• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
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• pp.1-7
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• 2001

FGR is one of the most widely used methods of NOx reduction in the combustion process. It was investigated the effect of FGR, excess air ratio, peak temperature and firing rate on NOx emission in this study. 100kW burner and LNG were adopted in this experiment. NOx emission was notably decreased with the increase of FGR, however CO emission was also drastically increased in the 25% FGR. And excess air ratio, peak temperature and firing rate did not affect the NOx emission appreciably in the normal operating condition.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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• pp.129-138
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• 1999

In this paper, our main issue is that establishing the control procedure of continuous gas flow rate according to combustion fan RPM. For this, first, we decide the optimum operating condition of gas swirl burner through analysis of combustion characteristics - thermal efficiency, combustion efficiency and exhaust gases such as CO, $CO_{2}$, $O_{2}$, $NO_{x}$ and THC. Second, fuel gas flow rate of gas valve is decided with considering excess air ratio and combustion fan RPM is decided by the target of combustion air flow rate. Finally, experimental operating equation is acquired by regression for gas valve and combustion fan. This equation is the control equation of continuous gas flow rate and always gas flow rate is decided by combustion fan operating RPM.

• International Journal of Automotive Technology
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• 제5권3호
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• pp.181-188
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• 2004

A cylindrical constant-volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of an inhomogeneous charge methane-air mixture under several parameters such as stratified pattern, initial charge pressure, ignition time and the excess air ratio of the initial charge mixture. Flow characteristics including mean velocity and turbulence intensity were analyzed by a hot-wire anemometer. The combustion pressure development, measured by a piezo-electric pressure transducer, was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to near-zero value at 3000 ms. For the stratified patterns, the combustion rate under the rich injection (RI) condition was the fastest. Under the initial charge conditions, the second mixture was accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the combustion rate.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.107-113
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• 2002

LPG has been well known as a clean alternative fuel for vehicles. Recently, several LPG engines for heavy duty vehicles have been developed, which can replace some diesel engines that are one of the main sources for air pollution in the urban area. Because cylinder bore of heavy duty LPG engine is larger than that of gasoline, the study of knock characteristics of LPG engine are needed. In this study, the knock characteristics were investigated with various engine speed, air excess ratios and LPG fuel compositions. Experimental results indicated that the Knock occurrence probability decreases with increasing engine speed and propane fraction of fuel. The Knock occurrence probability is highest at excess air ratio of 1 and decreases as the mixture strength became leaner.

• 한국자동차공학회논문집
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• 제22권6호
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• pp.96-103
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• 2014

Liquefied Petroleum Gas(LPG) has attracted attention as a alternative fuel. The lean-burn LPG direct injection engine is a promising technology because it has an advantage of lower harmful emissions. This study aims to investigate the effect of combustion strategy and excess air ratio on combustion and emission characteristics in lean-burn LPG direct injection engine. Fuel consumption and combustion stability were measured with change of the ignition timing and injection timing at various air/fuel ratio conditions. The lean combustion characteristics were evaluated as a function of the excess air ratio with the single injection and multiple injection strategy. Furthermore, the feasibility of lean operation with stratified mixture was assessed when comparing the combustion and emission characteristics with premixed lean combustion.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.74-82
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• 2004

Planar laser-induced fluorescence(PLIF) has been widely used to obtain two dimensional fuel distribution. Acetone PLIF is chosen because fluorescence signal from acetone as a fluorescent tracer is less sensitive to oxygen quenching than other dopants. Acetone PLIF is applied to measure quantitative air excess ratio distribution in an engine fueled with LPG. Acetone is excited by KrF excimer laser (248nm) and its fluorescence image is acquired by ICCD camera with a cut-off filter to suppress Mie scattering from the laser light. For the purpose of quantifying PLIF signal, an image processing method including the correction of laser sheet beam profile is suggested. Raw images are divided by each intensity of laser energy and profile of laser sheet beam. Inhomogeneous fluorescence images scaled with the reference data, which is taken by a calibration process, are converted to air excess ratio distribution. This investigation shows instantaneous quantitative measurement of planar air excess ratio distribution for gaseous fuel.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.1-8
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• 2004

A cylindrical constant volume combustion chamber was used to investigate the exhaust emission characteristics of homogeneous charge, stratified pattern and inhomogeneous charge under various conditions using gas chromatography. In the case of homogeneous charge condition, the $CO_2$ concentration is proportional to excess air ratio and overall charge pressure, the $CO_2$ concentration is proportional to excess air ratio and the UHC concentration is inversely proportional to ignition time and overall charge pressure. In the case of stratified pattern, the RI(rich injection) condition shows better exhaust emission characteristics, especially $CO_2$, than that of HI (homogeneous injection) or LI (lean injection) conditions. In inhomogeneous charge conditions, when initial charge pressure is increased, $CO_2$ and UHC concentration is reduced but $O_2$ concentration is increased. And when the excess air ratio of initial charge mixture is 3.0, UHC and $CO_2$concentration show lowest values.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2916-2921
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• 2008

This paper presents the performance and characteristics of small spark-ignited small 2-stroke engine. A single cylinder, two-stroke, air cooled 23cc SI engine for brush-cutter was used in this study. For the performance of the engine, rpm, torque, fuel consumption and lubricate oil consumption were measured, and also HC, CO, NOx emissions and excess air ratio according to throat open ratio under two lubrication method were measured and analyzed. The results showed that maximum of engine rpm is nearly same in both methods and also, torque, power is similar. exhaust emissions tend to decrease with throat open ratio.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.24-31
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyzer the heat quantity of inhomogeneous charge methane-air mixture. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. It is shown that the effect of stratification is not significant in case of the overall excess air ratio of 1.1, mainly due to the higher heat loss and lower thermal efficiency compared to those of homogeneous condition. In the case of the overall excess air ratio of 1.4, as the initial charge pressure decreases, the CHR ratio has been decreased while the HL ratio has been increased, Generally, as the initial charge pressure increases, the amount of injection mixture has been decreased and has resulted in lower mean velocity and turbulence intensity for injection mixture. Also, the injected mixture is too rich to result in mixing deficiency in combustion chamber. From these results, it could be possible to acquire the improvement of thermal efficiency and the reduction of heat loss simultaneously through the 2-stage injection in CNG direct injection engine.

• 대한기계학회논문집B
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• 제39권7호
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• pp.609-615
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• 2015

본 연구는 직접분사식 가솔린엔진에서 공기 과잉률 및 바이오에탄올-가솔린 혼합연료의 혼합비에 따른 연소특성과 배기배출물 특성을 실험적으로 규명한 것이다. 다양한 공기 과잉률 및 혼합비 조건에서 실험을 수행하였으며, 연소실 압력, 열발생률, 연료소비율 등을 통해 연소특성을 분석하였으며, 배기배출물 특성은 미연탄화수소(HC), 일산화탄소(CO), 질소산화물($NO_x$) 분석을 통해 확인하였다. 혼합연료의 실험결과는 100% 가솔린 및 바이오에탄올 실험결과와 비교하였다. 실험결과 최고연소압력과 열발생률, 제동연료소비율은 혼합비의 증가에 따라 증가하였으며, CO, HC, $NO_x$와 같은 배기배출물은 바이오 에탄올 혼합비율이 증가함에 따라 감소하였다. 혼합연료의 배기배출물 수준은 가솔린 보다 낮게 나타났다.