• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.5
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• pp.23-30
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• 2007

The effectiveness of a pogo suppression device (PSD) on the response of piping system simulating the propellant supply lines of the rocket engines was investigated experimentally by other researchers. In this study, the simplified analytical model was made, and the key parameters which are difficult to derive theoretically were identified in combination with the previous experimental work. In other words, the flow transient equations for a PSD system and the key parameters used to decide the instability of the system from the linearized transfer function including inertance, compliance, and resistance were derived. From the analysis, the values of key parameters could be determined from the experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1144-1147
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• 2017

It was reviewed about the pressure oscillation on the inlet of turbo-pump at the moment of engine startup and shutdown. Specially, This research was performed how much is the effect of PSD(Pogo Suppression Device) about the pressure oscillation on the inlet of turbo-pump at the moment of engine startup and shutdown. For analysis, propellant tank PSD and Engine are modelled with Flowmaster which is the commercial 1D program. As the analysis results, even though the PSD is installed in the pipeline, the pressure drop or rising at the moment of engine startup and shutdown is same compared to the case without PSD. However, it was confirmed that PSD reduces the pressure oscillation of the high frequency band as the original purpose of PSD.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.177-185
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• 2015

City-based Lifeline is expected to cause significant social and economic loss accompanied the secondary damage such as paralysis of urban functions and a large fire as well as the collapse caused by earthquake. Earthquake Disaster Response System of Korea is being operated with preparation, calculates the probability of failure of the facility through Seismic Fragility Model and evaluates the degree of earthquake disaster. In this paper, the time history analysis of buried gas pipeline in city-based lifeline was performed with consideration for ground characteristics and also seismic fragility model was developed by maximum likelihood estimation method. Analysis model was selected as the high-pressure pipe and the normal-pressure pipe buried in the city of Seoul, Korea's representative, modeling of soil was used for Winkler foundation model. Also, method to apply developed fragility model at GIS is presented.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.4
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• pp.368-375
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• 2013

Failure of small bore piping welds is a recurring problem at nuclear power plants. And the socket weld cracking in small bore piping has caused unplanned plant shutdowns for repair and high economic impact on the plants. Consequently, early crack detection, including the detection of manufacturing defects, is of the utmost importance. Until now, the surface inspection methods has been applied according to ASME Section XI requirements. But the ultrasonic inspection as a volumetric method is also applying to enforce the inspection requirement. However, the conventional manual ultrasonic inspection techniques are used to detect service induced fatigue cracks. And there was uncertainty on manual ultrasonic inspection because of limited access to the welds and difficulties with contact between the ultrasonic probe and the OD(outer diameter) surface of small bore piping. In this study, phased array ultrasonic inspection technique is applied to increase inspection speed and reliability. To achieve this object, the 3.5 MHz phased array ultrasonic transducer are designed and fabricated. The manually encoded scanner was also developed to enhance contact conditions and maintain constant signal quality. Additionally inspection system is configured and inspection procedure is developed.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.51-57
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• 2019

A plant layout problem has a large impact on the overall construction cost of a plant. When determining a plant layout, various constraints associating with safety, environment, sufficient maintenance area, passages for workers, etc have to be considered together. In general plant layout problems, the main goal is to minimize the length of piping connecting equipments as satisfying various constraints. Since the process may suffer from the heat and friction loss, the piping length between equipments should be shorter. This problem can be represented by the mathematical formulation and the optimal solutions can be investigated by an optimization solver. General researches have overlooked many constraints such as maintenance spaces and safety distances between equipments. And, previous researches have tested benchmark processes. What the lack of general researches is that there is no realistic comparison. In this study, the plant layout of a real industrial C3MR (Propane precooling Mixed Refrigerant) process is studied. A MILP (Mixed Integer Linear Programming) including various constraints is developed. To avoid the violation of constraints, penalty functions are introduced. However, conventional optimization solvers handling the derivatives of an objective functions can not solve this problem due to the complexities of equations. Therefore, the PSO (Particle Swarm Optimization), which investigate an optimal solutions without differential equations, is selected to solve this problem. The results show that a proposed method contributes to saving the capital expenditures.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.582-585
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• 2016

This study intends to provide initial evacuation distances for the public in case of accidental releases of hydrogen fluoride (HF). HF is a very toxic chemical that is widely used in the chemical, electrical, and electronics industries. Consequence modeling programs, such as ALOHA and PHAST, were used to help formulate a contingency plan in case of an HF leak. For the purpose of this study, the release of entire quantity of HF in 10 min is defined as a worst-case scenario and the release from a partial line rupture is used as an alternative case scenario as National Institute of Chemical Safety (NICS) guidelines. Once the discharge rates were calculated based on the scenarios, the ERPG-2 endpoint distances have been obtained for representative daytime and nighttime weather conditions. This paper presents graphs that can be used to enact swift evacuation orders and emergency response plans in the case of accidental releases of HF.

• The Transactions of the Korea Information Processing Society
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• v.5 no.4
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• pp.1044-1047
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• 1998

Non-destructive x-ray inspection system needs image intensifier to obtain the x-ray image. Captured image from image intensifier is distorted because the input plate of image intensifier has a spherical surface. In the research, in order to compensate this image distortion, we created the model of image intensifier and show mathematically that the image distortion was compensated. To show the performance of the proposed method, experiment was performed in real x-ray inspection system.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.534-541
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• 1997

1000MWe급 피동형원자로기 안전계통 성능 및 RELAP5 코드의 적용성 평가를 목적으로 AP600을 참조노형으로 설정된 1000MWe급 대용량 피동형원자로에 대한 냉각재 상실사고를 모의 해석하였다. 대형냉각재상실사고시 발생되는 현상들은 기존 원자로와 큰 차이가 없고, 이들 현상을 모의하기 위한 모델링 요건들이 피동형계통 분석에 동일하게 요구되었으며, 계산된 PCT가 규제기관의 허용치에 충분한 여유도를 갖고 있어 대형냉각재상실사고시 충분한 노심냉각 능력을 갖는 것으로 평가되었다. 또한 안전주입 배관이 파단되는 소형냉각재 상실사고를 해석한 결과 KP1000의 피동안전계통은 ADS의 작동에 의하여 노심을 노출시키지 않고 적절한 사고완화 기능을 수행할 수 있는 것으로 분석되었다.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.70-76
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• 2013

Several finite element models for the leak-before-break (LBB) assessment of overlay dissimilar metal weldment were constructed and analyzed to develop a simple finite element modeling method. The J-integral, crack opening displacement (COD) and J-integral distribution along the crack front in thickness direction due to the applied moment were obtained from the analysis results of the constructed finite element models, and studied compared to the previous literatures. It is concluded that the modeling with base material only is simple and produces a slightly conservative results compared to the complex modeling composed with weld metal and base metal in the calculation of J-integrals and COD values which are used for the calculation of fracture toughness and postulated leakage crack length respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.87-91
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• 1997

This paper presents the modeling and analysis of dynamic characteristics of hydraulic snubber in electric power plant. The nonlinear state equations of 9th order to describe the dynamics of the snubber was established by Sirnulink. The simulation results show that the hydraulic snubber reacts as like the conventional shock absolvers to the high pulse shock load. The snubber also shows the peculiar characteristics to the small step load, which are temporary locking displacements of control valves and same steady-state pressures of all internal chambers in the snubber.