• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1556-1571
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• 1993

Nitrogen oxides ($NO_x$) are air pollutants which are generated from the combustion of fossil fuels. Stage combustion is an effective method to reduce $NO_x$ emissions. The effects of $NO_x$ reduction by stage combustion in a pilot scale combustor(6.6kW) have been investigated using propane gas flames laden with NH$_{3}$ as Fuel-N. The results in this study are follows; (1) $NO_x$ emissions are dependent on the reducing environment of fuel-rich zone regardless of total air ratio. The maximum $NO_x$ reduction is at the stoichiometric ratio of 0.8 to 0.9 in the reducing zone. (2) $NO_x$ reduction is maximum when burnout air is injected at the point where the oxygen in reducing zone is almost consumed. (3) $NO_x$ reduction is dependent upon the temperature of reducing zone with best effect above 950.deg. C in the reducing zone. (4) The fuel stage combustion is more effective to reduce $NO_x$ formation in the wide range of stoichiometric ratio than two stage combustion. (5) The results of this study could be utilized mainly in a design strategy for low $NO_x$ emission from the combustion of high fuel-nitrogen in energy sources ratio than as an indication of the absolute levels of $NO_x$ which can be achieved by stage combustion techniques in large scale facilities.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.236-246
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• 2003

This paper focuses on developing a model of a PEM fuel cell stack and to integrate it with realistic model of the air supply system for fuel cell vehicle application. The fuel cell system model is realistically and accurately simulated air supply operation and its effect on the system power and efficiency using simulation tool Matlab/Simulink. The Peak performance found at a pressure ratio of 3, and it give a 15mV increase per cell. The limit imposed is a minimum SR(Stoichiometric Ratio) of 2 at low fuel cell load and 2.5 at high fuel cell load.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.587-592
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• 2010

A numerical analysis of reactive flow in a MILD(Moderate and Intense Low oxygen Dilution) combustor is accomplished to elucidate the characteristics of combustion phenomena in the furnace with the variation of air fuel ratio. For the smaller magnitude of air injection velocity(10 m/s), the air flow could not penetrate toward upper part of furnace. On the other hand, the air flow suppresses the fuel flow for the case of air injection velocity 30 m/s. The air velocity 18 m/s is corresponding to the stoichiometric air flow velocity, and for that case, the air flows to relatively more upper part of the furnace when compared with the case of air injection velocity 10 m/s. The reaction zone is produced with the previous flow pattern, so that the reaction zone of the air injection velocity 10 m/s is biased to the air nozzle side and for the case of air injection velocity 30 m/s, the reaction zone is inclined to the fuel nozzle side. For the cases with the air injection velocities 16, 18, 20 m/s, the reaction zone is nearly located at the center between air nozzle and fuel nozzle. The maximum temperatures and NOx concentrations for the cases of air injection velocity 16, 18, 20 m/s are lower than the cases with air injection velocity 10, 30 m/s. From the present study, the stoichiometric air fuel ratio is considered as the most optimal operating condition for the NOx reduction.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.1006-1011
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• 1991

In this paper, a neural network estimator which estimates the output of the wide range oxygen sensor is proposed, The neural network estimator is constructed to give the output of the wide range oxygen sensor from rpm, fuel injection time, throttle position, and output voltage of the exhaust gas oxygen sensor. And, using this estimator, PI controller for air-fuel ratio control is designed. Experiment results show that the proposed method gives good results for SONATA engine under light load and constant rpms.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1112-1120
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• 2002

Numerical investigations on air staging and fuel staging were carried out with a newly designed coaxial cyclone combustor, which uses the method of two stage coal combustion composed of pre-combustor and main combustor. The pre-combustor with a high air/fuel ratio is designed to supply gas at high temperature to the main combustor. To avoid local high temperature region in this process, secondary air is injected in the downstream. Together with the burned gas supplied from the pre-combustor and the preheated air directly injected into main combustor, coals supplied through the main burner react rapidly at a low air/fuel ratio. Strong swirling motion of cyclone combustor keeps the wall temperature high, which makes slagging combustion possible. Alaska, US coal is used for calculations. Predictions were made for various coal flow rates in the main combustor for fuel staging and for the various flow rate of secondary air in the pre-combustor for air staging. In-scattering angles are also chosen as a variable to increase residence times of coal particles. Temperature fields and particle trajectories for various conditions are described. Predicted temperature variations at the wall of the combustor are compared with corresponding experimental data and show a similar trend. The in-scattering angle of 20° is recommended to increase the combustion efficiency in the main chamber.

• International Journal of Automotive Technology
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• v.2 no.3
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• pp.93-101
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• 2001

Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.389-394
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• 2004

An experimental study on the NOx formation of LNG flame in fuel staged combustor has been studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is a act as a pilot flame for the secondary combustion stage combustion zone, where most of fuel bums. Experiments were performed on a semi-industrial scale (thermal input 0.233 MW) in a laboratory furnace and Liquefied Natural Gas(LNG) was used as a primary and secondary fuels. This study included parametric study to identify the optimum operating conditions which are primary/secondary fuel ratio, and primary/secondary air ratio for reducing NOx emission with two types of nozzle. The test demonstrated that NOx emission can be reduced by >70% in accordance with operating conditions.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.161-166
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• 2001

An Experimental study on the NOx formation of LNG flame in fuel staged combustor has been studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is act as a pilot flame for the secondary combustion stage combustion zone, where most of fuel burns. Experiments were performed on a semi-industrial scale (thermal input 0.233 MW) in a laboratory furnace and Liquefied Natural Gas(LNG) was used as primary and secondary fuels. The study included parametric study to identify the optimum operating conditions which are primary/secondary fuel ratio, and primary/secondary air ratio for reducing NOx emission with two types of nozzle. The test demonstrated that NOx emission can be reduced by >70% in accordance with operating conditions.

• Journal of the korean Society of Automotive Engineers
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• v.8 no.4
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• pp.13-23
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• 1986

The power of an international combustion engine depends on its ability to inhale air whether it is naturally aspirated or turbocharged. The use of fuel injection allows engine efficiency to be increased through a more even distribution of the air/fuel ratio throughout the engine's operation range. The theoretical value for complete combustion in an engine is commonly refered to as stoichiometric, which means that we require 14.7 parts of air to 1 part of gasoline. This stoichiometric ratio can be more closely maintained with electronically controlled fuel injection than it can with carburetion. Because of the greater efficiency of the engine using fuel injection, a horse power increase of at least 10% is produced over its carburetor version. In addition, better fuel economy and less exhaust emissions are also obtained.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.57-64
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• 2001

This study presents an self tuning regulator(STR) to improve the air-fuel ratio control of performance of gasoline engine. The STR is designed based on the nonlinear dynamic engine model, and the performance of the STR is evaluated through the simulation and experiments. The STR shows better performance than a conventional PI controller in terms of the response time and disturbance rejection. Since the STR has less calculation load than the complex nonlinear controller, this algorithm can be easily applied to on-board engine controller.