• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.75-81
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• 2003

In this paper, the study of effects of flow variables on flame structure and NOx emission concentration was performed in co-axial laminar partially premixed methane/air flames. the objectives are to reveal its effect as parameters were varied and to understand the correlation between flame structure and NOx emission characteristics in the reaction zone. equivalence ratio(${\Phi}$), fuel split degree(${\sigma}$), and mixing distance(x/D) were defined as a premixing degree and varied within $1.36{\sim}3.17$(equivalence ratio), $50{\sim}100$(fuel split degree), and $5{\sim}20$(mixing distance). the image of $OH{\ast}$ and $CH{\ast}$, and NOx concentration were obtained with an ICCD camera and a NOx analyzer. additionally the maximum intensity location of $OH{\ast}$ chemiluminescence and $CH{\ast}$ chemiluminescence were measured to compare each flame structures. In conclusion flame structure and NOx emission characteristics were changed from diffused to premixed flame when mixing degree was on the increase. the main effect on flame structure and NOx production was at first equivalence ratio(${\Phi}$), and next fuel split degree(${\sigma}$), and finally mixing distance(x/D).

• 대한기계학회논문집B
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• 제30권9호
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• pp.905-912
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• 2006

Experiments in low strain rate methane-air counterflow diffusion flames diluted with $CO_2$ have been conducted to investigate the flame extinction behavior and edge flame oscillation in which flame length is less than the burner diameter and thus lateral conductive heat loss in addition to radiative loss could be remarkable at low global strain rates. The critical mole fraction at flame extinction is examined in terms of velocity ratio and global strain rate. It is seen that flame length is closely relevant to lateral heat loss, and this sheets flame extinction and edge flame oscillation considerably. Lateral heat loss causes flame oscillation even at fuel Lewis number less than unity. Edge flame oscillations are categorized into three: a growing-, a harmonic- and a decaying-oscillation mode. Onset conditions of the edge flame oscillation and the relevant modes are examined with global strain rate and $CO_2$ mole fraction in fuel stream. A flame stability map based on the flame oscillation modes is also provided at low strain rate flames.

• 한국화재소방학회논문지
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• 제17권3호
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• pp.20-25
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• 2003

화염변형률과 소화약제의 첨가 및 부력이 비예혼합 대향류 화염의 구조와 소화에 미치는 영향을 조사하기 위해 필라멘트와 열전대를 이용한 실험과 Oppdif 및 FDS를 사용한 수치해석을 수행하였다. 소화농도에 가까운 메탄-공기의 확산화염에 대하여 2.2초의 무중력 낙하실험과 정상중력에서의 측정결과를 수치모사의 결과와 비교하였다. 변형률 7 s$^{-1}$에서 100 s$^{-1}$까지 무중력상태에서 측정한 임계소화농도로부터 질소의 임계소화농도에 최대치가 있음을 확인하였다. 또한, 부력의 효과, 즉, 화염의 곡률과 두께 변화를 FDS의 계산결과로 확인하였다. 무중력상태에서 화염의 최고온도와 그 위치에 대한 실험치와 계산값이 일치함을 알 수 있었다.

• 한국자동차공학회논문집
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• 제13권2호
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• pp.22-28
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And, it is extremely difficult to increase gasoline engine efficiency and to reduce $NO_X$ and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper, a flame trap was used to simulate internal EGR(exhaust gas recirculation) effect. An experimental study was carried out to find combustion characteristics using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). Flame propagation photos and pressure signals were acquired to verify the flame trap effect. The flame trap creates high speed burned gas jet. It achieves higher flame propagation speed and more stable combustion due to the effect of geometry and burned gas jet.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.171-181
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• 2007

Blending effects of hydrogen and water vapor on flame structure and NOx emission behavior are numerically studied with detailed chemistry in methane-air counterflow diffusion flames. The composition of fuel is systematically changed from pure methane and pure hydrogen to the blending fuels of methane-hydrogen-water vapor through the molar addition of $H_2O$. Flame structure is changed considerably for hydrogen-blending methane flames and hydrogen-blending methane flames diluted with water vapor in comparison to pure methane flame. These complicated changes of flame structures also affect NOx emission behavior considerably. The changes of thermal NO and Fenimore NO are analyzed for various combinations of the fuel composition. Importantly contributing reaction steps to thermal NO and Fenimore NO are addressed in pure methane, hydrogen-blending methane flames, and hydrogen-blending methane flames diluted with water vapor.

• 한국잔디학회:학술대회논문집
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• 한국잔디학회 2011년도 제24차 정기총회 및 학술발표회
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• pp.11-21
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• 2011

경기도 여주군의 R골프장에서 페어웨이 건설 시 토양조사 및 적절한 토양개량이 실시되지 않아 배수불량지역의 발생한 것으로 한 것으로 분석되었다. 원인 분석결과 토양 경화로 인한 토양 물리성이 악화되어 있어, 투수에 의한 토양 하부층으로의 배수능력이 저조하여 배수 불량의 직접 원인이 되었다. 또 재배 지역의 토양과 이식 지역의 토성이 달라 이식 후 토양에 이질층이 형성되어 수분의 하층 이동이 원활하지 못해 배수 불량의 원인되고 잔디의 생육이 나빠지게 되었다. 배수불량의 결과로 인해 토양 내 산소가 부족하게 되어 토양이 환원 상태가 되면서 혐기성 미생물의 생육이 증가하고, 메탄가스가 축적되고 악취를 유발시키며 토양의 공기순환이 자유롭지 못해 식재된 잔디의 뿌리 생장에 악영향을 주어 결과적으로 잔디 생육이 불량하게 되는 연쇄적인 문제가 발생하였다. 골프장 운영 중 잔디 지반의 문제로 잔디 생육 불량을 초래 할 수 있는 여러 가지 요인들을 제거하기 위해 골프코스 건설시 모재 토양의 사전 조사 및 잔디 지반으로서의 적합성에 대하여 반드시 실험 분석하여야 하며, 건설 후 지반의 배수불량을 개선하기 위해서 배수구 설치, Sand capping, 잔디 보식, 토양개량재의 사용, 배토 등 경종적 관리 등의 방법을 이용하여 배수불량지역의 개선과 잔디생육 정상화를 시행하였다.

• 대한기계학회논문집B
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• 제21권5호
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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.

• 한국분무공학회지
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• 제10권2호
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• pp.41-47
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And. it is extremely difficult to increase gasoline engine efficiency and to reduce NOx and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper. internal EGR(exhaust gas recirculation) effect is suggested to realize CAI combustion. An experimental study was carried out to achieve CAI combustion using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). A flame trap was used to simulate internal EGR effect and to increase flame propagation speed in the CVCC. Flame propagation photos and pressure signals were acquired to verify internal EGR effect. Flame trap creates high speed burned gas jet. It achieves higher flame propagation speed due to the effect of geometry and burned gas jet.

• 대한화학회지
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• 제29권3호
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• pp.226-232
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• 1985

디옥소몰리브데늄(VI) 착물, MoO$_2$(H-Sal-R)$_2$, R ; 아릴아민을 디옥소비스살리실알데히다토 몰리브데늄(Ⅵ)과 여러가지 일차아민으로 부터 합성하여 원소분석, 전기전도도 및 분광학적 연구로 부터 이들 착물에 대한 구조를 조사하였다. 적외선 가시 및 자외선 그리고 핵자기 공명스펙트라로 부터 이들 착물은 여섯배위된 팔면체의 cis-MoO$_2$형을 가지고 있음을 알 수 있었고 질량스펙트라로 부터 MoO$_2$와 배위자간의 결합비가 1:2임을 확인하였다. 또한 이들 착물은 노란색 결정으로 공기중에서 오랫동안 안정하고 알코올 디클로메탄 그리고 디메틸포름아마이드에 약간 녹으며 벤젠, 에테르, 사염화탄소등의 일반 유기용매에는 녹지 않았다.

• 한국안전학회지
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• 제26권5호
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• pp.1-6
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• 2011

Flame extinction and the chemistry of stoichiometric methane/air mixture were investigated numerically in the PSR(perfectly stirred reactor). For the study, PSR code was modified to be possible to unsteady calculation, and the sinusoidal fluctuation was subjected to the residence time. In the region of residence time far from the extinction limit, combustion mode was strongly dependent on the frequency. The low frequency excitation provided the quasi-steady behavior on the temperature and the concentrations of related species, but small variation of temperature was observed under high frequency. In the region of residence time near the extinction limit, the mixture subjected above 1 KHz was still reacting even though extinction had to be occurred under quasi-steady concept. The attenuation of extinction limit resulted from that chemical time was comparable to the flow time. The mean mole fractions of both NO and CO were almost same regardless of imposed frequency. However, the average mole fraction of $C_2H_2$ was decreased as increasing frequency, which implies that soot yield might be reduced at the higher frequency of flow excitation. The result provides the basic concept for flame stabilization, and it will be used to design a mild combustor.