• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.356-367
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• 2005

The spray characteristics of DISI injector have a great role in gasoline engine efficiency and emission. Thus, many researchers have studied to investigate the spray characteristics of swirl and slit injectors that are used in a DISI engine. In this study, we tried to provide spray parameters, which affect on the spray characteristics such as injection pressure, ambient pressure and ambient temperature. In addition, we calculated $t_{b}\;and\;t_{c}$ to investigate the break up mechanism of test injectors and obtained $C_{v}$ to evaluate the spray characteristics. As the ambient pressure increases in case of slit injector, $C_{v}$ decreases. The laser-induced exciplex fluorescence (LIEF) technique, which is based on spectrally resolved two-color fluorescent emissions, has applied to measure the liquid and vapor phases for on evaporating spray simultaneously. The TMPD/naphthalene proposed by Melton is used as a dophant to detect exciplex signal. The temporal and spatial distribution of liquid and vapor phases during the mixture formation process was measured by this technique. In the LIEF technique, the vapor phase is detected by the monomer fluorescence while the liquid phase is tracked by the exciplex fluorescence. From this experiment, we found that the spray area of the vapor phase is increased with elapsed time after injection and the area of liquid is decreased when the ambient pressure is 0.1MPa. However, the area tends to increase until the end of injection when the ambient pressure is 1.0MPa.

• Journal of the Korea Institute of Building Construction
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• v.23 no.5
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• pp.559-570
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• 2023

The corrosion of structural steel used in the construction industry is increasing due to the industrialization where many aggressive ions released in the atmosphere. Therefore, in the present study Al coating was deposited by arc and plasma arc thermal spray process and compared their effectiveness in simulated weathering condition i.e. Society of Automotive Engineers(SAE) J2334 solution which mostly contain Cl^- and CO₃^2- ions. Different analytical techniques have been used to characterize the coating and draw the corrosion mechanism. The Al coating deposited by plasma arc thermal spray process exhibited uniform, dense and layer by layer deposition resulting higher bond adhesion values. The open circuit potential(OCP) of Al coating deposited this process is exhibited more electropositive values than arc thermal spray process in SAE J2334 solution with immersion periods. The total impedance of plasma arc thermal spray process exhibited higher than arc thermal spray process. The corrosion rate of the plasma arc thermal sprayed Al coating is reduced by 20% compared to arc thermal spray process after 23 days of immersion in SAE J2334 solution.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.6
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• pp.442-448
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• 2009

To evaluate the combustion mechanism of each droplet cluster downstream of the premixed spray flame, the simultaneous time-series measurements were conducted by using optical measurement system consisting of laser tomography, multi-color integrated Cassegrain receiving optics (MICRO) and phase Doppler anemometer (PDA). Furthermore, the group combustion number of droplet cluster was estimated experimentally, and the combustion mechanism of droplet cluster was examined applying the theoretical analysis. The group combustion number, $G_c$, was experimentally estimated about all droplet cluster verified by planar images, and it was classified into the internal group combustion mode and the external group combustion mode according to the theoretical analysis. It is found that there are cases in which the group combustion number estimated experimentally for droplet cluster agree or disagree with the classification by theoretical analysis. The reason of disagreement is considered due to that the group combustion number was only estimated by the geometrical arrangement of droplets in cluster, and that the actual phenomenon is three-dimensional but the measurement system is two-dimensional.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.12
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• pp.1115-1120
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• 2007

This paper presents a novel mechanism of electro-spray micro-thruster featured by a nozzle with a conductive pole inside, referred to here as a pole type nozzle. And the effects of the pole type nozzle on the efficiency of the jetting are numerically and experimentally investigated. The electric voltage signal applied to the upper electrode plate, against the pole as the ground, allows a ejection of spray to take place. It is verified experimentally that the use of the pole type nozzle allows a stable and sustainable jetting mode of ejection for a wider range of applied voltages because it can concentrate the electric field more on the centre of the meniscus. According to results about size effect, experiments indicates that the proposed mechanism allows that operation of micro thruster at less than 500 volts through nanoscale nozzle.

• Korean Journal of Environmental Agriculture
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• v.25 no.4
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• pp.352-358
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• 2006

We investigated the mechanism on occurring of briny injury in four fruit species (apple, pear, grape, peach). Briny injury of apple, pear, peach, and grape was induced by the foliar splay of saline solutions. Browning symptom was initiated one hour after the spray of 3% NaCl in apple, pearl and peach trees. while two hour were needed for grape, but the latter developed the symptom faster than the formers. Foliar spray of 3% NaCl resulted in 4-fold increase in ethylene production 24 h after the spray, and the production was returned to early stage rate after 72 h. Ethylene production of control was nearly constant with slight decrease after 4 h. Browning and defoliation response to the spray of 3% NaCl on lower side were not different from the spray on both sides regardless of fruit species, while no injury symptoms occurred by the spiny on upper side. In saline damage for treated date, lateral bud was only germinated in apple at 30 July. A shoot apex was 100% grew in all fruit tree. In result for hormonal content of leaf and shoot apex, control was high t-zeatin content in leaf. However, IAA and ABA content was increasing in high saline concentration.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.200-205
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• 2008

Spray formation mechanism was controlled by a cavitation inside an injection nozzle. Nozzle geometry affects spray characteristics and formation behavior, which could determine engine performance and pollutant formation. A study was carried out on the influence of aspect ratio on cavitation inside a nozzle. The cavitation model available in Star-CD code was used to obtain cavitation behavior inside nozzle, which was compared with previous experimental results. In this paper, a CFD approach combining multiphase Volume-of-Fluid(VOF) and k-model was applied. The numerical results are similar with the experimental results.

• Journal of Mechanical Science and Technology
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• v.15 no.8
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• pp.1196-1204
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• 2001

The effects of EGR(Exhaust Gas Recirculation) on heavy-duty diesel engine performance, NO and soot emissions were numerically investigated using the modified KIVA-3V code. For the fuel spray, the atomization model based on the linear stability analysis and spray wall impingement model were developed for the KIVA-3V code. The Zeldovich mechanism for the formation of nitric oxide and the soot model suggested by Hiroyasu et al. were used to predict the diesel emissions. In this paper, the computational results of fuel spray, cylinder pressure, and emissions were compared with experimental data, and the optimum EGR rates were sought from the NO and soot emissions trade-off. The results showed that the EGR is effective in suppressing NO but the soot emission was increased considerably by EGR. Using cooled EGR, soot emission could be enhanced without worsening of NO.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.61-65
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• 2002

The present study was numerically and experimentally performed to investigate the fire suppression performance of water mist spray subjected to thermal radiation in closed space. Downward-directed water mist sprays to interact with an under kerosine pool fire were investigated in test facility. The mass mean diameters of water mist droplet were measured by PMAS under various flow conditions. The developed water mist spray nozzle was satisfied to the criteria of NFPA 750, Class 1. The mechanism of the fire suppression by water mist was concluded to be cooling of the fire surface which lead to suppressed of fuel evaporation. It was proved that the water mist spray system under lower pressures could be applied to underground fire protection system.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.148-152
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• 1997

A numerical method is presented to predict and analyze the shape and the temperature history of a growing billet produced form the "spray forming" which is a fairly new near net-shape manufacturing process. It is important to understand the mechanism of billet growing and the cooling history of the spray deposited body, because one can obtain a billet with the desired final shape without secondary operations by accurate control of the billet shape and, moreover, growing velocity together with the cooling rate define the microstructure of the final formed product. In the present study, a theoretical model is first established to predict the shape of the billet and next the transient axisymmetric heat conduction problem with growing domain is solved using the so called "front tracking finite element technique".ent technique".uot;.

• Journal of Surface Science and Engineering
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• v.29 no.6
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• pp.745-752
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• 1996

Wear property of plasma spray coating in $Cr_2O_3$ powder manufatured of spray dry method on the aluminum substrate was inspected for the application of piston-ring of automotive enginel. The plama spray coatings were varied with feed rate and particle size. Used the ball-on disc type tribometer, wear volume, friction, surface rougness were investigated. The delamination of the coating layer were observed with SEM. Also the cross-section of wear track were investigated, using optical microscopy. As a result of experiment, wear mechanism was addressed in the various coating process.