• Title/Summary/Keyword: Wall flow

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An experimental study of particle deposition from high temperature gas-particle flows (고온의 기체 입자 유동으로부터 입자부착 현상에 관한 실험적 연구)

  • 김상수;김용진
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.3
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    • pp.501-508
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    • 1987
  • Experimental studies of particle (TiO$\_$2/) deposition from the laminar hot gas particle flow (about 1565K) onto the cold wall surface (about 1215K-1530K) were carried out by the 'real time' laser light reflectivity method (LLRM) and the photographs of scanning electron microscope(SEM). The LLRM was used for the measurement of thermophoretic deposition rates of small particles (d$\_$p/<3.mu.m), and the photographs of SEM were used for determining what factors control the collection of particles having diameters ranging from 0.2 to 30 microns. Two phenomena are primarily responsible for transport of the particles across the laminar boundary layers and deposition: (1) particle thermophoresis (i.e. particles migration down a temperature gradient), and (2) particle inertial impaction, the former effect being especially larger factor of the particle deposition in its size over the range of 0.2 to 1 microns. And also, this study indicates that thermophoresis can be important for particles as large as 15 microns. Beyond d$\_$p/=16.mu.m, this effect diminishes and the inertial impaction is taken into account as a dominant mechanism of particle deposition. The results of present experiments found to be in close agreement with existing theories.

Synthesis of Silica/Alumina Composite Membrane Using Sol-Gel and CVD Method for Hydrogen Purification at High Temperature (Sol-gel 및 CVD법을 이용한 고온 수소 분리용 silica/alumina 복합막의 합성)

  • 서봉국;이동욱;이규호
    • Membrane Journal
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    • v.11 no.3
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    • pp.124-132
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    • 2001
  • Silica membranes were prepared on a porous ${\alpha}$-alumina tube with pore size of 150nm by sol-gel and chemical vapor deposition(CVD) method for hydrogen separation at high temperatures. Silica and ${\gamma}$-lumina membranes formed by the sol-gel method possessed a large amount of mesopores of a Knudsen diffusion regime. In order to improve the $H_2$ selectivity, silica was deposited in the sol-gel derived silica/${\gamma}$-alumina layer by thermal decomposition of tetraethyl orthosilicate(TEOS) at $600^{\circ}C$. The CVD with forced cross flow through the porous wall of the support was very effective in plugging mesopores that were left unplugged in the membranes. The CVD modified silica/alumina composite membrane completely rejected nitrogen permeation and thus showed a high $H_2$ selectivity by molecular sieve effect. the permeation of hydrogen was explained by activated diffusion and the activation energy was 9.52kJ/mol.

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Compressible Simulation of Rotor-Stator Interaction in Pump-Turbines

  • Yan, Jianping;Koutnik, Jiri;Seidel, Ulrich;Hubner, Bjorn
    • International Journal of Fluid Machinery and Systems
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    • v.3 no.4
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    • pp.315-323
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    • 2010
  • This work investigates the influence of water compressibility on pressure pulsations induced by rotor-stator interaction (RSI) in hydraulic machinery, using the commercial CFD solver ANSYS-CFX. A pipe flow example with harmonic velocity excitation at the inlet plane is simulated using different grid densities and time step sizes. Results are compared with a validated code for hydraulic networks (SIMSEN). Subsequently, the solution procedure is applied to a simplified 2.5-dimensional pump-turbine configuration in prototype with different speeds of sound as well as in model scale with an adapted speed of sound. Pressure fluctuations are compared with numerical and experimental data based on prototype scale. The good agreement indicates that the scaling of acoustic effects with an adapted speed of sound works well. With respect to pressure fluctuation amplitudes along the centerline of runner channels, incompressible solutions exhibit a linear decrease while compressible solutions exhibit sinusoidal distributions with maximum values at half the channel length, coinciding with analytical solutions of one-dimensional acoustics. Furthermore, in compressible simulation the amplification of pressure fluctuations is observed from the inlet of stay vane channels to the spiral case wall. Finally, the procedure is applied to a three-dimensional pump configuration in model scale with adapted speed of sound. Normalized Pressure fluctuations are compared with results from prototype measurements. Compared to incompressible computations, compressible simulations provide similar pressure fluctuations in vaneless space, but pressure fluctuations in spiral case and penstock may be much higher.

Resonance May Elucidate New Bone Formation Induced by Low amplitude and High frequency Mechanical Stimuli (고주파 미세자극에 의한 뼈의 생성에 관한 모델링)

  • Yoon, Young June;Kim, Moon-Hwan;Bae, Cheol-Soo
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.1 no.3
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    • pp.27-32
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    • 2008
  • Bone is a self-assembly material. It is known that the low amplitude and high frequency mechanical stimulus, which is much less amplitude but higher frequency than those induced by the normal activity, can induce new bone formation. The vibrating resonance is employed to elucidate why new bone is formed by this kind of mechanical stimulus. For example, as 30 Hz and $5{\mu}{\epsilon}$ mechanical stimulus is applied at the wall of canaliculus (the tiny tube type pathway of bone fluid flow and the diameter of canaliculus is less than 200nm), the osteocytic cell membrane experiences $1,000{\mu}{\epsilon}$ strain due to the vibrating resonance. Two experiments will follow after this pilot study; (1) observing the MAPK pathway of osteocytes by using in-vitro cell culture and (2) visualizing the actin filament network in the osteocytes by using the imaging technique, such as confocal laser scanning microscope.

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Characteristics of Multi staged Combustion on a Double-cone Partial Premixed Nozzle (이중 콘형 부분 예혼합 GT 노즐의 다단 연소특성)

  • Kim, Han Seok;Cho, Ju Hyeong;Kim, Min Kuk;Hwang, Jeongjae;Lee, Won June
    • Journal of the Korean Institute of Gas
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    • v.24 no.1
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    • pp.49-55
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    • 2020
  • Experimental investigations were conducted to understand the multi-staged combustion characteristics of a swirl-stabilized double cone premixed burner nozzle used for industrial gas turbines for power generation. Multi-staged combustion is implemented by injecting the fuel through the existing manifold of the side slots as well as through the apex of the cone with two fuel injection angles which are slanted or axial. NOx and CO emissions, and wall temperature distributions were measured for various fuel distributions and operating conditions. Results show that NOx emissions are decreased when the fuel distribution to the apex is 3% of the total amount of fuel, which is due to more uniform fuel distribution inside the nozzle, hence less hot spots at the flame. NOx emissions are rather increased when the fuel distribution to the apex is 8% of the total amount of fuel for axial fuel injection by occurrence of flash back in premixing zone of burner.

Combustion Characteristics of a Double-cone Partial Premixed Nozzle with Various Fuel hole Patterns (이중 콘형 부분 예혼합 GT 노즐의 연료 분사구 형상 변화에 대한 연소특성)

  • Kim, Han Seok;Cho, Ju Hyeong;Kim, Min Kuk;Hwang, Jeongjae;Lee, Won June
    • Journal of the Korean Institute of Gas
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    • v.24 no.4
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    • pp.25-31
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    • 2020
  • Experimental investigations were conducted to examine the combustion characteristics of a swirl-stabilized double cone premixed burner nozzle used for industrial gas turbines for power generation. Several variants with different fuel injection patterns are tested to compare the combustion characteristics such as NOx and CO emissions, stability, and wall temperature distributions. Main results show that NOx emissions and stability are decreased either when the fuel hole diameter is decreased with the same number of fuel holes, or when the number of fuel holes is reduced with the same total area of fuel holes, both of which are due to a higher penetration of fuel into the air stream. Not only is NOx reduced but also stability is enhanced when the fuel hole diameter varies in an alternating manner with the same total area of fuel holes, showing that NOx reduction is due to a higher penetration of mean fuel injection path while stability enhancement is due to a lowered penetration of minimum fuel injection path.

A Study on the Characteristics of Interior Elements of Frank Lloyd Wright's Residential Design (F. L. Wright의 주택특성과 실내디자인 요소분석에 관한 연구)

  • 서수경
    • Korean Institute of Interior Design Journal
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    • no.5
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    • pp.45-52
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    • 1995
  • Frank Lloyd Wright, a master of the 20th Century Ar-chitecture, contributed tremendously in creating a wholly new form of American architecture called Prairie Style. His idea behind the development of the building structur-al system, organic relationships between inner and outer space, horizontal vertical lines, and idea of extending and expanding interior spaces came from nature. He had completed over 390 projects throughout his life and 90% of those projects were residential design. The most typical characteristic shared by many of his residential design was that each design element, whether it is functional or aesthetical, has close relationship to or-ganic nature, human scale, theoretical floor plants, and maximum emphasis on horizontal lines in respect to na-ture. His concept of "flow of spaces" reformed common the-ory of room next to room in a enclosed space. His sense of "wall" was no longer the side of a box. Careful selec-tion of finishing materials, colors, and natural images en-hance the design as well. F.L. Wright was an artist, designer, and architect who believed the exterior space should have direct relationship to the interior space. His architectural philosophy was not only to design exterior of architecture but also to ful-fill his space through the careful development of interior elements such as furniture, and lighting fixture. Even the patterns for leaded glass windows were designed to have unified appearance from outside to inside of the house. The objective of this study was to analyze floor plans, spatial organizations, and interior design elements of the houses which represent the best of F.L. Wright's design principles and philosophy behind Prairie Style. The meth-od used to collect informations for this study was based on books, articles, journals, and actual site visits. actual site visits.

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CFD Analysis of Trap Effect of Groove in Lubricating Systems: Part I - Variation in Cross-Sectional Shape of Groove (그루브의 Trap 효과에 대한 CFD 해석: 제 1부 − 그루브 단면 형상의 변화)

  • Hong, Sung-Ho
    • Tribology and Lubricants
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    • v.32 no.3
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    • pp.101-105
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    • 2016
  • Trap effect of groove is evaluated in a lubricating system using computational fluid dynamics (CFD) analysis. The simulation is based on the standard k-ε turbulence model and the discrete phase model (DPM) using a commercial CFD code FLUENT. The simulation results are also capable of showing the particle trajectories in flow field. Computational domain is meshed using the GAMBIT pre-processor. The various grooves are applied in order to improve lubrication characteristics such as reduction of friction loss, increase in load carrying capacity, and trapping of the wear particles. Trap effect of groove is investigated with variations in cross-sectional shape and Reynolds number in this research. Various cross-sectional shapes of groove (rectangular, triangle, U shaped, trapezoid, elliptical shapes) are considered to evaluate the trap effect in simplified two-dimensional sliding bearing. The particles are assumed to steel, and defined a single particle injection condition in various positions. The “reflect” boundary condition for discrete phase is applied to the wall boundary, and the “escape” boundary condition to “pressure inlet” and “pressure outlet” conditions. The streamlines are compared with particles trajectories in the groove. From the results of numerical analysis in the study, it is found that the cross-sectional shapes favorable to the creation of vortex and small eddy current are effective in terms of particle trapping effect. Moreover, it is found that the Reynolds number has a strong influence on the pattern of vortex or small eddy current in the groove, and that the pattern of the vortex or small eddy current affects the trap effect of the groove.

Studies on the Heat Storage Using the Hydration/Dehydration of the Calcined Dolomite (소성 Dolomite의 수화 및 탈수반응을 이용한 축열에 관한 연구)

  • Lee, Soo-Kag;Lee, Young-Sei;Kim, Jong-Shik
    • Applied Chemistry for Engineering
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    • v.3 no.3
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    • pp.507-515
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    • 1992
  • This study was carried out to investigate the heat-storage/-release characteristics of the thermochemical reaction of the calcined dolomite and steam system for the application of regenerative heat exchangers with the packed bed shape experimental apparatus. The experimental data were obtained at the following conditions ; the hydration temperature was $150-400^{\circ}C$, the dehydration temperature was $700-800^{\circ}C$ and the steam mass flow rates were 294, 430 and 567 g/hr. In the present study, it was found that MgO of the calcined dolomite was not hydrated during the hydration process under the studied experimental conditions. Therefore, MgO of the calcined dolomite can be regard as an inert material. Because the reaction was proceeded from the packed bed input to packed bed output and from wall to center, it could be thought that the rate determining step is not the reaction itself but the heat transfer.

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Bioconversion of Pytogallo from Gallic Acid by Pseudomonas sp. KS-96 using Rotating Disc Contactor (회전원판 반응조를 이용한 Pseudomonas sp. KS-96에 의한 gallic acid로부터 Pyrogallol의 전환)

  • An, Seung-Man;Kim, Dong-Suck;Jeong, Young-Kee;Lim, Bock-Gu;Lee, Heung-Su;Ryu, Beung-Ho
    • Journal of Life Science
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    • v.7 no.2
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    • pp.112-118
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    • 1997
  • In previous paper Pseudomonas sp. Ks-96 isolated from the bioconversion into pyrogallol from gallic acid . Continuous bioconversion of pyrogallol was carried out using rotatory disc contactor immobilized Pseudomonas sp. Ks-96 . Enzyme activity of gallate decarboxylase released from Pseudomonas sp. Ks-96 were shown at the highest activity on 24h incubation. Culture media containing gallic acid supplied on the flow rate of 20m${\ell}$/h until thickness of cells wall reached steady state. Bioconversion rate of pyrogallol from gallic acid showed at highest level ranging from 18hr to 36h according to time courses. Continuous bioconversion of pyrogallol using rotating disc contactor was about 82% and 80% between 6 and 8 days at the feeding rate of 300m${\ell}$ per hour in the medium containing 15g/${\ell}$ gallic acid.

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