• 한국분무공학회지
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• 제1권1호
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• pp.76-84
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• 1996

The nozzle geometry and up-stream inject ion condition affect the characteristics of flow inside the nozzle. such as turbulence and cavitation bubbles. Flow details in fuel nozzle orifice with sudden contraction of cross sectional area have been investigated both experimentally and numerically. The measurements of velocities of internal flow in a scaled-up nozzle with different length to diameter rat io(L/d) were made by laser Doppler velocimetry in order to clarify the effect of internal flow on the characteristics of fuel spray. Mean and fluctuating velocities and discharge coefficients were obtained at various Reynolds numbers. The turbulent intensity and turbulence kinetic energy in a sharp inlet nozzle were higher than that in a round inlet nozzle. Calculations were also performed for the same nozzles as scaled-up experimental nozzles using the SIMPLE algorithm. External spray behavior under different nozzle geometry and up-stream flow conditions using Doppler technique and visualization technique were also observed.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.73-76
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• 2006

액체 로켓엔진에서의 고주파 연소불안정 제어를 위한 수동 안정화 제어 기구로 음향공을 적용하여 감쇠 효과의 적합성을 검증하였다. 음향공의 기하학적 형상에 따른 음향 감쇠 효과를 비교하기 위하여, 주요 설계 변수를 변화시킨 음향공 모델에 대해 유해 공진주파수 감쇠 효과를 정량적으로 비교, 분석하였다. 선형음향해석과 실험적 방법 모두 만족할만한 일치성을 나타내었으며, 오리피스 입구 면적이 가장 크거나 오리피스 길이가 가장 짧은 경우에서 감쇠 효과가 가장 크게 나타났다. 결론적으로 음향공을 이용한 최적의 음향공 제어를 위해서는 음향공 부피를 고려한 최적기 음향공 설계가 절대적으로 필요함을 입증한다.

• 대한기계학회논문집B
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• 제27권4호
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• pp.484-495
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• 2003

This study investigates the flow characteristics of fuel droplets between twin spray for the 4-hole injector used a 4-valve gasoline engine. The injectors for this study were the three types of 4-hole gasoline injector in which orifice diameter was 0.24mm. The spray behavior of twin spray was investigated by means of visualization employed stroboscope. A PDPA system was employed to simultaneously measure the size and velocity of fuel droplets. The 3 dimensional mean velocities. droplet size distributions, SMD and joint probability density function of velocity and droplet size are analyzed at the center of the spray and the center region of twin spray. As a result, the configurations of injector exit such as orifice interval and length of outlet, are very important factors that affect the flow characteristics of fuel droplets at the center region of twin spray.

• 한국분무공학회지
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• 제16권2호
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• pp.90-96
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• 2011

Atomized liquid jets from the washing nozzle which configured with recirculation chamber for cleaning hot-zone area are accelerated and impinged on the head lamp surface. Cleaning efficiency of head lamp can be increased with injecting washing fluids into the hot-zone area. Experimental and numerical studies with various design parameters were executed to reveal the relations between internal geometry and internal flow in the washing nozzle. Spray structures were fitted with each of the head lamp surfaces and spray nozzles were optimized to the spray pattern. The recirculation chamber induces a recirculation flow and can be decreased the pressures perturbation inside the chamber. Orifice determines the mass flow rate. When the diameter of orifice is excessively large, it showed an unstable spray pattern. As a nozzle exit angle increases, density distributions are separated with two section. Also, as a protrusion length of nozzle exit increases, spray patterns are spread into a large area and density distributions showed unstable trend.

• 한국추진공학회지
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• 제12권5호
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• pp.9-17
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• 2008

액체추진제 추력기 인젝터로부터 발생하는 분무의 분열과 확산거동을 파악하기 위해 이중모드 위상 도플러속도계(DPDA)를 사용하여 분무액적의 준3차원적 공간분포를 계측하고 도시한다. 분무는 27.6 bar의 분사압력 조건에서 길이-직경비가 1.67인 노즐 오리피스로부터 지면에 수직으로 분사된다. 분무 액적의 수직 및 수평방향 평균속도, SMD, 그리고 체적유속은 분무의 상류/중심에서 하류/외곽으로 이동함에 따라 분무분열에 의해 그 크기가 감소한다. 분무특성 인자들의 대칭적 분포 경향에도 불구하고 그들의 절대값은 노즐 오리피스 중심축을 기준으로 대칭이 아니다.

• Design & Manufacturing
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• 제9권2호
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• pp.25-29
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• 2015

This paper presented characterization of spray velocity and angle of spray nozzle systems for cosmetic products. Diameter and length of nozzle orifice were chosen as shape factors of the spray system. Spray orifice of the spray pattern is a factor influencing the quality of the product. Fluid analysis was conducted by using "Fluent" to obtain spray angle and velocity. RSM (Response Surface Method) was used to approximate the relationship between these 2 factors and spray characteristics. To evaluate the proposed method, experimental work with existing was conducted and good agreement between simulation and experimental results.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.35-38
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• 2011

본 연구에서는 액체로켓엔진에서 발생되는 고주파 연소불안정 문제를 제어하기 위한 수동제어 장치인 헬름홀쯔 음향공의 형상변화에 따른 음향공의 감쇠 특성에 대하여 연구하였다. 오리피스의 지름과 길이가 일정한 헬름홀쯔 형상 음향공의 지름을 점차 줄여 음향공의 형상이 헬름홀쯔 음향공의 오리피스 지름과 같은 지름을 가진 쿼터웨이브 형상으로 변화 할 때 각 단계별 튜닝되는 음향공의 부피는 작아지지만 그에 따른 음향공의 음향 감쇠 효과는 거의 일정하다는 것을 상온 음향실험과 수치해석을 비교 하면서 그 특성을 확인 하였다.

• 대한기계학회논문집A
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• 제32권10호
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• pp.831-835
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• 2008

We present a continuous electrical cell lysis chip, using a DC bias voltage to generate the focused high electric field for cell lysis as well as the electroosmotic flow for cell transport. The previous cell lysis chips apply an AC voltage between micro-gap electrodes for cell lysis and use pumps or valves for cell transport. The present DC chip generates high electrical field by reducing the width of the channel between a DC electrode pair, while the previous AC chips reducing the gap between an AC electrode pair. The present chip performs continuous cell pumping without using additional flow source, while the previous chips need additional pumps or valves for the discontinuous cell loading and unloading in the lysis chambers. The experimental study features an orifice whose width and length is 20 times narrower and 175 times shorter than the width and length of a microchannel. With an operational voltage of 50 V, the present chip generates high electric field strength of 1.2 kV/cm at the orifice to disrupt cells with 100% lysis rate of Red Blood Cells and low electric field strength of 60 V/cm at the microchannel to generate an electroosmotic flow of $30{\mu}m/s{\pm}9{\mu}m/s$. In conclusion, the present chip is capable of continuous self-pumping cell lysis at a low voltage; thus, it is suitable for a sample pretreatment component of a micro total analysis system or lab-on-a-chip.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.158-165
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• 2005

KOGAS(Korea Gas Corporation) has about a hundred of local stations to supply natural gas to the city gas companies and the power stations. As some severe flow fluctuation phenomena are observed in several governor stations, the investigation about the reasons and factors which are relating to flow fluctuation has been started. Some field surveys hav been carried out and experimental studies have been performed to find the fluctuation mechanism. As a result, it is found that the flow fluctuation is related with the length of straight pipe in front of the meter, the size of the header pipe and the variation of demand at the city gas company and the power station. Furthermore. it is also proved that both the length of the transmitter cable and the status of the coating of signal transmission cable do not affect flow fluctuation, but the measurement range of the differential pressure transmitter influences flow fluctuation. On the other hand, as the averaging the flow fluctuation is converged to less than 0.1 % in almost all of the cases, it is concluded that the quantity of flow fluctuation do not relates to metering accuracy directly.

• 농약과학회지
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• 제16권4호
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• pp.282-287
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• 2012

본 실험은 배부식 분무기 노즐 종류를 달리하여 농약을 살포하였을 경우 작물 중 농약잔류량에 미치는 영향을 구명하기 위해 수행하였다. 배부식 인력분무기의 2구 디스크형 노즐과 배부식 동력분무기의 2구 선형노즐을 분구형상에 따라 I형은 분구가 하나, II형은 분구가 둘, III형은 분구가 셋으로 3가지 유형으로 구분하여 분무입경과 시간당 분무량을 조사하였다. 선형노즐 II형(상표명: D-3)이 압력 $1.1{\pm}0.2$ MPa에서 분무입경 $76{\mu}m$, 단위 시간당 약제 살포량 2.4 L/min.으로, 선형노즐 II형 (상표명: D-35)가 압력 $1.0{\pm}0.2$ MPa에서 분무입경 $90{\mu}m$, 단위 시간당 약제 살포량 2.6 L/min.으로 적정하다고 판단되었다. D-3의 분구 크기는 0.65 mm length ${\times}$ 0.45 mm width이고 D-35의 분구 크기는 0.62 mm length ${\times}$ 0.46 mm width 이였다. 들깻잎을 대상으로 노즐별 imidacloprid의 잔류량 차이를 비교하여 유의수준 5%에서 잔류량의 차이가 있었다. 디스크형 노즐과 선형노즐 I형이 $3.76{\sim}3.92mg\;kg^{-1}$으로 선형노즐 II형과 III형의 $4.52{\sim}4.92mg\;kg^{-1}$보다 잔류량이 적었다. 분무 노즐을 달리하여 농약살포시 들깻잎 중 잔류량의 차이가 있다고 판단되었다.