• Advances in aircraft and spacecraft science
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• v.1 no.3
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• pp.311-330
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• 2014

Environmental impact of aircraft emissions can be addressed in two ways. Air quality impact occurs during landings and takeoffs while in-flight impact during climbs and cruises influences climate change, ozone and UV-radiation. The aim of this paper is to investigate airports related local emissions and fuel consumption (FC). It gives flight path optimization model linked to a dispersion model as well as numerical methods. Operational factors are considered and the cost function integrates objectives taking into account FC and induced pollutant concentrations. We have compared pollutants emitted and their reduction during LTO cycles, optimized flight path and with analysis by Dopelheuer. Pollutants appearing from incomplete and complete combustion processes have been discussed. Because of calculation difficulties, no assessment has been made for the soot, $H_2O$ and $PM_{2.5}$. In addition, because of the low reliability of models quantifying pollutant emissions of the APU, an empirical evaluation has been done. This is based on Benson's fuel flow method. A new model, giving FC and predicting the in-flight emissions, has been developed. It fits with the Boeing FC model. We confirm that FC can be reduced by 3% for takeoffs and 27% for landings. This contributes to analyze the intelligent fuel gauge computing the in-flight fuel flow. Further research is needed to define the role of $NO_x$ which is emitted during the combustion process derived from the ambient air, not the fuel. Models are needed for analyzing the effects of fleet composition and engine combinations on emission factors and fuel flow assessment.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.355-362
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• 2009

Fuels based on petroleum will eventually run out in the near future. DME (Di-methyl Ether) is a clean energy source that can be manufactured from various raw materials such as natural gas, coal as well as biomass. As DME has no carbon-carbon bond in its molecular structure and is an oxygenate fuel, its combustion essentially generates no soot as well as no SOx. Because the physical properties of DME are similar to those of LPG, the LPG distribution infrastructure can be converted to use with DME. DME has such high cetane number of 55~60 that it can be used as a diesel engine fuel. Practical use of DME as a next-generation clean fuel or next-generation chemical feedstock is advancing in the fields of power generation, diesel engines, household use, and fuel cells, among others. The purpose of this paper is review the characteristics, standardization, status of research and development in domestic and foreign countries of DME.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.11
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• pp.1065-1072
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• 2012

Due to its oxygen (O) content, biodiesel (BD) is advantageous in that it lowers PM emissions in CI engines. Therefore, BD is considered one of the best candidates for low temperature combustion (LTC) operation because its use can extend the regime for simultaneous reduction of PM and $NO_x$. Thus, in this study, LTC operation was realized using BD and diesel with a 5~7% $O_2$ fraction. Engine test results show that the use of BD increased the efficiency and reduced emissions such as PM, THC, and CO; furthermore, IMEP reduced by 10~12% owing to the lower LHV of the fuel. In particular, smoke was suppressed by up to 90% because O atoms in the BD enhanced the soot oxidation reaction. To compensate the IMEP loss, turbocharging (TC) was then tested, and the results showed that the power output increased and PM was reduced further. Moreover, TC in BD engine operation allowed a similar level of reduction in both $NO_x$ and PM at 11~12% $O_2$ fraction, suggesting that there is a potential to widen the operating range by the combination of TC and BD.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.196-205
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• 2016

The exhaust gas discharged by cars not only threatens the health of the human body, but also contributes to global warming, due to the resulting increase in the concentrations of ozone, fine dust and carbon dioxide. Therefore, the government has steadily implemented careful inspection systems for exhaust emissions, in order to efficiently regulate the exhaust gas of cars. Studies on reducing the exhaust emissions of automobiles have been conducted in various fields, including ones designed to reduce the generation of HC, NOx, and $CO_2$ in the exhaust emission of vehicles. However, there have been insufficient studies on the reduction of the exhaust emission for old diesel vehicles. To develop careful inspection systems for the exhaust emissions of old diesel vehicles, studies on the reduction of the exhaust emissions and improvement of power are necessary by cleaning the carbon sediment in both the intake manifold and injector. Therefore, in this study, we analyzed and compared the amounts of gas emitted when simultaneously cleaning or not cleaning the intake manifold and injector of diesel automobiles with mileages over 80,000 km and operating periods over 5 years. The experimental results showed that in the case where the intake manifold and injector were simultaneously cleaned, there was a decline of 75.2% in the gas emission compared to the cases where only the manifold or injector is cleaned. Also, it was found that simultaneously cleansing the intake manifold and injector enabled the exhaust standard to be satisfied for less than 30% within 8.5 sec.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.155-166
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• 2014

This review will be concentrated on the spray characteristics of bioethanol and its derived fuels such as ethanol-diesel, ethanol-biodiesel in compression ignition (CI) engines. The difficulty in meeting the severe limitations on NOx and PM emissions in CI engines has brought about many methods for the application of ethanol because ethanol diffusion flames in engine produce virtually no soot. The most popular method for the application of ethanol as a fuel in CI engines is the blending of ethanol with diesel. The physical properties of ethanol and its derivatives related to spray characteristics such as viscosity, density and surface tension are discussed. Viscosity and density of e-diesel and e-biodiesel generally are decreased with increase in ethanol content and temperature. More than 22% and 30% of ethanol addition would not satisfied the requirement of viscosity and density in EN 590, respectively. Investigation of neat ethanol sprays in CI engines was conducted by very few researchers. The effect of ambient temperature on liquid phase penetration is a controversial topic due to the opposite result between two studies. More researches are required for the spray characteristics of neat ethanol in CI engines. The ethanol blended fuels in CI engines can be classified into ethanol-diesel blend (e-diesel) and ethanol-biodiesel (e-biodiesel) blend. Even though dodecanol and n-butanol are rarely used, the addition of biodiesel as blend stabilizer is the prevailing method because it has the advantage of increasing the biofuel concentration in diesel fuel. Spray penetration and SMD of e-diesel and e-biodiesel decrease with increase in ethanol concentration, and in ambient pressure. However, spray angle is increased with increase in the ethanol percentage in e-diesel. As the ambient pressure increases, liquid phase penetration was decreased, but spray angle was increased in e-diesel. The increase in ambient temperature showed the slight effect on liquid phase penetration, but spray angle was decreased. A numerical study of micro-explosion concluded that the optimum composition of e-diesel binary mixture for micro-explosion was approximately E50D50, while that of e-biodiesel binary mixture was E30B70 due to the lower volatility of biodiesel. Adding less volatile biodiesel into the ternary mixture of ethanol-biodiesel-diesel can remarkably enhance micro-explosion. Addition of ethanol up to 20% in e-biodiesel showed no effect on spray penetration. However, increase of nozzle orifice diameter results in increase of spray penetration. The more study on liquid phase penetration and SMD in e-diesel and e-biodiesel is required.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.111-112
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• 2009

Diamond-like carbon (DLC) is a convenient term to indicate the compositions of the various forms of amorphous carbon (a-C), tetrahedral amorphous carbon (ta-C), hydrogenated amorphous carbon and tetrahedral amorphous carbon (a-C:H and ta-C:H). The a-C film with disordered graphitic ordering, such as soot, chars, glassy carbon, and evaporated a-C, is shown in the lower left hand corner. If the fraction of sp3 bonding reaches a high degree, such an a-C is denoted as tetrahedral amorphous carbon (ta-C), in order to distinguish it from sp2 a-C [2]. Two hydrocarbon polymers, that is, polyethylene (CH2)n and polyacetylene (CH)n, define the limits of the triangle in the right hand corner beyond which interconnecting C-C networks do not form, and only strait-chain molecules are formed. The DLC films, i.e. a-C, ta-C, a-C:H and ta-C:H, have some extreme properties similar to diamond, such as hardness, elastic modulus and chemical inertness. These films are great advantages for many applications. One of the most important applications of the carbon-based films is the coating for magnetic hard disk recording. The second successful application is wear protective and antireflective films for IR windows. The third application is wear protection of bearings and sliding friction parts. The fourth is precision gages for the automotive industry. Recently, exciting ongoing study [1] tries to deposit a carbon-based protective film on engine parts (e.g. engine cylinders and pistons) taking into account not only low friction and wear, but also self lubricating properties. Reduction of the oil consumption is expected. Currently, for an additional application field, the carbon-based films are extensively studied as excellent candidates for biocompatible films on biomedical implants. The carbon-based films consist of carbon, hydrogen and nitrogen, which are biologically harmless as well as the main elements of human body. Some in vitro and limited in vivo studies on the biological effects of carbon-based films have been studied [$2{\sim}5$].The carbon-based films have great potentials in many fields. However, a few technological issues for carbon-based film are still needed to be studied to improve the applicability. Aisenberg and Chabot [3] firstly prepared an amorphous carbon film on substrates remained at room temperature using a beam of carbon ions produced using argon plasma. Spencer et al. [4] had subsequently developed this field. Many deposition techniques for DLC films have been developed to increase the fraction of sp3 bonding in the films. The a-C films have been prepared by a variety of deposition methods such as ion plating, DC or RF sputtering, RF or DC plasma enhanced chemical vapor deposition (PECVD), electron cyclotron resonance chemical vapor deposition (ECR-CVD), ion implantation, ablation, pulsed laser deposition and cathodic arc deposition, from a variety of carbon target or gaseous sources materials [5]. Sputtering is the most common deposition method for a-C film. Deposited films by these plasma methods, such as plasma enhanced chemical vapor deposition (PECVD) [6], are ranged into the interior of the triangle. Application fields of DLC films investigated from papers. Many papers purposed to apply for tribology due to the carbon-based films of low friction and wear resistance. Figure 1 shows the percentage of DLC research interest for application field. The biggest portion is tribology field. It is occupied 57%. Second, biomedical field hold 14%. Nowadays, biomedical field is took notice in many countries and significantly increased the research papers. DLC films actually applied to many industries in 2005 as shown figure 2. The most applied fields are mold and machinery industries. It took over 50%. The automobile industry is more and more increase application parts. In the near future, automobile industry is expected a big market for DLC coating. Figure 1 Research interests of carbon-based filmsFigure 2 Demand ratio of DLC coating for industry in 2005. In this presentation, I will introduce a trend of carbon-based coating research and applications.