• International Journal of Automotive Technology
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• 제7권7호
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• pp.763-768
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• 2006

Emission reduction in the cold start period of SI engines is crucial to meet stringent emission regulations such as SULEV Emissoin reduction is the starting point of the study in the which the variable valve timing (VVT) technology may be one promising method to minimize cold start emissions while maintaining engine performance. This is because it is possible to change valve overlap and residual gas fraction during cold start and idle operations. Our previous study showed that spark timing is another important factor for reducing cold-start emissions since it affects warm-up time of close-coupled catalysts (CCC) by changing exhaust gas temperature. However, even though these factors may be favorable for reduction of emissions, they may deteriorate combustion stability in these operating conditions. This means that the two variables should be optimized for best exhaust emissions and engine stability. This study investigated the effects of valve and spark timings in idle performance such as combustion stability and exhaust emissions. Experiments showed that valve timings significantly affected engine stability and exhaust emissions, especially CO and $NO_x$, due to change in residual gas fraction within the combustion chamber. Spark timing also affects HC emissions and exhaust gas temperature. Yet it has no significant effects on combustion stability. A control strategy of proper valve timing and spark timing is suggested in order to achieve a reduction in exhaust emissions and a stable operation of the engine in a cold start and idle operation.

• 에너지공학
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• 제18권2호
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• pp.136-140
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• 2009

자동차 공회전은 운전자의 운전 만족도에 여러 영향을 미친다. 또한 보다 높은 연료 경제성의 요구가 고조됨에 따라, 자동차 생산자들은 계속적으로 보다 나은 운전조건의 혜택에 관심을 갖는다. 스파크 점화기관의 공회전에서 기관의 안정성은 연소변동에 의해 좌우되며, 기관의 안정성은 연료분사시기, 점화시기, 그리고 공기연료비 등의 요소들에 영향을 받게 된다. 본 연구에서는 공회전에서 연료분사시기, 점화시기 그리고 공기연료비 등에 따라, 연소의 안정성과 변동율에 미치는 영향을 조사하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.342-352
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• 2003

Idle NVH characteristics are one of the most important aspects among the vehicle performances. Vehicle developers are devoted to improve vehicle interior noise and steering wheel and seat vibrations. In order to improve the idle quality, noise and vibration transfer path should be carefully evaluated. Also, effects of various components related to the idle performance should be confirmed. A general procedure for improving the idle qualify is described in detail. The relationship among cylinder pressure characteristics, crankshaft rotational speed variation, and vehicle vibrations is also investigated. Influences of drive shaft, torque converter, air conditioning system, vehicle structure including engine mount system, and idle control parameters on the vehicle idle quality are studied. Weak points of typical vehicles on the idle qualify are identified. Some of improvement measures are proposed and verified.

• 한국연소학회지
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• 제11권4호
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• pp.14-21
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• 2006

In this study, syngas which is reformed from fossil fuel and has hydrogen as a major component, was added to a gasoline engine to improve combustion stability and exhaust emissions of idle state. Syngas fraction of the total supplied fuel varied to 0 %, 25 %, 50 % with various ignition timing and excess air ratio. Combustion stability, exhaust emissions, fuel consumption and exhaust gas temperature were measured to investigate the effects of syngas addition on idle performance. Results showed that syngas has ability to widely extend lean operation limit and ignition retard range with dramatical reduction of engine out emissions. It is supposed that the usage of syngas in the internal combustion engine is an effective solution to meet the future strict emission regulations.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.245-251
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• 2005

Recently, fuel reforming technology for the fuel cell vehicle has been applied to internal combustion engines, with various purpose. Syngas which is reformed from fossil fuel has hydrogen as a major component. It has better effort in combustion characteristics such as wide flammability and hig speed flame propagation. In this study, syngas was added to a gasoline engine for the improvement of combustion stability and exhaust emission in idle state. Combustion stability, exhaust emissions, fuel consumption and exhaust gas temperature were measured to investigate the effects of syngas addition on idle performance. Results showed that syngas has ability to extend lean operation limit and ignition retard range. with dramatical reduction of engine out emissions.

• 한국자동차공학회논문집
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• 제7권5호
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• pp.66-72
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• 1999

It is necessary to discuss lightening engine parts and reducing the friction of sliding parts to improve fuel consumption and combustion stability at idling condition. Lean best torque combustion which produce maximum power at a lean air-fuel ratio is effective for the reduction of exhaust gas emission and the improvement of fuel consumption. Accordingly, this study deals with the expansion of lean combustible limitation, the combustion stability and the reduction of idle speed through the analysis of combustion characteristics on the base of the control technique of precise air-fuel ratio because it does not need to maximum power at idling condition. The idle speed is increased proportional to ISC(Idle Speed Control) duty ratio. On the other hand the idle speed decreased by lean air-fuel ratio. The COV in engine speed is stable within maximum two percent up to 17.6 mixture ratio by the control of ISC duty ratio.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.259-266
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• 1998

In the SI engine, the improvement of combustion stability is important not only for the fuel consumption rate but also for the emission control at idling of engine. Thus the engine speed fluctuation at idle operation mainly comes from cyclic variation of combustion in the SI engine. In this syudy, the improvement of combustion stability for the SI engine at idle condition by the cooling water temperature, duty ratio of ISC, spark ignition timing as well as the reducement of the harmful exhaust gas emission was discussed.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.174-182
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• 2007

Fuel reforming technology for the fuel cell vehicles could be applied to internal combustion engine for the reduction of engine out emissions. Since syngas which is reformed from fossil fuel has hydrogen as a major component, it has abilities to enhance the combustion characteristics with wide flammability and high speed flame propagation. In this study, syngas was added to a gasoline engine to improve combustion stability and exhaust emissions of idle state. Syngas fraction is varied to 0%, 50%, 100% with various ignition timing and excess air ratio. Combustion stability, exhaust emissions, fuel consumption and exhaust gas temperature were measured to investigate the effects of syngas addition on idle performance. Results showed that syngas has ability to widely extend lean operation limit and ignition retard range with dramatical reduction of engine out emissions.

• 한국자동차공학회논문집
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• 제2권5호
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• pp.23-29
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• 1994

The design procedure for fuzzy logic controller depends on the expert's knowledge or trial and error. Moreover, it is very difficult to guarantee the stability and robustness of the system due to the linguistic expression of fuzzy control. However, fuzzy logic control has succeeded in many control problems that the conventional control theory has difficulties to deal with. As a result, this control theory is applied to the engine control system which a mathematical model is difficult. In this study, the fuzzy logic is applied to obtain the gain of PI control at idle speed control system, and a simple engine model is developed in order to perform simulation. Experimental results show that the response to reach the target engine speed at idle speed control system is improved by adopting the gain obtained with fuzzy logic.

• 대한기계학회논문집B
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• 제21권12호
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• pp.1647-1655
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• 1997

The cyclic variations can be characterized by the variations in different type of parameters. These parameters may be grouped into four main categories: pressure-related parameters, combustion-related parameters, flame front-related parameters, and exhaust gas-related parameters. One of the resultant effects of the cycle-by-cycle variation in the combustion process, which is the most important with regard to the engine performance characteristics, is the cycle-by-cycle variation in IMEP. This paper uses the repetitive discharge igniter, which can change the ignition energy easily, to study on idle stability in a spark ignition engine. From this device, the 6 number of spark and 0.20 ms spark interval, it is very available for the idle stability.