• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.19-25
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• 2007

A LNG safety valve functions to control a constant pressure inside the LNG line of transportation, and the flow through it accompanies with noise and vibration which affect adversely on the system. The present study aims at understanding the flow physics of LNG safety valve for a practical design of LNG safety valve. A computational work using the two-dimensional, axisymmetric, compressible, Navier-Stokes equations is carried out to simulate the gas flow through the LNG safety valve, and compared with the theoretical results. It is found that the shape of valve sheet and the gap size are the key parameters in determining the gas dynamic forces on the valve sheet, and there exists a distance between nozzle exit and valve sheet in which the thrust coefficient at the valve sheet increases abruptly.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.551-556
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• 2007

High pressure storage of the agent gas in fire suppression system was composed of tank, main valve and safety valve, which prevents the fracture of the high pressure storage. The safety valve has circular thin plate as fracture plate that was destroyed over fracture pressure. When inner pressure of the storage is reached the fracture pressure, the safety valve discharges gas and degrades simultaneously the inner pressure of the storage. There are design variables such as flow path diameter, inner diameter of the plastic packing ring, thickness of plate and fillet radius. In this variables, thickness of plate is set to be a value of 0.2mm. The main effect of variables on the inner pressure, has been decided using factorial design and statistical analysis. Therefore, the relation of variables are expressed by regression equation. It is disclosed results that the difference of fracture pressures between the equation and experiment has $2{\sim}5%$. Finally, using response surface method, the optimal design of the safety valve could be decided with safety pressure of 25MPa, where the fracture occurs on circular thin plate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2090-2097
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• 1992

In this paper, fluttering behavior of mechanical monloleaflet heart valve prosthesis was analyzed taking into consideration of the impact between the valve occluder and the stopper. The motion of valve occluder was modeled as a rotating system, and equations were derived by employing the moment equilibrium conditions. Lift force, drag force, gravity and buoyancy were considered as external forces acting on the valve occluder. The 4th order Runge-Kutta method was used to solve the equations. The results demonstrated that the occluder reaches steady eguilibrium position only after damped vibration. The mean damping ratio is in the range of 0.197-0.301. Fluttering frequency does not have any specific value, but varies as a function of time. It is in the range of 11-84Hz. Valve opening appears to be affected by the orientation of the valve relative to gravitational forces.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.122-128
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• 2012

Many of the liquid rocket engines use a hypergolic igniter with rupture disc ends located in the combustion chamber ignition line. In this study, the flow coefficient tests of the igniter, which have a solenoid valve upstream, were performed. The tension-type rupture discs for radial and circumferential scores and the igniter with them were tested using water at room temperature. The effects of the score, flow rate, the disc thickness, gas pocket and the solenoid valve on the coefficient were analyzed.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.510-515
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• 1993

본 연구에서는 저속에서도 시스템의 자세 제어가 용이하게 하기 위하여 추진기 뒤에 제어판이 위치하도록 설계하였으며, 일반 서보 시스템과는 달리 무게와 공간 제약이 크고, 제어판 운동에 따른 외란 등록성의 변화가 심하므로 push-pull 형태의 소형, 고출력 편로드 복동 복수 실린더의 작동기를 설계하였다. 또한 일반적으로 서보밸브와 작동기는 일체형으로 설계되나 본 시스템의 공간상 심한 제약으로 인하여 서보밸브와 작동기를 분리하는 방법으로 구조설계를 하고 그 사이 유로는 매니폴드식으로 하여 동력전달을 하였다. 설계된 구동장치를 실제 정밀제작하여 실험을 수행하였으며, 시뮬레이션 결과와 실험에 의하여 얻어진 결과를 비교 분석하여 설계의 타당성 및 시스템의 성능을 검증하였다. 고속 수중운동체에 대하여 저속에서 자세제어를 용이하게 하고, 제한된 좁은 설치공간의 문제점을 해결하기 위하여 1) 추진기 후미에 독립된 4개의 상, 하, 좌, 우 제어판 설치 2) 서보밸브는 몸체에, 작동기는 Tail Tube에 분리 작동 설계 3) 소형의 편로드 복동 복수 실린더로 설계 구성된 유압식 구동장치는 시뮬레이션과 실험 결과를 통하여 시스템의 타당성을 입증하였다. 그러므로, 개발한 구동장치는 저속에서도 큰 제어력으로 자세 제어가 용이하기 때문에 얕은 수심에서 발사시 예상되는 위험 요소를 상다ㅇ 개선 시키므로써 운용범위의 다양화를 가져 올것으로 기대된다.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.55-63
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• 2021

In this study, a numerical methodology is proposed for evaluating valve flow noise in a pipe conveying high pressure gas, and the effects of perforated plates on reduction of such valve flow noise are quantitatively analyzed. First, high-accurate unsteady compressible Large Eddy Simulation techniques are utilized to predict flow and flow noise by a valve in a high-pressure pipe. The validity of the numerical result is confirmed by comparing the predicted wall pressure spectrum with the measured one. Next, the acoustic power of downstream-propagating acoustic waves due to the valve flow is analyzed using an acoustic power formula for acoustic waves propagating on mean flow in a pipe. Based on the analysis results, perforated plates are designed and installed downstream of the valve to suppress the valve flow noise and the acoustic power of downstream-going acoustic waves is predicted by using the same numerical procedure. The reduction by 9.5 dB is confirmed by comparing the predicted result with that of the existing system. Based on these results, the current numerical methodology is expected to be used to reduce valve flow noise in an existing system as well as in a design stage.

• Journal of the Korean Vacuum Society
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• v.4 no.2
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• pp.124-134
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• 1995

포항가속기연구소에서는 PLS 2-GeV 선형가속기 클라이스트론의 교체 및 보수시에 사용하기 위하여, 80 MW급 S-band의 도파관 밸브를 개발중에 있다. PLS형 도파관 밸브는 결합수단 없이 대전력을 전송할 수 있는 구조로 설계되어, 전력전송에 대한 제한을 받지 않는 특징을 갖는다. 본 도파관 밸브의 주요구성부는 밀착구동체를 갖는 U자형 도파관부, 두 개의 H-코너가 부착된 진공함, 그리고 두 개의 Viton O-링이 장착된 진공기밀판으로 이루어져 있다. 시제품용 도파관 밸브의 특성조사 결과, 펄스폭 3.5 $\mu$sec, 반복율 30 Hz에서 65MW의 전력전송을 얻을 수 있었다. 본 논문에서는 PLS도파관 밸브의 설계 개념, 기계적 특성 및 가공의 순으로 자세히 논할 것이며, 또한 현재까지의 실험결과 및 앞으로의 계획에 대하여 보고하기로 한다.

• The KSFM Journal of Fluid Machinery
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• v.17 no.3
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• pp.65-70
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• 2014

The effectiveness of a perforated plate installed additionally at butterfly valve to reduce cavitation which can cause vibration, noise, erosion, and flow path blockage has been investigated using CFD. Rayleigh-Plesset equation was applied to simulate cavitation phenomena. 3D flow simulations have been performed for 6 cases to consider the occurrence of cavitation at the downstream of the valve. From the present results, the perforated plate was thought to be very effective to suppress the cavitation inside of the pipe.

• Journal of the Korean Institute of Gas
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• v.24 no.4
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• pp.32-38
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• 2020

Based on the cases of fire and explosion accident in the chemical reactor, thr problems of preventive measures installed in the chemical reactor were analyzed. The chemical reactors produce a variety of chemicals and install rupture disk to relieve the pressure that rises sharply in the event of a runaway reaction. In order to maintain the function of the rupture disk, the emissions was allowed to be discharged into the atmosphere, resulting in fire and explosion accidents. As a way to improve this, safety instrumented system based on the safety integrity level(SIL3) was applied as a preventive measures for chemical reactor. Two emergency shur-off valves are installed in series on pipe dropping raw materials for chemical reactor so that the supply of raw materials can be cut off even if only one of the two emergency shut-off valves is operated during the runaway reaction. The automatic on/off valve is installed in parallel in the supply pipe of the reaction inhibitor so that the reaction inhibitor can be injected even if only one valve is opened at the time of the runaway reaction.

• Journal of the Korean Institute of Gas
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• v.17 no.3
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• pp.14-19
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• 2013

This paper presents an experimental study on the safety of a valve for a special gas cylinder. The test valves that were randomly dismantled from the special gas cylinder were experimented on the gas leakage and operation safeties. The crack, wear and deformation of the valve body, screw thread, safety disk, vent hole, stem and handle components that may affect to the gas leakage safety of a used valve were not found in this experimental study. A painted handle of a valve was partly stripped from the coated surface, and the surface of PT screw of a used valve body was rusted. But, these paint and rust problems do not affected to the gas leakage safety of used valves. And there was no gas leakage in the dismantled valve, and the permanent deformation and partial scars of a valve stem and O-rings were observed on the rubbing surfaces. Thus, the valve seat and O-rings are recommended to be replaced for a gas leakage safety of a dismantled valve. And it is necessary to repair and inspect handle fastening forces for a safe opening and closing operations of a valve.