• Journal of ILASS-Korea
• /
• v.16 no.3
• /
• pp.140-145
• /
• 2011

Gelled propellants are non-Newtonian fluids in which the viscosity is a function of the shear rate, and they have a high dynamic shear viscosity which depends on the amount of gelling agent contents. The present study has focused on the breakup process, wave development of ligament and liquid sheets formed by impinging jets with various gelling agent contents. The breakup process of like-on-like doublet impinging jets are experimentally characterized using non-Newtonian liquids. The spray shape with elliptical pattern is distributed in a perpendicular direction to the momentum vectors of the jets. Gelled propellant simulants with high viscosity jets are more stable and produce less pronounced surface waves than low viscosity jets. Gelled propellant simulants from like-on-like doublet impinging jets have the spray shape of closed rim patterns at low pressure. As the injection pressure increased, rimless patterns which were composed of ligament sheets and small droplets emerged due to the effect of the aerodynamic action.

• Journal of ILASS-Korea
• /
• v.17 no.1
• /
• pp.35-44
• /
• 2012

To improve the mixing and atomizing performance at the center region of the conventional coaxial shear injector spray, the concept of a coaxial porous injector was invented. This novel injection concept for liquid rocket engines utilizes the Taylor-Culick flow in the cylindrical porous tube. The 2-dimensional injector, which can be converted in three injection configurations, was fabricated, and several cold flow tests using water-air simulant propellant was performed. The hydraulic characteristics and the effects of a gas flow condition on the spray pattern and the Sauter mean diameter (SMD) was analyzed for each configuration. The atomizing mechanism of coaxial porous injector was different with the coaxial shear injector, and it was explained by the momentum of the gas jet, which is injected normally against the center liquid column, and by the secondary disintegration at the wavy interface of liquid jet, which was generated at the recessed region. The SMD of 2D coaxial porous injector, which has higher gas momentum, was measured and it shows better atomizing performance at the center and outer side of spray than the 2D coaxial shear injector.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.11 no.5
• /
• pp.50-59
• /
• 2003

It was known that high pressure injection is an effective method to enhance thermal efficiency and decrease exhaust emissions in diesel engines. If injection pressure becomes ultra high, it is predicted that there may be a suitable injection pressure which the enhancement rate of spray characteristics is moderate. Also, there may be a limit injection pressure which spray characteristics is reversed and get worse. But these are unknown. To investigate a suitable injection pressure and a limit injection pressure, ultra high pressure injection equipment(UHPIE), which can realize the injection pressure of 3,200bar, was developed. UHPIE is a basic apparatus of single shot injection, and ultra high pressure was achieved by second stage rapid compression in short time. From the evaluation of UHPIE, a injection curve like a conventional diesel engine(jerk type) was realized. Also, it was proved that repetition of experiment was excellent. Therefore it was found that there was no problem to perform the study on the ultra high pressure injection with UHPIE. Consequently, the foundation of the study on ultra high pressure injection could be established.

• Korean Journal of Agricultural Science
• /
• v.7 no.2
• /
• pp.156-168
• /
• 1980

The air-center nozzles, being specially designed to supply air into the central part of water stream at seven levels of air volume, were tested for spray deposit pattern and flow-rate at each of the twelve pressure levels ranging from $0.35kg/cm^2$ (5 psi) to $6.33kg/cm^2$ (90 psi) in comparison with those of standard nozzles. The air-center nozzles produced comparatively more stable spray deposit patterns than the standard nozzles. The spray deposit patterns of the air-center nozzle were concentrated gradually in the central region with increase of air volume as a component of spray mixture. The degree of concentration of spray deposit on the central region from the air-center nozzle was higher than that of the standard nozzle, which suggested the possibility of obtaining farther travel distance spraying system at a given performance level. The flow rate of the air-center nozzle was not as much as that of the standard nozzle due to the air within certain limits. The rate of decrease of water flow became smaller with an increase in operating pressure although it changed rapidly in the beginning stage, ranging up to two or three percent of the air flow rate due to the compressive properties of air.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.11-14
• /
• 2009

The implementation of gelled propellants systems offers high performance, thrust-control, energy management of propulsion, storability, and high density impulse of solid propulsion. Present study focused on the spray behavior of liquid sheets formed by impinging jets of non-Newtonian liquids which are mixed by Carbopol 941 0.5%wt. The results are then compared with experiments conducted on spray images formed by impinging jets concerning with air-blast effect at center orifice. When gel propellants are injected by doublet impinging jets at low pressure, closed rim pattern shape appeared. As increasing air mass flow rate(decreasing GLR), spray breakup and atomization phenomenon better improved and spray structure instabilities for the effect of air-blast are also increased.

• Journal of Pharmaceutical Investigation
• /
• v.31 no.4
• /
• pp.241-256
• /
• 2001

Alginate microspheres, containing fluorescein isothiocyanate-bovine serum albumin (FITC-BSA) or green fluorescent protein (GFP) were prepared and used as a model drug to develop the oral vaccine delivery system. The alginate microspheres were coated with poly-L-lysine or chitosan. Two methods, w/o-emulsion and spray, were used to prepare alginate microspheres. To optimize preparation conditions, effects of several factors on the particle size and particle morphology of microsphere, and loading efficiency of model antigen were investigated. In both preparation methods, the particle size and the loading efficiency were enhanced when the concentration of sodium alginate increased. In the w/o-emulsion preparation method, as the concentration of Span 80 was increased from 0.5% to 2%, the particle size was decreased, but the loading efficiency was increased. The higher the emulsification speed was, the smaller the particle size and loading efficiency were. The concentration of calcium chloride did not show any effect on the particle size and loading efficiency. In the spray preparation method, the particle size was increased as the nozzle pressure $(from\;1\;kgf/m^2\;to\;3\;kgf/m^2)$ and spray rate was raised. Increasing calcium chloride concentration (<7%) decreased the particle size, in contrast to no effect of calcium chloride concentration on the w/o-emulsion preparation method. Alginate microspheres prepared by two methods were different in the particle size and loading efficiency, the particle size of microspheres prepared by the spray method was about $2-6\;{\mu}m$, larger than that prepared by the w/o emulsion method $(about\;2{\mu}m)$, and the loading efficiency was also higher with spray method. Furthermore, drying process for the microspheres prepared by the spray was simpler and easier, compared with the w/o emulsion preparation. Therefore, the spray method was chosen to prepare alginate microspheres for further experiments. Release pattern of FITC-BSA in alginate microspheres was evaluated in simulated intestinal fluid and PBS (phosphate buffered saline). Dissolution rate of FITC-BSA from alginate/chitosan microsphere was lower than that from alginate microsphere and alginate/poly-L-lysine microsphere. By confocal laser scanning microscope, it was revealed that alginate/FITC-poly-L-lysine microspheres were present in close apposition epithelium of the Peyer's patches of rabbits following inoculation into lumen of intestine, which proved that microspheres could be taken up by Peyer's patch. In conclusion, it is suggested that alginate microsphere prepared by spray method, showing a particle size of & $10\;{\mu}m$ and a high loading efficiency, can be used as a model drug for the development of oral vaccine delivery system.

• Fire Science and Engineering
• /
• v.26 no.2
• /
• pp.1-10
• /
• 2012

While a performance based sprinkler design method has been widely used in UK and USA according to fire hazards of occupancies, Korean fire safety industry could not yet accept it due to nonstandardization on risk level of various occupancy. Even only two or three spray pattern sprinkler was produced in Korea fire safety industry, therefore, various spray pattern sprinklers have not yet introduced to major occupancies. Spray pattern sprinklers with one of two K value have been used in all occupancies in Korea Market. UK and USA's Fire industry should produced the spray sprinklers with various K-factors and protection area due to performance based sprinkler design requirement. Therefore the fire load density for main occupancies has been investigated in order to compare with installation standard in advanced countries. Eventually a lot of variations in orifice and K factors of standard heads were set up including special heads needed for high hazard areas such as large drop type, enlarged orifice type and early suppression fast response.

• Journal of the Korea Fashion and Costume Design Association
• /
• v.14 no.3
• /
• pp.1-10
• /
• 2012

This study has purpose to understanding recent trends and image effect of textile in fashion by looking to dyeing technique and aesthetics of diffusing image pattern. Further the study will hope to provide basic data for fashion and textile designer fashion. The methods of this study are academic literatures as well as practical study through case studies about actual works. Dyeing techniques and aesthetics of diffusing image pattern since 2000 fashion collection and their results are as follows. First, Dyeing techniques of diffusing image pattern are wet-dyeing and printing. There are plangi dyeing, salt dyeing, alcohol dyeing and ikat dyeing in the wet-dyeing and spray dyeing, discharge dyeing in the printing. There are tie-dyeing, rumpling-dyeing and plank-dyeing in the plangi. Second, Forming of the diffusing image pattern are due to uneven seeping and the contingency of a chemical reaction by reducing the pressure and intensity. Third, Aesthetics of diffusing image pattern are extracted purity missing childhood, fantasy escaping facts of the situation and abstraction representing informal world from formative characteristics of diffusing image pattern.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.5
• /
• pp.1121-1129
• /
• 1988

An economic and efficient system for measuring drop sizes was developed. Pattern recognition technique was used with conventional oil-bath sampling and photographic method. The system was designed to measure and count relatively large number of drops in a very short time, and also to filter out abnormal images such as drops in contact or overlap as well as odd-shaped foreign materials. In this measuring system, most important error originates from the process of converting the original image to the binary image. If the photograph contains a large number of spray drops, the relative size of the pixel to the drops is not infinitesimally small; thus the proper choice of threshold level to convert the original image to the binary image becomes very important. In present case, most of the images lay in one of the two separate bands of brightness level and the arithmetic mean of the most popular brightness levels from each band was chosen as the threshold level. Present image processing system reduces the subjective error by the observers in counting and measuring drops and turns out to be substantially effective. The processing time can be further reduced by improving the hardware system concerned with the digital image coding.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.11
• /
• pp.727-730
• /
• 2015

In this paper, we fabricated organic compounds detector using the MWCNT/PMMA (multi-walled carbon nanotube / polymethylmethacrylate) composite film. We used polymer film as a matrix material for the device framework, and introduced CNTs for reacting with the organic compounds resulting in changing electrical conductivity. Spray coating method was used to form the MWCNT/PMMA composite film detector, and pattern formation of the detector was done by shadow mask during the spray coating process. We investigated changes of electrical conductivity of the detector before and after the organic compounds exposure. Electrical conductivity of the detector tended to decrease after the exposure with various organic compounds such as acetone, tetrahydrofuran (THF), toluene, and dimethylformamide (DMF). Finally we conclude that organic compounds detection by the MWCNT/PMMA composite film detector was possible, and expect the feasibility of commercial MWCNT/PMMA composite film detector for various organic compounds.