• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.54-58
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• 2007

The trailers with electronically controlled diesel engine was converted to dual fuel engine system. To estimate economical efficiency, test vehicles have been operated on a certain driving route repeatedly. Fuel economy, mximum driving distance per refueling and driveability are examined on the road including a free way. Developed vehicle can be operated over 500 km with dual Hel and shows 85% of diesel substitution ratio. Driveability is similar with but passing acceleration. It will be improved by calibration process. Test engine was set up for investigating power output, thermal efficiency and emission. ND 13-mode tests were performed for the test cycle. The emission result of dual fuel meets K2006 regulation and the engine performance of dual fuel engine was equivalent to the performance of diesel engine.

• Journal of Power Electronics
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• v.13 no.5
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• pp.806-813
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• 2013

This paper aims to compare the performance of three phase induction motor drives using Five Leg Inverter (FLI) and Three Leg Inverter (TLI) configurations. An Indirect Field Oriented Control (IFOC) method using a TLI is well established and incorporated for high performance speed drives in various industries. The FLI dual motor drive system on the other hand shows good workability in the independent control of two induction motor drives simultaneously. In this experiment, the IFOC method is utilized for both drive systems, and Space Vector Pulse Width Modulation (SVPWM) is used to generate pulses for both inverters. For the FLI, the Double Zero Sequence (DZS) Injection technique is used to generate the modulation signal. The complete experiment setup is done by using a DSpace 1103 controller board. The individual motor performances are analyzed using similar schemes, equipment setups and controller parameter values. The results show similar speed performance response capability between the single motor operation using a TLI system and the two motor operation using a FLI system based on the variable speed range either in forward or reverse operation. They also show similar load rejection abilities. However, the single motor with a TLI has a better power quality aspect such as ripple current and total harmonics distortion (THD).

• Journal of Energy Engineering
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• v.25 no.1
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• pp.122-130
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• 2016

This study is a numerical study using commercial simulation program GT-Power on 1.5MW diesel engine for power generation. Performance comparison has done for diesel operation with dual fuel operation for different engine load(50%, 75%, 100%) using the target engine model with additional gas injection system. Effect of using Hi-sene, which is actually being used in island area, instead of diesel was also studied. As a result, under 60% natural gas with diesel condition, BSFC was increased by 32% without modifying system. There was almost no change for natural gas/Hi-sene condition compared with natural gas/diesel condition. Decrease of burned fuel fraction was the main reason of these phenomena. After optimizing system, BSFC was improved by 2%.

• Journal of Power System Engineering
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• v.18 no.4
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• pp.11-16
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• 2014

Although smoke emitted from ships is not included in IMO(International Maritime Organiztion) regulation yet, it is one of the substance what is polluting mainly the air. Especially, its concentration is very high when an engine is started and a load is rapidly changed. This is caused by unburned fuel what is injected more than necessary quantity after combustion period. It is possible to decrease smoke concentration emitted at starting engine by controlling fuel injection quantity, but it is concerned that time to rated speed must be spent. Then a governor what can reduce the smoke concentration without a loss of time to rated speed is needed. We adopted a electro-hydraulic governor what can control dual fuel start limit function and achieved very low level of smoke concentration without greater the loss of time to rated speed.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.45-53
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• 2022

In order to improve the emission of diesel engines, natural gas-diesel dual fuel combustion compression ignition engines are in the spotlight. In particular, a reactivity controlled compression ignition (RCCI) combustion strategy is investigated comprehensively due to its possibility to improve both efficiency and emissions. With advanced diesel direct injection timing earlier than TDC, it achieves spontaneous reaction with overall lean mixture from a homogeneous mixture in the entire cylinder area, reducing nitrogen oxides (NOx) and particulate matter (PM) and improving braking heat efficiency at the same time. However, there is a disadvantage in that the amount of incomplete combustion increases in a low load region with a relatively small amount of fuel-air. To solve this, sensitive control according to the diesel injection timing and fuel ratio is required. In this study, experiments were conducted to improve efficiency and exhaust emissions of the natural gas-diesel dual fuel engine at low load, and evaluate combustion stability according to the diesel injection timing at the operation point for power generation. A 6 L-class commercial diesel engine was used for the experiment which was conducted under a 50% load range (~50 kW) at 1,800 rpm. Two injectors with different spray patterns were applied to the experiment, and the fraction of natural gas and diesel injection timing were selected as main parameters. Based on the experimental results, it was confirmed that the brake thermal efficiency increased by up to 1.3%p in the modified injector with the narrow-angle injection added. In addition, the spray pattern of the modified injector was suitable for premixed combustion, increasing operable range in consideration of combustion instability, torque reduction, and emissions level under Tier-V level (0.4 g/kWh for NOx).

• Applied Science and Convergence Technology
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• v.26 no.6
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• pp.189-194
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• 2017

Effects of gas injection scheme and rf driving current configuration in a dual turn inductively coupled plasma (ICP) system were analyzed by 3D numerical simulation using CFD-ACE+. Injected gases from a tunable gas nozzle system (TGN) having 12 horizontal and 12 vertical nozzles showed different paths to the pumping surface. The maximum velocity from the nozzle reached Mach 2.2 with 2.2 Pa of Ar. More than half of the injected gases from the right side of the TGN were found to go to the pump without touching the wafer surface by massless particle tracing method. Gases from the vertical nozzle with 45 degree slanted angle soared up to the hottest region beneath the ceramic lid between the inner and the outer rf turn of the antenna. Under reversed driving current configuration, the highest rf power absorption region were separated into the two inner islands and the four peaked donut region.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.172-179
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• 1998

Valve lifter namely tappet is supported by lifter hole which is located upper side of camshaft in cylinder block transforms rotatic mvement of camshaft into linear movement and helps to open and shut the en-gine valve as an engine parts. The face of valve lifter which is continuously contacting with camshaft brings about abnormal wears such as unfair wear and early wear because it is severely loaded in the valve train system. These wears act as a defect like over-clearance and cause imperfect combustion of fuel during the valve lifting in the combustion chamber. Consequently this imperfect combustion makes the engine out-put decrease and has cause on air pollution. To prevent these wears therefore The valve lifter cast in me-tal developed into SiC ceramics valve lifter which has an excellence in wear and impact resistance As a results the optimum process conditions like injection condition mixture ratio and debonding process could be established. After sintering fine-sinered dual microstructure in which prior ${\alpha}$-SiC matches well with new SiC(${\beta}$-SiC) produced by reaction among the ${\alpha}$-SiC carbon and silicon was obtained. Based on the study it is verified that mechanical properties of SiC valve lifter are excellent in Vickers hardness 1100-1200 bending strength (300-350 Pa) fracture toughness(1.5-1.7 Mpa$.$m1/2) Through engine dynamo test-ing SiC valve lifter and metal valve lifter are examined and compared into abnormal phenomena such as early fracture unfair and early wear. It is hoped that this research will serve as an important springboard for the future study of heavy duty diesel engine parts developed by ceramics which has a good wear resis-tance relaibility and lightability.

• Journal of the Korean Institute of Gas
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• v.21 no.5
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• pp.9-15
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• 2017

Natural gas fuel has known to be very promising in terms of abundancy and economic value. Therefore it is widely treated as research topics in a variety field of production, storage and utilization. Natural gas has become one of the major sources for the power generation by using internal combustion engines(ICE). Development of natural gas fuel injection device should be preceded to realize a reliable natural gas fuel supply system for a MW class power generation reciprocating ICE. In this research, an injection valve which consists of solenoid and body part with a moving plate was designed and its dynamic performance was experimented in the engine-like environment. Displacement length and diameter of an armature and diameter of a solenoid coil were tested at former study. In this research the effect of materials of solenoid core, size of main housing inlet and supply gas pressure are examined.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2224-2236
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• 2014

The performance of an isolated high voltage full bridge converter is improved using a voltage doubler. In a conventional high voltage full bridge converter, the diode of the transformer secondary voltage undergoes a voltage spike due to the leakage inductance of the transformer and the resonance occurring with the parasitic capacitance of the diode. In addition, in the phase shift control, conduction loss largely increases from the freewheeling mode because of the circulating current. The efficiency of the converter is thus reduced. However, in the proposed converter, the high voltage dual converter consists of a voltage doubler because the circulating current of the converter is reduced to increase efficiency. On the other hand, in the proposed converter, an input current is distributed when using parallel input / serial output and the output voltage can be doubled. However, the voltages in the 2 serial DC links might be unbalanced due to line impedance, passive and active components impedance, and sensor error. Considering these problems, DC injection is performed due to the complementary operations of half bridge inverters as well as the disadvantage of the unbalance in the DC link. Therefore, the serial output of the converter needs to control the balance of the algorithm. In this paper, the performance of the conventional converter is improved and a balance control algorithm is proposed for the proposed converter. Also, the system of the 1.5[kW] PCS is verified through an experiment examining the operation and stability.

• 연구논문집
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• s.27
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• pp.75-86
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• 1997

Combined cycle power plant is a system where a gas turbine or steam turbine is used to produce shaft power to drive a generator for producing electrical power and the steam from the HRSG is expanded in a steam turbine for additional shaft power. Combined cycle plant is a one from of cogeneration. The temperature of the exhaust gases from a gas turbine ranges from $400^\circC$ to $600^\circC$, and can be used effectively in a heat recovery steam generator to produce steam. Combined cycle can be classed as a "topping(gas turbine)" and a "bottoming(steam turbine)" cycle. The first cycle, to which most of the heat is supplied, is called the topping cycle. The wasted heat it produces is then utilized in a second process which operates at a lower temperature level and is therefore referred to as a "bottoming cycle". The combination of gas/steam turbine power plant managed to be accepted widely because, first, each individual system has already proven themselves in power plants with a single cycle, therefore, the development costs are low. Secondly, the air as a working medium is relatively non-problematic and inexpensive and can be used in gas turbines at an elevated temperature level over $1000^\circC$. The steam process uses water, which is likewise inexpensive and widely available, but better suited for the medium and low temperature ranges. It, therefore, is quite reasonable to use the steam process for the bottoming cycle. Only recently gas turbines attained inlet temperature that make it possible to design a highly efficient combined cycle. In the present study, performance analysis of a dual pressure combined-cycle power plant is carried out to investigate the influence of topping cycle to combined cycle performance.