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A Steam-Plasma Igniter for Aluminum Powder Combustion

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Plasma Science and Technology 2015年第5期17卷 392-401页

作者： Sanghyup lee Kwanyoung NOH Jihwan LIM Woongsup yoon Mechanical Engineering Department of Yonsei University

High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions. A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests. The steam plasma rapidly stabilizes in both plasma and steam jet modes. Parametric investigation of the steam plasma jet is conducted in terms of arc strength. A high-speed camera and an oscilloscope method visualize the discharge characteristics, and optical emission spectroscopy measures the thermochemical properties of the plasma jet. The diatomic molecule OH fitting method, the Boltzmann plot method, and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature, excitation temperature, and OH radical distribution, respectively. The excitation temperature at the nozzle tip is near 5500 K, and the gas temperature is 5400 K.

关键词： steam plasma igniter aluminum emission spectroscopy energetic metal fuels powder ignition and combustion optical

Thermo-physical Characteristics of Nickel-coated Aluminum Powder as a Function of Particle Size and Oxidant

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Chinese Journal of Mechanical Engineering 2016年第6期29卷 1244-1255页

作者： lee Sanghyup NOH Kwanyoung LIM Jihwan yoon Woongsup Advanced Energy and Propulsion Laboratory Department of Mechanical Engineering Yonsei University Missile System Integration / propulsion Center Hanwha Corp.

Aluminum particles 15-25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size（15-25 μm, 74-105 μm, and 2.38 mm） and oxidizer（air, CO2, and argon）, the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry （TGA/DSC） enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.

关键词： nickel-coated aluminum TGA/DSC aluminum ignition combustion intermetallic reaction

A Study on Energy Saving Rate for Variable Speed Condition of Multistage Centrifugal Pump

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Journal of Thermal Science 2015年第6期24卷 566-573页

作者： Sang-Ho Suh Rakibuzzaman Kyung-Wuk Kim Hyoung-Ho Kim In sik yoon Min-Tae Cho Department of Mechanical Engineering Soongsil University Dooch Co. 295 Sagok-ri Jangan- Myeon Hwaseong-si Gyeonggi-do 445-942 South Korea

Centrifugal pumps are being widely used in many industrial and commercial *** of these pumps are being operated at constant speed but could provide energy savings through adjustable speed *** purpose of this study was to get the energy saving rates of the multistage centrifugal pump with variable speed *** this investigation an experimental set up of variable flow and pressure system was made to get energy saving rates and numerical analyses are applied to validate the pump *** energy saving and therefore the cost saving depends on the specific duty cycle of which the machine *** cycle is the proportion of time during which a component,device and system is *** duty cycle segmented into different flow rates and weighting the average value for each segment by the interval *** system was operated at 50%or less of the pump *** input power of the system was carried out by pump characteristics curve of each operating *** energy consumption was done by the product of specific duty cycle and the input power of the system for constant speed and variable speed drive *** total energy consumed for constant speed drive pump was 75,770 k *** and for variable speed drive pump was 31,700 k *** total energy saving of the system was 44,070 k *** or 58.16%***,this paper suggests a method of implementing an energy saving on variable-flow and pressure system of the multistage centrifugal pump.

关键词： Multistage Centrifugal Pump Performance Analysis Energy saving rate SST Model Duty Cycle

Analysis of the Sloshing Flows of a LNG Cargo Tank

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Journal of Thermal Science 2011年第5期20卷 442-448页

作者： Deog Hee Doh Hyo Je Jo Byeong Rog Shin Min Cheol Ryu yoon sik Hwang Division of Mechanical and Information Eng. Korea Maritime University Division of Naval Architecture and Ocean Systems Eng. Korea Maritime University Department of Mechanical Engineering Changwon National University Fluid Dynamics R&D Team DSMEGeoje-siKorea

The sloshing flows in a LNG cargo tank model （1/50 scale） of a ship are measured by an embedded pano- ramicPIV system. The measurement system consists of a Nd-Yag laser（120mJ, 15Hz）, two cameras（lk x lk） and a host computer. Four experimental cases were tested for the tank model, in which swaying motions are made by a 6 DOF-motion platform. The amplitudes of swaying are 9.76mm and 29.29mm, and the swaying frequencies are 0.633Hz and 0.828Hz. The measurement regions are the vertical plane 50ram away from the front wall of the tank where a pump tower is installed. It was verified that the flow patterns of the sloshing are similar to each other when the swaying amplitudes are similar.

关键词： Sloshing Model Ship Cargo Tank Embedded Panoramic PIV Swaying Motion

Effect of polyethylene glycol on electrochemically deposited trivalent chromium layers

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中国有色金属学会会刊：英文版 2009年第4期19卷 819-823页

作者： Joo-Yul lee Man KI M sik-Chol KWON Department of Surface Technology Korea Institute of Materials Science

The structural characteristics of the trivalent chromium deposits and their interfacial behavior in the plating solution with and without polyethylene glycol molecules were observed by using various electrochemical methods such as cyclic voltammetry,open circuit potential transition,electrochemical impedance spectroscopy,scanning electron microscopy and X-ray photoelectron *** is shown that the polyethylene glycol molecules make the reductive current density lower in the trivalent chromium plating system and promote a hydrogen evolution reaction through their adsorption on the electrode *** the trivalent chromium layer formed from the polyethylene glycol-containing solution has somewhat higher density of cracks on its surface and results in a lower film resistance,lower polarization resistance,and higher capacitance in a corrosive *** is also revealed that the formation of chromium carbide layer is facilitated in the presence of polyethylene glycol,which means easier electrochemical codeposition of chromium and carbon,not single chromium deposition.

关键词：聚乙二醇电沉积层三价铬扫描电子显微镜电化学阻抗谱电极表面电化学方法乙二醇溶液

Isothermal-crystallization Kinetics and Spherulite Growth of Aliphatic Polyketone/Polyamide-6 Blends

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Chinese Journal of Polymer Science 2017年第6期35卷 782-792页

作者： He-xin Zhang Seong-Rok Huh Eun-Bin Ko Byung-sik Park Keun-Byoung yoon Department of Polymer Science and Engineering Kyungpook National UniversityKorea Key Laboratory of Synthetic Rubber Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Department of Pharmaceutical Engineering International University of KoreaJinjuKorea

In this research, the morphologies, isothermal-crystallization kinetics, and spherulite growth of aliphatic polyketone/polyamide-6 blends were studied. A single glass-transition temperature （Tg） was determined, and the composition dependence of Tg for these blends was well described by the Kwei equation. The strong intermolecular interaction between the two polymer components was confirmed by melting-point depression. The isothermal-crystallization kinetics were analyzed on the basis of the Avrami approach. A linear increase in the radii of the spherulites with time was observed for all compositions. All the spherulites continued to grow at nearly identical growth rates. With increasing polyamide-6 content, the size of the spherulites in the polyketone/polyamide-6 blends gradually decreased, and the number of spherulites in the blends increased.

关键词： Polyketone Polyamide-6 Crystallization kinetics Spherulite growth

Effect of post heat-treatment on the microstructure and high-temperature oxidation behavior of precipitation hardened IN738LC superalloy fabricated by selective laser melting

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Journal of Materials Science & Technology 2021年第17期76卷 95-103页

作者： Kyu-sik Kim Sangsun Yang Myeong-Se Kim Kee-Ahn lee Department of Materials Science and Engineering Inha UniversityIncheon 22212Republic of Korea Korea Institute of Materials Science Changwon51508Republic of Korea Auratech Co. Ltd.Seongnam13449Republic of Korea

The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation *** as-built microstructure showed fine cell and columnar structure due to high cooling *** element segregation was observed in inter-cell/inter-columnar *** post heat-treatment,the initially-observed cell structure disappeared,instead bimodal Ni_3(Al,Ti)particles *** temperature(1273 K and 1373 K)oxidation test results showed parabolic oxidation curves regardless of temperature and initial *** as-built IN738LC fabricated via the selective laser melting process displayed oxidation resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast ***-treated SLM IN738LC,although had similar oxidation weight-gain values to those of the SLM asbuilt material at 1273K,showed relatively better oxidation resistance at 1373 *** Ni_3(Al,Ti)precipitate formed in the post heat treatment changed the local chemical composition,thereby led to changes in alumina former/chromia former location and fraction on the alloy *** was concluded that in heat-treated IN738LC increased alumina former fraction was found,and this resulted in excellent oxidation resistance and relatively low weight-gain.

关键词： IN738LC Selective laser melting High temperature oxidation Post heat-treatment Oxidation mechanism

Soil compression influences the avoidance behavior of Allonychiurus kimi(Collembola)to cadmium and copper

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Pedosphere 2022年第3期32卷 487-494页

作者： Jino SON Yun-sik lee Yongeun KIM Kijong CHO OJeong Eco-Resilience Institute Korea UniversitySeoul 02841(Republic of Korea) Department of Environmental Science and Ecological Engineering Korea UniversitySeoul 02841(Republic of Korea) Institute of Environment and Ecology Korea UniversitySeoul 02841(Republic of Korea)

The behavior of soil organisms inhabiting soil pore spaces can be influenced by soil compression,which can affect their avoidance behavior to *** this study,we aimed to evaluate the effect of soil compression on the avoidance behavior of Allonychiurus kimi(Collembola)to heavy metals cadmium and ***,to assess the applicability of the avoidance test guideline of the International Organization for Standardization(ISO)developed for Folsomia candida,we investigated the avoidance behavior of *** to cadmium and copper in an artificial soil with a loose structure(bulk density of 0.25 g cm^(-3)),the porous texture of which was sufficiently loose to enable *** to move between pore *** effect of soil compression on the avoidance behavior of *** to both metals was evaluated in compressed soil(bulk density of 0.64 g cm^(-3))with a uniformly compressed soil surface,and avoidance behavior was investigated at 24-h intervals over a 120-h *** that *** is unable to burrow into compressed soil,the compressed soil test can minimize the effects of differences in soil factors,such as soil porosity and bulk density,on the behavior of this *** the artificial soil,a statistically significant avoidance behavior of *** was observed at cadmium and copper concentrations greater than 50 and 200 mg kg^(-1),respectively,thereby indicating the applicability of the ISO avoidance test guidelines for *** compared at the same exposure time point,the avoidance response to both metals in compressed soil was less sensitive than that in uncompressed *** addition,we observed differences in the effects of metals on avoidance response in the compressed soil over time,with the effect of cadmium increasing with time and the effect of copper showing the opposite ***,we found that soil compression can affect the avoidance behavior of *** to cadmium and copper,and we discussed the advantages and limitations of using compressed

关键词： behavioral endpoint ecotoxicity test habitat function heavy metal pollutant springtail

Self-motivated,thermally oxidized hematite nanoflake photoanodes:Effects of pre-polishing and ZrO_(2) passivation layer

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Journal of Energy Chemistry 2022年第2期31卷 415-423页

作者： Love Kumar Dhandole Hyun Hwi lee Weon-sik Chae Jum Suk Jang Jae Sung lee Department of Energy Engineering School of Energy and Chemical EngineeringUlsan National Institute of Science and Technology(UNIST)Ulsan 44919Republic of Korea Division of Biotechnology College of Environmental and Bioresource SciencesChonbuk National UniversityIksan 54596Republic of Korea Pohang Accelerator Laboratory Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Daegu Center Korea Basic Science InstituteDaegu 41566Republic of Korea

High-temperature thermal oxidation of an Fe foil produces a high-quality,crystalline hematite nanoflake suitable as a photoanode for the photoelectrochemical(PEC)water *** pre-polishing of the foil surface has a profound effect in the formation of a vertically-aligned nanoflakes of hematite phase with extended(110)planes by removing the loosely-bonded oxide *** the surface of the photoanode is modified with a ZrO_(2) passivation layer and a cobalt phosphate co-catalyst,the charge recombination at the photoanode-electrolyte interface is greatly suppressed to improve its overall PEC *** a result,the photocurrent density at 1.10 VRHE under 1 sun condition is enhanced from 0.22 mA cm^(-2) for an unmodified photoanode to 0.59 mA cm^(-2) for the fully modified photoanode,and the photocurrent onset potential is shifted cathodically by 400 ***,the photoanode demonstrates outstanding stability by showing steady production of H_(2) and O_(2) gases in the stoichiometric ratio of 2:1 in a continuous PEC operation for 10 h.

关键词： Fe foil Thermal oxidation Nanoflakes Photoelectrochemical water splitting Surface modifications