Agar Gel Barrier의 농도변화에 따른 폭발완화 특성에 관한 실험적 연구

박달재(Dal Jae Park),김남일(Nam Il Kim) 한국가스학회 2011 한국가스학회지 Vol.15 No.5

폭발챔버에서 Agar gel barrier의 폭발완화 특성을 조사하기 위하여 실험적 연구를 수행하였다. 단면적 100 × 100 mm<SUP>2</SUP>, 길이 1400 mm를 가지는 폭발챔버 그리고 폭발챔버의 개구부에 설치될 gel barrier의 고정을 위하여 100 × 100 × 300 mm<SUP>3</SUP>의 챔버를 제작하였다. Agar gel과 물을 혼합하여 4가지 서로 다른 농도(2, 3, 4, 5 %)를 가지는 agar gel barrier를 제조하여 실험변수로 사용하였다. 폭발과정 동안 gel displacement의 가시화를 위해 고속카메라 그리고 gel barrier 전·후단의 폭발압력 변화를 관찰하고자 압력획득시스템을 사용하였다. 실험결과, gel 농도 증가에 따라 gel의 파열시간 및 최대 폭발압력 도달시간이 지연되는 것으로 나타났다. 또한, gel 농도가 증가할 때 gel barrier 전·후단에서의 폭발압력 완화율이 증가하는 경향으로 나타났다. Experimental studies were carried out to investigate the characteristics of explosion mitigations by varying concentrations of agar gel barriers in an explosion chamber, 1400 mm in length, with a square cross-section of 100 × 100 mm<SUP>2</SUP>. Another extension chamber, 100 × 100 × 300 mm<SUP>3</SUP>, was made to hold a gel barrier. Four different gel concentrations were used in the measurements: 2, 3, 4, 5 %(by weight of gel). Displacement of the gel barrier was measured using a high speed camera, and pressure development was measured using pressure transducers and a data acquisition system. It was found that as the concentrations of the gel barriers increased, the gel rupture time and the time taken to reach the maximum pressure increased. It was also found that the increment of gel concentrations increased the reduction percentage in the maximum pressure between before and after gel barrier.

직사각형 폭발 챔버에서 화염전파와 직사각형 장애물의 상관관계

박달재 ( Dal Jae Park ),이태성 ( Tae Sung Lee ),이영순 ( Young Soon Lee ) 한국안전학회 2008 한국안전학회지 Vol.23 No.2

증기운 폭발에 의해 발생된 폭풍 과압 예측 모델 검토

박달재(Dal Jae Park),이영순(Young Soon Lee),임영훈(Young Hoon Lim) 한국가스학회 2000 한국가스학회지 Vol.4 No.4

Flame Propagations of Gasoline-Air Mixtures by Electrostatic Discharge Energies

박달재(Dal-Jae Park),김남일(Nam Il Kim) 한국가스학회 2011 한국가스학회지 Vol.15 No.3

실린더형 챔버내에서 정전기 방전에너지 변화에 따른 가솔린-공기 혼합물의 화염전파에 관한 영향을 조사하기 위해 실험적 연구를 수행하였다. 3개의 서로 다른 정전기 방전 에너지(1 mJ, 50 mJ 및 98 mJ)를 실험변수로 사용하였으며, 점화원 전극 주변의 미연소가스 유동장을 가시화하기 위해 고속 PIV 시스템을 적용하였다. 정전기 방전 에너지가 증가할 때, 점화원 핵은 찌그러면서 초기화염에 영향을 미치는 것으로 나타났다. 초기화염 동안에 화염속도는 점화에너지가 높을수록 증가하는 것으로 나타났으나, 초기화염 이후에 시간이 증가할수록 화염속도는 점화에너지에 관계없이 거의 유사하였으며, 이는 문헌[5]에서 보여진 전산유체 모델링 결과의 경향과 거의 유사하였다. 또한, 점화에너지가 증가할 때 전파하는 화염 전면의 미연소가스 속도장은 증가하는 것으로 나타났다. Experimental studies were carried out to investigate the effects on flame propagation of gasoline-air mixtures by different electrostatic discharge energies in a cylindrical chamber. Three different ignition energies were used: 1 mJ, 50 mJ and 98 mJ. In this work, a high-speed particle image velocimetry technique was applied to visualize the flow-field around ignition electrodes. It was found that as the ignition energy increased, the ignition kernel was different. The different ignition kernel caused different flame initiation. During the flame initiation, the higher ignition energy was applied, the higher flame speed was observed. However, with increasing time, the flame speeds were independent of the ignition energies used. Theses observed flame behaviors were similar to computational simulations shown in the literature. It was also found that as the ignition energies increased, the velocities of unburnt mixtures ahead of propagating flame fronts increased.

젤라틴 Simulant를 이용한 비비탄총 탄환의 위험성에 관한 실험적 연구

박달재 ( Dal Jae Park ),김형석 ( Hyung Suk Kim ),이영순 ( Young Soon Lee ) 한국안전학회(구 한국산업안전학회) 2011 한국안전학회지 Vol.26 No.3

Experimental studies were performed to investigate the injury potential of BB pellets through gelatine based simulants. In order to record BB pellet movements penetrating into the target simulant, a high-speed video camera was used. In this study the first investigation involved the effects on concentrations, homogeneity and gelation times of the gelatine simulant. The second investigation involved the penetration depth of the pellets to the simulant by different distances between the BB gun and the simulant. The final one is associated with impact velocity, threshold velocity and penetration depth of the pellets by different kinetic energies of the BB gun. Results provided the basis in assessing the injury potential of BB pellets.

Water Gel Barrier 표면형상의 크기에 따른 폭발특성

박달재(Dal Jae Park),김남일(Nam Il Kim) 한국가스학회 2012 한국가스학회지 Vol.16 No.3

폭발챔버에서 water gel barrier의 표면형상의 크기에 따른 폭발거동 특성을 조사하기 위하여 실험적 연구를 수행하였다. 단면적 100 × 100 ㎟, 길이 1600 ㎜를 가지는 폭발챔버 그리고 점화원으로부터 각각 300 ㎜, 700 ㎜ 및 1100 ㎜ 떨어진 챔버 바닥면에 100 × 200 ㎟의 크기에 서로 다른 크기의 표면형상을 고려한 gel barrier를 설치할 수 있도록 제작하였다. 젤라틴 gel과 물을 혼합하여 4가지 크기의 표면형상을 가지는 water gel barrier를 제조하여 실험변수로 사용하였다. 폭발과정 동안 화염전파 과정을 가시화하기 위해 고속카메라 그리고 폭발압력 변화를 관찰하고자 압력획득시스템을 사용하였다. 실험결과, gel barrier의 표면형상의 크기가 커질수록 화염전파과정 및 최대 폭발압력 도달시간은 빠르게 진행되는 것으로 나타났으며, 화염속도 및 폭발압력 또한 증가하는 경향으로 나타났다. Experimental investigations were carried out to examine the explosion characteristics by different sizes in the wall surface shape of a water gel barrier in an explosion chamber, 1,600 ㎜ in length with a square cross-section of 100 × 100 ㎟. The sizes in the wall surface shape were varied by using water gel barriers with a cross-section of 100 × 200 ㎟ and its were varied in the bottom of the chamber away 300, 700 and 1,100 ㎜, respectively from the closed end of the chamber. The flame propagation images were photographed with a high speed camera and the pressure was recorded using a pressure transducer and a data acquisition system. It was found that as the size of the wall surface shape increased, the flame propagation process and the time taken to reach the maximum pressure were found to be faster. As a result, both the flame speed and the explosion overpressure increased as the size of the wall surface shape increased.

장애물이 있는 챔버 내부의 정전기 방전 에너지에 의한 가스 폭 발시 초기화염과 화염전파 특성에 대한 PIV 계측

박달재(Dal Jae Park),이석환(Seok Hwan Lee),성재용(Jaeyong Sung),이영순(Young Soon Lee) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.9

In order to investigate the effects of three different electrostatic discharge energies on gas explosions, a high-speed PIV system has been applied. The present study paid attention to the flame initiation by the gas explosions and its propagation at the existence of an obstacle within a chamber. Three different ignition energies such as 0.56 mJ, 52.87 mJ and 112.5 mJ were used. It is found that the ignition kernel is bent by the electrostatic discharge during the flame initiation. Tangential velocities of unburnt mixture ahead of initially propagating flame fronts are increased with increasing ignition energy, which makes the flame propagation faster before it reaches the obstacle. Although the flame speed was found to be less sensitive to the ignition energies, the flame developments were different. The effects of the energies on explosion pressures were also discussed.

부분 밀폐 공간의 가스 폭발에 대한 과압 예측 방법 검토

박달재(Dal Jae Park),이영순(Young Soon Lee) 한국가스학회 2000 한국가스학회 학술대회논문집 Vol.2000 No.9

0.57의 L/D 비를 가지는 폭발챔버에서 전파하는 화염과 다중 장애물의 상호작용에 관한 실험적 연구

박달재 ( Dal Jae Park ) 한국안전학회(구 한국산업안전학회) 2012 한국안전학회지 Vol.27 No.6

Experimental investigations were performed to examine the characteristics of propagating flame fronts around multiple bars within a rectangular chamber. The explosion chamber is 400 mm in height, 700×700 mm(2) in cross section and has a large top venting area, A(v) of 700×210 mm(2). This results in a value of 0.44 for A(v)/V(2/3) and a L/D value of 0.57. The multiple obstacles of length 700 mm with a blockage ratio of 30% were placed within the chamber. Temporally resolved flame front images were recorded by a high speed video camera to investigate the inte-raction between the propagating flame and the obstacles. Results showed that the flame propagation speeds before the flame impinges onto the obstacle almost equal to the laminar burning velocity. As the propagating flame impinged on the obstacle, the central region of flame began to become concave, this resulted in the flame deceleration in the region. As the flame interacted with the modified flow filed generated behind the central obstacle. the probability density functions(PDFs) of the local flame displacement speed were extensively distributed toward higher speeds.

폭발챔버에서 전파하는 화염의 국부 거동

박달재 ( Dal Jae Park ),이영순 ( Young Soon Lee ) 한국안전학회(구-한국산업안전학회) 2011 한국안전학회지 Vol.26 No.2

다중 장애물을 가지는 폭발챔버에서 전파하는 화염과 국부 장애물의 상관관계를 조사하기 위하여 실험적 연구를 수행하였다. 폭발챔버 높이 235 mm, 단면적 1,000×950mm2, 벤트면적 1,000×320mm2를 가지는 폭발챔버를 제작하였으며, 30% blockage ratio를 가지는 장애물을 챔버내에 설치하였다. 전파하는 화염과 장애물의 상관관계를 조사하기 위해 고속카메라를 사용하였다. 고속카메라로 얻어진 화염 이미지로부터 장애물 주위의 국부 화염전파 거동은 2가지 다른 방법, 즉 전파하는 화염전면(flame front)의 각 pixel point에서 산정된 평균 화염전파속도와 연소면적 증가(incremental burnt area)/화염전면 길이(flame front length) 관점에서 분석하였다. 분석결과, 2가지 방법으로 얻은 결과는 거의 일치하는 경향을 나타났으며, 전파하는 화염이 장애물의 전면과 상호 작용할 때 화염속도는 급격히 증가하다가 장애물의 후단면에서 약간 감소하고, 화염이 장애물 후단에서 재결합될 때 다시 급격히 증가하였다. Experimental studies were carried out in an explosion chamber to investigate the influences of multiple cylinder obstacles on local flame propagation. The chamber dimension is 235 mm in height with a 1,000×950mm2 rectangular cross section and a large vent area of 1,000×320mm2. Multiple cylinder bars with obstruction ratio of 30% were used. In order to examine the interaction between the propagating flames and the obstacles, temporally resolved flame front images were recorded by a high speed video camera. The propagation behaviour of local flame fronts around the left obstacle was analyzed in terms of two different methods such as the incremental burnt area divided by the flame front length and the average of the local propagation velocity determined at each point along the flame front. It was found that two methods give good consistency.