• 한국분무공학회지
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• 제22권1호
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• pp.13-21
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• 2017

The fog screen is a device projecting the media to the aerosol flow field. As major parameters to generate dense and steady fog screen, shear stress, optical blockage ratio and SMD were obtained result through experiment. The micro droplet was generated by the piezo oscillation element, and the aerosol flow mixed with an air flow was sprayed into the vertical direction from the top of the fog screen through the 280 mm slot. For produce a dense, uniform fog screen, the shear effect, optical blockage ratio and SMD between aerosol and air curtain were measured. The minimum and maximum shear stress conditions were selected and it was confirmed that the optical transmission deviation of the aerosol flow field was small when the aerosol and air curtain flow rates were changed. When the aerosol and air curtain flow power were 18 V (1.51 m/s) and 24 V (2.55 m/s), respectively, under the condition of the minimum shear stress and laminar flow, the optical blockage ratios with the spray length were small, and it produced a most stable and high density uniform fog screen by injecting a constant of $10{\mu}m$ or less.

• 한국해양공학회지
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• 제27권2호
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• pp.47-52
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• 2013

A subsea chemical injection system treats blockage problems in a subsea production system. It is important to treat problems quickly, because production delays cause fatal profit losses in a subsea production system. Therefore, the subsea industry requires a relatively higher reliability level for a production system compared to other industries. In this study, a subsea chemical injection system (linked to a control system) to inject chemicals into a subsea X-mas tree was analyzed. By using FSA (Formal Safety Assessment), the risk factors were defined and a quantitative risk analysis utilizing FTA (Fault Tree Analysis) and ETA (Event Tree Analysis) was performed. As a result, the effectiveness of a risk reduction option was evaluated.

• 한국추진공학회지
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• 제7권2호
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• pp.44-53
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• 2003

KSR-III의 추진시스템 종합성능시험과 단인증시험을 위한 수직형 연소시험시설이 구축되었다. 이러한 시험은 발사체에 준하는 단품을 사용하는 시험으로, 상대적으로 낮은 수준의 안전율 하에서 시험이 진행되게 된다. 이에 연소시험 안전대책의 하나로 엔진부에 대한 비상정지 시스템이 검토되었으며, 정확하고 빠른 판단을 위하여 연소실 압력과 가속도신호를 사용하는 비상정지 시스템이 구축되었다. 이러한 측정변수를 통하여 점화지연 및 실패, 소화, 추진제 공급상태, 불안정 연소, 구조물 과도진동 등을 감시할 수 있었으며, 이상 상황인지 후 빠르게 시험을 중단할 수 있었다. 이처럼 빠른 판단과 후속조치로 시험의 안전을 확보할 수 있었으며, 목적한 개발시험을 안전하게 마칠 수 있었다.

• Advances in aircraft and spacecraft science
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• 제10권3호
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• pp.203-222
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• 2023

The detonation combustion is a supersonic combustion process follows on shock wave oscillations in detonation tube. In this paper numerical studies are carried out combined effect of blockage ratio and spacing of obstacle on detonation wave propagation of hydrogen-air mixture in pulse detonation combustor. The deflagration to detonation transition of stoichiometric (ϕ=1)fuel-air mixture in channel has been analyzed for effect of blockage ratio (BR)=0.39, 0.51, 0.59, 0.71 with spacing of 2D and 3D. The reactive Navier-Stokes equation is used to solve the detonation wave propagation mechanism in Ansys Fluent platform. The result shows that fully developed detonation wave initiation regime is observed near smaller vortex generator ratio of BR=0.39 inside the combustor. The turbulent rate of reaction has also a great significance role for shock wave structure. However, vortices of rapid detonation wave are appears near thin boundary layer of each obstacle. Finally, detonation combustor demonstrates the superiority of pressure gain combustor with turbulent rate of reaction of 0.6 kg mol/m3 -s inside the detonation tube with obstacle spacing of 12 cm, this blockage enhanced the turbulence intensity and propulsive thrust. The successful detonation wave propagation speed is achieved in shortest possible time of 0.031s with a significance magnitude of 2349 m/s, which is higher than Chapman-Jouguet (C-J) velocity of 1848 m/s. Furthermore, stronger propulsive thrust force of 36.82 N is generated in pulse time of 0.031s.

• 한국컴퓨터정보학회논문지
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• 제25권5호
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• pp.11-18
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• 2020

본 연구는 컨베이어 시스템에서 딥러닝을 이용한 배출구 막힘 판단 기술에 대하여 제안한다. 제안 방법은 산업 현장의 CCTV에서 수집한 영상을 이용하여 배출구 막힘 판단을 위한 다양한 CNN 모델들을 학습시키고, 성능이 가장 좋은 모델을 사용하여 실제 공정에 적용하는 것을 목적으로 한다. CNN 모델로는 잘 알려진 VGGNet, ResNet, DenseNet, 그리고 NASNet을 사용하였으며, 모델 학습과 성능 테스트를 위하여 CCTV에서 수집한 18,000장의 영상을 이용하였다. 다양한 모델에 대한 실험 결과, VGGNet은 99.89%의 정확도와 29.05ms의 처리 시간으로 가장 좋은 성능을 보였으며, 이로부터 배출구 막힘 판단 문제에 VGGNet이 가장 적합함을 확인하였다.

• 대한조선학회논문집
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• 제57권3호
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• pp.133-139
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• 2020

In order to study the resistance test technique for the submerged body in Large Cavitation Tunnel (LCT), DARPA Suboff, submarine model publicly available was manufactured. DTRC released the resistance test data of DARPA Suboff conducted at ship speeds up to 18.0 knots in high-speed towing tank in 1990. As LCT is considered restricted waterways with walls, the resistance test results must be corrected with three wall blockage effects called buoyancy effect, solid blockage effect and wake blockage effect. Before correction, the resistance of LCT was 16~20 % higher than that of DTRC. After correction, the resistance and the resistance coefficients were compared with those of DTRC. The corrected resistance of LCT shows good agreement with that of DTRC. The residual resistance coefficient shows the difference according to the calculation method of buoyancy and frictional resistance coefficient. This paper suggests the best way for the calculation of residual resistance coefficient, On the basis of the present study, it is thought that the operating conditions for the propeller cavitation and noise tests can be drawn through LCT tests.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.425-432
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• 2002

Both numerical and experimental studies on sedimentation efficiency of a sedimentation bed were carried out. Three different structures of sedimentation bed and five different combinations of blockage ratio of center feed wall and angle of distributor are implemented to find the optimal values of geometric parameters. The effect of rotation of the distributor on sedimentation efficiency is also investigated. It reveals that the effect of blockage ratio and angle of distributor on sedimentation efficiency is considerable, while rotation effect can be neglected, and that calculated efficiencies show good agreements with those of experiment, qualitatively.

• 대한기계학회논문집B
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• 제23권2호
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• pp.166-174
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• 1999

The flow characteristics of 2-valve and 4-valve cylinder heads with various blocked-valve were experimentally investigated in a steady flow rig. Effects of the blocked-valve configurations on flow coefficient, swirl and tumble intensity are studied. Compared to the conventional valve, the blocked valve in both cylinder heads have the much lower flow coefficient and the much higher intensity of swirl and tumble. Under the same size of blockage, the value of flow coefficient and swirl(or tumble) intensity were varied according to the position of blockage. Throughout these steady flow test the optimized positions of blockage in both cylinder heads were determined.

• 한국유체기계학회 논문집
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• 제6권2호
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• pp.54-61
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• 2003

Both numerical and experimental studies on the sedimentation efficiency of a sedimentation bed were carried out. Three different structures of sedimentation bed and five different combinations of blockage ratio of center feed wall and angle of distributor are implemented to find the optimal values of geometric parameters. The effect of rotation of the distributor on sedimentation efficiency is also investigated. It reveals that the effects of blockage ratio and angle of distributor on sedimentation efficiency are considerable, while rotation effect can be neglected, and that calculated efficiencies show good agreements with those of experiment, qualitatively.

• 대한기계학회논문집
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• 제19권2호
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• pp.509-518
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• 1995

A study for the flame stability and the combustion characteristics of coaxial diffusion flame was conducted. The fuel employed was natural gas. The experimental variables were rim thickness of fuel tube, blockage ratio of the outer diameter of fuel tube to the inner diameter of air tube, and momentum ratio of fuel to air. It was consequently found that the stability in the neighborhood of the fuel rim depended on the rim thickness, especially in the case of above 3 mm, and that the stable region of the flame extended remarkably due to the formation of recirculation zone above rim. The effect of the blockage ratio on the flame stability was found to be minor in the case of above 3 mm of rim thickness. Between the momentum ratio 2 and 3, the stable flame zone was widely established as well good combustion. With increasing the fuel-air momentum ratio, axial velocity, turbulence intensity, and Reynolds stress increased.