• 전력전자학회논문지
• /
• 제27권2호
• /
• pp.150-156
• /
• 2022

This study proposes a design method of fuel cell DC/DC converter using in 5-ton forklift. For efficient hydrogen usage, targeted fuel cell system recirculates discarded hydrogen after fuel cell reaction. Recirculating hydrogen contains much impurities that reduces output power, increasing pressure that can damage the internal fuel cell reaction system. The proposed DC/DC converter effectively converts fuel cell power considering the voltage drop rate to reflect the recirculating hydrogen. Then, frequency control method is used to regulate the current ripple amount for battery and fuel cell hybrid configuration. Proposed power converter system design and control methods are verified in a practical fuel cell system that implements recirculating hydrogen.

• 한국분말재료학회지
• /
• 제17권1호
• /
• pp.23-28
• /
• 2010

HDDR treated anisotropic Nd-Fe-B powders have been widely used for the sheet motors and the sunroof motors of hybrid or electric vehicles, due to their excellent magnetic properties. Microstructural alignment of HDDR treated powders are mostly depending on the hydrogen reaction in disproportionation step, so the specific method to control hydrogenation reaction is required for improving magnetic properties. In disproportionation step, hydrogenation pressure and reaction time were controlled in the range of 0.15~1.0 atm for 15~180 min in order to control the micorstructural alignment of $Nd_2Fe_{14}B$ phase and, at the same time, to improve remanence of HDDR treated magnet powders. In this study, we could obtain a well aligned anisotropic Nd-Fe-B-Ga-Nb alloy powder having high remanence of 12 kG by reducing hydrogen pressure down to 0.3 atm in disproportionation step.

• 대한토목학회논문집
• /
• 제14권3호
• /
• pp.679-688
• /
• 1994

본 연구에서는 UASB 반응조의 형상변화에 따른 입상슬러지의 물리 화학적 및 형태학적인 특성이 조사되었다. 또한 반응조내의 수소분압의 크기에 따른 반응조운전의 안정성이 조사되었다. 수소분압이 높게 유지된 수정개발된 UASB 반응조의 경우가 상대적으로 수소분압이 낮게 유지된 일반적인 UASB 반응조의 경우에 비해 입상슬러지의 침전성 및 미생물보유능이 더 우수하게 나타났다. 입상슬러지의 형성과 그 안정성에 수소분압이 큰 영향을 미치는 것으로 나타났다. 입상슬러지의 화학적 조성식은 일반적인 UASB 반응조와 수정개발된 UASB 반응조가 각각 $C_7H_{12}O_{4.6}N$과 $C_5H_9O_3N$으로, 일반적인 미생물의 경험식인 $C_5H_7O_2N$과는 상이하게 나타났다. 특히 수정개발된 UASB 반응조의 경우 입상슬러지내에 질소성분이 일반적인 혐기성 미생물보다 높게 나타나, 입상슬러지의 발생기작으로서 polypeptide계 체외폴리머의 존재가능성을 보여주고 있다. 전자현미경을 이용한 형태화적 특성조사결과, 일반적인 반응조의 경우와는 달리 수소분압이 높게 유지된 수정개발된 UASB 반응조의 경우 입상슬러지의 표면에서는 Methanobrevibactor arboriphilus와 같은 크기와 형태를 한 수소이용메탄균의 성장이 다발을 이루며 관찰되었는데, 이러한 현상은 입상슬러지의 형성 메커니즘을 뒷받침해주고 있다. 우수한 입상슬러지의 형성을 위해서는 상대적인 수소분압의 크기에 따른 효과적인 상분리가 이루어져, acetogens과 수소이용메탄균들간의 공생관계가 잘 유지되도록 해주어야 할 것으로 사료된다. 수정개발된 UASB 반응조가 일반적인 UASB 반응조에 비하여 수소이용메탄균의 성장에 더욱 효과적인 환경을 제공하는 것으로 판단되며, 입상슬러지의 경영성과 반응조 전체의 유기물질 제거효율 뿐만 아니라, 운전의 안정성 측면에서도 더 우수한 것으로 사료된다.

• Nuclear Engineering and Technology
• /
• 제55권6호
• /
• pp.2069-2087
• /
• 2023

In nuclear power plant (NPP) accidents, the containment is subject to high temperatures and high internal pressures, which may further trigger serious chain accidents such as core meltdown and hydrogen explosion, resulting in a significantly higher accident level. Therefore, studying the mechanical performance of a containment under high temperature and high internal pressure is relevant to the safety of NPPs. Based on similarity principles, the 1:3.2 scale model of a prestressed concrete containment vessel (PCCV) of a NPP was designed. The loading method, which considers the thermal-pressure coupling conditions, was used. The mechanical response of the PCCV was investigated with a simultaneous increase in internal pressure and temperature, and the failure mechanism of the PCCV under thermal-pressure coupling conditions was revealed.

• 한국수소및신에너지학회논문집
• /
• 제32권6호
• /
• pp.636-641
• /
• 2021

Using numerical analysis, various factors influencing the performance development of high-pressure pumps for Dimethyl Ether (DME) engines were identified and the impact of each factor was evaluated using Taguchi method. DME fuels are more compressive than diesel fuels and have the lower heat generation, so it is necessary to increase the size of the plunger and speed (RPM) of the pump as well. In addition, it is necessary to change the shape and design of control valve to control the discharge flow and pressure. In this study, various variables affecting the performance and flow rate increase of high-pressure pumps for DME engines are planned using Taguchi method, and the best design method is proposed using correlation of the most important variables. As a result, we were able to provide the design value needed for a six-liter engine and provide optimal conditions. The best combination factors to optimize the flow rate at RPM 2,000 and diameter plunger with 20 mm. The regression equation can also be used to optimize the flow rate; -8, 13+0, 2552 RPM +54, 17 diam. Plunger.

• 한국연소학회지
• /
• 제18권1호
• /
• pp.27-33
• /
• 2013

Hydrogen-dimethy ether(DME) partially premixed compression ignition(PCCI) engine combustion was investigated in a single cylinder compression ignition engine. Hydrogen and DME were used as low carbon alternative fuels to reduce green house gases and pollutant. Hydrogen was injected at the intake manifold with an injection pressure of 0.5 MPa at fixed injection timing, $-210^{\circ}CA$ aTDC. DME was injected directly into the cylinder through the common-rail injection system at injection pressure of 30 MPa. DME inejction timing was varied to find the optimum PCCI combustion to reduce CO, HC and NOx emissions. When DME was injected early, CO and HC emissions were high while NOx emission was low. As the DME injection was retarded, the CO and HC emissions were decreased due to high combustion efficiency. NOx emissions were increased due to the high in-cylinder temperature. When DME were injected at $-30^{\circ}CA$ aTDC, reduction of HC, CO and NOx emissions was possible with high value of IMEP.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2007년도 추계학술대회 논문집
• /
• pp.188-191
• /
• 2007

This paper shows the Development of In-tank pressure regulator and Solenoid Valve used in FCV(Fuel Cell Vehicle). We have developed new type of Regulator and Solenoid through analysis of the structure and characteristics of component of FCS(Fuel Cell System) from the advanced technology. Now it is possible to localize the component by making use of the development of Regulator and Solenoid made by us. Regulator and Solenoid is a equipment to control hydrogen pressure supplied into a stack. Therefore, outlet pressure, a flow of fluid and temperature are important parameters according to a inlet pressure. And leak test, endurance test and burst test should be done to guarantee the performance and safety of Regulator and Solenoid used in the fuel of high pressure. Also, Hydrogen friendly materials are applied to inner parts of the Regulator, Solenoid and weight reduction is done to cost saving in part not related to performance. As a result, we have proven the good performance and reliability in endurance of Regulator, Solenoid and will make an development in performance as well as durability to ensure industrialization.

• 에너지공학
• /
• 제28권3호
• /
• pp.10-17
• /
• 2019

국내 친환경 수소차 보급 정책에 따라 수소차와 수소충전소 인프라 개발에 대한 관련 업계의 연구는 활발하게 진행 중이다. 반면에 수소차와 수소충전소의 내구성 및 신뢰성에 직접적인 영향을 주는 기밀용 비금속 소재(라이너, 씰, 개스킷 등)의 위험성 평가 및 재료에 관한 실증 연구는 부족한 실정이다. 이에 본 연구에서는 FMEA를 활용하여 고압 수소 설비에 사용되는 비금속 부품의 라이너와 씰에 대한 위험요소를 도출한 후 심각도, 발생빈도, 검출도 등급을 점수로 환산하여 RPN값을 산정하였다. RPN의 최대값 600, 최소값 63, 평균값이 278.5로 산출되었으며, 라이너와 씰에 대한 주기적인 관리가 중요함을 확인하였다. 더불어 비금속 고무제품에 대한 수소침지와 산소노화시험을 통해 기초 자료로 활용 가능한 물리적 실험값을 제시하고자 하였다.

• International Journal of Automotive Technology
• /
• 제2권2호
• /
• pp.39-45
• /
• 2001

Hydrogen is seen as one of the important energy vectors of the next century. Hydrogen as a renewable energy source, provides the potential for a sustainable development particularly in the transportation sector. Hydrogen driven vehicles reduce both local as well as global emissions. The laboratory of transporttechnology (University of Gent) converted a GM/Crusader V-8 engine for hydrogen use. Once the engine is optimised, it will be built in a low-floor midsize hydrogen city bus for public demonstration. For a complete control of the combustion process and to increase the resistance to backfire (explosion of the air-fuel mixture in the inlet manifold), a sequential timed multipoint injection of hydrogen and an electronic management system is chosen. The results as a function of the engine parameters (ignition timing. injection timing and duration, injection pressure) we given. Special focus is given to topics related to the use of hydrogen as a fuel: ignition characteristics (importance of electrode distance), quality of the lubricating oil (crankcase gases with high contents of hydrogen), oxygen sensors (very lean operating conditions), noise reduction (configuration and length of inlet pipes). The advantages and disadvantages of a power regulation only by the air to fuel ratio (as for diesel engines) against a throttle regulation (normal gasoline or gas regulation) are examined. Finally the goals of the development of the engine are reached: power output of 90 kW, torque of 300 Nm, extremely low emission levels and backfire-safe operation.

• Corrosion Science and Technology
• /
• 제6권3호
• /
• pp.112-119
• /
• 2007

This paper presents the importance of corrosion control and protection technology with a real case study of heater tube rupture damaged by High temperature H2S-H2 corrosion in the refinery. The heater was operated at the Hydrocracking unit and the operation temperature and pressure was $340^{\circ}C$ and $18kg/cm^{3}$ respectively. Top side of the convection tube was thinned by high temperature hydrogen sulfide and hydrogen gas as a uniform corrosion and finally ruptured under operation pressure. Damaged area (Convection tube zone) was blocked by protection wall, so it was impossible to inspect with conventional nondestructive examination. Instead the elbow area which is out of the protection wall was inspected regularly to evaluate the corrosion rate of convection tube indirectly. However the operation temperature and the phase of the process stream was different between inside the chamber and outside the chamber. As a result, it caused severe corrosion to the horizontal convection tube inside the chamber comparing to the elbow outside the chamber. Finally convection tube was corroded more rapidly than the elbow and ruptured after 13 years operation. Because of the rupture, the heater was totally burned and the operation was stopped for 3 months until it has been reconstructed. To prevent this kind of corrosion problem and accident, corrosion control should be strengthened and protection technology should be improved.