Abstract We study the variability in the ignition delay time, τign, of n-butanol due to uncertainty in the enthalpies and entropies of the fuel and fuel radicals. A stoichiometric mixture reacting adiabatically at constant volume is considered, over a range of initial temperatures (700–1000 K) and pressures (10–80 bar). We develop a thermodynamic class approach to account for the variability in the thermodynamic properties of species of interest, and to define associated uncertainty ranges. To gain insight into the impact of the variability of the thermodynamic properties of individual species, a brute force sensitivity analysis is first performed. The results show that large variations in τign are mainly due to perturbations in the enthalpies of six species belonging to two thermodynamic classes. A refined 1D analysis is then conducted of the uncertain enthalpies and entropies of these six species. In particular, a complex, nonmonotonic dependence of τign on species enthalpies is observed, highlighting potential limitations in extrapolating local sensitivity results. The 1D analysis also shows that uncertainties in species entropies have a weaker impact on the variability in τign than the species enthalpies. A global sensitivity analysis of the impact of thermodynamic class uncertainties is then performed, namely using surrogates constructed using an adaptive pseudo-spectral method. The results indicate that the variability of τign is dominated by uncertainties in the classes associated with peroxy and hydroperoxide radicals. Lastly, we perform a combined sensitivity analysis of uncertainty in kinetic rates and thermodynamic properties. In particular, the results indicate that uncertainties in thermodynamic properties can induce variabilities in ignition delay time that are as large as those associated with kinetic rate uncertainties.

中文翻译：

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正丁醇点火延迟时间对热力学等级和速率规则参数的全局敏感性分析

摘要 我们研究了由于燃料和燃料自由基的焓和熵的不确定性，正丁醇的点火延迟时间 τign 的变化。考虑在初始温度 (700–1000 K) 和压力 (10–80 bar) 范围内以恒定体积绝热反应的化学计量混合物。我们开发了一种热力学类方法来解释感兴趣物种的热力学特性的可变性，并定义相关的不确定性范围。为了深入了解单个物种的热力学特性的可变性的影响，首先进行了蛮力敏感性分析。结果表明，τign 的大变化主要是由于属于两个热力学类别的六个物种的焓的扰动。然后对这六个物种的不确定焓和熵进行精细的一维分析。特别是，观察到 τign 对物种焓的复杂、非单调依赖性，突出了外推局部敏感性结果的潜在局限性。一维分析还表明，与物种焓相比，物种熵的不确定性对 τign 的可变性的影响更小。然后对热力学类别不确定性的影响进行全局敏感性分析，即使用使用自适应伪谱方法构建的代理。结果表明，τign 的可变性主要由与过氧和氢过氧化物自由基相关的类别的不确定性决定。最后，我们对动力学速率和热力学性质的不确定性进行了综合敏感性分析。