• 한국자동차공학회논문집
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• 제24권3호
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• pp.358-364
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• 2016

The combustion and exhaust emission characteristics in a spark ignition (SI) engine with various test fuels (bioethanol - gasoline blends) and air-fuel ratio were investigated in this research. To investigate the influence of the excess air ratio and ethanol blends on the combustion characteristics such as the cylinder pressure, rate of heat release (ROHR), and fuel consumption rate were analyzed. In addition, the reduction effects of exhaust emissions such as carbon monoxide (CO), unburned hydrocarbon (HC), and oxides of nitrogen (NOx) were compared with those of neat gasoline fuel under the various excess-air ratios. The results showed that the peak combustion pressures and the ROHR of bioethanol fuel cases were slightly higher than those of gasoline fuel at all test ranges and fuel ratio. As compared with gasoline fuel (G100) at each given excess air ratio, BSFC of bio-ethanol was increased. The CO, HC, NOx emissions of bio-ethanol blends were lower than those of gasoline fuel under overall experimental conditions.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.409-412
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• 2008

This paper presents the effects of excess air factors(0.84${\sim}$0.90) and opened throttle area ratios(AR=0.15${\sim}$0.25) on the emission and performance of a small spark-ignition gasoline engine. The engine used in this paper was a single cylinder, diaphragm carburetor, two-stroke, air-cooled 26cc engine for brush cutter. The rpm, torque, fuel consumption and CO emission were measured under the four different excess air factors and three different opened area ratios conditions on the engine loads respectively. The results showed that the rpm was decreased and torque was increased at increasing load, the maximum power and minimum fuel consumption could be obtained critical rpm on each throttle opened area ratios and brake specific fuel consumption was decreased 13${\sim}$17%, CO emissions was decreased 21${\sim}$38% at excess air factor 0.90 than 0.84.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.28-35
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• 1999

In this study, investigation of transient knock characteristics in a spark-ignition engine has been carried out. The universal knock threshold values were found by a DFDD method and a NSDBP method which is a non-dimensional version of the SDBP method. Also modified NSDBP method could be used for transient knock detection. In a commercial ECU , spark timing was retarded from the steady -state spark timing during rapid throttle opening to avoid uncomfortable feeling and knock. Knock usually occurred just after the start of rapid throttle opening when spark timing was set, as values for the steady state condition. We found that air/fuel ratio deeply involved with the knock during transient condition. Due to the difference of initial heat release rate, knock occurred more easily at rich air/fuel ratio than at lean air/fuel ratio.

• 한국정밀공학회지
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• 제19권7호
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• pp.80-87
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• 2002

Liquefied petroleum gas (LPG) is used in spark ignition (SI) engines. Fuel injection rate of an injector is affected by fuel temperature and pressure in LPG liquid injection systems for either a multi-point-injection (MPI) or a direct injection (DI) engine. Even fuel injection conditions are varied, the air-fuel ratio should be accurately controlled to reduce exhaust emissions. In this study, a correction factor fur the fuel injection rate of an injector is derived from density ratio and pressure difference ratio. A compensation method of injected fuel amount is proposed for a fuel injection control system. The experimental results for the LPG liquid injection system in a SI engine show that this system works well fur a full range of engine speed and load condition, and the air-fuel ratio is accurately controlled by the proposed correction factor.

• 한국자동차공학회논문집
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• 제19권5호
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• pp.35-44
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• 2011

In a spark ignition engine, a variable valve lift (VVL) system has been developed for high fuel efficiency and low power loss. However, changes in valve lift cause deviations of cylinder air charge which lead to individual cylinder equivalence ratio maldistribution. In this study, in order to reduce the maldistribution, we propose individual cylinder equivalence ratio estimation and control algorithms. The estimation algorithm calculates the equivalence ratio of each cylinder by using a mathematical engine model which includes air charging, fuel film, exhaust gas, and universal exhaust gas oxygen sensor (UEGO) dynamics at various valve lifts. Based on the results of estimated equivalence ratio, the injection quantity of each cylinder is adjusted to control the individual cylinder equivalence ratio. Estimation and control performance are validated by engine experiments. Experimental results represented that the equivalence ratio maldistribution and variation are decreased by the proposed algorithms.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.437-444
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• 2007

This paper experimentally investigates the effects of oxygen-enriched air (OEA) on the running behaviors of an LPG SI engine during both start/warm-up (SW) and hot idling (HI) stages. The experiments were performed on an air-cooled, single-cylinder, 4-stroke, LPG SI engine with an electronic fuel injection system and an electrically-heated oxygen sensor. OEA containing 23% and 25% oxygen (by volume) was supplied for the experiments. The throttle position was fixed at that of idle condition. A fueling strategy was used as following: the fuel injection pulse width (FIPW) in the first cycle of injection was set 5.05 ms, and 2.6 ms in the subsequent cycles till the achieving of closed-loop control. In closed-loop mode, the FIPW was adjusted by the ECU in terms of the oxygen sensor feedback. Instantaneous engine speed, cylinder pressure, engine-out time-resolved HC, CO and NOx emissions and excess air coefficient (EAC) were measured and compared to the intake air baseline (ambient air, 21% oxygen). The results show that during SW stage, with the increase in the oxygen concentration in the intake air, the EAC of the mixture is much closer to the stoichiometric one and more oxygen is made available for oxidation, which results in evidently-improved combustion. The ignition in the first firing cycle starts earlier and peak pressure and maximum heat release rate both notably increase. The maximum engine speed is elevated and HC and CO emissions are reduced considerably. The percent reductions in HC emissions are about 48% and 68% in CO emissions about 52% and 78%; with 23% and 25% OEA, respectively, compared to ambient air. During HI stage, with OEA, the fuel amount per cycle increases due to closed-loop control, the engine speed rises, and speed stability is improved. The HC emissions notably decrease: about 60% and 80% with 23% and 25% OEA, respectively, compared to ambient air. The CO emissions remain at the same low level as with ambient air. During both SW and HI stages, intake air oxygen enrichment causes the delay of spark timing and the increased NOx emissions.

• 한국자동차공학회논문집
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• 제18권1호
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• pp.23-30
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• 2010

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 results obtained from experiments have shown that specific fuel consumption has increased by increasing ethanol amount in the blend whereas decreased by the use of hydrogen-enriched gas. The combustion characteristics with hydrogen-enriched gaseous fuel from ethanol reforming are also examined.

• 한국가스학회지
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• 제27권3호
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• pp.52-58
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• 2023

지구 기상이변에 대해 탄소중립의 중요성이 대두됨에 따라 무탄소 연료인 수소의 에너지원으로서의 활용도 역시 증대되고 있다. 일반적으로 수소는 연료전지(FC, Fuel Cell)에 활용되고 있으나, 이는 연소를 기반으로 하는 내연기관(ICE, Internal Combustion Engine)에도 활용될 수 있다. 특히 연료전지만으로 수소 활용 및 인프라 확장이 어려운 때에 이미 생산 측면이나 공급 측면에서 인프라가 기 구축되어 있는 내연기관은 수소 에너지 저변 확대에 큰 도움을 줄 수 있다. 다만 수소를 연소기반으로 활용할 경우 고온에서 공기 중 질소가 산소와 반응하여 유해배기물질인 질소산화물(NOx, Nitrogen Oxides)이 생성될 수 있는 단점은 존재한다. 특히 냉간 (Cold Start) 운전 영역시 포함될 EURO-7 배기규제의 경우 워밍업(Warm-up) 과정에서 발생하는 배기배출물의 저감을 위한 노력도 필요하다. 따라서 본 연구에서는 2 L급 수소 직접분사방식 전기점화 (SI, Spark Ignition) 엔진을 활용하여 냉각수를 상온에서 88 ℃로 워밍업하는 과정에서 질소산화물 및 연료소모율의 변화 특성을 살펴보았다. 특히 수소는 기존의 가솔린, 천연가스, 액화석유가스(LPG, Liquified Petroleum Gas)와 달리 가연범위(Flammable range)가 넓기 때문에 공기과잉률(Excessive air ratio)을 희박하게 조절할 수 있다는 장점이 있다. 이에 본 연구에서는 워밍업하는 과정에 있어서 공기과잉률을 1.6/1.8/2.0으로 변화하여 그 결과를 분석하였다. 본 실험의 결과는 워밍업 시 공기과잉률이 희박해질수록 시간당 질소산화물의 배출이 적고, 열효율도 상대적으로 높으나 최종 온도까지 도달 시간이 길어짐에 따라 누적 배출량 및 연료소모율은 악화될 수도 있음을 시사한다.

• 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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.796-801
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• 2001

During cold operation period, fuel injection system directly contributes the unburned hydrocarbon formation in spark ignition engines. The relationship between injection parameters and HC emission behavior was investigated through a series of experiments. Spray behavior of port fuel injectors was characterized through a quantitative evaluation of mass concentration of liquid fuel by a patternator and PDA. 6-hole injector was found to produce finer spray than single hole one. Using a purpose-built test rig, the wall wetting fuel was measured, which was mostly affected by wall temperature. Varying coolant temperature($20{\sim}80^{\circ}C$), HC emissions were measured in a production engine. With respect to the different types of injectors, HC emission was also measured. In the 6-hole injector application, the engine produced less HC emission in low coolant temperature region. Though it produces much more amount of wetting fuel, it has the advantages of finer atomization quality. In high coolant temperature region, there was little effect between different types of injectors. The control schemes to reduce HC emissions during cold start could be suggested from the findings that the amount of fuel supply and HC emission could be reduced by utilizing fine spray and high intake wall temperature.