• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.1
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• pp.65-71
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• 2016

Injection rate, injection quantity and injection timing of fuel are controlled precisely by electric control in CRDI system. Particularly, injection rate being influenced with injection pressure affects to spray characteristics and fuel-air ratio, so it is a very important factor in diesel combustion. In this study, injection rates in accordance with injection pressure at a constant ambient pressure were measured with Zeuch's method. Under the same condition, non-evaporating spray images were taken with a high speed camera and analyzed carefully with Adobe Photoshop CS3. Macroscopic spray characteristics and breakup processes in the spray could be found from the examined and analyzed data. Injection start time and injection period were practically affected with injection pressure. Also, initial injection rate, spray penetration, spray angle and breakup of high density droplets region in the spray were affected with injection pressure. The results and techniques of spray visualization and injection rate measurement in this study would be practically effective to study a high pressure diesel spray for common rail direct injection system.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.4
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• pp.39-49
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• 1994

An experimental investigation was undertaken in a diesel spray to evaluate wall impingement behavior and droplet size distribution. Emphasis is placed on the possibility of the application for new combustion type which is based on OSKA-D type. Visualization were employed using optical scheme which was a spark shadowgraphy to observe the behavior of wall impingement caused by diesel spray vertically injected at the center of the combustion chamber. Droplet size measurements using Malvern system were made to quantify the visual observations with surface diameter of impingement. The effects of the surface dia. variation on the droplet size during injection with the wall impingement spray are discussed. It was found that for the wall impingement spray the droplet size becomes greatly small rather than the spray without the wall impingement and the droplet deposition rate of the injection fuel is decreased as the surface area of impingement becomes small.

• Journal of Sensor Science and Technology
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• v.26 no.5
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• pp.366-369
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• 2017

This work presents a detailed study of several parameters on the spray coating method for fabricating a flexible cantilever. Conventionally, spin coating method have been widely used in the microelectromechanical system (MEMS) fabrication process. However, the major drawback of this method is the difficulties in protecting various topography with photoresist film, particularly when the device is manufactured in high aspect ratio. It is also a challenging process to form a small pattern in the etched area. On the other hand, the commercial spray coating systems are not advantageous from an economic perspective and the technique is also providing less efficient. In order to solve these issues, we have developed a manual spray coating system which can be efficiently used by combining the accessories available in the laboratory. The developed spray coating system consists of a spin-coater, motorized stage, a spray gun with the capable of controlling centrifugal force, injection amount, injection angle, and spray range. The major advantage of the proposed spray coating system is its reasonable fabrication cost. Secondly, the system can be easily disassembled after finishing the coating experiment. Owing to the mentioned advantages, we sincerely believe that the proposed spray coating system can be effectively used in many related applications.

• Journal of ILASS-Korea
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• v.26 no.3
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• pp.111-119
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• 2021

Deteriorated agricultural diesel engines using mechanical fuel injection systems have low fuel injection pressures. And they are not equipped with an exhaust gas abatement device, so it produces a lot of exhaust gas. Remanufactured used injectors can reduce emissions because spray characteristics are improved. In addition, remanufacturing is environmentally friendly and economical compared to producing new parts. For efficient injector remanufacturing, it is necessary to conduct a comparison experiment on the spray characteristics of an used mechanical injector and a new injector of the same model. In this study, the spray characteristics of the two injectors were compared by performing an injection quantity measurement and a spray visualization experiment. As a result, the used injector had a larger injection quantity, a shorter spray tip penetration, a wider spray angle and a smaller spray area than the new injector.

• Journal of ILASS-Korea
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• v.16 no.4
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• pp.195-200
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• 2011

The pressure-swirl atomizer is widely used for the injectors in liquid rocket engines thanks to its high performance atomization and broad stability margin range. Spray mixed-interaction is an important area of study especially in cases where the propellant is mixed by spray interaction after an oxidant and a fuel are discharged separately. This interaction of sprays results in a significant modification of the spray characteristics such as the spatial evolution of the sprays. Experiments are conducted by a photographic technique to quantify the merged angle of the interaction regions of sprays from two pressure-swirl injectors. The experimental results show that the merged angle is mainly determined by the momentum flux ratios between two swirled sprays.

• Journal of Power System Engineering
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• v.12 no.5
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• pp.14-19
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• 2008

In order to meet stringent future emission regulations, especially to reduce Particulate Matter (PM) and NOX, stoichiometric diesel combustion technology with a piezo group-hole nozzle injector is being researched for reduction harmful emissions. A new nozzle layout, namely a group-hole nozzle, which has one group of small orifices with a wide spray included angle was investigated to improve the efficiency of stoichiometric diesel combustion. From this point of view, the group-hole nozzle suggested by Dense Co. is an attractive candidate method applicable to stoichiometric diesel combustion. The group-hole nozzle concept is to reduce the injector nozzle hole diameters without sacrificing spray penetration by closely locating two holes. Experimental studies have proven that the spray from group-hole nozzles have similar spray penetration to that of a single hole with equivalent overall nozzle hole area, but the spray drop sizes (SMD) are reduced, aiding vaporization and mixing.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.8
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• pp.1013-1020
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• 2001

This paper addresses to the area where the extended collision model is applied. In order to find the optimum shape of wall sprays, the extended model is applied to the nearest cells of just over the impaction wall, spray core or over all. The droplet distribution, wall spray radii, heights and gas flows are shown in all the cases. Those results show that the best spray shape represents in the case applying the extended model just on the impinging wall.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.179-184
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• 2007

The boiling heat transfer was experimentally investigated for the FC-77 sprays impacting a square heated test surface in a downward direction. Full cone spray nozzles were employed for the spray cooling experiment, and experiments were made under the test conditions of $Q=3.32{\times}10^{-6}{\sim}2.30{\times}10^{-5}\;m^3/s$, ${\Delta}T_{sub}=20{\sim}70^{\circ}C$. Also, heat transfer measurements were made using the copper block of $10{\times}10\;mm^2$ test area heated by nine cartridge heater. From the experimental results, correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30%$ error for FC-77.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.4
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• pp.475-482
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• 1998

In this paper, an experimental study was conducted to investigate the performance of the spherical ice particle production system which uses the technology of water spray in a vacuum chamber for increasing the heat transfer area. As a result, following conclusions were obtained. The diffusion-controlled evaporation model agreed relatively well with experiments. The spray flow rate influences the performance of the system rather than any other factors, for example, the spray nozzle position, the nozzle number. As the spray rate increases, the system efficiency increases. It is due to the entrainment of small droplets among the spray with the exhausted vapor. Thus the system should be designed and operated to prevent the entrainment. Assuming the compressor efficiency to be 70%, the COP of the system reaches highly up to 6 at a maximum spray rate. Under the conditions, however, the rigid ice layer is obtained because ice particles bond together with increase of the spray rate. Therefore, the spray rate should be controlled properly to make the spherical ice particles.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.58-64
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• 2003

Dimethyl Ether(DME) has been considered as one of the most attractive alternative fuels for compression ignition engine. Its main advantage in diesel engine application is high efficiency of diesel cycle with soot free combustion though conventional fuel injection system has to be modified due to the physical properties of DME. Experimental study of DME and conventional diesel spray employing a common-rail type fuel injection system with a 5-hole sac type injector was performed in a constant volume vessel pressurized by nitrogen gas. Spray cone angles and penetrations of the DME spray were characterized and compared with those of diesel. For evaluation of the evaporating characteristics of the DME, shadowgraphy technique employing an Ar-ion laser and an ICCD camera was adopted. Tip of the DME spray was formed in mushroom-like shape at atmospheric chamber pressure, which disappeared in higher chamber pressure. Spray tip penetration and spray cone angle of the DME became similar to those of diesel under 3MPa of chamber pressure. Higher injection pressure provided wider vapor phase area while it decreased with higher chamber pressure condition.