• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.05a
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• pp.38-40
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• 2003

본 연구에서 적용한 저 NOx 연소법의 NOx 저감 효과를 비교해 보면 다단 연소법이 지연연소 효과와 국부적인 최고 화염온도 감소, 고온부에서의 산소농도 감소효과 등이 동시에 나타나 저 과잉공기 연소법, 배기가스 재순환법, 이단 연소법 보다 더 큰 NOx 저감효과를 얻을 수 있음을 알 수 있었다. 다만, 총 공급공기 량에 대한 분할 공급공기량의 비가 일정수준 이상으로 커지면 CO 발생량 증가로 효율저하 등의 문제점이 우려되므로 연소상태를 저하시키지 않는 공급비를 산정하는 것이 중요할 것으로 생각된다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.963-969
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• 2014

Four coal sources that had different ash contents were evaluated in a drop tube furnace (DTF). Combustion experiments were conducted by using several sources with different particle sizes and excess air ratios under air-staging conditions to determine the optimized combustion conditions of high-ash coal, with an emphasis on the combustion efficiency and NOx emissions. The results show that the higher ash content results in a large amount of carbon remaining unburned, and that this effect is dominant when the largest particle size is used. Furthermore, the ash content of coal does affect the Char-NOx concentration, which decreases with the particle size. The results of this study suggest that an air-staged system can be useful to reduce the NOx emissions of high-ash coal and that control of the air stoichiometric ratio of the primary combustion zone (SR1) is effective for reducing NOx emissions, especially by considering unburned carbon contents.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.63-69
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• 2014

The oxidizer-rich preburner's combustion tests were fulfilled in the development process of staged combustion cycle rocket engines. The exhaust plume from an oxidizer-rich preburner is relatively transparent because combustion takes place in oxidizer rich state. During hot fire tests a still and infrared images were captured to visualize the plume structure, temperature distribution and so on. In addition, the exhaust plume was numerically investigated to figure out the detailed characteristics. The combustion was not considered for the numerical modeling, but the mixing of exhaust plume with circumstantial air was modeled by species transport model with several turbulence models. The inner structure of plume was configured out by the comparison of numerical results with experimental results, and the validity of applied numerical models was verified.

• 연구논문집
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• s.27
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• pp.101-108
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• 1997

The characteristics of combustion and emissions in multi-staged oil burner have been experimentally studied for the various range of equivalence ratios, drop sizes and fuel formulations. Malvern system was used to measure droplet size of fuel. Light fuel oil and light fuel oil doped with pyridine($C_5H _5N$) were used to investigate the effects on fuel NOx emission. The emissions of NO and CO in exhaust gas and the flame temperatures were measured by the gas analyzer and thennocouples. NOx emissions were increased by increasing the excess air ratio (range:$lambda=1.1-1.4$) or decreasing the SMD of droplet in single-staged burner. In comparison with the single-staged burner, the emission of NOx in multi-staged burner was reduced by 50% but CO emission was slightly increased. It is found that multi-staged burner has a good capability in reducing thermal NOx resulting from the distributed heat release rate and lower flame temperature in fuel-rich and fuel-lean combustion zone. Moreover, the fuel NOx emission of the multi-staged burner is lower than that of single-staged burner, because multi-staged burner has fuel rich zone where fuel N is converted to $N_2$ more than NO. In 3-staged burner, the percentage of each stage combustion air have strong influence on emission characteristics. It is also found that NOx emission can be reduced by decreasing inner and outer air percentage or increasing middle air flow rate and CO emission is vice versa.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.11
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• pp.858-868
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• 2009

A numerical investigation has been carried out about the performance of a 500MW class tangentially coal-fired boiler, focusing on the optimization of separated overfire air (SOFA) position to reduce NOx emission. For this purpose, a comprehensive combination of NOx chemistry models has been employed in the numerical simulation of a particle-laden flow along with solid fuel combustion and heat and mass transfer. A reasonable agreement has been shown in baseline cases for predicted operational parameters compared with experimental data measured in the boiler. A further SOFA calculation has been made to obtain optimum elevation and position of SOFA port. Additionally, clarifying on the effect of SOFA on NOx emission has been carried out in the coal-fired boiler. As a result, this paper is valuable to provide an information about the optimum position of SOFA and the mechanism by which the SOFA would affect NOx emission.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.335-342
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• 2012

Nowadays, automobile manufacturers are focusing on the reduction of exhaust-gas emissions because of the harmful effects on humans and the environment, such as global warming by greenhouse gases. Gasoline direct injection (GDI) combustion is a promising technology that can improve fuel economy significantly compared to conventional port fuel injection (PFI) gasoline engines. In the present study, ultra-lean combustion with an excess air ratio of over 2.0 is realized with a spray-guided-type GDI combustion system, so that the fuel consumption is improved by about 13%. The level of exhaust-gas emissions and the operation performance with the multiple injection strategy and exhaust-gas recirculation (EGR) are examined in comparison with the emission regulations and from the point of view of commercialization.