• Journal of ILASS-Korea
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• v.16 no.1
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• pp.27-36
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• 2011

The impact force on the single and overlap region of twin spray was experimentally evaluated using visualization method in full cone type swirl nozzle spray. Visualization of spray was conducted to obtain the spray angle and breakup process. The photography/imaging technique, based on Particle Image Velocimetry (PIV) using high-speed camera, was adopted for the direct observation of droplet motion and axial velocity measurement, respectively. Droplet size was measured by Particle Motion Analyze System (PMAS). The purpose of this study is to provide fundamental information of spray characteristics, such as impact force, for higher etching factor in the practical wet etching system. It was found that the spray angle, axial velocity and impact force were increased with increasing the nozzle pressure while droplet size decreased with increasing the nozzle pressure. Droplet size increased as the distance from nozzle tip was decreased. The impact force of twin spray in the overlap region was about 63.29, 67.02, 52.41% higher than that of single spray at 40, 50 and 60 mm of nozzle pitch, respectively. Also, the nozzle pitch was one of the important factors in the twin spray characteristics.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.354-358
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• 2007

An experimental study was performed to understand spray characteristics of the slinger injector. system for the micro turbojet engine. In this fuel injection system, fuel is sprayed and atomized in the combustor by centrifugal forces of engine shaft. This experimental apparatus consist of a high speed rotating Spindle, slinger injector, pressure tank and acrylic case. The droplet size and velocity were measured by PDPA(Phase Doppler Particle Analyzer) and spray was visualized by using Nd-Yag laser-based flash photography. From the test results, the droplet size(SMD) is largely affected to rotational speed, mass flow rate and the number of injection orifice. From the this experimental study, we could understand the spray characteristics of the slinger injection system and obtain the optimum shape of the slinger injector nozzle which is suitable for the micro turbojet engine.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.553-559
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• 2006

Most diesel injector, which is currently used in high-pressure common rail fuel injection system of diesel engine, is driven by the solenoid coil energy for its needle movement. The main disadvantage of this solenoid-driven injector is a high power consumption, high power loss through solenoid coil and relatively fixed needle response's problem. In this study, a prototype piezo-driven injector, as a new injector mechanism driven by piezoelectric energy based on the concept of inverse piezo-electric effect, has been designed and fabricated to know the effect of piezo-driven injection processes on the diesel spray structure and internal nozzle flow. Firstly we investigated the spray characteristics in a constant volume chamber pressurized by nitrogen gas using the back diffusion light illumination method for high-speed temporal photography and also analyzed the inside nozzle flow by a fully transient simulation with cavitation model using VOF(volume of fraction) method. The numerical calculation has been performed to simulate the cavitating flow of 3-dimensional real size single hole nozzle along the injection duration. Results were compared between a conventional solenoid-driven injector and piezo-driven injector, both equipped with the same micro-sac multi-hole injection nozzle. The experimental results show that the piezo-driven injector has short injection delay and a faster spray development and produces higher injection velocity than the solenoid-driven injector. And the predicted simulation results with the degree of cavitation's generation inside nozzle for faster needle response In a piezo-driven injector were reflected to spray development in agreement with the experimental spray images.

• Explosives and Blasting
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• v.37 no.4
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• pp.1-9
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• 2019

In this study the applicability of a Digital Image Correlation (DIC) method was investigated by measuring the displacement and vibration of rock pillar due to underground mining blasting. When combined with a high speed photography technology, the DIC method provides an excellent photographic image processing ability that can be used to convert the evolving full-field surface properties of structures to 2D or 3D set of coordinate values. The measured coordinate sets are then used to calculate the displacement, strain, and velocity of the target structure. This technique is widely used in science and engineering, and continuously finds its new application areas. In this study, the DIC system and the conventional seismograph were compared for their ability to measure the displacement and vibration produced by blasting. In the field test both methods showed similar results. Thus, it is concluded that the DIC method is feasible to measure the ground displacements and vibrations from blasting.

• Journal of Bio-Environment Control
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• v.26 no.3
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• pp.215-220
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• 2017

This study was conducted to improve the insufficiency of fruit vegetable grafting system developed by National Institute of Agricultural Sciences, Rural Development Administration. When the rotary blade cut the stem of scions and rootstocks, the grafting failure at curved cutting surfaces happened. The cutting depth of a tomato seedling by a rotated cutter was calculated 0.11 mm even when the cutting arm length and the maximum stem diameter were 50 mm and 5 mm, respectively. Mathematical analysis and high-speed photography showed that there was no problem by cutting in straight the stem of scions and rootstocks. The compression test of seedling stems to design the optimal shape of gripper showed that stems were not completely restored when they were compressed above 0.8 mm and 0.6 mm in case of rootstocks and scion, respectively. This study found that the bending angle of stem of tomato seedlings at the grafting period was 10 degree on average. The optimal gripper finger was the edge finger type which could be precisely set center point by adjusting the distance between fingers. In addition, it was found that most of seedling could be grasped without damage when the finger-to-finger distances is set to 2.5 mm for scion and 3.0 mm for rootstocks and finger are coated by 1 mm-thick flexible material.