• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.24-29
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• 1998

An experimental study was carried out to investigate the characteristics of spray pattern such as discharge coefficient, spray angle, and mass distribution for two-fluid airblast swirl injector, within the range of fluid supply pressure 0~13kg/$\textrm{cm}^2$. In general atomization is promoted with increasing total gas mass flow and performance of the splay pattern was more stable when radial mass flow was greater than axial mass flow, radial swirler was better than Axial swirler for atomization. Equivalent spray angle did not change with water mass flow except for the condition of 3kg/$\textrm{cm}^2$ and showed the same for the gas mass flow. Mass distribution from the patternator shows that maximum value of the distribution were lowered but distributed larger area when gas flow rate increased. Center of mass position did not change with increasing water mass flow.

• Journal of Sensor Science and Technology
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• v.20 no.3
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• pp.151-155
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• 2011

A variety of pattern recognition algorithms including neural networks may be applicable to the identification of odors. In this paper, an identification technique for an electronic odor sensing system applicable to wound state monitoring is presented. The performance of the radial basis function(RBF) network is highly dependent on the choice of centers and widths in basis function. For the fine tuning of centers and widths, those parameters are initialized by an ill-conditioned genetic fuzzy c-means algorithm, and the distribution of input patterns in the very first stage, the stochastic gradient(SG), is adapted. The adaptive RBF network with singular value decomposition(SVD), which provides additional adaptation capabilities to the RBF network, is used to process data from array-based gas sensors for early detection of wound infection in burn patients. The primary results indicate that infected patients can be distinguished from uninfected patients.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1671-1678
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• 1996

In external chemical vapor deposition processes including VAD and OVD the distribution of flame-synthesized silica particles is determined by heat and mass transfer limitations to particle formation. Combustion gas flow velocities are such that the particle diffusion time scale is longer than that of gas flow convection in the zone of particle formation. The consequence of these effects is that the particles formed tend to remain along straight smooth flow stream lines. Silica particles are formed due to oxidation and hydrolysis. In the hydrolysis, the particles are formed in diffuse bands and particle formation thus requires the diffusion of SiCl$\_$4/ toward CH$\_$4//O$\_$2/ combustion zone to react with H$\_$2/O diffusing away from these same zones on the torch face. The conversion kinetics of hydrolysis is fast compared to diffusion and the rate of conversion is thus diffusion-limited. In the language of combustion, the hydrolysis occurs as a Burke-Schumann process. In selected conditions, reaction zone shape and temperature distributions predicted by the Burke-Schumann analysis are introduced and compared with experimental data available. The calculated centerline temperatures inside the reaction zone agree well with the data, but the calculated values outside the reaction zone are a little higher than the data since the analysis does not consider diffusion in the axial direction and mixing of the combustion products with ambient air. The temperatures along the radial direction agree with the data near the centerline, but gradually diverge from the data as the distance is away from the centerline. This is caused by the convection in the radial direction, which is not considered in the analysis. Spatial distribution of silica particles are affected by convection and diffusion, resulting in a Gaussian form in the radial direction.

• 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 B
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• v.27 no.9
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• pp.1299-1308
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• 2003

This paper is studied to investigate the effect of slits and swirl vanes on the development of turbulent flow fields in gun-type gas burner with a cone type baffle plate because this gas burner is generally composed of eight slits and swirl vanes. All of turbulent characteristics including mean velocities were measured in the horizontal plane and cross section by using X-type hot-wire probe from hot-wire anemometer system. This experiment is carried out at flow rate 450 l/min in the test section of subsonic wind tunnel. Slits cause the fast jets, and then they have the characteristic that the flow is not adequately spread to radial direction and has long flow length and very small flow velocity distribution in the central part. On the contrary, swirl vanes does not have long enough for adequate flow length to downstream because the rotational flow diffuses remarkably to radial direction. However, the suitable arrangement between slits and swirl vanes causes effective flow width and flow length, and then it promotes fast flow mixing over the entire region including central part to increase turbulence more largely and effectively. Therefore, it is thought as a very desirable design method in gun-type gas burner to locate slits on the outside of swirl vanes.

• Journal of Radiation Protection and Research
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• v.29 no.1
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• pp.25-31
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• 2004

Results of EGS4 based calculations to study the spatial resolution of gas detectors are described. The calculations include radial distribution of electrons generated by photons of various energies penetrating into variable thickness of Ar and Xe gas layers. Given a desired spatial resolution, the maximum allowed thickness of gas layer for each energy level is determined. In order to obtain 0.1mm spatial resolution, the maximum thickness for the Ar gas is found to be 2mm for photon energies below 14keV while the optimum energy of photons for Xe gas with the same thickness is about 45keV. The results of calculations performed to compare the number of electrons generated by CsI coated micro-channel plate and the number of electrons generated by the Ar and Xe gas layers are described. The results show that the number of electrons generated by the gases is about 10 times higher than the one generated by CsI coated micro-channel plate. A few sample gray scale images generated by these calculations are included.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.7
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• pp.997-1004
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• 2001

Burner of Flat Flame type expects the uniform flame distribution and NOx reduction. The characteristics of Flat Flame Burner become different according to swirl number in the burner throat. Experiments were focused on swirl effect by four types of swirler with different swirl numbers (0, 0.26, 0.6 and 1.24). It shows many different flow patterns according to swirl number using PIV(Particle Image Velocimetry) method. The flow of burner with swirler is recirculated by pressure difference between its center and outside. Recirculated air makes stable in flame, and reduced pollutant gas. In case of swirl number 0, main flow passes through axial direction. As swirl number increased, The backward flow develops in the center part of burner and Flow gas recirculates. This is caused by radial flow momentum becomes larger than axial flow by swirled air and the pressure at center drops against surrounding. As swirl number increases, the radial and axial velocity was confirmed to be larger than low swirl numbers. And turbulence intensity have similar pattern. The CTRZ(Central Toroidal Recirculation Zone) is shown evidently when y/D=1 and S=1.24. The boundary-layer between main flow and recirculated flow is shown that the width is seen to be decreased as swirl number increased.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.225-231
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• 2004

Scroll compressor has been used extensively for refrigeration since the early 1980's for its improved efficiency, greater reliability, smoother operation, lower noise and vibration. And also, nowadays, the scroll mechanism is used for expander even though in niche market yet. But scroll expander has not been used for high-temperature and high-pressure gas, because the continuous expansion of the gas causes a wide range of temperature distribution over the whole scroll wrap that leads to differential thermal expansion of scroll elements, which results in system vibrations, noise and efficiency losses. For the scroll expander to produce power more efficiently, all of radial and radial clearances between scroll wrap must be the same. In order to reduce differential thermal expansion in addition to improvements in thermal efficiency and specific power, we propose a scroll expander with heating structure. Heat-pipe heating structure is considered as the most effective method to heat the scroll expander at a uniform temperature. This paper includes some results of preliminary study of the scroll expander with heating structure and proposals of their systems for power generation and refrigeration.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.19-20
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• 2003

Brownian-dynamics simulation on highly charged colloidal suspensions is performed by employing Tokuyama effective force recently proposed. The radial distribution function suggests that there exist three novel phases, a gas phase, a liquid droplet phase, and a face-centered cubic (FCC) crystal droplet phase, depending on the minimum values of that potential. The dynamics of droplet growth is also investigated both in liquid droplet phase and in crystal droplet phase. Thus, different types of characteristic growth stages are found.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.143-148
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• 2004

The numerical analysis of the hard disk drive slider is presented. The pressure distribution was calculated using the finite element method. The generalized Reynolds equation was applied in order to include the gas rarefaction effect. The balance of the air bearing force and preload force was considered. The characteristics of the small vibrations near the equilibrium were studied using the perturbation method. Triangular mesh with variable element size was employed to model the two-rail slider. The flying height, pitching angle, rolling angle, stiffness and damping of the two-rail slider were calculated for radial position changing from the inner radius to the outer radius and for a wide range of the slider crown values. It was found that the flying height, pitching angle and rolling angle were increased with radial position while the stiffness and damping coefficients were decreased. The higher values of crown resulted in increased flying height, pitching angle and damping and decreased stiffness.