In this study, the effect of external-exhaust-gas-recirculation (EGR) on anti-knock characteristics of ethanol reference fuels (ERFs) with research octane number (RON) 100 was analyzed by measuring the ignition delay of the simulated end gas from a representative spark ignition (SI) engine operation, i.e. ASTM RON test condition. An in-house SI engine model was used to derive temperature and pressure profiles of the end gas with and without external-EGR for various ERFs, and then the ignition delay was measured by using a rapid compression machine along the derived temperature-pressure paths. The effect of external-EGR on the ignition delay of the simulated end gas was divided into two effects affecting the auto-ignition behavior: composition effect and temperature effect, then each effect was evaluated separately. As a result, the composition effect by adding external-EGR was maximized when the fuel is ERF10. With a regression analysis, it was found that there is the correlation between the amount of composition effect and the amount of pre-heat release in the end gas during a flame propagation; therefore, it is understood that ERF10 shows the most sensitive composition effect due to its pre-heat release characteristic. On the other hand, ERF with higher ethanol content was more sensitive to temperature effect by external-EGR on the ignition delay. It is found out that the amount of temperature effect depends mainly on latent heat of fuel; therefore, high latent heat of ethanol in ERF leads to its being influenced more by temperature effect. Consequently, ERF10 has the highest external-EGR sensitivity in anti-knock behavior at RON test condition, and it is further discussed that the optimum ERF for external-EGR strategy could vary from ERF0 to ERF10 according to different engine operating conditions.

在这项研究中，通过测量模拟尾气的点火延迟，分析了外部废气再循环（EGR）对研究辛烷值（RON）为100的乙醇参考燃料（ERF）的抗爆震特性的影响。代表性的火花点火（SI）发动机操作，即ASTM RON测试条件。使用内部SI发动机模型来导出带有和不带有外部EGR的各种ERF的最终气体的温度和压力曲线，然后使用快速压缩机沿导出的温度-压力路径测量点火延迟。将外部EGR对模拟最终气体着火延迟的影响分为影响自燃行为的两种影响：成分影响和温度影响，然后分别评估每种影响。因此，当燃料为ERF10时，通过添加外部EGR的成分效果最大。通过回归分析发现，在火焰传播过程中，成分效应的量与终端气体中预热释放量之间存在相关性。因此，可以理解，ERF10由于其预热释放特性而显示出最敏感的成分效果。另一方面，乙醇含量较高的ERF对外部EGR对点火延迟的温度影响更敏感。结果发现，温度效应的大小主要取决于燃料的潜热。因此，ERF中乙醇的高潜热导致乙醇受温度效应的影响更大。因此，在RON测试条件下，ERF10在抗爆震性能方面具有最高的外部EGR灵敏度，