• Journal of Advanced Marine Engineering and Technology
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• 제25권4호
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• pp.904-911
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• 2001

The fuels of water-in-oil emulsion have a potential of reducing PM(Particulate Matter) and NOx emissions, and increasing combustion efficiency in the furnaces and the burners. For making the most of the beneficial of the secondary atomization due to the microexplosion, the water droplets distributed in the oil must have the optimal sizes. The purpose of this paper is to investigate the water droplet size distribution characteristics of the different types of the static mixers. For analysis the size distribution characteristics efficiently, image analysis system wes constructed and an appropriate image processing algorithm was developed. Two kinds of static mixers: Kenics type and RF type, were tested. As a results, RF type static mixer shows a better characteristics in the mean drop size, particularly in the condition of high water content.

• International Journal of Korean Welding Society
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• 제4권1호
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• pp.15-22
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• 2004

Metal transfer behavior of three shielded metal arc welding electrodes, AWS El1018, E6013 and E6010, were investigated through the characterization of size distribution of droplets and measurement of arc voltage signals. Of the three electrodes, Ell018 electrode showed the largest droplet size with the smallest amount of spatter, while E6010 electrode showed the smallest droplet size with the largest amount of spatter. Even though Ell0l8 electrode showed a good agreement between the frequencies of voltage drop in FFT processed voltage signals and the transfer rate of droplets, E6013 and E6010 electrodes showed weaker correlation because of their dominant explosive transfer behavior. The type of cathode used and electrode baking time also influenced the metal transfer behavior. Compared to bead-on-plate welding using steel plate as a cathode, welding on a water-cooled copper pipe showed less short-circuiting and higher melting rate in all electrodes because of higher arc potential and/or anode drop. When baked for a long time, E6010 electrode showed much more stable arc with less short-circuiting and explosion due to the loss of gas formation ingredients.

• 한국항공우주학회지
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• 제40권10호
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• pp.862-871
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• 2012

96% 과산화수소와 케로신을 추진제로 사용하는 500 N 급 로켓엔진에 대하여 추진제의 분무, 기화, 혼합, 연소를 포함하는 수치해석을 수행하였다. 1/6 조각의 연소실을 격자로 생성하였으며, 세 가지 종류의 액체상 추진제(케로신, 과산화수소, 물)가 속이 빈 콘 형태로 공급되는 분무를 모사하였고, Rosin-Rammler 함수에 따른 액적크기 분포를 가정하였으며, 연소 해석에는 와류소산모델을 사용하였다. 본 계산에서는 작은 연소실 크기, 그리고 과산화수소 및 물의 큰 잠열 및 비열로 인하여 평균 액적 크기 변화에 따라 큰 성능의 차이를 나타냈으며, 평균 액적 크기가 30 micron인 경우 가장 좋은 추진성능을 보여주었다.

• 한국화재소방학회논문지
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• 제29권5호
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• pp.29-33
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• 2015

본 연구에서는 노즐의 형상변화에 따라서 방사유량, 살수분포 그리고 액적크기를 측정하였다. 이를 위해서 중심부 직경이 6.0 mm이고 반지름 방향 방사각도가 $142^{\circ}$와 $148^{\circ}$인 이중 구조의 미세 물분무 노즐(LPN142, LPN148) 형상을 제작하여 UL2167 시험규격에 의해서 살수분포와 분사거리의 관계를 정량화하였다. Hellium-Neon 레이져에 의한 광학적 분석 방법을 적용하여 방사유량 변화에 따라서 웨버 수와 액적 크기 그리고 방사각도에 관한 경험식을 구하였으며, 전달 방정식의 주요인자인 소멸 항과 액적크기의 상관관계를 분석하였다. 그 결과 이중 구조의 미세 물분무 노즐은 최소허용 유량범위가 결정된 경우 작동압력, 분사거리, 액적 직경을 예측하여 화재특성을 분석함으로써 노즐 선정이 가능할 것으로 사료된다.

• 대한기계학회논문집B
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• 제26권4호
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• pp.604-613
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• 2002

Generation characteristics of electrospray droplets for highly viscous liquid have been investigated by measuring size distributions of droplets emitted from the Taylor cone using glycerol solutions with various conductivities. Because of very small volatility of glycerol, droplet sizes can be measured by an aerodynamic size spectrometer (TSI Aerosizer DSP) with negligible evaporation of droplets. For highly conducting and viscous liquid, the sizes of the droplets electrosprayed from the Taylor cone are found to be relatively insensitive to applied voltages and the electrosprays assisted by the corona discharge call produce monodisperse droplets as long as the corona intensity is not too high. Near the minimum flow rate where a liquid cone is stable, the spray tends to consist of a one -peak monodisperse distribution of drop lets. However, at high flow rates, the spray bifurcates into bimodal distributions, which are consistent with the result of the previous study for less viscous liquids than our liquids. For liquid flow rates (Q) below 1 nl/s, the measured droplet diameters by the aerosizer are in the range of 0.30 to 1.2 ${\mu}{\textrm}{m}$ for the glycerol solutions. The diameters of monodisperse droplets scale approximately with $r^*=Q_$\tau$(Q$\tau$){^1/3}$ where $r^*$ is a characteristic length and $\tau$is the electrical relaxation time of the fluid. However, when compared with several represe ntative scaling laws, the droplet diameters are two to six factors greater than those predicted by the scaling laws. This may be closely related to the combined effect of the much higher viscosity and the electrical charge on the jet breakup of glycerol so solution.

• 대한기계학회논문집B
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• 제21권4호
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• pp.473-485
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• 1997

Detailed experimental study has been made of air blast kerosene spray flames with and without swirl in combustion air flow. Phase-Doppler detect technique is used to measure Sauter mean diameter, axial component mean and rms velocity, size-velocity correlation, and number density. These measurements are obtained for both nonreacting and reacting cases under several stable flame conditions. The results show that the introduction of swirl to the combustion air modifies the spatial distribution of droplet size, velocity, and number density, and thus alters the flame structure. However, due to the weak swirl intensity, the overall structure of swirling flames are essentially same as that of nonswirling flames. Physical model of structure of air blast atomized spray flames is projected to show that spray flames are composed of three distinct regions: the two-phase mixture region, the main reaction and the intermittent combustion region. Near the atomizer, two phase mixture of droplet and air is formed in the core region. This dense spray region is characterized by high droplet number density and the strong convective effect. There follows the main combustion region where the main flame penetrates within the spray boundary. Main reaction region of these flames are governed by internal group combustion mode. Finally there exists the intermittent combustion region where local group burning or isolated droplet burning occurs.

• 한국재료학회지
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• 제21권12호
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• pp.690-696
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• 2011

In this study, nano-sized tin oxide powder with an average particle size of below 50 nm is prepared by the spray pyrolysis process. The influence of air pressure on the properties of the generated powder is examined. Along with the rise of air pressure from $0.1kg/cm^2$ to $3kg/cm^2$, the average size of the droplet-shaped particles decreases, while the particle size distribution becomes more regular. When the air pressure increases from $0.1kg/cm^2$ to $1kg/cm^2$, the average size of the dropletshaped particles, which is around 30-50 nm, shows hardly any change. When the air pressure increases up to $3kg/cm^2$, the average size of the droplet-shaped particles decreases to 30 nm. For the independent generated particles, when the air pressure is at $0.1kg/cm^2$, the average particle size is approximately 100 nm; when the air pressure increases up to $0.5kg/m^2$, the average particle size becomes more than 100 nm, and the surface structure becomes more compact; when the air pressure increases up to $1kg/cm^2$, the surface structure is almost the same as in the case of $0.5kg/cm^2$, and the average particle size is around 80- 100 nm; when the air pressure increases up to $3kg/cm^2$, the surface structure becomes incompact compared to the cases of other air pressures, and the average particle size is around 80-100 nm. Along with the rise of air pressure from $0.1kg/cm^2$ to $0.5kg/cm^2$, the XRD peak intensity slightly decreases, and the specific surface area increases. When the air pressure increases up to $1kg/cm^2$ and $3kg/cm^2$, the XRD peak intensity increases, while the specific surface area also increases.

• 한국추진공학회지
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• 제14권5호
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• pp.51-56
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• 2010

고속회전 시험장치를 이용하여 V 형태의 회전식 연료 노즐의 오리피스 직경에 따른 분사특성을 파악하기 위한 연구를 수행하였다. 시험장치는 고속 회전장치, 연료공급장치, 아크릴 케이스로 구성하였다. 분무 오리피스의 직경과 회전속도를 변화시켜가며 분무실험을 수행하였다. 분무입자의 크기 및 속도 측정은 PDPA(Phase Doppler Particle Analyzer) 시스템을 사용하였고, Nd-Yag Laser를 이용하여 분무특성을 가시화하였다. 실험결과, 분무오리피스의 직경이 커질수록 분무입자의 크기가 작아졌으며, 분무입자 크기가 가장 작은 값을 보이는 분무오리피스의 한계 직경이 존재하였다. 오리피스의 직경이 이 한계직경 보다 클 경우 분무입자의 크기는 더 이상 감소하지 않았다. 이것은 분무 오리피스의 직경이 한계직경보다 커질 경우 오리피스 내의 액막이 균일하게 분포하지 않기 때문으로 판단된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.79-84
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• 2001

The effect of spray characteristics on desulfurization yield was evaluated by performing experiments with pilot spray drying sorber (SDS). Among the variables of operating conditions, the slurry-spraying conditions were chosen as major parameters; Stoichiometric ratio and Sauter mean diameter of slurry droplet were varied for the different gas temperatures and $SO_{2}$ concentrations in the inlet gas flow. From the experimental results, we proposed semi-empirical models of desulfurization yield for both Stoichiometric ratio and Sauter mean diameter of droplets. The optimal condition of spray can be determined based on these results, which might be applied to the design or scale-up of SDS systems.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.97-104
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• 2007

The object of this work is to analyze the macroscopic spray performance and atomization characteristics between diesel and biodiesel fuels. In this study, the effects of mixture ratios of biodiesel fuel on the spray tip penetration, fuel injection rate, spray cone angle, and the atomization characteristics such as droplet size, droplets distribution, and spray arrival time according to the axial distance were investigated at various injection parameters. It is revealed that the injection rate is more affected by injection pressure than mixture ratio. And, the spray development process is closely matched between diesel and biodiesel fuels. However, the droplet atomization characteristics of biodiesel shows deteriorated results as the mixture ratio of biodiesel increased because of the high viscosity and density.