• 에너지공학
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• 제24권3호
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• pp.55-60
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• 2015

Recent engine development has focused mainly on the improvement of engine efficiency and output emissions. The improvements in efficiency are being made by friction reduction, combustion improvement and thermodynamic cycle modification. Computer simulation has been developed to predict the performance of a spark ignition engine. The effects of various cylinder pressure, heat release, flame temperature, unburned gas temperature, flame properties, laminar burning velocity, turbulence burning velocity, etc. were simulated. The simulation and analysis show several meaningful results. The objective of the present study is to develop a combustion model for a spark ignition engine running with isooctane as a fuel and predicting its behavior.

• 에너지공학
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• 제18권3호
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• pp.156-162
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• 2009

내연기관의 연소현상을 연구하는 연구자들에게 엔진 내부의 압력값은 연소과정을 이해 할 수 있는 좋은 데이터가 된다. 본 논문에서는 압력값을 이용하여 스파크 점화기관의 무부하에서의 사이클 연소 변동의 중요한 원인이 무엇인가를 규명한다. 또한 실험기관의 연소실에서 채취한 압력 데이터는 사이클 변동의 연소 해석의 기초 데이터와 연소율 해석 등의 데이터분석을 하는데 사용되었다. 연소변수의 입력변수로써 연료, 공기, 잔류량, 등등이 사이클 변동을 결정하는데 사용되었다.

• 오토저널
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• 제5권2호
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• pp.41-47
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• 1983

The analysis shows that the variation of maximum pressure of the cycle, rate of hear release, rate of mass burned, and combustion delay are influenced by the inlet air humidity in the spark-ignition engine. The quantitative combustion delay can be obtained from the rate of mass burned. Also, the variation of time loss and effective compression ratio with the change of inlet air humidity are dominated by the development of rate of heat release.

• Journal of Mechanical Science and Technology
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• 제15권1호
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• pp.81-87
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• 2001

Cyclic variability limits the range of operating conditions of spark ignition engines, especially under lean and highly diluted operation conditions. The cyclic combustion variations can be characterized by pressure parameters, combustion related parameters, and flame-front related parameters. The coefficient of variation (COV) in indicated mean effective pressure (IMEP) defines the cyclic variability in indicated work per cycle.

• 오토저널
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• 제6권2호
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• pp.47-54
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• 1984

The predictions of the mean effective pressure and the exhaust emission of NOx in hydrogen fueled spark ignition engine were studied. And the predictions were compared to the experimental results of D.B. Kittelson and H.S.Homan. The modeling was based on Otto cycle and the prediction of NOx was performed by extended Zeldovich mechanism. The differences between predictions and experimental results were 20 - 30% in the mean effective pressure and 10 - 20% in the concentration of NOx where the equivalence ratio .phi. was 0.6 - 0.8.

• 오토저널
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• 제7권1호
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• pp.24-34
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• 1985

The study of unsteady gas exchange processes in the inlet and exhaust systems of the single-cylinder 4-stroke cycle spark ignition engine is presented in this paper. The generalized method of characteristics including friction, heat transfer, change of flow area and entropy gradients was used for solving the equations defining the gas exchange process. The path line calculation was also conducted to allow for calculation of the gas composition and entropy change along the path lines, and of the variable specific heat due to the change of temperature and composition. As the result of the simulation, the properties at each point in the inlet and exhaust pipe, pressure and temperature in the cylinder, and charging efficiency were obtained. Pumping loss and residual gas fraction were also computed. The effect of engine speed, exhaust and inlet pipe length on the pumping loss and charging efficiency were studied showing that the results were in agreement with what has been known from experiments.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.37-44
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• 1998

Lean burn combustion is an important concept for improving the fuel consumption and exhaust emissions. However, the lean burning is associated with increased cycle-to-cycle combustion variations due to the ignition instabilities and redu- ced flame propagation rates. Engine stability under lean mixture conditions could be improved by increasing flame speed through enhanced flow characteristics and by securing ignitability with improvement of ignition systems. The effects of flow motion and ignition characteristics on the combustion performances were investigated in a 4-valve SI engine. Flow motions of tumble-swirl were varied with a swirl control valve attached at the inlet ports, while ignition energy and its distribution were controlled in a high -frequency ignition system by changing spark duration and spark frequency. The improvement of lean burn performance by the optimum flow motion and ignition characteristics is discussed.

• 한국자동차공학회논문집
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• 제8권6호
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• pp.1-8
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• 2000

A new method of knock detection in SI engines, using a change of ion concentration in the combustion chamber, was developed. In order to measure in-cylinder ionization current, ionization probes were installed at spark plug and cylinder head of production engine. It was found that the electric current generated by ionized gas in core burned gas region of knocking cycle is between 2 and 10 times larger than that of normal cycle, because the burned gas temperature which is the dominant parameter of a change of ion concentration increases. However, a change of ionization current in boundary region of burned gas is relatively weak. Hence a change of ion concentration in core burned gas region can be used for knock detection.

• 오토저널
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• 제5권1호
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• pp.79-88
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• 1983

A prediction of emission concentrations was made by calculating chemical equilibrium on the basis of an indicated pressure diagram in spark ignition engine using methanol as a fuel. A prediction according to Otto cycle was also made and for carbon dioxide, carbon monoxide and nitric oxide, emission test was performed using a conventional SI engine that was modified a little considering fuel characteristics. An investigation was made for those three cases-results from an indicated pressure diagram, Otto cycle and emission test. A good agreement between the measured values and the predicted ones existed for carbon dioxide and carbon monoxide, but not for nitric oxide. And good results existed for the other emission concentrations.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.58-71
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• 1996

A model which calculates the hydrocarbon emissions from spark ignition engines is presented The model contains the formation of HC emissions due to both crevices around piston ring top land and oil films on the cylinder wall. The model also considers in-cylinder oxidation and exhaust port oxidation of desorbed HC from crevices and oil films after combustion process. The HC emissions model utilizes the results of SI engine cycle simulation. The model predicts well the trends of HC emissions from the engines when varying engine parameters.