• International Journal of Automotive Technology
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• v.8 no.3
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• pp.289-298
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• 2007

A nonlinear dynamic simulation model from cranking to idle speed is developed to optimize the cold start process of a diesel engine. Physically-based first order nonlinear differential equations and some algebraic equations describing engine dynamics and starter motor dynamics are used to model the performance of cold starting process which is very complex and involves many components including the cold start aiding method. These equations are solved using numerical schemes to describe the starting process of a diesel engine and to study the effects of cold starting parameters. The validity of this model is examined by a cold start test at $-20^{\circ}C$. Using the developed model the effects of the important starting variables on the cold starting processes were investigated. This model can be served as a tool for designing computer aided control systems that improve cold start performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.22-30
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• 2003

Engine-out HC emissions were investigated during cold and hot start. The tests were conducted according to engine cooling temperatures which were controlled by simulated coolant temperatures of cold and hot start, on a 1.5L, 4-cylinder, 16 valve, multipoint-port-fuel-injection gasoline engine. Real time engine-out HC emissions were measured at a exhaust port and cylinder head using Fast Response Flame Ionization Detector(FRFID). Unburned hydrocarbons emitted at the cold coolant temperature were much higher than those of the hot coolant temperatures. And the main source of the high HC emission was confirmed as misfire at cold coolant temperature. In addition, the effect of intake valve timing on engine-out HC emissions was investigated. The results obtained indicate that optimized intake phasing provides the potential for start-up engine-out HC emissions reduction.

• International Journal of Automotive Technology
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• v.7 no.7
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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.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.66-72
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• 2008

Fuel reforming technology for the fuel cell vehicles could be adopted 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 paper, syngas was feed to 2.0 liter gasoline engine during the cold start and early state of idle condition. Not only cold start HC emission but also $NO_x$ emission could be dramatically reduced due to the fact that syngas has no HC and has nitrogen up to 50% as components. Exhaust gas temperature was lower than that of gasoline feeding condition. Delayed ignition timing, however, resulted in increased exhaust gas temperature approximated to gasoline condition. It is supposed that the usage of syngas in the gasoline internal combustion engine is an effective solution to meet the future strict emission regulations by the reduction of cold start THC and $NO_x$ emissions.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.1
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• pp.32-39
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• 2000

To optimize the cold start process of a 4-stroke, 8 cylinder Diesel engine, a dynamic simulation model from cranking to idle speed is developed. Physically-based first order starter motor dynamics are used to model the performance of starting process which is very complex. These equations are solved using numerical schemes(Petzold-Gear BDF method) to describe the starting process of diesel engine and to study the effects of starting parameters. The validity of this model is examined by start test. This model can be served as a tool for computer aided control systems design to improve cold improve cold start performance.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.585-590
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• 2005

The effects of spark timing and exhaust valve timing change on exhaust gas temperature during cold start period of an SI engine are studied through engine bench tests. The exhaust gas temperature increases when the spark timing or valve timing are retarded individually, due to late combustion or slow flame speed. Therefore, exhaust gas temperature shows a large increase when the two timings are retarded simultaneously. However, it is considered that combustion stability during cold start deteriorated under these retarded conditions. To increase exhaust gas temperature for fast warmup of catalysts while maintaining combustion stability, an optimal condition for spark and valve timing retard should be applied for the cold start period.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.6
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• pp.628-633
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• 2012

It was found that the pure hydrogen-air pre-mixture was self-ignited at a high compression ratio without any assisting method in room temperature, thus refuting the preconception that compression ignition of hydrogen engine was impossible. Therefore, in order to analyze the correlation of compression ignition condition at cold start with hydrogen HCCI engine clearly, the possibility of compression igniting compression ratio is investigated with the change of equivalence ratio and engine speed, experimentally. As the results, it is confirmed that the possibility of compression-igniting compression ratio at cold start was decreased by increasing equivalence ratio due to decreasing auto-ignition temperature. In addition, it is grasped that the possibility of compression-igniting compression ratio at cold start is decreased around 14.9% by increasing engine speed at same supply energy.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.67-74
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• 2001

A synchronized secondaty air injection method has been developed to hydrocarbon emission by injecting secondary air intermittently into exhaust port. The method has been tested in a single cylinder spark-ignition engine operating at cold-steady / cold-start conditions. Effects of air injection timing, intake pressure and engine air-fuel ratio have been investigated at cold-steady condition. Also, hydrocarbon emission and exhaust gas temperature with catalytic conberter are compared with a continuous SAI method and base condition at cold-start condition. Resules show that hydrocarbon reduction rate and exhaust gas temperature are sensitive to the timing of synchronized SAI. At cold-steady condition, HC emission is minimum at engine air-fuel ratio of 10. At cold-start condition, the accumulated hydrocarbon emission during the first 120 s decreases about 56% and 22% with the synchronized and continuous SAI, respectively, compared to that of base condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.384-389
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• 2005

Experimental study of variation of exhaust gas temperature was carried out with the changes of spark timing and exhaust valve timing during the cold start operation of an SI engine. To investigate the effects of these variables on combustion stability, cylinder pressure and exhaust gas temperature were measured and analyzed. Experimental results showed that exhaust gas temperature increased when spark and exhaust valve timings were retarded from the baseline cases. However, combustion stability during cold start deteriorated under the retarded conditions. To increase exhaust gas temperature for fast warmup of catalysts while maintaining combustion stability, an optimal condition for spark and valve timing retard should be appied for the cold start period.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.101-108
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• 2011

On cold start operation of an SI engine, a catalyst shows poor performance before it reaches activation temperature. Therefore, fast warmup of the catalyst is very crucial to reduce harmful emissions. In this study, an appropriate control strategy is investigated to increase exhaust gas temperature through changes of spark timing. Combustion stability is also considered at the same time. Exhaust gas temperature and pressure of combustion chamber are measured to investigate the effects of spark timings on cold start and idle performance. Experiments showed that retarded spark timing promotes the combustion at the end of expansion stroke and increases exhaust gas temperature during cold start.