• Journal of Mechanical Science and Technology
• /
• 제16권1호
• /
• pp.116-124
• /
• 2002

In order to investigate the soot formation and oxidation processes, we employed the two variable approach and its source terms representing soot nucleation, coagulation, surface growth and oxidation. For the simulation of the taxi-symmetric turbulent reacting flows, the pressure-velocity coupling is handled by the pressure based finite volume method. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical models used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reacting flow field.

• 한국자동차공학회논문집
• /
• 제10권6호
• /
• pp.80-89
• /
• 2002

The flame structure and soot formation in Acetylene-Air nonpremixed jet flame are numerically analyzed. We employed two variable approach to investigate the soot formation and oxidation processes. The present soot reaction mechanism involves nucleation, surface growth, particle coagulation, and oxidation steps. The gas phase chemistry and the soot nucleation, surface growth reactions are coupled by assuming that the nucleation and soot mass growth has the certain relationship with the concentration of pyrene and acetylene. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical model used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reaction flow field.

• 공업화학
• /
• 제22권4호
• /
• pp.400-404
• /
• 2011

백금이 코팅된 메탈 필터 소재의 NOx, soot 산화반응의 안정성 및 활성에 대하여 연구하였다. NOx와 soot 산화실험은 독립 또는 동시에 반응시킨 조건으로 수행되었다. 그 결과, 백금이 코팅된 소재는 20%의 NO의 $NO_2$로의 전환반응, 약 10%의 NOx 분해반응 그리고 soot의 완전산화반응이 진행됨을 보였다. Soot 산화반응은 $NO_2$의 생성으로 인하여 반응온도가 더 저온으로(약 $30^{\circ}C$) 이동할 수 있었다. 코팅 소재는 $Pt/Al_2O_3$ 또는 $Pt/TiO_2$ 촉매보다 표면구조의 안정성으로 인하여 열충격에 대한 내구성이 우수하였다.

• 대한기계학회논문집
• /
• 제14권5호
• /
• pp.1222-1233
• /
• 1990

본 연구에서는 급속압축장치에서 실현된 단발분무하염내의 매연을 레이저음영 사진법에 의하여 가시화하고, 화염내의 매연농도의 시간적, 공간적분포를 조사한다. 또 전보에서 측정된 비증발분무내의 당량비분포와 비교검토하여 디젤화염내의 매연 생 성기구를 고찰하고, 분위기조건에 따른 착화지연이 매연생성에 미치는 영향 및 매연생 성과 열발생율과의 관계를 밝힌다.

• 한국자동차공학회논문집
• /
• 제13권1호
• /
• pp.68-75
• /
• 2005

By utilizing a semi-empirical soot model, the applicability of the laminar flamelet concept fur simulating the formation and oxidation of soot in the laminar diffusion flame has been studied. The source terms for two transport equations of the soot formation and oxidation are calculated in the mixture fraction/scalar dissipation rate space for laminar flamelets and stored in a library. In this study, emphasis is given to the interaction associated with radiation and soot formation. The radiative heat loss is obtained by solving the radiative transfer equation using the unstructured grid finite volume method with the WSGGM. The calculated temperatures and soot volume fractions agree relatively well with the experimental data and the previous numerical results of Kaplan et al. using the detailed chemistry.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.2965-2970
• /
• 2008

Effects of split injection and oxygen-enriched air on soot emissions in a DI diesel engine were studied by the KIVA-3V code. When split injection is applied, the second injection of fuel into a cylinder results in two separate stoichiometric zones which increases soot oxidation. As a result, soot emissions are decreased with split injection. When oxygen-enriched air is applied together with split injection, higher concentration of oxygen helps secondary combustion which results in a higher temperature in the cylinder. The increased temperature promotes growth reaction of acetylene with soot but doesn't improve the acetylene formation during the second injection of fuel. As more acetylene is consumed in the growth reaction of acetylene, the net acetylene mass in the cylinder is decreased, which leads to a decrease of soot formation. With an increase of soot oxidation caused by split injection, the soot emissions are decreased significantly. However, to avoid excessive NOx emissions with increased oxygen concentration, the level of oxygen concentration should be lower than 22% in volume.

• 공업화학
• /
• 제21권2호
• /
• pp.178-182
• /
• 2010

다양한 $TiO_2$를 담체로 한 Pt계 촉매에서 NOx, soot의 동시 제거 반응에 대한 연구를 수행하였다. 실험은 각 촉매를 NOx와 soot의 반응을 독립 또는 동시에 반응시킨 조건으로 수행하였으며 그 결과 $TiO_2$의 종류에 따라 서로 상이한 NOx 제거능력과 soot 산화력을 나타내었다. 또 NOx 독립 실험 시 생성된 $NO_2$ 양과 soot 산화시작온도가 저온으로 이동하는 정도가 관계가 있었다. 담체의 물성 중 Pt의 뭉침현상에 결정적 역할을 미치는 비표면적과 촉매의 환원력에 영향을 미치는 crystallite size가 NO의 $NO_2$ 전환반응에 밀접한 관계를 가지는 것으로 조사되었다. 따라서 반응의 중요한 인자는 촉매에 사용되는 담체의 물리화학적 특성임을 알 수 있었다.

• Journal of Mechanical Science and Technology
• /
• 제16권6호
• /
• pp.851-860
• /
• 2002

In this study, it was attempted to obtain the fundamental data for the formation and oxidation of soot from a diesel engine. Combustion of spray injected into a cylinder is complex phenomenon having physical and chemical processes, and these processes affect each other. There are many factors in the mechanism of the formation and oxidization of soot and it is necessary to observe spray combustion microscopically. In order to observe with that view, free fuel droplet array was used as an experimental object and the droplet array was injected into an atmospheric combustion chamber with high temperature. Ambient temperature of the combustion chamber, interdroplet spacing, and droplet diameter were selected as parameters, which affect the formation and oxidation of soot. In this study, it was found that the parameters also affect ignition delay of droplet. The ambient temperature especially affected the ignition delay of droplet as well as the flame temperature after self-ignition. As the interdroplet spacing that means the local equivalence ratio in a combustion chamber was narrow, formation of soot was increased. As diameter of droplet was large, surface area of the droplet was also broad, and hence evaporation of the droplet was more active than that of a droplet with relative small diameter.

• 한국연소학회지
• /
• 제8권1호
• /
• pp.9-16
• /
• 2003

Carbon soot emission from combustion processes, especially from diesel engines, is a subject of growing concern since soot is known to seriously affect human health. Efforts have been made to oxidize soot particles utilizing Non-Thermal Plasma(NTP) techniques. When oxygen is carried into a plasma device, electrons generated by the plasma dissociate the oxygen, resulting in the formation of oxygen atoms. These highly activated atoms, called O radicals, are known as strong oxidizing agent. This paper presents concentration variations of CO and $CO_2$ at the exit of the plasma device, resulting from the soot oxidation by O radicals, with variations of inlet oxygen concentration, gas temperature, and gas flow rate. Based on the data, Arrehenious rate constants of reactions between C(s)+O and C(s)+O+O were proposed.

• 한국자동차공학회논문집
• /
• 제5권2호
• /
• pp.173-182
• /
• 1997

The instantaneous flame temperature and soot formation and oxidation in a D. I. diesel engine are measured by using a two-color method. The proposed method based on the continuous spectral radiation from the soot particles in flames is applicable to industrial diesel engines without major modifications of their main characteristics. Measurements are performed at one location inside the combustion chamber of a D.I. diesel engine. Effects of different engine speeds and loads on flame temperature and KL factor which is an index of soot concentrations were examined. A little temperature change were observed with increasing engine speed, while increased with loads. The higher the flame temperature is, the lower the KL factor is.