• Journal of Advanced Marine Engineering and Technology
• /
• 제24권5호
• /
• pp.25-32
• /
• 2000

In this paper, experiments investigating the high-temperature region heat transfer coefficients for the spray cooling of hot flat plates were performed by down spray water using flat spray nozzles. The heat transfer surface is made of copper and is 100mm in length and 40mm in width and 15mm in thickness. The experimental condition of spray are as follows: temperatures of the water droplets are T=20~$80^{\circ}C$ and droplets volume fluxes are D=0.001565~0.010438$m^3/m^2s$. Next, correlating equations for the heat transfer characteristics of spray cooling in the high temperature region are developed from the effects of droplets volume flux and the surface temperature of heat transfer plate.

• Journal of Advanced Marine Engineering and Technology
• /
• 제26권3호
• /
• pp.320-327
• /
• 2002

An experimental study of heat transfer from hot flat surface to water sprays was conducted in high temperature region. Heat transfer measurements for hot flat surface were made by 4 sheathed C-A thermocouples. Droplets volume flux were also measured-independently at a position in spray field. The test conditions included variations in droplets volume flux, subcooling of cooling water of $1.565\times10^{-3} to 14.089\times10^{-3}m^3/m^2s and 80 to $20^{\circ}C$ respectively. The effects of inclination angle on heat transfer were investigated and changes in inclination angle of hot flat surface affected heat transfer coefficients of high temperature region.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
• /
• pp.8-14
• /
• 2001

The purpose of this study is to elucidate heat characteristics according to inclination angle of the hot flat plate at the spray cooling. As results of this experiment, the heat flux, the heat transfer coefficient and the cooling speed are increased as the liquid volume flux and subcooled temperature go up. And as the inclination angle of the heat transfer surface is increased, the cooling speed on the inclined flat plate becomes faster. It means that the cooling ability is increased because droplets were excluded by gravity.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2009년도 춘계학술대회 논문집
• /
• pp.149-152
• /
• 2009

직접분사방식 추력기 노즐오리피스로부터 분사되는 분무입자의 발달특성을 연구하기 위해 분무의 다양한 위치에서 평균속도, 직경, 그리고 부피유속과 같은 분무특성인자들을 측정한다. 실험 결과로부터, 고속의 큰 직경을 갖는 분무 입자들이 주변 공기로의 운동량 손실로 인해 하류로 이동함에 따라 저속의 작은 입자로 분열한다. 또, 분무 확산 및 분산에 의해 높은 부피유속의 영역이 반경방향으로 넓게 확장된다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
• /
• pp.125-128
• /
• 2008

이중모드 위상도플러속도계(Dual-mode Phase Doppler Anemometry, DPDA)를 이용하여 소형 액체 로켓엔진 인젝터 분무의 미립화 특성을 고찰하였다. 분무액적의 반경방향 이동에 따른 속도, 크기, 수밀도, 부피플럭스 등을 다양한 분사압력에서 측정하여 인젝터 분무의 공간분포 특성을 규명한다. 분사 압력이 증가함에 따라 분무액적의 속도, 난류강도, 수밀도, 그리고 부피플럭스는 증가하지만, 산술평균 직경($D_{10}$)과 분무액적의 증발율에 대한 척도인 Sauter Mean Diameter($D_{32}$)로 표현되는 액적의 크기는 감소하였다. 또, 속도와 부피플럭스는 Sauter 평균직경(Sauter mean diameter, SMD)에 비례하는 것을 알 수 있었다.

• 한국추진공학회지
• /
• 제12권5호
• /
• pp.1-8
• /
• 2008

소형 액체로켓엔진 인젝터 분무의 공간분포 특성 규명을 위해 이중모드 위상도플러속도계(DPDA)를 이용한다. 분사압력 및 분무확산방향 이동거리를 변화시켜 분무액적의 크기, 속도 등을 측정하고, 산술평균직경(AMD), Sauter 평균직경(SMD), 수밀도, 스팬(span of drop size distribution), 그리고 체적 유속(volume flux) 등의 분무 매개변수를 도출하여 인젝터 분무의 분열특성을 고찰한다. 분사압력이 증가함에 따라 분무액적의 수밀도, 스팬, 그리고 체적 유속은 증가하지만, AMD는 감소하였다.

• 한국분무공학회지
• /
• 제22권2호
• /
• pp.80-86
• /
• 2017

The soot formation characteristics of various alkane-based single fuel droplets were studied in this work. Also, This study was performed to provide the database of the soot behavior and formation of alkane-based single fuel droplet. The experimental conditions were set to 1.0 atm of ambient pressure ($P_{amb}$), 21% of oxygen concentration ($O_2$) and 79% of nitrogen concentration ($N_2$). Combustion and soot formation of single fuel droplet was visualized by visualization system with high speed camera. At the same time, ambient pressure, oxygen concentration and nitrogen concentration were maintained by ambient condition control system. Soot formation characteristics was analyzed and compared on the basis of intensity ratio ($I/I_0$) of background image. The results of toluene fuel droplet showed the largest soot generation. Soot volume fraction ($f_v$) was almost the same under the identical fuel types regardless of various initial droplet diameter ($d_0$) since thermophoretic flux was not much changed under the same ambient conditions.

• 한국분무공학회지
• /
• 제5권4호
• /
• pp.40-46
• /
• 2000

To understand the basic the structure of the spray field and to obtain the initial conditions for computational models for shear coaxial twin-fluid injectors. the atomization characteristics under different flow and geometric conditions were examined. The spray characteristics such as SMD, mean axial and radial velocities, Dia. of droplets and volume flux with a P.D.P.A. Water and nitrogen gas under atmospheric conditions were used as a test fluids. The drops produced by shear coaxial injectors continue to disintegrate along the spray axis and decrease their sizes. SMD was the maximum at the spray center of spray and decreased with increasing radial distance. The results of this parametric study showed that SMD decreased with increasing gas injection velocity as well as with decreasing liquid injection mass flow rate, The relative velocity between gas and liquid flow played a significant role resulted in decreasing SMD and in spreading the spray. Recessing the liquid orifice resulted decreasing SMD and a spreading the spray. Recess of liquid orifice by 5.0mm showed best atomization characteristics in this experiment. Although drop diameter changes, shear coaxial injector sprays had constant velocity and exhibited a high degree of radial symmetry.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 1999년도 제13회 학술강연논문집
• /
• pp.27-27
• /
• 1999

To illustrate the global variation of the droplet mean diameters and the turbulent flow characteristics in counterflowing internal mixing pneumatic nozzle, the experimental measurements at five axial downstream locations(i.e., at Z=30, 50, 80, 120, and 170mm) were made using a PDPA(Phase Doppler Particle Analyzer) under the different air injection pressures ranging from 40 ㎪ to 120 ㎪. A nozzle with axi-symmetric tangential-drilled four holes at an angle of 15$^{\circ}$ has been designed and manufactured. The distributions of velocities, turbulence intensities, turbulence kinetic energy, turbulent correlation coefficients, spray angle, droplet mean diameters, volume flux, number density are quantitatively analyzed. It is possible to discern the effects of increasing air pressure. It indicates that the strong axial momentum in spite of more or less disparity between the velocity components means more reluctant to disperse radially, and that axial fluctuating velocities are substantially higher than those of radial and tangential ones, suggesting that the disintegration process is enhanced under higher air assist. The larger droplets are detected in the spray centerline at the near stations and smaller ones are generated due to further subsequent breakup at farther axial locations are attributed to the internal mixing type nozzle characteristics. Despite of the strong axial momentum, the poor atomization around the centre close to the nozzle exit is attributed to the lower rates of spherical particles which are not subject to instantaneous breakup. As it goes downstream, however, substantial increases in SMD(Sauter Mean Diameter) from the central part toward spray periphery are understandable because the droplet relative velocity is too low to bring about any subsequent disintegration.