• 한국분무공학회지
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• 제9권2호
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• pp.24-33
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• 2004

The effect of the working fluid flow conditions and nozzle geometry on the spray performance of a twin-fluid nozzle used in Selective Catalytic Reduction is investigated experimentally. The liquid pressure is varied in the range of 0.3atm to 1.5atm and the air pressure is varied from the 0.5atm to 3.0atm. relative position between liquid nozzle(internal nozzle) and air nozzle(external nozzle) tip changes front 1mm inside the air nozzle to 1mm outside the air nozzle. The orifice diameter of the air nozzle is varied with 5mm. 6mm and 7mm. Spray visualization is realized with CCD-Camera. SMD(Sauter Mean Diameter) and mean particle velocities are measured by PDPA(Phase Doppler Particle Analyzer) under various experimental conditions. The measuring point is 300mm away from the nozzle tip in the downstream spray. The experimental results are that spray angle is depended air flow rate because nozzle diameter, air pressure and nozzle tip relative positions are related air flow rate. SMD is depended air flow rate and water flow rate. Also, SMD is increased when water flow rate is bigger. SMD is decreased when Air flow rate is bigger.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.508-513
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• 2003

Experiments are performed to investigate the detailed structure of underexpanded twin jet impinging on a perpendicular flat plate. The major parameters, such as nozzle operating pressure and nozzle spacing, are varied to create different jet flow fields resulted from the complicated interactions of the twin jets. From the surface pressure measurements and shadowgraphs taken by schlieren optical system, the jet structure is strongly dependent on the nozzle operation pressure and the spacing. The results obtained show that the closer nozzle spacing may induce to decrease the diameter of the Mach disk within the first shock cell in the underexpanded twin jet. With the increasing nozzle operating pressure and decreasing the nozzle spacing, a new shock wave appears at the entrainment region between the two jets, due to the enhancement of mixing effect of the both jets. The closer nozzle spacing makes the overall impinging pressure level higher, while severe pressure oscillation along the axis of symmetry. Furthermore it is recommended the wider spacing to obtain higher thrust under the present experimental conditions.

• 한국화재소방학회논문지
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• 제31권4호
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• pp.59-64
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• 2017

본 연구에서는 2유체노즐의 액체풀 (Liquid pool) 화재 소화 성능에 대하여 선행적인 검토를 수행하였다. 액체풀 화재의 경우, 에탄올 (Ethanol) 1200 ml를 이용하였으며, 물 공급 유량은 632 ml/min, 공기의 공급 유량은 40 l/min과 70 l/min으로 설정하였다. 본 실험조건에서 2유체노즐을 이용하여 화재 소화 실험을 수행하였고, 2유체노즐의 분사 특성 (액적 크기 및 유량 분포)을 측정하였다. 실험 결과, 공기의 유량이 많은 조건에서 빠른 시간 안에 성공적으로 화재를 소화할 수 있었고, 이러한 결과에 대하여 가시화 및 2유체노즐 분사 특성 데이터를 토대로 분석하였다. 또한, 기존 연구의 일부 결과와 비교를 통하여, 2유체노즐이 단일유체노즐에 비해 더욱 작은 물의 유량 조건에서도 화재 소화를 할 수 있을 가능성이 있음을 확인하였다.

• 한국기계가공학회지
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• 제10권3호
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• pp.60-66
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• 2011

In the present investigation, experimental studies were conducted on the fire suppression performance of twin-fluid water mist spray which is subjected to thermal radiation in a closed space. Downward-directed water-mist sprays, interacting with an under kerosene pool fire, were investigated in a test facility. The mass mean diameter of water-mist droplets were measured by PMAS under various flow conditions. The developed twin-fluid water mit spray nozzle satisfied the criteria of NFPA 750, Class 1. The mechanism of fire suppression by fine water mist was concluded to be the cooling of the fire surface which leads to the suppression of fuel evaporation. It was proved that the automatic twin-fluid water mist spray system under lower pressures could be applied to an industrial facilities.

• 대한기계학회논문집
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• 제17권7호
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• pp.1841-1850
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• 1993

A simplified one-dimensional analysis has been performed to predict the local pressure distributions in Y-Jet twin-fluid atomizers. Fluid compressibility was considered both in the gas(air) and two-phase(mixing) ports. The annular-mist flow model was adopted to analyze the flow in the mixing port. A series of experiments also has been performed; the results show that the air flow rate increases and the liquid flow rate decreases with the increase of the air injection pressure and/or with the decrease of the liquid injection pressure. From the measured injection pressures and flow rates, the appropriate constants for the correlations of the pressure loss coefficients and the rate of drop entrainment were decided. The local pressures inside the nozzle by prediction reasonably agree with those by the experiments.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.943-948
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• 2000

The Twin-fluid Swirl Nozzles are used in many parts of the industry to produce homogeneous spray. This study is to investigate the effects of outer air swiller and inner water swiller on atomization of liquid.. The experiment was carried out with increasing air-flow rate at constant liquid-flow rate and with changing outer air swiller angle and inner water swiller angle. A Particle Dynamics Analyzer(PDA) was used to measure drop size, mean and ms values of axial velocity, number density and Sauter mean diameter(SMD). The axial mean velocity and SMD of droplets were measured along the center line and radial directions. It was found that the higher air flow-rate resulted in the smaller Sauter mean diameter of liquid spray and the higher axial mean velocity of droplets. This experimental results will be conveniently used for the preliminary design stage of twin-fluid nozzle development.

• 대한기계학회논문집B
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• 제21권8호
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• pp.1056-1067
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• 1997

Present study visualized flow pattern and investigated spray characteristics of twin-fluid atomization with converging-diverging nozzles. Particle sizes were measured by using the Malvern particle analyzer, and the radial size distributions were evaluated by using the tomographic transform technique. The results show that the SMD generally increases in the radial direction at a prescribed liquid flow rate and the increasing rate in the SMD becomes gradual as atomizing gas pressure increases. The SMD decreases as the liquid flow rate increases at a fixed GLR (gas/liquid mass ratio). The atomization performance of the protrusion-type nozzle turned out to be superior to that of the flush-type. However, in the case of the protrusion-type, flow separation occurs outside the liquid delivery tube when the pressure at the gas nozzle chamber is high enough, which may deteriorate the atomization performance.

• 한국분무공학회지
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• 제1권1호
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• pp.21-27
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• 1996

This experimental study was to investigate spray angles and drop sizes in an external mixed twin-fluid swirl jet nozzle. Twin-fluid swirl jet nozzle with swirlers designed four swirl angles such as $0^{\circ},\;22.5^{\circ},\;45^{\circ},\;64.2^{\circ}$ was employed. A PDA system was utilized for the measurement of drop size and mean velocity. Water and air were used as the working fluids in this experiment. The mass flow rate of water was fixed as 0.03 kg/min, and air flow rates were controlled to have the air/liquid mass ratio from 1.0 to 6.0. As a result, swirl angle controlled to spray angles and drop sizes. It was found that swirl angle was increased with spray angle and with decreased SMD. However, the effect of swirl angle was reduced at large air/liquid mass ratio(Mr=6.0).

• 한국화재소방학회논문지
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• 제33권3호
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• pp.37-43
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• 2019

본 연구에서는 2유체노즐을 이용하여 에탄올 풀화재(Ethanol pool fire) 소화 실험을 수행하였다. 화원 면적이 5.027 × 10^-3 ㎡와 1.131 × 10^-2 ㎡(연료팬 직경은 각각 80 mm와 120 mm)를 대상으로 하였고, 화재 소화 실험 시 2유체노즐로의 공급 유량의 경우 물은 156-483 g/min, 공기는 20-70 L/min 조건이었다. 화원 면적이 증가하면 열방출률도 증가하였고, 화원 면적이 5.027 × 10^-3 ㎡와 1.131 × 10^-2 ㎡일 때의 열방출률은 각각 1.01 kW와 5.51 kW로 측정되었다. 본 실험 영역에서 2가지 화원 면적 조건 모두, 물 공급 유량 조건과는 상관없이 공기 공급 유량이 40 L/min 이상의 조건에서 소화가 가능하였다. 소화 소요 시간 및 물 소모량의 경우 모든 물 공급 유량 조건에서 공기 공급 유량이 증가함에 따라 감소하는 경향이 관찰되었고, 공기 공급 유량이 비교적 많은 영역(예를 들면, 약 50 L/min 이상)에서 소화 소요 시간은 약 23 s, 물 소모량은 약 185 g 이내로 나타났다. 본 연구 결과와 단일유체노즐을 이용한 기존 연구 간 단위 열방출률 당 물 소모량 비교를 통하여, 2유체노즐이 단일유체노즐에 비해 더 적은 물 소모량으로 소화가 가능할 수 있음을 확인하였다.

• 한국분무공학회지
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• 제22권2호
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• pp.96-102
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• 2017

In order to reduce the NOx, SCR technology is most suitable. In this study, we focused on studying the injector part of urea-SCR system. When stoichiometric 1 mole of urea is injected, 2 moles of $NH_3$ are created. $NH_3$ causes a SCR reaction by reacting with NOx. However, urea is decomposed by the side reaction of coming out HNCO, deposit formation is formed. In this study, it was to design a nozzle that can spray the optimal spray flow rate. Test nozzle used in this experiment is efferverscent type. The result of the experiment, liquid flow rate was confirmed to be that they are dominated by the exit orifice diameter. The area ratio is defined by ratio of the area of exit orifice hole and that of aerorator. The droplet size was measured by varying the area ratios. In addition, it was also confirmed that there is no change of the liquid flow rate and air flow rate to change the aerorator at the same exit orifice. Further, It was confirmed that the droplet size was relatively uniform even though the area ratio was different. Finally, there is little change in the SMD that air flow rate increases in 0.3 or more ALR.