• 한국입자에어로졸학회지
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• 제12권1호
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• pp.21-26
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• 2016

In order to realize In-line and convenient measurement for solid-gas two phase flows, Light Transmission Fluctuation (LTF) based on the random variation of transmitted light intensity, light scattering theory and cross-correlation method was presented for online measurement of particle size, concentration and velocity. The statistical relationship among transmitted light intensity, particle size and particle number in measurement zone was described by Beer-Lambert Law. Accordingly, the particle size and concentration were determined from the fluctuation signal of transmitted light intensity. Simultaneously, the particle velocity was calculated by cross-correlation analysis of two neighboring light beams. By considering the influence of concentration variation in industrial applications, the improved algorithm based on spectral analysis of transmitted light intensity was proposed to improve measurement accuracy and stability. Therefore, the online measurement system based on LTF was developed and applied to measure pulverized coal in power station and raw material in cement plant. The particle size, concentration and velocity of powder were monitored in real-time. It can provide important references for optimal control, energy saving and emission reduction of energy-intensive industries.

• 한국수자원학회논문집
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• 제39권2호
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• pp.99-108
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• 2006

부유사의 거동을 나타내는 데는 이송-확산 방정식이나 이 방정식을 간략화한 식들이 이용된다 이 방정식은 여러 가지 가정하에서 유도되었으나, 이러한 가정에 대해서는 심도있는 검토가 되지 못한 상태에 있다 그 이유는 난류의 측정 자체가 매우 힘들며, 유사가 혼합된 흐름의 경우 물과 유사의 속도를 구별해서 측정하기 매우 힘들기 때문이다. 본 연구는 입자 영상 유속계(PIV, Particle Image Velocimeoy)의 일종인 입자 추적 유속계(PTV, Particle Tracking Velocimetry)를 이용하여 개수로 난류에서 물과 유사의 속도를 측정하는 실험적 연구이다. 측정 결과, 하상에서 어느 정도 떨어진 영역에서는 유사의 속도가 물보다 느린 경향을 보였다. 이 속도 지체의 양은 본 연구의 경우 평균 유속 의 약 $5\%$ 정도였으며, 속도 지체가 최대에 이르는 지점은 $g/h\approx0.05\;(g^{+}=30\~50)$정도인 것으로 나타났다. 유사 입자가 물보다 느리게 이동하는 것은 전적으로 유사의 비중이 물보다 크기 때문으로 보인다. 반면, 하상에 근접한 점성 저층에서는 오히려 유사 입자의 속도가 물보다 빠르게 나타났으며, 이것은 물은 고체 경계면에서 점착 조건에 종속되는 데 반하여, 유사 입자는 점성의 영향을 받지 않기 때문으로 보인다.

• 대한기계학회논문집B
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• 제22권1호
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• pp.61-69
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• 1998

Vapor Axial Deposition (VAD), one of optical fiber preform fabrication processes, is performed by deposition of submicron-size silica particles that are synthesized by combustion of raw chemical materials. In this study, flow field is assumed to be a forced uniform flow perpendicularly impinging on a rotating disk. Similarity solutions obtained in our previous study are utilized to solve the particle transport equation. The particles are approximated to be in a polydisperse state that satisfies a lognormal size distribution. A moment model is used in order to predict distributions of particle number density and size simultaneously. Deposition of the particles on the disk is examined considering convection, Brownian diffusion, thermophoresis, and coagulation with variations of the forced flow velocity and the disk rotating velocity. The deposition rate and the efficiency directly increase as the flow velocity increases, resulting from that the increase of the forced flow velocity causes thinner thermal and diffusion boundary layer thicknesses and thus causes the increase of thermophoretic drift and Brownian diffusion of the particles toward the disk. However, the increase of the disk rotating speed does not result in the direct increase of the deposition rate and the deposition efficiency. Slower flow velocity causes extension of the time scale for coagulation and thus yields larger mean particle size and its geometric standard deviation at the deposition surface. In the case of coagulation starting farther from the deposition surface, coagulation effects increases, resulting in the increase of the particle size and the decrease of the deposition rate at the surface.

• 대한기계학회논문집B
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• 제27권6호
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• pp.813-820
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• 2003

The purpose of this research is to develop the model of turbulence modulation due to the presence of particles in various types of particle-laden flows Available experimental data are surveyed and the dependence of turbulence modulation of carrier-phase on particle size, concentration and. particle Reynolds number are examined. This study takes into account the effect of wake produced by particle, the drag between phases and the velocity gradient in the wake to estimate the production of turbulence. The model of turbulence modulation using the mixing length theory under the assumption of equilibrium flow is proposed. Numerical results show that the model is successful in predicting the characteristics of the particle-laden in various flow conditions both qualitatively and quantitatively.

• 한국대기환경학회지
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• 제12권3호
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• pp.243-254
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• 1996

The main purpose of this study is to investigate the collection efficiency characteristics of a cylindrical ESP. To do that, it is necessary to analyze the electric field, gas flow field, and mechanism of particle movement by numerical simulation based on EHD model. For a gas flow field, Navier-Stokes equation involving the electric source term was solved by SIMPLE algorithm. In case of the electric field, the current continuity and electric field equations were solved by S.O.R. method. The analysis of particle movement was performed on the basis of PSI-CELL model from the Lagrangian viewpoint. The results showed that the influence on the gas flow field by the electric field is almost negligible in a cylindrical ESP. The particle drift velocity $V_P$ toward the collection surface is increased continuously by the electrostatic force due to the rise of particle charge as the particle is moving to the flow direction and the particle size becomes larger. The collection efficiency is to quitely higher with the increase of applied voltage for the same particle size, while becomes smaller as the inlet velocity is increased.

• Journal of Magnetics
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• 제16권4호
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• pp.444-448
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• 2011

In the present study, we separated the marker particles from the suspending particle mixture solution using isotacho-electrophoresis technique, a novel quantitative ionic particle separation method, in the microchannel. A multiple stacking zone of the suspending particle was visualized with variations in electric field strength, pH value and concentration of the ionic solution. In particular, the electrophoretic mobility of ionic particle (fluorescein) was estimated based on the electrophoretic velocity value measured by the particle image velocimetry. As a result, isotacho-electrophoresis zones were clearly visualized as going downstream in the electric field. The particle migration velocity increased proportional to the applied voltage increase; it was also affected by the pH value variations in the ionic solution.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.725-730
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• 2008

In this study, we found out charged particle's deposition characteristic by experiments of $0.5{\mu}m$, $1.0{\mu}m$, $3.0{\mu}m$ size particle's concentration decay. We carried out the experiments on charged particle deposition onto the vertical cleanroom wall panel and some other fundamental experiments. The particle deposition mechanism is consist of sedimentation, convection, diffusion, thermophoresis, electrostatic and so on. Particle size determines mainly working deposition mechanism. The charged particle is made with corona discharge that are constituted field charging and diffusion charging. In addition, this combinational mechanism is called combined charging. The type of corona discharge determines quantity of particle electrical charge. In conclusion, we assumed that quantity of particle electrical charge accelerations deposition velocity onto the vertical cleanroom wall panel and proved it. And we figured out particle's deposition characteristic through compared between our experiment's results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3197-3202
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• 2007

An analysis program for pedestrian flow has been developed to investigate the flow patterns of passenger in railway stations. Analysis algorithms for pedestrian flow based on DEM(Discrete Element Method) are newly developed. There are lots of similarity between particle-laden two phase flow and passenger flow. The velocity component of 1st phase corresponds to the unit vector of calculation cell, each particle to passenger, volume fraction to population density and the particle velocity to the walking velocity, etc. And, the walking velocity of passenger is also represented by the function of population density. Key algorithms are developed to determine the position of passenger, population density and numbering to each passenger. By using the developed program, we compared the simulation results of the effects of the location and size of exit and elapsed time.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.455-462
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• 1999

In this case, we have selected a representative location in the vicinity of large underground structures where they cross a runway and taxiway: measured the effects of the dynamic hammer compaction by distance: analyzed the measured results over a period of time and for many frequencies: and determined the maximum anticipated particle velocity (PV) of vibration, caused by the dynamic hammer, verses distance. In addition, while compacting the hydrofill, we reviewed the impact of subsurface particle velocities, caused by hammer compaction methods, upon newly constructed reinforced concrete underground structures. We have implemented the appropriate technical standards after reviewing domestic and international technical standards concerning allowable vibration velocity appropriate In the many types of underground structures at Inchon International Airport.

• 한국철도학회논문집
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• 제9권3호
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• pp.271-276
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• 2006

Insight into behaviour of pedestrians as welt as tools to assess passenger flow condition is important in such instances as planning and geometric design of railway station under regular and safety-critical circumstances. Algorithm for passenger flow analysis based on DEM (Discrete Element Method) is newly developed. There are lots of similarity between particle-laden two phase flow and passenger flow. The velocity component of 1st phase corresponds to the unit vector of calculation cell, each particle to passenger, volume fraction to population density and the particle velocity to the walking velocity, etc. And, the walking velocity of passenger is also represented by the function of population density. Key algorithms are developed to determine the position of passenger, population density and numbering to each passenger. To verify the effectiveness of new algorithm, passenger flow analysis for the basic models of railway station is conducted.