• Journal of ILASS-Korea
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• v.26 no.1
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• pp.33-39
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• 2021

Y-jet nozzle has a wide fuel flow rate range and turn-down ratio, thus, it is used in industrial boilers, furnace and agricultural atomizer. However, it has asymmetrical spray characteristics due to the nozzle design factors. Therefore, in this study, asymmetric spraying characteristics of the elliptical Y-jet nozzle was studied by using the lab-scale spray apparatus. As a result, the elliptical Y-jet nozzle had lower gas mass flow rate than circular Y-jet nozzle at same gas pressure, because of bigger shear stress due to the wider inner surface at the elliptical Y-jet nozzle. Larger SMD was measured on the elliptical Y-jet nozzle than the circular Y-jet nozzle. When SMD was measured in the X_Axis direction at the same gas mass flow rate, the elliptical Y-jet nozzle with an aspect ratio of 2:1 showed greater asymmetry than the others.

• Journal of Drive and Control
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• v.17 no.4
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• pp.1-7
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• 2020

In orchard or crop-growing environments, pesticides are sprayed using various nozzles to prevent pests and improve productivity. Nozzles currently in use are restricted for use in multi-purpose environments, thus, it is necessary to develop new nozzles. In this study, new two-phase nozzles are proposed to improve the performance of the nozzle (flow rate, spray angle, spray particle size). The performance of the two-phase nozzles are predicted through the CFD analysis and the performance of the nozzles is compared with the experiment. The experimental results showed that the proposed two-phase nozzles are available at relatively low operating pressure condition and are capable of extensive spray particle size control. Thus, the proposed nozzles are expected to be available in various orchard environments.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.503-516
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• 2021

Autonomous fire detection and suppression system requires advanced technology for complex detection technology and injection/control technology for accurate hitting by fire location. Also, foam spraying should be included to respond to oil fires. However, when a single spray monitor is used in common, water and foam spray properties appear different, so for accurate fire suppression, research on the spray trajectory and distance will be required. In this study, experimental studies and numerical analysis studies were combined to analyze the foam spray characteristics through the spray monitor developed for the establishment of an autonomous fire extinguishing system. For flow analysis of foam injection, modeling was performed using OpenFOAM analysis software, and the commonly used foaming agent (Aqueous Film-Forming Foam) was applied for foam properties. The injection distance analysis was performed according to the injection pressure and the injection angle according to the form of the foam, and at the same time, the results were verified and presented through the injection experiment.

• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.1
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• pp.10-19
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• 2011

In order to predict the risk of anthracnose on hot pepper in the future, the projected climate data from SRES A1B scenario in South Korea were used with the modified anthracnose model to calculate Infection Risk (IR), which was to estimate the number of fungicide sprays. Based on daily temperature and precipitation, the anthracnose model resulted in an empirical relationship that IR = (Daily temperature - $16^{\circ}C$) ${\times}$ 0.07 + (Daily precipitation ${\times}$ 0.11). For 135 locations in South Korea, the total number of fungicide sprays needed from 2011 to 2100 was 12,150, indicating a complicated change with an overall increase in anthracnose development in all locations until 2100. In particular, radical changes in anthracnose development were predicted at Yeongdeok, Yeongyang, and Uiseong, whereas gradual changes were predicted at Heongsung, Hamyang and Taean. The eastern counties of Gyeongbuk Province, which ar the major plantation area in these days, would be the place with the highest disease pressure in the future. In addition, the years of 2058, 61, 78 and 2096 will be most severe, requiring 8-11 times of fungicide spraying. The GIS maps show that the mountain areas of Jeonbuk and Chungbuk Province would have the least disease pressure of anthracnose in the future.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.3
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• pp.186-192
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• 2023

According to the regulation on the pollution of the marine environment, SOx emission from ships has to be reduced. A SOx scrubbing system installed in a funnel of a ship is considered in order to reduce SOx emission. A scrubbing layer with a porous material is present in the funnel to increase the contact area between exhaust gas and water. In this study, experiments on the pressure drop characteristics in the scrubbing layer are conducted to investigate the effect of the scrubber on the engine load. The pressure drop according to flow rate of air instead of exhaust gas was measured for fillers such as sphere, pall ring and saddle in the scrubbing layer. First of all, porosity is experimentally measured for the three types of filler and it is confirmed that the porosity of the saddle-type filler was the largest. The pressure drop according to the change in air flow rate was measured for the three types of fillers in the scrubbing layer. As a result, the pressure drop was the smallest in the scrubbing layer with the saddle-type filler which has the largest porosity. In addition, the effect of spraying water flowing counter flow against air flow is experimentally examined. It is known that the pressure drop is increased because the air flow space is reduced when water is sprayed. In the case of the saddle, the pressure drop is about 1.5 to 2 times greater than that when only air flows at the optimum exhaust gas-water injection ratio.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.792-797
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• 2015

In this study, three softwood species were treated with water-soluble melamine resin by different concentration and treatment time under vacuum pressure for improving mechanical property, abrasion resistance, and incombustibility. After the treatment, a compreg was manufactured and then evaluated on physical properties. Additionally, incombustibility of compreg was determined by comparing with a wood that was treated by spraying a water-soluble fire retardant on surface. As concentration of resin increased, bending strength and Brinell hardness increased as well as abrasion resistance, but there was no correlation on treatment and mechanical properties by treatment time. The wood impregnated by water-soluble melamine resin under vacuum pressure showed better incombustibility than that of a water-soluble fire retardant sprayed wood. Therefore, this treatment could be used for improving incombustibility of wood.

• Progress in Superconductivity
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• v.8 no.1
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• pp.93-97
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• 2006

YBCO films were deposited on a moving substrate by a spray pyrolysis method using nitrate aqueous solution as precursors. Deposition was made on $LaAlO_3$(100) single crystal substrate by spraying precursor droplets generated by a concentric nozzle. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:4.5. The distance between nozzle and substrate was 15 cm. Substrate was transported with a speed ranging from 0.23 cm/min to 0.5 cm/min. Films were deposited at the pressure ranging from 10 Torr to 20 Torr and the deposition temperature was ranged from $740^{\circ}C\;to\;790^{\circ}C$. Oxygen partial pressure was controlled between 1 Tow and S Torr. Superconducting YBCO films were obtained from $740^{\circ}C\;to\;790^{\circ}C$ with an oxygen partial pressure of 3 Torr. Scanning electron microscope(SEM) and X-ray diffraction(XRD) observation revealed that films are smooth and highly texture with(001) plans parallel to substrate plane. Highest Jc was 0.72 $MA/cm^2$ at 77K and self-field for the film with a thickness of 0.15 m prepared at a substrate temperature of $740^{\circ}C$ and $PO_2$=3 Torr.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.5
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• pp.338-344
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• 2016

Recent trends in transport system for carrying heavy freight are that demands of a high efficiency, economic efficiency, convenience and safety are increased. Conventional transport systems were poor in transport efficiency and economic efficiency. And Safety problems can be caused to products and workers. In order to overcome these problems, an air cushion transport device with a high-pressure air is required. The air cushion transporter is a device for reducing the frictional force of floor surface and lifting the heavy freight by spraying the high-pressure air to the floor. Technology to float and transfer freight using high-pressure air is very convenient and initial cost can be reduced. In this paper, the study on the levitation performance and transport efficiency of air cushion transport system is conducted and verified that air cushion transporter has a significantly higher transport efficiency than conventional heavy handling systems.

• The Journal of the Korea Contents Association
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• v.10 no.10
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• pp.68-77
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• 2010

In the case of operating steam generators for long periods in nuclear power plants, sludge is accumulated inside the steam generator. This phenomenon could adversely affect the operation of the steam generator. This paper is about the design of a sludge washing apparatus which can remove the sludge efficiently and the control methods of the apparatus. In this paper, to design the sludge washing apparatus, firstly, we design nozzles for spraying high-pressure water through applying mathematical models and lab tests. Secondly, we establish the mathematical theory for performance parameters required to drive the sludge washing apparatus. Thirdly, we design physical structures of the apparatus based on the established performance parameters. Finally, we present the control methods of the apparatus. The sludge washing apparatus presented in this paper moves along the walls of the steam generator according to cracks in the tube array, and spray the high pressure water to remove the sludge. By this way, a relatively large amount of sludge formed in the inner surfaces can be washed very effectively.

• Korean Journal of Materials Research
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• v.24 no.2
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• pp.98-104
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• 2014

Vacuum kinetic spray(VKS) is a relatively advanced process for fabricating thin/thick and dense ceramic coatings via submicron-sized particle impact at room temperature. However, unfortunately, the particle velocity, which is an important value for investigating the deposition mechanism, has not been clarified yet. Thus, in this research, VKS average particle velocities were derived by numerical analysis method(CFD: computational fluid dynamics) connected with an experimental approach(SCM: slit cell method). When the process gas or powder particles are accelerated by a compressive force generated by gas pressure in kinetic spraying, a tensile force generated by the vacuum in the VKS system accelerates the process gas. As a result, the gas is able to reach supersonic speed even though only 0.6MPa gas pressure is used in VKS. In addition, small size powders can be accelerated up to supersonic velocity by means of the drag-force of the low pressure process gas flow. Furthermore, in this process, the increase of gas flow makes the drag-force stronger and gas distribution more homogenized in the pipe, by which the total particle average velocity becomes higher and the difference between max. and min. particle velocity decreases. Consequently, the control of particle size and gas flow rate are important factors in making the velocity of particles high enough for successful deposition in the VKS system.