• Journal of the Korean Institute of Gas
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• v.15 no.5
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• pp.25-30
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• 2011

Biogas obtained from the biodegradable organic wastes in an anaerobic digester consists of $CH_4$ and inert gases such as $CO_2$ and $N_2$. Since the composition of biogas varies by anaerobic digester conditions and the origin of wastes, it is necessary to respond to these variations so as to make stable combustion and accomplish high efficiency when it is used as a fuel for power generating SI engines. In this study, efforts have been made to investigate the effect of changes in the calorific values of biogas on the engine performance and exhaust characteristics. The biogas was simulated by supplying of $CH_4$ with $N_2$ dilution of various ratios, and ECM was developed to achieve accurate control of ignition and combustion. The results show that as the $CH_4$ concentration of the biogas decreases, the optimal spark timing is advanced due to the elevated thermal capacity and lowered $O_2$ concentration of the in-cylinder charge. Furthermore, since combustion temperature was reduced by increased inert gas, $NO_x$ emissions decreased, whereas THC emissions increased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.610-616
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• 2020

Recently, the application of a photocatalyst to road structures is being attempted to solve environmental problems caused by fine particulate matter and automobile exhaust. The purpose of this study was to develop a release agent with GST (low-cost, high-performance photocatalyst produced from wastewater sludge). For this, the method of mixing and dispersing GST with the release agent was used first, and the removal performance of nitrogen oxide (NOx) was then checked. The best performance without a precipitation reaction was achieved using a stabilizing agent at 20 % in an outdoor exposure test for four weeks. The NO and NOx removal rate of the specimen demolded by applying the GST release agent developed in this study showed excellent effects of 200 to 400 % compared to the Plain material. To increase the performance of the GST release agent, it is necessary to improve the dispersibility of GST in the release agent and increase the amount of the nano-sized photocatalyst. In addition, the use of GST release agent in road structures and exposed concrete is expected to increase the NOx removal efficiency.

• Journal of environmental and Sanitary engineering
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• v.18 no.3 s.49
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• pp.27-34
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• 2003

An objective of local exhaust hood design is to design the hood to operate as efficiently as possible. The greatest loss normally occurs at the entrance to the duct, due to the vena contracta in the throat of the duct. This can be accomplished by minimizing the loss that results from the vena contracta. There have been little studied to be cost-effective approach as installing simple instrument inside the throat of the hood. The aims of this paper were to minimize entry loss using inner square, and to measure the effect of inner square when installed inside hood throat. The results of this study were as follows; First, the magnitude of vena contracta could be considered as the difference between direct measured velocity and calculated velocity, which is from Bernoulli theory. In circle hood, calculated velocity and direct measured velocity were 10.7m/sec and 10.3n/sec, respectively. And the calculated velocity and direct measured velocity in square hood were 7.7m./sec and 6.5m/sec, respectively. Second, effect of inner square by width was carried out. The widths of inner square were L/1(18cm), L/2(9cm), L/3(6cm) and L/6(3cm). In case inner square was installed with 3cm width, the entry of coefficient was 0.93, comparing with 0.85 of entry of coefficient of general hood. Third, effect of inner square by distance from hood inside surface to inner square was carried out. The distances were L/3(6cm), L/6(3cm), L/9(2cm) and L/l8(1cm). In case the distance was 3cm the best efficiency was shown (Ce= 0.93). Fourth, effect of inner square by location from hood entry to duct inside was carried out. The locations of inner square were entry(0cm), L/6(3cm), L/3(6cm), L/2(9cm) and L/l(12cm). In case the location was 0cm, 3cm and 6cm the entry of coefficients were 0.93, 0.92 and 0.90, respectively.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.402-410
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• 2012

A two-loop Rankine cycle for engine waste heat recovery of gasoline vehicle has been investigated. Water-steam cycle as a high-temperature (HT) loop for exhaust gas heat recovery and R-134a cycle as a low-temperature (LT) loop for both heat recovery of the engine coolant and the residual heat from the HT loop were considered. Energy and exergy analysis was performed to investigate the performance of the system. Because two volumetric expanders are used for the HT and LT loop, the sizes of two expanders are very important for the optimization of the system. The effects of pressure ratio of the HT loop, considering the size of the HT expander, and the condensation temperature of LT loop on the performance of the system at a target engine condition were investigated. This study shows that about 20% of additional power from the engine waste heat recovery can be obtained at the target engine condition.

• Journal of Animal Science and Technology
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• v.44 no.4
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• pp.475-482
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• 2002

The experiment was conducted to evaluate a ventilation system, which was devised to encourage farmers to use the enclosed poultry housing system. The study was observed in the National Livestock Research Institute from May 9 to May 30 in 2002. The main results of the experiment are as follows: 1. Although the outside temperature of the enclosed poultry house was 9.6 ${\sim}$ 21.2$^{\circ}C$ with 11.6$^{\circ}C$ variation, the house with an excellent heat insulation was maintained at 32${\sim}$33$^{\circ}C$ in a variation of 2$^{\circ}C$ which is within the range of the optimal temperature for broiler, being aided with two small electric heaters. 2. The average of air flow rates of the upper, middle and low parts of the room in the broiler house were detected at 0.57, 0.22 and 0.04 m/sec, respectively. The air flow in the whole room was distibuted uniformly by a perforated duct. In conclusion, heat and humidity could be controlled without any problem in this enclosed housing system. Especially, air flow in all parts of the room was detected in uniform rates, resulting in the better ventilation performance with air inhalation through the duct and air exhaust through the side walls of the house.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.28-36
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• 2018

Islands are supplied with power from diesel generation or from photovoltaic power generation, and problems with offshore environmental impacts (age deterioration, salt pollution), environmental pollution (exhaust gas, noise, dust) and power generation costs (installation, maintenance) have increasingly emerged. In 2016, the cost recovery rate was only 27%, and deficits reached 73% on 65 islands managed by KEPCO. In terms of deficits, the costs incurred in the power generation sector accounted for 91%, with the ratio of fixed costs at about 60%. Analysis suggests that operating costs can be reduced with an optimal power supply system that improves power generation efficiency and makes operating systems more efficient. Therefore, it is possible to simplify fuel transportation and facility maintenance, because one island integrates the power plants of remote islands, and offshore cable is used to supply power to the other islands. From the economic evaluations in this paper, an algorithm deciding offshore cable layout validity for an integrated power supply between adjacent islands is presented. Simulation results based on the proposed algorithm confirmed that an integrated power supply is economical for existing stand-alone operations on islands having diesel generation, low peak power, and near distances.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.1005-1012
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• 2011

This research carried out a 3-dimensional simulation using computerized fluid dynamics (CFD) for the flow characteristics, temperature distribution, velocity distribution and residence time, etc. in a reactor in order to derive the optimal combustion conditions of an innovative combustion system. The area-weighted average temperature of the outlet of a furnace during combustion at a condition of fuel input rate 1.5 ton/hr, residence time 1.25 sec and air/fuel ratio 2.1 was $1,077^{\circ}C$, which is a suitable temperature for energy recovery and treatment of air pollutants. Exhaust gas is discharged through a duct at a 40~50 m/s maximum speed along strong vortexes at the center of a combustion chamber, so strong turbulence is created at the center of a combustion chamber to enhance the combustion speed and combustion efficiency. In this system, the optimum operation conditions to prevent incomplete combustion and suppress the formation of thermal NOx were air/fuel ratio 1.9~2.1 and fuel input rate 1.25~1.5 ton/hr.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.345-350
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• 2017

Downsizing is widely applied to diesel engines in order to improve fuel efficiency and reduce exhaust emissions. Engine sizes are becoming smaller but pressure and temperature inside combustion chambers are increasing. Therefore, research for fuel spray under high pressure and temperature conditions is important. A constant volume chamber which simulates high temperature and pressure likely to be found in diesel engines was developed in this study. Pressure and temperature were increased abruptly because of ignition of the pre-mixture in the constant volume chamber. Then pressure and temperature were gradually decreased due to the heat loss through the chamber wall. Fuel spray occurred when temperature and pressure were reached at the target condition. In this experiment, the temperature condition should be exactly defined to understand the relation between fuel evaporation and ambient temperature. A fast response thermocouple was developed and used to measure the temporal and spatial temperature distribution during the combustion process inside the combustion chamber. In the results, the core temperature was slightly higher than the bulk temperature calculated by the gas equation. Ed-note: do you want to say 'ideal gas equation'? This was attributed to the heat transfer loss through the chamber wall. The vertical temperature deviation was higher than the horizontal temperature deviation by 5% which resulted from the buoyancy effect.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.13-29
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• 2016

In this study, we analyzed the causes of major faults in the biogas plant through the case of gas engine failure when cogenerating electricity and heat using biogas as a fuel in the actual sewage treatment plant and suggested countermeasures. Hydrogen sulfide in the biogas entering the biogas engine and water caused by intermittent malfunction of the water removal system caused intercooler corrosion in the biogas engine. In addition, the siloxane in the biogas forms a silicate compound with silicon dioxide, which causes scratches and wear of the piston surface and the inner wall of the cylinder liner. The substances attached to the combustion chamber and the exhaust system were analyzed to be combined with hydrogen sulfide and other impurities. It is believed that hydrogen sulfide was supplied to the desulfurization plant for a long period of time because of the high content of hydrogen sulfide (more than 50ppm) in the biogas and the hydrogen sulfide was introduced into the engine due to the decrease of the removal efficiency due to the breakthrough point of the activated carbon in the desulfurization plant. In addition, the hydrogen sulfide degrades the function of the activated carbon for siloxane removal of the adsorption column, which is considered to be caused by the introduction of unremoved siloxane waste into the engine, resulting in various types of engine failure. Therefore, hydrogen sulfide, siloxane, and water can be regarded as the main causes of the failure of the biogas engine. Among them, hydrogen sulfide reacts with other materials causing failure and can be regarded as a substance having a great influence on the pretreatment process. As a result, optimization of $H_2S$ removal method seems to be an essential measure for stable operation of the biogas engine.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.120-128
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• 2015

This study reports the combustion characteristics, such as burner temperature and the concentration of exhausted gas ($O_2$, $CO_x$, $NO_x$) due to the different types and pitches of the fuel supply feeder of the wood pellet boiler. The 1st grade wood pellets composed of mainly larch have been used for the experiment. In case of using the spring feeder, mean temperature of burner was approximately $821.76^{\circ}C$, and the mean concentration of oxygen, carbon monoxide, carbon dioxide and nitrogen oxide were approximately 8.88%, 93.35ppm, 12.15% and 139.83 ppm, respectively. The test result with the spring feeder was shown to approach the condition of complete combustion compared to that of a screw feeder and were in good agreement with authentication judgement standard. Furthermore, the combustion efficiency was improved according to the growth of screw pitch. The control of air flow rate from the blower and ventilator is needed to achieve the complete combustion.