• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.57-64
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• 1999

Initial flame development and propagation were visualized under the new ignition system developed to estimate the effects of ignition characteristics on the engine performance in a port injection SI engine. Effects of intake air flow characteristics were also investigated by three different kinds of the swirl control valve. Experiments were performed in an optical single cylinder engine modified form a commercial engine. Flame images were captured through the quartz window mounted in the piston by the high speed video camera and analyzed to compare initial flame development. Results show that IMEP tends to rise slightly as the ignition duration gets longer. The direction of flame propagation is decisively governed by the in-cylinder flow motion. Every flame grows toward the exhaust valve forming a kind of turbulent flame. Initial flame propaagation characteristics are very similar to ones analyzed form pressure data.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.153-159
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• 2007

The performance of a direct-injection type diesel engine often depends on the strength of air flow in the cylinder, shape of combustion chamber, the number of nozzle holes, etc. This is of course because the process of combustion in the cylinder was affected by the mixture formation process. In the present paper, high speed photography was employed to investigate the effectiveness of holes penetrated from the bottom of cavity wall to piston crown for some more useful utilization of air. The holes would function to improve mixing of fuel and air by the increase of air flow in the cylinder. The results obtained are summarized as follows, (1) Activated first of the combustion by shorten of ignition timing and rapid flame propagation (2) Raised the combustion peak pressure, more close to TDC the formation timing of peak pressure.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.3-10
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• 1995

The compressible laminar and turbulent viscous flow on a slender body in supersonic speed as well as subsonic speed has been numerically simulated at high angle of attack. The steady and time-accurate compressible thin-layer Navier-Stokes code based on an implicit upwind-biased LU-SGS algorithm has been developed and specifically applied at angles of attack of 20, 30, 40 deg, respectively. The modified eddy-viscosity turbulence model suggested by Degani and Schiff was used to simulate the case of turbulent flow. Any geometric asymmetry and numerical perturbation have not been intentionally or artificially imposed in the process of computation. The purely numerical results for laminar and turbulent cases, however, show clear asymmetric formation of vortices which were observed experimentally. Contrary to the subsonic results, the supersonic case shows the symmetric formation of vortices as indicated by the earlier experiments.

• 한국가시화정보학회:학술대회논문집
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• 2001.12a
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• pp.151-163
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• 2001

A two color PIV technique has been developed for visualization of complex and high speed flow in a ramjet combustor. Two color PIV has the advantages that velocity distributions in high speed flowfields can be measured simply by varying the time interval between two different laser beams and a directional ambiguity problem can be solved by color separation, and then a signal-to-noise ratio can be increased through nearly perfect cross-correlation. As a basic research of the ramjet engine, a 2-D shaped combustor with two symmetric air intakes has been manufactured and an experimental study has been conducted using a two color PIV technique. The flow characteristics such as recirculation zones, intake air mixing and turbulent kinetic energy have been investigated varying inlet angles and dome heights. It was found that the primary recirculation zone is affected mainly by the dome height, whereas the secondary recirculation zone is influenced by the air inlet angle.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.111-118
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• 2004

A new micro-resolution PIV (Particle Image. Velocimetry) has been developed. To investigate transient phenomena in a microfluidic device, Dynamic micro-PIV system was realized by combining a high-speed camera and a CW(Continuous Wave) laser. The technique was applied to a micro-counter-current flow, consisting of water and butyl acetate. The velocity fields of water in the micro counter-current flow were visualized for a time resolution of 500 $\{mu}s$ and a spatial resolution of 2.2 x 2.2 $\{mu}m$. Using the Dynamic micro-PIV technique, the vortex-like motions of fluorescent particles at the water-butyl acetate interface were captured clearly

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.476-481
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• 2001

In this paper, based on the developed dynamic model of a vacuum circuit breaker mechanism, the development of the new circuit breaker with less energy mechanism is focused. The energy flow analysis of the original mechanism is carried out to show where the elastic potential energies of pre-loaded springs are transmitted. Through energy flow analysis, the concept design of the new circuit breaker with less energy mechanism is proposed, and then the detailed design is carried out through the design process based on the verified dynamic model. Comparing simulation results with experiment using a high-speed camera, the appropriateness of the proposed design procedures for the rapid circuit breaker mechanism is shown.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.28-29
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• 2006

High-Speed Centrifugal Compaction Process (HCP) is a wet compacting method, in which powders are compacted under a huge centrifugal force. The HCP was well applied to small alumina specimens, but the compact easily cracked when we applied the HCP to other materials. We clarified how the cracks introduced and found that the formation of such a flow pattern was related to the Colioli's force in the centrifugal field.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.129-135
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• 2012

High speed casting technology is an attractive method to increase the productivity of continuous casting. However, high speed casting causes flow instability of molten steel in a mold. In this study, Large Eddy Simulation (LES) has been performed to identify the characteristics of mold flow for various shapes of submerged entry nozzles. The LES code has been newly developed to efficiently compute the two-phase flow by using the Fractional Step Method (FSM) combined with the Volume of Fluid (VOF) method. The Immersed Boundary Method was used to implement the shape of the submerged entry nozzle. Three cases of discharge angle of the submerged entry nozzle were computed and compared. The current results shed light on improving shape design of a submerged entry nozzle.

• Journal of the Korean Society for Railway
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• v.19 no.1
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• pp.11-19
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• 2016

The flows around a high speed train are very important because they could affect the aerodynamic characteristics such as drag and acoustic noise. Especially the boundary layer of flows could represent the characteristic of flows around the high speed train. Most previous studies have focused on the boundary layer region along the train length direction for the side of the train and underbody. The measurement and analysis of the boundary layer for the roof side is also very important because it could determine the flow inlet condition for the pantograph. In this study, the roof boundary layer was measured with a 1/20 scaled model of the next generation high speed train, and the results were compared with full-scaled computational fluid dynamics results to confirm their validity. As a result, it was confirmed that the flow inlet condition for the pantograph is about 85% of the train speed. Additionally, the characteristics of the boundary layer, which increases along the train direction, was also analyzed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.953-956
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• 2017

This paper introduces general applications of vehicle's dynamic pressure information which is estimated during the flight. And a method to estimate the dynamic pressure for a high speed vehicle is suggested to sustain reliability of the flight under a high estimation accuracy of the information. The presented method is straightforward with simple relations of the compressible flow but is a still merited idea employed for the high speed vehicle control scheme with great accuracy.