Abstract Methanol is a promising fuel for spark ignition engines because of its high octane number, high octane sensitivity, high heat of vaporization and high laminar flame speed. To further boost the efficiency of methanol engines, the use of waste heat for driving fuel reforming was considered. This study explores the possibility of the reformed-exhaust gas recirculation (R-EGR) concept for increased efficiency of methanol engines. A simple Otto cycle calculation and a more detailed gas dynamic engine simulation are used to evaluate that potential. Both methodologies point to an enhancement in engine efficiency with fuel reforming compared to conventional EGR but not as much as the increase in lower heating value of the reforming product would suggest. A gas dynamic engine simulation shows a shortening of the flame development period and the combustion duration in line with the expected behavior with the hydrogen-rich reformer product gas. However, the heat loss increases with the presence of hydrogen in the reactants. The improvement of brake thermal efficiency is mainly attributed to the reduction of pumping work. The R-EGR concept is also evaluated for ethanol and iso-octane. As the reforming fraction increases, the efficiency of ethanol and iso-octane fueled engines rises faster than for the methanol engines due to a higher enhancement of exergy in their reforming products. At high reforming fractions, the efficiency of the ethanol engine becomes higher than with methanol. However, if the impact of optimal compression ratio for different fuels are considered, the methanol engine is able to produce a higher efficiency than the ethanol engine.

中文翻译：

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探索重整废气再循环 (R-EGR) 提高甲醇燃料 SI 发动机效率的潜力

摘要 甲醇具有高辛烷值、高辛烷敏感性、高汽化热和高层流火焰速度，是一种很有前途的火花点火发动机燃料。为了进一步提高甲醇发动机的效率，考虑利用余热驱动燃料重整。本研究探讨了重整废气再循环 (R-EGR) 概念提高甲醇发动机效率的可能性。使用简单的奥托循环计算和更详细的气体动力发动机模拟来评估这种潜力。与传统 EGR 相比，这两种方法都表明通过燃料重整提高发动机效率，但不如重整产品低热值的增加所暗示的那么多。气体动力发动机模拟显示火焰发展期和燃烧持续时间的缩短与富氢重整器产物气体的预期行为一致。然而，热损失随着反应物中氢气的存在而增加。制动热效率的提高主要归功于泵送功的减少。还针对乙醇和异辛烷评估了 R-EGR 概念。随着重整分数的增加，乙醇和异辛烷燃料发动机的效率比甲醇发动机提高得更快，因为它们的重整产品的火用增强程度更高。在高重整馏分下，乙醇发动机的效率高于甲醇发动机。但是，如果考虑不同燃料的最佳压缩比的影响，