The Effect of Compression Ratio, Fuel Octane Rating, and Ethanol Content on Spark-Ignition Engine Efficiency

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• 作者：Thomas G. Leone ; James E. Anderson ; Richard S. Davis ; Asim Iqbal ; Ronald A. Reese ; II ; Michael H. Shelby ; William M. Studzinski
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：September 15, 2015
• 年：2015
• 卷：49
• 期：18
• 页码：10778-10789
• 全文大小：499K
• ISSN：1520-5851

文摘

Light-duty vehicles (LDVs) in the United States and elsewhere are required to meet increasingly challenging regulations on fuel economy and greenhouse gas (GHG) emissions as well as criteria pollutant emissions. New vehicle trends to improve efficiency include higher compression ratio, downsizing, turbocharging, downspeeding, and hybridization, each involving greater operation of spark-ignited (SI) engines under higher-load, knock-limited conditions. Higher octane ratings for regular-grade gasoline (with greater knock resistance) are an enabler for these technologies. This literature review discusses both fuel and engine factors affecting knock resistance and their contribution to higher engine efficiency and lower tailpipe CO₂ emissions. Increasing compression ratios for future SI engines would be the primary response to a significant increase in fuel octane ratings. Existing LDVs would see more advanced spark timing and more efficient combustion phasing. Higher ethanol content is one available option for increasing the octane ratings of gasoline and would provide additional engine efficiency benefits for part and full load operation. An empirical calculation method is provided that allows estimation of expected vehicle efficiency, volumetric fuel economy, and CO₂ emission benefits for future LDVs through higher compression ratios for different assumptions on fuel properties and engine types. Accurate 鈥渢ank-to-wheel鈥?estimates of this type are necessary for 鈥渨ell-to-wheel鈥?analyses of increased gasoline octane ratings in the context of light duty vehicle transportation.