• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3088-3101
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• 2023

A pressurized vessel-pipe-safety valve (PVPSV) combination is a commonly used configuration in nuclear power plants, and a good numerical model is essential for the system design, sizing and performance optimization. However, owing to the large-scale and cross-scale features, it is still a challenge to build a system level numerical model with both high accuracy and efficiency. To overcome this, a novel system level modeling method which can synthesize the advantages of various models is proposed in this paper. For system modeling, the analytical approach, the method of characteristics (MOC) and the surrogate model approach are respectively adopted to predict the dynamics of the pressure vessel, the connecting pipe and the safety valve, and different models are connected through data interfaces. With this system model, dynamic simulations were carried out and both the stable and the unstable system responses were obtained. For the model verification purpose, the simulation results were compared with those obtained from experiments and full CFD simulations. A good agreement and a better efficiency were obtained, verifying the ability of the model and the feasibility of the modeling method proposed in this paper.

• 한국가스학회지
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• 제12권2호
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• pp.99-104
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• 2008

가스 정압기지 내의 가스 정압기는 배관 내의 높은 가스의 압력을 일정한 압력으로 낮추는 역할을 한다. 가스 정압기는 흐르는 가스의 유동을 제어할 뿐 아니라, 하류의 압력을 제어하는 데도 사용한다. 가스 정압기지의 안전성을 위해서 정압기와 정압기에 연결되어 있는 안전밸브의 유동 특성을 파악하는 것은 필수적이다. 따라서 본 연구에서는 정압기의 질량 유량 및 유동 특성을 다양한 입구 및 출구 압력 조건, 그리고 개도율에 대하여 수치해석 방법을 이용하여 알아보았다. 이러한 질량 유량에 대한 수치해석 결과는 정압기 제조사로부터 제안되는 실험 수식을 통하여 검증하였다. 결론적으로, 수치해석 결과와 실험 수식을 통해 얻어진 결과가 잘 일치함을 알 수 있다.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2509-2522
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• 2021

A valve assembly used in nuclear power plants must be qualified and supervised. New technical standards such as ASME QME-1 2007 particularly require detailed qualification using experiment and analysis. Particularly, diagnostic tests and engineering studies are required for qualification of ASME QME-1 2007. Among these studies, the research on the measurement of friction coefficient and packing stress is important. The irregular change of packing stress along the stroke distance occurs because of the abnormal phenomenon, which must be found and studied with quantitative methods. Packing stress should be analyzed conservatively through experimentation and analysis. In this study, various formulas were applied to measure and calculate coefficient of friction and packing stress. This study can be used in relation to qualification and supervision of packing materials. And the calculation using static diagnosis test can be used to find the packing frictional force in dynamic diagnosis test with flow pressure in a pipe. This study has made it possible to reliably consider packing frictional force generated in a valve body. And so, it is believed that more margin can be secured when evaluating the capacity of valve actuator by applying the accurate frictional force generated in the valve assembly.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2007년도 추계학술 발표회
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• pp.320-325
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• 2007

• 대한안전경영과학회지
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• 제16권2호
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• pp.211-216
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• 2014

Using a high-rise building water piping after hydrostatic test of the reliability of the leak to be completed if the pressure is maintained until the leak is not commercially available considered. Due to the nature of high-rise buildings and the construction period will take several years from the lower levels of use of the water supply and fire fighting water pipe construction is in progress, the order of which I do most of the first pipe to the construction and more than three years. So kind of riser pipe is complete, install the valve in the basement by installing an automatic pump to maintain a constant pressure after hydrostatic test and after each floor plumbing piping is complete, the progress of the hydrostatic test without undergoing a separate branch pipe the valve is opened automatically when the number of the pressing pressure of the structure. I kind of do and keep working pressure of pipe until the completion of the construction work to keep the damage to human error when it is intended to prepare. In winter, the frost protection and an alternative to drainage water pipe is damaged or deformed, even if unaware of the finishing work to the building, the use of the damage caused by a leak in a after construction of finish work to be expected. Alternative to reduce this damage if the pressure test without fear of freezing to help maintain long-term commercial pressures may be considered.

• 한국가스학회지
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• 제10권4호
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• pp.23-28
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• 2006

본 연구에서는 LPG 용기용 가스밸브의 강도 안전성과 몸체의 경량화 해석을 9개의 밸브모델에 대하여 유한요소해석 프로그램 MARC 및 다구찌의 실험적 설계법을 사용하였다. 가스밸브의 몸체에 작용하는 Von Mises 최대응력은 밸브에 작용하는 최대가스압력 $91kg/cm^2$을 적용하여 황동밸브 구조물의 안전성을 고찰하였다. 여기서 최대압력 $91kg/cm^2$은 LPG 가스용기의 안전계수를 고려한 것으로 안전성 해석이나 최적설계를 수행하는데 충분한 작동압력이다. 밸브몸체의 자중량을 줄이기 위해 수행된 해석은 LPG가스의 유동손실을 줄이고, 최적설계에 따라 소재가격을 낮출 수 있기 때문에 설계단계에서 고려해야 할 하나의 주요변수이다. 계산결과에 따르면, 최적설계 밸브모델은 9번이고, 이때의 최적설계 변수는 가스가 통과하는 밸브의 아래쪽 A의 반경 r=10mm, 위쪽 B의 반경 r=6mm, A와 B의 연결부 파이프 길이 l=2 mm로 결정되었다.

• 한국생산제조학회지
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• 제20권5호
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• pp.528-534
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• 2011

This study analyzes thermal stress and durability fatigue on the modelling of EGR valve. In case of 10% opening at its inlet, the minimum temperature gets cool as 3 times as inlet temperature. The maximum equivalent stress becomes lowest as the value of $2.6274{\times}109$ Pa and fatigue life becomes highest as 23.657 Cycle. But the minimum temperature gets cool as 2.2 times as inlet temperature in case of 50% opening at its inlet. The equivalent stress becomes higher and fatigue life becomes lower than in case of 10% opening. In case of 100% opening at its inlet, the minimum temperature gets cool as 0.2 times as inlet temperature. The equivalent stress becomes lower and fatigue life becomes higher than in case of 50% opening. Maximum equivalent stress and total deformation are shown at the closing of EGR valve by the pressure of inflow gas. The structural analysis result of this study can be effectively utilized with the design of EGR valve by investigating prevention and durability against its damage.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.741-747
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• 2010

발사체의 추진공급시스템에 사용되는 벤트/릴리프밸브는 안전밸브의 조합체로 극저온의 산화제를 주입할 때와 비행 중에 기화된 산소기체를 배출시킨다. 벤트/릴리프밸브의 설계검증을 위해 AMESim과 FLUENT 상용코드를 이용하여 밸브모델을 구성하였다. AMESim 밸브모델을 검증하기 위해 밸브의 개폐압력, 개폐작동시간을 수학적 계산결과와 비교하였고 내부유동해석 결과를 반영하여 모델의 정확도를 높였다. 본 연구에서는 설계인자를 검증 및 작동성능을 분석하였다. 이 결과는 한국형 발사체에 사용되는 다양한 규격의 벤트/릴리프밸브 개발과정의 효율성을 높일 수 있을 것으로 판단된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.676-681
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• 2001

ABS is a safety device, which adds hydraulic system to the existing brake system to prevent wheel from locking, so we can obtain maximum braking force on driving. The hydraulic system to control braking pressure consists of sol-flow type using solenoid valve, flow control valve or consists of sol-sol type using two solenoid valve. In this paper, the hydraulic system in ABS is composed of sol type using a 3port-2position solenoid valve, and vehicle system is composed of 1/4 vehicle model. And slip ratio is controlled using PWM (Pulse-Width-Modulation) control algorithm. Braking friction coefficient and tracking friction coefficient which are described by slip ratio's function have maximum value when slip ratio has its value from 0.1 to 0.3. And slip ratio is controlled constantly in this boundary value even in the variation of road's condition in some boundary.

• 에너지공학
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• 제24권2호
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• pp.40-44
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• 2015

중수로 일차냉각재계통 액체방출밸브의 개방압력에 대한 안전여유 및 시간지연을 반영하여 열수력코드로 경년열화가 반영된 노심에 대해 민감도를 평가하였다. 과거에는 안전해석을 수행할 때 안전여유와 시간지연을 반영하여 평가하지 않았으나, 월성1호기 안전해석 인허가 심사과정중 반영 평가하였다. 중수로 안전해석에서 압력경계는 일차냉각재계통 액체방출밸브이다. 따라서 액체방출밸브 응동이 안전해석에 직접적인 영향을 주므로 안전여유와 시간지연 부가가 안전해석 결과에 미치는 영향을 파악하고 해석에 반영하기 위해 일차냉각재계통 과압이 걸리는 사고들에 대해 평가하였다.