• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2562-2567
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• 2008

Jet impingement on a moving plate, which is applicable to cooling of hot metals in a steel-making process, is investigated numerically by solving the Navier-Stokes equations in the liquid and gas phases. The liquid-gas interface or free surface is tracked by a level-set method which is improved by incorporating the ghost fluid approach based on a sharp-interface representation. The computations are made for multiple jets as well as a single jet to compare their flow characteristics. Also, the effects of the nozzle pitch, moving velocity of plate and jet velocity on the interfacial motion and the associated flow and temperature fields.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.730-733
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• 2017

An ignitor for the initiation of burning propellants becomes one of the most critical components for the operation of liquid rocket engines. The important phenomenon of the igniter is thermoacoustic resonance. This paper mainly includes experimental results on thermoacoustic resonance phenomenon from distance between nozzle and resonance tube. The ultimate goal is to develop an ignitor capable of multiple ignitions based on research results about the usage of the thermoacoustic resonance phenomenon.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.21-24
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• 2006

Transient and asymmetric density distributions have been investigated by a digital speckle tomography with a novel integration method. Multiple CCD images captured movements of speckles in three angles of view simultaneously because the flows were asymmetric and unsteady. The speckle movements which have been formed by a ground glass between no flow and downward butane flow from an elliptical nozzle have been calculated by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. A novel integration method has been developed to obtain projection data from the deflection angles for the speckle tomography. The unsteady density fields have been reconstructed from the accurate projection values by the digital speckle tomography method using the developed integration method.

• 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.

• Journal of ILASS-Korea
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• v.5 no.1
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• pp.5-12
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• 2000

The beneficial aspects of applying emulsion fuels to combustion systems may be due to the changes of fuel properties which lead to the enhanced atomization characteristics. The spray characteristics of water/oil emulsified fuel injected from the pressure-swirl(simplex) atomizer using for oil burner were investigated. Four different water contents from 10 to 40 % by volume at 10% increment were prepared by mixing with the different contents of surfactants. Total amount of surfactant used was varied from 1 to 3 % by volume. This study demonstrates the influence of water and surfactant contents of emulsified fuel, injection pressure on the spray characteristics, i.e. Sauter mean diameter(SMD) and spray angle. The drop size distribution of the emulsified fuel spray was measured with a Malvem particle sizer. In order to measure the spray angle, the digital image processing was employed by capturing multiple images of the spray with 3-CCD digital video camera. It was evident that the addition of water and surfactant changes fuel properties which are the key parameters influencing the atomization of the spray. The increase in surfactant content results in the decrease of SMD and the increase in spray angle. The droplets decease with increase in injection pressure, but the influence of injection pressure in this experimental condition was less important than expected. The more viscous fuel with the increase of water content exhibits the larger droplets in the centerline of the spray, and the less viscous fuel in the outer edges of the spray. The increase in axial position from the nozzle causes the spray angle to decrease. The spray angle decreases with increase in water content. This is due to increase in viscosity with increase in water content.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.177-180
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• 2010

Two-stage light gas gun, sorted with Ballistic Range System, is used to research spray characteristics of supersonic liquid jets. When high pressure tube was pressurized to the 135 bar, diaphragm films which composed with OHP film are ruptured. Expansion gases accelerate a projectile approximately 250 m/s at the exit of pump tube. And accelerated projectile collides with liquid storage part and liquid jets were injected into supersonic conditions. Supersonic liquid jets show the multiple jets and generate shockwave at the forward region of jets. Supersonic liquid jets of speed and shockwave angle have different value at each case. Supersonic liquid jets with minimum velocities are injected with M=1.53 at the geometry condition of L/d=23.8.

• Journal of the Korean Society of Combustion
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• v.17 no.4
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• pp.11-20
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• 2012

The Blow-off characteristics of LPG/air lean pre-mixed flames were experimentally investigated using a double and a multiple concentric coflow burners. Experiments were conducted to understand the effects of recirculation motion, thermal interaction between flames, and stratified flame configuration. Here, the stratified premixed flame is a "new concept" of a flame that sequentially contains fuel rich, stoichiometric, and fuel lean reaction zones in a flame. The blow-off from a lean premixed flame was significantly suppressed with recirculation motion. The recirculation motion by itself, however, was not sufficient to prevent the blow-off when the equivalence ratio became low. The existence of a inner premixed flame could also help to prevent the blow-off of lean premixed flame; however, the blow-off suppression effect was rather diminished by weakened recirculation motion with the presence of inner flame. The inner flame could be separated from an outer flame on a multiple concentric coflow burner, causing recirculation motion as well as thermal interaction between flames to become effective; therefore, the blow-off was further suppressed. The lean premixed flame could be stabilized with a fuel rich premixed flames that was produced with the supply of fuel through an inner nozzle. The penetration of lean premixed gas from outside into the fuel stream produced a lifted rich premixed flame. Chemiluminescence images of OH, CH, and $C_2$ radicals confirmed the structure of a stratified premixed flame. The stable premixed flames could be obtained at the very fuel lean condition by applying the stratified premixed flame concept.

• Journal of the Korean Society of Safety
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• v.37 no.5
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• pp.80-88
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• 2022

The Korean nuclear industry had developed the SPACE (Safety and Performance Analysis Code for nuclear power plants) code, which adopts a two-fluid, three-field model that is comprised of gas, continuous liquid and droplet fields and has the capability to simulate three-dimensional models. According to the revised law by the Nuclear Safety and Security Commission (NSSC) in Korea, the multiple failure accidents that must be considered for the accident management plan of a nuclear power plant was determined based on the lessons learned from the Fukushima accident. Generally, to improve the reliability of the calculation results of a safety analysis code, verification is required for the separate and integral effect experiments. Therefore, the goal of this work is to verify the calculation capability of the SPACE code for multiple failure accidents. For this purpose, an experiment was conducted to simulate a Control Element Drive Mechanism (CEDM) break with a safety injection failure using the ATLAS test facility, which is operated by Korea Atomic Energy Research Institute (KAERI). This experiment focused on the comparison between the experiment results and code calculation results to verify the performance of the SPACE code. The results of the overall system transient response using the SPACE code showed similar trends with the experimental results for parameters such as the system pressure, mass flow rate, and collapsed water level in component. In conclusion, it can be concluded that the SPACE code has sufficient capability to simulate a CEDM break with a safety injection failure accident.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.1031-1038
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• 2002

The effects of casing shape on the performance and interaction between the impeller and casing in a small-size turbo-compressor are investigated. Numerical analysis is conducted for the compressor with circular and single volute casings from inlet to discharge nozzle. In order to predict the flow pattern inside the entire impeller, vaneless diffuer and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For compressible turbulent flow fields, the continuity and three-dimensional time-averaged Wavier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure and loss coefficients are obtained with various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. To prove the accuracy of numerical results, measurements of static pressure around casing and pressure difference between the inlet and outlet of the compressor are peformed for the circular casing. Comparisons of these results between the experimental and numerical analyses are conducted, and reasonable agreement is obtained.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1115-1122
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• 2002

The present experiment investigates the effects of pore density f of aluminum foam heat sinks, the jet-to-jet spacing X and the nozzle plate-to-target surface spacing H of 3$\times$3 square impinging arrays on the averaged Nusselt number. The performance of the aluminum foam heat sinks and the rectangular plate heat sink is evaluated in terms of the enhancement factor. /equation omitted/. The multiple impinging jet with X/d=4.0 displays higher Nusselt numbers than single impinging jet for 12.0$\leq$H/d$\leq$20.0. With the variation of the jet-to-jet spacing, the aluminum foam heat sink of 10 PPI show higher Nusselt numbers than the 20 and 40 PPI aluminum foam heat sinks. Further, the 10 PPI aluminum foam heat sink demonstrates 26% higher enhancement factor than the rectangular plate heat sink in the range of 7000$\leq$Re$\leq$11000.