• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.330-339
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• 2005

An experimental study on the behavior of droplets impinging on a solid flat surface was carried out in the present study. Breakup of a liquid droplet impinging on a solid surface has been investigated experimentally for various liquids with different properties. The liquid droplet temperature and incident angle were chosen as major parameters. Liquid droplet temperature and incident angle varied in the range from $-20{\circ}C\;to\;30{\circ}C\;and\;from\;30{\circ}\;to\;60{\circ},$ respectively. It was found that the variation of droplet temperature influences upon the mean diameter and uniformity of droplets which were bounced out from the solid surface. With increase of incident angle the dispersion mass fraction increases, causing the decrease of liquid film flow rate. As the liquid temperature increases, dispersion mass fraction increases since the surface tension decreases.

• Journal of ILASS-Korea
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• v.5 no.3
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• pp.27-36
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• 2000

In this study, spray characteristics of a dual airblast atomizer are addressed. Three dimensional characteristics of a dual airblast atomizer with air swirl are measured to provide the significant data. The liquid flow rate was fixed at 0.06 kg/min, and atomizing air was controlled at the liquid-air mass ratio of 4.0. The performance of the spray with co-swirl and counter-swirl flow was investigated at each point in the developed spray region using a three-component phase Doppler particle analyzer. This instrument was also used to evaluate the concentration profiles. The three dimensional mean velocity were investigated of present flow characteristics of the dual airblast atomizer. In addition, drop size distributions, mean droplet size profile, and droplet concentration were analyzed to understand atomization characteristics. This experimental results can be conveniently utilized for the preliminary design of gas turbine engines for aircraft.

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

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.47-53
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• 2006

The purpose of this study was to investigate the significant characteristics in spray of industrial etch-nozzle for the design of process. The experiment was carried out with different spray pressure and industrial nozzle in wet etch. The characteristics of liquid spray, such as axial velocity and sauter mean diameter measurements were obtained by PDA. And impact force was calculated from spray characteristics. It was found that the fluid with higher spray pressure resulted in the smaller SMD and the higher droplet velocity and impact force. The depth of etch was increased in case of high spray pressure. In the case of injection angle oscillated between $20^{\circ}$, the result indicated constant effect of etch. The correlation between the spray characteristics and etch ones were analyzed. The depth of etch had good positive correlation with axial velocity and impact force. The result clearly shows that the characteristics in wet etch are strongly related to the spray characteristics with process.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.986-998
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• 2002

Flow and spray characteristics are critical factors that affect the performance and exhaust emissions of a direct injection diesel engine. It is well known that the swirl control system is one of the useful ways to improve the fuel consumption and emission reduction rate in a diesel engine. However, until now there have only been a few studies on the effect of flow on spray. Because of this, the relationship between the flow pattern in the cylinder and its influence on the behavior of the spray is in need of investigation. First, in-cylinder flow distributions for 4-valve cylinder head of DI (Direct Injection) Diesel engine were investigated under steady-state conditions for different SCV (Swirl Control Valve) opening angles using a steady flow rig and 2-D LDV (Laser Doppler Velocimetry). It was found that swirl flow was more dominant than that of tumble in the experimented engine. In addition, the in-cylinder flow was quantified in terms of swirl/tumble ratio and mean flow coefficient. As the SCV opening angle was increased, high swirl ratios more than 3.0 were obtained in the case of SCV -70° and 90°. Second, spray characteristics of the intermittent injection were investigated by a PDA (Phase Doppler Anemometer) system. A Time Dividing Method (TDM) was used to analyze the microscopic spray characteristics. It was found that the atomization characteristics such as velocity and SMD (Sauter Mean Diameter) of the spray were affected by the in-cylinder swirl ratio. As a result, it was concluded that the swirl ratio improves atomization characteristics uniformly.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.4
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• pp.444-453
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• 2014

A throttleable rocket engine enables operational possibilities such as the docking of spacecraft, maneuvering in a certain orbit and landing on a planet's surface, altitude control, and entrance to atmosphere-less planets. Thus, throttling methods have long been researched. However, dual-manifold injectors, which represent one throttling method, have been investigated less than others. In this study, dual-manifold and single-manifold injectors were compared to determine the characteristics of dual-manifold injectors. Also, the effects of gas injection were investigated with various F/O ratios. To investigate the characteristics, mass flow rate, spray pattern, spray angle, and droplet size were measured. The spray angle and droplet size were captured by indirect photography. About 30 images were taken to assess the spray patterns and spray angle. Also, 700 images were analyzed to understand the droplet distribution and targeting area, moving to the right from the centerline with 1.11-cm intervals. The droplet size was obtained from an image processing procedure. From the results, the spray angle showed two transition regions, due to swirl momentum in the swirl chamber regardless of the F/O ratio. The droplet size showed similar trends in both dual-manifold and single-manifold injectors except in the low mass flow rate region. In the case of the dual- manifold injector, the spray cone was not fully developed in the low mass flow rate region due to low angular momentum in the swirl chamber.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.9
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• pp.569-576
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• 2016

The objective of this study was to investigate, using a numerical method, the fuel injection targeting for improving the combustion performance in a HSDI diesel engine. In this work, the ECFM-3Z model was applied as the combustion model, and the injection mass, inclined spray angle, and injection timing were varied for the study on the targeting of fuel spray. The results of this work were compared in terms of cylinder pressure, rate of heat release, and exhaust emissions characteristics. It was found that the cylinder pressure increased when the injection timing was advanced, and the rate of heat release increased when more fuel was injected into the piston bowl. In addition, $NO_x$ emission increased owing to the increase in the rate of heat release. On the other hand, CO and soot emissions decreased because of the improvement in combustion performance.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.159.1-159.1
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• 2011

Partial oxidation reformer was fabricated and operated using commercial transportation fuels. Fuel injector and heating coil were used for fuel atomization and startup, respectively. The reformer was designed to produce syngas for $150{\sim}200W_e$ class solid oxide fuel cell. The reformer was operated in the $O_2$/C range between 0.6 and 0.8 while the capacity was fixed at $150W_e$. The temperature range in catalyst bed was between $500^{\circ}C$ and $900^{\circ}C$. Only 83% fuel was converted to $H_2$, CO, $CO_2$ and $CH_4$ at the operating conditions. The lowest temperature increase to $700^{\circ}C$ when the reformer was operated at $200W_e$, Although the temperature profiles was improved, fuel conversion was 88%. On the other hand, fuel was completely converted when micro-reactor operated at the same condition. This difference maybe due to aromatic compounds formation at homogeneous region. In addition, a significant amount of coke deposition was observed at vent line. Homogeneous reaction depends on the degree of mixing. For this purpose, two fluid nozzle and Ultra sonic injector were compared to investigate the effect of atomization. Sauter mean diameter(SMD) of Ultra sonic injector was lower than two-fluid nozzle at test condition. However, conversion efficiency and fuel conversion were not improved by using two-fluid nozzle. these results imply that the temperature of homogeneous reaction region should be controlled to prevent coke formation.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.26-33
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• 2006

The use of high-density propellants can provide performance advantages in space launch vehicles by allowing an improved structural ratio due to smaller propellants tanks. The Jet A-1 fuel is currently used in Korean space launch vehicle development and it has lower density than other advanced hydrocarbon fuels such as RP-1 or RG-1. In this paper, the results of hydraulic and combustion tests conducted for the two newly developed densified hydrocarbon fuels are presented and they are compared with the results of Jet A-1. Conclusively, the two densified hydrocarbon fuels presented equivalent or even higher combustion performance compared to the Jet A-1 and the performance difference was found to be more obvious in the injector of external mixing.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.39-45
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• 2004

Experiments were performed in a two-phase swirling spray facility that has been described elsewhere. Measurements of spray transport and drop size distribution are analyzed over wide ranges of air to liquid mass flow ratios, utilizing four different internal mixing pneumatic nozzles. The spatial distributions of mean velocities. fluctuating velocities, and velocity-diameter correlation were quantitatively analyzed. Also, the exponential correlation curves were obtained with ALR along the spray centerline, which indicated an approximately identical formulation regardless of ALR. It indicated that the atomization characteristics were remarkably superior in the case of 30o of swirl angle with higher ALR. Among other things. nozzle configuration is one of the significant parameters affecting spray phenomena from an internal mixing nozzle. Turbulence intensities are increasingly degenerated with an increase of nozzle configuration, allowing a rapid increment of drop size distribution.