초소형 휴대폰 광학계의 금형 정밀도가 광학성능에 미치는 영향

예인수,정선환,최성대,현동훈,Ye, In-Soo,Cheong, Seon-Hwan,Choi, Seong-Dae,Hyun, Dong-Hoon 한국생산제조학회 2010 한국생산제조학회지 Vol.25 No.5

In cellphone optical systems, a tiny difference of manufacturing has a strong influence on camera lenses. This study aims to find out the worst result by tolerances come from all parts in optical performance. First, 3D Measure Instrument, Roundness Measure Instrument, and Wavelength Measure Instrument were used for greater precision by making and measuring the parts to see how different from the drawings. It was confirmed that even narrow tolerances could result in defects by assembling. Tolerances in assembly should be concerned as those in parts through the research.

Numerical Investigation of the Spreading and Heat Transfer Characteristics of Ex-vessel Core Melt

예인수,김정은,류창국,하광순,김환열,송진호 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.1

The flow and heat transfer characteristics of the ex-vessel core melt (corium) were investigated using a commercial CFD code along with the experimental data on the spreading of corium available in the literature (VULCANO VE-U7 test). In the numerical simulation of the unsteady two-phase flow, the volume-of-fluid model was applied for the spreading and interfacial surface formation of corium with the surrounding air. The effects of the key parameters were evaluated for the corium spreading,including the radiation, decay heat, temperature-dependent viscosity and initial temperature of corium. The results showed a reasonable trend of corium progression influenced by the changes in the radiation, decay heat, temperature-dependent viscosity and initial temperature of corium. The modeling of the viscosity appropriate for corium and the radiative heat transfer was critical, since the front progression and temperature profiles were strongly dependent on the models. Further development is required for the code to consider the formation of crust on the surfaces of corium and the interaction with the substrate.

전산해석을 이용한 원자로 노심 용융물의 노외 거동 및 열전달 특성 분석

예인수(In-Soo Ye),류창국(Changkook Ryu),하광순(Kwang Soon Ha),송진호(Jin Ho Song) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.4

원자로의 노심 손상에 따른 노심 용융물의 유출시 코어캐쳐라고 불리는 설비를 통해 용융물을 억제하고 냉각시키게 된다. 이 때 노의 노심용융물의 거동은 희생물질과의 반응을 포함한 복잡한 물리적, 화학적 현상에 결정된다. 이 연구는 기존의 용융물 거동 실험결과에 대헤 용융물의 유동과 열전달의 세부적인 특성을 사용코드를 이용해 해석하여 검증함으로써 코어캐쳐의 설계에 활용할 수 있도록 하기 위한 것이다. 단순화된 채널에서 시간에 따르 용융물과 공기의 이상유동과 복사열전달을 VOF 모델과 구분종좌법을 적용하여 비정상상태에서 해석한 결과, 열전달에 따른 용융물 내부의 온도변화 및 이에 따른 점성 변화 등을 예측할 수 있음을 확인하였다. 이러한 접근방식을 기초로 향후 용융물의 조성, 유량 및 온도 등의 조건에 따른 용융물의 거동에 대한 자세한 평가가 필요하다. In the unlikely of nuclear reactor meltdown, the leaked core melt or corium must be contained in a device called core-catcher so that the corium can be cooled and stabilized. The ex-vessel behavior of corium involves complex physical and chemical mechanisms of flow propagation, heat transfer, and reactions with sacrificial substrates. In this study, the detailed characteristics of corium flow and heat transfer were investigated by using a commercial CFD code for VULCANO VE-U7 test reported in the literature. The volume-of-fluid (VOF) model was used to predict the interfacial surface formation of corium and the surrounding air, and the discrete ordinate model was adopted to calculate radiation between corium and the surroundings. It was found that cooling via radiation through the top surface of corium had a dominant effect on the temperature and viscosity profiles at the front of the corium flow.

석탄 가스화시 회분의 임계점도온도 및 플럭스 비율 변화에 따른 벽면 슬래그 거동 특성 분석

예인수(Insoo Ye),류창국(Changkook Ryu),김봉근(Bongkeun Kim) 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.11

In the entrained-flow coal gasifier, coal ash turns into a molten slag most of which deposits onto the wall to form liquid and solid layers. Critical viscosity refers to the viscosity at the interface of the two layers. The slag layers play an important role in protecting the wall from physical/chemical attack from the hot syngas and in continuously discharging the ash to the slag tap at the bottom of the gasifier. For coal with high ash melting point and slag viscosity, CaO-based flux is added to coal to lower the viscosity. This study evaulates the effect of critical viscosity temperature and ash/flux ratio on the slag behavior using numerical modelling in a commercial gasifier. The changes in the slag layer thickness, heat transfer rate, surface temperature and velocity profiles were analyzed to understand the underlying mechanism of slag flow and heat transfer.

석탄 분류층 가스화기 내 유동 및 입자 거동의 특성에 대한 전산유동해석 연구

예인수(Insoo Ye),박상빈(Sangbin Park),류창국(Changkook Ryu),김유석(Youseok Kim) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.43

During gasification in an entrained reactor, coal undergoes a series of complex reactions including drying, pyrolysis, gasification and melting of ash. At elevated operating pressures, the reactor design becomes compact but requires an optimization of fuel and oxidant reactions, temperature, wall heat flux and formation of liquid slag on the membrane wall. Using computational fluid dynamics, this study investigates the progress of coal gasification in the entrained flow reactor for a 300㎿e capacity IGCC. The results show that the nozzle angles of coal and oxidant injection significantly influenced the flow and reaction pattern. The distribution of ash deposition and heat flux onto the wall were very sensitive to the nozzle angle, while the cold gas efficiency did not change noticeably.

석탄 가스화기 내벽의 슬래그 유동 해석 및 열전달 모델링

예인수(In-Soo Ye),류창국(Changkook Ryu),김봉근(Bongkeun Kim) 한국연소학회 2013 KOSCOSYMPOSIUM논문집 Vol.2013 No.12

In a commercial coal gasifier, coal ash turns into slag forming solid and liquid layers on the wall, protecting the membrane tubes from excessive heat flux and damage. In order to overcome the limitation of conventional analytical model for the slagging wall, a comprehensive numerical model was established in this study. The model solves the mass, momentum and energy equation for a liquid slag layer adopting the control volume method on a 2-dimensional cylindrical system. The performance of the model was evaluated using an Excel/VBA code for various operating conditions of heat flux and slag deposition from the syngas. The model reasonably predicted the thickness, velocity, temperature of the slag layers, and resultant heat flux to the membrane wall. Further study is required to combine this model with the gas-side model for a gasifier and to investigate the detailed gas-slag interactions.

전산해석을 통한 원자로 노심 용융물의 채널 내 퍼짐 및 열전달 특성 분석

예인수(In-Soo Ye),류창국(Changkook Ryu),하광순(Kwang-Soon Ha),송진호(Jin-Ho Song) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

In an unlikely accident of nuclear reactor melt down, the leaked core-melt or corium needs to be contained in a device called core-catcher for cooling and stabilization. The ex-vessel behavior of corium involves complex physical and chemical mechanisms of flow propagation, heat transfer and reactions with sacrificial materials. As part of design development of a core-catcher, this study investigated the detailed characteristics of corium flow and heat transfer using a commercial CFD code for experimental data of corium spreading available in literature. The volume-of-fluid (VOF) model was applied to predict the interfacial surface formation of corium and surrounding air, and the discrete ordinate model was adopted for prediction of radiation from the surface of corium to the surroundings. It was found that the effect of cooling by radiation through the top surface of corium was dominant on the temperature and viscosity profiles at the corium front.

분류층 석탄 가스화기 내 임계점도온도의 변화에 따른 슬래그 층의 영향 연구

예인수(Insoo Ye),류창국(Changkook Ryu) 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.5

In the gasification, burnout coal particles converts to molten ash called slag with hot gas atmosphere. The slag layers which are accumulated slag particles and consist of solid and liquid phase prevent damages from hot synthesis gas and particles, and liquid slag flows down for continuous coal ash discharge. Critical viscosity temperature (Tcv) is the interface point determined by flowability between two slag layers. Higher Tcv with coal affects thick slag layer onto the gasifier wall, while for the lower Tcv, the layers may become thin or liquid flow only except to fixed solid phase. This study evaluates the theoretical influences of Tcv, critical viscosity and flux addition on the slag behavior in a commercial coal gasifier using a numerical model. The results showed that a lower slag Tcv led to an exponential decrease in the solid slag thickness owing to an increased wall heat flux and a reduced temperature difference between the slag and the coolant. However, liquid slag thickness was relatively small.

휴대폰 카메라 모듈의 조립공차 개선 시스템에 관한 연구

예인수(In-Soo Ye),정선환(Seon-Hwan Cheong),최성대(Seong-Dae Choi),현동훈(Dong-Hoon Hyun) 한국기계가공학회 2010 한국기계가공학회지 Vol.9 No.5

Tolerance analysis is one of the most important processes to improve the image quality of products. High resolution camera module for mobile phones needs precision assembly technology since the module becomes smaller and thinner. This paper will focus on the unit tolerance and the assembly tolerance which can affect the performance of the module. Lens shading and relative illumination were used to evaluate the optical axis scatter for each component on camera and estimate the assembly yield rate based on the evaluation result. A program was developed to analyze the impact on optical axis by each module, then to optimize the dimensions and tolerance for reducing the scatter of optical axis assembly. Through the simulation, though a rate of relative illumination was declined in where optical axis is displaced 100㎛ from sensor center, MTF performance is not influenced by increasing in optical axis displacement. It was seen that assembly yield was improved in result of simulation after correcting optical axis tolerance.

초소형 휴대폰 광학계의 금형 정밀도가 광학성능에 미치는 영향

예인수(In-Soo Ye),정선환(Seon-Hwan Cheong),최성대(Seong-Dae Choi),현동훈(Dong-Hoon Hyun) 한국생산제조학회 2010 한국생산제조학회지 Vol.19 No.5

In cellphone optical systems, a tiny difference of manufacturing has a strong influence on camera lenses. This study aims to find out the worst result by tolerances come from all parts in optical performance. First, 3D Measure Instrument, Roundness Measure Instrument, and Wavelength Measure Instrument were used for greater precision by making and measuring the parts to see how different from the drawings. It was confirmed that even narrow tolerances could result in defects by assembling. Tolerances in assembly should be concerned as those in parts through the research.