• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.333-338
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• 2012

To verify the utilization of fluff refuse derived fuel (RDF) as energy source, the combustion charateristic has been studied by an experimental combustion furnace under various temperatures. The characteristics of flue gas, dust and residue from fluff RDF combustion has been analyzed and compared with those of pelletized RDF. From this work, it was found that the incomplete combustion of fluff RDF was greater than that of pelletized RDF because the combustion reaction rate of fluff RDF was faster than that of pelletized RDF, and oxgen concentration in fluff RDF combustion decreased rapidly. It was also found that carbon monoxide concentration of flue gas from fluff RDF combustion increased with combustion temperature because the oxygen consumption and the incomplete combustion increased. Therefore, it is felt that the combustion operation conditions of fluff RDF should be carefully determined.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.74-80
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• 2008

A combustion of CAI engine is purely dominated by fuel chemical reactions. In order to simulate the combustion of CAI engine, it should be considered the effect of fuel components and chemical kinetics. So it needs enormous computational power. To overcome this problem reduced problem of needing massive computational power, chemical kinetic mechanism and multi-zone method is proposed here in this paper. A reduced chemical kinetic mechanism for a gasoline surrogate was used in this study for a CAI combustion. This gasoline surrogate was modeled as a blend of iso-octane, n-heptane, and toluene. For the analysis of CAI combustion, a multi-zone method as combustion model for a CAI engine was developed and incorporated into the computational fluid dynamics code, STAR-CD, for computing efficiency. This coupled multi-zone model can calculate 3 dimensional computational fluid dynamics and multi-zoned chemical reaction simultaneously in one time step. In other words, every computational cell interacts with the adjacent cells during the chemical reaction process. It can enhance the reality of multi-zone model. A greatly time-saving and yet still relatively accurate CAI combustion simulation model based on the above mentioned two efficient methodologies, is thus proposed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.905-910
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• 2003

One of the methods that are used to compare and verify the supporting performance of the spacer grids developed is the vibration characteristic test. A modal test in this paper is performed for a dummy rod 3,847mm tall supported by eight New Doublet (ND) spacer grids. For the vibration test in air, nine accelerometers, one displacement sensor and one shaker are used for acquiring signals, and an I-DEAS TDAS software is employed for analyzing the signals. Also, a finite element (FE) analysis is performed by a beam-spring simple model and a contact model simulating the contact phenomenon between the rod and the fm spring. And then, the result of the FE analysis is compared with that of the modal test. The natural frequencies as well as the mode shapes calculated by the proposed contact models have a greater similarity to the test results than those by the previous beam-spring model. In addition, for grasping whether or not the modal parameters are influenced by where shaking spot is, two kinds of tests are performed; one is for the shaker attached at the fourth span (center), the other is for the shaker at the fifth span that is one span nearer to the bottom of the rod. The latter shows higher MAC than the former. Finally, the vibration displacements are measured in the range of 0.112-0.214mm for the excitation force of 0.25-0.75 N.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.27-33
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• 2013

In this study we analyzed the on-road driving performance of two parallel-type diesel-hybrid buses which have been driven in Daegu metropolitan area. A real-time on-board data logger was facilitated to measure the vehicle information such as vehicle speed, idle stop, state of charge of battery, and engine operating conditions. These diesel-hybrid buses ran as a commuter at Daegu Exco area and Dalsung industrial complex. The driving pattern in Exco area comprised more frequent idle stop and relatively lower speed than at Dalsung area, where comprised no idle stop. Due to those different driving patterns, the fuel economy at Dalsung showed $3.7\;km/{\ell}$, which is about 8% higher than that of Exco. The main causes of this come from the higher portion of regenerative braking and higher speed which moves to the operating points of diesel engine with a lower fuel consumption.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.299-303
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• 2015

The electrolyte is an important component in determining the performance of Fuel Cells. Especially, investigation of the conduction properties of electrolytes plays a key role in determining the performance of the electrolyte. The electrochemical properties of Yttrium stabilized zirconia (YSZ) were measured to allow the use of this material as an electrolyte for solid oxide fuel cells (SOFC) in the temperature range of $700-1000^{\circ}C$ and in $0.21{\leq}pO_2/atm{\leq}10^{-23}$. A Hebb-Wagner polarization experimental cell was optimally manufactured; here we discuss typical problems associated with making cells. The partial conductivities due to electrons and holes for 8YSZ, which is known as a superior oxygen conductor, were obtained using I-V characteristics based on the Hebb-Wagner polarization method. Activation energies for holes and electrons are $3.99{\pm}0.17eV$ and $1.70{\pm}0.06eV$ respectively. Further, we calculated the oxygen ion conductivity with electron, hole, and total conductivity, which was obtained by DC four probe conductivity measurements. The oxygen ion conductivity was dependent on the temperature; the activation energy was $0.80{\pm}0.10eV$. The electrolyte domain was determined from the top limit, bottom limit, and boundary (p=n) of the oxygen partial pressure. As a result, the electrolyte domain was widely presented in an extensive range of oxygen partial pressures and temperatures.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.19-26
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• 2000

This paper presents the effects of initial pressure of mixture on CO, $CO_2$ and NOx emissions in constant volume combustion chamber. The CO, $CO_2,O_2,N_2$ concentrations in the chamber are determined by thermal conductivity detection (Gas-chromatograph) wile the NOx concentration is measured by chemiluminescent detection (NOx Analyser). Methane-air mixture is used as premixed fuel and the measurements are taken with equivalence ratios($\phi$) varing from 0.6 to 1.3, and initial pressures of methane-air mixture varing from 0.1MPa to 0.8MPa in constant volume combustion chamber. The NOx concentration steadily increases with increasing equivalence ratio, peaks in lean flame ($\phi$=0.85~0.9), and then rapidly decreases. However, as the initial pressure of mixture is increased, the equivalence ratio corresponding to the point of peak [NOx] shifts towards leaner conditions. This is caused by a similar shift in the peak [CH], which is caused by the variation with pressure and equivalence ratio of the rate of CH production from $CH_2$ and OH. The maximum combustion pressure peaks at $\phi$ =1.05 and the $CO_2$ concentration peaks at $\phi$=0.95~1.0 while the CO concentration rises sharply at the condition of fuel-rich mixtures. This is caused by complete combustion at $\phi$=0.95.

• Journal of Biosystems Engineering
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• v.27 no.1
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• pp.25-32
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• 2002

This study was conducted to develop a dry paddy seeder of strip tillage. The prototype is 8 rows drill seeder, which is composed of a strip tillage, sowing and fertilizing device, and pressing wheels to do the strip tillage, sowing, fertilizing, and draining ditch, simultaneously. The performances of prototype was evaluated through the investigation of fuel consumption, tillage torque, ratio of soil breaking, and economical efficiency and the results were compared with these of a dry paddy seeder that needs whole tillage. According to the USDA textural classification, the experiment field was composed of sandy loam which consisted of 56.8 of sand, 30.2 of silt and 13.0 % of clay, respectively. Its hardness ranged from 952 to 1,673 kPa depending on the soil depth, and its soil moisture content was 24.9%(d. b.) Fuel consumption of the prototype was 5,015g/hr at 2,000 rpm of engine, which was consequently 64% smaller than that of the conventional dry paddy seeder. For the tillage torque, it ranged from 132 to 206N$.$m depending on the tillage pitch, which was 10∼30% smaller than that of the conventional dry paddy seeder. The ratio of soil braking of the prototype was 87∼98%, whereas that of the conventional dry paddy seeder was 80∼97%. The working performance of the prototype was surveyed to be 3.8hours/ha, which was about 5 times higher than that of the conventional dry paddy seeder. The cost reduction of 26.3% was obtained by using the prototype.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.125-130
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• 2012

In these days, there has been increased focus on global warming and the exhaustion of resources recently caused by the heavy consumption of fossil resources. In order to resolve these problems, biomass is increasingly gaining international attention as a renewable energy source. Biogas derived from various biomass is environmental friendly alternative fuel for power generation, heating and vehicle fuel. Large amounts of sewage sludge, food waste and manure are generated from human activity, but these organic wastes contain high levels of organic matter and thus they are potential substrates for producing methane of biogas. The biogas contains 60% of highly concentrated methane, which is expected to be used effectively as energy. In this paper, we investigate the status of biogas in Korea as an alternative energy.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.153-156
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• 2012

In this study, two different methods were studied to prepare Pt-Pd catalysts for direct methanol fuel cells in order to enhance the electrochemical efficiency. The catalysts were compared with simultaneously deposited Pt-Pd and sequentially deposited Pt-Pd. The electrocatalysts contained 20 wt% of metal loading on carbon black and 1 : 2 of Pt : Pd atomic ratio. Electrochemical properties of the catalysts were compared by measuring cyclic voltammetries and average sizes and lattice parameters were measured by transmission electron microscopy images and x-ray diffraction. As a result, sequentially deposited Pt-Pd/C catalysts showed better electrochemical properties than those of simultaneously deposited Pt-Pd/C catalysts.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.109-114
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• 2008

This paper presents the development status of a subscale precooled turbojet engine "S-engine" for the hypersonic cruiser and space place. S-engine employs the precooled-cycle using liquid hydrogen as fuel and coolant. It has $23cm{\times}23cm$ of rectangular cross section, 2.6 m of the overall length and about 100 kg of the target weight employing composite materials for a variable-geometry rectangular air-intake and nozzle. The design thrust and specific impulse at sea-level-static(SLS) are 1.2 kN and 2,000 sec respectively. After the system design and component tests, a prototype engine made of metal was manufactured and provided for the system firing test using gaseous hydrogen in March 2007. The core engine performance could be verified in this test. The second firing test using liquid hydrogen was conducted in October 2007. The engine, fuel supplying system and control system for the next flight test were used in this test. We verified the engine start-up sequence, compressor-turbine matching and performance of system and components. A flight test of S-engine is to be conducted by the Balloon-based Operation Vehicle(BOV) at Taiki town in Hokkaido in October 2008. The vehicle is about 5 m in length, 0.55 m in diameter and 500 kg in weight. The vehicle is dropped from an altitude of 40 km by a high-altitude observation balloon. After 40 second free-fall, the vehicle pulls up and S-engine operates for 60 seconds up to Mach 2. High altitude tests of the engine components corresponding to the BOV flight condition are also conducted.