• New & Renewable Energy
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• v.10 no.4
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• pp.9-15
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• 2014

In this study pressure and shaft torque pulsation were measured with variation of head and flow during the model test for a 15 MW Francis Turbine. Pressure pulsations were measured at the inlet of the spiral casing and 4 points in the cone of the diffuser and shaft torque pulsation at the upper position of the turbine. The maximum amplitude of pressure pulsation appeared 2.03% of the maximum rated head with the frequency of 25% of the rated revolution and at the guide vane opening of $10^{\circ}$. Shaft torque pulsation appeared 0.01% of the rated shaft torque, fairly low value. Air was admitted through the cone and pressure pulsation gradually decreased with increase of air flow and kept nearly constant after 5% of the rated flow. A new Francis turbine of which specific speed is 115 m-kW had been designed to rehabilitate the old one and the model test was performed at EPFL. The commercial code, STAR-$CCM^+$ was used for numerical simulation of flow.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.658-663
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• 2003

A process of 3-D stereo particle image velocimetry(PIV)was developed for the measurement of an illuminated sliced section field of 3-D complex flows. The present method includes modeling of camera by a calibrator based on the homogeneous coordinate system, transformation of the oblique-angled image to the right-angled image, identification of 2-D velocity vectors by 2-D cross-correlation equation, stereo matching of 2-D velocity vectors of two cameras, accurate calculation of 3-D velocity vectors by homogeneous coordinate system, removal of error vectors by a statistical method followed by a continuity equation criteria, and finally 3-D display as the post processing. An experimental system was also used for the application of the proposed method. Two high speed digital CCD cameras and an Argon-Ion Laser for the illumination were adopted to clarify the time-dependent characteristics of the leading edge extension(LEX) in a highly swept shape applied to a delta wing found in modern air-fighters.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.1
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• pp.104-111
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• 2017

This research focuses on simulation and visualization of flow field characteristics inside a centrifugal pump. The 3D numerical analysis was carried out by using a numerical CFD tool, addressing a Reynolds Average Navier-Stock code with a standard k-${\varepsilon}$ two-equation turbulence model. The simulation accounts for friction head loss due to rough walls at suction, impeller, discharge areas and volumetric head loss at impeller wear ring. A comparison of performance curves between simulation and experimentation is included, and it reveals a same trend of those results with a small difference of maximum 5 %. At best efficiency point, velocity vectors are smooth but it changes significantly under off-design point, a strong recirculation appears at the outlet of impeller passages near tongue area. A relatively uniform preassure distribution was observed around the impeller in despite of the tongue. Within the volute, because of its geometry, spiral vortexes formed, proving that the flow field in this region was relatively turbulent and unsteady.