• 한국수소및신에너지학회논문집
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• 제20권3호
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• pp.188-193
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• 2009

Fuel cell vehicles are equipped with Pressure Relief Devices(PRDs) installed in pressure tank cylinder to prevent the explosion of the tank during a fire. PRDs are safety devices that perceive a fire and release gas in the pressure tank cylinder before it is exploded. But if the PRD does not actuate, because either the PRD fails or can't be surrounded by the flame of a fire, the tank will rupture and produce a blast wave and hydrogen fire ball. In this paper, we observed the fire behavior of actual fuel cell vehicle, comparing with that of gasoline vehicle.

• 한국음향학회지
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• 제36권5호
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• pp.314-320
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• 2017

일반적으로 감압밸브는 고압 가스에 의한 배관 파손을 방지하기 위해 설치된다. 그러나 감압 밸브를 지나면서 발생하는 급격한 압력 저하는 음향파의 형태로 전파되는 큰 음향 에너지를 발생 시키며, 하류 방향으로 전파되면서 배관의 벽면을 진동시키는 가진원으로 작용하여 배관의 파손을 유발한다. 따라서, 본 연구에서는 단순 수축-확장 배관을 대상으로 LES(Large-Eddy Simulation)기법과 파수-주파수 분석을 통해 유동장 내 비압축성 압력섭동과 압축성 압력 섭동을 분리하고, 밸브 유동에 의한 내부 유동소음을 예측하였다. 수치해석의 수렴성을 향상시키기 위해 먼저 정상상태 Reynolds-Averaged Navier-Stokes 방정식을 해석하여, 고정확도의 비정상 LES해석의 초기 값으로 활용하였으며, 비정상 유동장 결과로부터 파수-주파수 분석을 실시하였다. 파수-주파수 분석을 통해 비압축성 압력섭동과 압축성 압력섭동을 분리하였으며, 이를 통해 배관 내 음향유기진동에 의한 소음원 정보를 정확히 제공할 수 있음을 확인하였다.

• 한국자동차공학회논문집
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• 제18권3호
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• pp.95-103
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• 2010

This paper presents a simulation model of a double-acting high-speed pneumatic cylinder with a relief valve type cushion mechanism. The model predicts piston motion, mass flow rate, pressure and temperature time histories of cushion chamber. Of interest here is to investigate the cushioning effect of varying the piston and piston-rod diameter, cushion ring diameter and length, and stoke in cushion mechanism. As a result, this cushion mechanism is found to be adequate under high-speed driving of pneumatic cylinders. The simulation model proposed here will be very useful to analyze the dynamic characteristics and to improve or design the better cushion mechanism in high-speed pneumatic cushion cylinders.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1382-1399
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• 2023

Pressure relief valve (PRV) is one of the important control valves used in nuclear power plants, and its sealing performance is crucial to ensure the safety and function of the entire pressure system. For the sealing performance improving purpose, an explicit function that accounts for all design parameters and can accurately describe the relationship between the multi-design parameters and the seal performance is essential, which is also the challenge of the valve seal design and/or optimization work. On this basis, a surrogate model-based design optimization is carried out in this paper. To obtain the basic data required by the surrogate model, both the Finite Element Model (FEM) and the Computational Fluid Dynamics (CFD) based numerical models were successively established, and thereby both the contact stresses of valve static sealing and dynamic impact (between valve disk and nozzle) could be predicted. With these basic data, the polynomial chaos expansion (PCE) surrogate model which can not only be used for inputs-outputs relationship construction, but also produce the sensitivity of different design parameters were developed. Based on the PCE surrogate model, a new design scheme was obtained after optimization, in which the valve sealing stress is increased by 24.42% while keeping the maximum impact stress lower than 90% of the material allowable stress. The result confirms the ability and feasibility of the method proposed in this paper, and should also be suitable for performance design optimizations of control valves with similar structures.

• 드라이브 ㆍ 컨트롤
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• 제18권2호
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• pp.1-8
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• 2021

In this work, a circuit with a hydraulic power unit is formulated as a means of predicting the behavior of the prefill valve in the future. The behavior of the prefill valve can be examined by the measurements of the configured power unit, and the performance is determined by using hydraulic pumps, relief valves, and hydraulic hoses that make up the power unit. In particular, pressure/flow pulsation generated by hydraulic pumps can cause instability in the prefill valve and cause noise-induced degradation of the overall performance and reliability of the hydraulic system containing the prefill valve. Therefore, to study the behavior and performance of the prefill valve in a relatively accurate manner, the prediction of the characteristics of the hydraulic power unit driving the prefill valve is very important. In this study, the pulsation characteristics of the hydraulic pump were analyzed to theoretically demonstrate its relationship with different settings of the power unit, such as relief valve pressure settings and the presence/absence of the hose.

• Korean Chemical Engineering Research
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• 제55권2호
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• pp.170-179
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• 2017

본 논문은 소듐냉각고속로 원형로 소듐-물 반응 압력완화계통의 급수배출부와 수소방출부의 설계요건 도출을 목적으로 한다. 증기발생기 전열관 누설에 의한 소듐-물 반응 발생 시, 증기발생기 내의 급수 증기를 신속하게 배출하는 조건을 도출하기 위해 급수덤프탱크 가스방출배관의 단면적과 증기발생기 급수배출배관의 수직길이를 변화시켜 연구를 수행하였다. 정상운전과 재장전운전에 대해 각각 계산을 수행하여 급수덤프탱크 가스방출배관의 단면적과 증기발생기 급수배출배관의 수직길이를 결정하였다. 정상운전 조건에서 소듐-물 반응 발생 시, 생성물인 수소에 의해 형성되는 과압이 소듐덤프탱크의 설계압력을 만족시킬 수 있도록 하는 가스방출배관의 직경을 도출하였고, 이 때 대기로 방출되는 수소의 유량과 농도를 계산하였다. 본 논문의 계산결과는 향후 소듐냉각고속로 원형로의 소듐-물 반응 압력완화계통의 설계요건으로 활용될 예정이다.

• 상하수도학회지
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• 제26권5호
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• pp.693-703
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• 2012

Leakage in water supply system can cause water resources loss in addition to the water quality degradation. In this research, leakage reduction after establishment of a block system in the area with leakage rate of 69.0 % was investigated using EPANET simulation. The average water pressure for the research area was $5.17kgf/cm^2$ which was relatively high, and several sites were deviated from recommended water pressure ranges(i.e., 1.5 ~ $7.1kgf/cm^2$). However, the average water pressure in the area was reduced to 3.81 and $3.49kgf/cm^2$ after the introduction of block system with a water pressure relief valve(PRV) setting of 3.0 and $2.5kgf/cm^2$, respectively. Under the installation of a PRV with regulating pressure of $2.5kgf/cm^2$, the predicted leakage was reduced from $4,420.3m^3/d$ to $3,028.1m^3/d$, which was equivalent to the leakage reduction from 31.0 % to 23.5 %.

• 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.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.39-46
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• 2014

A total loss of all heat sinks is considered a severe accident with a low probability of occurrence. Following a total loss of all heat sinks, the degasser/condenser relief valves (DCRV) become the sole means available for the depressurization of the primary heat transport system. If a nuclear power plant has a total loss of heat sinks accident, high-temperature steam and differential pressure between the primary heat transport system (PHTS) and the steam generator (SG) secondary side can cause a SG tube creep rupture. To protect the PHTS during a total loss of all heat sinks accident, a sufficient depressurization capability of the degasser/condenser relief valve and the SG tube integrity is very important. Therefore, an accurate estimation of the discharge through these valves is necessary to assess the impact of the PHTS overprotection and the SG tube integrity of the primary circuit. This paper describes the analysis of DCRV discharge capacity and the SG tube integrity under a total loss of all heat sink using the CATHENA code. It was found that the DCRV's discharge capacity is enough to protect the overpressure in the PHTS, and the SG tube integrity is maintained in a total loss of all heat accident.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.520-526
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• 2011

In recent years, it is very important that hydrogen storage system is safe for user in any circumstances in case of crash and fire. Because the hydrogen vehicle usually carry high pressurized cylinders, it is necessary to do safety design for fire. The Global Technical Regulation (GTR) has been enacted for localized and engulfing fire test. High pressure hydrogen storage system of fuel cell electrical vehicles are equipped with Thermal Pressure Relief Device (TPRD) installed in pressured tank cylinder to prevent the explosion of the tank during a fire. TPRDs are safety devices that perceive a fire and release gas in the pressure tank cylinder before it is exploded. In this paper, we observed the localized and engulfing behavior of tank safety, regarding the difference of size and types of the tanks in accordance with GTR.