• 대한기계학회논문집B
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• 제23권2호
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• pp.262-271
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• 1999

A study of aerosol dynamics has been done to obtain axially and radially varying size distributions of particles generated in the Modified Chemical Vapor Deposition process. Heat and mass transfer have also been studied since particle generation and deposition strongly depend on the temperature field in a tube. Bimodal size distributions of particles have been obtained both in the particulate flow and in the deposited particle layer for the first time using the sectional method to solve aerosol dynamics. Variations of geometric mean diameter, geometric standard deviation have been studied for various parameters; flow rates and maximum wall temperature. The comparison between one-dimensional and two-dimensional approaches has also been made.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2000년도 춘계학술대회 논문집
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• pp.219-220
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• 2000

대기 중에 부유하는 입자상 물질을 크기별로 측정하는 기술은 크게 입자의 전기적 특성, 광학적 특성 및 공기역학적 특성을 이용하는 방법이 널리 사용된다. 이중 입자의 공기역학적 특성, 다시 말해 입자의 관성력을 이용한 다단임팩터는 설계 및 제작이 용이하고, 입경별 분리능력이 우수하기 때문에 대기 에어로졸의 입경분포 측정에 가장 많이 사용되고 있다. 본 연구의 목표는 분리입경이 각각 10, 5, 2.5, 1 $\mu\textrm{m}$ 인 상압 4단임팩터를 설계, 제작하여 성능평가하는 데 있다. (중략)

• 한국입자에어로졸학회지
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• 제7권4호
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• pp.123-130
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• 2011

Previous designs of conventional aerodynamic lenses have a limitation of narrow range of focusable particle size, e.g. 30 to 300nm or 3 to 30nm. To enlarge the focusable size range to 30-3000nm, it is necessary to avoid a significant loss of particles larger than 300nm inside the lenses. From numerical simulations on size-resolved particle trajectories, we confirmed that the traveling losses of such large particles could be avoided only when the radial position of particles approaching the orifice lens was near the lens axis. Hence, we designed the lens system consisting of a converging-diverging nozzle and 7 orifices to fulfill the requirement. In particular, the orifices were aligned in a way that their diameters were descending and ascending to the downstream. As a result, 30-2800nm particles can be focused to the particle beam of 0.2mm or less in radius with above 85% transmission efficiency. Even $10{\mu}m$ particles can be focused with 74% of transmission efficiency.

• 드라이브 ㆍ 컨트롤
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• 제21권1호
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• pp.8-15
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• 2024

This thesis investigates the jetting characteristics of an aerosol jet printing (AJP) process as a function of design and operating conditions. The governing equations of the AJP system are derived for experimentation and analysis. To understand the characteristics of the AJP system, it analyzes the jetting characteristics as a function of the flow rate of the carrier gas and the sheath gas, and the variation of the linewidth with the nozzle exit size based on particle tracking. The thesis focuses on computational fluid dynamics (CFD), which is a computer simulation. The particle tracking results obtained by CFD were analyzed using MATLAB. CFD analytical models can be analyzed in environments with different conditions and consider more specific situations than mathematical computational models. The validity of the CFD analysis is shown by comparing the experimental results with the CFD analysis.

• 드라이브 ㆍ 컨트롤
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• 제21권2호
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• pp.8-14
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• 2024

This paper investigates the jetting characteristics of an aerosol jet printing (AJP) process as a function of design and operating conditions. The governing equations of the AJP system are derived for experimentation and analysis. To understand the characteristics of the AJP system, this thesis analyzes the jetting characteristics as a function of the flow rate of the carrier gas and the sheath gas, and the variation of the linewidth with the nozzle exit size based on particle tracking. This thesis focuses on computational fluid dynamics (CFD), which is a computer simulation. The particle tracking results obtained by CFD were analyzed using MATLAB. CFD analytical models can be analyzed in environments with different conditions and consider more specific situations than mathematical computational models. The validity of the CFD analysis is shown by comparing the experimental results with the CFD analysis.

• 한국입자에어로졸학회지
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• 제9권2호
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• pp.39-50
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• 2013

SMPS, APS, ELPI는 실시간으로 대기 중 입자상 물질을 측정할 수 있는 장비로 많은 연구자들에 의해 사용되고 있다. 하지만 측정장비의 특성과 입자 분류 특성에 대한 충분한 이해가 없다면, 단순히 장비에 제공된 소프트웨어의 계산 결과를 여과 없이 그대로 사용할 수밖에 없다. 본 연구에서는 SMPS, APS, ELPI의 측정 메커니즘을 간단히 정리하였고, 전기적 이동도로 입자를 분리하는 SMPS와 공기역학적 거동을 이용하는 APS를 함께 사용하여 입자의 크기분포를 측정할 때 발생할 수 있는 문제점을 고찰하였다. 크기분포 측정결과를 이용해서 무게 농도를 환산하는 과정에서 대기 입자의 입경에 따른 밀도 정보를 제공하는 것이 매우 중요하다는 것을 보였다. 특히, APS 측정결과를 이용하는 경우 무게 농도의 추정 결과가 크게 영향을 받았다. ELPI의 경우 입자 밀도를 정확히 설정하지 않으면 입자의 수 농도에 오차가 크게 발생할 수 있으므로, 정확한 밀도를 설정하는 것이 중요했다. 반면에 ELPI로 대기 중입자상 물질의 무게 농도를 추정하는 경우 밀도가 실제와 다르게 설정되더라도 공기역학적 입경으로 나타내면 총 무게 농도는 수 농도에 비해 상대적으로 영향이 적었다. 향후 SMPS와 APS를 이용하여 시간에 따른 크기 분포 변화와 연간 수 농도와 무게 농도의 변화 추이를 측정하는 연구가 필요하다. 특히, 국내 대기 중입자의 입경에 따른 평균 밀도 혹은 유효 밀도를 측정하여 크기분포와 총 수 농도 혹은 PM2.5나 PM1에 해당하는 무게 농도를 정확하게 계산할 수 있는 데이터 환산 프로그램의 개발도 필요하다. 이와 같은 연구로 시간경과에 따라 변화하는 대기 입자의 오염원에 대한 영향을 규명하는 기초 자료를 얻을 수 있을 것이다.

• 한국입자에어로졸학회지
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• 제9권2호
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• pp.103-110
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• 2013

The electrostatic precipitator (ESP) has been used for degrading atmospheric pollutants. These devices induce the electrical forces to facilitate the removal of particulate pollutants. The ions travel from the high voltage electrode to the grounded electrode by Coulomb force induced by the electric field when a high voltage is applied between two electrodes. The ions collide with gas molecules and exchange momentum with each other thus inducing fluid motion, electrohydrodynamic (EHD) flow. In this study, for the simulation of electric field and EHD flow in ESPs, an open source EHD solver, "espFoam", has been developed using open source CFD toolbox, OpenFOAM(R) (Open Field Operation and Manipulation). The electric potential distribution and ionic space charge density distribution were obtained with the developed solver, and validated with experimental results in the literature. The comparison results showed good agreement. Turbulence model is also incorporated to simulate turbulent flow; hence the developed solver can analyze laminar and turbulent flow. In distributions of electric potential and space charge, the distributions become distorted and asymmetric as the flow velocity increases. The effect of electrical drift flow was investigated for different flow velocities and the secondary flow in a flow of low velocity is successfully predicted.

• 한국입자에어로졸학회지
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• 제19권3호
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• pp.63-76
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• 2023

An electrostatic precipitator (ESP) has a low pressure drop and a high collection efficiency but its collection efficiency can be reduced due to dust accumulation on the collection plates during long-term operations. In order to maintain the initial dust collection efficiency, it is necessary to periodically clean the collection plates. The common cleaning methods are using physical impacts or water sprays. These cleaning methods can lead to damage to the collection plate or generate wastewater. Herein, we implemented an electrodynamic screen (EDS) for ESP cleaning and evaluated its surface cleaning performance of particles. The EDS is an electrostatic system that can electrostatically repel particles on surfaces, allowing it to clean the ESP without causing damage and wastewater generation. Our evaluation included the analysis of the effects of AC voltage characteristics, electrode configuration and environmental conditions on the cleaning performance of the EDS with the aim of achieving effective surface cleaning. It has been demonstrated that activating the EDS cleans up to 65% of the particles on the surface, which indicates about 94% of our target cleaning zone.

• 한국입자에어로졸학회지
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• 제19권4호
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• pp.155-164
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• 2023

APS (Aerodynamic Particle Sizer) and OPC (Optical Particle Counter) have been widely used to real-time measurement of indoor and outdoor aerosols. The APS measures the size distribution based on an aerodynamic diameter, while the OPC uses optical diameter to measure the size distribution of aerosols. Since obtaining a size distribution based on aerodynamic diameter is important to understand aerosol characteristics, lots of researcher had been developed experimental equations which can convert optical diameter into aerodynamic diameter. However, previous studies have conducted repeated experiments on particles having a single diameter. In this study, an experimental method of converting optical diameter into aerodynamic diameter through a single experiment was presented. The collection efficiencies of an axial cyclone were measured using APS and OPC at the same time, and the correlation equation between aerodynamic diameter and optical diameter was driven through a theoretical model. Using the proposed method, the size distribution of NaCl particles measured by OPC showed a high correlation with the size distribution obtained by APS (0.93 of R-squared value). In the tests conducted on ISO A1, A2, and A4 test particles, the converted OPC size distribution tended to be similar to the APS size distribution, and for each of test particles (ISO A1, A2, and A4), the R-squared values for the APS particle size distribution were 0.75, 0.86, and 0.89, respectively.

• 한국기계가공학회지
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• 제18권7호
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• pp.63-70
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• 2019

An electro-aerodynamic lens for improving the performance of virtual impactor has been proposed in this study. ANSYS FLUENT Release 16.1 was used for numerical analysis of virtual impactor with and without the electro-aerodynamic lens, used to collimate the incoming aerosol particles into a particle beam before injecting the particles into the virtual impactor. Particles supplied to the electro-aerodynamic lens were assumed to be highly charged. By using an aerodynamic lens before the virtual impactor, without any electrostatic effect, it was found that the cut-off diameter of the virtual impactor was reduced from $4.2{\mu}m$ to $0.68{\mu}m$ and that the fine particle contamination problem became more serious. However, by employing the combined electrostatic and aerodynamic effects, that is, by applying electric voltage potential to the electro-aerodynamic lens, the cut-off diameter was found to be further reduced to $0.45{\mu}m$ and the fine particle contamination was eliminated.