• Title/Summary/Keyword: Water atomization

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Characteristics of Ti-Ni-(XCu) Shape Memory Alloy Powders made by Gas Atomization Process (가스 분무법으로 제조한 Ti-Ni-XCu 형상기억합금분말의 특성)

  • 징동훈
    • Journal of Powder Materials
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    • v.6 no.2
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    • pp.171-177
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    • 1999
  • Ti-45.2at.%Ni-5at.%Cu and Ti-40.2at.%Ni-10atat.%Cu alloy powders were fabricated by gas atomization process. The microstructures, Shape, hardness and phase transformation behaviors of the powders were investigated by means of optical microscopy, scanning electron microscopy, micro-hardness measurement, x-ray diffraction analyses and differential scanning calorimetry. The hardness of the Ti-Ni-XCu alloy powders decreased as Cu-content increased. The x-ray diffraction analyses were carried out for powders without heat treatment, and those that treated at 85$0^{\circ}C$ for an hour in a vaccum state($10^5$ torr) and then quenched into ice water. The intensity of B$19^t$ phase increased with heat treating. The monoclinic B$19^t$ martensite was formed in the Ti-Ni-XCu alloy powders during cooling.

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An Experimental Study on the Combustion Characteristics of CWM Single Droplet (CWM 단일액적의 연소특성에 관한 연구)

  • Park, Chong-Sang;Lee, Tae-Won;HA, Jong-Yul;Chung, Sung-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.3
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    • pp.402-410
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    • 2000
  • As the combustion process of CWM consists of the water evaporation, the release and combustion of volatile matter, and the combustion of char for every particle, it is more complex than that of existent liquid fuel. Though the many studies on CWM combustion have been carried out by the single droplet using hanging methods or the multiple droplet using atomization methods, any report don't presents definite solution about the effects by the initial water evaporation and combustion of volatile. When CWM is suddenly exposed in the high temperature surroundings, the internal water evaporates and then each droplet builds up pores. Besides, porosity rate changes along the temperature of surroundings, the composition ratio of CWM, and the initial diameter of droplet. In result, because it affects the whole combustion rate, the combustion of CWM has complex mechanism as compared with the combustion of liquid or gas fuel. Therefore, concentrating on porous structure of CWM, this study has proceeded to acquire the basic data on the CWM injection combustion and closely examines the effects of the first stage combustion on the whole combustion by measuring the diameter variations, pore rate, mass fraction burned, and the internal temperature changes of CWM droplet. The results demonstrate that $60{\sim}70%$ of initial mass is reduced during water evaporation and volatile combustion period, and swelling rate, mass faction burned, and density variation are greatly concerned with atomization of CWM etc.

Combustion Characteristics of Gasoline Direct Injection Engine with Water Injection into Intake Port under Low Engine-Load Operating Condition (낮은 엔진 부하의 운전조건에서 흡기포트 내 물 분사에 따른 가솔린 직접분사 엔진의 연소 특성)

  • Jeun, Haegwang;Lee, Kyung-Hwan;Choi, Myungsik;Park, Suhan
    • Journal of ILASS-Korea
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    • v.23 no.2
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    • pp.96-101
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    • 2018
  • The purpose of this study is to investigate the effect of water injection on combustion characteristics of gasoline direct injection (GDI) engine with turbo-charger under low-load operating condition. The test engine used in this study has four-cylinder and 10.2 of compression ratio. In order to study the effect of water injection ratio on combustion characteristics, the water was injected into the intake port from 10% to 50%, based on fuel injection quantity. From the experiment, it revealed that the water injection induced the improvement of fuel economy because of the advance of spark-timing by the reduction of in-cylinder temperature. In addition, the water injection caused the prolong of extension of the ignition delay and slight increase of burn duration.

Experimental Study on Water Absorption and Drying Characteristics of Various Fabrics using IR Camera (열화상카메라를 이용한 직물의 물 흡수 및 건조 특성에 대한 실험 연구)

  • Jeongbae Kim
    • Journal of ILASS-Korea
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    • v.28 no.1
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    • pp.10-15
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    • 2023
  • Recently, various types of towels and dishcloth dryer products are being widely distributed in Korea. Evaluation methods for water absorption properties of various fabrics have been developed, and there are many studies using them. This study newly intended that whether it is possible to obtain data that can quantitatively analyze the water absorption characteristics of various fabrics, to show the correlation between the water absorption height and the amount of water (water holdup) absorbed, and to experimentally suggest the applicability to evaluate the drying capacity of towel dryer using IR camera. Through these experiments, it was confirmed that quantitative data on the water absorption height of various fabrics can be measured using an IR camera and can be clearly applied to the performance evaluation of actual products.

Numerical Study on the Change in Fire Characteristic as Operating Water-mist in Under-ventilated Compartments (워터미스트 작동에 의한 산소저공급 실내화재 특성 변화에 대한 수치해석 연구)

  • Ko, G.H.;Lee, S.H.;Ryou, H.S.
    • Journal of ILASS-Korea
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    • v.13 no.3
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    • pp.156-161
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    • 2008
  • The present article reports a numerical study on the fire characteristic change by water-mist in under-ventilated compartments. The natural gas and heptane pool fires are used as fire sources, which are located in the bottom center of the 2/5 reduced-scaled model of the ISO 9705 standard room. The fire modeling using the FDS (Fire Dynamics Simulator) is validated by comparison with previously published experimental results. For temperature and combustion gas concentrations at two positions located in the upper layer of compartment, the predicted results with and without water-mist are compared each other. The results show that under the water-mist operation, the predicted temperature and carbon monoxide concentration reduce as $300{\sim}400^{\circ}C$ and about 20%, respectively, compared to those without water-mist.

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A Study on the Behavior of Nano-fluid Droplet Impacting Upon a Hot Surface (고온벽과 충돌하는 나노유체 액적 거동에 관한 연구)

  • Kim, E.DD.;Park, I.H.;Bae, N.H.;Kang, B.S.
    • Journal of ILASS-Korea
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    • v.20 no.1
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    • pp.7-13
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    • 2015
  • In this study, the behavior of water or nanofluid droplets impacting upon a hot surface was investigated by visualization of impacting phenomena with time-delayed photographic technique. Changing the mass ratio of nanofluid and the temperature of the heated surface, the characteristics of the spreading behavior and the diameter of spreading liquid film was compared between water and nanofluid droplets. The impacting droplet spreaded as a liquid film after impact and nanofluid droplets spreaded more widely than water droplets. After reaching the maximum diameter, water droplets shrinked more than nanofluid droplets. Based on this, the heat transfer area from a hot surface to impacting nanofluid droplets would be wider than that of impacting water droplets. Considering individual impacting droplet only, spray cooling using nanofluid would be better than using water.

Effects of Water Vapor Concentration on a Droplet Evaporation (액적의 증발에 미치는 수증기 농도의 영향)

  • Kim, Y.W.;Lee, M.J.;Ha, J.Y.;Chung, S.S.
    • Journal of ILASS-Korea
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    • v.4 no.1
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    • pp.27-33
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    • 1999
  • An experimental study has been conducted to clarify the effect of vapor on droplet evaporation. Droplets of water, ethanol, n-hexadecane and n-heptane were exposed in air stream. Temperature, pressure, and flow velocity in the ambient air are 470K, 1 atm, and 2m/s, respectively. Measurements are carried out for the wide range of water vapor concentration$(0%\sim40%)$. To obtain the time histories of droplet diameter, suspended droplet in hot and humid air stream was synchronized with a back flash light, and enlarged droplet images were taken on a CCD camera. With the vapor concentration increasing, the evaporation rate constant of water droplet decrease slightly and the droplet of ethanol and n-heptane increase actively. The evaporation rate constant of n-hexadecane which has higher boiling point than water increases within around 30% of the concentration.

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Mixing Characteristics of Static Mixers for Emulsion Oil (이멀션유 정적믹서의 혼합특성 연구)

  • 김기성;박상규
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2000.11a
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    • pp.91-98
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    • 2000
  • The fuels of water-in-oil emulsion have a potential of reducing PM(Particulate Matter) and NOx emissions, and increassing combustion efficiency in the furnaces and the burners. For making the most of the beneficial of the secondary atomization due to the microexplosion, the water droplets distributed in the oil must have the optimal sizes. The purpose of this paper is to investigate the water droplet size distribution characteristics of the different types of the static mixers. For analysing the size distribution characteristics efficiently, image analysis system was constructed and an appropriate image processing algorithm was developed. Two kinds of static mixers: Kenics type and RF type, were tested. As a results, RF type static mixer shows a better characteristics in the mean drop sizes, particularly in the condition of high water content.

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Development of Radial Fin Static Mixers for Emulsion Oil (이멀션유용 방사상 핀 정적믹서 개발)

  • 김기성;박상규
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.4
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    • pp.904-911
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    • 2001
  • The fuels of water-in-oil emulsion have a potential of reducing PM(Particulate Matter) and NOx emissions, and increasing combustion efficiency in the furnaces and the burners. For making the most of the beneficial of the secondary atomization due to the microexplosion, the water droplets distributed in the oil must have the optimal sizes. The purpose of this paper is to investigate the water droplet size distribution characteristics of the different types of the static mixers. For analysis the size distribution characteristics efficiently, image analysis system wes constructed and an appropriate image processing algorithm was developed. Two kinds of static mixers: Kenics type and RF type, were tested. As a results, RF type static mixer shows a better characteristics in the mean drop size, particularly in the condition of high water content.

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Comparison of the Characteristics of Sprays between Water and Nanofluid Sprays (물과 나노유체의 분무 특성 비교)

  • Kang, B.S.;Lee, S.P.
    • Journal of ILASS-Korea
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    • v.19 no.2
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    • pp.82-87
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    • 2014
  • Nanofluids are that metallic or nonmetallic nanometer-sized particles are dispersed in liquid. They can be used in various fields to increase the heat transfer rate because the thermal conductivity of nanofluids can be increased significantly. Nanofluids may be used as a good alternative of coolants in spray cooling. This study conducted experiments to compare the characteristics of sprays between water and nanofluid sprays. The radial distributions of droplet velocities and diameters of water, 0.2% wt.(weight), and 0.5% wt. $Al_2O_3$ nanofluids at the pressure of 0.2 and 0.3 MPa were measured by laser doppler instruments. The radial distributions of droplet diameters and velocities at two axial positions with water and 0.2% wt. nanofluid sprays didn't show much difference. A big difference, however, was observed between 0.5% wt. nanofluid and water sprays. With the increase of the mass of nano-particles, the average droplet diameters were increased and the average droplet velocities were decreased.