• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.967-975
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• 2000

Transient characteristics of a boiler and turbine system for a steam power plant are simulated. One-dimensional unsteady models are introduced for each component. An interaction between boiler and turbine and a control of the water level in the drum are taken into account. Transient responses of the system to the variations of main system variables such as fuel and air flow rate, cooling water injection rate at the attemperator, gas recirculation rate at the furnace and opening of the turbine control valve are examined. Effect of fluid inertia and tube wall thermal inertia on predicted dynamic behavior is investigated.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.6
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• pp.17-22
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• 2011

This study is to investigate the effect of the cetane number in ultra low sulfur diesel fuel on combustion characteristics and exhaust emissions at 1500 rpm and 2.6bar BMEP in low-temperature diesel combustion with 1.9L common rail direct injection diesel engine. Low-temperature diesel combustion was achieved by adopting external high EGR rate with the strategic injection control without modification of engine components. Test fuels are ultra low sulfur diesel fuel (sulfur less than 12 ppm) with two cetane numbers (CN), i.e., CN30 and CN55. For the CN30 fuel, as a start of injection (SOI) timing is retarded, the duration of an ignition delay was decreased while still longer than $20^{\circ}CA$ for all the SOI timings. In the meanwhile, the CN55 fuel showed that an ignition delay was monotonically extended as an SOI timing is retarded but much shorter than that of the CN30 fuel. The duration of combustion for both fuels was increased as an SOI timing is retarded. For the SOI timing for the minimum BSFC, the CN30 produced nearly zero PM much less than the CN55, while keeping the level of NOx and the fuel consumption similar to the CN55 fuel. However, the CN30 produced more THC and CO than the CN55 fuel, which may come from the longer ignition delay of CN30 to make fuel and air over-mixed.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.72-77
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• 2011

This study is to investigate the effect of the distillation temperature in ultra low sulfur diesel fuel on exhaust emissions in the low-temperature diesel combustion with 1.9L common rail direct injection diesel engine. Low temperature diesel combustion was achieved by adopting an external high EGR rate with a strategic injection control. The engine was operated at 1500 rpm 2.6 bar BMEP. The 90% distillation recovery temperature (T90) was $270^{\circ}C$ and $340^{\circ}C$ for the respective cetane number (CN) 30 and 55. It was found that there exists no distinctive discrepancy on exhaust emissions with regards to the different T90s. The high CN (CN55) fuels follow the similar trend of exhaust emissions as observed in CN30 fuels' except that high T90 fuel (CN55-T340) produced higher PM compared to low T90 fuel (CN55-T270). This may come from that high T90 plays an active role in aggravating the degree of fuel-air mixture preparedness before ignition.

• Journal of the Korean Society of Combustion
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• v.3 no.2
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• pp.13-27
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• 1998

The optimization of frontal device including fuel nozzle and swirler is required to secure the mixing of fuel and air and the combustion stability leading the reduction of pollutant emissions and the increase of combustion efficiency in gas turbine combustor. The effects of injection nozzle and swirler on the flow field, spray characteristics and consequently the combustion stability, were experimentally investigated by measuring the velocity field, droplet sizes of fuel spray, lean combustion limit and the temperature field in the main combustion region. Flow fields and spray characteristics were measured with APV(Adaptive Phase Doppler Velocimetry) under atmospheric condition using kerosine fuel. Temperatures were measured by Pt-Pt13%Rh, R-type thermocouple which was 0.2mm thick. Spray and flame was visualized by ICCD(Intensified Charge Coupled Device) camera. It was found that the dual swirler resulted in the biggest recirculation zone with the highest reverse flow velocity at the central region, which lead the most stable combustion. The various combustion characteristics were observed as a function of the geometries of injector and swirler, that gave a tip for the better design of gas turbine combustor.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.4
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• pp.392-400
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• 2016

In this paper, a study based on engine operating conditions versus hybrid excavator engines was conducted about the engine performance and fuel consumption via the 1-D engine simulation model. First of all, engine operating points with performance and emission were determined by driving patterns. The 1-D HFEM(High Frequency Engine Model) was developed for deep insight into engine combustion and the energy conversion phenomena. In accordance with changing operating points, especially High Idle and Rated output conditions, engine parameters and systems such as turbocharger(Waste Gate Turbocharger and Variable Geometry Turbocharger) injection strategies and EGR(Exhaust Gas Recirculation) should be considered. Therefore, various configurations and parametric analysis with optimization methods in hybrid excavator were simulated and optimized by NLPQL(Non-linear Programming by Quadratic Lagrangian algorithm) in 1-D HFEM. As a result, the fuel consumption with the developed hybrid electric excavator engine could be significantly decreased and bsfc(Brake Specific Fuel Consumption) was also reduced about 5 % to 7 % without any performance degradation.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.7
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• pp.1123-1130
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• 2004

Numerical simulations have been carried out to investigate the effect of nozzle hole geometry on the combustion characteristics of the large diesel engine. 6S90MC-C. Spray and combustion phenomena were examined numerically using FIRE code. Wane breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation processes. Predictions on the cylinder peak pressure and NOx emission were first verified with the experimental data to confirm the reliability of numerical calculations. The comparison results showed good agreements within the range of 0.64% and 4.6% respectively. Finally, the effects of fuel spray angle and diameter on the engine performance were investigated numerically to find the optimum nozzle hole geometry considering fuel consumption, NOx emission and heat flux of the combustion chamber wall. It was concluded that the combustion gas recirculation in cylinder by changing fuel injection direction is an effective method to reduce NOx emission by about 10% with increasing fuel oil consumption, 1.4% in a large diesel engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.134-139
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• 2008

This research investigated variations of the engine performance and the exhaust emission characteristic of a direct injection diesel engine by fueling a commercial diesel fuel, which was blended with the di-ether group (butyl-ether: BE). The smoke emission reduced to 26% from the diesel engine with the blending fuel (diesel fuel 80 vol-% + BE 20 vol-%)at the full engine load of 2500 rpm compared to it with the diesel fuel only. The power, torque and brake specific energy consumption of the diesel engine showed very slight differences. The NOx emission from the diesel engine, however, with the blended fuel was higher than with the commercial diesel fuel only. By applying EGR method, as a counter plan of the NOx reduction, this research obtained reductions of the smoke and NOx emission at the same time from the diesel engine with the BE blended diesel fuel.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.9-21
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• 1998

The optimization of frontal device including fuel nozzle and swirler is required to secure the mixing of fuel and air, and the combustion stability in the gas turbine combustor design for the reduction of pollutant emissions and the increase of combustion efficiency. The effects of injection nozzle and swirler on the flow field, spray characteristics and consequently the combustion stability, were experimentally investigated by measuring the velocity field, droplet sizes of fuel spray, lean combustion limit and the temperature field in the main combustion region. The effect of fuel injection nozzle was tested by adopting three different nozzles; a dual orifice fuel nozzle, a hollow cone nozzle and a solid cone nozzle. These tests were combined with the three different swirler geometries; a dual-stage swirler with 40$^{\circ}$ /-4 5$^{\circ}$ vanes and two single-stage swirlers with 40$^{\circ}$ vane angle having 12 and 16vanes, respectively. Flow fields and spray characteristics were measured with APV(Adaptive Phase Doppler Velocimetry) under atmospheric condition using kerosine fuel. Temperatures were measured by Pt-PtI3%Rh, R-type thermocouple which was 0.2mm thick. It was found that the dual swirler resulted in the biggest recirculation zone with the highest reverse flow velocity at the central region, which lead the most stable combustion. The various combustion characteristics were observed as a function of the combination between the injector and swirler, that gave a tip for the better design of gas turbine combustor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.337-344
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• 2011

The humidification of reactant gases is crucial for efficiently operating PEM (polymer electrolyte membrane) fuel cell systems and for improving the durability of these systems. The recycle of the energy and water vapor of exhaust gas improves the system performance especially in the case of automotive application. The available humidification methods are steam injection, nozzle spray, humidification by enthalpy wheel, membrane humidifier, etc. However, these methods do not satisfy certain requirements such as compact design, efficient operation and control. In this study, a hybrid humidification system consisting of a membrane humidifier and exhaust-air recirculation units was developed and the humidification performance of this hybrid humidifier was analyzed. Finally, a new practical method for optimal design of PEM-fuel-cell humidification system is proposed.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.58-64
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• 2006

Homogeneous charge compression ignition(HCCI) combustion is an advanced technique for reducing the hazardous nitrogen oxide(NOx) and particulate matter(PM) in a diesel engine. NOx could be reduced by achieving lean homogeneous mixture resulting in combustion temperature. PM could be also reduced by eliminating fuel-rich zones which exist in conventional diesel combustion. However previous researches have reported that power-output of HCCI engine is limited by the high intensive knock and misfiring. In an attempt to extend the upper load limit for HCCI operation, supercharging in combination with Exhaust Gas Recirculation(EGR) has been applied: supercharging to increase the power density and EGR to control the combustion phase. The test was performed in a single cylinder engine operated at 1200 rpm. Boost pressures of 1.1 and 1.2 bar were applied. High EGR rates up to 45% were supplied. Most of fuel was injected at early timing to make homogeneous mixture. Small amount of fuel injection was followed near TDC to assist ignition. Results showed increasing boost pressure resulted in much higher power-output. Optimal EGR rate influenced by longer ignition delay and charge dilution simultaneously was observed.