• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.88-96
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• 2017

As a part of the development procedures of scramjet engine with a regenerative cooling system, this experiment was performed using air-assist type injectors for scramjet engine. Two types of injectors were used in this experiment with the 90 and 60 degrees of the injection angle to the main flow. Mie-scattering was used for spray visualization and PDPA was used for the measurement of the atomization characteristics. It was found that increasing the pressure of supplied gas and the distance from nozzle tip led to the enhancement atomization characteristics and the injector with 60 degrees injection angle has better atomization characteristics than 90 degrees injector.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.146-156
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• 2003

A numerical algorithm is developed to analyze the performance of a Unit-injector (UI) System for a diesel engine. The fundamental theory of the algorithm is based on the continuity equation of fluid dynamics. The loss factors that should be seriously regarded on the continuity equation are the compressibility effect of liquid fuel, the wall friction loss in high-pressure fuel lines of the system, the kinetic energy loss of fuel in the system, and the leakage of fuel out of the control volume. For an evaluation of the developed simulation algorithm, the calculation results are compared with the experimental outputs provided by the Technical Research Center of Doowon Precision Industry Co. (DPICO) ； the maximum pressure in the plunger chamber (P$\_$p/) and total amount of fuel injected into a cylinder per cycle (Q$\_$f/) at each operational condition. The result shows that the average error rate (%) of P$\_$p/ and Q$\_$f/ are 2.90% and 4.87%, respectively, in the specified operational conditions. Hence, it can be concluded that the analytical simulation algorithm developed in this study can be reasonably applied to the performance prediction of newly designed UI system.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.4
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• pp.339-349
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• 2014

$CO_2$ emission has been gradually increased due to rising fossil fuel use. A gliding arc plasma scrubber (GAPS) was proposed to destruct $CO_2$. For optimum design of GAPS, a CFD analysis has been conducted in different configuration for the system. The parameters considered included gas injection velocity at the nozzle and gas flow rate to gap between electrodes. The reactor configuration affected velocity fields which caused changes in the mixture fraction and the retention time. The mixing effect of $CO_2$ and supplied gas ($CH_4$ and steam) was enhanced by installing a orifice baffle. This revealed that the orifice baffle is effective in $CO_2$ conversion by positioning the reactants in the gas into the center of plasma discharge.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.75-80
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• 2001

The present article deals with the numerical calculations for the inter-spray impingement of two diesel sprays under the conditions of high injection pressure. The Wave model involving the cavitation effect inside the nozzle was used for describing the atomization process. In particular, a hybrid model for drop collision was newly suggested in this study and compared with the O'Rourk's model, which has been widely used for diesel sprays. The impingement angles of 60 and 90 degrees were considered for simulation of non-evaporative diesel sprays. The calculated results for tip penetration were compared with experimental data and the Sauter Mean Diameter(SMD) characteristic was analyzed. It was concluded that the hybrid model slightly shows better agreement with experimental data than the O'Rourke's model. However, the more elaborate study should be needed for better understanding of spray-to-spray impingement phenomena.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.262-265
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• 2002

Fused deposition modelling(FDM) is a rapid prototyping(RP) process that fabricates part layer by layer by deposition of molten thermoplastic material extrude from a nozzle. RP system has many benefit. One of the benefit would be the ability to experiment wiか physical objects of my complexity in a relatively short period of time. But it has a matter of surface roughness and geometric accuracy. We study on Influence of angle of tangent line and area error on sphere surface roughness at fused deposition.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.978-980
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• 2010

Nocolok 브레이징을 이용할 경우 저농도 플럭스와는 달리 고농도 플러스를 이용해 필요한 부분만 도포해야 한다. 일반적으로 고농도 플럭스 도포의 경우 인력을 이용한 수작업을 실시하므로 작업이 비효율적일 뿐만 아니라 플럭스 분진 날림 몇 열 등으로 인해 기피하고 있는 실정이다. 그러므로 경제적이며 효율적인 고농도 플럭스 자동 도포 장치의 개발을 통한 품질 향상 및 생산 단가 저감 등이 절실한 실정이다. 본 연구에서는 고농도 플럭스 자동 도포 시스템을 제작을 위해 수치해석을 이용한 고농도 플럭스 혼합 탱크의 혼합 효율성 및 정수압력을 이용한 유량 분배 해석을 실시하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.177-180
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• 2010

Two-stage light gas gun, sorted with Ballistic Range System, is used to research spray characteristics of supersonic liquid jets. When high pressure tube was pressurized to the 135 bar, diaphragm films which composed with OHP film are ruptured. Expansion gases accelerate a projectile approximately 250 m/s at the exit of pump tube. And accelerated projectile collides with liquid storage part and liquid jets were injected into supersonic conditions. Supersonic liquid jets show the multiple jets and generate shockwave at the forward region of jets. Supersonic liquid jets of speed and shockwave angle have different value at each case. Supersonic liquid jets with minimum velocities are injected with M=1.53 at the geometry condition of L/d=23.8.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1161-1166
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non-inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.1
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• pp.75-80
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non~inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.9
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• pp.745-752
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• 2006

DOS and NaCl aerosol particles were used to determine collection efficiencies of a 2-stage electrostatic wet scrubber with respect to particle size. The DOS and NaCl aerosols have geometric mean diameters of 0.1-3.0 urn, geometric standard deviations of $1.1{\sim}1.8$ and total number concentrations of $450{\sim}2,400\;particles/cm^3$. The tested operating variables for the electrostatic wet scrubber included air velocity and water injection rate. It was shown from the experimental results that particle collection efficiencies increased in the submicron particle size range when different polarities were applied on the water nozzle and corona wire, respectively. This increase in the collection efficiency is attributed to strong electrostatic attraction between the negative water droplets and positive submicron particles. The collection efficiencies also increased when water injection rate was increased or air velocity was decreased. Meanwhile, the pressure drop across the wet scrubber decreased by 90% compared with the existing mechanical wet scrubber. Finally, ammonia gas was used to determine gas removal efficiencies. It was observed that the gas removal efficiencies increased when the air velocity was decreased or the water injection rate was increased.