Structure and Suppression of Nonpremixed Counterflow Flames

Hamins, Anthony,Park, Woe-Chul 한국화재소방학회 2003 한국화재소방학회논문지 Vol.17 No.3

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 100s^(-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. Measurements with filaments and thermocouples and computations with Oppdif and FDS were carried out to investigate the impact of flame strain, agent addition, and buoyancy on the structure and extinction of nonpremixed counterflow flames. Measurements through 2.2 s drop tests in microgravity conditions and experiments in normal gravity conditions were compared with the results of computations. For the global strain rates 7 s^(-1) through 100 s^(-l), the turning point behavior in the critical nitrogen concentration at 0-g was confirmed. The effects of buoyancy, that is, changes in the flame curvature and thickness were also confirmed by the computations with FDS. There was agreement in the peak flame temperature and its position between the computations and the measurements in the near extinction methane/air diffusion flames in microgravity.

정상 중력장에서 낮은 스트레인율을 갖는 대향류 비예혼합화염의 소화한계

Anthony Hamins,김정수,오창보,박정,최병일 대한기계학회 2005 大韓機械學會論文集B Vol.29 No.9

비예혼합 대향류화염의 구조와 소화

Anthony Hamins,Park,Woe-Chul 한국화재소방학회 2003 한국화재소방학회논문지 Vol.17 No.3

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<TEX>$^{-1}$</TEX>에서 100 s<TEX>$^{-1}$</TEX>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. Measurements with filaments and thermocouples and computations with Oppdif and FDS were carried out to investigate the impact of flame strain, agent addition, and buoyancy on the structure and extinction of nonpremixed counterflow flames. Measurements through 2.2 s drop tests in microgravity conditions and experiments in normal gravity conditions were compared with the results of computations. For the global strain rates 7 s<TEX>$^{-1}$</TEX> through 100 s<TEX>$^{-1}$</TEX> , the turning point behavior in the critical nitrogen concentration at O-g was confirmed. The effects of buoyancy, that is, changes in the flame curvature and thickness were also confirmed by the computations with FDS. There was agreement in the peak flame temperature and its position between the computations and the measurements in the near extinction methane/air diffusion flames in microgravity.

제조사 보정상수에 기인한 열유속계의 측정 오차

김성찬,Anthony Hamins 한국화재소방학회 2018 한국화재소방학회논문지 Vol.32 No.4

As a preliminary study to quantify the measurement uncertainty of the Schmidt-Boelter type heat flux gauge, the presentstudy has been conducted to evaluate the measurement error due to the calibration constant supported by manufacturer. Calibrations of heat flux gauges are performed at NIST Fire Research Division using a calibration facility with heat sourceof a 2000 W halogen-tungsten filament lamp and the calibration constant is obtained by comparing the response of thereference and a standard heat flux gauge at the same irradiance conditions. Calibration for heat flux gauges made by threedifferent manufacturers is compared with their factory calibration constant. Relative error due to fluctuation of output signalfrom heat flux gauges does not exceed 1% of the mean value and the relative error between calibration of this study andfactory calibration constant ranged from 1.5% to 14.3%. The present study shows that a continuous and periodic calibrationis necessary for accurate heat flux measurement. 본 연구는 Schmidt-Boelter형 열유속계의 측정 불확실도를 정량화하기 위한 기초연구로서 제조사에서 제공되는 보정상수의 측정오차를 평가하였다. 보정실험은 미국립표준기술원(NIST) 화재연구부의 2000 W급 할로겐-텅스텐 램프를 열원으로 적용한 열유속계 보정장치를 이용하였으며 동일 열유속 조건들에 대해 보정대상 열유속계와 표준열유속계를 비교하여 보정상수를 얻었다. 3개 제조사의 열유속계에 대한 보정실험 결과를 제조사의 보정상수와 비교하였다. 열유속계의 출력신호의 섭동값은 1 ․ 를 넘지 않았으며 보정실험결과와 제조사의 보정상수의 상대오차는 1.5%~ 14.3%까지 차이를 보였다. 본 연구는 정확한 열유속을 측정하기 위해 지속적이고 주기적인 보정과정이 필요함을보여준다.

Development of a Three-Dimensional DNS Code for Study of Clean Agents -Two-Dimensional Simulation of Diluted Nonpremixed Counterflow Flames-

Park, Woe Chul,Hamins, A. The Korean Society of Safety 2002 International Journal of Safety Vol.1 No.1

A mixture fraction formulation is used to numerically simulate the structure of diluted axisymmetric methane-air nonpremixed counterflow flames. The effects of global strain rate and gravity wert! investigated and results were compared. Fuel of a mixture of 20% methane and 80% nitrogen by volume and oxidizer of pure air at low and moderate global strain rates $a_g= 20, 40, 80 s^{-1}$ in normal and zero gravity were computed. It is shown that the numerical method is capable of predicting the structure of counterflow flames in normal and microgravity environments at low and moderate global strain rates.

미소 중력장에 있는 저신장율 화염소화에 미치는 다차원 효과

김정수,오창보,박정,Anthony Hamins 대한기계학회 2005 大韓機械學會論文集B Vol.29 No.9

Investigation of Velocity Boundary Conditions in Counterflow Flames

Woe Chul Park,Anthony Hamins 대한기계학회 2002 KSME International Journal Vol.16 No.2

환기부족 구획화재에 대한 FDS 해석 및 검증

고권현,김성찬,A. Hamins,유홍선 한국화재소방학회 2009 한국화재소방학회논문지 Vol.23 No.5

In this study, fire simulations on the under-ventilated compartment fires have been conducted using the Fire Dynamics Simulator (FDS Ver. 5.2) and its prediction performance on the thermal and combustion chemical characteristics has been discussed. The temperature and chemical species concentrations in the upper layer of methane, heptane, and toluene fires located in a 2/5 scale compartment based on the ISO-9705 standard room are predicted and compared with the previously published experimental data. The results showed that the FDS simulations reproduced well the temperature of the ceiling and the mixture fraction in the upper layer under the well-ventilation conditions. For the under-ventilated fires, which were taken place due to the insufficient oxygen entrainment, the prediction by the FDS significantly under-estimated the production of carbon monoxide and soot compared to the experimental data. 본 연구에서는 환기부족 조건의 구획화재에 대하여 FDS(Ver. 5.2)를 이용하여 수치해석을 수행하였고 열적 특성 및 연소 가스 생성 특성에 대한 예측성능을 평가하였다. ISO-9705 표준화재실의 2/5 크기 모 형에 대한 메탄 및 헵탄, 톨루엔 화재를 모사하였으며 고온 상층부의 온도, 연소가스 농도 등에 대하여 기존의 실험 결과와 비교하였다. 실험결과와의 비교를 통해 FDS가 천정의 온도와 과환기 조건의 혼합분 율의 예측에 있어서 좋은 성능을 보임을 확인할 수 있었다. 그러나 화재 크기에 비해 산소의 유입량이 충분치 않은 환기부족 조건에서는 일산화탄소 및 그을름의 발생량을 실험값에 비해 크게 하향 예측하였다.

An experimental study of acoustically driven medium-scale pool fires

이기용,Andrew Lock,Anthony Hamins 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.8

A set of experiments has been conducted on a medium-scale propane fueled pool fire acoustically forced in order to facilitate repeatable measurements defining the flame’s transient behavior. The fuel flow was slightly perturbed at the pool fire’s natural frequency by a sine waveform driven with a loudspeaker which was installed under the burner. As a result of the perturbation, the puffing behavior of the pool fire and the fire shape were modified. As the magnitude of the sine wave was increased larger perturbations were clearly observed,based on the measurement of the radiative heat flux and image analysis. Temperature and soot volume fractions were measured along the center line and throughout a slice of the flame. The soot volume fractions in the flame region are in good agreement with the data of other researchers. The reproducibility of these measurements was established through several experiments. The acoustically driven flame provides the possibility of more repeatable measurements of the transient behavior of these pool fires.

환기 조건에 따른 화재거동 연구

김성찬(Sung Chan Kim),Anthony Hamins 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.5

A series of fire experiments has been conducted to provide an improved understanding of the fire structure of under-ventilated compartment fires. A comprehensive and quantitative assessment of gaseous species from the fire was made in the upper layer of fire in a 40 % reduced scale ISO 9705 fire compartment. The global equivalence ratio (GER) concept was used to characterize the fire behavior for various fire sizes, fuel types and ventilation conditions. The oxygen concentration in the upper layer reached to zero near the global equivalence ratio of 0.4~0.6 while the carbon monoxide concentration increases with increasing the global equivalence ratio. Classification parameters of ISO19706 were also compared with the reduced scale experimental data for under ventilation fire.