• The KSFM Journal of Fluid Machinery
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• v.14 no.4
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• pp.5-11
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• 2011

This study investigated on details of flow characteristics in a vaneless diffuser of a compressor with 2-dimensional impeller at various flow rates. Experiment for a low speed compressor model in a water reservoir was performed to analyze the flow field in the vaneless diffuser and volute casing, which was done by PIV measurement. It was also focused on the periodic flow patterns occurring at low flow rate near unstable operating region of the compressor. At low flow rate condition, the flow visualization clearly shows that the flow energy from impeller is highly accumulated at the compressor exit by the blockage effect of a flow damper and consequently the reverse flow occurs in the diffuser.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.67-68
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• 2005

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.845-850
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• 2003

Unsteady nature of a tip leakage vortex in an axial flow fan operating at a design and off-design operating conditions has been investigated by measuring the velocity fluctuation in a blade passage with a rotating hotwire probe sensor. Two hot-wire probe sensors rotating with the fan rotor were also introduced to obtain the cross-correlation coefficient between the two sensors located in the vortical flow as well as the fluctuating velocity. The results show that the vortical flow structure near the rotor tip can be clearly observed at the quasi-orthogonal planes to a tip leakage vortex. The leakage vortex is enlarged as the flow rate is decreased, thus resulting in the high blockage to main flow. The spectral peaks due to the fluctuating velocity near the rotor tip are mainly observed in the reverse flow region at higher flow rates than the peak pressure operating condition. However, no peak frequency presents near the rotor tip for near stall condition.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.115-124
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• 2018

In this study, a cold flow test was carried out on a high-speed vehicle facility with a high-altitude environment simulator. Variable test was carried out according to the blockage ratio, angle, and length of the test model. It is confirmed that the blockage rate can be operated in the range of 40%, and that the model should be selected at an angle of 45 degrees or less. The variables of length are less dominant compared to the variables of blockage rate and angle. Through this, a database is obtained according to the parameters of the conical model of the high-speed vehicle test facility.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.346-351
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• 2017

A numerical study has been conducted to investigate flow characteristics of STED with ram structure shape. By increasing the attack angle of shock cone, vacuum pressure is increased because of oblique shock at ram structure and separation point moved to the downstream of the second throat. By increasing blockage ratio, expansion wave angle is increased at ram structure while vacuum pressure is constant.

• Journal of computational fluids engineering
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• v.11 no.3 s.34
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• pp.52-58
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• 2006

A numerical investigation is made of air flow in a spinner equipment used for cleanning and drying flat display panels. A unique feature of the spinner under question is the placement of a torus plate cover over the rotating plate. The turbulent flow is driven by rotation of a large disk and suction by the exhaust system connected to vacuum chamber. The flow is modelled as an axisymmetric two-dimensional flow and computation is conducted by using the FLUENT package with a version of k-$\varepsilon$ turbulence model. The required capacity of the exhaust system is assessed numerically. The usefulness of the cover in controlling air flow circulation is examined. A computational trouble shooting is attempted to resolve the problem of panel rising which occurred in real experiment.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.55-62
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• 1996

In a fuel injection engine, atomization of liquid fuel and mixture formation process has influenced(or affected) directly on the engine performance and pollutant emission. In this study, the characteristics of fuel spray and the behaviors of secondary atomization developed at the downstream of the valves were investigated using an image processing method. Solid and perforated valves are chosen in order to evaluate the valve performance in terns of air flow rate, valve opening angle and valve shape. Experimental results clearly indicate that the spray atomization quality can be improved by increasing the perforated rat io and the blockage rat io in the perforated valve, the characteristics of spray atomization is improved by using the perforated valve with high perforated rat io and blockage ratio.

• 한국전산유체공학회:학술대회논문집
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• 1995.04a
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• pp.30-36
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• 1995

An axisymmetric flow induced by a train moving into a tunnel is numerically simulated. The effect of train shape on wavefront of a compression wave created by a train is investigated parametrically using several model trains having the same nose shape but different blockage. The zonal method combined with the Fortified Solution Algorithm (FSA) is employed as a numerical algorithm to solve this moving body problem. The computational result is compared with the experimental data. Good agreement is obtained, which justifies the present computational approach. The compression waves created by the model trains are compared and the result shows that the pressure gradient of the wavefront of the compression wave becomes small in the case of small blockage even though the nose shape is same. The wavefront is not determined solely by the cross-sectional area distribution of the train nose.

• The KSFM Journal of Fluid Machinery
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• v.7 no.6 s.27
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• pp.55-61
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• 2004

A numerical procedure for optimizing the shape of three-dimensional sedimentation tank is presented to maximize its sedimentation efficiency. The response surface based optimization is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis for multi-phase flow. Standard $k-{\epsilon}$ model is used as a turbulence closure. Three design variables such as, tank height to center feed wall diameter ratio, blockage ratio of center feed wall and angle of distributor are chosen as design variables. Sedimentation efficiency is defined as an objective function. Full-factorial method is used to determine the training points as a means of design of experiment. Sensitivity of each design variable on the objective function has been evaluated. And, optimal values of the design variables have been obtained.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.134-140
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• 1999

A three-dimensional CSCM upwind flux difference splitting Navier-stokes code with two-equation turbulence models was developed to predict the transonic flows in centrifugal compressor diffuser. The k-$\epsilon$ model of Abe et al. performed well in predicting the pressure distribution in the shock wave/turbulent boundary-layer interaction. Three turbulence models predicted the similar distribution of static pressure through the diffuser and showed a good agreement with the experimental results. The secondary flows in the corner were predicted well by these turbulence models. The pressure increase before the throat of the diffuser vane is important for the overall pressure recovery. As the mass flow rate increased the blockage decreased at the throat. The pressure coefficient distribution through the diffuser depended on the throat blockage not on the rotational speed of the impeller.