• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.6
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• pp.472-476
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• 1998

The surface reactions of silica film($SiO_2-P_2O_5-B_2O_3-GeO_2$) with fluorocarbon plasma has been studied by using angle -resolved x-ray photoelectron spectroscopy(XPS). It has been confirmed that residual carbon consists of C-C and C-CFx bonds and fluorine mainly binds silicon in the case of etched silica by using $CF_4$ gas plasma. The surface reaction of silica with various fluorocarbon gases, such as $CF_4,C_2F_6 and CHF_3$ were investigated. XPS results showed that though the etching gases were changed, the elements and binding states of the residual layers on the etched silica by using various fluorocarbon gas plasma were nearly the same . This seems to be due to the high volatility of byproducts, that is, $SiF_4 and CO_2$ etc..

• Journal of computational fluids engineering
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• v.11 no.2 s.33
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• pp.8-18
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• 2006

A CFD benchmark calculation for a steam blowdown test was performed for 30 seconds to develop the methodology of numerical analysis for the thermal mixing between steam and subcooled water. In the CFD analysis, the grid model simulating the sparger and the IRWST pool were developed by the axisymmetric condition and then the steam condensation phenomena by a direct contact was modelled by the so-called condensation region model. Thermal mixing phenomenon in the subcooled water tank was treated as an incompressible flow, a free surface flow between the air and the water, a turbulent flow, and a buoyancy flow. The comparison of the CFD results with the test data showed a good agreement as a whole, but a small temperature difference was locally found at some locations. The commercial CFD code of CFX4.4 together with the condensation region model can simulate the thermal mixing behavior reasonably well when a sufficient number of mesh distribution and a proper numerical method are adopted.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.52-58
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• 2014

This study consists of two parts. The first discusses the development of a single production forming machine which was reported in earlier papers. The second outlines the development of a multi-production forming machine, which consists primarily of a film feeding unit, an unwinding unit, and a heating block unit. The heating block unit of the multi-production forming machine has 30 members per die. An analysis of the stress deformation and temperature deviation of this machine is carried out using ANSYS Workbench and CFX-11 under the design conditions. According to this analysis, the maximum deflection in the Z-direction is $0.05104{\mu}m$ and the maximum temperature deviation is $0.7^{\circ}C$ when the temperature of the heating block unit is $175^{\circ}C$. It was also found that these values are structurally safe. The advantage of the developed multi-production forming machine is demonstrated to be in its offering of a proper voice test.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.387-391
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• 2011

Since MEMS based micro actuators or generating devices have high efficiency per volume, plenty of research are ongoing. Among them, MEMS based millimeter-scale micro gas' turbine is one of the most powerful issue for replacing chemical batteries. However, since limiting of MEMS manufacturing technique, it is very difficult that makes wide turbine bearing area. It causes low DN number, so sufficient bearing force is hard to achieve. Thus, the most important issue on micro gas turbine is proper bearing design which can keep rotor stable during operation. In order to that, micro-scale gas-lubricated bearing is generally used. In this paper, basic feasibility study and design of journal bearing for 10mm diameter micro gas turbine is described Journal bearing is hydrostatic gas-lubricated type. Numerical simulation is performed with ANSYS CFX 11.0 which is commercial numerical tool. Repulsive force when there is radial displacement in bearing and returning time is calculated using steady and unsteady cases. Auto re-meshing technic is used for moving mesh unsteady cases which simulate displacement of axis and its movement. The simulation results are used for further design of micro gas turbine, and experiment will be done later.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.375-382
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• 2009

Hydraulic instability associated with pressure fluctuations is a serious problem in hydraulic machinery. Pressure fluctuations are usually a result of a strong vortex created in the centre of a flow at the outlet of a runner. At every radial turbine and also at every single regulating axial turbine, the draft tube vortex appears at part-load operating regimes. The consequences of the vortex developed in the draft tube are very unpleasant pressure pulsation, axial and radial forces and torque fluctuation as well as turbine structure vibration. The consequences of the vortex are transferred upstream and downstream with amplitude and frequency modulation in respect of the turbine operating regime, cavitation conditions and air admitted content. Numerical prediction of the vortex appearance in the design stage is a very important task. The amplitude of the pressure pulsation is different for each operating regime therefore the main goal of this research was to numerically predict pressure pulsation amplitude versus different guide vane openings and to compare the results with experimental ones. For the numerical flow analysis of a complete Francis turbine (FT), the computer code ANSYS-CFX11 has been used.

• Journal of Power System Engineering
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• v.16 no.4
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• pp.24-29
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• 2012

The numerical analysis by using CFX 11.0 commercial code was done for prediction of fluid flow and thermal field in the vertical heat exchanger. The present experimental studies were also conducted to investigate the effects of circulating solid particles on the fluid flow and temperatures in the fluidized bed vertical shell and tube type heat exchanger with counterflow, at which the solid particles of glasses (3 $mm{\Phi}$) were used in the fluidized bed with a smooth tube. The effect of circulation on the distance(L) of tube inlet and baffle plate was also examined. The present experimental and numerical results showed that the particles in the distance (Ds) of 15 mm showed a more efficient circulation without stacked the space and the LMTD(Log Mean Temperature Difference) in the fluidized bed type was much lower than that in the typical type shell and tube heat exchanger.

• Nuclear Engineering and Technology
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• v.41 no.10
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• pp.1275-1284
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• 2009

A directly heated $SO_3$ decomposer for the sulfur-iodine and hybrid-sulfur processes has been introduced and analyzed using the computational fluid dynamics (CFD) code CFX 11. The use of a directly heated decomposition reactor in conjunction with a very high temperature reactor (VHTR) allows for higher decomposition reactor operating temperatures. However, the high temperatures and strongly corrosive operating conditions associated with $SO_3$ decomposition present challenges for the structural materials of decomposition reactors. In order to resolve these problems, we have designed a directly heated $SO_3$ decomposer using RA330 alloy as a structural material and have performed a CFD analysis of the design based on the finite rate chemistry model. The CFD results show the maximum temperature of the structural material could be maintained sufficiently below 1073 K, which is considered the target temperature for RA 330. The CFD simulations also indicated good performance in terms of $SO_3$ decomposition for the design parameters of the present study.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.4
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• pp.370-378
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• 2008

It is reported to develop the driving pump for the Low Noise Large Cavitation Tunnel(LOCAT) which is under construction at Maritime & Ocean Engineering Research Institute(MOERI). For low background noise condition of the LOCAT, it is crucial not only the best pump efficiency but also no cavity occurrence at any operating conditions. Design condition of the pump is determined by considering the required pump headrise, flow quantity, shaft rotation velocity and pump diameter. Performance analysis of the pump is conducted using commercial CFD codes ($BladeGen^+$, CFX-10), and the predicted results are verified by a series of model tests. Cavity was not observed at any operating condition in the model test, which were conducted at the midium cavitation tunnel of MOERI. The optimum pump for LOCAT, named as LP-11, was successfully developed through a series of pump design processes composed of blade design, performance analysis and model test.

• The KSFM Journal of Fluid Machinery
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• v.15 no.5
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• pp.48-53
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• 2012

This paper presents a systematic procedure for three-dimensional noise analysis of an axial-flow fan by using computational aero-acoustics based on Ffowcs Williams-Hawkings equation. Flow-fields of a basic fan model are simulated by solving three-dimensional, unsteady, Reynolds-averaged Navier-Stokes equations using the commercial code ANSYS CFX 11.0. Starting with steady flow results, unsteady flow analysis is performed to extract the fluctuating pressures in the time domain at specified local points on the blade surface of the axial flow fan. The perturbed density wave by rotating blades reaches at the observer position, which is simulated by an in-house noise prediction software based on Ffowcs Williams-Hawkings equation. The detailed far-field noise signatures from the axial-flow fan are analyzed in terms of source types, field characteristics, and interpolation schemes.

• The KSFM Journal of Fluid Machinery
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• v.16 no.4
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• pp.10-14
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• 2013

In this study, we have numerically investigated the hydraulic efficiency with various values of discharge angle($11^{\circ}$, $12^{\circ}$, $14^{\circ}$, $15^{\circ}$, $17^{\circ}$, $18^{\circ}$, $20^{\circ}$) in the Francis turbine of hydropower generation under 15MW with fixed values of head range of 151m and flow rate($10.97m^3/s$). We also conducted the numerical analysis with constant inlet angle in the Francis turbine using the commercial code, ANSYS CFX. Hydraulic characteristics for different values of the runner blade angle are investigated. The results showed that the change of discharge angles significantly influenced on the performance of the turbine hydraulic efficiency.