• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.158-162
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• 2000

Secondary flows in gas turbines, especially those associated tip clearance and labyrinth seals, have become a focus of interest for engine manufacturers. In the past, many analytical and experimental studies, which focused solely on the flows in either tip clearances or seals, have been conducted. This paper presents an analytical model that describes the flow response in a single stage turbine induced by a finite sealing gap at the turbine rotor. The flow is assumed to be axisymmetric and the analysis is done in the meridional plane. Upon going through the stage, the radially uniform upstream flow is assumed to split into two streams one associated with the seal and the other which has gone through the blades. The former is referred to as the leakage flow, and the latter is referred the as the passage flow. The passage flow is assumed to be inviscid and incompressible while the flow in the seal can be modeled as either inviscid or viscous. Thus, the model is capable of predicting the kinematic effects of labyrinth seals on the turbine flow field.

• Journal of Mechanical Science and Technology
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• v.19 no.4
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• pp.993-1000
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• 2005

A vehicle cruise control strategy designed based on human drivers driving characteristics has been investigated. Human drivers driving patterns have been investigated using vehicle driving test data obtained from 125 participants. The control algorithm has been designed to incorporate the driving characteristics of the human drivers and to achieve natural vehicle behavior of the controlled vehicle that would feel comfortable to the human driver. Vehicle following charac­teristics of the cruise controlled vehicle have been investigated using real-world vehicle driving test data and a validated simulation package.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.2
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• pp.135-144
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• 1995

조립작업에 있어서의 경로계획(path planning)에 대하여 지금까지 많은 연구가 진행되어 왔으며, 그것의 주종을 이루는 것들은 cell decomposition 방식과 potential field 방식이다. 이러한 방식들은 free space를 세분하거나 potential field를 계산하는데 많은 시간을 필요로 하며, 조립부품 이동영역이 configuration space로 먼저 치환이 되어야 하는 문제점들이 발생하게 된다. 그러므로, 만약에 조립부품에 대한 이동환경이 복잡하지 않고 알려져 있으면 위의 방식들은 비용적인 면에서 많은 낭비를 가져온다. 본 논문에서는 간단하면서도 알려진 작업환경에서 효과적인 조립부품의 경로계획 알고리즘을 개발하였다. 먼저, channel, junction 및 간격 유지계수(clearance gap)의 개념을 도입하고, 이 개념들을 이용하여 룰 방식의 알고리즘을 개발하였다. 그리고, 이 알고리즘을 이동용 로봇의 경로계획에도 적용될 수 있음을 보였다.

• Tribology and Lubricants
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• v.22 no.1
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• pp.26-32
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• 2006

This work analyzes the behaviors of aerated lubricant in the gap between con-rod bearing and journal. Aerated lubricant influences two major factors on the film formation. One is the density characteristics of the lubricant due to the volume change by the bubbles and the other is the viscosity characteristics of the lubricant due to the surface tension of the bubble. Those two major factors surprisingly increase the load capacity in certain ranges of bubble sizes and densities. Modified Reynolds' equation is developed with the consideration of aerated ratio in the lubricant and journal locus is computed with the Mobility method after the computation of two dimensional pressure distributions over the bearing area.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.232-238
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• 1997

In this paper, a theoretical method is presented to design a hydraulic control valve system that consist of an important component in the hydraulic snubber. The hydraulic snubber is used essentially to support the piping systems at power plants. To calculate the force due to pressure drop and flow rate in the valve orifice and by-pass hole, Bernoulli equation is used. The Reynolds equation are numerically analyzed in the clearance gap between the valve cone and valve seat to estimate the friction force and leakage flow rate. Based on the detailed theoretical data, we developed successfully the hydraulic snubber for power plants.

• Journal of Welding and Joining
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• v.18 no.4
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• pp.38-47
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• 2000

Characteristics of the interface between tube and tube sheet which were formed by explosive expansion and roll expansion, have been studied in the research. The results are as follows: Optimum amounts of explosives for the expansion of Alloy 600 (19.05mm and 15.88mm) were found to be RDX 3.5-8.5g/m. Because explosive expansion caused les strain hardening and increased bounding strength, characteristics of the explosively expanded were better than those of mechanically expanded. As the transition region of the explosive expansion is inactive, the resistance to the stress corrosion cracking increases by 30∼40% compared to the roll and hydraulic expansion.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.159-162
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• 2008

In this paper, a numerical simulation of three-dimensional flow field and heat transfer coefficient distribution are conducted for two types of gas turbine blade with plane and squealer tips. The numerical results show that gas turbine blade with squealer tip considerably changes the flow structures near the tip regions of pressure and suction sides, so the overall heat transfer coefficients on the tip and shroud with squealer tip are lower than those with the plane tip blade. Finally, the effect of tip gap clearance on the flow field and heat transfer characteristics are investigated.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.430-435
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• 2003

Detailed heat transfer coefficient distributions on a gas turbine blade tip were measured using a hue-detection base transient liquid crystals technique. The heat transfer coefficients on the shroud and near tip regions of the pressure and suction sides of a blade were also measured. Both plane tip and squealer tip blade were considered. The heat transfer measurements were taken at the three different tip gap clearance of 1.0%, 1.5%, and 2.5% of blade span. Results show the overall heat transfer coefficients on the tip and shroud with squealer tip blade were lower than those with plane tip blade. However, the reductions of heat transfer coefficients near the tip regions of the pressure and suction sides were not remarkable.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.32-38
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• 2006

A vehicle adaptive cruise control strategy based on human drivers' driving characteristics has been investigated. Human drivers driving characteristics have been analyzed using vehicle test data obtained from 125 participants. The control algorithm has been designed to incorporate the driving characteristics of the human drivers and to achieve natural vehicle behavior of the controlled vehicle that would reduce the workload of the human driver. Vehicle following characteristics of the cruise controlled vehicle have been compared to real-world driving radar sensor data of human drivers using a validated vehicle simulator. and compare nominal cruise control and adaptive cruise control.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.4
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• pp.410-415
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• 2011

A cylindrical type of self-controlled restrictor is designed for hydrostatic bearing of crank shaft for a grinding wheel spindle. The effect of operation parameters, clearance between spindle and housing on bearing stiffness are analyzed to determine the optimum conditions of operation parameters. The lowest values of the supply pressure and the loads by the theoretical and experimental results assuming oil film thickness and shape of pocket are compared.