• Journal of Power System Engineering
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• v.9 no.4
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• pp.214-219
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• 2005

The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 72MPa to 112MPa by using a common rail injection system(ECD-U2). The images of liquid and vapor phase in the evaporating free diesel spray are simultaneously taken by exciplex fluorescence method. As a result, it can be confirmed that the distribution of vapor concentration is more uniform in the case of the high injection than in that of the low injection pressure.

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.216-225
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• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.796-801
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• 2011

The objective of this work presented here was focused on analysis of development trend for the integrated power system of naval vessels to perform the high-power and energy mission load platform. These mission loads are affected by the high level of military technologies, digitalization of the ocean battlefield, high power sensor system for maximization of the ship survivability. All electric power including propulsion power for ship should be controlled by integrated single system in order to carry various high power density weapon system such as Electromagnetic Aircraft Launch System, Electromagnetic Rail Gun[feasible precision striking at long distance 200NM(370km) or over]. As the analyzing the present state of things, mechanical propulsion system is shifted into hybrid or fully electric propulsion systems to realize integrated power system at the developed countries. Such challenges include reduced dependency on foreign-supplied fossil fuel, increasing demand for installed ship power, controlling life-cycle costs.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.4
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• pp.508-514
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• 2010

The objective of this work presented here was experimental study of steadystate and cold start exhaust nano-sized particle characteristics from common rail diesel engine. The effect of the diesel oxidation catalyst (DOC) on the particle number reduction was insignificant, however, particle number concentration levels were reduced by 3 orders of magnitude into the downstream of diesel particulate filter (DPF). In high speed and load conditions, natural regeneration of trapped particle occurred inside DPF and it was referable to increase particle number concentration. As fuel injection timing was shifted BTDC $6^{\circ}CA$ to ATDC $4^{\circ}CA$, particle number concentration level was slightly reduced, however particle number and size was increased at ATDC $9^{\circ}CA$. Nucleation type particle reduced and accumulation type particle was increased on EGR condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.12
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• pp.1151-1159
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• 2012

Spray visualization and computer simulation of a DME injector have been conducted to investigate the enlarged injection hole diameter effect. To increase the reliability of the computational result, simulation results have been compared with the visualization test results, and the behaviors of a DME spray under various high-pressure and -temperature conditions have been computed. This study shows a discrepancy of 3.57% between the experimental and the computational results of penetration length for an injection pressure of 35 MPa and ambient pressure of 5 MPa. When simulating the engine conditions, the maximum penetration length of a fully developed DME spray is 42 mm when the temperature to pressure ratio is 300 K/MPa. The DME spray behavior is dominantly affected by the ambient pressure under the condition that the ratio is less than 300 K/MPa, and by the ambient temperature under the condition that the ratio is more than 300 K/MPa.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.7
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• pp.745-752
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• 2012

Diesel engines are most suitable for biodiesel fuel because diesel fuel has a higher cetane number compared to gasoline and diesel engines have no spark ignition system; hence, engine conversion is easy and cost effective. For these reasons, in this study, the spray behavior characteristics of vegetable palm oil were analyzed by using a common-rail injection system of a commercial diesel engine, and the results were compared with those obtained for the diesel fuel. The injection pressures and blend ratios of palm oil and diesel fuel (BD3, BD5, BD20, BD30, BD50, and BD100) were the main parameters. The experiments were conducted for different injection pressures-500 bar, 1000 bar, 1500 bar, and 1600 bar-by setting the injection duration at $500{\mu}s$. We determined there is no significant difference in the macro characteristics of the spray behavior (spray penetration and spray angle) in response to any change in the blend ratio of palm oil and diesel fuel at a fixed injection pressure. In particular, all experiments showed a spray angle of approximately $15^{\circ}$.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.8
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• pp.459-467
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• 2016

In order to assess the pollution status and distribution characteristics of PM and PM-bound species, PM10 samples were collected using mini-volume air sampler at the subway cabin in Daejeon city. Measurements of about 24 elements including toxic metals (e.g., As, Cr, Mn, V, Zn) in PM10 were made by instrumental neutron activation analysis and X-ray fluorescence. The average PM10 concentration was $59.3{\pm}14.5{\mu}g/m^3$ in the subway cabin with a range of 42.2 to $97.4{\mu}g/m^3$, while the associated elemental concentrations were varied in the range of $10^{-3}$ to $10^5ng/m^3$. It was found that the concentration of Fe ($12.5{\mu}g/m^3$) was substantially higher than any other element. The Fe concentration was apportioned by about 20% of the PM10 concentration. The results of factor analysis indicate that there are no more than six sources in the cabin (e.g., brake-nonferrous metal particle, resuspended rail dust, fuel combustion, vehicle exhaust, black carbon, Cr-related).

• Journal of Biosystems Engineering
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• v.6 no.1
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• pp.60-72
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• 1981

This study was carried out to find out the effects of the sheaf size of paddy harvested by the binders on the threshing performance, load characteristics and power requirement of an auto-feed thresher. The results of the study are summarized as follows: 1. The seperating performance of the thresher appeared to be satisfactory for all the sheaf sizes although the amount of rubbishes and empty grains slightly increased with the sheaf size of paddy. 2. There was no significant difference in grain output quality of the thresher among the three sheaf sizes. However, the amount of grains left unthreshed increased with the sheaf size. In the case of the largest sheaf size with the feed rate of 780kg/h, it exceeded the limit set by the national inspection regulations. 3. The position of the feed-chain rail gave a significant effect on the power requirement of the thresher. At the feed rate of 780kg/h, the net power required to convey sheafs through the feed chain was in the range of 0.37 to 0.50 PS for the middle and lowest position of feed-chain rail, and there was no significant difference among the sheaf sizes. At the highest position, however, it appeared that the smallest sheaf required more power than the others. The net power requirements at this position were 1.03, 0.59. 0.65 PS for the smallest, medium and largest sheafs respectively. 4. The torques of both the thresher and the engine shaft increased with the feed rate and were not affected by the sheaf size for the lower two feed rates of 520 and 780kg/h. At the highest feed rate of 1,040 kg/h, however, they were affected by the sheaf size. In this case, the medium sheaf size gave lower values than the others. 5. The variations in the thresher and the engine torque increased with the feed rate and were not affected by the sheaf size for the feed rate of 520kg/h. At the feed rate of 780kg/h, however, they increased with sheaf size. And at the feed rate of 1,040 kg/h, the torque variations increased greatly for all the sheaf sizes due to an over-load operating condition. 6. It appeared that the average and maximum power requirements of the thresher increased with the feed rate. But, there was no significant difference in power requirement among the sheaf sizes for the lower two feed rates. 7. The threshing efficiency of the thresher was in the range of 214-249 kg/ps.h with the feed rates of 520 and 780 kg/h, and it was not affected by both the sheaf size and the feed rate. At the feed rate of 1,040 kg/h, however, it decreased to as low as 171-174 kg/ps.h because of a sudden increase in power requirement. 8. The average power requirements of the engine were slightly higher than those of the thresher due to the slippage of flat belt between the thresher and engine. It appeared that power transmission from the engine to the thresher was maintained properly since slippages were moderately low with the range of 2.78 to 6.51% throughout the tests. 9. The specific fuel consumption of the engine (diesel 8PS) decreased as the feed rate increased. However, there was no significant reduction in specific fuel consumption as the feed rate increased above 780 kg/h.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.111-120
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• 2014

The aim of this study is to develop an integrated urea-SCR catalytic filter system for reducing soot and $NO_X$ emissions simultaneously in diesel engines. In this study, the characteristics of exhaust emissions relative to reactive activation temperature under four kinds of engine loads are experimentally investigated by using a four-cycle, four-cylinder, direct injection type, water-cooled turbo intercooler ECU common-rail diesel engine with the integrated urea-SCR $MnO_2-V_2O_5-WO_3/TiO_2/SiC$ catalytic filter system operating at three kinds of engine speeds. The urea-SCR reactor is used to reduce $NO_X$ emissions, and the catalytic filter system is used to reduce soot emissions. The reactive activation temperature is very important for reacting a reducing agent with exhaust emissions. The reactive activation temperatures in this experiment is applied to 523, 573 and 623 K. The fuel is sprayed by the pilot and main injections at the variable injection timing between BTDC $15^{\circ}$ and ATDC $1^{\circ}$ according to experimental conditions. It is found that the $NO_X$ conversion rate is the highest as 83.9% at the reactive activation temperature of 523 K in all experimental conditions of engine speed and load, and the soot emissions shown by the average reduction rate of approximately 93.3% are almost decreased below 0.6% in all experimental conditions regardless of reactive activation temperatures. Also, the THC and CO emissions by oxidation reaction of Mn, V and Ti are shown in the average reduction rates of 70.3% and 38% regardless of all experimental conditions.

• Journal of Korea Port Economic Association
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• v.23 no.1
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• pp.95-113
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• 2007

Recently, International institution such as IMO and major maritime countries have introduced various regulations and steps to reduce port pollution. However, recognition of environmental pollution from ports is not sufficient for Korean policy makers and port communities. The purpose of this paper is to examine solutions to port pollution problems and suggests some implications to Korean ports to become a green port. To this aim, necessity of regulation on environmental pollution from port operation; literature survey on port's environmental pollution; current conditions of international port pollution; various regulations and policies governing major ports are conducted in this paper. Our main findings are as follows; first, air pollution from ship can be reduced by providing electric power at docks while at berth, Second, in case of cargo-handling equipment, retire old equipment and switch to cleaner fuel such as low-sulfur fuel and diesel emulsions. Third, offering incentives for the installation of pollution controls and minimizing idling by enforcing idling limits or by installing idle shutoff controls can be recommended for reduction of air pollution of truck and rail at ports.