• 한국기계가공학회지
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• 제21권7호
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• pp.28-33
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• 2022

In this study, we analyze the flow characteristics according to the internal shape of a 700bar hydrogen charging gun for hydrogen electric vehicles. When charging hydrogen, it receives a high-pressure charging pressure. At this time, we analyze the flow characteristics according to the shape of the nozzle and find the shape of the nozzle that minimizes energy loss. Ultimately, the optimal design of the nozzle was obtained by comparing the pressure difference between the inlet pressure and outlet pressure under a fixed mass flow condition.

• 한국수소및신에너지학회논문집
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• 제34권1호
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• pp.26-31
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• 2023

In this study, in order to propose a modular method for type IV high aspect ratio modular hydrogen storage vessel, a numerical analysis was conducted on the heat transfer behavior in series and parallel connection methods, and the differences according to each connection method were reviewed. Computational fluid dynamics software was used to check the internal temperature and pressure values of the hydrogen storage container under charging conditions. In terms of thermal safety when charging hydrogen gas, it was confirmed that the parallel modularization method was superior.

• 한국수소및신에너지학회논문집
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• 제33권4호
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• pp.284-292
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• 2022

Hydrogen is promising a candidate for energy supporting the carbon neutrality policy for greenhouse gas reduction, which is being promoted in several countries, including Korea. Although challenging efforts-such as lowering the costs of green hydrogen production and fuel cells-remain, hydrogen fuel cell electric vehicles (FCEVs) are expected to play a significant role in the energy transition from fossil fuels to renewable energy. In line with this objective, the hydrogen FCEV working group in the International Organization for Standardization (ISO) compiled and revised international standards related to hydrogen refueling stations as of 2019. A well-established hydrogen quality management system based on the standard documents will increase the reliability of hydrogen charging stations and accelerate the use of FCEVs. In this study, among the published ISO standards and other references, the main requirements for managing charging stations and developing related techniques were summarized and explained. To respond preemptively to the growing FCEV market, a continuous hydrogen quality monitoring method suitable for use at hydrogen charging stations was proposed.

• Archives of Metallurgy and Materials
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• 제67권4호
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• pp.1491-1495
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• 2022

The present research deals with the effect of pre-strain on the hydrogen embrittlement behavior of intercritically annealed medium-Mn steels. A slow strain-rate tensile test was conducted after hydrogen charging by an electrochemical permeation method. Based on EBSD and XRD analysis results, the microstructure was composed of martensite and retained austenite of which fraction increased with an increase in the intercritical annealing temperature. The tensile test results showed that the steel with a higher fraction of retained austenite had relatively high hydrogen embrittlement resistance because the retained austenite acts as an irreversible hydrogen trap site. As the amount of pre-strain was increased, the hydrogen embrittlement resistance decreased notably due to an increase in the dislocation density and strain-induced martensite transformation.

• 한국가스학회지
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• 제18권1호
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• pp.61-67
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• 2014

고강도 DP강의 수소취성 거동을 소형펀치시험을 통해 평가하였다. 이를 위해 첨가원소가 각기 다른 3종의 DP강 시험편에 전기화학적 방법으로 수소를 강제 주입시켰다. 수소주입 후, 수소주입량을 측정하였다. 수소주입량은 마르텐사이트 부피분율에 크게 의존하는 것으로 조사되었다. 전류밀도 150, $200mA/cm^2$ 조건에서 25시간이 포화상태에 도달하는 수소주입조건으로 나타났다. SP시험 후 SP에너지와 SP bulb 형상을 비교한 결과, 수소주입량의 증가에 따라 SP에너지와 SP bulb 높이가 감소하는 것으로 나타났다. 또한 SP bulb 파단면에서는 뚜렷한 facet와 층상형태의 벽개 파단면이 관찰되어 수소취성화를 관찰할 수 있었다.

• 한국가스학회지
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• 제18권5호
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• pp.40-46
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• 2014

전기화학적 방법으로 수소 주입시킨 5종의 고강도 DP강의 수소취성화 정도를 소형펀치시험으로 평가하였다. SP시험 후 SP흡수에너지는, $200mA/cm^2$ 전류밀도 조건의 DP5 시험편에서 수소주입시간이 5hr에서 50hr으로 증가함에 따라 363 kgf-mm에서 209 kgf-mm로 현저히 저하되는 것을 알 수 있었다. 전류밀도와 수소주입시간의 증가에 따라 수소주입량과 SP에너지 저하는 선형적인 상관관계를 갖는 것으로 조사되었다. 또한 SP시험에 의해 생성된 bulb의 높이 변화는 1.79 mm에서 1.59 mm로 낮아지는 것으로 조사되었다. 이는 앞서의 SP 흡수에너지 결과와 유사한 경향으로 나타나, 수소취성평가의 지표로 활용 가능할 것으로 사료된다. 균열 파단부위의 SEM 관찰에서 수소주입량 증가에 따라 파단면은 취성파면 형태로 진행되는 것을 확인할 수 있었다.

• 한국산업융합학회 논문집
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• 제26권4_2호
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• pp.705-713
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• 2023

The phenomenon of abnormal climate conditions resulting from greenhouse gas-induced global warming is increasingly prevalent. To address this challenge, global initiatives are underway to adopt environmentally friendly, zero-emission fuels. In this study, we investigate the hydrogen embrittlement characteristics of materials used for eco-friendly hydrogen storage systems. The effects of hydrogen embrittlement on austenitic stainless steels of the FCC series and structural steel of the BCC series were examined. Initially, test samples of three different steel types were prepared in 2t and 3t sizes, and hydrogen was injected into the specimens using an electrochemical method over a 24-hour period. Subsequently, a universal material testing machine (UTM) was employed to monitor changes in mechanical strength and elongation. The FCC series stainless steels exhibited a tendency for elongation to decrease, indicating low sensitivity to hydrogen. In contrast, the mechanical strength and elongation of the BCC series steel changed significantly upon hydrogen charging, posing challenges for prediction. The results of the present study are expected to serve as a fundamental database for analyzing the impact of hydrogen embrittlement on both FCC and BCC series steel materials.

• 한국가스학회지
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• 제25권4호
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• pp.57-62
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• 2021

본 연구는 국제공동 연구로 개발 된 HyKoRAM 프로그램을 이용하여 저장설비(튜브트레일러)의 누출 시 위험성평가를 진행하였다. 수소충전소 내의 고압가스설비는 크게 4가지로 저장설비(튜브트레일러), 처리설비(압축기), 압축가스설비, 충전설비(디스펜서)로 분류된다. 그 중 저장설비인 튜브트레일러의 설계 사양, 주변 환경 조건 등을 반영하여 기존에 발생된 사고 및 잠재적 사고 위험 사고 시나리오를 구성하였다. 이를 통해, 수소충전소 저장 설비의 위험을 확인하고 수소충전소 안전성 향상을 위한 대책을 제안한다.

• 한국수소및신에너지학회논문집
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• 제34권1호
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• pp.17-25
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• 2023

The purpose of this study was to propose a design that shows optimal performance by changing the geometry of the internal flow path of the receptacle in order to prevent the decrease in flow rate and differential pressure performance due to the application of the receptacle in the hydrogen charging system. To achieve this, 3D computational fluid dynamics simulation was performed for the receptacle, according to the geometry of the flow path inside the receptacle. The pressure results at the inlet and outlet were measured the same as both of N and H₂ in the experiment, and the flow rate of H₂ was 3.75 times higher than that of N₂. In addition, since the flow performance of the receptacle improved under conditions where the flow path was widened, it was confirmed that reducing the diameter of the poppet and the width of the guide are advantageous for improving performance.

• 한국수소및신에너지학회논문집
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• 제34권5호
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• pp.497-504
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• 2023

This study analyzes pressure distribution and pressure drop in the receptacle used in charging system of hydrogen fuel cell vehicles. The objective is to minimize receptacle-induced pressure drop by redesigning internal flow channels. Through numerical simulations, three receptacle variants are compared with a baseline case. Results show reduced pressure drop in the filter section. However, the check valve section exhibits higher pressure drop, requiring further improvement. By increasing throat diameter, pressure drop is decreased by 28% between inlet and outlet of the receptacle. This study shows the relationship between dynamic pressure and pressure drop, providing a guideline for receptacle performance optimization. The redesigned receptacle offers potential for enhancing hydrogen charging efficiency.