• Water for future
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• v.26 no.4
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• pp.97-105
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• 1993

This paper presents the results of a study conducted to improve the understanding of the characteristics of cylindrical capsule flow in a pipeline by taking into account of the effect of capsule density uniformity. The effect of capsule density variation in the axial direction was studied both experimentally and anaytically. The experiments were conducted in a 190mm diameter straight pipe 17m long. The velocity, gap and tilt of capsules were measured under various conditions, In order to interpret the data on various capsule density conditions, the stability index given in the dimensionless number was introduced. The motion of capsules in pipelines is strongly affected by the stability of the capsules characterized by the stability index. The experiments conducted prover that the stability index is a valid criterion for explaining and correlating data on the capsule motion and the capsule density uniformity.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.108-113
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• 1996

Several analytical models for the departure from nucleate boiling (DNB) phenomenon have been developed during the last decade. Among these, Chang & Lee's model based on a bubble crowding mechanism is remarkable in the fundamental features characterized as the formulation of mass, energy, and momentum balance equation at thermal-hydraulic conditions leading to the DNB. However, Bricard and Souyri remarked that the assumption of stagnant bubbly layer at the DNB condition is questionable and the signs on the axial projections of the momentum fluxes at the core/bubbly layer interface in the momentum balance equations are erroneous. From this remark, Chang & Lee's model has been re-examined and modified by correcting the erroneous treatments in the momentum balance equations and removing the spurious assumptions. The revised model predicts well the extensive DNB data of water in uniformly heated tubes at low qualities and shows more accurate prediction compared with the original model.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.2
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• pp.43-53
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• 1989

In this research programs, a series test was conducted to show the effects of freeze/thaw process on the various soil properties. The tests were carried out taken from the west sea shore of Korean peninsular and the west sea shore of Scotland, and their results are as follows; 1. There was a positive total heave in a freezing run, although water may he expelled for the sample initially. The water flow must he reverse' from expulsion to intake. 2. The confining pressure had an overriding influence on the heave and frost penetration, a sudden change of the axial strain at failure with strain rate was observed occuring at a strain rate between 10-5 and 10-6, and the initial friction angle of frozen clay was appeared zero. 3. There was shown a significant decrease in liquid limit of soil which was subjected to freeze/thaw process for the initial value of about 20% because of soil particles aggregation. 4. The cyclic freeze/thaw caused a sinificant reduction in shear strength and its thixotropic regain. The frozen/thawed soil exibited negative strength regain, particularly at high freeze/thaw cycles. 5. The freezing temperature greatly influenced on the failure strength of soils and this. Trend was more pronounced the lower the freezing temperature and shown the ductile failure with indistinct peaks.

• The KSFM Journal of Fluid Machinery
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• v.7 no.2 s.23
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• pp.27-34
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• 2004

The performance of a centrifugal compressor composed of an impeller, tandem diffuser rows and axial guide vanes has been predicted numerically and compared with available experimental results on its design rotational speed. The pitchwise-averaged mixing plane method was employed for the boundaries between rotor and stator to obtain steady state solutions. The overall characteristics showed difference according to the relative positions of tandem diffuser rows while the characteristics of impeller showed almost identical result. The numerical results agree with the measured data in respect of their tendency. It turned out that $0\%$ of relative positions is the worst case in terms of static pressure recovery and efficiency. According to the experimental results, some pressure fluctuations and malfunction of the compressor were observed for $75\%$ case. However, this numerical calculation using mixing plane method did not capture any of those phenomena. Thus, unsteady flow calculation should be performed to investigate the stability of the compressor caused by different diffuser configuration.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.231-236
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• 2020

A water reforming reaction high-speed turning incinerator test facility was prepared. The reforming reaction chamber and the combustion chamber were directly connected. The incinerator and dust collecting device were integrated and made into a double bulkhead type air cooling structure. The blower is built into the dust collector to improve spatial efficiency. An axial flow type multi-stage dust collector was applied by collecting dust by using a plurality of dust collecting bins attached to the side of the dust collecting part. As a result of measuring dioxin among the exhausted gases, results below the standard value were obtained. As a result of measuring exhaust gas and heavy metals, results were obtained below the environmental standard.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.9
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• pp.95-102
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• 2008

A miniature metal bellows is used to minimize the excessive flow of the cryogenic gas in Joule-Thomson micro cryocooler. It is made of metal alloy and its geometry is axisymmetric. The bellows is filled with high pressure gas. It contracts or expands in the axial direction for a wide change of temperature, because the pressure and volume inside the bellows must be satisfied with state equation of the gas. Therefore, in order to design the bellows in Joule-Thomson micro-cryocooler, it is important to evaluate deformation of the bellows under internal pressure exactly. Considering geometric nonlinearity, deformations analysis of the bellows were obtained by a commercial finite element code ANSYS, The bellows was modeled by 3-node axisymmetric shell elements with reduced integration. Experiments were also performed to prove the validity of proposed numerical analysis. The results by numerical analysis and experiments were shown in good agreements.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.89-95
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• 2011

In this study, We modeled the deck house of the container ship like the representative bluff body and made the model ship. By using the PIV technique, the exhaust gas anti-reflux effect of the deck house backward according to open and close of the Sunken Deck and installation of the deflector in deck house side were measured in circulating water channel. The experiment system consists of hi-speed camera, laser, image board, host computer. The mean velocity vector and time mean axial velocity were found in deck house backward and the results were compared each case.

• Journal of the Korean Society of Combustion
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• v.7 no.3
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• pp.47-54
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• 2002

The propagation speed of tribrachial flame in laminar propane jets has been investigated experimentally under normal and micro gravity conditions. The displacement speed was found to vary nonlinearly with axial distance because flow velocity along stoichiometric contour was comparable to the propagation speed of tribrachial flame for the present experiment. Approximate solutions for velocity and concentration accounting density difference and virtual origins have been used in determining the propagation speeds of tribrachial flame. Under micro gravity condition, the results showed that propagation speed of tribrachial flame is largely affected by the mixture fraction gradients, in agreement with previous studies. The limiting maximum value. of propagation speeds under micro gravity conditions are in good agreement with the theoretical prediction, that is, the ratio of maximum propagation speed to the stoichiometric laminar burning velocity is proportional to the square root of the density ratio of unburned to burnt mixture.

• Journal of the Korean Society of Combustion
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• v.6 no.2
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• pp.65-70
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• 2001

To investigate statistics of flamelet in a turbulent premixed flame and to obtain components of their burning velocities in a vertical plane above a pipe-flow burner, the local motion of flamelets with respect to gas are measured by specially arranged diagnostics, composed of an electrostatic probe with four identical sensors and a two-color four-beam LDV system. With this technique, the three-dimensional local flame-front-velocity vector is measured by the electrostatic probe for the first time, and simultaneously the axial and radial components of the local gas-velocity vector in a vertical plane above the vertically oriented burner are measured by the LDV system. Two components of burning velocities of planar flamelets can be obtained from these results and are found to be distributed over different directions and to range in magnitude from nearly zero to a few times the planar, unstrained adiabatic laminar burning velocity measured in the unburnt gas. It may be concluded from these results that turbulence exerts measurable influences on flamelets and causes at least some of them to exhibit increased burning velocity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.325-330
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• 2011

A rotor overlap technique was adapted to improve the performance of a axial turbine. The technique secured sufficient flow passage by additional height at the rotor tip and hub. especially in a supersonic turbine, the technique reduced the chance of chocking in the rotor passage, and made to be satisfied the design pressure ratio. However, the technique also made additional losses, like a pumping loss, expansion loss, etc. Therefore, a optimization technique was appled to maximize the improvement of the turbine performance. An approximate optimization method was used for the investigation to secure the computational efficiency. The design variables was shape factors of a rotor overlap. Results indicated that a significant improvement in turbine performance can be achieved through the optimization of the rotor overlap.