• International Journal of Automotive Technology
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• v.7 no.1
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• pp.17-23
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• 2006

An experimental study was carried out to obtain the fundamental data about the effect of sub-chamber on pre-mixture combustion. A eve (constant volume combustor) divided into a sub-chamber and a main chamber was used in this experiment. The volume of the sub-chamber was varid trom $0.45\%$ to $1.4\%$ about the whole combustion chamber. The sub-chamber has twelve narrow radial passage holes and a spark plug to ignite the pre-mixture. As the ignition occurs in the sub-chamber by a spark discharge, burned and unburned gas including a great number of radicals is injected into the main chamber, then the multi-point ignition occurs in the main chamber. The combustion pressure is measured to calculate the burning velocity mainly as a function of the sub-chamber volume, the diameter of the passage holes, and the equivalence ratio. In the case of RI (radical ignition) methods, the overall burning time became very short and the maximum burning pressure was slightly increased as compared with that of SI (spark ignition) method. The optimum design value of the sub-chamber is near 0.11 $cm^{-l}$ in the ratio of total area of holes to the sub-chamber volume.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.133-139
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• 2005

In this study, a three-dimensional transient simulation with a knock model was performed to predict knock occurrence and autoignition site in a heavy-duty LPG engine. A FAE (Flame Area Evolutoin) premixed combustion model was applied to simulate flame propagation. The coefficient of the reduced kinetic model was adjusted to LPG fuel and used to simulate autoignition in the unburned gas region. Engine experiments using a single-cylinder research engine were performed to calibrate the reduced kinetic model and to verify the results of the modeling. A pressure transducer and a head-gasket type ion-probe circuit board were installed in order to detect knock occurrences, flame arrival angles, and autoignition sites. Knock occurrence and position were compared for different piston bowl shapes. The simulation concurred with engine experimental data regarding the cylinder pressure, flame arrival angle, knock occurrence, and autoignition site. Furthermore, it provided much information about in-cylinder phenomena and solutions that might help reducing the knocking tendency. The knock simulation model presented in this paper can be used for a development tool of engine design.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.180-188
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• 2020

To replace Japanese coal ash used in the domestic cement production and to recycle large quantities of domestic pond ash, it is essential to develop the technologies for quality control of cement by using the domestic pond ash. Thus, in this study, the feasibility of using the pond ash as a raw material for cement was investigated through chemical composition and microstructure analysis. As a result, most of the domestic pond ash contained slightly more Fe2O3, chloride, and unburned carbon contents than Japanese coal ash. In particular, the contents of chloride were considerably low in the pond ash that was transferred to fresh water or collected from surface of landfill area. However, since circulating fluidized bed boiler coal ash had relatively high SO3 contents causing durability problems of cement, it was not suitable for use as a raw material for cement. Thus, to replace Japanese coal ash with the domestic pond ash, it is necessary to introduce the adjustment of mixture proportion of cement raw materials and the process of removing chloride in the pond ash.

• Korean journal of applied entomology
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• v.50 no.1
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• pp.7-14
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• 2011

We investigated moth communities in Samcheok, Korea, to elucidate the influence of the East Coast Fire in 2000. Moths were collected with UV light traps 4 times a year from 2006 to 2009 at 3 sites: Unburned area (Site 1), Surface fire area (Site 2), and Crown fire area (Site 3) sites, respectively. A total of 3,804 individuals belonging to 727 species from 30 families were captured at the 3 study 1,727 individuals of 505 species (27 families) at Site 1, 1,193 individuals of 353 species (24 families) at Site 2, and 885 individuals of 340 species (25 families) at Site 3. Species richness and individuals of Noctuidae, Pyralidae, Geometridae, and Tortricidae were the highest at all 3 sites. All of species richness, individuals, and species diversity (H') were the highest in Site 1 for 4 years. The index of similarity (${\alpha}$-Index) was higher between Site 2 and 3 in 2006, while higher between Site 1 and 2 in 2009. Moths were grouped into 16 categories by hosts of the larval stage. Individuals of moths of herbaceous feeding habit continuously decreased at Site 3, but proportion of individuals of tree feeding habits continuously increased. The present results showed that moth communities was relatively recovered according to vegetation change after forest fire and regeneration of moth communities in surface fire area was more faster than in crown fire area.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.8
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• pp.743-752
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• 2013

This is the second paper on the combustion characteristics of landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine, and it discusses the combustion process on the basis of pressure measurements. The results show that the bimodal peak pressure phenomenon, which is caused by the interaction of the heat release and the heat transfer, is more apparent as the mixtures are more favorable to combustion, and the magnitudes of the pressures depend on the unburned fraction. In addition, there exist four main inflection points during heat release owing to variations in the heat transfer area related to flame propagation from the ignition point. Furthermore, the number of inflection points increases as the mixture quality worsens because of the extended burn duration. Consequently, the sophisticated interactions between the heat transfer area changing pattern due to flame propagation and transfer duration might cause very peculiar heat release patterns.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.139-154
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• 1998

Under certain circumstance, premixed turbulent flame can be treated as wrinkled thin laminar flame and its motion in a hydrodynamic flow field has been investigated by employing G-equation. Past studies on G-equation successfully described certain aspects of laminar flame propagation such as effects of stretch on flame speed. In those studies, flames were regarded as a passive interface that does not influence the flow field. The experimental evidences, however, indicate that flow field can be significantly modified by the propagation of flames through the volume expansion of burned gas. In the present study, a new method to be used with G -equation is described to include the effect of volume expansion in the flame dynamics. The effect of volume expansion on the flow field is approximated by Biot-Savart law. The newly developed model is validated by comparison with existing analytical solutions of G -equation to predict flames propagating in hydrodynamic flow field without volume expansion. To further investigate the influence of volume expansion, present method was applied to initially wrinkled or planar flame propagating in an imposed velocity field and the average flame speed was evaluated from the ratio of flame surface area and projected area of unburned stream channel. It was observed that the initial wrinkling of flame cannot sustain itself without velocity disturbance and wrinkled structure decays into planar flame as the flame propagates. The rate of decay of the structure increased with volume expansion. The asymptotic change in the average burning speed occurs only with disturbed velocity field. Because volume expansion acts directly on the velocity field, the average burning speed is affected at all time when its effect is included. With relatively small temperature ratio of 3, the average flame speed increased 10%. The combined effect of volume expansion and flame stretch is also considered and the result implied that the effect of stretch is independent of volume release.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.12
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• pp.1108-1114
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• 2007

The effect of oxidizer injection angle on the combustion characteristics of end-burning hybrid combustor is numerically investigated. Besides the previously studied parameter(injector arrangement, port diameter and O/F ratio), three different injection angle are considered: parallel angle to fuel surface(Case 1), +30 degree inclined angle toward the fuel(Case 2) and 30 degree inclined angle toward the nozzle(Case 3). It is found that Case 2 has the best mixing pattern in the upstream area but has the worst combustion efficiency since non negligible amount of unburned fuel is expelled from the nozzle. In contrast, though Case 1 and Case 3 showed relatively low mixing effect than the Case 2, they had high combustion efficiency. The comparison of numerical results between Case 1 and Case 3 demonstrate that no major difference is encountered, however, Case 1 is expected to have the best combustion efficiency due to the low residence time of the Case 3 injector which heads toward the nozzle.

• Korean journal of applied entomology
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• v.50 no.4
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• pp.267-278
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• 2011

This study was conducted to estimate the effects of fire intensity and recovery methods on coleopteran communities in three burned forests, Goseong, Gangneung, and Samcheok in Gangwon province, Korea. Four sampling sites were selected in each study area according to disturbance degree (DD) caused by fire intensity and recovery methods. DD in the study sites were categorized as 0 (no fire), 1 (weak fire), 2 (strong fire), and 3 (strong fire followed by human disturbance). Beetles collected by pitfall traps were classified into 3 functional guilds: detritivore, herbivore, and carnivore. Diversity and abundance were slightly higher in the burned sites (DD = 1-3) than in the unburned sites (DD = 0), although there was no statistical significance. Coleopteran communities differed according to fire intensity and recovery method. This suggests that recovery of burned forests using both natural recovery and reforestation may increase the diversity of coleopteran communities.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.979-985
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• 2011

This paper includes that there are results of designing the flash hider and analyzing fluid dynamics of a front area of the barrel to shorten the length of small arms. Generally, the muzzle flash can be generated out of the barrel by the reaction between the oxygen in the air and unburned gunpowder contained in the propellant gas if a barrel is not long enough to burn gunpowder fully inside of the barrel. Though, the hugh muzzle flash, which is a characteristic of small arms with short barrel length, caused a soldier to aim at the target at night by making the soldier blind for a while and endangers his life by revealing firing position to enemies. Besides, the heat of muzzle flash can weaken the performance of thermal sights, which are attached to small arms for night battlefield. In this paper, flash hiders with several different shapes were designed for a newly developed 5.56mm caliber rifle with short barrel length. The performance of each flash hider to reduce the muzzle flash was compared theoretically and experimentally. Through the authorized test procedure, a highly efficient design of flash hider for reducing the muzzle flash was identified. The result of the paper can be helpful when designing flash hiders for small arms with short barrel length.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.17 no.2
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• pp.49-60
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• 2014

This study was conducted to evaluate the effect of forest fire on natural distribution and regeneration of Pinus densiflora Sieb. & Zucc. in Goseong, Gangwon province, Korea. After 13 years of the last forest fire in 2000, five investigation plots ($10m{\times}10m$) in each of rocky land and ridge, the well-known location as a favorite site for natural distribution of P. densiflora, were set to investigate stand characteristic and soil environment including physico-chemical properties and moisture contents of soil. Also, five investigation plots in slope area were set and investigated as well. The concentration of organic matter, total nitrogen, and exchangeable nutrients ($K^+$, $Ca^{2+}$, $Mg^{2+}$) were highest in the slope while the soil in the rocky land showed the lowest concentration of organic matter, total nitrogen, available $P_2O_5$, and exchangeable nutrients ($K^+$, $Na^+$, $Ca^{2+}$, $Mg^{2+}$). The soil in the slope only showed higher concentration of total nitrogen, $K^+$ and $Ca^{2+}$ than the unburned area in Goseong. Mean soil moisture contents in the rocky land (5.77%) were lowest while the slope (15.78%) and the ridge (15.27%) showed almost three times as much than the rocky land. P. densiflora was dominant in the rocky land and Quercus spp. were dominant in the ridge and slope. The average proportion of P. densiflora was highest in rocky land (58.4%, 14.6 trees per plot) followed by the ridge (25.2%, 7.8 trees per plot) and the slope (11.3%, 3.4 trees per plot) while the average height of P. densiflora was highest in slope (277cm) followed by the ridge and the rocky land. The height and crown width of Quercus spp. were higher than P. densiflora in the every plot. The results suggest that P. densiflora may be able to naturally regenerate and survive in the rocky land after the fire while P. densiflora in the ridge and the slope are suppressed by Quercus spp.