This work presents an experimental and numerical study of extinction properties of 2,5-dimethylfuran (DMF) and 2-methylfuran (MF) in counterflow diffusion flames at atmospheric pressure. The impact of addition of isooctane to the fuels is presented with two degrees of blends (25:75 and 50:50). The analysis was carried out for different levels of fuel loading ranging from 0.10 to 0.24 (volumetric) with the rest of the component being N₂ as a carrier gas. Extinction limits are observed to increase with an increase in fuel loading, and the resistance to extinction follows the order MF > isooctane > DMF. Numerical predictions using the Tianjin mechanism are within 10% of the measurements for MF cases, while the Galway mechanism tends to underpredict at higher fuel loading conditions. For DMF flames, both the mechanisms perform relatively well at X_F ≤ 0.14; however, they underpredict as the fuel loading is increased. Addition of isooctane to DMF led to an increase in the extinction limits at low fuel loading conditions, but the impact of blending diminished at higher fuel loading conditions. On the other hand, addition of isooctane had a minimum impact on MF flame’s extinction limit at low fuel loading conditions, while it led to a reduction in the resistance to extinction at higher fuel loadings. Numerical simulations by a mechanism proposed for the isooctane-DMF-MF blend predict similar effects of blending, however, consistently tend to underpredict at higher fuel loading conditions. Quantitative reaction path diagrams show that the H-abstraction step is the dominant fuel consumption route for near-extinction MF and DMF flames. With an increase in fuel loading, the role of C₅H₅ in the H-abstraction process increases in DMF/air flames. Reaction sensitivity analysis shows an increase in the importance of C₅H₅ kinetics in X_F = 0.24 DMF flames as compared to X_F = 0.14 along with the ring-opening step converting DMF to 3,4-hexadiene-2-one. In MF/air flames, the degree of change in sensitivities with fuel loading was found to be significantly low as compared to the DMF/air flames. Finally, reaction rate analysis was carried out to reveal that the slower consumption of MF causes the underprediction of the extinction strain rate by the Galway mechanism as compared to the Tianjin mechanism.

中文翻译：

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2-甲基呋喃，2,5-二甲基呋喃和异辛烷二元混合物扩散火焰熄灭的实验和动力学模型

这项工作提供了在大气压力下2,5-二甲基呋喃（DMF）和2-甲基呋喃（MF）在逆流扩散火焰中的消光特性的实验和数值研究。两种混合度（25:75和50:50）显示了向燃料中添加异辛烷的影响。进行了从0.10到0.24（体积）的不同燃料负载水平的分析，其余成分为N ₂作为载气。观察到消光极限随着燃料负荷的增加而增加，并且消光阻力遵循MF>异辛烷> DMF的顺序。使用天津机制的数值预测在MF情况下的测量值在10％以内，而高威机制在较高的燃料负载条件下往往预测不足。对于DMF火焰，两种机制在X _F下的性能都相对较好≤0.14；但是，随着燃料负荷的增加，它们会低估。在低燃料负荷条件下，向DMF中添加异辛烷导致消光极限的增加，但在较高燃料负荷条件下，混合的影响减小了。另一方面，在低燃料负荷条件下，异辛烷的添加对MF火焰的熄灭极限影响最小，而在较高燃料负荷下，耐熄火性降低。提出的针对异辛烷-DMF-MF共混物的机理的数值模拟预测了相似的共混效果，但是，在较高的燃料负载条件下，始终会发生预测不足的情况。定量反应路径图显示，H吸收步骤是接近灭绝的MF和DMF火焰的主要燃料消耗途径。随着燃料负荷的增加，C的作用H吸收过程中的₅ H ₅在DMF /空气火焰中增加。反应敏感性分析表明，与X _F = 0.14相比，X _F = 0.24 DMF火焰中C ₅ H ₅动力学的重要性增加，同时还有将DMF转化为3,4-己二烯-2-酮的开环步骤。在MF /空气火焰中，与DMF /空气火焰相比，发现随着燃料负载的敏感性变化程度明显较低。最后，进行了反应速率分析，结果表明，与天津机理相比，戈尔韦机理导致的MF消耗较慢会导致对灭绝应变速率的预测不足。