• Particle and aerosol research
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• v.13 no.1
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• pp.25-31
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• 2017

This paper offer the characteristics for the detection and classification of biological and non-biological aerosol particles in the air by using laser-induced-fluorescence (LIF) based Bio-aerosol Detection System (BDS). The BDS is mainly consist of an optical chamber, in-outlet nozzle system, 405 nm diode laser, an avalanche photo detector (APD) for scattering signal and photomultiplier tubes (PMT) for fluorescence signals in two different wavelength range ; F1, 510-600 nm and F2, 435-470 nm. The detection characteristics, especially ratio of fluorescence signal intensity were examined using well-known components : polystylene latex (PSL), fluorescence PSL, $2{\mu}m$ of SiO2 micro sphere, dried yeast, NADH, ovalbumin, fungicide powder and standard dust. The results indicated that the 405 nm diode laser-based LIF instrument can be a useful bio-aerosol detection system for unexpected biological threaten alter in real-time to apply for dual-use technology in military and civilian fields.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.4
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• pp.49-62
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• 1993

It has been a principle research topic on the diesel engine development to increase the efficiency and the performance of engine to satisfy the user's needs for high reliability and durability. However, recently with the worldwide concerns at the global climate change and environmental protection, the main target in the diesel engine research has been changed to solve the exhaust emission problem in order to satisfy the strict emission regulations. To reduce the pollutant for the diesel engine, the researchs on the combustion chamber is the most important and has to be performed first of all. The diesel fuel injection system plays major role to air-fuel mixing process and influences engine output, themal efficiency, reliability, noise, and emissions. The experimental studies were conducted by varying the various parametric conditions and the results were campared with the computation and calculated results by using the fuel injection simulation program developed during previous research. From the experiments, the matching technique of a fuel injection pump and nozzle was conducted to understand under the various parametric conditions. Also, the relations between needle lift and wave propagation characteristics in high pressure pipe were examined. The basic design data from the experimentations and computation works would be applied to actual design works of diesel fuel injection system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.337-344
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• 2011

The humidification of reactant gases is crucial for efficiently operating PEM (polymer electrolyte membrane) fuel cell systems and for improving the durability of these systems. The recycle of the energy and water vapor of exhaust gas improves the system performance especially in the case of automotive application. The available humidification methods are steam injection, nozzle spray, humidification by enthalpy wheel, membrane humidifier, etc. However, these methods do not satisfy certain requirements such as compact design, efficient operation and control. In this study, a hybrid humidification system consisting of a membrane humidifier and exhaust-air recirculation units was developed and the humidification performance of this hybrid humidifier was analyzed. Finally, a new practical method for optimal design of PEM-fuel-cell humidification system is proposed.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.63-75
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• 1996

The purpose of this study is to investigate the break-up characteristics by taking advantage of a two-phase coaxial nozzle. Air and water are utilized as working fluids and the mass ratio air/water has been controlled to characterize the atomization, diffusion and development of mixing process. By way of a photographic technique, conventional developing structures and diffusion angles have been analyzed systematically with variations of mass ratios. The turbulent flow components of the atomized particles were measured by a two channel LDV system and the data were treated by an on-lined measurement equipment. According to the photographic results the spreading angles decreased because the axial inertia moment was relatively higher than the lateral one with respect to the increase of mass ratio. It is found the jet flow diffuses linearly in a certain limit region while the atomizing characteristics, in terms of the distributions of particle diameters did not show particular differences. It may be expected that these fundamental results can be used as reference data in studying the atomization, breakup and diffusions.

• Journal of ILASS-Korea
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• v.11 no.3
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• pp.168-175
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• 2006

The static pressure distribution and flow characteristics inside the high-pressure swirl spray were investigated by measuring the static pressure inside the spray and applying the computational fluid dynamics (CFD). The static pressure difference between inner and outer part of spray was measured at different axial locations and operating conditions using a piezo-resislive pressure transducer. To obtain the qualitative value of swirl motion at different operating conditions, the spray impact-pressure at the nozzle exit was measured using a piezo-electric pressure transducer, and the flow angle was measured using a microscopic imaging system. The flow characteristics inside the high pressure swirl spray was simulated by the 1-phase 3-dimensional CFD model. The effect of pressure alternations on spray development was discussed with macroscopic spray images and a mathematical liquid film model. The results showed that the static pressure drop is observed inside the swirl spray as a result of the dragged air motion and the centrifugal force of the air. The recirculation vortex inside the spray was also observed inside the swirl spray as a result of the adverse pressure gradient along the axial locations. The results of analytical liquid film model and macroscopic spray images showed that the static pressure structure is one of the main parameters affecting the swirl spray development.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1236-1242
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• 2006

The local heat flux of spray cooling in the film boiling region were experimentally investigated for the spray region of $D_{max}$ = $0.005{\sim}0.03m^3/(m^2s)$. A twin-fluid full cone spray nozzle was employed for the experiment and the distributions of droplet flow rates were obtained for air-water full cone sprays. A stainless steel block was cooled down from initial temperature of about $800^{\circ}C$ by full cone spray. In the region near the stagnation point, it was found that the experimental data are in good agreement with the results predicted from the correlations between the local heat transfer and the local droplet flow rate proposed in the previous report. However, it was found that the experimental data of $D_r$ > $0.01m^3/(m^2s)$ are a little smaller than the results predicted from the correlations.

• Environmental Engineering Research
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• v.24 no.4
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• pp.600-607
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• 2019

Volatile organic compounds (VOCs) are released from various sources and are unsafe for human health. Porous materials are promising candidates for the adsorption of VOCs owing to their increased ratio of surface area to volume. In this study, activated carbon (AC) impregnated cellulose acetate (CA) electrospun mats were synthesized using electrospinning for the removal of VOCs from the air mixture of ACs, and CA solution was electrospun at different proportions (5%, 10%, and 15%) in a single nozzle system. The different AC amounts in the electrospun mats were distributed within the AC fibers. The adsorption capacities were measured for acetone, benzene, and dichloromethane, using quartz crystal microbalance. The results elicited an increasing adsorption capacity trend as a function of the impregnation of ACs in the electrospun mats, while their capacities increased as a function of the AC concentration. Dichloromethane resulted in a faster adsorption process than acetone and benzene owing to its smaller molecular size. VOCs were desorbed with the N₂ gas purging, while VOCs were adsorbed at higher temperatures owing to the increased vapor pressures. The adsorption analysis using Dubinin-Astakhov equation showed that dichloromethane is more strongly adsorbed on mats.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.37-46
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• 2006

The outside environment is very severe while aircraft is cruising. Especially small particle of icing in cold air condition can have negative influence on aircraft performance. If ice particle is attached to leading edge of wing, it can change wing configuration and decrease flight quality. If icing particle is attached to inlet of engine, it can damage compressor blade and have negative influence to aircraft safety. We make icing simulation device with liquid air system for analyzing about variation of engine performance due to incoming of icing to engine.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.12 no.4
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• pp.264-274
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• 1983

Two-dimensional jet flows into a couple of confined rectangular enclosures such as an Ondol flue channel and their flow distributions were analyzed by numerical graphics : rectangular space in one enclosure is vacated and the other has 8 rectangular small posts. Both enclosures have a protruded inlet nozzle and on outlet on its center line. Steady state incompressible laminar viscous flow was assumed. The primitive forms of Navier-Stokes equations and continuity equation in a cartesian coordinate system were solved numerically by the Marker and Cell method for Reynolds numbers of 5, 10, 20, 30 and 40. From the numerical graphics it was found that the flow regions in both enclosures were devided into tow parts ; one part was the jet flow localized in a narrow center region of the enclosure and the other part was the very slow recirculating flow occupying the rest of the flow region in the enclosures. However there were a little differences in the shapes of jet flow in both enclosures for Reynolds numbers of 5 and 10 and also in the shapes of recirculating flows in both enclosures for all Reynolds number. Also it was found that waving flow appeared right before the outlet at Reynolds number of 20 and more.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.413-418
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• 2016

Recently, a mega project such as Korea-China or Korea-Japan undersea tunnel project has been emerged for detail discussion and the interest in undersea tunnel is on the rise. More severe damage by train fire is expected in undersea tunnel comparing to ground tunnel and thus the study on more efficient fire extinguishing system, besides existing disaster prevention design is underway. To that end, a full-scale fire tests using CAF fire extinguishing system which has been developed by modifying traditional foam fire extinguishing system for fire suppression at rescue station in timely manner were conducted over 7 times. The test was conducted after setting the rescue station in virtual tunnel with a car of KTX. As a result of using compressed air foam directly to the fire source, 30 liter of Heptane combustibles was extinguished within 1 minutes. Applicability of compressed air foam to train fire at rescue station in undersea tunnel was has been proven and further study is considered required while changing the nozzle angle and location so as to achieve quick and easy extinguishing goal, making use of the advantage of CAF, as well as to reduce the fire water and chemicals required.