• Journal of ILASS-Korea
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• v.25 no.2
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• pp.60-67
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• 2020

Despite its benefit in engine thermal efficiency, gasoline-direct-injection (GDI) engines generate substantial particulate matter (PM) emissions compared to conventional port-fuel-injection (PFI) engines. One of the reasons for this is that the spray collapse caused by the spray-to-spray interaction forms the locally rich fuel-air mixture and increases the fuel wall film. Previous studies have investigated the spray collapse phenomenon through the macroscopic observation of spray behavior using laser optical techniques, but it is somewhat difficult to understand the interaction between sprays that is initiated in the near-nozzle region within 10 mm from the nozzle exit. In this study, the spray structure, droplet size and velocity data were obtained using an X-ray imaging technique from the near-nozzle to the downstream of the spray to investigate the spray-to-spray interaction and discuss the effects of spray collapse on local droplet size and velocity distribution. It was found that as the ambient density increases, the spray collapse was promoted due to the intensified spray-to-spray interaction, thereby increasing the local droplet size and velocity from the near-nozzle region as a result of droplet collision/coalescence.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.37-44
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• 2002

A theoretical study of spray and combustion characteristics due to coaxial twin-fluid injection is conducted to investigate the effects of liquid jet property, droplet size, contact length and liquid jet velocity. Model is properly validated with measurements and shows good agreement. Prediction of jet contact length, droplet size, liquid jet velocity reflects genuine features of coaxial injection in physical and practical aspects. Both the jet contact length and tile droplet size are reduced in a linear manner with an increase of injector diameter. Cross sectional area of liquid intact core is reduced with augmented jet splitting rate, thus the jet is accelerated to maintain the mass continuity and with an assistant of momentum diffusion by burnt gas.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.419-429
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• 2016

In a bid to avoid the economic loss resulting from traffic jam in urban area, a deep underground road at 40 m depth has been considered and the first class disaster prevention facilities shall be applied according to domestic guideline. Automatic-monitoring fire extinguishing system designed to use for fire fighting has been widely applied at home and abroad. Recently development and commercialization through theoretical and experimental research to apply to road/railroad sector have been underway. Based on such performance of automatic fire extinguishing system, technical/economic analysis of existing water spray systems was conducted and as a result, it has demonstrated the superiority in terms of fire suppression as well as in cost efficiency. Then to commercialize this system, more diverse studies that will incorporate the characteristics of domestic tunnels are needed and should the system be promoted through institutional improvement, it's expected to become one of the advanced nations with own original technology in a life safety system industry throughout the world.

• Journal of Conservation Science
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• v.29 no.3
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• pp.249-259
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• 2013

This study was experimented on accelerated weathering test using salt and freeze-thaw to prove effects of consolidants and consolidation for stone cultural heritage. The samples used four kinds of stones (Gyeongju Namsan Granite, Iksan Granite, Yeongyang Sandstone and Jeongseon Marble) which to distributed by three type of weathering grade (Fresh, Weathered Stone and Highly Weathered Stone) added for thermal treatment. The samples were treated with three consolidants (Wacker OH 100, Remmers KSE 300 and 1T1G), and tested by 500 cycles with freezing-thawing and 50 cycles of salt weathering test. As a results of freezing-thawing test, the crack and destruction occurred from some samples. And total immersed samples maintained effect of consolidation to 200 cycles. Also, The rock particle was fall off and gradually destructed by salts weathering test. The consolidated sample relatively had fewer changes by the weathering than not treated sample. The sprayed sample had not continuous effect on weathering.

• Korean Journal of Food Science and Technology
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• v.23 no.2
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• pp.235-240
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• 1991

Starch phosphates were prepared from the corn starch mixed with 2% sodium tripolyphosphate by twin-screw extruder with a feed rate of 20 kg/hr and an extrusion temperature of $130^{\circ}C$, and the effects of extrusion variables on the physicochemical properties (target parameters) of starch phosphates were investigated. Interrelations of system parameters (specific mechanical energy and extrudate moisture) and rheological properities of starch was analyzed by using the response surface analysis. Degree of substitution (DS) was increased with increasing the feed moisture, and showed the maximum value at the screw of near 250 rpm, Degree of gelatinization was proportionally increased with increasing the screw speed and decreasing the feed moisture. Apparent viscosity of the paste was increased with increasing the feed moisture, but it was not significantly affected by the screw speed. It was found by scanning electron microscopy that the starch microgranules were much more degradaded, and as consequent result, the intrinsic viscosity was decreased, whereas, water solubility index was increased. The rate of retrogradation of the gels was retarded with increasing DS and decreasing viscosity.

• Food Engineering Progress
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• v.21 no.3
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• pp.267-272
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• 2017

To improve dispersibility of cereal powder without additives, granulation of cereal powder was conducted using fluidized-bed granulator. Operation condition was sample 300 g, internal temperature $40^{\circ}C$, ventilation speed $30-90m^3/h$, inlet temperature $90^{\circ}C$ and spray pressure 2.5 bar. The amount of distilled water (20-45%) as binder, granulation time (10-15 min) and drying time (3-10 min) were controlled. Mean diameter over volume (Brouckere mean, $D_{4,3}$) was increased from $123{\mu}m$ to $263{\mu}m$ and dispersibility was improved from 73% to 92.25% at experiment conditions. Wettability (wetting time) was drastically decreased from 5,000 second to 7 second. Granulation of cereal powder did not affect sinkability and mean diameter over volume as wet analysis was about the same between raw and granulated cereals. Such phenomenon means that granulation with only water as binder enables cereal powder to disperse in water or milk without rapid sedimentation.