• 대한기계학회논문집B
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• 제20권10호
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• pp.3243-3250
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• 1996

Emission characteristics of nitric oxides and carbon monoxide from a porous media combustor has been experiment studied. The relationship between the change of flame shape and emission has also been examined. As the equivalence ratio decreases, the flame shape on the ceramic matrix plate changes from a diffusion flame, R(radiant)-type flame, to B(Blue)-type flame. With large fuel flow rate, R-type flame turns to be two dimensional R-II type flame around the equivalence of 0.7. Carbon monoxide emission increases very rapid with decreasing equivalence ratio. It changes a lot from some 10 ppm to 100-10,000 ppm with the change of flame type from R-I to R-II type. Nitric oxide emission from the premixed burner is less than 25 ppm over all range of fuel flow rate, which is less than 20% of NOx emission from conventional gas burners.

• 대한기계학회논문집
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• 제19권8호
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• pp.2022-2029
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• 1995

The experiment was performed by using the condenser discharge ignition device in a constant volume combustion chamber for high pressure, equivalent to the TDC of spark ignition engine, which makes the forced turbulent field possible. The conclusions obtained under various initial pressures, initial temperatures, and turbulent conditions of the methanol-air mixture are as follows : As initial pressure, initial temperature of the mixture, and the ignition energy increase, the inflammability limit expands, but the lean inflammability limit decreases as turbulence intensity increases. Combustion duration is shorter in the case of the lower initial pressure, the higher initial temperature, an equivalence ratio of 1.1-1.2, and even though turbulence intensity increases up to optimum value. Maximum combustion pressure increases in turbulent ambience under the same mixture condition, only in the case each optimum turbulence intensity exists under every condition. As the turbulence intensity increases .tau.$_{10}$ proportion increases while the .tau.$_{pr}$ proportion decreases....

• 한국자동차공학회논문집
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• 제13권2호
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• pp.44-51
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• 2005

According to the increasing concern on the global environment, the $CO_2$ regulation has been discussed including automobile emission regulation. In order to cope with this rapid changing circumstances, the development of an ultra low emission and super fuel economy automobile is essential. Direct injection LPG engine is the one of the possible future engine to maximize the engine efficiency. This experimental study for the development of direct injection LPG engine technology is promoted with two parts; spray characteristics of high pressure swirl injector, and performance characteristics of direct injection LPG engine. Engine characteristics according to the fuel was analyzed in order to establish stratified combustion technology for LPG engine by using the DISI engine. In the engine experiment, control system was manufactured for gasoline and LPG fuel. The engine was modified 2,000 cc GDI engine (fuel supply device, fuel injection device). Through this experiment, engine operating condition, engine speed and spark timing (MBT), fuel injection position, and fuel rate were investigated.

• 한국자동차공학회논문집
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• 제23권4호
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• pp.402-409
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• 2015

In this study a quasi-dimensional model is developed to predict the combustion process and emissions of a GDI engine under ultra-lean conditions. Combustion of a GDI engine condition is modeled as two simultaneous processes to consider significant fuel stratification. The first process is premixed flame propagation described as burning in a hemispherically propagating flame. The second is diffusion-controlled combustion modeled as mixing of multiple spray zones in the burned gas region. Mixing is an important factor in ultra-lean conditions leaving stratified mixture of developing sprays behind the propagating premixed flame. Sheet breakup and Hiroyasu models are applied to predict the velocity of a hollow cone spray. Validation is performed against measured pressures and NOx and CO emissions at different load and rpm conditions in the test engine.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.23-28
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• 2011

To secure basic data for intake port design, effects of a port masking on the part load performance were investigated in a 4 valve SI engine. For this purpose, 9 kinds of masking, which have different shapes and masking ratio, are applied to the engine intake system. The characteristics of the performance were estimated through mixture response test at various engine load and speed. The results show that NOx emission, one of indexes for stratification, increases considerably in spite of retarded spark timing due to the stratification which is caused by unequal flow distribution between the two intake ports. The mechanism of stratification by masking is different from axial stratification and the fuel entering through masked port plays a very important role in this stratification process. In conclusion, the port masking method could be easily applied to engine intake system and be very effective for inducing the stratified charging without the change of port design.

• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.184-191
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• 1999

Th effects of exhaust gas recirculation(EGR) on the characteristics of combustion exhaust emissions and specific fuel consumption(SFC) are experimentally investigated by four-cylin-der four-cycle and direct injection marine diesel engine. In order to reduce soot contents in the recirculated exhaust gas to intake system of the engines a novel diesel soot removal system with a cylinder-type scrubber which has water injector(4 nozzles in 1.0mm diameter)is specially designed and manufactured for the experi-mental system. The obtained results are as follows; The combustion pressure in cylinder is decreased and ignition is delayed with increasing EGR rate. The accumulated quantity of heat release is slightly decreased and the tendency of heat release rate is not constant. NOx and Soot emissions are decreased by maximum 7% and 540% with scrubber tan without scrubber in the range of experimental conditions. Those are increased at the lean burn area with increasing equivalence ration in the constant value of engine speed and EGR rate. Also those are decreased with increasing EGR rate in the constant value of engine speed and equivalence ratio.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2928-2933
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• 2008

Trends of the automotive market require the application of new engine technologies, which allows for the use of different types of fuel. Since ethanol is a renewable source of energy and it contributes to lower $CO_2$ emissions, ethanol produced from biomass is expected to increase in use as an alternative fuel. It is recognized that for spark ignition (SI) engines ethanol has advantages of high octane number and high combustion speed. In spite of the advantages of ethanol, fuel supply system might be affected by fuel blends with ethanol like a wear and corrosion of electric fuel pumps. So the on-board hydrogen production out of ethanol reforming can be considered as an alternative plan. This paper investigates the influence of ethanol fuel on SI engine performance, thermal efficiency and emissions. The combustion characteristics with hydrogen-enriched gaseous fuel from ethanol reforming are also examined.

• 한국분무공학회지
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• 제3권3호
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• pp.33-41
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• 1998

In recently, a study on the lean combustion is investigated intensively, because it is expected that this method may decrease the harmful exhaust gas and improve fuel economy in gasoline engine. The problems of lean combustion system in gasoline engine are ignition difficulty, misfire and instability of combustion. The investigation on the optimization of fuel metering and the control of mixing gas flow may be critical to improve the performance of lean combustion. In the fuel injection gasoline engine, the formation of mixture influences strongly on the engine performance such that the importance of fuel metering system becomes apparent. First of all, a study on the fuel breakup characteristics of gasoline fuel injector was carried out in this paper. Fuel injectors are pintle and 4hole-2spray type. The purpose of this study is to clarify the atomization mechanism of spray injected into atomosphere field through electronic controlled-fuel injectors, and to analyze spray characteristics such as drop size distribution and mean drop diameter produced at fuel injector. In this paper, the spray development is observed by taking photograps using 80mm still-camera system, and drop sizes are measured by PMAS. From these experiment, spray pattern injected from gasoline fuel injectors was investigated clearly. Also, it was found that SMD and drop size distribution of injected fuel spray from gasoline fuel injectors.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.156-165
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• 2014

This paper is the first investigation on the effect of flow control methods on the part load performance in a spark ignition engine. For comparison of the methods, two control devices, port throttling and masking, were applied to a conventional engine without any design change of the intake port. Steady flow evaluation shows that steady flow rates per unit opening area and swirl ratio are very low compared with the port throttling and saturated from mid-stage valve lift, however, swirl increases slightly as the lift is higher in case of 1/4 masking control. In the part load performance, the effect of simple port throttling on lean misfire limit expansion is limited and insufficient; on the other hand a masking improves the limit considerably without any port modification for increasing swirl. Also the results show that the intake flow control improves the combustion with following two mechanisms: stratification induced by the combination of the flow pattern and the fuel injection timing attribute to ignition ability and the intensified flow ensure fast burn. In addition fuel consumption reduces under the flow controls and the reduction rate is different according to the operation conditions and control methods. At the Stoichiometric and/or low speed and low load the throttling method is more advantageous; however vice versa at lean and high load condition. Finally, the throttling is more efficient for HC reduction than masking, on the other side the NOx emissions increase under the masking and decrease under the port throttling compared with conventional port scheme.

• 한국자동차공학회논문집
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• 제22권4호
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• pp.121-130
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• 2014

This paper is the second investigation on the effects of intake flow control methods on the part load performance in a spark ignition engine. In the previous work, two control methods, port throttling and masking, were compared with respect to lean misfire limit, fuel consumption and emissions. In this work, the effects of these two methods on EGR characteristics were studied and simultaneously the differences between EGR and lean combustion as a dilution method were investigated. The results show that EGR limit is expanded up to 23% and 3 ~ 5% improvement in the fuel consumption are achieved around 8 ~ 13% rates by the flow controls comparing with 10% limit and 1.5% reduction around 3% rate of non-control case. The masking method is more effective on the limit expansion than throttling as like as lean misfire limit; however there is no substantial difference in fuel consumptions improvement regardless the control methods except high load condition. Also it is observed that there exist critical EGR rates around which the combustion performance and NOx formation change remarkably and these rates generally coincide with optimum rates for the fuel consumption. In addition, dilution with fresh air is much more advantageous than that of the exhaust gas from the view point of dilution limit and fuel consumption, while utilization of the exhaust gas is more effective on NOx reduction in spite of considerably small dilution compared with the use of fresh air. Finally, the improvement of fuel consumption by massive EGR is highly dependent on the EGR limit at which the engine runs stably, therefore the stratified combustion technique might be a best solution for this purpose.