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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
TAB 모델과 수정된 액적 항력 모델을 이용한 공기 보조 분무에서의 액적 분열에 대한 수치적 연구
고권현(Gwon Hyun Ko),유홍선(Hong Sun Ryou),이성혁(Seong Hyuk Lee),홍기배(Ki Bae Hong) 한국자동차공학회 2002 한국 자동차공학회논문집 Vol.10 No.2
The aim of this article is to perform the numerical simulation for drop drag and breakup processes in airassisted sprays using the Taylor analogy breakup (TAB) model with a modified drop drag model, in which a random method is newly used to consider the variation of the drop's frontal area. The predicted results for drop trajectory and Sauter mean diameter (SMD) were compared with experimental data and the simulation results using the earlier published models such as TAB model, surface wave instability (Wave) model, and Wave model with original drop drag model. In addition, the effects of the breakup model constant, Ck, on prediction of spray behaviors were discussed. The results shows that the TAB model with the modified drop drag model is in better agreement with experimental data than the other models, indicating the present model is acceptable for predicting the drop breakup process in air-assisted sprays. At higher Weber numbers, the smaller Ck shows the best fitting to experimental data. It should be noted that more elaborated studies is required in order to determine the breakup model constant in the suggested model in the study.
[디젤엔진부문] 공기보조 분무에서 분산 모델들의 적용에 대한 수치 해석적 연구
고권현(Gwon-hyun Ko),유홍선(Hong Sun Ryou),이성혁(Seong Hyuk Lee) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A numerical study was performed for applications of earlier published breakup models to air-assisted liquid drop atomization. In this paper, the Taylor analogy breakup (TAB) model, the surface wave instability (WAVE) model, and the drop drag WAVE (DDW) model were used to simulate breakup processes for liquid drops. Liquid drops was injected into high-speed gas flows with various Weber numbers, taken as 72. 148. and 270, at room temperature. At high Weber number, all models showed good agreement with experimental results for parent drop trajectories. For all ranges of Weber number, the TAB model underestimated drop sizes, but the WAVE relatively showed good results. It was thought that the DDW model was acceptable for the computation of liquid drop breakup in air-assisted sprays.<br/> <br/>
극초고압 조건에서 디젤 분무 특성에 미치는 액적 항력 모델의 영향
고권현 ( Gwon Hyun Ko ),이성혁 ( Seong Hyuk Lee ),유홍선 ( Hong Sun Ryou ),이종태 ( Jong Tai Lee ) 한국분무공학회 2004 한국액체미립화학회지 Vol.9 No.3
N/A The present article investigates the influence of droplet drag models on predictions of diesel spray behaviors under ultra-high injection pressure conditions. To consider drop deformation and shock disturbance, this study introduces a new hybrid model in predicting drag coefficient from the literature findings. Numerical simulations are first conducted on transient behaviors of single droplet to compare the hybrid model with earlier conventional model. Moreover, using two different models, extensive numerical calculations are made for diesel sprays under ultra-high pressure sprays. It is found that the droplet drag models play an important role in determining the transient behaviors of sprays such as spray tip velocity and penetration lengths. Numerical results indicate that this new hybrid model yields the much better conformity with measurements especially under the ultra-high injection pressure conditions.
고권현(Gwon Hyun Ko),유홍선(Hong Sun Ryou),소성욱(Seong Wook Cho),이규봉(Gyu Bong Lee) 한국자동차공학회 2002 한국 자동차공학회논문집 Vol.10 No.4
The present article deals with the measurement and the numerical calculations for the temperature distribution near the facing of the lockup clutch. The rotating telemetry system is introduced for the estimation inside high-speed torque converter. For the numerical calculation, the effect of the convective heat transfer is considcred as well as thc conduction to the solid. The estimation shows that the oil temperature near facing rapidly rises as the lockup clutch is engaged. The numerical results shows good agreements with the experimental values for the maximum temperature near thc facing of the lockup clutch.
비등방성 난류특성을 고려한 분무의 벽면충돌 현상에 대한 수치해석 연구
고권현(Gwon Hyun Ko),유홍선(Hong sun Ryon),이성혁(Seong Hyuk Lee) 한국자동차공학회 2003 한국 자동차공학회논문집 Vol.11 No.3
It is an aim of this study to perform extensive numerical study for analyzing the anisotropic turbulence effects on spatial and temporal behaviors of diesel sprays after wall impingement. The turbulence model of Durbin7) is used for comparisons with the k-ε model. The turbulence-induced dispersions of droplets are considered to describe the anisotropy of turbulence effectively and the spray/wall interactions are simulated using the model of Lee and Ryou.6) The present study investigates the internal structures of impinging diesel sprays such as Sauter mean diameter (SMD), local droplet velocities, and local gas velocities and also compares the results predicted by two turbulence models with the experimental data. The Durbin's model considering the anisotropy of turbulence predicts both gas and droplet tangential velocities better than the k-εmodel does, It is concluded that the anisotropy of turbulence should be considered in simulating impinging diesel sprays.
스트레칭 분리 영역을 포함한 새로운 액적 충돌 모델의 개발
고권현(Gwon Hyun Ko),유홍선(Hong Sun Ryou) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
The present article proposes a new droplet collision model including the stretching separation regime and the formation of satellite droplets. The new model consists of a several equations to calculate the post-collision characteristics of colliding droplets and satellite droplets. These equations are derived from the energy balance of droplets between before and after collision. For binary collision of water droplets, the new model shows good agreement with experimental data for the number of satellite droplets. Nevertheless, it is thought that, in order to guarantee the generality of the new model, the improvements should be performed to consider the effects of the bouncing and the reflexive separation, which is essential process in the collision of hydrocarbon droplets.
[디젤엔진부문] 공동 현상 모델이 디젤분무의 예측에 미치는 영향에 대한 수치 해석적 연구
고권현(Gwon-Hyun Ko),유홍선(Hong Sun Ryou),이성혁(Seong Hyuk Lee) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The aim of this article is to investigate an importance of cavitation effect on numerical calculation for high-pressure diesel sprays. The nozzle flow model was used to take account of nozzle inlet configurations, cavitation effect, injection flow rate and chamber conditions. The KH/RT model published recently was also adopted for atomization and breakup processes. The numerical calculations were carried out for non-evaporative diesel sprays under different ambient conditions and the predicted results were compared with experimental data. The tip penetration and Sauter Mean Diameter(SMD) with considering the cavitation effect were in better agreement with experimental data than those obtained without considering the cavitation effect. In addition, the results showed that the cavitation could cause the increase of the atomization of liquid jet, resulting in producing smaller SMDs
충돌분무의 거동에 미치는 벽면곡률의 영향에 대한 수치해석 연구
고권현(Gwon Hyun Ko),유홍선(Hong Sun Ryou) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.3
In this paper a numerical study was performed for the effect of the wall curvature on the behaviors of fuel sprays impinging on the concave Surface. Actually, in the real diesel engines, a piston head has a curved shape for the experimental and numerical works had been performed on the spray/wall impingement phenomena, the curvature effect of impinged wall was rarely investigated, The wall curvature affects on the behaviors of the secondary droplets generated by impingement and the concave wall obstructs the droplets to advance from the impinging site to outward. In present study, the simulation code was validated for the flat surface case and three cases of the different curvature were calculated and compared with the flat surface case for several parameters, such as the spray radius, the spray height and the position of vortex center of gas phase. The simulation results showed that the radial advance of the wall spray and the vortex is decreased with increasing the curvature. It was concluded that the curvature of the impinged wall significantly affects the behaviors of both the gas-phase and the droplet-phase.