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Gwon Hyun Ko(Gwon Hyun Ko) 한국화재소방학회 2023 International Journal of Fire Science and Engineer Vol.37 No.1
This research was conducted to numerically analyze the smoke confinement and radiation shielding characteristics of water mist curtains during the process of plume flow that propagates along the ceiling after its occurrence in fire source. We reviewed the flow field based on the location of the spray, size of water mist droplets, temperature distribution, and soot distribution. The optical density extracted at a height of 1.5 m and the thermal radiation attenuation rate values were comparatively analyzed. In the case of no water-mist operation, the temperature and soot concentration were stable as they formed a layer toward the floor from the ceiling. By contrast, when the water mist curtain was operational, the spray flow obstructed the ceiling jet flow and caused considerable mixing. The results from reviewing the optical density predictions showed that it tended to decrease at a distance sufficiently far downstream of the curtain, but overall the effect was not meaningful compared to the case of no water-mist operation. This was considered to be because a considerable number of fine droplets, as well as soot particles included in the smoke, affected the optical density. Conversely, the attenuation rate of thermal radiation was greatly affected by the average size of the droplets. In the case when the location of the water mist curtain was xinj = 6 m, the thermal radiation attenuation rate at the lowermost part changed from 79.0%, 29.7%, and 17.0% as the average spray droplet size increased from 200, 500, and 1,000 μm., respectively.
Ko, Gwon-Hyun,Ryou, Hong-Sun,Hur, Nahm-Keon,Ko, Seung-Woo,Youn, Myoung-O 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.4
The main purpose of the present study is to perform numerical study on bouncing and separation collision between two droplets considering the collision-induced breakup. In this study, the collision model proposed in our previous study is used for simulation of collision-induced breakup, and we modify this model to consider the effect of liquid property on the behavior of droplet-droplet collision. This collision model is based on the conservation laws for mass, momentum, and energy between before and after collision and provides several formulae for post-collision characteristics of colliding droplets and satellite droplets. Improving the accuracy of the model, in this study, appreciate criterion for bouncing collision is added and dissipation energy during collision process is newly modeled. To validate the new model, numerical calculations are performed and their results are compared with experimental data published earlier for binary collisions of water, propanol, and tetradecane droplets. It is found from the results that the new model shows good agreement with experimental data for the number of satellite droplets. It can be also shown that the predicted mean diameter by the new model decrease with increasing the Weber number because of the collision-induced breakup, whereas the O'Rourke model fails to predict the size reduction via the binary droplet collision.
고권현(Ko, Gwon Hyun) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.8
본 논문은 미세물분무 작동에 따른 화재 거동 및 제압 특성을 예측하는 데 있어서 FDS(Fire Dynamic Simulator)의 예측 성능을 평가하는 것을 목적으로 한다. 미세물분무의 초기액적분포 입력을 위해 Rosin-Rammler /log-normal 분포를 사용하였으며 모델 상수의 영향을 살펴보았다. 또한 미세물분무의 분사압력에 따른 화재 제압특성을 이전의 실험 결과와 비교함으로써 해석 모델을 검증하고 열유동 특성 및 가스 농도 변화를 분석하였다. 결과로부터 동일한 평균입경을 갖는 미세 물분무도 액적분포의 특성에 따라 하부 위치에서의 액적 크기 및 속도에 큰 영향을 받고 있음을 확인할 수 있었다. 분무특성 에 대한 실험결과와의 비교를 통해 적절한 초기입경분포를 결정하였으며 이를 이용하여 화재 시뮬레이션을 진행하였다. FDS 화재 시뮬레이션 결과는 온도의 변화 및 화재 제압 특성에 대하여 실험 결과와 좋은 일치를 보여주었다. 또한 미세물분 무의 작동압력에 따른 열유동장 변화, 가스상 농도 변화의 예측에 있어 유용한 데이터를 제공할 수 있음을 확인하였다. The aim of the present study was to estimate the prediction performance of a FDS (Fire Dynamic Simulator) to simulate the fire behaviors and suppression characteristics by operating a water-mist. Rosin-Rammler/log-normal distribution function was used to determine the initial droplet distribution of water-mist and the effects of its model constant were considered. In addition, the simulation models were validated by a comparison of the predicted fire suppression characteristics with water-mist injection pressures to the previous experiments, and the thermal flow behaviors and gaseous concentration variations were analyzed. The results showed that water-mists with the same mean diameter were affected by the characteristics of the droplet size distribution, which have different size and velocity distributions at the downstream location. The fire simulations conducted in this study determine the initial droplet size distribution tuned to the base of the spray characteristics measured by previous experiments. The simulation results showed good agreement with the previous measurements for temperature variations and fire suppression characteristics. In addition, it was confirmed that the FDS simulation with a water-mist operation supplies useful details on estimations of the thermal flow fields and gaseous concentration under water mist operation conditions.
하이브리드 액정충돌모델을 이용한 분무간 충동시스템에 대한 수치해석적 연구
고권현(Gwon Hyun Ko),유홍선(Hong Sun Ryou),이성혁(Seong Hyuk Lee),방기영(Ki Young Bang) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1
The purpose of present study is to propose a new hybrid collision model for analyzing two impinging sprays under low and high pressure of gas phase and to assess it through comparisons with the original model of O'Rourke. The hybrid model proposes new criterion of collision threshold, including the effect of preferred directions of impinging droplets, and such a critical collision radius based on literature findings. In addition, the hybrid model considers the effect of the collision-induced disintegration, added to other three regimes, i.e. bouncing, separation and coalescence. Numerical simulations are carried out for mutual impingement system operating under low and high pressure of gas phase. The hybrid model is validated through comparisons between predictions and measurements for Sauter Mean Diameter (SMD) and penetration length. Findings through the present work include good predictability of the hybrid model compared to the O'Rourke model and the existence of optimal injection conditions under a specific situation
포스터 전시회 : 미세물분무의 작동에 대한 FDS 예측 성능 평가
고권현 ( Gwon Hyun Ko ),노경철 ( Kyoung Chul Ro ),김성찬 ( Sung Chan Kim ),이성혁 ( Seong Hyuk Lee ),유홍선 ( Hong Sun Ryou ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-
In this study, the prediction performance of FDS has been estimated on the suppression of diesel pool fires by water mist. A downward-directed nozzle produces a fine water spray over small-scale opposed diesel pool fires located at the center of compartment. At FDS simulation, the water mist injection conditions are tuned to mimic the droplet size and velocity measured at the experiment. The predicted temperature distribution of flame shows good agreements with the measurement before and after water mist activation