• Wind and Structures
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• v.18 no.3
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• pp.295-320
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• 2014

The characteristics of amplitudes and power spectra of X axial, Y axial, and RZ axial (i.e., body axis) wind forces on a 492 m high-rise building with a section varying along height in typical wind directions are studied via a rigid model wind tunnel test of pressure measurement. Then the corresponding mathematical expressions of power spectra of X axial (across-wind), Y axial (along-wind) and torsional wind forces in $315^{\circ}$ wind directions are proposed. The investigation shows that the mathematical expressions of wind force spectra of the main structure in across-wind and torsional directions can be constructed by the superimposition of an modified wind spectrum function and a peak function caused by turbulent flow and vortex shedding, respectively. While that in along-wind direction can only be constructed by the former and is similar to wind spectrum. Moreover, the fitted parameters of the wind load spectra of each measurement level of altitude are summarized, and the unified parametric results are obtained. The comparisons of the first three order generalized force spectra show that the proposed mathematical expressions accord with the experimental results well.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.288-291
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• 2008

Recently, the importance and necessity of engineering analysis has shown a steady growth. However, researchers working in small and medium enterprises know little about the usefulness of engineering analysis and suffer from lack of technical knowledge. Axial fan is air fluid machinery in various fields of industry such as automobile, electric appliance, and heavy machinery. It is also a time and budget consuming equipment to develop the axial fan through physical experiments. In order to overcome this problem, we have designed and developed a web-base automated simulator for axial fan's fluid analysis using supercomputer. Automated simulator means that all of processes for engineering analysis including pre-process, solving, and post-process can be performed automatically without user intervention after transferring fan model(CAD files) made by user. After executing the simulator with some parameters, user can receive the report including pressure P and flow rate Q. In this paper, we introduce the architecture of our easy and efficient automated engineering analysis simulator, related techniques and result of development.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.52-57
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• 2016

A swash plate-type piston pump is a device used to discharge hydraulic fluid as the volume generated through the piston moves in the direction of the slope by adjusting the angle of its swash plate. In addition, the valve block internalized in the pump includes a flow path for intake from outside, a flow path for discharge, and a pilot conduit line to control discharge pressure and flux. In this study, a numerical analysis is conducted to improve the cracking of the valve block generated during process testing, and the developed pump is evaluated.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.97-103
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• 1997

Effects of fuel injection timing on the lean misfire limit of a sequential MPI SI engine has been investigated. To investigate the interaction of injection timing and intake flow characteristics, so called axial stratification phenomena, 4 kinds of different intake swirl port of the same combustion chamber geometry have been teated in a single cylinder engine test bench. And 2 kinds of fuel, gasoline and compressed natural gas(CNG), were used to see the effect of liquid fuel vaporization. Result shows that combination of port swirl and injection timing governs the lean misfire limit and lean misfire limit envelopes remain almost the same for a given ratio regardless of engine speed. It is also found that two phase flow has some effects on lean misfire limit.

• Journal of the Korean Society of Safety
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• v.14 no.3
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• pp.3-11
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• 1999

The atomic fuel rods between top and bottom end pieces of reactor need to be extended for high combustion rate of future-type fuel to increase the irradiation in the axial direction. For allowing axial extension of the fuel rods, the space between top and bottom end pieces should be expanded. Thus the thickness reduction of the flow plate is necessary. This study was carried out the mechanical strength test by using strain gages as a function of flow plate thickness, the existence of skirt and loading condition for the Korean Fuel Assembly(KOFA). The experimental apparatus was designed for load conditions, uniformly distributed load and displacement. Test method using whiffle tree of uniformly distributed load has been comparatively conservative. The test results were compared with those of finite element analysis and the test method on bottom end piece was established.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1115-1119
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• 2007

Five control methods (Speed Control, PID Gain Scheduling, Loop Time Control, Simple PID, Switching Control) have been applied to the control of an Inline Co-axial valve by the simulation of AMESim. The simulation results have shown that the speed control method is the most stable and the fastest way to reach to the set point in the simulation of the flow control. Moreover, It has been found that the five control methods have the almost same characteristics in the power consumption, the counter electromotive force, and the motor angular velocity. According to the analysis results, the fast and stable control characteristics of the speed control method is the most suitable for the flow control using a inline co-axial valve with a DC(BLCD) motor.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.676-685
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• 1993

A mathematical model was developed to quantify the separation process of threshed grain-straw mixtures. It was made to predict the separation loss from a separation unit consisted of stationary crimped sieve with rotating inner rotor. Experiments were performed to prove the mathematical model by changing various levels of pertinent variables for rice. Good Agreement between the simulated results and observed data under the various test conditions, such as inclination angle of the separator, vane pitch, rotor speed, MOG/G ratio, feed rate, and crop variety and moisture content, were confirmed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.206-213
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• 2002

In this paper, the flow characteristics of an axial fan spraying isothermal compact jet in a confined space were investigated by the experimental methods, the numerical method, and the free jet theory According to the results, the numerical result and the experimental result are agreed well qualitatively and different quantitatively within $\pm1.0%$ for the centerline velocity, the entrainment ratio, and the maximum throw. However, the free jet theory can reasonably predict the centerline velocity except the entrainment ratio and the maximum throw. In other words, the entrainment ratio and the maximum throw by 1.he free jet theory are hard to estimate the characteristics of jet because of restriction of c confined space.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.135-142
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• 2001

Design optimization of a transonic compressor rotor (NASA rotor 37) using response surface method and three-dimensional Navier-Stokes analysis has been carried out in this work. Baldwin-Lomax turbulence model was used in the flow analysis. Three design variables were selected to optimize the stacking line of the blade. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, adiabatic efficiency was successfully improved. Ana, it is found that the design process provides reliable design of a turbomachinery blade with reasonable computing time.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.5
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• pp.1291-1299
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• 1995

In confined coaxial jets, the flow-mixing characteristics depend on the initial conditions at the nozzle outlet such as velocity ratio and nozzle radius ratio. In this study, nozzle ratio(inner/outer) was 0.3. Longitudinal axial velocity, turbulent intensity and Reynolds shear stress were measured by CTA. Measurements were made from the duct inlet to the region where similarity solution could exist. This study investigated flow charicteristics according to the variation of similitude parameter which was derived from the theory of Craya-Cutet. The range of similarity region depends on the variation of the similitude patameter. The form factor obtained from the axial velocity profile in the similarity region was constant. The higher the similitude parameter, the wider the spread rate of the jets. Due to this fact, the similarity conditions developed more quickly and the region where the similarity holds became narrow. Present experimental data confirmed the validity of Craya-Curtet theory.