrical chamber. The code is applied on the two combustors in a wide range of equivalence ratio. The results show that the burning time is much shorter in the combustor having radical injector.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.53-59
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• 2006

This study is measurement of radicals in gas & light oil diffusion flame focused on burner exit. The goal of this study is to analyse the relationship between flame chemiluminescence($OH^{\ast}$, $CH^{\ast}$, $C_2^{\ast}$) intensities and flame conditions. The investigation performed turbulent diffusion flame of commercial burner in varying the excess air ratio from 1.0 to 1.8. The optical emissions were measured by photomultiplier(PMT) using optical band pass filter and spectrometer system. The effects of excess air ratio and NOx emission characteristics on the radical emission intensities were investigated experimentally.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.1064-1071
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• 1994

There are three active radicals which become to the scale of flame diagnostics at the flame front. They are OH, CH and $C_2$ radical. For this, optical measurement system which could monitor simultaneously the luminous waves of three radicals, was constructed. These were analyzed statistically into the cross correlation, coherence and phase. Through such an statistical treatment, combustion characteristics was investigated at the primary zone of gas turbine combustor. The local equivalence ratio was predicted with the ratio of luminuous intensity between CH and $C_2$ radical. This result was matched up to the equivalence ratio calculated from gas composition within 5% error. In general, equivalence ratio was said to be 1.0 at flame front, but it could be increased up to about 1.2 depending on the degree of swirl intensity in case of changing properly the air amount of primary zone.

• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.18-25
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• 2006

The present studying is aimed to establish the relationship between flame chemiluminescence$(OH^*,\;CH^*,\;C_2^*)$ intensities and combustion conditions such as $NO_x$ emission characteristics. Measurements are made for $OH^*,\;CH^*,\;C_2^*$ radicals in gas & light oil diffusion flames. At turbulent nonpremixed combustion mode, the equivalence ratio is varied. The optical emissions were measured by photomultiplier(PMT) using optical band pass filter and spectrometer system. The experimental results showed that the ratio of radicals and $NO_x$ emission characteristics have exponential correlations and equivalence ratio characteristics have linear correlations at this experimental conditions.