• Title/Summary/Keyword: High-pressure experiment

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Coal particle distribution inside fuel droplets of high loading CWM (고부하도 CWM 연료방울안에 존재하는 미분탄 분포)

  • 김성준;유영길
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.2
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    • pp.618-629
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    • 1991
  • The purpose of this experiment is to understand the distribution of coal particles inside CWM droplet which is believed to be a very important factor controlling the flame stability. CWM slurry is atomized by an air assisted twin fluid nozzle. An experimental rig is designed and fabricated. The mean size of coal particle distribution in CWM slurry, atomizing air pressure, coal particle loading in slurry and sampling position inside spray are main experimental variables. The atomized CWM droplets are sampled on the thin white layer of magnesium oxide by the emergency sampling shutter. The sampled coal particles on magnesium oxide layers are collected into test tubes and dispersed completely by Ultra-Sonicator. The size distribution of coal particles inside droplets are measured by Coulter Counter. The presence of coal particle inside the impressions of droplets on magnesium oxide layer are investigated by photo technique. There are quite many droplets which do not have any coal particles. Those are just water droplets, not CWM droplets. The population ratio of droplets without coal particles to toal number of droplets is strongly affected by the mean size of coal particle distribution in slurry and this ration becomes bigger number as the mean size of coal particles be larger. The size distribution of coal particles inside CWM droplets is not even and depends on the size of droplet. Experimental results show that the larger CWM droplets has droplets has bigger mean value of particle size distribution. This trend becomes more evident as the atomizing air pressure is raised and the mean size of coal particles in CWM slurry is bigger. That is, the distribution of coal particles inside CWM dropolets is very much affected by the atomizing air pressure and the mean size of pulverized coal particles in CWM slurry.

A Phase Transformation Study on Amorphous Diopside ($CaMgSi_2O_6$) (비정질 투휘석($CaMgSi_2O_6$)에 대한 상변이 연구)

  • 김영호
    • Journal of the Mineralogical Society of Korea
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    • v.16 no.2
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    • pp.161-169
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    • 2003
  • A phase transformation study on a synthetic amorphous diopside, $(Ca,Mg)SiO_3$has been carried out up to ∼30 GPa, and ∼$1000^{\circ}C$ using a diamond anvil cell and YAG laser heating system, respectively. A starting amorphous material shows a direct transition to cubic $(Ca,Mg)SiO_3$perovskite at high pressure, which contradicts to the crystalline diopside phase transformation sequence disproportionating into mixtures of the orthorhombic$ MgSiO_3$perovskite and the cubic $CaSiO_3$perovskite phases. This discrepancy might be due to the different starting materials as well as the temperature variations at each specific experiment performed. The present phase transfor mation sequence would modify the mineralogical assemblage in the Earth transition region and the lower mantle depending upon the pressure, temperature and the oxygen partial pressure.

Bending ratcheting behavior of pressurized straight Z2CND18.12N stainless steel pipe

  • Wang, Lei;Chen, Gang;Zhu, Jianbei;Sun, Xiuhu;Mei, Yunhui;Ling, Xiang;Chen, Xu
    • Structural Engineering and Mechanics
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    • v.52 no.6
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    • pp.1135-1156
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    • 2014
  • The ratcheting effect greatly challenges the design of piping components. With the assistance of the quasi-three point bending apparatus, ratcheting and the ratcheting boundary of pressurized straight Z2CND18.12N stainless steel pipe under bending loading and vertical displacement control were studied experimentally. The characteristics of progressive inelastic deformation in axial and hoop directions of the Z2CND18.12N stainless steel pipes were investigated. The experiment results show that the ratcheting strain occurs mainly in the hoop direction while there is less ratcheting strain in the axial direction. The characteristics of the bending ratcheting behavior of the pressure pipes were derived and compared under load control and displacement control, respectively. The results show that the cyclic bending loading and the internal pressure affect the ratcheting behavior of the pressurized straight pipe significantly under load control. In the meantime, the ratcheting characteristics are also highly associated with the cyclic displacement and the internal pressure under displacement control. All these factors affect not only the saturation of the ratcheting strain but the ratcheting strain rate. A series of multi-step bending ratcheting experiments were conducted under both control modes. It was found that the hardening effect of Z2CND18.12N stainless steel pipe under previous cyclic loadings no matter with high or low displacement amplitudes is significant, and the prior loading histories greatly retard the ratcheting strain and its rate under subsequent loadings. Finally, the ratcheting boundaries of the pressurized straight Z2CND18.12N stainless steel pipe were determined and compared based on KTA/ASME, RCC-MR and the experimental results.

A Study on the High Repetition Rate Pulsed $CO_2$ Laser Using IGBT (IGBT를 이용한 고반복 펄스형 $CO_2$ 레이저 개발에 관한 연구)

  • Chung, H.J.;Kim, D.W.;Lee, D.H.;Yoon, S.H.;Lee, Y.S.;Kim, H.J.;Cho, J.S.
    • Proceedings of the KIEE Conference
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    • 1999.11d
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    • pp.1072-1074
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    • 1999
  • In this study, it is the purpose to develope a cheap and compact pulsed $CO_2$ laser with pulse repetition rate range of 1 kHz. We used a IGBT switched power supply as a power supply, which is cheap and simple comparing to others. PIC one-chip microprocessor was used for precise control of a laser power supply on the control part. And the laser cavity was fabricated as an axial and water cooled type. The laser performance characteristics as various parameters, such as pulse repetition rate gas pressure, and gas mixture rate have been investigated. The experiment was done under the condition of total pressure of $CO_2:N_2$:He = 1.3:10, 1:1.5:5 1:9:15 from 6 Torr to 15 Torr and pulse repetition rate from 100 Hz to 900 Hz. As a result, the maximum average output was about 20.5 W at the total pressure of 15 Torr, the gas mixture $CO_2:N_2$:He = 1:9:15 and the pulse repetition rate of 700 Hz.

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Non-contact Vibration Suppression of a Rotating Flexible Disk (회전 유연 디스크의 비 접촉 진동 억제)

  • Um, Yo-Han;Lee, Ho-Ryul;Lee, Sung-Ho;Rhim, Yoon-Chul
    • Transactions of the Society of Information Storage Systems
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    • v.1 no.2
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    • pp.169-174
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    • 2005
  • Current information storage devices read/write data on the rotating disk. The axial vibration of a rotating disk should be suppressed for the successful operation of the device. Information storage devices widely used in these days adopt relatively thick disk which is stiff enough to suppress axial vibration under allowable limit. However, the thickness of the disk is going to be thinner and thinner as the small form factor of the devices is getting preferred by the consumer. In this study, a stabilizer system, which is composed with 8 air bearings, is proposed for suppressing the axial vibration of a $95{\mu}m$ thick PC disk in a non-contacting manner. The performance of the stabilizer system is simulated by numerical computation and then confirmed its results through a series of experiment. A thin and flexible disk has various vibration modes when it rotates in high speed. The stabilizer system generates positive as well as negative pressure due to the rotation of flexible disk so that the force due to the pressure distribution pushes and pulls rotating disk in a non-contacting manner. The balance between positive and negative pressure forces can be obtained by adjusting the area and the slope of the air bearing surface. The axial vibration of the flexible disk of 120mm diameter is suppressed successfully from over $1000{\mu}m$ to $30{\mu}m$ peak-to-peak value at the rotational speed of 5,000rpm.

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Study on Heat Transfer and Pressure Drop Characteristics of Internal Heat Exchanger for $CO_2$ Heat Pump under Cooling Condition ($CO_2$ 열펌프용 내부 열교환기의 냉방조건에서 열전달 및 압력 강하 특성에 대한 연구)

  • Kim, Dae-Hoon;Lee, Sang-Jae;Choi, Jun-Young;Lee, Jae-Heon;Kwon, Young-Chul
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.8
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    • pp.517-525
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    • 2008
  • In order to study the heat transfer and pressure drop of an internal heat exchanger for $CO_2$ heat pump under cooling condition, the experiment and numerical analysis were performed. Four kinds of internal heat exchangers with a coaxial tube type and a micro-channel tube type were used. The experimental apparatus consisted of a test section, a power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. The section-by-section method and Hardy-Cross method were used for the numerical analysis. The effects of the internal heat exchanger refrigerant flow rate, the length of the internal heat exchanger, the operating condition of the gas-cooler, the evaporator and the type of the internal heat exchangers were investigated. With increasing of the flow rate, the heat transfer rate increased about 25%. The heat transfer rate of the micro-channel tube type was higher about 100% than that of the coaxial tube type. With increasing of the length of the internal heat exchanger, the heat transfer rate increased about $20{\sim}50%$. The pressure drop of the low-side tube was larger compared with that of the high-side tube.

DESTRUCTION OF HUMIC MATTERS AND AMMONIA IN THE LANDFILL LEACHATE BY SUPERCRITICAL WATER OXIDATION

  • Kim, Y.K.;Ahn, J.S.;Leung, W.
    • Environmental Engineering Research
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    • v.11 no.6
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    • pp.311-317
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    • 2006
  • Feasibility of destroying synthetic and actual leachate containing humic acids and ammonia compounds by supercritical water oxidation (SCWO) was evaluated. In this study, destruction efficiencies of humic acids and ammonia respectively were investigated at various reaction temperatures and residence times under pressure a supercritical pressure (280 atm). To lower reaction temperature, chemical oxidants were used. The experiment was carried out in a cylindrical batch reactor made of Hastelloy C-276 that can withstand high temperature and pressure. Concentrations of humic acids and ammonia were measured using a $COD_{Cr}$ method and an ammonia selective electrode, respectively. The optimal destructive condition of humic acids in the presence of stoichiometric oxygen(air) was 3 min at $380^{\circ}C$, but the temperature could be lowered to subcritical region ($360^{\circ}C$) along with $H_2O_2$ as an oxidant. For ammonia, the optimal destructive condition with air was 5 min at $660^{\circ}C$, but it was possible to operate the process for 3 minutes at $550^{\circ}C$ or 2 min at $600^{\circ}C$ along with $H_2O_2$ as an oxidant. At 2 min and $550^{\circ}C$ along with $H_2O_2$ as an oxidant, humic and ammonia compounds in the actual leachate were easily destructed and the effluent quality met the Korea Standard Leachate Quality.

Characterization of Via Etching in $CHF_3/CF_4$ Magnetically Enhanced Reactive Ion Etching Using Neural Networks

  • Kwon, Sung-Ku;Kwon, Kwang-Ho;Kim, Byung-Whan;Park, Jong-Moon;Yoo, Seong-Wook;Park, Kun-Sik;Bae, Yoon-Kyu;Kim, Bo-Woo
    • ETRI Journal
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    • v.24 no.3
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    • pp.211-220
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    • 2002
  • This study characterizes an oxide etching process in a magnetically enhanced reactive ion etching (MERIE) reactor with a $CHF_3/CF_4$ gas chemistry. We use a statistical $2^{4-1}$ experimental design plus one center point to characterize the relationships between the process factors and etch responses. The factors that we varied in the design include RF power, pressure, and gas composition, and the modeled etch responses were the etch rate, etch selectivity to TiN, and uniformity. The developed models produced 3D response plots. Etching of $SiO_2$ mainly depends on F density and ion bombardment. $SiO_2$ etch selectivity to TiN sensitively depends on the F density in the plasma and the effects of ion bombardment. The process conditions for a high etch selectivity are a 0.3 to 0.5 $CF_4$ flow ratio and a -600 V to -650 V DC bias voltage according to the process pressure in our experiment. Etching uniformity was improved with an increase in the $CF_4$ flow ratio in the gas mixture, an increase in the source power, and a higher pressure. Our characterization of via etching in a $CHF_3/CF_4$ MERIE using neural networks was successful, economical, and effective. The results provide highly valuable information about etching mechanisms and optimum etching conditions.

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A Study for Change of Audio Data according to Rotation Degree of VR Video (VR 영상의 회전각도에 따른 오디오 데이터 변화에 관한 연구)

  • Ko, Eun-Ji;Yang, Ji-Hee;Kim, Young-Ae;Park, Goo-Man;Kim, Seong-Kweon
    • The Journal of the Korea institute of electronic communication sciences
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    • v.12 no.6
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    • pp.1135-1142
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    • 2017
  • In this paper, we propose an algorithm that can automatically mix the screen and sound by tracking the change of the sound data according to the screen change so that the real sound can be implemented in the personal broadcasting service. Since the personal broadcasting service is often broadcasted lively, it should be convenient to have a real-time mixing. Through experiments, it was confirmed that the sound pressure changes in a wide range in the high frequency band related to the clarity for understanding according to the rotation angle change of the screen. Regression analysis of the sound pressure changes at 2kHz, 4kHz, and 8kHz, The attenuation change of sound pressure was observed at the slope of -1.17, the slope of -2.0, and the slope of -2.44 for each frequency. Therefore, these experiment results can be applied to the VR service. This study is expected to be useful data in the implementation of personal broadcasting service.

Kinetics for the Reaction of Benzyl Benzenesulfonate with Pyridine in Acetone Under High Pressure (Benzyl Benzenesulfonate와 피리딘과의 고압반응에 대한 반응속도론적 연구)

  • Jung-Ui Hwang;Soo-Dong Yoh;Jong-Gi Jee
    • Journal of the Korean Chemical Society
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    • v.24 no.2
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    • pp.150-154
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    • 1980
  • Kinetic studies of the reaction of benzyl benzenesulfonate with pyridine in acetone were carried out by the electric conductivity method under 1 to 2000 bars and at 20 to $40^{\circ}C$. The rate increases with increasing pressure and temperature. The activation enthalpy $({\Delta}H^{\neq}),\;entropy\;({\Delta}S^{\neq})$ and activation volume $({\Delta}V^{\neq})$ of the reaction are obtained by the above experiment. The isokinetic relationship between $({\Delta}H^{\neq})\;and\;({\Delta}S^{\neq})$ for pressure change in the reaction was shown, and its isokinetic temperature was $342^{\circ}K$. From all of the above results it was found that this reaction precedes on the $S_N2$ reaction mechanism in which the rate of the reaction was determined by $C{\cdots}N$ bond formation at transition state.

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