• Journal of the Korean Institute of Gas
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• v.12 no.4
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• pp.21-28
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• 2008

A numerical analysis is achieved to elucidate the behavior of lifted flames and characteristics of flow near flame zone according to the exit velocity of triple flame, Poiseuille and uniform distribution. For the cases of Poiseuille and uniform nozzle exit velocity, we reviewed previous results with the present numerical results and investigated characteristics of the flame structure near the flame zone comparing with liftoff height generalized by momentum flux. In addition, a close inquiry into the combustion flow characteristics near flame zone was made with the characteristics of velocity, pressure, temperature and chemical reaction. From nozzle to flame zone, center line velocity profile traced well with the velocity profile of typical cold jet flow, but very near the flame zone, this study examined phenomenon that flow velocity decreases very quickly before the flame zone and then increases very quickly after the flame zone. Because flame zone acts as a barrier at the flow region which is before the flame zone and accelerate the flow velocity when it pass through the flame zone. This phenomenon was not clarified previous cold jet flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1700-1716
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• 1996

The two-dimensional, unsteady, laminar conservation equations for mass, momentum, energy and species transport in the gas phase and mass, momentum and energy in the liquid phase are solved simultaneously in spherical coordinates in order to study heating and vaporization of a droplet entrained in the oscillating flow. The numerical solution gives the velocity and temperature distribution in both gas and liquid phase as a function of time. When the gas flow oscillates around an vaporizing droplet, the liquid flow circulates in the clockwise or counterclockwise direction and the temperature distribution in the liquid phase changes its shapes, depending on the gas fow direction. When the gas flow changes its direction of circulating liquid flow is opposite to the gas flow, forming two vortex circulating in the opposite direction. During the heating period, the difference in the maximum and minimum temperature is large, followed by the almost uniform temperature slightly below the boiling temperature. The mass and heat transfer from the droplet depend on the droplet temperature, droplet diameter and the magnitude of relative velocity, giving the droplet lifetime different from the d$^{2}$-law.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.69-76
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• 1991

A design method based on the surface vorticity distribution is developed to generate a two-dimensional blade section for prescribed velocity distribution in potential flow. The boundary condition used to determine the strength of vorticity distribution requires that the surface of blade section should be a streamline of the resulting flow. In order to obtain the required final geometry of a two-dimensional blade section, an iterative procedure is used. A computer program is developed and several numerical results are presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.7
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• pp.911-918
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• 1997

The turbulent viscous wake flows behind a single airfoil, two-dimensional stationary blade row and three-dimensional rotating blade row were calculated, and the numerical results were compared with experimental ones. The numerical technique was based on the SIMPLE algorithm using three turbulent closure models, standard k-.epsilon. model(WFM), low Reynolds number k-.epsilon. model(LRN) and Reynolds stress model (RSM). In the case of a single airfoil, WFM, LRN and RSM presented fairly good velocity distributions in the wake compared with experimental data. In the case of the stationary blade row, LRN and RSM presented better results than WFM for wake velocity distribution, and especially LRN showed best results among these three turbulent models. In the case of the rotating blade row, WFM and LRN showed fairly good agreement with experimental data of the three-dimensional velocity component distributions in the range from hub to mid span region. LRN was also superior to WFM in accuracy of prediction for the wake velocity distribution as same with the cases of a airfoil and the stationary blade row.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1845-1852
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• 2001

This paper deals with the experiment to obtain quantitative information about conditions of the interface between a water drop and surrounding oil. Velocity distributions in very close region of the interface are measured by introducing a new illumination technique and a telecentric lens. It enables precise measurements of velocity distributions in the close region to the interface. Although the measured velocity distributions exhibit strong influence from the solid wall of an experimental tube, the coincidence of inner and outside velocities on the interface is clearly confirmed for the clean interface. The shearing stresses on the interface, which are proportional to the velocity gradient normal to the interface, clearly show conditions of contaminated interface, which can be divided into two parts. From front stagnation point to somewhere near a separation point, the distribution of shearing stresses is well coincide with that of the Hadamard's analytical solution, while the distribution on the latter part of the interface sows quite different feature, which is supposed to be strongly influenced by contamination of the surface.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.1-10
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• 1998

A header is the device that makes uniform flow distribution in all branches from header of heat exchangers, pipe burner or chemical equipments. In this study, experimental tests have been performed in order to investigate the flow distribution characteristics in a straight header and tapered header which have 6 and 11 glass pipe branches. The experimental equipment consists of a water circulation system where the fluid velocity in each glass pipe is measured by Ar-ion LDV system. From the experiments and the theoretical equation, it could be recommended that tapered header should be determined so that its internal velocities inside the header become uniform according to taper of the header and number of attached branches for uniform flow distribution in energy systems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.662-669
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• 1994

In the combustion system, the optimum spray conditions reduce the pollutant emission of exhaust gas and enhance the fuel efficiency. The spray characteristics-the drop size, the drop velocity, the number density and the mass flux, become increasingly important in the design of combustor and in testifying numerical simulation of spray flow in the combustor. The purposes of this study are to clarify the spray characteristics of twin-fluid nozzle and to offer the data for combustor design and the numerical simulation of a spray flow. Spatial drop diameter was measured by immersion sampling method. The mean diameter, size distribution and uniformity of drop were analyzed with variations of air/liquid mass flow ratio. The results show that the SMD increases with the liquid supply flow rate and decreases with the air supply velocity. The radial distribution of SMD shows the larger drops can diffuse farther to the boundary of spray. And the drop size range is found to be wider close to the spray boundary where the maximum SMD locates.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.877-884
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• 2004

In this paper, structural analysis is performed to investigate the deformation of porous media in a proton exchange membrane fuel cell (PEMFC). Structural deformation of air plate of the fuel cell causes the change in configuration and cross sectional area of the channel. The distributions of mass flow rate and pressure are major factors to decide the performance of a PEMFC. These factors are affected by channel configuration of air plate. Two kinds of numerical air plate models are suggested for flow analyses. Deformed porous media and undeformed porous media are considered for the two models. The Numerical flow analysis results between deformed porous media and undeformed porous media have some discrepancy in pressure distribution. The pressure and velocity distribution under a working condition are numerically calculated to predict the performance of the air plates. Pressure and velocity distributions are compared for two models. It is shown that structural deformation makes difference in flow analysis results.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.5
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• pp.648-656
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• 2003

An experimental research was performed to study turbulent flow characteristic in a $90^{\circ}$ circular bend by using the PIV(Particle Image Velocimetry) method, this study found the time-mean velocity distribution, time-mean turbulent intensity with turbulent flow for Re = 10,000, 15,000, 20,000, and 25,000 along the test bend. It was found that the highest streamwise velocity of turbulent flow occurs near y/D = 0.5 and the flow moved to y/D =0.15. The peak turbulence intensity shifted toward the concave wall from $\theta= 45 and as \theta$ increased. the intensity decayed along the test tube.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.264-271
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• 1999

The present experimental study is aimed to investigate the flow characteristics of the high-speed flow field within hot-water pump by PIV(Particle Image Velocimetry). As multi-point simultaneous velocity acquisition, 2-D PIV system based upon the two-frame gray-level cross correlation method is adopted using PC frame-grabber and simple video system. Gated image intensifier CCD Camera to cope with illumination problem is arranged for accurate PIV measurement of high-speed complex flow. The velocity vector distribution, velocity profile, and kinetic energy are represented quantitatively at the full-scale region for the deeper understanding of the unsteady flow characteristics in a pump.