• 한국연소학회지
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• 제20권3호
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• pp.21-26
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• 2015

This study was performed to provide the information of the combustion characteristics of n-butanol fuel in accordance with the n-heptane fuel mixing ratio. The closed homogeneous reactor model was used for the analysis. The analysis conditions were set to 800 K of the initial temperature, 20 atm of initial pressure and 1.0 of equivalence ratio. The results of analysis were compared in terms of combustion temperature, combustion pressure, CO, Soot and $NO_X$ emissions. The results of combustion and exhaust emission characteristics showed that ignition delay was decreased and the combustion temperature was increased as the n-heptane mixing ratio was increased. Also, the carbon monoxide(CO) was slightly decreased however, the soot and nitrogen oxides($NO_X$) increased a little in accordance with the n-heptane fuel mixing ratio. In addition, the pressure difference was almost the same in any conditions.

• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.524-534
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• 2013

Gasoline direct injection(GDI) engine has a high thermal efficiency, but it has a problem to increase carbon emissions such as soot and $CO_x$. In this study, the objective is to analyze numerically a problem for adding the hydrogen during the intake stroke so as to reduce the injected amount of gasoline in GDI engines. For selection of the base model, the cylinder pressure of simulation is matched to experimental data. The numerical analysis are carried out by a CFD model with the hydrogen addition of 2%, 3% and 4% on the volume basis. In the case of 3% hydrogen addition, the injected gasoline amount is only changed to match the maximum pressure of simulation to that of the base model for additional study. It is found that the combustion temperature and pressure increase with the hydrogen addition. And NO emission also increases because of the higher combustion temperature. $CO_x$ emissions, however, are reduced due to the decrease of injected gasoline amount. Also, as the injected gasoline amount is reduced for the same hydrogen addition ratio, the gross indicated work is no significant, But NO and $CO_x$ emissions are considerably decreased. On the order hand, $CO_x$ emissions of two cases are more decreased and their gross indicated works are higher obtained than those of the base model.

• 한국분무공학회지
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• 제15권1호
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• pp.31-37
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• 2010

The aim of this work is to investigate the spray and combustion characteristics of dimethyl-ether (DME) at various injection conditions. The spray characteristics such as spray tip penetration and spray cone angle were experimentally studied from the spray images which obtained from the spray visualization system. Combustion and emissions characteristics were numerically investigated by using KIVA-3V code coupled with Chemkin chemistry solver. From these results, it revealed that DME spray had a shorter spray tip penetration and wider spray cone angle than that of diesel spray due to the low density, low surface tension, and fast evaporation characteristics. At the constant heating value condition, DME fuel showed higher peak combustion pressure and earlier ignition timing, because of high cetane number and superior evaporation characteristics. In addition, the combustion of DME exhausted more $NO_x$ emission and lower HC emission due to the active combustion reaction in the combustion chamber. The result shows that DME had a little soot emission due to its molecular structure characteristics with no direct connection between carbons.

• 한국가시화정보학회지
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• 제3권2호
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• pp.14-20
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• 2005

내연기관 연소는 난류유동, 분무, 연소, 열전달의 복합적인 현상으로서 열역학적 해석이 주류를 이루어 왔으나 컴퓨터의 발전에 따라 효율 개선과 공해 저감을 목표로 전산유체해석 기법이 적극적으로 도입되고 있다. 내연 기관 연소의 근간을 형성하는 난류 연소 모델링의 기본 개념으로서 가솔린엔진에서의 예혼합연소와 디젤엔진에서의 확산연소에 대한 영역조건평균(zone conditional averaging) 모델과 조건평균닫힘(conditional moment closure) 모델에 대해 설명하였으며 $NO_x$와 soot 예측에 대한 적용과 엔진응용 사례를 소개하였다.

• 한국분무공학회지
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• 제25권1호
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• pp.21-26
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• 2020

The objective of this work is to numerically reveal the effect of equivalence ratio change on the simultaneous reduction of NO_X and soot emissions from the simulated-EGR compression ignition engine containing CO₂. An experiment was conducted by using a single-cylinder common-rail injection system engine, an intake control system, and exhaust emissions analyzers. The numerical analysis results were validated under the same experimental conditions. To investigate the effect of equivalence ratio by simulated-EGR containing CO₂, the O₂, N₂, and CO₂ mole fraction were changed in the initial air conditions to the cylinder. The results were analyzed in terms of peak cylinder pressure, indicated mean effective pressure, indicated specific nitrogen oxide, and indicated specific soot. It was revealed that ignition delay characteristics and heat release rate (ROHR) characteristics were not significantly different according to the equivalence ratio. However, as the equivalence ratio increased from 0.68 to 0.83, the maximum combustion pressure and IMEP decreased by about 6.5% and 9.4%, respectively. In the case of ISFC, as is well known, the trend is opposite of IMEP. In the case of ISNO, as the equivalence ratio increased, less NO was generated, and as the equivalence ratio increased by 0.05, the ISSoot value of about 10% increased.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.12-23
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• 2004

The effects of improved rice bran oil on the characteristics of exhaust emissions have been experimentally examined by a single cylinder, four cycle, direct injection, water-cooled agricul-tural diesel engine operating at several loads and speeds. The experiments are conducted with light oil, rice bran oil, and improved rice bran oil as a fuel. The fuel injection timing is fixed to 22$^{\circ}$ BTDC regardless of fuel types, engine loads and speeds. To reduce the viscosity of rice bran oil, it is used with the methods of heating, methyl ester and ultrasonic system in a highly viscous rice bran oil. In this study, it is found that the brake specific fuel consumption rate of light oil is the lowest and that of improved rice bran oils is lower than that of pure rice bran oil, and NO$_{x}$ emissions of light oil are the lowest and those of pure rice bran oil are the high- est, while soot emissions of light oil are the highest and those of pure and improved rice bran oils are lower than that of light oil. However these results are not amply satisfied with the emissions regulation limit using the pure and improved rice bran oil as fuels in diesel engines.s.

• 대한기계학회논문집B
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• 제40권9호
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• pp.569-576
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• 2016

본 연구는 HSDI 디젤 엔진의 연소 성능 향상을 위해 연료 분사 타겟팅의 최적화를 수치 해석적으로 연구하였다. 연구에 적용된 연소모델은 ECFM-3Z모델을 사용하였고, 해석에 필요한 엔진 부하 및 연료의 타겟팅은 분사량, 분사각도, 분사시기를 변경하여 해석한 실린더압력, 열 발생률, 배기 배출물 특성의 결과를 비교 분석하여 연구하였다. 연구결과, 분사시기와 분사각도에 따라 연료가 피스톤 보울 안쪽으로 많이 유입될수록 열 발생률의 증가로 인하여 $NO_x$는 증가하였고, CO, Soot은 연소성능의 증진으로 감소하는 것을 확인할 수 있었다. 또한, 분사시기가 진각될수록 균일 혼합기 형성시간이 충분하여 연소성능이 증진되고, 실린더압력은 증가하였다.

• 한국연소학회지
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• 제15권3호
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• pp.57-66
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• 2010

The purpose of this paper is to investigate the effects of fuel injection strategy and engine load on the structure and emissions characteristics of a DI diesel engine with 1.6L of piston displacement. In order to analyze the particulate matter (PM) and exhaust emissions characteristics in a direct injection diesel engine, the quantity of PM and exhaust emissions (including HC, CO and $NO_X$) were investigated under various injection strategies and engine loads. Two different injection strategies (one pilot/main injection and two pilots/main injection) was investigated under the various engine loads. A thermophoretic sampling method with a scanning electron microscope (SEM) were used to obtain the PM morphology (including primary particles, the size of the agglomerates, the number of agglomerates, the fractal dimension). The quantity of soot gradually increased with increasing engine load at both injection strategies. The primary particles in the PM agglomerates indicate that the average of the primary particle and radius of gyration increased as the engine load increased.

• 한국자동차공학회논문집
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• 제20권1호
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• pp.88-94
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• 2012

One of the effective ways to reduce both $NO_x$ and PM at the same time in a diesel CI engine is to operate the engine in low temperature combustion (LTC) regimes. In general, two strategies are used to realize the LTC operation-dilution controlled LTC and late injection LTC - and in this study, the former approach was used. In the dilution controlled regime, LTC is achieved by supplying a large amount of EGR to the cylinder. The significant EGR gas increases the heat capacity of in-cylinder charge mixture while decreasing oxygen concentration of the charge, activating low temperature oxidation reaction and lowering PM and $NO_x$ emissions. However, use of high EGR levels also deteriorates combustion efficiency and engine power output. Therefore, it is widely considered to use increased intake pressure as a way to resolve this issue. In this study, the effects of intake pressure variations on performance and emission characteristics of a single cylinder diesel engine operated in LTC regimes were examined. LTC operation was achieved in less than 8% $O_2$ concentration and thus a simultaneous reduction of both PM and $NO_x$ emission was confirmed. As intake pressure increased, combustion efficiency was improved so that THC and CO emissions were decreased. A shift of the peak Soot location was also observed to lower $O_2$ concentration while $NO_x$ levels were kept nearly zero. In addition, an elevation of intake pressure enhanced engine power output as well as indicated thermal efficiency in LTC regimes. All these results suggested that LTC operation range can be extended and emissions can be further reduced by adjusting intake pressure.

• Advances in aircraft and spacecraft science
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• 제1권3호
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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.