• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 추계학술대회 논문집
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• pp.89-93
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• 2002

Hydrogen - Oxygen gas has obtained from water electrolysis reaction. It is mixed gas havingconstant volume ratio 2:1 Hydrogen and Oxygen, and it is used as a source of thermal energy by combustion reaction. This gas has betterristics in the field of economy, efficiency of energy, and environmental intimacy than used both of acetylene gas and LPG for gas welding machin. So nowdays many studies of Water-Electrolyzed gas are progressed, and commercially used as a source of thermal energy for gas welding In the industry. For Water-Electrolyzed Source, it was used diode rectifier or SCR rectifier for get DC source. This method which is not looking to improve a source for impossible current control or voltage and limited control intervals. In this paper, it was relized and designed in source of pulse type for complementing existing-DC source type, also by experiment it was acquired producting characteristics of Hydrogen -Oxygen Gas through feature of source

• 전력전자학회논문지
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• 제6권5호
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• pp.377-385
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• 2001

물을 전기분해하여 얻은 일정 부피비를 갖는 수소와 산소 혼합가스를 수산화가스로 명명하며, 이를 역반응시켜서 열 에너지원으로 사용하고 있다. 수산화가스는 경제성, 안전성 및 환경친화적인 고유한 특성을 지니고 있어서 현재 가스용접기에 적용하고 있으며 여러 가지 응용분야에 적용할 수 있도록 연구 중에 있다. 본 논문에서는 수산화가스의 특성에 관하여 고찰하고 발생기용 전원에 대하여 소개하고 이 중에서 아직까지 적용되지 않은 펄스전원을 적용하여 여러 가지 운전주파수에서 비교분석 하였다.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.97-99
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• 2002

Turbulent premixed flames were a subject of many researches for a number of decades. Especially, Borghi suggested a manificent diagram classifying turbulent combustion reasions and Lipatnikov and Chomiak modified this diagram. But this diagram has difficulties tn defining a flame thickness and velocity and measuring integral length scales In addition, recently experimental techniques are being developed, so we can accurately use PIV diagnostics measuring 2D velocity field instead of LDV and make good use of PLIF techniques for obtaining the flame information. In this study, according to developing techniques, suggest a new diagram replacing the existing Borghi diagram. Simultaneous PIV/OH PLIF measurements are used, which measure a shear strain rate and a location of flames, respectively. The shear strain rate represents turbulence and the OH signal indicates the flame information, but there is no geometric Information which is very important to flame quenching. Hence, to consider the geometric information, calculate fractal dimensions of the OH images. So the diagram suggested in this research has three axes which consist of strain rate, OH signal, and fractal dimension and can classify turbulent premixed flames.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2866-2877
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• 2021

The complex coupling relationship between liquid sodium and concrete materials affects both the sodium fire characteristics and concrete properties through heat and chemical erosion. In this study, experiments on direct and indirect (separated by a steel plate) contact of the columnar sodium fire with the concrete surface were performed. It was found that the combustion efficiency of liquid sodium in direct contact with concrete was significantly enhanced and accompanied by intermittent explosions and splashing of small concrete fragments. The sodium fire on the surface of the concrete considerably increased the internal temperature, pore size, and distribution density of the concrete. In addition, the depth of influence on the loosening of the concrete structure was also greatly extended. The contact of liquid sodium with the concrete substantially affected its permeability resistance. The water absorption of the concrete surface was increased by more than 70% when liquid sodium directly impacted the bare concrete surface. However, the change in water absorption in the centre of the concrete was primarily affected by the duration of the external heat.

• Advances in materials Research
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• 제8권1호
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• pp.11-24
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• 2019

This paper presents a review study for energy-efficient gas turbines (GTs) with cycles which contributes significantly towards sustainable usage. Nonetheless, these progressive engines, operative at turbine inlet temperatures as high as $1600^{\circ}C$, require the employment of highly creep resistant materials for use in hotter section components of gas turbines like combustion chamber and blades. However, the gas turbine obtain its driving power by utilizing the energy of treated gases and air which is at piercing temperature and pushing by expanding through the several rings of steady and vibratory blades. Since the turbine blades works at very high temperature and pressure, high stress concentration are observed on the blades. With the increasing demand of service, to provide adequate efficiency and power within the optimized level, turbine blades are to be made of those materials which can withstand high thermal and working load condition for longer cycle time. This paper depicts the recent developments in the field of implementing the best suited materials for the GTs, selection of proper Thermal Barrier Coating (TBC), fracture analysis and experiments on failed or used turbine blades and several other designing and operating factors which are effecting the blade life and efficiency. It is revealed that Nickel based Superalloys were promising, Cast Iron with Zirconium and Pt-Al coatings are used as best TBC material, material defects are the foremost and prominent reason for blade failure.

• Corrosion Science and Technology
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• 제21권6호
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• pp.476-486
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• 2022

Recently, aluminum 6061 instead of copper alloy is used for cooling heat exchangers used in the internal combustion of engines due to its economic feasibility, lightweight, and excellent thermal conductivity. In this study, aluminum 6061 alloy was anodized with oxalic acid, phosphoric acid, or chromic acid as an anodizing electrolyte at the same concentration of 0.3 M. After the third anodization, FDTS, a material with low surface energy, was coated to compare hydrophobic properties and anti-icing characteristics. Aluminum was converted into an anodization film after anodization on the surface, which was confirmed through Energy Dispersive X-ray Spectroscopy (EDS). Pore distance, interpore distance, anodization film thickness, and solid fraction were measured with a Field Emission Scanning Electron Microscope (FESEM). For anti-icing, hydrophobic surfaces were anodized with oxalic acid, phosphoric acid, or chromic acid solution. The sample anodized in oxalic acid had the lowest solid fraction. It had the highest contact angle for water droplets and the lowest contact hysteresis angle. The anti-icing contact angle showed a tendency to decrease for specimens in all solutions.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.91-93
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• 2003

A comprehensive numerical study is carried out to investigate for the understanding of the flow evolution and flame development in a supersonic combustor with normal injection of ncumally injecting hydrogen in airsupersonic flows. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration for a multi-component chemically reacting system. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations and detailed chemistry of H2-Air is considered. It also accommodates a finite-rate chemical kinetics mechanism of hydrogen-air combustion GRI-Mech. 2.11[1], which consists of nine species and twenty-five reaction steps. Turbulence closure is achieved by means of a k-two-equation model (2). The governing equations are spatially discretized using a finite-volume approach, and temporally integrated by means of a second-order accurate implicit scheme (3-5).The supersonic combustor consists of a flat channel of 10 cm height and a fuel-injection slit of 0.1 cm width located at 10 cm downstream of the inlet. A cavity of 5 cm height and 20 cm width is installed at 15 cm downstream of the injection slit. A total of 936160 grids are used for the main-combustor flow passage, and 159161 grids for the cavity. The grids are clustered in the flow direction near the fuel injector and cavity, as well as in the vertical direction near the bottom wall. The no-slip and adiabatic conditions are assumed throughout the entire wall boundary. As a specific example, the inflow Mach number is assumed to be 3, and the temperature and pressure are 600 K and 0.1 MPa, respectively. Gaseous hydrogen at a temperature of 151.5 K is injected normal to the wall from a choked injector.A series of calculations were carried out by varying the fuel injection pressure from 0.5 to 1.5MPa. This amounts to changing the fuel mass flow rate or the overall equivalence ratio for different operating regimes. Figure 1 shows the instantaneous temperature fields in the supersonic combustor at four different conditions. The dark blue region represents the hot burned gases. At the fuel injection pressure of 0.5 MPa, the flame is stably anchored, but the flow field exhibits a high-amplitude oscillation. At the fuel injection pressure of 1.0 MPa, the Mach reflection occurs ahead of the injector. The interaction between the incoming air and the injection flow becomes much more complex, and the fuel/air mixing is strongly enhanced. The Mach reflection oscillates and results in a strong fluctuation in the combustor wall pressure. At the fuel injection pressure of 1.5MPa, the flow inside the combustor becomes nearly choked and the Mach reflection is displaced forward. The leading shock wave moves slowly toward the inlet, and eventually causes the combustor-upstart due to the thermal choking. The cavity appears to play a secondary role in driving the flow unsteadiness, in spite of its influence on the fuel/air mixing and flame evolution. Further investigation is necessary on this issue. The present study features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous works. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is not related to the cavity, but rather to the intrinsic unsteadiness in the flowfield, as also shown experimentally by Ben-Yakar et al. [6], The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The work appears to be the first of its kind in the numerical study of combustion oscillations in a supersonic combustor, although a similar phenomenon was previously reported experimentally. A more comprehensive discussion will be given in the final paper presented at the colloquium.

• 대한기계학회논문집B
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• 제35권3호
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• pp.321-330
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• 2011

본 연구는 전선화염의 전파특성에 직류전기장이 미치는 영향에 대한 실험적 연구이다. 화염전파는 은 0에서 ${\pm}7kV$ 범위의 음극과 양극의 전기장을 인가하여 실험되어졌다. 본 연구를 통해 앞선 전선화염 전파에 영향을 미치는 교류전기장 효과에 관한 연구결과와 비교하여 관찰된 다양한 화염 모양 변화의 원인을 알아보고, 화염 전파 속도의 가속특성에 대해서도 논의하고자 한다. 직류전기장의 인가가 전선화염에 미치는 영향은 크지 않지만 이온풍 효과에 따른 미미한 영향은 존재하며, 이것은 온도 균형 메커니즘과 연료 증발기체 분사 효과로 설명 될 수 있다.

• 한국토양환경학회지
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• 제2권1호
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• pp.109-117
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• 1997

60년대 이후 우리나라에 새로운 주거양식으로 정착된 아파트내 설비의 일부였던 쓰레기 투입구(Dust Chute)는 여러 사회적인 논의를 거쳐 폐쇄되었고, 이제는 신도시에서 조차도 찾아볼 수 없는 낡은 유물이 되고 말았다. 현재는 주택 옥외공간에 별도의 집하장소를 만들어 수거해가는 방식으로 대응하고 있는데, 그럴수밖에 없었던 주된 이유는 분리수거가 제대로 이뤄지지 않은데 기인한 것으로 분석된다. 95년초부터 전국적으로 실시된 쓰레기종량제는 우리나라의 쓰레기 처리 분야에 있어 생활쓰레기의 분리수거 및 재활용을 가능케하는 제도로 자리잡고 있다. 인간들은 또 그린라운드 시대에 걸맞는 주거환경의 질을 추구하고 있다. 이러한 사회적 변화에 대응한 여러 노력이 쓰레기 수거운반 분야에서도 이뤄질 수 있다고 본다. 이미 택지개발 등으로 새로 조성되는 주거단지에는 지역난방시스템과 쓰레기소각장, 공동구 등이 도입 활용되고 있으며, 바로 이들 시설과도 밀접한 연관성이 있는 각국의 쓰레기 수거운반 방식을 비교하고, 선진 각국의 신도시와 주요 대형시설에 도입 활용되고 있는 방식인 관로내 공기를 이용한 쓰레기 수거운반 시스템(Pneumatic Waste Collection System)의 적용사례 및 그의 실용성에 대하여 연구하기로 한다.

• 한국광물학회지
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• 제22권2호
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• pp.153-162
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• 2009

석간주는 적색과 적갈색 등 붉은 빛을 띠는 전통 광물성 안료로 주성분은 산화철이다. 석간주의 광물학적 특성과 기능성을 연구하기 위해서, 문헌에 옛 산지로 나와있는 울릉도 주토굴에서 석간주를 채취하였다. 울릉도주토굴의 석간주광석은 감람석현무암과 각섬석조면암 경계면에서 단속적으로 산출하며, 적갈색 또는 황갈색을 띠고 대체로 점토질이며 부분적으로 암편을 함유하고 있다. 석간주광석 중 적색은 적철석에 의한 것이며, 황갈색은 훼리하이드라이트에 의한 것이다. 울릉도석간주광석의 색상을 결정하는 산화철광물들은 고토양중에서 함철 수용액으로부터 훼리하이드라이트라는 광물로 침전되었으나 부분적으로 적철석으로 전이되었다. 석간주광석을 전통방식에 의해 안료로 제작하여 목재에 재현한 색상은 전통 건축물에서 측정한 붉은색 색상과 유사하였다. 울릉도석간주안료의 내습기능과 방염기능은 화학석간주안료에 비해 월등히 우수한 것으로 확인되었으며 연소시험에서 화학석간주안료는 발화와 연소를 촉진시키는 결과를 보였다. 울릉도석간주안료가 함유된 배지에서 목재부후균의 성장이 저지되는 경향을 보여 울릉도석간주는 방부성을 지닌 채색안료로 판단된다.