• Journal of Power System Engineering
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• v.14 no.2
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• pp.5-11
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• 2010

분사연료의 혼합기형성과정 최적화를 통한 연소제어 기술은 디젤기관의 기관운전 및 배기특성을 향상시키기 위하여 매우 중요하다. 또한 분무의 혼합기형성 최적화를 위해서는 분사된 연료와 주위기체와의 혼합과정에 영향을 미치는 분무내부의 유동특성에 대한 연구는 필수 불가결하다. 따라서 본 연구에서는 고온 고압의 증발장에서 분무의 액상 거동에 주목하고, 그 거동특성을 통하여 증발디젤분무의 혼합기형성을 해석한다. 비정상 증발분무의 중심축에 레이저 시트광을 입사한 후, 액상분무 액적의 Mie 산란광에 의한 2차원 화상을 획득하여 증발분무 액상의 속도분포 및 와도(vorticity) 등을 구하였다. 분무의 속도분포 및 와도는 2차원 화상에 PIV법을 적용하여 계산하였다. 그림 1에 본 연구에서 구한 속도분포의 일례를 보인다. 본 연구의 결과로 상변화를 동반하는 비정상 증발장에서 구한 분무액상의 거동 특성은 상변화가 일어나지 않는 비증발장에 있어서의 분무거동특성과 유사함을 확인하였다.

• Journal of ILASS-Korea
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• v.10 no.1
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• pp.43-52
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• 2005

The effect of fuel injection spray on engine performance has been known as one of the major concerns for improving fuel economy and reducing emissions. In general, reducing the spray droplet size could prevent HC emission in gasoline engine. As far as PFI (Port Fuel Injection) gasoline engine is concerned, the mixture of air and fuel may not be uniform under a certain condition, because breakup and production of spray droplets are made in a short distance between the fuel injector and intake valve. This study, by constituting PFI gasoline spray system, was performed to study the transient spray characteristics and dynamic behavior of droplets from 2hole 2spray type injector used in DOHC gasoline engine. Mean droplet size and optical concentration in accordance with various conditions were measured by LDPA and CCD camera. Through this study, the variation of drop size and optical concentration could be used for understanding the behavior of unsteady spray was declared and the existing the small droplets between each pulse spray could be estimated caused to the development of wall film was conformed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.175-178
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• 2006

A numerical study for spray combustion of fluctuated fuel and oxidizer droplets injected into combustion chamber has been conducted for the analysis of spray combustion considering characteristics of injector. The 2 dimensional unsteady state flow fields have been calculated by using QUICK Scheme and SIMPLER Algorithm. As the spray model, DSF model and Euler-Lagrange Scheme have been used. The sine Auction has been used for droplet fluctuation model of fuel and oxidizer, while the coupling effects of the droplets between gas phase and evaporated vapor have been calculated by using PSIC model.

• Journal of ILASS-Korea
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• v.4 no.3
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• pp.15-23
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• 1999

The use of LPG as clean fuel for Diesel engine is very attractive way to reduce soot and NOx emission. In this study, a numerical study has been done to know the transient behavior of LPG fuel in chamber pressures which is held at a pressure above (0.37MPa)and below(0.15MPa)the fuel vapor pressure. Results show that the vortex formed within the start of injection at the leading edge of the spray cone and was most apparent for 0.15MPa chamber pressure case. The high speed photographs and model results showed a narrower cone angle during the quasi-steady spray period at the 0.37MPa chamber pressure compared to the 0.15MPa case. And it can be shown that more realistic vaporization process is necessary to predict the spray length well.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.8-8
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• 1998

액체 추진제를 사용하는 연소기관내의 연소 불안정 현상에 대하여 수치적인 해석을 수행하였다 비정상 다차원 다상 유동장에 대한 Eulerian-Lagrangian 방법에 기반을 두고 수학적으로 모델 하였으며 속도-압력-밀도에 대한 결합메커니즘은 개선된 PISO 알고리즘을 사용하여 처리하였다. 연소실의 기하학적 형상 및 추진제의 분무조건이 액체 연료 추진기관의 연소 불안정 현상에 미치는 영향을 체계적으로 해석하였으며 액체 추진제의 증발 특성이 연소 불안정 현상의 Driving Mechanism에 미치는 영향을 상세히 분석하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.64-74
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• 2005

The effect of fuel injection spray on engine performance has been known as one of the major concerns for improving fuel economy and reducing emissions. In general, reducing the spray droplet size could prevent HC emission in gasoline engine. As far as PFI gasoline engine is concerned, the mixture of air and fuel may not be uniform under a certain condition, because breakup and production of spray droplets are made in a short distance between the fuel injector and intake valve. This study, by constituting PFI gasoline spray system, was performed to study the transient spray characteristics and dynamic behavior of droplets from two-holes two-sprays type injector used in DOHC gasoline engine. Mean droplet size and optical concentration in accordance with various conditions were measured by LDPA and CCD camera. Through this study, the variation of drop size and optical concentration could be used for understanding the behavior of unsteady spray was declared and the existing the small droplets between each pulse spray could be estimated caused to the development of wall film was conformed.

• Journal of Chitin and Chitosan
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• v.23 no.4
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• pp.234-243
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• 2018

In this study, the physicochemical properties of freeze dried (FD) and spray dried powders (SD-MD10, SD-MD20, SD-CD10, SD-CD20) from green coffee bean extract were investigated. Yields were 91.46% for FD powder and 71.63~87.98% for SD powders, respectively. The moisture content of SD powders (1.39~1.86%) was lower than that of FD powder (3.19%). L, a and b value of SD powders were higher than of FD powder. The particle size of the FD powder ($147.67{\mu}m$) was higher than that of the SD powders ($54.23{\sim}66.07{\mu}m$). The water absorption index of the SD powders (0.51-0.59) were lower than that of the FD powder (0.72). The water solubility index of the SD powders, 77.26-90.07%, was higher than that of the FD powder (70.07%). The total phenolic and flavonoid contents of SD-CD10 were 20.67 g/100 g and 8.92 g/100 g, respectively. The chlorogenic acid content of SD-CD10 (12.04 g/100 g) was higher than other SD powders. The DPPH and superoxide radical scavenging activities of SD-CD10 at $1,000{\mu}g/mL$ were 88.02% and 86.89%, respectively. The SD-CD10 was better than other SD powders on protective effects against oxidative stress in L-132 cells (87.33%). In conclusion, we provided experimental evidence that spray-dried powder of green coffee bean extracts have potential as functional food materials.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.19-28
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• 2017

Effects of cavitation and hydraulic flip in circular and elliptical nozzles on the flow characteristics have been studied. Spray tests were conducted using injectors with different ratios of an orifice length(L) to a diameter(d) and of a major axis diameter(a) to a minor axis diameter(b). With the increment of an injection pressure drop, discharge coefficients slightly decreased in cavitation flows, and those suddenly dropped and were almost constant in hydraulic flip flows. For elliptical nozzles with L/b > 8 and L/a < 8, discharge coefficients and flow patterns showed different results from those in previous circular nozzles. When a flow in the elliptical nozzle was under steady condition, as the liquid column went downstream from the nozzle, its spray angle a little decreased in the plane of a major axis and increased in the plane of a minor axis.

• Journal of ILASS-Korea
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• v.15 no.2
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• pp.74-82
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• 2010

In order to understand the behavior of transient gaseous injection used in an LPG (Liquefied Petroleum Gas) engine, turbulent incompressible transient jets with butane and propane were measured and analyzed at pressures of 1.5 bar and 2.0 bar with injector diameters of 3 mm and 5 mm. Mie-scattering method with a tracer was used, and images were processed to investigate the behavior of butane and propane jets. Distances from the nozzle to transition region were measured as $L_e/d_{inj}$=4.35~19.4, where $L_e$ and $d_{inj}$ indicate respectively a distance from nozzle to transition point and nozzle diameter. Slits and tubes around jet at near-field were introduced to measure the effect of entrainment and the diameter of jet, which revealed that the entrainment of surrounding air is significant for developing jet diameter. When the entrainment is restricted, the behavior of jet became deviating from the baseline. It was found that the virtual origin located outside of a nozzle towards jet tip within the conditions of this work, and its location was estimated as $x_o/d_{inj}$=0.56~7.25, where $x_o$ is a distance from nozzle to virtual origin.

• Journal of ILASS-Korea
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• v.24 no.3
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• pp.105-113
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• 2019

In this paper, a study of Urea-SCR System for Dosing Injector for responding to enhanced environmental regulations has been conducted. There is a limit to the experimental approach due to the structural characteristics of the injector. In order to overcome this problem, The analysis was performed assuming unsteady turbulent flow through computational fluid analysis and the internal flow characteristics of the injector were analyzed. By changing the nozzle shape of the injector, the performance factors of the swirl injector by shape were selected and compared. The design parameters were modified by changing the diameter of the nozzle at a constant ratio compared to the base model. Swirl coefficient, outlet mass flow, and sac volume were selected as performance parameters of the injector. The Conv. model to which the taper was applied showed the dominance in mass flow rate, discharge coefficient and swirl because of the smooth fluid flow by shape. Swirl coefficient, outlet mass flow, and sac volume were selected as performance parameters of the injector. As a result of the comparison coefficient derivation with those performance parameters for comparing the performance of the model-specific injector, the Conv-140 model with the nozzle diameter expanded by 140% showed the best value of the comparison coefficient.