• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.652-659
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• 2011

A computational system to predict flowfield and infrared signature in aircraft exhaust system is developed. As the first step, a virtual mission profile is considered and an engine is selected through a performance analysis. Then a nozzle that meets the requirement of each mission is designed. The internal flow in the exhaustion nozzle at the maximum thrust is analyzed using a state-of-the-art CFD code. In addition, a system to combine information of the skin temperature distribution of the nozzle and after-body surface with an infrared prediction code is developed. Finally, qualitative results for the infrared signature reduction design are obtained by investigating the infrared signature level under various conditions.

• Journal of Environmental Science International
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• v.19 no.2
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• pp.229-236
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• 2010

As air pollution has emerged as one of the most pressing urban environmental concerns, many studies have investigated the influence of air pollutants(ex: $O^3$, $NO^2$, $SO^2$, Acid rain, etc.) on roadside trees and urban grove. In Korea, population density started to increase since the industrialization. Since dense population aggravates our living conditions, it's very important for us to preserve and keep a lively and refreshing nature in order to live with green nature in harmony under the current artificial environment-dominating world. In metropolitan cities, the production of pollutants increases in proportion to population growth. The vehicle exhaust gas and air pollutants from cooling and heating systems have been the major causes of acid rain. Furthermore, tire particles which are naturally produced by tire wearing on roads and other toxic substances in exhaust gas have caused a problem in human health directly and indirectly. In fact, a lot of studies have analyzed air pollution, roadside trees and plants in Korea. However, they are mostly limited to covering the influence of air pollution on the growth of plants. No paper has clearly explained why air pollution-resistant or-vulnerable species has shown different reactions yet. Even though a lot of urban roadside trees have died or stopped to grow from time to time, this kind of problem has not been properly examined. This paper is aimed to comparatively analyze physio-ecological characteristic such as photosynthesis, chlorophyll contents, soil volume water figure out their relationship with environmental factors against the expanding roadside trees in Cheong-ju, and provide basic data for management of roadside trees and elaboration of urban environment preservation policies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.209-213
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• 2016

The characteristics of fluidization in a centrifugal fluidized bed with a 184 mm inner diameter, 50 mm width of the gas distributor was observed by photographs and experimental works using Cu-ZSM-5 zeolite catalysts with a mean diameter of $26{\mu}m$ and $32{\mu}m$ as bed materials at a rotor at 400rpm and 600rpm. Under these experimental ranges, the experimental results clearly showed the effects of the number of rotation of the rotor on the behavior of bubbles in the centrifugal fluidized bed. As the number of rotations of the rotor increased, the gas velocity at which bubbles begin to be formed also increased but the diameter of the bubbles decreased. In addition, the size of the bubbles in the centrifugal fluidized bed were relatively smaller than those in the conventional bubbling fluidized bed.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.68-78
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• 2006

In the past few years, considerable efforts have been directed towards the further development of Urea-SCR(selective catalytic reduction) technique for diesel-driven vehicle. Although urea possesses considerable advantages over Ammonia$(NH_3)$ in terms of toxicity and handling, its necessary decomposition into Ammonia and carbon dioxide complicates the DeNOx process. Moreover, a mobile SCR system has only a short distance between engine exhaust and the catalyst entrance. Hence, this leads to not enough residence times of urea, and therefore evaporation and thermolysis cannot be completed at the catalyst entrance. This may cause high secondary emissions of Ammonia and isocyanic acid from the reducing agent and also leads to the fact that a considerable section of the catalyst may be misused for the purely thermal steps of water evaporation and thermolysis of urea. Hence the key factor to implementation of SCR technology on automobile is fast thermolysis, good mixing of Ammonia and gas, and reducing Ammonia slip. In this context, this study performs three-dimensional numerical simulation of urea injection of heavy-duty diesel engine under various injection pressure, injector locations and number of injector hole. This study employs Eulerian-Lagrangian approach to consider break-up, evaporation and heat and mass-transfer between droplet and exhaust gas with considering thermolysis and the turbulence dispersion effect of droplet. The SCR-monolith brick has been treated as porous medium. The effect of location and number of hole of urea injector on the uniformity of Ammonia concentration distribution and the amount of water at the entrance of SCR-monolith has been examined in detail under various injection pressures. The present results show useful guidelines for the optimum design of urea injector for reducing Ammonia slip and improving DeNOx performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.4
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• pp.454-462
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• 2016

This study was conducted in order to estimate the exhaust emissions analysis method of the real driving emission(RDE). The Association for Emissions Control by Catalyst(AECC) has developed a test procedure by using a random cycle method based on the chassis dynamometer. In order to confirm this approach in Korea, Euro 5(DPF), Euro 6(DPF + LNT), and Euro 6(DPF + SCR) were performed on three different vehicles to determine the exhaust gas characteristics of the random cycle, real-road driving test(PEMS), and emission certification driving mode(NEDC). Six different random cycle driving modes were generated by the vehicle specifications(e.g. curb weight, engine power, gear ratio, and maximum acceleration). The NOx emissions were increased in the NEDC, random cycle, and PEMS order in this study regardless of the test vehicles. The random cycle method has the advantage because it utilizes a chassis dynamometer in the laboratories for a repeatable data collection, and it allows any eminent emission improvement checked prior to a real-road driving test with PEMS.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.166-174
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• 2015

This study examined combustion characteristics by selecting the fuel which have a different physical properties compared to gasoline in order to examine the effects of vehicle performance and environment depending on the physical properties. The experiment examined the combustion characteristic in the optimum ignition timing according to the physical properties change and the lean burn by performing control about ignition timing and air-fuel ratio for each fuel, and it was also evaluated the exhaust gas according to the experiment. We used a single-cylinder engine for the experiment, and tested for gasoline properties change by selecting a fake fuel that beyond the fuel quality standards in 석대법. As a result, in the case of the selected fuel showed a difference in Octane and distillation characteristics, vapor pressure and it was also found to unstable combustion, and leads to a large amount of harmful exhaust gas.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.33-33
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• 1999

The Coanda effect is the tendency for a fluid jet to atach itself to an adjacent surface and follow its contour without causing an appreciable flow separation. The jet is pulled onto the surface by the low pressure region which develops as entrainment pumps fluid from the region between the jet and the surface. Then the jet is held to the wall surface by the resulting radial pressure gradient which balance the inertial resistance of the jet to turning. The jet may attach to the surface and may be deflected through more than 180 dog, when the radius of the Coanda surface is sufficiently large compared to the height of the exhaust nozzle. However, if the radius of curvature is small, the jet turns through a smaller angle, or may not attach to the surface at all. In general, the limitations in size and weight of a device will limit the radius of the deflection surface. Thus much effort has been paid to improve the jet deflection in a variety of engineering fields. The Coanda effect has long been applied to improve aerodynamic characteristics, such as the drag/lift ratio of flight body, the engine exhaust plume thrust vectoring, and the aerofoil/wing circulation control. During the energy crisis of the seventies, the Coanda jet was applied to reduce vehicle drag and led to drag reductions of as much as about 30% for a trailer configuration. Recently a variety of industrial applications are exploiting another characteristics of the Coanda jets, mainly the enhanced turbulence levels and entrainment compared with conventional jet flows. Various industrial burners and combustors are based upon this principle. If the curvature of the Coanda surface is too great or the operating pressure too high, the jet flow will break away completely from the surface. This could have catastrophic consequences for a burner or combustor. Detailed understanding of the Coanda jet flow is essential to refine the design to maximize the enhanced entrainment in these applications.

• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.21-26
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• 2011

Emissoin of heavy duty vehicle have much positioned in air pollution although its limited number of vehicles. CNG vehicles are coming to the fore as one of the solution of diesel vehicles. CNG vehicles exhaust smaller emission than diesel vehicles on PM and NOx. In this study, aftertreatment technologies are introduced on vehicles which use CNG and hydrogenmixed fuel. Withmixing hydrogen with CNG, combustion efficiency is enhanced, and harmful emission might be decreased, but methane that is main component of CNG brings green house effect. In order to remove methane and NOx in exhaust gas of CNG engine, methane oxidation catalyst and SCR technologies were respectively analyzed.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.1
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• pp.8-18
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• 2024

The present study concerns reduced order modeling of a marine diesel engine, which can be used for outlier detection in status monitoring and carbon intensity index calculation. Principal Component Analysis (PCA) is introduced for the reduced order modeling, focusing on the feasibility of detecting and treating nonlinear variables. By cross-correlation, it is found that there are seven non-linear data channels among 23 data channels, i.e., fuel mode, exhaust gas temperature after the turbocharger, and cylinder coolant temperatures. The dataset is handled so that the mean is located at the nominal continuous rating. Polynomial presentation of the dataset is also applied to reflect the linearity between the engine speed and other channels. The first principal mode shows strong effects of linearity of the most data channels to show the linearity of the system. The non-linear variables are effectively explained by other modes. second mode concerns the temperature of the cylinder cooling water, which shows small correlation with other variables. The third and fourth modes correlates the fuel mode and turbocharger exhaust gas temperature, which have inferior linearity to other channels. PCA is proven to be applicable to data given in binary type of fuel mode selection, as well as numerical type data.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.4
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• pp.378-386
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• 2014

The use of bus stop in the center lane has reduced the emissions of exhaust gas on the road due to the improvement of the traffic speed but has caused a health problem for the citizens who are waiting for the bus in the platform, and thus the air pollution control of bus stop in the center lane is emerging as a more important part. This study was conducted to investigate the air pollution degree for the center lane-bus stops in four regions using mobile air measuring vehicle, and to evaluate the characteristics of air pollution by comparing with the data measured at the urban air monitoring site close to the bus stops. In addition, the correlation analysis was performed to analyze the impact to neighboring region by vehicle exhaust gas. The regional mean concentration of nitrogen dioxide in the center lane-bus stops ranged from 0.025 to 0.043 ppm which shows from 2.5 times to 5.3 times higher than the values of urban air monitoring site selected as a control group. The regional mean concentration of ozone in the center lane-bus stops ranged from 0.023 to 0.034 ppm which shows from 3% to 28% lower than the values of urban air monitoring site selected as a control group. The concentrations of nitrogen dioxide and ozone for the sampling regions did not exceed one hour-air quality environmental standard (0.1 ppm). The mean concentration of particulate matter for four center lane-bus stops was $28{\mu}g/m^3$ which shows about 27% higher than the values of urban air monitoring site selected as a control group, and that of particulate matter did not exceed one day-air quality environmental standard ($100{\mu}g/m^3$). In the results of correlation analysis between data from center lane-bus stops and data from urban air monitoring sites, the correlation coefficient (r) of nitrogen dioxide was relatively low as 0.316 to 0.416, and the correlation coefficient was high as the distance was close and vice versa. However, the correlation coefficient of ozone ranged from 0.167 to 0.658 and the correlation coefficient was high as the distance was far and vice versa.