• 한국표면공학회지
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• 제29권6호
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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.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.251-255
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• 2005

본 연구에서는 스월 인젝터의 기하학적 형상에 따른 분무특성 파악을 위해 액막두께 측정방법을 사용하였다. 액막두께 측정을 위해 특별히 제작된 인젝터를 사용하였으며, 백홀과 스월챔버 그리고 오리피스의 길이에 따른 분무특성을 확인하였다. 분무특성 파악을 위해 분사압에 따른 유량변화, 오리피스 하단의 액막두께와 분무각을 측정하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1703-1708
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• 2003

The present study investigates the effect of injection angle of water mist on fire suppression characteristics by numerical simulation. In order to validate the temperature field by numerical simulation, the predicted results are compared with experimental data. It shows that the temperature difference between measurements and predictions are within $10^{\circ}C$ Numerical simulations of fire suppression are performed for 4 different injection angle($60^{\circ}$, $90^{\circ}$, $120^{\circ}$, and $180^{\circ}$). The grobal mean temperature over the fire compartment decrease with increasing of spray angle. The result shows that the heat transfer between droplets and gas phase are enhaced with the increasing of spray angle. Near the fire source, temperature field by the wide spray angle is slightly higher than that of narrow injection angle because of direct cooling of fire source.

• 대한기계학회논문집B
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• 제24권7호
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• pp.1010-1019
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• 2000

The main purpose of this article is to propose and assess a new spray impingement model considering film formation, which is capable of describing the droplet distribution and film flows in direct injection diesel engines. The spray-wall interaction model includes several mathematical formulae, newly made by the energy conservation law and some experimental results. The model consists of three representative regimes, rebound, deposition and splash. In addition, the film flow is described in the present model by solving the continuity and momentum equations for film flows using the integral method. To assess the new spray impingement model, the calculated results using the new model are compared with several experimental data for the normally impinging diesel sprays. The film model is also validated through comparing film radius and thickness against experimental data. The results show that the new model is generally in better agreement with experimental data and acceptable for prediction of the film radius and thickness.

• 한국재료학회지
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• 제12권10호
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• pp.784-790
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• 2002

For mass product of nanocrystalline ZnO ultrafine powders, self-sustaining combustion process(SCP) and ultrasonic spray combustion method(USCM) were applied at the same time. Ultrasonic spray gun was attached on top of the vertical type furnace. The droplet was sprayed into reaction zone of the furnace to form SCP which produces spherical shape with soft agglomerate crystalline ZnO particles. To characterize formed particles, fuel and oxidizing agent for SCP were used glycine and zinc nitrate or zinc hydroxide. Respectively, with changing combustion temperature and mixture ratio of oxidizing agent and fuel, the best ultrasonic spray conditions were obtained. To observe ultrasonic spray effect, two types of powder synthesis processes were compared. One was directly sprayed into furnace from the precursor solution (Type A), the other directly was heated on the hot plate without using spray gun (Type B). Powder obtained by type A was porous sponge shape with heavy agglomeration, but powder obtained using type B was finer primary particle size, spherical shape with weak agglomeration and bigger value of specific surface area. 9/ This can be due to much lower reaction temperature of type B at ignition time than type A. Synthesized nanocrystalline ZnO powders at the best ultrasonic spray conditions have primary particle size in range 20~30nm and specific surface area is about 20m$^2$/g.

• 치위생과학회지
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• 제19권2호
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• pp.107-112
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• 2019

Background: Good oral health is important for systemic body health and quality of life. Spray oral cleansers are increasingly preferred because of their convenience of carrying and the ease of oral hygiene management. In addition, many kinds of oral cleanser products containing various ingredients with antibacterial, washing, and moisturizing effects are being manufactured. However, concerns about the safety and side effects of oral sprays are increasing, and there is very little information regarding the use and care of oral sprays is available to consumers. This study aimed to investigate the effects of oral spray on oral bacteria and tissue to elucidate the factors that need to be considered when using oral sprays. Methods: The effects of oral spray on the growth of dental plaque bacteria was assessed using disk diffusion assays. Cytotoxicity and morphological changes in oral epithelial cells were observed by microscopy. The effects of oral spray on dental plaque growth were also confirmed on specimens from permanent incisors of bovines by Coomassie staining. Results: The pH of spray products, such as Perioe Dental Cooling, Cool Sense, and Dentrix, were 3.65, 3.61, and 6.15, respectively. All tested spray products showed strong toxicity to dental plaque bacteria and oral epithelial cells. Compared with those on the control, dental plaque bacteria deposits on the enamel surface increased following the use of oral spray. Conclusion: Three types of oral spray, namely Perioe Dental Cooling, Cool Sense, and Dentrix, strongly inhibited the growth of dental plaque bacteria and oral epithelial cells. The oral spray ingredient enhanced dental plaque growth on the enamel surface. Users should be informed of precautions when using oral sprays and the need for oral hygiene after its use.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2005년도 추계학술발표회 및 workshop
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• pp.181-182
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• 2005

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.951-961
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• 2001

The present article presents an extension to the computational model for spray/wall interaction and liquid film processes that has been dealt with in the earlier studies (Lee and Ryou, 2000a). The extensions incorporate film spread due to impingement forces and dynamic motion induced by film inertia to predict the dynamic characteristics of wall films effectively. The film model includes the impingement pressure of droplets, tangential momentum transfer due to the impinging droplets on the film surface and the gas shear force at the film surface. Validation of the spray/wall interaction model and the film model was carried out for non-evaporative diesel sprays against several sources of experimental data. The computational model for spray/wall interactions was in good agreement with experimental data for both spray radius and height. The film model in the present work was better than the previous static film model, indicating that the dynamic effects of film motion should be considered for wall films. On the overall the present film model was acceptable for predication of the film radius and thickness.

• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.235-245
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• 2002

The present article aims to perform numerical calculations for inter-spray impingement of two diesel sprays under a high injection pressure and to propose a new hybrid model for droplet collision on the basis of literature findings. The hybrid model is compared with the original O'Rourke's model, which has been widely used for spray calculations. The main difference between the hybrid model and the O'Rourke's model is mainly in determination of the collision threshold condition, in which the preferred directional effect of droplets and a critical collision radius are included. The Wave model involving the cavitation effect inside a nozzle is used for predictions of atomization processes. Numerical results are reported for different impingement angles of 60°and 90°in order to show the influence of the impinging angle on spray characteristics and also compared with experimental data. It is found that the hybrid model shows slightly better agreement with experimental data than the O'Rourke's model.

• 한국전산유체공학회지
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• 제12권2호
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• pp.32-36
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• 2007

NUFLEX is a general purpose program for the analysis 3D thermo/fluid flow and pre/post processor in a complex geometry. NUFLEX is composed of various physical models, such as phase change(solidification/melting) and spray, MHD(Magneto Hydraulic Dynamics) models. It is possible to simulate continuous cast iron process and spray droplet breakup/collision phenomenon. For the verification of these models, compared with the experimental data and commercial CFD code's results. The results show good agreements with experimental and comercial CFD codes's results.