• The KSFM Journal of Fluid Machinery
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• v.3 no.1 s.6
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• pp.43-50
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• 2000

Upgrade development of a high pressure ratio centrifugal compressor in marine engine turbochargers is presented. A new matched operating point at increased speed of rotation was determined through system cycle analysis using the exisitng test data of turbine performance. Under some severe restrictions for geometric parameters, the state-of-the-art methods of both aerodynamic design and CFD analysis were applied, in which only an impeller, a vaned diffusor and some part of casing wall were modified. Prototype hardware was fabricated and assembled for system performance tests. Excellent performance in pressure ratio and efficiency was obtained over whole speed region. Reduced surge and choke margin was, however, observed at design speed of rotation.

• Journal of Energy Engineering
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• v.10 no.4
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• pp.318-326
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• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1 MW organic Rankine cycle system was designed and developed. The exhaust gases of 175$^{\circ}C$ at two 100 MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1 MW as designed but only 670 kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• Journal of Energy Engineering
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• v.13 no.2
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• pp.118-127
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• 2004

The purpose of this study is experimentally to analyze that intake port swirl, injection system and turbocharger have an effect on the engine performance and the emission characteristics in a V8 type turbocharged intercooler D.I. diesel engine of the displacement 16.7ι, and to suggest the improvement of engine performance. Generally to enhance engine power, TCI diesel engine is put to practically use turbo-charged intercoler in order to increase boost efficiency which is cooled boost air. As results of considering the factors of the intake port of swirl ratio 2.25, compression ratio 17.5, re-entrant 8.5$^{\circ}$ combustion bowl, nozzle hole diameter ${\Phi}$0.33*3+${\Phi}$0.35*2, nozzle protrusion 3.18mm, injection timing BTDC 12$^{\circ}$CA and turbo charger (compressor 0.6A/R+46Trim, turbine 1.0A/R+57Trim) is the best in the full range of operating in the engine performance and the exhaust characteristics of NO$\_$x/ concentration. Therefore their factors are appropriated as intake system, injection and turbocharger system.

• Journal of Biosystems Engineering
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• v.26 no.3
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• pp.263-270
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• 2001

This study was conducted in order to develop wind-water heating system where frictional heat is creased between the rotor and working fluid when they are rotating in the cylindrical heat generator. The wind-water heating system is composed of rotor, stator, working fluid, motor, inverter and heat generation tank. Instead of wind turbine, we have used an electrical motor of 30㎾ to rotate the rotor in this system. Two working fluids and six levels of rotor rpm were tested to quantify heat amounts generated by the system. Generally, as motor rpm goes up heat amount increases that we have expected. At the same rpm, viscous fluid showed up better performance than the water, generating more heat by 10$\^{C}$ difference. The greatest heat amount of 31,500kJ/h was obtained when the system constantly drained out the hot water of at the flow rate of 500ℓ/h. Power consumption rate of the motor was measured by thee phase electric power meter where the largest power consumption rate was 14㎾ when motor rpm was 600 and gained heat was 31,500kJ/h, that indicated total thermal efficiency of the wind power water heating system was 62%.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.631-638
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• 2016

Offshore wind power can be an alternative for onshore wind power which suffers from not only civil complaints regarding to landscape damage and noise but also wind power siting due to lack of onshore site candidates. Compared to onshore wind power, offshore wind power is free from these problems considering that generally the sites are far enough from the coast. And more electricity is generated in offshore wind turbines due to abundant offshore wind resources. However high installation costs of offshore turbines could deteriorate the economical efficiency. The main cause of the high installation costs comes from a long-term lease of the heavy marine equipment and the consequential high rental cost. In this paper, the conceptual design of the support structure for offshore wind turbines will be suggested for the installation of them with less heavy marine equipment.

• Journal of Power System Engineering
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• v.16 no.1
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• pp.58-64
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• 2012

Power plant boiler is one of the most important utilities providing steam to turbine in thermal power plant. It is composed of thousands of boiler tubes for high efficient heat transfer. Boiler tube material is used in such high temperature and pressure as $540^{\circ}C$, $170kg/mm^2$. The boiler tube material is needed to resist corrosion damage, creep damage and fatigue damage. 2.25%Cr-1Mo steel is used for conventional boiler tubes. In these days steam temperature and pressure of the power plant became higher for high plant efficiency. So, the material property of boiler tube must be upgraded to meet the plant property. Several boiler tube material was developed to meet such condition. X20CrMoV12.1 steel is also developed in early 1980's and used for superheater and reheater tubes in supercritical boilers. The material has martensitic structure, which is difficult to evaluate the material degradation. Boiler tube material at severe condition was tested to evaluate long term and short term degradation and creep. Through long term and high temperature degradation test, lath structure was decreased and recrystallization has been proceeded by sub-crystal. And in this research the effect of temperature and stress on boiler tube characteristic,for example, deformation by creep was changed rapidly at relatively high temperature and stress because creep was affected easily by temperature and stress.

• Tribology and Lubricants
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• v.34 no.4
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• pp.138-145
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• 2018

Elliptical bearings are widely used for large steam turbines owing to their excellent load carrying capacity and good dynamic stability. Power loss in bearings is an extremely important parameter, especially for high turbine capacities. Optimization of operation conditions and design variables such as bearing clearance and bearing length can reduce the power loss in elliptical bearings. Although changes in the oil supply method have served to increase the efficiency of the tilting pad journal bearing, it has not explicitly improved elliptical bearings. In this study, we verify the static characteristics of an elliptical bearing by changing the direction of oil supply. We evaluate the bearing power loss and bearing metal temperature, and compare the bearing performance and reliability in different test cases. The direction of oil supply is $90^{\circ}$ (9 o'clock) and $270^{\circ}$ (3 o'clock) when the rotor rotates in a counterclockwise direction. We use an elliptical bearing with an inner diameter and active length of 220.30 and 110.00 mm, respectively. Bearing power loss and bearing metal temperatures are measured and evaluated by rotor rotational speed, oil flow rate, and bearing load. The results reveal a 20 reduction in the power loss when the direction of oil supply is 90. Furthermore, the oil film on the upper part of the bearing has a high temperature when the direction of oil supply is $90^{\circ}$. In contrast, when the direction of oil supply is $270^{\circ}$, the oil film on the upper part of the bearing is relatively cold.

• Journal of Powder Materials
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• v.19 no.6
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• pp.429-434
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• 2012

With increase in operating temperature of gas turbine for higher efficiency, it is necessary to find new materials of TBC for replacement of YSZ. Among candidate materials for future TBCs, zirconate-based oxides with pyrochlore and fluorite are prevailing ones. In this study, phase structure and thermal conductivities of $(La_{1-x}Gd_x)_2Zr_2O_7$ oxide system are investigated. $(La_{1-x}Gd_x)_2Zr_2O_7$ system are comprised by selecting $La^{3+}/Gd^{3+}$ as A-site ions and $Zr^{4+}$ as B-site ion in $A_2B_2O_7$ pyrochlore structures. With powder mixture from each oxide, $(La_{1-x}Gd_x)_2Zr_2O_7$ oxides are fabricated via solid-state reaction at $1600^{\circ}C$. Either pyrochlore or fluorite or mixture of both appears after heat treatment. For the developed phases along $(La_{1-x}Gd_x)_2Zr_2O_7$ compositions, thermal conductivities are examined, with which the potential of $(La_{1-x}Gd_x)_2Zr_2O_7$ compositions for TBC application is also discussed.

• Environmental and Resource Economics Review
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• v.23 no.4
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• pp.617-641
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• 2014

Korean electricity market is a Cost-Based Pool (CBP) designed to minimize electricity production cost through cost by providing cost reduction incentives to generators. Generation companies have shown diverse efforts to reduce costs in CBP market such as procuring low-price fuels, installing high efficiency gas turbine and constructing power plants near the heavy-load site. Recently, as a way to improve CBP market, a proposal to exclude no-load cost from System Marginal Price (SMP) and to compensate generators ex post was suggested to Korea Power Exchange. This study analyzes the impact of excluding no-load cost from SMP on the cost reduction incentive of generators. We found that excluding no-load cost from SMP enhances the likelihood of decreasing the cost reduction incentives of LNG combined-cycle generators lying on the price-setting range.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.10-17
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• 2004

The results of the combustion performance tests of gas generator which supplies hot gas into the turbine of turbo-pump for liquid rocket engine and uses LOx and kerosene as propellant are described. The gas generator consists of a injector head with F-O-F impinging injector, a water cooled combustion chamber, a gas torch igniter, a turbulence ring and an instrument ring. The effect of turbulence ring and combustion chamber length on performance of gas generator are investigated. The ignition and combustion at design point are stable and the pressure and gas temperature at gas generator exit meets the target. The turbulence ring installed at middle of chamber effectively mixes hot gas with cold gas and the effect of residence time of hot gas in gas generator on combustion efficiency is small. Test results show that the main parameter controlling the gas temperature at gas generator exit is overall O/F ratio.