• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.4
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• pp.22-28
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• 2003

Predictions of the fuel spray dispersion and mixing processes are very important to improve the fuel consumption and exhaust emissions in GDI engines. Numerical and experimental analysis of the sprays with a swirl injector have been conducted. A numerical analysis is carried out using KIVA-II code with modified spray models. Experimental measurements are performed to show the global spray images and the local images near nozzle tip using laser sheet visualization technique. Computed and measured spray characteristics such as spray width, tip penetration are compared, and good agreements can be achieved. The spray head vortex is stronger as the injection pressure increases, but numerical calculations cannot show the head vortex properly.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.27-32
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• 2000

The main objective of this work is to investigate the effect of ambient conditions on the spray behavior and spray characteristics of high-pressure fuel injector. For this purpose, the effects of ambient pressure and temperature on the spray characteristics have been studied by applying the analysis of visualization system and phase Doppler particle analyzer. In this experiment, the visualization of spray behavior was performed under various ambient gas conditions and injection parameters such as gas temperature, ambient pressure, injection pressure of injector, and axial distance from the nozzle tip. Based on the investigation results, the spray tip penetration and spray width decrease with the increase of ambient gas pressure in the spray chamber. The effects of the spray parameters on the microscopic characteristics of gasoline spray were discussed.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.504-509
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• 2016

Defects in dissimilar metal welds are reported to be on the increase during the operating lifespan and aging of nuclear power plants. In Korea, reported cases of defects due to dissimilar metal welds include the drain nozzle of a steam generator and RCS hot tube sampling nozzles. Therefore, there is an urgent need to develop a reliable automated nondestructive inspection technique and a system for the inspection of dissimilar metal welds of small diameter nozzles in a high radiation area of a nuclear power plant. In this study, to ensure effective defect inspection of small diameter nozzles (RCS high-temperature tube sampling nozzle) of a nuclear power plant, three different methods were developed. These include: (1) optimum inspection probe design by beam simulation, (2) multi-directions UT optimum inspection technique for the inspection of small diameters of different welded parts, and (3) remote control automatic inspection system. The developed technique and systems have been verified to be suitable for use in the inspection of defects in smaller diameter nozzles in nuclear power plants.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.22-28
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• 2021

Combustion characteristics were examined experimentally for a swirl-stabilized double cone premixed burner nozzle used for industrial gas turbines for power generation. An original model and a variant with a different fuel injection pattern are tested to compare their combustion characteristics such as NOx, CO and stability in pressurized conditions with single burner-flame and in an ambient multi-flame conditions with multi-burners. Test results show that NOx emissions are smaller for the variant, whose number of fuel holes is reduced with the same total area of fuel holes, in ambient and pressurized single-flame conditions with single burner, which results from enhanced fuel/air mixing due to a higher penetration of fuel into the air stream. The multi-burnerflame test results show that NOx emissions are smaller for the variant due to reduced flame interactions, which, on the contrary, slightly reduces the stability margin. On-site test results fromin an actual power plants also show that NOx emissions are reduced for the variant, compared with the original one, which is in agreement with the lab test results stated above.

• Nuclear Engineering and Technology
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• v.49 no.7
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• pp.1547-1554
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• 2017

VESTA (Verification of Ex-vessel corium STAbilization) and VESTA-S (-small) test facilities were constructed at the Korea Atomic Energy Research Institute in 2010 to perform various corium melt experiments. Since then, several tests have been performed for the verification of an ex-vessel core catcher design for the EU-APR1400. Ablation tests of an impinging $ZrO_2$ melt jet on a sacrificial material were performed to investigate the ablation characteristics. $ZrO_2$ melt in an amount of 65-70 kg was discharged onto a sacrificial material through a well-designed nozzle, after which the ablation depths were measured. Interaction tests between the metallic melt and sacrificial material were performed to investigate the interaction kinetics of the sacrificial material. Two types of melt were used: one is a metallic corium melt with Fe 46%, U 31%, Zr 16%, and Cr 7% (maximum possible content of U and Zr for C-40), and the other is a stainless steel (SUS304) melt. Metallic melt in an amount of 1.5-2.0 kg was delivered onto the sacrificial material, and the ablation depths were measured. Penetration tube failure tests were performed for an APR1400 equipped with 61 in-core instrumentation penetration nozzles and extended tubes at the reactor lower vessel. $ZrO_2$ melt was generated in a melting crucible and delivered down into an interaction crucible where the test specimen is installed. To evaluate the tube ejection mechanism, temperature distributions of the reactor bottom head and in-core instrumentation penetration were measured by a series of thermocouples embedded along the specimen. In addition, lower vessel failure tests for the Fukushima Daiichi nuclear power plant are being performed. As a first step, the configuration of the molten core in the plant was investigated by a melting and solidification experiment. Approximately 5 kg of a mixture, whose composition in terms of weight is $UO_2$ 60%, Zr 10%, $ZrO_2$ 15%, SUS304 14%, and $B_4C$ 1%, was melted in a cold crucible using an induction heating technique.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.351-358
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• 2006

The capability of high pressure injection with small fuel quantify at all engine operating conditions is one of the main feature in common rail fuel injection system, which is used in small and light-duty Diesel engine. The key parameter for the better atomized fuel sprays and multiple injections of this common rail fuel injection control, that can be freely selected irrespective of the engine speed and load is the mechanism controlling the needle energizing and movement in high pressure Diesel injector. In the electro-hydraulic injector, the injection nozzle is being opened and closed by movement of the injector's needle which is balanced by pressure between the nozzle seat and the needle control chamber. This study describes the macroscopic spray structure characteristics of the common rail Diesel injectors with different electric driving method i.e. the solenoid-driven and piezo-driven type. The macroscopic spray characteristics such as spray tip speed. spray tip penetration and spray cone angle were investigated by the high speed spray, which is measured by the back diffusion light illumination method with optical system for the high speed temporal photography in a constant volume chamber pressurized by nitrogen gas. As the results, the prototype piezo-driven injector system was designed and fabricated for the first time in domestic case and the effect of injector's needle response driven by different drive type was compared between the solenoid and piezo-driven injector It was found therefore. that the piezo-driven injector showed faster needle response and had better needle control capability by altering the electric input value than the solenoid-driven injector.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1047-1052
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• 2012

Primary water stress corrosion cracking (PWSCC) instances have been reported in the Alloy 600 reactor pressure vessel head penetration nozzle and the Alloy 82/182 dissimilar metal butt weld nozzle in several PWRs. Therefore, in-service inspection programs have been adopted worldwide to prevent failure at the weld region. If a PWSCC is observed at the dissimilar metal weld region during inspection, its structural integrity should be evaluated; however, this requires considerable time and effort, and this might lead to a decrease in the plant utilization coefficient. To prevent this, KHNP-CRI have established integrity assessment criteria and developed a computer program for the fast evaluation and judgment of PWSCC. In this paper, the results and current status of the same are presented. Through this study, criteria for the structural integrity evaluation of PWSCC have been established, and a computer program has been developed to realize technical means for the evaluation of PWSCC structural integrity.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.165-172
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• 2018

As an approach for estimation of the droplet size in the molten salt-liquid metal extraction process, a droplet formation experiment at room temperature was conducted to evaluate the applicability of the Scheele-Meister model with water-mercury system as a surrogate that is similar to the molten salt-liquid metal system. In the experiment, droplets were formed through the nozzle and the droplet size was measured using a digital camera and image analysis software. As nozzles, commercially available needles with inner diameters (ID) of 0.018 cm and 0.025 cm and self-fabricated nozzles with 3-holes (ID: 0.0135 cm), 4-holes (ID: 0.0135 cm), and 2-holes (ID: 0.0148 cm) were used. The mercury penetration lengths in the nozzles were 1.3 cm for the needles and 0.5 cm for the self-fabricated nozzles. The droplets formed from each nozzle maintained stable spherical shape up to 20 cm below the nozzle. The droplet size measurements were within a 10% error range when compared to the Scheele-Meister model estimates. The experimental results show that the Scheele-Meister model for droplet size estimation can be applied to nozzles that stably form droplets in a water-mercury system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.534-540
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• 1988

A study on the mixing process of fuel with ambient gas is necessary to verify combustion process of a diesel engine, especially the mechanism of its ignition delay. In this study, a single shot of diesel spray was injected through either a constant pressure injection system and bypass type injection system. Measurements were made on the flow characteristics of ambient gas and its time history using a hot wire anemometer and a high speed camera. The gas flow direction was determined by a smoke tracer method. (1) The ambient gas of spray flows away at the stagnation part where static pressure value is positive and flows in at the penetration part of a negative value with the steady entrainment length of 0.7. (2) The steady entertainment velocity around the spray in creases from the nozzle tip to the downstream, has the maximum value at the mixing boundary part, and represents zero at the stagnation boundary part after which the stream flows reversely at the stagnation part.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.5
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• pp.467-472
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• 2007

In this study the penetration distance of liquid phase fuel(i.e. liquid phsae length) was investigated in evaporative field. An exciplex fluorescence method was applied to the evaporative fuel spray to measure and investigate both the liquid and the vapor phase of the injected spray. For accurate investigation, images of the liquid and vapor phase regions were recorded using a 35mm still camera and CCD camera, respectively. Liquid fuel was injected from a single-hole nozzle (l/d=1.0mm/0.2mm) into a constant-volume chamber under high pressure and temperature in order to visualize the spray phenomena. Experimental results indicate that the liquid phase length decreased down to a certain constant value in accordance with increase in the ambient gas density and temperature. The constant value, about 40mm in this study the, is reached when the ambient density and temperature of the used fuel exceed critical condition.