• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.69-76
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• 2013

In this paper, electronic ballast using resonant inverter for HID lamp is designed and implemented. The proposed electronic ballast is used the soft switching technology ZVS(Zero Voltage Switching) to reduce turn-on and turn-off loss. The ignition of proposed electronic ballast is achieved by controlling a full bridge inverter which is consisted of LC filter for resonance. After ignition the ballast operates as a low frequency square wave inverter by controlling a full bridge inverter as a buck converter. After ignition at resonant frequency of $f_o$=160kHz, the switching frequency of a buck converter is consisted of 50kHz of high frequency and 170Hz of low frequency. This is for attenuating high frequency harmonics and avoiding acoustic resonance. The experimental results show that electronic ballast using resonant inverter is operated stably.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.373-376
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• 2009

A full rig combustor test and altitude ignition test were carried out for radial-annular combustor of micro turbojet engine. 11.2% total pressure loss and 99.85% of combustion efficiency were measured at design point of engine under sea level standard condition and $2{\sim}6$ of air excess ratio for ignition envelope was achieved on engine starting regime. Finally, A 30,000 ft high altitude ignition test was also performed and finally we found out that the developed radial-annular combustor is appropriate to micro turbojet engine.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.1
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• pp.24-34
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• 1985

The study of unsteady gas exchange processes in the inlet and exhaust systems of the single-cylinder 4-stroke cycle spark ignition engine is presented in this paper. The generalized method of characteristics including friction, heat transfer, change of flow area and entropy gradients was used for solving the equations defining the gas exchange process. The path line calculation was also conducted to allow for calculation of the gas composition and entropy change along the path lines, and of the variable specific heat due to the change of temperature and composition. As the result of the simulation, the properties at each point in the inlet and exhaust pipe, pressure and temperature in the cylinder, and charging efficiency were obtained. Pumping loss and residual gas fraction were also computed. The effect of engine speed, exhaust and inlet pipe length on the pumping loss and charging efficiency were studied showing that the results were in agreement with what has been known from experiments.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.2
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• pp.225-230
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• 2017

Coal oil is widely used as a home heating fuel for portable and installed coal oil heaters. Today, Coal oil is widely used as fuel for jet engines and some rocket engines in several grades. This paper describes the performance characteristics according to the compression ratio of spark ignition engine fuelled with coal oil. As a result, the following knowledge is obtained: As the compression ratio is decreased, there is an increase in torque, indicated mean effective pressure (IMEP), heat release rate, and brake thermal efficiency. Higher compression ratio of the engine decreases the ignition delay period, combustion period, and cooling loss.

• Fire Science and Engineering
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• v.27 no.6
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• pp.50-56
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• 2013

The radiation effects on the auto-ignition and extinction characteristics of a non-premixed fuel-air counterflow field were numerically investigated. A detailed reaction mechanism of GRI-v3.0 was used for the calculation of chemical reactions and the optically-thin radiation model was adopted in the simulations. The flame-controlling continuation method was also used in the simulation to predict the auto-ignition point and extinction limits precisely. As a result, it was found that the maximum H radical concentration, $(Y_H)_{max}$, rather than the maximum temperature was suitable to understand the ignition and extinction behaviors. S-, C- and O-curves, which were well known from the previous theory, were identified by investigating the $(Y_H)_{max}$. The radiative heat loss fraction ($f_r$) and spatially-integrated heat release rate (IHRR) were introduced to grasp each extinction mechanism. It was also found that the $f_r$ was the highest at the radiative extinction limit. At the flame stretch extinction limit, the flame was extinguished due to the conductive heat loss which attributed to the high strain rate although the heat release rate was the highest. The radiation affected on the radiative extinction limit and auto-ignition point considerably, however the effect on the flame stretch extinction limit was negligible. A stable flame regime defined by the region between each extinction limit became wide with increasing the fuel temperature.

• Journal of the Korean Institute of Gas
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• v.11 no.2 s.35
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• pp.10-14
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• 2007

Flash point is one of the major physical properties used to evaluate fire hazards of the combustible liquids. Properties showing relative fire hazards of the combustible liquids are heat release rate(HRR), peak heat release rate(PHRR), time to ignition(TTI), mass loss rate, and yield of $CO/CO_2$. The relationships between flash points and fire properties of the combustible liquids were examined in this study. For this study, mass loss rate and time to ignition were measured to calculate fire properties of the combustible liquids. The results showed that good correlations could be found between flash point and time to ignition, time to peak heat release rate, and the propensity to flashover. From a presented results, the parameters can be used to evaluate relative hazards of the combustible liquids on fire.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.21-30
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• 2005

Heat release analysis is a very importent method in understanding the combustion phenomena inside an engine cylinder. In this study, one-zone heat release analysis was used with the mesured cylinder pressures of an IDI(indirect injection), a HSDI(high speed direct injection) and a SI(spark ignition) engine. It has benefits of simple equation, fast speed, reliability. The object of the study is to compare the combustion characteristics among an IDI, a HSDI and SI engine. Result of analysis, the maximum heat release rate of a HSDI is higher than an IDI because of long ignition delay period. The heat release curve of a IDI is more linear than an HSDI, so the combustion characteristics of a IDI is similiar to that of an SI engine. There is a suggestion here that the combustion efficiency of a HSDI is highest of that of all engines because of the smallest heat transfer loss of all engines.

• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.1
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• pp.87-98
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• 1994

Sludge minimization in an water treatment plant can be achieved by optimizing a main water treatment process as well as by enhancing a thickening and a dewatering facilities. In this study, dewatering and drying techniques for reducing the quantity of the water sludge generated from the conventional water treatment plant in the local states were investigated by reducing its water content. Not only the types and dosages of polymers but also the mixing intensity of the mixtures of a concentrated sludge and polymers on the different pH were evaluated for the optimum dewatering conditions of the water sludge. Weight reduction of the water sludge was also tested at a given temperature range. The dewatering efficiency of the water sludge was not affected by the types of polymer but by mixing intensity(GT value) in this study. pH effect on dewaterbility of the water sludge took a major role at the neutral pH range. The optimal polymer dose was 1.5 mg-polymer/g-TSS(about 40mg/L as polymer). Dewaterability was enhanced at a lower mixing intensity(GTbelow 10,000 sec-1). Free water in the void of sludge cake was dried around $100^{\circ}C$, chemical bound water was evaporated around $320^{\circ}C$, and organic material was burned out at the range of 300 to $600^{\circ}C$. Ignition losses of the water sludge were varied 15 to 40 % as the raw water quality. The ignition loss due to the chemical bound water was 10-20% and the loss due to the organic material was 4-20% of the total ignition loss.

• Fire Science and Engineering
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• v.14 no.1
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• pp.8-12
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• 2000

We had investigated thermal and ignition behaviors of textiles. Decomposition of textiles with temperature was investigated using a DSC and the weight loss according to temperature using a TGA in order to find the thermal hazard of textiles, and the ignition behaviors of textiles according to species and permeation amount of oil. In addition, ignition behaviors of those permeated into oils indicating different iodine value and of those with arid without air in reaction vessel of measuring equipment were studied with constant temperature method among ignition temperature measuring methods. As results, the range of decomposition temperature of synthetic fiber was slightly broad compared with that of natural fiber, pure cotton. Besides, the initiation temperature of heat generation of both samples riced in the case of no air injection in the reaction vessel. On the other hand, in the case of air injection that was lowered according to the increase in permeative amount of oils and fats and decreased quickly as sample was permeated into drying oil.

• Journal of Wetlands Research
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• v.10 no.3
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• pp.27-35
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• 2008

Sediment cores were obtained from Upo and Mokpo in Upo Wetland and core samples were divided by depth into 20 ~ 21 subsamples. The heavy metal concentrations of Fe, Mn, Zn, AS, Cu, Cd, Ni, Pb, and Cr in the sediments of each depth were determined by ICP-MS. The texture of sediemnts from Upo Wetland appeared to be clayey silt with average grain size of $7.52{\sim}11.15{\mu}m$ for physical properties. It was found to have a clear tendency of depth profile with respect to TOC and ignition loss. Organics were stabilized in the range of 0.5 ~ 0.7 % TOC and 8 ~ 9 % ignition loss in 30 years, whereas, the surficial sediments have the highest concentrations of about 3.0 % of TOC and 13 ~ 15 % ignition loss. Those are much higher than the values of the main stream, the Nakdong River, which reflects the deposit of biodegradable organics from plants and other lifes. The vertical distribution of heavy metals in two sediment cores was investigated to elucidate historical trends of heavy metals deposited into Upo wetland. The depth profile concentrations of each heavy metal were compared and discussed with the Concensus-Based Sediment Quality Guidelines for freshwater ecosystems. All the Cd data for the vertical distribution in the sediments were detected above PEC value for Cd, which predict harmful effects on sediment-dwelling organisms expected to occur frequently. The concentrations of Zn, Cu, and Cr in all sediment samples for depth profile were detected below the TEC values, which provided a basis predicting the absence of toxicity by Zn, Cu, and Cr.