• 대한기계학회논문집B
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• 제31권2호
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• pp.195-201
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• 2007

A visualization study of flow characteristics in a mixer using multi-nozzle bubbling was performed. The mixer is filed with liquid glycerin (dynamic viscosity = $1000mPa{\cdot}s\;at\;25^{\circ}C$) and convective mixing is induced by air bubbles generated from 9 orifices installed on the bottom of the mixer. To visualize the flow field, PIV (Particle Image Velocimetry) system consisting of 532nm Nd:YAG laser, $2k{\times}2k$ CCD camera and synchronizer is adopted. The bubbles generated with uniform size and frequency form bubble stream and bubble streams rise vertically without interaction between bubble streams. Mixing efficiency is affected by the height of bubbler and the effective height of bubbler is 20nm from the bottom of the mixer.

• 열처리공학회지
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• 제36권1호
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• pp.33-39
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• 2023

In this study, the effect of mixing condition of raw material powders possessing various particle size and particle size distribution on thermite reaction efficiency was investigated. When fine raw powders are used, rather the reaction yield tends to decrease due to agglomeration. In contrast, coarse raw powders make deteriorate the contact area between raw material powders containing Al reducing agent. To ensure the optimal thermite reaction efficiency, it is required to optimize a mixture condition of raw material powders prior to thermite reaction. From the current experiment, the maximum thermite reaction efficiency is 77%, which came from Nb₂O₅ + NiO +Al mixtures with size distribution from 9.25 to 22.63 ㎛.

• 동아시아식생활학회지
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• 제7권2호
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• pp.159-165
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• 1997

The primary objective of this study was to learn the effect of various sugar particle size and level on cookie spread, The effect of sugar particle size and level on sugarsnap cookie spread was studied. Three different particle sized sugars; powered sugar, granulated sugar and sanding sugar, were used for the cookie test baking with five different sugar levels; 30, 45, 60, 75 and 90% based on the weight of flour. In mixing process, 5 minutes of creaming time was used for cream making and then the specific gravity of cream was measured on the basis of each different sugar particle size and level. In the result, the specific gravity of cream was influenced by sugar particle size and sugar level. However, the specific gravity of cream had no influence on cookie dough specific gravity. Cookie spread was influenced by sugar particle size and sugar level. Greater cookie spread was obtained by decreasing sugar particle size and increasing sugar level resulted in increased spread. Therefore, selection of suitable sugar particle size and its use level can be factors in controlling spread and imparting desired packaging characteristics.

• 한국산업보건학회지
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• 제20권4호
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• pp.248-255
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• 2010

Airborne nanoparticle concentrations in three metrics (particle surface area concentration, particle number concentration, and particle mass concentrations) were measured by task in a laboratory making carbon nanotubes (CNTs) films using three direct reading instruments. Because of the conducted other researcher's experiment before the tasks, airborne nanoparticle surface area and number concentrations are the highest at the first time conducted weighing and mixing by sonication task, respectively. Because of the mist generated during mixing by sonication, the highest airborne nanoparticle surface area and PM1 concentrations were measured in the task among the total. Nanoparticle surface area concentrations at the researchers' breathing zones had high correlation (r=0.93, p<0.01) with those measured at an area in the laboratory. This result indicates that nanoparticles generated during the experiment contaminated the whole room air. When the experiment performed all the fume hoods weren't operated and making CNTs films task were conducted in the out of the fume hoods. In conclusion, researchers performing making CNTs film experiments were exposed to airborne nanoparticles generated during the experiment without adequate controls. We recommend that adequate controls should be implemented so that workers' exposures to airborne nanoparticle are limited to minimum levels.

• KIEAE Journal
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• 제13권6호
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• pp.137-143
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• 2013

The purpose of this study is to suggest optimum micro-filler experiment method to select the optimal particle size of earth for using in earth construction works and test this suggestion through compressive strength measurement. According to the results of selecting the method to choose the optimum micro-filler mixing of earth and sand, three-stage filling(plate tamping) showed relatively high results and so was estimated to be the proper filling method. According to the results of optimum micro-filler experiment of earth and sand by the maximal sizes of sand, between 80% and 90% showed the highest result values. The larger the maximum size of sand was, the lower the addition ratio of sand was in optimum micro-filler mixing. According to the results of compressive strength experiment by the particle sizes of earth and sand, 90% in the addition ratio of sand showed the highest results, and so tended to be similar to the results of unit volume weight experiment.

• 한국분무공학회지
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• 제22권1호
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• pp.1-7
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• 2017

Recently, Performance and fuel efficiency of gasoline engines have been improved by adopting direct injection (DI) system instead of port fuel injection (PFI) system. However, injecting gasoline fuel directly into the cylinder significantly reduces the time available for mixing and evaporation. Consequently, particulate matters(PM) emissions increase. Moreover, as the emission regulations are getting more stringent, not only the mass but also the total number of PM should be reduced to satisfy the Euro VI regulations. Increasing the fuel injection pressure is one of the methods to meet this challenge. In this study, the effects of increased fuel injection pressures on combustion and emission characteristics were experimentally examined at several part load conditions in a 1.6 liter commercial gasoline direct injection engine. The main combustion durations decreased about $2{\sim}3^{\circ}$ in crank angle base by increasing the fuel injection pressure due to enhanced air-fuel mixing characteristics. The exhaust emissions and number concentration distributions of PM with particle sizes were also compared. Due to enhanced combustion characteristics, THC emissions decreased, whereas NOx emissions increased. Also, the number concentrations of PM, larger than 10 nm, also significantly decreased.

• 대한화장품학회지
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• 제42권4호
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• pp.387-392
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• 2016

본 연구에서는 동일한 농도의 유동파라핀/ Span 80-Tween 80/ 정제수로 구성되는 조성물을 혼합 경로와 온도에 따라 형성되는 에멀젼 상태를 비교하였다. 3성분계도상에서 최종 조성에 이르는 혼합경로는 세 가지로 구성하였다. 혼합 경로에 따라서 제조된 에멀젼의 평균 입자크기는 큰 차이를 보였으며 제조 온도가 증가함에 따라서도 에멀젼의 입자크기가 감소하였다. 그러나 혼합 온도보다는 혼합 경로에 따른 영향이 더욱 컸다.

• 대한기계학회논문집A
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• 제30권1호
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• pp.32-41
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• 2006

We analyzed the non-Newtonian and non-isothermal flow in the melt conveying zone in co-rotating and counter-rotating screw extruder system with the commercial code, STAR-CD, and compared the mixing performance with respect to screw speed and rotating direction. The viscosity of fluid was described by power-law model. The dynamics of mixing was studied numerically by tracking the motion of particles in a twin screw extruder system. The extent of mixing was characterized in terms of the residence time distribution and average strain. The results showed that high screw speed decreases the residence time but increases the shear rate. Therefore higher screw speed increases the strain and has better mixing performance. Counter-rotating screw extruder system and co-rotating screw extruder has the similar shear rate with the same screw speed in spite of different rotating direction. However, the counter-rotating screw has good mixing performance, which is resulted from longer residence time than that of co-rotating screw extruder.

• International Journal of Aeronautical and Space Sciences
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• 제4권1호
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• pp.26-33
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• 2003

Recess is a geometrical configuration shape that the exit surface of an inner injector is located at a certain length inward from that of an outer injector. It is known to have the characteristics that it can augment mixing efficiency and flame stabilization through internal mixing of propellant in it. So, various experiments, such as backlit stroboscopic photography, phase Doppler particle analyzer(PDPA) and mechanical patternator, were performed at several recess lengths to grasp its effect on the spray characteristics of spray angle, breakup length, atomization and' mixing. Recess length was normalized to dimensionless recess number and two principal mechanisms of impingement and swirl recovery were introduced to explain its influence on the spray characteristics. The effect of recess on SMD doesn't appear significantly near the recess number where mixing efficiency attains to the maximum, whereas mass distribution and mixing efficiency are changed considerably. Thus, it can be inferred that a certain optimum recess number exists, where mixing efficiency becomes the maximum.

• Journal of Animal Science and Technology
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• 제45권5호
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• pp.813-818
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• 2003

본 시험은 자가제조 TMR 농가의 TMR 배합기 운용실태와 국내에서 생산 이용되고 있는 TMR을 대상으로 TMR 배합소에서 생산되는 20개 유통 TMR과 농가에서 직접 제조하여 이용하는 20개 자가 TMR의 입자도를 Penn State Particle Size Separator를 이용하여 측정하여 TMR 입자도의 분포를 측정한 결과, 자가 TMR 배합기를 이용하여 TMR을 제조하는 농가의 1일 총 배합에 소요되는 시간은 48.6${\pm}$28.0분으로 나타났으며, 자가 TMR 농가의 보유 배합기 형태는 2오거가 55.5%로 가장 많았고, 여름철 및 다른 계절에 1일 2회 배합하는 농가가 44.4 및 22.2%였다. 자가 TMR 농가의 배합기 가동시간별 상위 체에 남아 있는 비율이 21.5~25.6%, 중간 체에 남아 있는 비율이 16.0~25.8% 그리고 바닥 체에 남은 사료의 비율은 52.8~61.4%로 많은 차이가 있었다. 자가 및 유통 TMR의 입자 길이가 19mm 이상인 사료의 비율이 각각 24.9${\pm}$1.4 및 26.2${\pm}$1.7%, 입자 길이가 8~19mm미만인 사료의 비율이 각각 22.8${\pm}$1.0 및 12.8${\pm}$1.2% 그리고 입자 길이가 8mm 미만인 사료의 비율이 52.3${\pm}$1.7 및 61.0${\pm}$1.5%였다. 이는 자가 TMR과 유통 TMR 모두에서 8~19mm미만 범위에 있는 입자는 Penn State Separator에서 추천하는 비율보다 각각 82.6%, 100%가 낮은 것으로 나타났는데, 이는 전체적으로 국내에서 생산 이용되고 있는 TMR의 입자도가 긴 것과 짧은 것의 적절한 조화가 이루어지지 않고 있음을 알 수 있다. 따라서 TMR을 급여하고 있는 농가에서 TMR중 입자도가 적정한지를 평가하기 위한 가장 기본적인 일은 우군의 반추행동을 모니터링하는 일이다. 즉, 전체 우군중 사료를 섭취하고 있는 소를 제외하고 휴식중에 있는 소들중 반추를 하고 있는 소가 40%가 안된다면 전체적으로 입자도가 너무 적거나 조사료의 비율이 너무 낮지 않은지 검토하여 배합시간을 조정하거나 배합비를 재조정해 주어야 할 것이다.