• Fire Science and Engineering
• /
• v.11 no.4
• /
• pp.15-23
• /
• 1997

A series of measurements and visualization to investigate the extingushiment of water sprays with pool fires is presented. Fire source is a small-scale pool burner with methanol, ethanol and gasoline. Measurements of temperature, O2, CO2, and CO concentrations along the plume centerline are carried out to observe pool structures without water sprays. Visualization by the Ar-ion laser sheet flow pattern of droplets of the sprays above the pool fires. It is observed than in the case of methanol and ethanol, water sprays continuously penetrate into the center of fuel surfaces. The gasoline pool fire allows intermittent penetration of water sprays because of pulsating characteristics of the gasoline flame. To evaluate the cooling effect of the fuel surface by the sprays, the temperature was measured at the fuel surface. As soon as the mists reach the fuel surface of methanol and ethanol, the temperatures of the fuel surface decrease rapidly below the boiling point, and then the fires are extinguished. Due to the application of mist upon the gasoline fire, though the fuel temperature decrease abruptly at the time of the injection, such a repid decrease do not continue till the extinction point.

• Journal of the Korean Society of Visualization
• /
• v.7 no.2
• /
• pp.42-46
• /
• 2010

In this paper we report the method of visualizing and measuring the fluid flow within a small droplet of millimeter size. We use a vertical laser sheet in visualization of the micrometer size and special attention is given to the arrangement of microscope to obtain clear images. Then we use a PIV technique to measure the velocity of the internal flow from the images taken. Since the droplet is of spherical shape, the images represent highly deteriorated picture of the real objects due to the refraction phenomenon. In order to compensate the refraction, we in this study developed two kinds of methods for the real velocity. In the first method, the refracted images are directly used to obtain the velocity in the image space, and then the velocity is transformed to the real space. In the second method the images are first transformed to the real-space objects, and then the PIV is used to measure the velocity field. We compared the two results to prove the usefulness of the compensation technique.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.1
• /
• pp.48-53
• /
• 2000

The effects of the internal flow in a diesel injection nozzle on the atomization of the spray has been investigated experimentally. Flow visualization was made using a transparent acrylic model nozzle. And also, measurement of the sac chamber pressure was made for clartfying the effect of pressure fluctuation in the sac chamber on the wpray behaviors. The geometry of the model nozzle was scaled up 10 times of the actual nozzle and the injection pressure for the model nozzle was adjusted so as to achieve a Reynolds number at the discharge hole which was the same as the actual nozzle. Polystyrene tracers, a laser sheet light and a still/high speed video camera were used to visualize the flow pattern in the sac chamber. When the needle lift was small, the high turbulence in the sac chamber generated by the high velocity seat flow made the spread angle of the spray large. Cavitation which arose in the sky chamber induced the pressure fluctuation and then affects the spread angle of the spray.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.11 no.2
• /
• pp.56-62
• /
• 2003

Spray characteristics of conventional diesel fuel and bio-diesel fuel(methyl-ester of soybean oil) were compared, in terms of spray tip penetration and spray angle, by using a commercial high pressure common rail injection system for light-duty DI Diesel engines. The experiments were carried out under the non-evaporating condition at ambient density(8.8, $15.6 kg/\textrm{m}^3$) and injection pressure(75, 135 MPa). The experimental method was based on a laser sheet scattering technique. Spray tip penetrations of bio-diesel fuel were longer, on the whole, than those of conventional diesel fuel, except for lower injection pressure(75 MPa) under lower ambient density$(8.8 kg/\textrm{m}^3)$. But spray near angle and spray far angle of bio-diesel fuel were smaller than those of conventional diesel fuel, implying spray angle is related to the growth rate of spray tip penetration. The experimental results of spray tip penetration agreed well with the calculated values by the Wakuri et al.'s correlation based on the momentum theory.

• Journal of ILASS-Korea
• /
• v.7 no.2
• /
• pp.7-15
• /
• 2002

A particle flow visualization, electrostatic charging measurement and separation of triboelectrically charged particles in the external electric field by a fluidized bed tribocharger are conducted for the removal of PVC particles from mixed waste plastics. The laboratory-scale triboelectrostatic separation system consists of the fluidized bed tribocharger, a separation chamber, a collection chamber and a controller. PVC and PET particles can be imparted negative and positive surface charges respectively due to the difference of triboelectric charging series between particles and particles in the fluidized bed tribocharger, and can be separated by passing them through an external electric field. To visualize these charged particles, He-Ne laser is used with cylindrical lenses to generate a sheet beam. In the charging measurement, the particle motion analysis system (PMAS), capable of determining particle velocity and diameter. is used to non-intrusively measure particle behavior in high strength electric field. The average charge-to-mass ratios of PVC and PET particles are $1.4\;and\;1.2{\mu}C/kg$, respectively. The highly concentrated PVC (91.9%) can be recovered with a yield of about 96.1% from the mixture of PVC and PET materials for a single-stage processing. The triboelectrostatic separation system using the fluidized tribocharger shows the potential to be an effective method for removing PVC from mixed plastics for waste plastic recycling.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.4
• /
• pp.462-472
• /
• 1999

De-NOx facility using Selective Catalytic Reduction method is the most widely applied one that removes NOx from flue gas emitted from combustion facility such as boiler for power generation engine incinerator etc. Reductant $NH_3\;or\;NH_4OH$ is sprayed into flue gas to convert NOx into $H_2O$ and $N_2.$ Good mixing between flue gas and $NH_3$ is the most important factor to increase reduction in catalytic layer and to reduce unreacted NH3 slip. Therefore the development of mixer device for mixing effect is one of the important part for SCR facility. Objectives of this study are to investigate the relation between flow and concentration field by observation at the wake of delta-wing type mixer. At the first stage qualitative measurement of flow field is conducted by flow visualization using laser light sheet in lab. scale wind tunnel. Also we have conducted the quantitative analysis by comparing flow field measurement using LDV with numerical simulation. On the basis of qualitative and quantitative analysis we investigate the dis-tribution of flow and concentration in flow model facility. The results of an experimental and compu-tational examination of the vortex structures shed from delta wing type vortex generator having $40^{\circ}$ angle of attack are presented, The effects of vortex structure on the gas mixing is discussed, too.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1661-1665
• /
• 2004

Hard disk drives (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. Laser sheet and digital camera was used for 2-dimensional visualization of the unsteady flow between co-rotating disks in air with a cylindrical enclosure (or shroud). Geometric parameters are gap height (H) between disks, and gap distance (G) between disk tip and shroud. The lobe-structured boundary between inner region and outer region was detected by inserted particles, and the number of dominant vortices was determined clearly It is found from flow visualization that the number of vortex cells can be correlated with Reynolds number based on H which is defined as $Re_H={\Omega}RH/v$ ranging from $7.96{\times}10^2$ to $1.43{\times}10^4$, and decreases as the disk speed increases. The lobe pattern by vortex cells is changed to a circular pattern for the wide gap than narrow one.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.12
• /
• pp.971-978
• /
• 2007

A spray-wall impingement process of a hollow-cone fuel spray from the high-pressure swirl injector in the Gasoline Direct Injection (GDI) engine were experimented and calculated at various wall geometries. The Linearized Instability Sheet Atomization (LISA) & the Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model and the Gosman model were applied to model the breakup and the wall impingement process of the hollow-cone fuel spray. The numerical modelings were implemented in the modified KIVA code. The calculation results of spray characteristics, such as a spray development process and a radial distance after wall impingement, compared with the experimental results by the Laser Induced Exciplex Fluorescence (LIEF) technique. The droplet size distribution and the ambient gas velocity field, which are generally difficult to obtain by the experimental methods, were also calculated and discussed. It was found that the radial distance after wall impingement and Sauter Mean Diameter (SMD) decreased with increasing a cavity angle.

• KSBB Journal
• /
• v.26 no.5
• /
• pp.422-426
• /
• 2011

Alginate bead has been supplemented with various polymers to control permeability and to enhance mechanical strength. In this report, fibroin-reinforced alginate hydrogel was prepared, in which spatial localization of fibroin molecules was investigated. Confocal laser scanning microscopy revealed that fibroin molecules formed a fibrous network in the alginate-fibroin beads, which was expected to enhance mechanical strength as same as in many composite materials. Uniaxial compression test showed that fibroin-reinforced alginate beads had increased mechanical strength only after methanol treatment that caused ${\beta}$-sheet formation among fibroin molecules. Simultaneous curing and dialysis of alginate beads were carried out to remove excesscalcium but to retain fibroin in the dialysis chamber, which fabricated beads without internal fibrous fluorescent stains. Fibroin molecules were only found beneath the surface of the beads. The fibroin-diffused shell was further processed to form a thick wall after drying or was mobilizedto the centre of the bead by methanol treatment. Accordingly, the structure analyses provide processing methods of fibroin to form a wall or center clumps, which could be applied to design controlled delivery device.

• Journal of the Korean Ceramic Society
• /
• v.52 no.5
• /
• pp.304-307
• /
• 2015

To reduce the lateral conduction loss of thin-film-processed cathodes, the microstructure of the thin-film cathode is engineered to contain a denser bridging layer in the middle. By doing so, the characteristic crack-like pores that separate the cathode domains in thin-film-processed cathodes and hamper lateral conduction are better connected and, as a result, the sheet resistance of the cathode is effectively reduced by a factor of 5. This induces suppression of the lateral conduction loss and expansion of the effective current collecting area; the cell performance is improved by more than 30%.