• Title/Summary/Keyword: Constant pressure mixing

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Study on the Atomization Characteristics of a Counter-swirling Two-phase Atomizer with Variations of Swirl angle (역선회 이류체 미립화기의 선회각 변화에 따른 미립화 특성연구)

  • Kim, N.H.;Lee, S.G.;Ha, M.H.;Rho, B.J.;Kang, S.J.
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.125-130
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    • 2001
  • Experimental and analytical researches have been conducted on the twin-fluid atomizers for better droplet breakup during the past decades. But, the studies on the disintegration mechanism still present a great challenge to understand the drop behavior and breakup structure. In an effort to describe the aerodynamic behavior of the sprays issuing from the internal mixing counter-swirling nozzle, the spatial distribution of axial (U) radial (V) and tangential (W) components of droplet velocities are investigated across the radial distance at several axial locations of Z=30, 50, 80, 120 and 170mm, respectively. Experiments were conducted for the liquid flow rates which was kept constant at 7.95 g/s and the air injection pressures were varied from 20 kPa to 140 kPa. Counter-swirling internal mixing nozzles manufactured at angles of $15^{\circ},\;30^{\circ},\;45^{\circ}$ and $60^{\circ}$ the central axis with axi-symmetric tangential-drilled holes was considered. The distributions of velocities and turbulence intensities are comparatively analyzed. PDPA is installed to specify spray flows, which have been conducted along the axial downstream distance from the nozzle exit. Ten thousand of sampling data was collected at each point with time limits of 30 second. 3-D automatic traversing system is used to control the exact measurement. It is observed that the sprays with all swirl angle have the maximum SMD for on air injection pressure of 20 kPa and 140 kPa with centerline, respectively. The nozzle with swirl angle of $60^{\circ}$ has vest performance.

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The etching characteristics of $(Ba_{0.6}Sr_{0.4})TiO_{3}$ film Using $Ar/CF_{4}$ Inductively Coupled Plasma ($Ar/CF_{4}$ 유도결합 플라즈마로 식각된 $(Ba_{0.6}Sr_{0.4})TiO_{3}$ 박막의 특성분석)

  • Kang, Pill-Seung;Kim, Kyoung-Tae;Kim, Dong-Pyo;Kim, Chang-Il;Lee, Soo-Jae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.05b
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    • pp.16-19
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    • 2002
  • (Ba,Sr)TiO3(BST) thin film is an attractive material for the application in high-density dynamic random access memories (DRAMs) because of the high relative dielectric constant and small variation in dielectric properties with frequency. In this study, (Ba0.6,Sr0.4)TiO3 thin films on Pt/Ti/SiO2/Si substrates were deposited by a sol-gel method and the CF4/Ar inductively coupled plasma (ICP) etching behavior of BST thin films had been investigatedby varying the process parameters such as chamber pressure, ICP power, and substrate bias voltage. To analysis the composition of surface residue following etching BST films etched with different Ar/CF4 gas mixing ratio were investigated using x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometer (SIMS).

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The etching properties of MgO thin films in $Cl_2/Ar$ gas chemistry (유도 결합 플라즈마를 이용한 MgO 박막의 식각특성)

  • Koo, Seong-Mo;Kim, Chang-Il
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07b
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    • pp.734-737
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    • 2004
  • The metal-ferroelectric-semiconductor (MFS) structure is widely studied for nondestructive readout (NDRO) memory devices, but conventional MFS structure has a critical problem. It is difficult to obtain ferroelectric films like PZT on Si substrate without interdiffusion of impurities such as Pb, Ti and other elements. In order to solve these problems, the metal-ferroelectric-insulator-semiconductor (MFIS) structure has been proposed with a buffer layer of high dielectric constant such as MgO, $Y_2O_3$, and $CeO_2$. In this study, the etching characteristics (etch rate, selectivity) of MgO thin films were etched using $Cl_2/Ar$ plasma. The maximum etch rate of 85 nm/min for MgO thin films was obtained at $Cl_2$(30%)/Ar(70%) gas mixing ratio. Also, the etch rate was measured by varying the etching parameters such as ICP rf power, dc-bias voltage, and chamber pressure. Plasma diagnostics was performed by Langmuir probe (LP) and optical emission spectroscopy (OES).

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Aeration Effects on the Performance of Turbocharger Journal Bearing under Constant Load Operating Condition (일정하중 운전조건 하에서 공기혼입이 터보챠져 저어널베이링의 성능에 미치는 영향)

  • Chun, Sang-Myung
    • Tribology and Lubricants
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    • v.23 no.5
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    • pp.207-218
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    • 2007
  • Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure distribution, then the friction in a journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

An Experimental Study on the Atomization Characteristics of Coal-Water-Mxture (CWM의 미립화특성에 대한 실험적 연구)

  • 김윤태;전영남;채재우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1330-1336
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    • 1990
  • The factors to act on atomization of liquid fuel are viscosity, geometric shape of nozzle, atomizing pressure, etc. Most of high viscous liquid fuels show decrease in viscosity by raising the preheat temperature, but the viscosity of liquid fuel like CWM does not readily change with fuel temperature. As an experimental study to investigate the atomizing characteristics of CWM, CWM fuel is atomizing with a twin-fluid atomizer, and the effects of the geometric shape of spray nozzle on atomization are investigated by measuring the Sauter`s Mean Diameter (SMD) of CWM. The summarized results obtained in this study are as follows ; (1) As the ratio of the mass flows of atomizing air to that of fuel (W$_{a}$ /W$_{1}$) increases, 능 decreases when fuel temperature is constant. (2) At the ratio (t/d) 4 of thickness (t) of spray nozzle hole to the diameter (d) of the hole, there is the best atomization. And SMD decreases when t/d is between 1 to 4 and increases when t/d > 4.

Fabrication of W-10wt.%Cu Powder for the Application of Metal Injection Molding (금속사출성형을 위한 W-10wt.%Cu 분말의 제조에 관한 연구)

  • 김순욱;손찬현;김영도;문인형
    • Journal of Powder Materials
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    • v.8 no.4
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    • pp.245-252
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    • 2001
  • Recent remarkable progress in the semiconductor industry has promoted smaller size of semiconductor chips and increased amounts of heat generation. So, the demand for a substrate material to meet both the characteristics of thermal expansion coefficient and heat radiation has been on the increase. Under such conditions, tungsten(W)-copper(Cu) has been proposed as materials to meet both of the above characteristics. In the present study, the W-10wt.%Cu powders were synthesised by the mixing and hydrogen reduction of the starting mixture materials such as W-Cu, $W-CuCl_2$and $WO_3-CuCl_2$ in order to obtain the full densification. The W-10wt.%Cu produced by hydrogen reduction showed the higher interparticle friction than the simple mixed W-10wt%Cu because of the W agglomerates. In the dilatometric analysis the W-10wt.%Cu prepared from the $W-CuCl_2$was largely shrank by heating up $1400^{\circ}C$ at the constant heating rate of $5^{\circ}C$/min. The possibility of application of metal injection molding (MIM) was also investigated for mass production of the complex shaped W-Cu parts in semiconductor devices. The relationship between the temperature of molding die and the pressure of injection molding was analyzed and the heating up stage of 120-$290^{\circ}C$ in the debinding process was controlled for the most suitable MIM condition.

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A Study of Al2O3 Thin Films Etching Characteristics Using Inductively Coupled BCl3/Ar Plasma (유도결합형 BCl3/Ar 플라즈마를 이용한 Al2O3 박막의 식각 특성)

  • Kim, Young-Keun;Kwon, Kwang-Ho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.6
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    • pp.445-448
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    • 2011
  • In this study, the etching characteristics of $Al_2O_3$ thin films were investigated using an ICP (inductively coupled plasma) of $BCl_3$/Ar gas mixture. The etch rate of $Al_2O_3$ thin films as well as the $SiO_2/Al_2O_3$ etch selectivity were measured as functions of $BCl_3$/Ar mixing ratio (0~100% Ar) at a constant gas pressure (10 mTorr), total gas flow rate (40 sccm), input power (800 W) and bias power (100 W). The behavior of the $Al_2O_3$ etch rate was shown to be quite typical for ion-assisted etch processes with a dominant chemical etch pathway. To analyze the etching mechanism using DLP (double langmuir probe), OES (optical emission spectroscopy) and surface analysis using XPS (x-ray photoelectron spectroscopy) were carried out.

The characteristics of $(Ba_{0.5},Sr_{0.5})TiO_3$ thin films deposited on ITO glass for TFELD insulating layer (TFELD 절연층을 위해 ITO glass위에 증착시킨 $(Ba_{0.5},Sr_{0.5})TiO_3$ 박막의 특성)

  • Kim, Jeong-Hwan;Bae, Seung-Choon;Park, Sung-Kun;Kwon, Sung-Ryul;Choi, Byung-Jin;Nam, Gi-Hong;Kim, Ki-Wan
    • Journal of Sensor Science and Technology
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    • v.9 no.1
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    • pp.83-89
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    • 2000
  • BST thin films were deposited on the ITO coated glass for using TFELD insulating layer by rf magnetron sputtering method. $O_2/(Ar+O_2)$ mixing ratio was 10%, substrate temperature was changed from R.T. to $500^{\circ}C$, and working pressure was changed from 5 mTorr to 30 mTorr. BST thin films deposited with various conditions were investigated electrical, optical, structural properties, and stoichiometry. The result of investigation was achieved good fabrication condition that substrate temperature of $400^{\circ}C$, and working pressure of 30 mTorr. Relative dielectric constant of 254 at 1 kHz, leakage current density was below $3.3{\times}10^{-7\;}A/cm^2$ at 5\;MV/cm applied electric field, and transmittance was over 82% at visible range.

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The Optimization of Fuel Injection Nozzles for the Reduction of NOx Emissions in a Large Diesel Engine (대형 디젤엔진의 NOx 저감을 위한 연료분사노즐 최적화 연구)

  • Yoon, Wook-Hyeon;Kim, Byung-Seok;Kim, Dong-Hun;Kim, Ki-Doo;Ha, Ji-Soo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.6
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    • pp.60-65
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    • 2004
  • Numerical simulations and experiments have been carried out to investigate the effect of fuel injection nozzles on the combustion and NOx formation processes in a medium-speed marine diesel engine. Spray visualization experiment was performed in the constant-volume high-pressure chamber to verify the numerical results on the spray characteristics such as spray angle and spray tip penetration. Time-resolved spray behaviors were captured by high-speed digital camera and analyzed to extract the information on the spray parameters. Spray and combustion phenomena were examined numerically using FIRE code. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation processes. Numerical results were verified with experimental data such as cylinder pressure, heat release rate and NOx emission. Finally, the effects of fuel injection nozzles on the engine performance were investigated numerically to find the optimum nozzle parameters such as fuel injection angle, nozzle hole diameter and number of nozzle holes. From this study, the optimum fuel injection nozzle (nozzle hole diameter, 0.32 mm, number of nozzle holes, 8 and fuel injection angle, $148^{\circ}$) was selected to reduce both the fuel consumption and NOx emission. The reason for this selection could be explained from the highest fuel-air mixing in the early phase of injection due to the longest spray tip penetration and the highest heat release rate after $19^{\circ}$ ATDC due to the increased injection duration.

Surface Micelle Formation of Polystyrene-b-Poly(2-vinyl pyridine) Diblock Copolymer at Air-Water Interface

  • Park, Myunghoon;Bonghoon Chung;Byungok Chun;Taihyun Chang
    • Macromolecular Research
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    • v.12 no.1
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    • pp.127-133
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    • 2004
  • We have studied the surface micelle formation of polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) at the air-water interface. A series of four PS-b-P2VPs were synthesized by anionic polymerization, keeping the PS block length constant (28 kg/㏖) and varying the P2VP block length (1, 11, 28, or 59 kg/㏖). The surface pressure-area ($\pi$-A) isotherms were measured and the surface morphology was studied by atomic force microscopy (AFM) after Langmuir-Blodgett film deposition onto silicon wafers. At low surface pressure, the hydrophobic PS blocks aggregate to form pancake-like micelle cores and the hydrophilic P2VP block chains spread on the water surface to form a corona-like monolayer. The surface area occupied by a block copolymer is proportional to the molecular weight of the P2VP block and identical to the surface area occupied by a homo-P2VP. It indicates that the entire surface is covered by the P2VP monolayer and the PS micelle cores lie on the P2VP monolayer. As the surface pressure is increased, the $\pi$-A isotherm shows a transition region where the surface pressure does not change much with the film compression. In this transition region, which displays high compressibility, the P2VP blocks restructure from the monolayer and spread at the air-water interface. After the transition, the Langmuir film becomes much less compressible. In this high-surface-pressure regime, the PS cores cover practically the entire surface area, as observed by AFM and the limiting area of the film. All the diblock copolymers formed circular micelles, except for the block copolymer having a very short P2VP block (1 kg/㏖), which formed large, non-uniform PS aggregates. By mixing with the block copolymer having a longer P2VP block (11 kg/㏖), we observed rod-shaped micelles, which indicates that the morphology of the surfaces micelles can be controlled by adjusting the average composition of block copolymers.