Experiment And Numerical Simulation For The Effects Of Gasoline Qualities On Engine Performance

Gasoline quality has an important role in the engine performance, especially the emissions characteristics. Exhaust emissions can be effectively controlled with clean gasoline. Many countries have performed research on gasoline quality based on the characteristics of their own automobile and oil industries, and enacted stringent gasoline specifications. The oil refinery is quite different from foreign countries and it is lack of the research on the relationships between gasoline qualities and emissions in China. Therefore, it is necessary to conduct relevant research and supply data and suggestions to Chinese or Beijing government for the stipulation of gasoline requirements.The typical international"Auto-Oil"programs and progress of relevant research on gasoline quality were investigated and analyzed, and the conclusions, research methods and the weakness in this research field were summarized. Based on the analysis, the main research contents and reasonable methods were proposed.The effects of octane number, olefins content, aromatics content, sulfur content and volatility on power output, fuel consumption and engine-out emissions were studied on two gasoline engines with different emissions level. Engine performance tests, rapid catalyst sulfur aging tests and simulated cold-start tests were conducted. Combustion characteristics were analyzed and were used to investigate the phenomenon and trends in the tests. The proposal of clean gasoline specifications to meet the 4th stage emissions standard in China was brought forward through detailed discussions on the results in this study and relevant results in previous research. Test results showed that too high octane number resulted in the prolonged combustion duration, high fuel consumption and emissions. Olefins resulted in the short combustion duration and low THC emissions. 1%v increment in olefins content resulted in 1% less THC emissions. Aromatics content had no significant effect on emissions and combustion process as it increased from 35%v to 45%v. Sulfur had little influence on catalyst initial activity. It had a great effect on catalyst aging performance. The aging light off temperature lifted significantly as sulfur content increased. Sulfur poisoning was somewhat reversible and the catalyst activity could be partially recovered through high temperature running. High volatility could improve the combustion process and reduce THC emissions during cold start. The effect of volatility on CO emissions was related to engines.Considering the multi-component characteristics of gasoline, three representative species and their fractions in the substituted gasoline model was determined by thermogravimetry analysis tests. The multi-component vaporization models for droplet and fuel film were developed, which can capture the differences of the vaporization between different gasoline components. Based on the developed vaporization models, the spray evaporation process of gasoline and the influence of gasoline volatility on mixture formation and combustion of an engine during cold start were numerically studied, which provided a theoretical explanation for understanding the effect of the gasoline quality on combustion and emissions.