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Kang-neung, South Korea

Flame transfer function measurements were performed in a turbulent premixed lean combustor with various blends of hydrogen and natural gas. The fuel mixture was completely premixed with air upstream of a choked inlet to the combustor to avoid equivalence ratio fluctuations. A variable speed siren was used to modulate fluctuations in the inlet velocity, which was measured using a hot wire anemometer as an input parameter of the flame transfer function. Heat release oscillations as an output function were determined using chemiluminescence measurements from whole flames. Stable flame images were captured to understand general flame behavior over a range of operating conditions and fuel blends. Experimental results showed that the stable flames' COMs (centers of mass) laid along a common path in a 2-D plane for all of the operating conditions and tested fuel compositions at a given injector geometry, and that variations in the stable flame shape could be characterized by the location of the common path of the flame's COM. It was also shown that changes in the fuels significantly affected the flame shape; as a result, flame dynamics varied with changes in flame geometry. Accordingly, flames that were close together on the characteristic flame COM curve were shown to have similar forced flame responses. © 2010 Elsevier Ltd. All rights reserved. Source

Kim D.,Gangwon Provincial College | Park S.W.,Hanyang University
Fuel Processing Technology | Year: 2010

An experimental study of the flame response in a premixed gas turbine combustor has been conducted at room temperature and under atmospheric pressure inlet conditions using natural gas. The fuel is premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. Therefore the observed flame response is only the result of the imposed velocity fluctuations, which are produced using a variable-speed siren. Also, a variable length combustor is designed for investigating characteristics of self-excited instabilities. Measurements are made of the velocity fluctuation in the mixing section using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function. The results show that the gain of flame transfer function is closely associated both with inlet flow forcing conditions such as frequency and amplitude of modulation as well as the operating conditions such as equivalence ratio. In order to predict the operating conditions where the combustor goes stable or unstable at given combustor and nozzle designs, time-lag analysis was tried using convection time delay measured from the phase information of the transfer function. The model prediction was in very good agreement with the self-excited instability measurement. However, spatial heat release distribution became more significant in long flames than in short flames and also had an important influence on the system damping procedure. © 2010 Elsevier B.V. All rights reserved. Source

Kim J.,University of Wisconsin - Madison | Reitz R.D.,University of Wisconsin - Madison | Park S.W.,Hanyang University | Sung K.,Gangwon Provincial College
Journal of Engineering for Gas Turbines and Power | Year: 2010

Experimental and numerical studies were performed to investigate the simultaneous reduction in NOx and CO for stoichiometric diesel combustion with a three-way catalyst. A single-cylinder engine was used for the experiments and KIVA simulations were used in order to characterize the combustion efficiency and emissions of throttled stoichiometric diesel combustion at 0.7 bar boost pressure and 90 MPa injection pressure. In addition, the efficiency of emission conversion with three-way catalysts in stoichiometric diesel combustion was investigated experimentally. The results showed CO and NOx emissions can be controlled with the three-way catalyst in spite of the fact that CO increases more at high equivalence ratios compared with conventional diesel combustion (i.e., lean combustion). At a stoichiometric operation, the three-way catalyst reduced CO and NOx emissions by up to 95%, which achieves lower emissions compared with conventional diesel combustion or low temperature diesel combustion, while keeping better fuel consumption than a comparable gasoline engine. Copyright © 2010 by ASME. Source

Jeong H.,Korea Institute of Energy Research | Jeong H.,Seoul National University | Yoo S.,Korea Institute of Energy Research | Lee J.,Seoul National University | An Y.-I.,Gangwon Provincial College
Renewable Energy | Year: 2013

Blue light has outstanding transmission characteristics in the sea, and is known to cause the most sensitive visual response in common squid Todarodes pacificus. Application of a light emitting diode (LED) that can efficiently emit monochromatic light is expected to bring enormous energy savings. LED can produce cost-effective low-wattage irradiance at the specific wavelength. This study investigated the retinular responses of common squid T. pacificus to colored LED lights and light adaptation conditions based on the Perkinje effect, which is the tendency for the luminance sensitivity of the human eye to shift depending on the bright and dark adaptation states. The changes of the retinular response to blue, red and white LED were investigated in the bright and dark adaptation conditions in the water tank experiment. The degree of light adaptation was similar between the bright adaptation state and dark adaptation state to blue light, which suggests that squid retina is highly sensitive to blue light as it has been reported to date. On the other hand, the degree of light adaptation to red LED light showed a tendency to increase, albeit slightly, over time. However, the degree of light adaptation to white light with wide wavelength band showed similar tendencies as to the case of red light in the dark adaptation condition, and was actually superior to the case of blue light in the bright adaptation condition. Also, the degree of light adaptation of the retina cells collected from the sea experiment was found to be between the range of 20 and 40%. From these results, blue light may be regarded as an excellent luring source as the retina of squid is highly sensitive to it, but it cannot be determined as the most ideal LED color for the purpose of catching fish. © 2012 Elsevier Ltd. Source

Lee J.-W.,University of California at Davis | Kim J.-W.,Gangwon Provincial College | De Riu N.,University of Sassari | Moniello G.,University of Sassari | Hung S.S.O.,University of California at Davis
Aquatic Toxicology | Year: 2012

Triplicate groups of juvenile green and white sturgeon (average weight of 30 ± 2. g) were exposed to one of four concentrations of dietary methylmercury (MeHg; 0, 25, 50, and 100. mg MeHg/kg diet) for 8 weeks to determine and compare the sensitivity of the two sturgeon species from a histopathological perspective. After 4- and 8-week exposure, histological changes were examined in the kidney, liver, gill, skeletal muscle, and heart muscle of both species using light microscopy. Marked abnormalities were observed in the kidney and liver of both sturgeon species after each exposure period; the abnormalities showed progressive histological alterations in severity with increasing doses and duration of exposure. Renal lesions included tubular epithelium degeneration and necrosis, renal corpuscular disintegration, and interstitial tissue degeneration. The changes observed in the livers of both sturgeon species were glycogen depletion and vacuolar degeneration. In the gill and skeletal and heart muscle of green and white sturgeon fed MeHg-added diets, mild histological changes were observed but did not show pronounced difference between the two species. Although the lowest observed effect concentration in both species was the 25. mg MeHg/kg diet, the histological changes in the kidney and liver were more pronounced at all treatments groups of green sturgeon than those of white sturgeon. The current results on structural changes of kidney and liver (i.e., more severe glycogen depletion and tubular epithelium degeneration in green sturgeon) confirmed our previous results, in that green sturgeon exhibited a higher mortality, lower growth rate, and lower protein, lipid, and energy contents in their whole body than white sturgeon under the same MeHg exposures. © 2011 Elsevier B.V.. Source

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