• 한국연소학회지
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• 제11권1호
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• pp.34-42
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• 2006

Numerical analysis code has been developed to investigate the slab heating characteristics in a reheating furnace of a steel mill company. Unsteady 3-Dimensional behaviour can be predicted with the developed code. Premixed flame model is adopted for combustion phenomena and eddy dissipation model is used for turbulent combustion. Non -gray FVM radiation method is used to get a better accurate radiative solution. Slab movement can be fully traced from entrance into a reheating furnace until it#s exit and computation is performed during that period.

• 한국분무공학회지
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• 제27권1호
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• pp.18-25
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• 2022

Hot-firing tests were performed to experimentally confirm the effect of the eigenmode in the fuel-air mixing section on combustion instability by changing mixing section length, inlet mean velocity, equivalence ratio, and swirler geometry. A premixed gas composed of air and ethylene was supplied to the combustion chamber through an mixing section and an axial swirler. As the mixing section length increased, the inlet velocity perturbation decreased, but the combustion instability increased more. It was found that the resonance frequency of the first longitudinal mode in the mixing section shifted to the third longitudinal mode as the length of the mixing section increased. The results implied that the transition of the resonace frquency by changing the length of the mixing section might cause combustion instability.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2010년도 춘계학술 발표회
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• pp.166-170
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• 2010

토치 점화 장치의 연소 특성을 파악하기 위하여 6개의 각기 다른 토치 점화 장치를 설계하였다. 토치 점화장치의 체적이 메탄의 연소특성에 미치는 영향을 파악하기 위하여, 토치점화 장치의 높이(h)와 오리피스 직경(De)는 10mm와 6mm로 고정하고, 입구 직경(D)을 12mm에서 22mm까지 2mm씩 증가시키며 토치 점화 장치를 설계하였다. 초기 화염 생성 및 전파는 질량 연소율과 연소 촉진율로 분석하였다. 질량 연소율과 연소 촉진율을 계산하기 위하여 정적 연소실 내의 평균 압력을 측정하였다. 또한 shadow graph법을 이용하여, 초기 화염 생성과 화염 전파과정 전 영역을 가시화하였다. 토치 점화 장치를 사용한 경우에는 일반적인 스파크 점화와 비교하여 질량 연소율의 기울기가 증가하였고, 연소 촉진율도 개선된것을 확인하였다. 토치 점화 장치의 체적이 증가할수록 연소가 개선되었으며, 넓은 점화 표면을 제공하였다.

• 대한환경공학회지
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• 제27권3호
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• pp.286-292
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• 2005

본 연구는 향후 산업적으로 질소산화물 규제가 중요한 문제로 대두될 만한 산업용 보일러를 대상으로 수행하였다. 일반적으로 SNCR 방법의 산업용 보일러로의 적용은 혼합을 위한 충분한 체류시간을 제공하지 못한다는 점에서 적합하지 않은 것으로 알려져 있다. 본 연구의 목적은 SNCR 장치의 산업용 보일러 적용가능성을 조사하기 위한 것이다. 구체적으로 연료로 중유를 사용하는 시간당 스팀 발생량 40톤 규모의 산업용 보일러를 연구 대상으로 하였다. 사업용 보일러의 수치 해석을 위한 3-D 직교좌표계 프로그램에는 난류 유동, 난류 연소반응, NOx의 생성과 환원제와의 반응을 통한 소멸반응 등을 포함하고 있다. 또한 개발된 코드에는 Lagrangian 방법에 의한 입자궤적 프로그램이 포함되어 있고, 주입구에서 접선방향으로의 선회효과를 계산에 의해 고려하였다. 선회버너 효과를 고려한 결과 단화염이 생성되었으며 NOx 환원반응에 적합한 온도 영역의 증가로 인해 NOx 제거효율도 향상되었다. 실험결과와의 비교를 통하여 프로그램을 검증하였으며, 계산결과 혼합용 공기 주입을 통한 환원제와의 혼합 향상을 통해서 SNCR 방법의 산업용 보일러 적용가능성을 확인하였다.

• 한국연소학회지
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• 제2권1호
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• pp.17-27
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• 1997

It is well known that NOx formation has a strong dependence on the maximum temperature and correspondingly with the maximum chamber pressure of a closed combustion system. However, in a case of impinging-jet-flame (IJF hereafter) combustion with opposed dual pre-chambers, low $NO_x$ formation with high pressure could be achieved, but its mechanism has not been clearly understood so far. In this study, a three-dimensional analysis is adopted to resolve time-variant local properties that might indicate the mechanism of IJF combustion. Numerical results are verified by comparing them with experiments. The IJF combustion in a vessel with no pre-chamber, with single pre-chamber, and with dual pre-chambers is studied. The orifice diameter and the volumetric ratio of pre-chamber are used as geometric parameters. The effects of main-chamber ignition delay time and combustion time of main-chamber, orifice exit velocity, orifice exit temperature, turbulent kinetic energy of main-chamber and spatial distribution of temperature in the latter stage of combustion are investigated. A longer main-chamber ignition delay and a shorter main-chamber combustion time suppress the formation of high temperature region with respect to mean temperature, which consequently results in less NO production.

• 한국화재소방학회논문지
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• 제26권2호
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• pp.90-96
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• 2012

외장재에 의한 수직화재확산은 확산속도가 구획화재에 비해 매우 빨라 이에 대한 화재의 특성 분석이 요구된다. 본 연구에서는 건물 외부에서 발생한 화재가 연소 확대되면서 수직으로 상승하여 개구부를 통해 유입되는 화재의 성상에 대해서 외장재로 널리 사용되는 심재가 폴리에틸렌인 일반 알루미늄복합패널에 대해 화재시뮬레이션을 적용하여 연구하였다. 그 결과, 수직확산화염은 화재초기에 2층까지 상승하는 데는 약 135초가 걸렸지만 10층까지는 470초, 최고층인 30층까지 상승하는 데는 711초에 도달하는 것으로 분석되어 고층부로 갈수록 난류 및 외장재 설치공간의 연돌효과에 의해서 급격히 확대되는 것을 알 수 있었다. 이러한 연구 결과로 외장재가 설치된 건축물의 화재 시 개구부를 통한 화재는 동시다발적으로 그 건물의 내부에 확대되는 심각성을 확인할 수 있었다.

• 한국분무공학회지
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• 제7권4호
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• pp.32-41
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• 2002

The breakup characteristics of liquid sheets formed by like-doublet injector were investigated in the cold-flow and atmospheric ambient pressure condition. The sheet breakup wavelength, which induces the sheet to be broken into ligaments, as well as the sheet breakup length, which is important for the flame location, was measured using a stroboscopic light. The liquid ligaments are formed intermittently after the breakup of sheet, and the wavelength of ligaments has been believed to have a relation to the combustion instability of liquid rocket engine. Therefore, the wavelength of ligaments and the breakup length of ligaments into fine drops were also measured. Since these spray characteristics are affected by the flow characteristics of two liquid jets before they impinge on each other, we focused on the effects of orifice internal flow such as the cavitation phenomenon that occurs inside the sharp-edged orifice. From the experimental results, we found that the liquid jet turbulence delays the sheet breakup and makes shorter wavelengths for both sheets and ligaments. Since the turbulent strength of sharp-edged orifice is stronger than that of round-edged orifice, the shape of orifice entrance results in large differences in the spray characteristics. Using these results, we proposed empirical models on the spray characteristics of the like-doublet injector, and these models are believed to provide some useful and actual data for designing liquid rocket combustors.

• 대한기계학회논문집
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• 제18권4호
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• pp.912-919
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• 1994

The engine combustion is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake stroke breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of this relationship is not well known. This paper describes the tumble flow measurements inside the cylinder of a 4-valve S.I. engine using laser Doppler velocimetry(LDV) under motoring(non-firing) conditions. This is conducted on an optically assesed single cylinder research engine under motored conditions at an engine speed of 1000rpm. Three different cylinder head intake port configurations are studied to develop a better understanding the tumble flow generation, development, and breakdown mechanisms.

• 대한기계학회논문집
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• 제18권4호
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• pp.920-932
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• 1994

The combustion phenomena of a reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. This paper describes cycle resolved LDV measurement of turbulent flow inside the cylinder of a 4-valve engine under motoring(non-firing) conditions, and studies the effect of intake port configurations on the turbulence characteristics using following parameters ; Eulerian temporal autocorrelation coefficient, turbulence energy spectral density function, Taylor micro time scale, integral time scale, and integral length scale.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.7-8
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• 2012

The effects of interaction between partially premixed and premixed swirl flames on CO and NOx emissions were experimentally investigated using a hybrid/dual swirl jet combustor for a micro-gas turbine. Under the condition of constant angle ($45^{\circ}$) for outer swirl vane, the angle and direction of inner swirl vane installed for a partially premixed flame were varied as main parameters with a constant fuel flow rate for each nozzle. It was found that for all conditions, CO and NOx emissions were measured below 4 ppm and 15 ppm at 15% $O_2$, respectively, in a wide range of equivalence ratio (0.6~0.9). For co-swirl flows, CO emission increased dramatically as the angle of inner swirl vane increased from $15^{\circ}$ to $45^{\circ}$ near lean-flammability limit (i.e. equivalence ratio of 0.5). On the other hand, the case of swirl $angle=45^{\circ}$ provided the lowest NOx emission at higher equivalence ratios than 0.6. For counter-swirl flows, the case of swirl $angle=45^{\circ}$ extended the lean-flammability limit but higher NOx emissions were found compared to those of co-swirl flows. These results could be inferred by interaction between (inner) partially premixed and (outer) premixed swirl flames. However, these estimations were not clear yet because there was insufficient data on turbulent flow structure and fuel-air mixing in the present experimental approach.