• 한국분무공학회지
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• 제6권1호
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• pp.44-51
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• 2001

The distributions of the SMD and behavior of 2% $NH_4H_2PO_4$ spray discharged from a fan-spray twin fluid type nozzle are measured and observed. The spray characteristics, according to the variation in the applied voltages, are demonstrated using the PMAS (particle Motion Analysis System) and the CCD camera, respectively. The preliminary experiments are executed to select an optimum condition for solidifying a galvanized coating layer in the uncharged condition before carrying out the main experiments. The liquid and air pressure of $0.07kgf/cm^2\;and\;0.15kgf/cm^2$ can be considered the optimum conditions to use in the main experiment. As the applied voltage increases, the frequent range of relatively large droplets diminishes. Thus, the distributions of drop diameter in the charged spray are more uniform than these in the uncharged condition. This is explained by recognizing that repulsive forces among droplets with the charges of the same sign cause them to be uniform.

• 한국레이저가공학회지
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• 제2권3호
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• pp.11-18
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• 1999

This paper describes the weldability of carbon steel and stainless steel using 5㎾ $CO_2$ laser system with nearly multi-mode beam and a parabolic focusing mirror. In the laser welding of steels, major welding parameters are focal point, travel speed, beam power, shield gas and gap tolerance, etc.. Two kinds of gases(Ar, He) were used as a assist gas and supplied through the external nozzle. It is very important for optimum condition to remove plasma plume which absorbs laser beam and to obtain deep penetration and sound weld bead. Bead-on-plate welding tests were carried out for the experiments. Penetration data were obtained with various welding parameters and the effects of welding parameters were discussed. Butt welding tests were performed with various conditions. Only the optimum laser parameters assured good weld quality As a result of this study, We achieve the fundamental weldabilities using a high power $CO_2$ laser for carbon steel and stainless steel.

• Journal of Advanced Marine Engineering and Technology
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• 제28권5호
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• pp.818-826
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• 2004

The spray-induced mixing characteristics and thermal decomposition of aqueous urea solution into ammonia have been studied to design optimum sizes and geometries of the mixing chamber in SCR(Selective Catalytic Reduction) system. The cold flow tests about the urea-injection nozzle were performed to clarify the parameters of spray mixing characteristics such as mean diameter and velocity of drops and spray width determined from the interactions between incoming air and injected drops. Discrete particle model in Fluent code was adopted to simulate spray-induced mixing process and the experimental results on the spray characteristics were used as input data of numerical calculations. The simulation results on the spray-induced mixing were verified by comparing the spray width extracted from the digital images with the simulated Particle tracks of injected drops. The single kinetic model was adopted to predict thermal decomposition of urea solution into ammonia and solved simultaneously along with the verified spray model. The hot air generator was designed to match the flow rate and temperature of the exhaust gas of the real engines The measured ammonia productions in the hot air generator were compared with the numerical predictions and the comparison results showed good agreements. Finally, we concluded that the design capabilities for sizing optimum mixing chamber were established.

• 한국추진공학회지
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• 제9권1호
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• pp.1-8
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• 2005

설계단계에서 수행되는 액체로켓엔진의 추력실 형상설계와 성능예측을 위하여 화학평형을 고려한 축대칭 압축성 해석코드를 개발하였다. 사용자의 편리함과 효율성에 중점을 두었으며, 형상파라미터의 입력값에 따라 자동으로 격자를 생성하고 연소실 조건은 추진제 조합, 연소압 그리고 혼합비를 지정함으로서 내부에서 계산하게 된다. 따라서 설계자는 추력실 형상 및 작동조건을 변화시켜 각각의 설계변수가 추력성능에 미치는 영향을 빠르고 손쉽게 파악할 수 있도록 하였다. CEA의 결과, JPL 노즐의 실험결과, 두 종류의 LRE 실제 엔진 자료, 그리고 KSR-III의 설계점 및 탈설계점 연소시험결과와 비교함으로서, 다양한 측면에서 해석코드의 정확도와 적용성을 평가하였다.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권4호
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• pp.196-205
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• 2005

In this paper, recent research trend on heat transfer in impinging jet is reviewed. We focused on submerged jet that air issued into air or liquid issued into liquid. To control and enhance the heat transfer in single jet, researchers have performed a lot of experiments by considering the nozzle geometry, impinging surface and active method such as jet vibration, secondary injection and suction flow. The studies on multiple jet have been mainly focused on finding out the optimum condition and on investigating many different factors concerned with application condition (crossflow, rotation and geometry etc.) and combined techniques (rib turbulator, pin fin, dimple and effusion hole etc.). All most experiments showed the detailed heat transfer data by using liquid crystal method, infrared camera technique and naphthalene sublimation method. Many numerical calculations have been performed to investigate the flow and heat transfer characteristics in laminar jet region. Various turbulence models such as $k-\varepsilon-\bar{\nu^2}$, modified $k-\varepsilon-f_{\mu}$ were applied to the calculation for turbulent jet and the predicted results showed a good agreement with the experimental data. Although a lot of studies on impinging jet have performed consistently up to recently, further studies are still required to understand the flow and heat transfer characteristics more accurately, and to give a guideline for optimum impinging jet design in various applications.

• 한국대기환경학회지
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• 제30권4호
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• pp.339-349
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• 2014

$CO_2$ emission has been gradually increased due to rising fossil fuel use. A gliding arc plasma scrubber (GAPS) was proposed to destruct $CO_2$. For optimum design of GAPS, a CFD analysis has been conducted in different configuration for the system. The parameters considered included gas injection velocity at the nozzle and gas flow rate to gap between electrodes. The reactor configuration affected velocity fields which caused changes in the mixture fraction and the retention time. The mixing effect of $CO_2$ and supplied gas ($CH_4$ and steam) was enhanced by installing a orifice baffle. This revealed that the orifice baffle is effective in $CO_2$ conversion by positioning the reactants in the gas into the center of plasma discharge.

• 한국추진공학회지
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• 제2권2호
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• pp.99-107
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• 1998

ASE120 엔진 연소기에 쓰이는 벤츄리(venturi)형 예혼합기의 혼합성능을 시험 평가하였다. 이 시험에서는 가스연료 대신 찬공기를 주입하고 혼합공기의 온도를 측정함으로 혼합정도를 계산하였다. DOE 기법을 사용하여 시험변수 matrix를 구성하고 시험결과를 분석하여 최적의 변수조합을 가지는 형상을 도출하였다. 선정된 형상에 대하여 확인시험이 수행되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.215-217
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• 2006

본 논문에서는 잉크젯 프린팅 기술을 이용한 산업용 FPCB의 패턴형성을 위한 잉크드롭의 최적형성을 연구목적으로 하였다. 이를 위하여 압전헤드에 대한 구동특성을 해석하였으며 드롭형성을 위한 전압파형의 크기, 펄스폭, 기울기(감속)조정을 통하여 잉크드롭을 최적으로 형성하도록 제어기(FPGA)를 구성하였으며 실험결과를 통하여 잉크의 최적형성 과정을 확인할 수 있었으며 잉크 드롭시 1[mm]에 ${\pm}10$[um]의 드롭오차를 ${\pm}2$[um]까지 감소시켜 50[um]패턴을 프린트하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.680-683
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• 2004

This study is to obtain basic data concerned with properties of foam for foamed concrete and foaming method. Main factors of this study are types of foaming agents, temperature of solution with foaming agents, and types of foam generator. Testing items are size distribution of foam, foaming ratio to solution, and stability of foam. The results of this study were shown as follow. It is optimum condition of foam generator that length/diameter of foaming tube is 2.0, bead size within foaming tube is $4\~6mm$, and nozzle size of foaming tube is 10mm. AES and AOS are good results to produce high quality foam, and stability of foam is good in foaming temperature of $20^{\circ}C$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.413-416
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• 2000

The spent fuel skeleton is processed in the cutting processing after compacting. If the cutting length is processed in the same interval length. The spent fuel skeleton is stayed on the connection of bottom nozzle and guide tube. In the case, because the compressive stress is loaded along the length, the guide tube is generated the buckling stress and the deforming. But the deformed guide tube interrupted the guide tube inserted through compressive room. therefore, it is experimented for the optimum buckling stress and the preventing of guide deformed. This paper is predicted the all over buckling stress of the spent fuel skeleton by using experiment. The guide of Spent fuel skeleton have buckling characteristics of the medium column. The experiment and analysis is conducted by the comparing among the equation of Euler, Johnson and Engresser. The fittest one of method is Engresser equation.