• 한국연소학회지
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• 제11권2호
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• pp.22-27
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• 2006

This experimental study has been mainly motivated to obtain generally applicable design correlation for the front mixing premix combustor. The design concept of the front mixing premix combustor is to minimize thermal $NO_x$ and prompt $NO_x$ formation by maintaining low peak flame temperature, and nearly uniform flame temperature through rapid mixing process near the ignition point. The present experimental results clearly indicate that the front mixing premix combustor yields the $NO_x$ level lower than 43 ppm $NO_x$ emissions and the nearly uniform temperature distribution.

• 상하수도학회지
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• 제21권3호
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• pp.359-366
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• 2007

Slow sand filtrations have been widely used for water treatment in small communities, however their capacity is often limited by high turbidity in the raw water. For this reason, several pre-treatment facilities were required for a slow sand filter. Turbidity removal from the highly turbid raw water was investigated in roughing filters as a pre-treatment process. The roughing filters followed by rapid mixing tank were operated in the form of a contact filtration. In several jar tests, the predetermined optimum aluminium sulfate (alum) doses for turbid water of 30 and 120NTU were 30 and 50mg/L, respectively. At the optimum alum dose, physically optimum parameters including G value of $220sec^{-1}$ and rapid mixing time of 3 minutes were applied to the contact filtration system. Without addition of alum, the filtrate turbidity from the roughing filters, packed respectively with different media such as sand, porous diatomite ball and gravel, was in the range of 5~30NTU at filtration velocities of 30 and 50m/day. However, the application of a contact filtration to roughing filters showed stably lower filtrate turbidity below 1.0NTU at filtration velocity of 30 m/day. Although the filtration velocity increased to 50m/day, filtrate turbidity was still below 1.0NTU in both single and double layer roughing filters. At influent turbidity of 120NTU, the filtrate turbidity was over 5 NTU in the triple layer roughing filter, which shortened the filter run time. The flocs larger than $10{\mu}m$, formed in the rapid mixing tank, were almost captured through the roughing filter bed, while the almost flocs smaller than $10{\mu}m$ remained in filtrate.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.809-814
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• 2009

Deep mixing method has been used for ground improvement and foundation system for embankment, port and harbor foundations, retaining wall, and liquefaction mitigations. It has attractive benefits because it is not only improved strength of soft ground but superior for prevention of settlement. However, the quality controls of improved mass affect to the efficiency of the deep mixing method is not properly established. These effects vary depending upon the construction environments and conditions of agitation in consideration of an agitator. The strength and shape of the improved column are not unique and these are affected by mechanical properties of agitators. In this study, in order to investigate the efficiency of deep mixing method for ground improvement on a soft clay ground, experimental studies are performed considering mechanical properties of agitator; the location of exit-hole of admixtures, an angle of mixing wing and a speed of revolution. The experiments are conducted with the simulated apparatus for deep mixing plant that reduced the scale in 1:8 of the real plant. According to the results, the diameter and shape of improved column mass vary depending on the mechanical properties and operating conditions of agitator. Its quality is better when the exit-hole of admixtures is located in the mixing wing, when an angle of mixing wing is large, and when the speed of revolution is rapid.

• 한국지반신소재학회논문집
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• 제14권3호
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• pp.13-20
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• 2015

하수관거 시공시 부적절한 뒤채움재 및 다짐불량으로 인해 하수관로 파손 및 지반침하 현상이 발생한다. 최근들어 이러한 문제점을 해결하기 위해 유동성 채움재에 대한 관심이 증가하고 있다. 본 연구에서는 속경성, 가소성, 유동성, 수중불분리성을 갖춘 뒤채움재의 최적배합 도출과 뒤채움재의 경제성 향상을 위한 기초 연구를 수행하였다. 속경성 결합재의 최적배합 도출 실험 결과를 통해 뒤채움재의 최적 배합의 특성을 평가하였다. 시험결과, 속경성 결합재 페이스트의 W/M을 100%까지 증가시켜도 가소제 첨가량을 적절히 조절하여 사용하면 요구 성능을 만족시킴과 동시에 경제성 또한 확보 할 수 있을 것으로 사료된다.

• International Journal of Aeronautical and Space Sciences
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• 제2권1호
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• pp.12-19
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• 2001

Study of turbulent mixing layers has been a popular subject from the point of view of both practical application and phenomenological importance in engineering field. Turbulent mixing layers can be applied in many fields where rapid transition to turbulence is desirable in order to prevent boundary layer separation or to enhance mixing. The ability to control mixing, structure and growth of the shear flow would obviously have a considerable impact on many engineering applications. In addition to practical applications, free shear flows are one of the simplest flows to understand the fundamental mechanism in the transition process to turbulence. After the discovery of large-scale vortical structure in free shear flows many researchers have investigated the physical mechanism of generation and dissipation processes of the vortical structure. This study investigated the role of the large-scale vortical structures in the turbulent mixing layer using LES(Large-Eddy Simulation). The result shows that the pairing interaction of the vortical structure plays an important role in the growth rate of a mixing layer. It is found that the turbulence quantities depend strongly on the velocity ratio. It is also found that the vorticity in the high-velocity-side can extract energy from the mean flow, while the vorticity in the low-velocity-side lose energy by the viscous dissipation. Finally the results suggest the guideline to obtain the desired flow by control of the velocity ratio.

• 상하수도학회지
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• 제19권3호
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• pp.370-377
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• 2005

Dispersion of coagulant should be completed in a fraction of a second before the metal hydroxide precipitate has form. For the reason so-called pump diffusion flash mixing (PDFM) have been proposed, and PDFM is one of reasonable methods to quickly disperse the hydrolyzing metal salts. In this study, therefore, we attempt to understand the difference of removal characteristics of natural organic matter (NOM) between pump diffusion flash mixing (PDFM) and conventional rapid mixing (CRM) for coagulation in a water treatment system, and to enhance the removal of NOM through the improved mixing process. DOC and turbidity removal by PDFM higher than those by CRM, while SUVA value of water treated by PDFM was high as compared with that by CRM. Hydrophilic NOM was more effectively removed by PDFM than CRM, since charge neutralization effect increased by quick dispersion of coagulant. The DBP formation potentials due to NOM was effectively reduced by the improved mixing (i.e., PDFM) for coagulation and could be controlled through decrease in concentration of precursor rather than reduction of activity with disinfectant.

• 대한환경공학회지
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• 제27권8호
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• pp.799-806
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• 2005

응집-UF 정수공정시 응집 전처리 공정에 있어 완속혼합없이 급속혼화만으로 충분한 응집의 효과를 기대할 수 있으며, 급속혼화장치로 in-line static mixer를 사용한 경우가 기존의 back mixer를 사용 한 경우보다 롤은 DOC 제거효율을 얻을 수 있었다. 또한, 적정 주입량인 16 mg alum/L에서 막의 투과 flux 감소가 가장 적게 나타났으며 적정 주입량보다 너무 적거나 또는 너무 많은 경우 모두 막의 투과 fiux 감소가 크게 나타났다. 또한 막의 fouling에 크게 영향을 미치는 것은 hydrophobic 물질로 이는 응집 전처리시 효과적으로 제거되어짐으로써 막의 투과 flux 감소를 줄일 수 있었다.

• 한국가시화정보학회지
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• 제3권2호
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• pp.45-50
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• 2005

Electro-osmotic flow (EOF) instability in a microchannel has been experimentally investigated using a micro-PIV system. The micro-PIV system consisting of a two-head Nd:Yag laser and cooled CCD camera was used to measure instantaneous velocity fields and vorticity contours of the EOF instability in a T-shape glass microchannel. The electrokinetic flow instability occurs in the presence of electric conductivity gradients. Charge accumulation at the interface of conductivity gradients leads to electric body forces, driving the coupled flow and electric field into an unstable dynamics. The threshold electric field above which the flow becomes unstable and rapid mixing occurs is about 1000V/cm. As the electric field increases, the flow pattern becomes unstable and vortical motion is enhanced. This kind of instability is a key factor limiting the robust performance of complex electrokinetic bio-analytical devices, but can also be used for rapid mixing and effective flow control fer micro-scale bio-chips.

• Journal of Advanced Marine Engineering and Technology
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• 제32권5호
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• pp.663-669
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• 2008

A rapid growth of automobile industry has become a major cause for the environmental pollution of big cities, which has driven the emission regulation into extreme. The study of alternative fuel is one of the many researches for improving car emissions. In this study, the effect of an ethanol mixing rate on the engine performance of exhaust emissions, fuel consumption and a maximum torque is assessed for a gasoline engine without any retrofit. The result shows that maximum torque is not reduced in the range of ethanol mixing rate of 10 to 15%. CO and NOx is reduced with the increase of ethanol mixing rate and the fuel consumption remains in similar level.

• 한국세라믹학회지
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• 제40권3호
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• pp.309-316
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• 2003

지정폐기물인 EAF(Electric Arc Furnace) Dust는 현재 대부분이 매립 등 부적절하게 처리되고 있어 지하수 오염 등의 환경 파괴를 일으킬 위험이 있다. EAF Dust의 자원화를 위하여 EAF Dust/점토 조성으로 세라믹 다공체의 제조 가능성을 연구하였다. 출발 원료들의 혼합은 습식 공정으로 행하였으며, 소결 방법은 급속 소결과 일반 소결을 각각 적용하였다. 소결된 시편의 비중, 기공 및 미세구조를 관찰한 결과. 시편내의 발포현상은 탄소(C)의 양과 액상 생성의 유무에 의해 결정됨이 밝혀졌다. 발포를 용이하게 발생시켜 다공체의 경량골재를 얻기 위해서는 소결 시 급열처리하는 것이 유리하였다.