• Journal of ILASS-Korea
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• v.2 no.2
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• pp.35-42
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• 1997

An innovating technique of atomizer has been proposed to supply and to atomise molten materials. Both of a simple geometry of nozzle and an improved nozzle have been fabricated in the present study. With these nozzles, characteristics of the suction and disintegration have been empirically investigated. The important conclusions are as follows; In the case of a simple nozzle: 1) Although the sucking up and supplying of molten materials are available, the applications of powder metallurgy are limited. 2) It is concluded that the more air flow rate, $W_A$ or the shorter the height of air nozzle from the surface of supplied water, $L_h$, the more the atomizing mass of liquids, $W_L$. In the case of an improved nozzle: 3) The stable liquids can be supplied due to cut off the passage of surrounding air entrainment by air jets. 4) The atomizing mass of liquids, $W_L$ has affected not so much on the height of nozzle from the surface of supplied water, $L_h$ as that from the orifice, hc.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.28-34
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• 1996

Study on the mechanism of droplet transport and the droplet eddy diffusivity in the intake manifold of internal conbustion engine with carburetor has been carried out in this paper The theory and experiments were studied and performed respectively, to elucidate the mechanism and to measure typical rates of deposition, on the walls of a straight type intake manifold, of water droplets suspended in a turbulent air streams. Accordingly, the results are that Mechanism of a spray transport to the walls is caused by the fluctuation component of radial velocity. Deposition rate of a spray on the walls is mainly dependent upon air velocity and mean diameter of spray, and Droplet eddy diffusivity in the intake manifold is around $80\sim105cm^2/sec$.

• Journal of ILASS-Korea
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• v.1 no.2
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• pp.33-41
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• 1996

Mixture formation is one of the important factors to improve combustion performance of MPI gasoline engines. This is affected by spray and atomization characteristics of injector. Especially, in the case of EGI system, air-fuel mixing period is too short and formed a lot of fuel-film in the intake manifold and cylinder wall. This fuel-film is not burnt in cylinder, it is exhausted in the form of HC emission. In this paper, spray characteristics such as size distributions, SMD, and spray angle are measured by PMAS, and the fuel-film measuring device is developed specially. Using this device, the amount and distribution of fuel-film which flows into through valve can be measured Quantitatively. As the result of these experiments, the information of optimal spray characteristics and injection condition that minimize the fuel-film can be built up.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.5
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• pp.76-84
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• 1990

To study diesel fuel spray behavior, an experimental study was undertaken to investigate injection characteristics in vary ing back pressure and atomization mechanism in a non-evaporating diesel spray. Generally, injection characteristics is the curve of fuel flow plotted against time. The area under this curve is equal to the total quantity of fuel discharged for one injection. The method that measures rate of injection is long tube-type fuel rate indicator. Diesel spray injected into a quiescent gaseous environment under high pressure is observed by taking high speed camera by the focused shadow photographs. The results show that, at the start of injection, as the injected fuel rushes into the quiescent atmosphere the spray angle becomes large. Finally the spray stabilizes at a constant cone angle. Spray penetration length increases with the injection pressure.

• Journal of ILASS-Korea
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• v.2 no.1
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• pp.18-28
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• 1997

The present study is mainly aiming at numerically analyzing the combustion and emission characteristics of the diesel spray in a high-pressure environment. Computations are peformed for the peak chamber pressure with range from 4.08 MPa to 162 MPa. Numerical results indicate that the pressure increase in combustion chamber significantly influences the mechanism for droplet dynamics and mixing characteristics, spray penetration autoignition, flame lift-on height and the propagation or fuel vapor and flame. By increasing the ratio or the ambient density to injected liquid density, the fuel-air mixing rates and the burning rates increase and the $NO_x/soot$ emission level decreases.

• Journal of Biosystems Engineering
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• v.21 no.2
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• pp.117-122
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• 1996

Droplet sizes produced from a mist blower should be adequate to get highly biological effects with a reasonable level of work performance. However the droplet sizes from the conventional nozzles of the mist blower were around VMD 95 to 469$\mu$ which were relatively large as compared with the recommended droplet sizes in liquid flow rate of 17.2 m$/ell$s with air flow rate of 16660$m^3$/s on the maximum travel distance of about 4.0 m. The velocity of air stream at the point where two fluids, air and liquid, impact each other, was tried to maximize as much as possible in order to enhance the atomization performance of a newly designed twin fluid nozzles with the same or better level of performance of the conventional mist blower, The configuration of nozzle orifice should be designed to enlarge the contact area between air and liquid to enhance the atomization.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.193-199
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• 2008

Spray coating is a versatile surface modification technology in which coating is built-up based on the successive deposition of micron-scaled particles. Depending on the coating materials, the coatings can meet the required mechanical properties, corrosion resistance, and other properties of base materials. Spraying processes are mainly classified into thermal and kinetic spraying according to their bonding mechanism and deposition characteristics. Specifically, thermal spraying process can be further classified into many categories based on the design and mechanism of the process, such as frame spraying, arc spraying, atmospheric plasma spraying (APS), and high velocity oxygen-fuel (HVOF) spraying, etc. Kinetic spraying or cold gas dynamic spraying is a newly emerging coating technique which is low-temperature and high-pressure coating process. In this paper, overall view of thermal and kinetic spray coating technologies is discussed in terms of fundamentals and industrial applications. The technological characteristics and bonding mechanism of each process are introduced. Deposition behavior and properties of technologically remarkable materials are reviewed. Furthermore, industrial applications of spray coating technology and its potentials are prospected.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.2
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• pp.206-212
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• 2009

The pressurized spray system with nitrogen gas was designed to fabricate the spherical AN(ammonium nitrate) particles. When AN melt was sprayed from a nozzle with equivalent diameter of 0.28mm into an ambient dry air, the ligament breakup mechanism of the molten AN was found to be responsible for the droplet formation(or disintegration) of AN melt. In the experimental range of spray temperature with $170{\sim}200^{\circ}C$ and atomization pressure with $0.1{\sim}0.4MPa$, the spherical AN particles with mean diameter of $130{\sim}250{\mu}m$ were obtained.

• Korean Journal of Agricultural Science
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• v.14 no.1
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• pp.81-97
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• 1987

Two nozzles with different size (Figure 2) were particularly designed to supply air through the swirl core into the central part of the liquid stream in the same parallel direction to produce a well-mixed air and water in the whirl chamber as spray liquid in bubble formation. Atomization was attempted to improve by using both the preliminary break-up process with less viscosity and less surface tension in the whirl chamber and the effects of increased frequency of the band of drops with the raised ambient air density in front of the nozzle orifice. The volumetric ratio between spray liquid and air on four levels was used to investigate the effects of air as a component of the mixture on atomization. The results of the experiment were summarized as follows; Droplet size became progressively finer as the operating pressure was increased in the range of $0.70kg/cm^2$ to $6.33kg/cm^2$, which was similar to the previous works. The new atomizing mechanism so-called 'air-center nozzle' gave a narrower range in droplet size distribution with smaller volumetric median diameter (VMD) than that of the existing spray system at a given pressure, which showed the possibility of improvement of atomization in a certain limit. The volumetric median diameter produced by the new atomizing mechanism was decreased from the central region toward the exterior edges across the spray pattern.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.213-218
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• 1996

Characteristics of high density U-Mo alloy powder prepared by centrifugal atomization have been examined. The results indicate that the majority of the atomized U-Mo alloy particles has a smooth surface and frequently near-perfect spheroidal shape with few satellites attached. The size distribution of atomized U-Mo alloy powder shows the mono-modal size distribution seen in ligament disintegration mechanism. All phases of atomized alloy powder below 150$\mu\textrm{m}$ irrespectively to particle size are found to be ${\gamma}$-U (cubic structure) phases with isotropic structure and not to be U$_2$Mo phase at all. The microstructure of atomized U-Mo alloy particulates has micro-crystalline structure with non-dendritic gram supersaturated with Mo element. Also the grain size of ${\gamma}$ -U tends to decrease with the decrease of the powder diameter.