• Food Science and Preservation
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• v.16 no.4
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• pp.541-548
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• 2009

We developed a surface washing system for ginseng. The washing system was developed using different treatments and conditions and characterized in terms of product hardness, weight loss, and change in temperature and color. Optimal results were obtained using a surface washing system involving a washing conveyor speed of 1.0 L/min, a water pressure of $35\;kg/cm^2$, a washing nozzle angle of $40^{\circ}$, a washing height of 5 cm, a 1-sec reciprocating washing nozzle cycle, a dehydration wind velocity of 30 m/sec, and an internal drying temperature of $30-33^{\circ}C$. A surface washing system using a washing conveyor speed of0.8 L/min, a water pressure of $40\;kg/cm^2$, a washing nozzle angle of $40^{\circ}$, a washing height of 3 cm, a 1-sec reciprocating washing nozzle cycle, a dehydration wind velocity of 30 m/sec, and an internal drying temperature of $30-33^{\circ}C$ resulted in ginseng that was stained yellow.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.335-340
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• 2005

A study on the variation of combustion characteristics by injector geometries was conducted. Coaxial swirl injectors were used. Existence of swirl chamber and variation of a nozzle length become key parameters. Injectors were identified as open, closed and mixed type by existence of swirl chamber. Variation of nozzle length was made extruding the both nozzle along the axis while other design parameters remain the same. A uni-element combustor with ablative material liner and a water cooled nozzle made by oxygen free copper with outer stainless steel casing were used.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.247-250
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• 2005

In the case of appling a unielement injector developed for a full scale liquid rocket combustor, a operating condition or configuration of the injector is changed by combustion pressure, arrangement and injector quantity of a full scale liquid rocket combustor. In order to verify application, swirl coaxial injectors propelled by jet-A1 and liquid oxygen are tested at different conditions of a combustion pressure, a flowrate and an injector length. As a test result, the application of the present swirl coaxial injectors is excellent because an efficiency of a characteristic velocity is increased at the each test condition beyond that variation of dynamic pressure intensity is small.

• Development and Reproduction
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• v.4 no.2
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• pp.161-173
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• 2000

The aim of this study was to assess the effect of the frequency of the L$N_2$ infusion on the ultrastructure, metabolism and development of the embryo after freezing and thawing by computerized cell freezer. Two-cell embryos of ICR mouse were randomly allocated into fresh (control), high-frequency freezing (group 1) and low-frequency freezing (group 2). For fresh and frozen-thawed intact 2-cell embryos, total ceil number in the blastocyst was counted by fluorescent microscope after Hoechst 33258 staining. Relative amount of $H_2O$$_2$ was measured by DCHFDA. Intracellular location and membrane potential of the mitochondria were evaluated by staining with rhodamine 123 and JC-1. The structure of actin filament was also evaluated by confocal microscope. DNA fragmentation was assessed by TUNEL method after development into blastocyst. The survival rate of intact embryo was higher in group 1 than group 2 (50.7％ vs. 34.6％ respectively, p<0.05). The blastocyst developmental rate was significantly low in group 2 (86.7％, 76.7％ vs. 44.0％ for control, group 1 and group 2 respectively, p<0.05). Total cell number in the blastocyst was also significantly lower in group 2 than control (79.5$\pm$12.9, 71.6$\pm$8.0, and 62.5$\pm$4.7 for control, group 1 and group 2 respectively, p<0.05). The relative amount of $H_2O$$_2$ was higher in group 2 than other groups (15.3$\pm$3.0, 16.6$\pm$1.6 vs. 23.4$\pm$1.8, p<0.05). After JC-1 staining, relative intensity of mitochondria with high membrane potential was significantly lower in group 2 than control and group 1 (17.2$\pm$3.8, 17.4$\pm$1.3 vs. 13.2$\pm$2.0, p<0.05). In group 2, partial deletion and aggregation of the actin filament was found. DNA fragmentation rate was also hieher for group 2 versus other groups (30.8％, 36.0％ vs. 65.6％, p<0.05). The frequency of the L$N_2$ infusion is an important factor for the development of frozen-thawed mouse embryo. High-frequency infusion may prevent damages of cytoskeleton and mitochondria in the embryo probably by preventing the temperature fluctuation during dehydration phase. We speculate that the application of high-frequency infusion method in human embryo may be promising.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.112.2-112.2
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• 2010

슬러리 기포탑 반응기는 열 및 물질 전달의 용이성, 낮은 운전비용 및 장치의 간단성의 장점을 가지고 있어서 Fischer-Tropsch 반응, bio-reaction 등에 많이 응용되고 있다. 그러나 기포탑 반응기 내의 물질 거동은 매우 복잡하기 때문에 많은 연구가 이루어지고 있음에도 불구하고 그 현상에 대한 명확한 이해는 어려운 상황이다. 특히 기포탑반응기내에 기체의 포집율(gas hold-up)을 증가시키는 것을 목적으로 하는 연구들이 활발히 진행되고 있다. 본 연구에서는 기체의 분사 방향에 따른 기체 포집율의 변화를 관찰하였다. 기체 분사는 0.6 mm의 pore가 66개로 구성된 perforated plate를 통해서 이루어졌고, 수직방향, 수평방향, 45도 그리고 수직/수평 조합의 네 가지 분사방향에 대해서 실험을 수행하였다. 반응기는 내경이 0.15 m이고 높이 2.0 m 아크릴 반응기를 이용하였다. 사용된 연속상은 수돗물을 사용하였고 분산상 기체로는 압축 공기를 이용하였다. 전체적인 기체 포집율은 수직방향의 분사방향에서 가장 높게 측정되었다. 그리고 수직/수평의 조합 분사방향의 경우, 기체 포집율이 가장 낮게 관찰되었다. 이것은 분사방향이 수직/수평으로 서로 엇갈릴 경우, 기포간의 충돌 가능성이 높아지고 bubble coalescence가 증가하였기 때문인 것으로 보인다. 실제로 homogeneous flow regime에서 heterogeneous flow regime으로 전환되는 기체선속도는 분사방향이 수직, 45도, 수평, 수직/수평 조합의 순서로 감소하였다. 즉 이 순서로 기체흐름의 와류가 증가하는 것을 알 수 있었다. 또한 Dynamic Gas Disengagement(DGD) 분석을 통하여 큰 기포가 발생하기 시작하는 기체 선속도의 변화를 관찰하였다. 이 경우, 예상되듯이 수직/수평 조합에서는 1.5 cm/sec 기체 선속도에서 큰 기포가 발생하기 시작한 반면 수직 방향 분사의 경우에는 2.5 cm/sec의 보다 높은 기체 선속도에서 관찰되기 시작하였다. 이러한 현상들을 종합하였을 때, 기체 분사방향을 수직으로 일정하게 했을 때, 기포간 출동을 최소화하고 와류발생을 최대한 지연시키며 전체 기체 포집율을 증가시킬 수 있음을 알 수 있다.

• 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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.53-57
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• 2007

고속회전의 원심력으로 연료를 공급하고 액체연료의 미립화를 초래하는 회전연료분무장치에 대한 분무특성 시험연구를 수행하였다. 특정한 공간상에 존재하는 액적의 특성을 이해하고자 고속회전 연료분사시스템을 설계 제작하였다. 시험장치는 고속으로 회전하는 Spindle, 회전연료노즐, 가압식 물탱크, 아크릴 케이스로 구성하였다. 액적의 크기와 속도를 측정하기 위해 PDPA(Phase Doppler Particle Analyzer)시스템을 사용하였고, ND-Yag Laser를 사용하여 분무를 가시화 하였다. 시험결과 고속회전 연료분사시스템의 분무특성을 확인할 수 있었고, 회전속도는 액적 크기, 속도, 분무각 및 분무패턴 등의 분무특성에 주요한 영향을 미치는 것으로 확인되었다.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.1
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• pp.17-26
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• 2005

Both numerical analysis and cold tests for the swirl coaxial type injector were performed to obtain the influence of spray angle, velocity ratio and liquid film thickness for pressure drop and recess. The basic experimental and numerical data obtained in this study can be applicable to the performance design of swirl coaxial type injector. Spray angle was not affected by the applied test pressure drop, but spray angle was affected by tangential velocity ratio and shape factors. Feasibility of numerical analysis for the liquid film thickness and spray angle was confirmed, and the change of liquid film thickness by tangential velocity ratio affected more seriously than pressure drop, and liquid film thickness was decreased with increasing tangential velocity ratio.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.12
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• pp.48-58
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• 2006

The spray and combustion characteristics of liquid jet in cross flow with variation of injection angle are numerically studied. Numerical analysis was carried out using KIVA code, which may be used to generate numerical solutions to spray and chemical reactive fluid problem in three space dimensions and modified to be suitable for simulating liquid jet ejected into the cross flow. Wave model and Kelvin- Helmholtz(KH) /Rayleigh-Taylor(RT) hybrid model were used for the purpose of analyzing liquid column, ligament, and the breakup of droplet. Penetration length increases as flow velocity decreases and injection velocity increases. Numerical error increases as inflow velocity increases. The results of flame propagation contour in combustion chamber and local temperature distribution, combustion emissions were obtained.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.37-44
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• 2002

A theoretical study of spray and combustion characteristics due to coaxial twin-fluid injection is conducted to investigate the effects of liquid jet property, droplet size, contact length and liquid jet velocity. Model is properly validated with measurements and shows good agreement. Prediction of jet contact length, droplet size, liquid jet velocity reflects genuine features of coaxial injection in physical and practical aspects. Both the jet contact length and tile droplet size are reduced in a linear manner with an increase of injector diameter. Cross sectional area of liquid intact core is reduced with augmented jet splitting rate, thus the jet is accelerated to maintain the mass continuity and with an assistant of momentum diffusion by burnt gas.