• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.1
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• pp.65-73
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• 2006

The high temperature occurs due to the combustion gas from engine in unmanned aerial vehicles (UAV). The high temperature may cause serious damages in UAV structure. The Functionally Graded Material (FGM) is chosen as a candidate material of the engine duct structure. A functionally graded material (FGM) is a two- component mixture composed by compositional gradient materials from one material to the other. In contrast, traditional composite materials are homogeneous mixtures, and involve compositions between the desirable properties of the component materials. Since significant proportions of an FGM contain the pure form of each material, the need for compromise is eliminated. The properties of both components can be fully utilized. Thermal stress analysis of FGM layers (20, 40, 60, 80 and 100) is performed in this paper. In addition, the creep behavior of FGM applied in duct structure of an engine is analyzed for better understanding of FGM characteristics.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.6
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• pp.767-778
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• 2006

This study was carried out to evaluate the temporal variations of VOCs at an urban site, and to compare the concentrations of VOCs at an urban site in Daegu with those at a suburban site in Gyeongsan. Three hourly VOC samples in the ambient air were collected using a sequential tube sampler (STS 25, Perkin Elmer) throughout two weeks during May and July representing spring and summer seasons, respectively. The VOC concentrations were determined by an automatic thermal desorption apparatus with GC/MS analysis. A total of 12 VOCs of environmental concern were determined, which are chloroform, benzene, trichloroethylene, toluene, tetra-chloroethylene, ethylbenzene, m+p-xylenes, o-xylene, styrene, 1,3,5- and 1,2,4-trimethylbenzenes. Among 12 target VOCs, the most abundant compound appeared to be toluene, being followed by xylenes. The mean concentrations at the urbn site were 1.2 pub for benzene and 20.4 ppb for toluene (n=221) while the mean levels at the suburban site were 0.9 ppb and 4.3 ppb for benzene and toluene (n=96), respectively. The urban site concentrations were typically several-fold higher than those measured at the suburban site. It was found that general trends of VOC levels were significantly dependent on traffic conditions at the sampling site since VOC concentrations were at their maximum during rush hours, i.e. $9{\sim}12a.m$ and $6{\sim}9p.m$. Statistical investigations were conducted to investigate any significant relationships between VOC concentrations and affecting factors. Calculated correlation coefficients among VOCs were positively significant at a level of 0.05 in most cases. Increased concentrations of toluene in the urban site were estimated to reflect the effect of large industrial sources, mainly from textile industry.

• Journal of ILASS-Korea
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• v.25 no.1
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• pp.27-33
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• 2020

NOx, PN and CO emissions from diesel trucks make up a significant portion of domestic air pollutant emissions. Therefore, test vehicles with various emission standards and driving modes were selected to evaluate the emission characteristics of regulated pollutants (NOx, PN, CO) in medium-duty trucks. As a result of test, all test vehicles were satisfied with Euro 5 or 6 regulation. NOx emissions of Euro 6 vehicles with after-treatment of LNT + DPF were lower than those of Euro 5 vehicles with DPF. In WLTC mode, all vehicles have high NOx emissions at section of extra high speeds, which are determined by increased fuel consumption and high combustion temperatures. CO and PN emissions from all vehicles were found to be low at section of low speeds. Also, The NO₂/NOx ratio was analyzed at 7-23% in each mode, and the NO₂/NOx ratio increased as the average vehicle speed increased. In NIER 9 mode, the CO, HC, and PN emissions were higher under cold conditions of engine than hot conditions of engine. In addition, vehicles with after-treatment system of LNT have similar NOx emissions level in this study.

• Journal of the Korean Institute of Gas
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• v.21 no.6
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• pp.1-7
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• 2017

This study is aimed to investigate the US code and European code on the evaluation of fuel economy of natural gas vehicles and deduce the formula suitable for domestic natural gas fuel. The fuel consumption formula have been derived by carbon balance relation between fuel composition and exhaust emission. The US code does not limit the composition of the test gas, but European code should be used the reference gases such as G20 and G23. In the case of NGV using domestic city gas, it is confirmed that the fuel economy determined by European code is 12% worse than that of US code because of difference of test gas. Also, a method of determining the fuel properties from the calorific value is proposed to evaluate the fuel economy of natural gas vehicles.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.80-83
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• 2008

As SOC (Social Overhead Capital) has been expanded, the highway road construction has been accelerated and city road system has been more complicated. So, long road tunnels have been increased and traffic flow rate also has been raised. Accordingly, the exhausting gas of vehicle cars seriously deteriorates the tunnel inside air quality and driving view. In order to improve tunnel inside air quality, we may need to introduce a compulsory ventilation system as well as natural ventilation mechanism. The natural ventilation mechanism is enough for short tunnels, meanwhile longer tunnels require a specific compulsory ventilation facility. Many foreign countries already have been devoting on development of effective tunnel ventilation system and especially, some European nations and Japan have already applied their developed tunnel ventilation system for longer road tunnels. More recently, as the quality of life improved, our concerns about safety of driving and better driving environment have been increased. In order to obtain clearer and longer driving view, we are more interested in EP tunnel ventilation system in order to remove floating contaminants and automobile exhaust gas. Evan though it's been a long time since many European countries and Japan applied more economical and environment-friendly tunnel ventilation system with their self-developed Electrostatic Precipitator, we are still dependant on imported system from foreign nations. Therefore, we need to develop our unique technical know-how for optimum design tools through validity investigation and continuous possibility examination, eventually in order to localize the tunnel ventilation system technology. In this project, we will manufacture test-run products to examine the performance of system in order to develop main parts of tunnel ventilation system such as electrostatic precipitator, high voltage power generator, water treatment system, etc.

• Design & Manufacturing
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• v.11 no.2
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• pp.37-41
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• 2017

With light vehicle weight gradually becoming ever more importance due to tightened exhaust gas regulations, hot-stamping processing using boron alloyed steel is being applied more and more by major automobile OEMs since process assures both moldability and a high strength of 1.5 GPa. Although laser trimming is generally applied to the post-processing of the hot-stamped process with high strength, there have been many studies of in-die hot trimming using shear dies during the quenching of material in order to shorten processing times. As such, this study investigated the effects of the Shear rate and Shear mechanism on shear processes during the quenching process of hot-stamping material. In case of pad variable, padding force is very weak compared with shear force, so it does not affect the shear surface. In case of shear rate, the higher the shear at high temperatures and the higher the friction effect. As a result the rollover and the fracture distribution decreased, and the burnish distribution increased. Therefore, it is considered that the shear quality is guaranteed when high shear rate is applied in high temperature shear process.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.32-38
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• 2006

Currently, due to the serious world-wide air pollution by substances emitted from vehicles, emission control is enforced more firmly and it is expected that the regulation requirements for emission will become more severe. A new concept combustion technology that can reduce the NOx and PM in relation to combustion is urgently required. Due to such social requirement, technologically advanced countries are making efforts to develop an environment-friendly vehicle engine at the nation-wide level in order to respond to the reinforced emission control. As a core combustion technology among new combustion technologies for the next generation engine, the homogenous charge compression ignition(HCCI) is expanding its application range by adopting multiple combustion mode, catalyst, direct fuel injection and partially premixed combustion. This study used a 2-staged injection method in order to apply the HCCI combustion method without significantly altering engine specifications in the aspect of multiple combustion mode and practicality by referring to the results of studies on the HCCI engine. In addition, this study confirmed the possibility of securing optimum fuel economy emission reduction in the IMEP 8bar range(which could not be achieved with existing partially premixed combustion) through forced charging, exhaust gas recirculation(EGR), compression ratio change and application of DOC catalyst.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.162-170
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• 2007

Currently, due to the serious world-wide air pollution by substances emitted from vehicles, emission control is enforced more firmly and it is expected that the regulation requirements for emission will become more severe. Anew concept combustion technology that can reduce the NOx and PM in relation to combustion is urgently required. Due to such social requirement, technologically advanced countries are making efforts to develop an environment-friendly vehicle engine at the nation-wide level in order to respond to the reinforced emission control. As a core combustion technology among new combustion technologies for the next generation engine, the homogeneous charge compression ignition (HCCI) is expanding its application range by adopting multiple combustion mode, catalyst, direct fuel injection and partially premixed combustion. This study used a 2-staged injection method in order to apply the HCCI combustion method without significantly altering engine specifications in the aspect of multiple combustion mode and practicality by referring to the results of studies on the HCCI engine. And it is investigated that the effects of the engine rpm and load(or A/F) to emission characteristics.

• Journal of the Korean Institute of Gas
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• v.25 no.5
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• pp.52-56
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• 2021

With the development of an eco-friendly environment and the automobile industry, research is being actively conducted to increase thermal efficiency and reduce exhaust gas through complete combustion in internal combustion engine vehicles. In particular, research is underway to increase engine load and output by understanding the volatility and combustion characteristics of gasoline, and research is underway to reduce soot and harmful gases and realize optimal efficiency based on the distillation and combustion characteristics of diesel fuel. . Therefore, in this study, based on the contents of KS M ISO 3045 on the distillation test method for petroleum products according to the Korean industrial standard, distillation experiments were conducted based on gasoline and diesel from 4 refineries marketed and used in Korea. The distillation experiment confirmed the correlation with the distillation temperature according to the amount of distillation, and the distillation characteristics were analyzed by comparing the distilled fuel to confirm the suitability of meeting the test standards.

• Clean Technology
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• v.24 no.4
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• pp.301-306
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• 2018

Recently, due to the increase in the fine dust, regulations on PM generated from diesel cars are strengthened. There is a growing interest in diesel particulate filters (DPFs), a post-treatment device that removes exhaust gases from diesel vehicles. Therefore, one of the enhancements of the DPF efficiency is to reduce the pressure drop in the DPF, thereby increasing the efficiency of the filter and regeneration. In this study, the effect of cell density, channel shape, wall thickness, and inlet channel ratio of 5.66" SiC and Cordierite DPF on the pressure drop in DPF was investigated using ANSYS FLUENT simulator. As a result of the experiment, the pressure drop was smaller at 300 CPSI than 200 CPSI, and the anisotropy and O / S cell showed less than Isotropy by pressure drop of about 1,000 Pa. As the porosity increased by 10% the pressure drop was reduced by about 300 Pa and as the wall thickness increased by 0.05 mm, the pressure drop was increased by about 500 Pa.