• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.1
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• pp.67-73
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• 2011

The purpose of this study is to investigate experimentally the spray-atomization and combustion-emission characteristics of biodiesel-DME blended fuel. In this study, two types of test fuels pure biodiesel (BD100) and blended fuel (B-DME20) were used, and the spray and combustion characteristics of different fuel compositions were analyzed. DME constitutes 20% and biodiesel constitutes 80% (by mass fraction) of the blended fuel. The overall spray characteristics, spray tip penetration, and cone angle were evaluated using frozen spray images. In addition, the combustion and emission characteristics were analyzed on the basis of the evaluated data for a single-cylinder CI engine with common-rail injection system. It was revealed that the injection profiles of both the test fuels for a given injection pressure showed similar trends. However, the injection profiles of the blended fuel (B-DME20) indicated shorter ignition delay than those of biodiesel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.405-413
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• 2013

The char oxidation characteristics of high ash coal were experimentally investigated at several temperatures (from 900 to $1300^{\circ}C$) for 4 types of coals (Gunvor, Glencore, Noble, and ECM) under atmospheric pressure in a drop tube furnace (DTF). The char reaction rate was calculated from the exhaust gas concentrations (CO and $CO_2$) using FT-IR, and the particle temperature was measured using the two-color method. In addition, the activation energy and pre-exponential factor for high ash coal char were calculated based on the Arrhenius equation. The results show that as the ash content increases, the particle temperature and area reactivity decreases. This is because in high ash coal, the large heat capacity of the ash, ash vaporization, and relatively low fixed carbon content of ash suppress combustibility during char oxidation. As a result, the higher ash content of coal leads to high activation energy.

• Journal of Energy Engineering
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• v.11 no.2
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• pp.90-98
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• 2002

The effects of swirl and combustion parameters on the performance and emission in a turbo-charged D.I. diesel engine of the displacement 9.4L were studied experimentally in this paper. Generally the swirl in the combustion process of diesel engine promotes mixing of the injection fuel and the intake air. It is a major factor to improve the engine performance because the fuel consumption and NO$_{x}$ is trade-off according to the high temperature and high pressure of combustion gas in a turbocharged D.I. diesel engine, it's necessary to thinking over the intake and exhaust system, the design of combustion bowl and so on. In order to choose a turbocharger of appropriate capacity. As a result of steady flow test, when the swirl ratio is increased, the mean flow coefficient is decreased, whereas the gulf factor is increased. Also, through engine test its can be expected to meet performance and emissions by optimizing the main parameter's; the swirl ratio is 2.43, injection timing is BTDC 13$^{\circ}$ CA, compression ratio is 16, combustion bowl is re-entrant 5$^{\circ}$, nozzle hole diameter is $\Phi$0.28*6, turbocharger is GT40 model which are compressor A/R 0.58 and turbine A/R 1.19.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.130-136
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• 2011

This study describes the effect of EGR rate on the combustion and emissions characteristics of a four cylinder CRDI diesel engine using biodiesel (soybean oil) blended diesel fuel. The test fuel is composed of 30% biodiesel and 70% ULSD (ultra low sulfur diesel) by volumetric ratio. The experiment of engine emissions and performance characteristics were performed under the various EGR rates. The experimental results showed that ignition delay was extended, the maximum combustion pressure and heat release gradually were decreased with increasing EGR rate. Comparing biodiesel blended fuel to ULSD, the injection quantity of biodiesel blended fuel was further increased than ULSD. The emission results showed that $NO_x$ emission of biodiesel blended fuel becomes higher according to the increase of EGR rate. However, in the case of biodiesel blended fuel, HC, CO and soot emissions were decreased compared to ULSD.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.118-128
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• 2004

Exhaust plume effects on longitudinal aerodynamics of missile were investigated by wind tunnel tests using a solid plume simulator and CFD analyses with both the solid plume and air jet plumes. Approximate plume boundary prediction technique was used to produce the outer shape of the solid plumer and chamber conditions and nozzle shapes of the air jet plumes were determined through plume modeling technique to compensate the difference in thermodynamic properties between air and real plume. From comparisons among turbulence models in case of external flow interaction with the air jet plume, Spalart-Allmaras model turned out to give accurate result and to be less grid-dependent. Effects induced by the plume were evaluated through the computations with Spalart-Allmaras turbulence model and the air jet plume to account for various ratios of chamber and ambient pressure and Reynolds number under the flight test condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.178-185
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• 2006

This paper investigates the steady-state combustion characteristics of the Homogeneous charge compression ignition(HCCI) engine with variable valve timing(VVT) and dimethyl ether(DME) direct injection, to find out its benefits in exhaust gas emissions. HCCI combustion is an attractive way to lower carbon dioxide($CO_2$), nitrogen oxides(NOx) emission and to allow higher fuel conversion efficiency. However, HCCI engine has inherent problem of narrow operating range at high load due to high in-cylinder peak pressure and consequent noise. To overcome this problem, the control of combustion start and heat release rate is required. It is difficult to control the start of combustion because HCCI combustion phase is closely linked to chemical reaction during a compression stroke. The combination of VVT and DME direct injection was chosen as the most promising strategy to control the HCCI combustion phase in this study. Regular gasoline was injected at intake port as main fuel, while small amount of DME was also injected directly into the cylinder as an ignition promoter for the control of ignition timing. Different intake valve timings were tested for combustion phase control. Regular gasoline was tested for HCCI operation and emission characteristics with various engine conditions. With HCCI operation, ignition delay and rapid burning angle were successfully controlled by the amount of internal EGR that was determined with VVT. For best IMEP and low HC emission, DME should be injected during early compression stroke. IMEP was mainly affected by the DME injection timing, and quantities of fuel DME and gasoline. HC emission was mainly affected by both the amount of gasoline and the DME injection timing. NOx emission was lower than conventional SI engine at gasoline lean region. However, NOx emission was similar to that in the conventional SI engine at gasoline rich region. CO emission was affected by the amount of gasoline and DME.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.21 no.1
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• pp.1-10
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• 2011

Generally, the tire curing process is the process in which the sulfur is added and subsequently the tire is heated to give the tire elasticity. In this process, all kinds of the chemicals in the tire are emitted with a lot of heat. The chemical fume and heat aggravate the work environment. To solve this problem, 92 local exhaust ventilators and 8 gravity ventilators were used, but not satisfactory yet. Preliminary survey showed that the temperatures in the process were very high: 30.3, 32.9 and $37.2^{\circ}C$ at 2, 4 and 6m above the ground level, respectively in the winter (outside temperature was $2^{\circ}C$). It can be imagined that the process is severely hot in the summer time. The higher temperature distribution in the higher space tells us that the hot plume could not be removed with the existing ventilation systems. Therefore, in this study, some alternative ventilation systems were designed. The partitions were used to contain the hot plume to increase the capture efficiency. The gravity ventilators were newly designed to improve the extraction efficiency of hot fume. To satisfy the balance of pressure in the curing process, some supply air system was introduced by renewing the existing air conditioning system. Many alternative solutions were evaluated by using computational fluid dynamics modelling. The best and applicable solution was selected and the existing ventilation system was modified. After implementing the new ventilation system, the hot environment was much improved. The temperature reduction in the curing process was about $6.4^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3125-3134
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• 2010

Three-way catalyst durability in the Korea requires 5 years/80,000km in 1988 but require 10 years/120,000km after 2002. Domestic three-way catalyst satisfies exhaust gas conversion efficiency or pressure drop etc. but don't satisfy thermal durability. Three-way catalyst maintains high temperature in interior domain but maintain low temperature on outside surface. This study evaluated thermal durability of three-way catalyst by thermal flow and structure analysis and the procedure is as followings. Thermal flow parameters ranges were determined by vehicle test and basic thermal flow analysis. Response surface for rear catalyst temperature was constructed using the design of experiment (DOE) for thermal flow parameters. Thermal flow parameters for rear catalyst temperature in vehicles examination were predicted by desirability function. Temperature distribution of three-way catalyst was estimated by thermal flow analysis for predicted thermal flow parameters.

• Environmental Engineering Research
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• v.20 no.3
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• pp.260-267
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• 2015

The $PM_{10}$, $SO_2$ and $NO_2$ mass concentrations were obtained over five years from monitoring stations across Nanchong, a southwest city in China. Changes in urban air quality over time, as well as the factors influencing that change, were evaluated based on air pollutant concentrations, the Air Pollution Index (API), and the Comprehensive Pollution Index (P). The results showed that the total annual mean $PM_{10}$, $SO_2$ and $NO_2$ concentrations over the five years studied were $61.1{\pm}1.1$, $45.0{\pm}3.9$ and $34.9{\pm}4.9{\mu}g{\cdot}m^{-3}$, respectively. The annual mean concentrations displayed a generally decreasing trend; lower than the annual mean second-level air quality limit. Meanwhile, the annual mean API values were in a small range of 52-53, the air quality levels were grade II, and P values were 1.06-1.21 less than the slight level ($P{\leq}1.31$). Total monthly mean $PM_{10}$, $SO_2$, $NO_2$ concentrations, and API and P values were consistently higher in winter and spring than during autumn and summer. The results of a correlation analysis showed that temperature and pressure were the major meteorological factors influencing pollution levels. Pollution sources included industrial coal and straw burning, automobiles exhaust and road dust, fireworks, and dust storms.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.93-99
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• 1997

The re quest to develop the engines that are able to run without air or with very little oxygen condition is raised with the interest of ocean science or the mines. This research had already be gun before the world war II, but had been stagnant owing to the appearance of nuclear power. Recycle diesel engines have ability to run under the above mentioned condition the recycle diesel engine recirculates exhaust gases into intake port and consumes additional oxygen supplied by oxygen tank. Carbon dioxide is controlled by the absorber. The combustion and emission characteristics of recycle diesel engines are quite different with conventional one because the working fluids of recycle diesel engines consist of Ar, $CO_2$ and $O_2$ as well as $N_2$. Recycle diesel engine is therefore different with general diesel engine from the viewpoint of intake air composition. It is required to investigate the effect of intake composition in the combustion and emission to know recycle diesel engine. In this study, NOx concentration, smoke and cylinder pressure are measured with the variation of Ar and $CO_2$ Reduces show that the addition of Ar reduces NOx but increases smoke. Otherwise $CO_2$ reduces smoke and NOX simultaneously. Only $CO_2$ increases the ignition delay and both gases increase fuel consumption Ar addition is superior to $CO_2$ addition for the performance of recycle diesel engine system but $CO_2$ has the avantage with respect to emission.