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首页> 外文学位 >Determination of elementary rate constants by fitting detailed reaction mechanisms: Application to intermediate-temperature hydrocarbon kinetics.
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Determination of elementary rate constants by fitting detailed reaction mechanisms: Application to intermediate-temperature hydrocarbon kinetics.

机译：通过拟合详细的反应机理确定基本速率常数：在中温烃动力学中的应用。

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Experimental elementary rate constant determinations are vital for the construction of reaction mechanisms and the verification of theoretical rate predictions. It is often difficult to obtain direct rate measurements, however, and the best determinations often come from fitting a detailed reaction mechanism to experimental data. In this work, techniques for assessing the mechanistic dependence of rate constants determined in this manner were developed. The techniques were used to design and evaluate flow reactor experiments for the determination of rate constants important in hydrocarbon combustion.; First, local, first-order sensitivity coefficients were developed for rate constants determined by a least-squares fit to flow reactor data. These coefficients give the sensitivity of the determined rate constants to the remaining model parameters and experimental data. With uncertainty estimates for the model rate constants and experimental data the uncertainty in the proposed rate constant determinations could be estimated. Such estimates were used for experimental design, where these uncertainties were minimized through adjustment of the experimental conditions in a series of simulated flow reactor experiments.; The local, first-order technique could also be used for error estimates once the experiments were completed. However, given the large parameter uncertainties and strong couplings typical of kinetic mechanisms, a globally valid technique was desirable. An importance-sampled Monte Carlo technique was developed to determine global probability distributions and regressions for the fit results.; Flow reactor experiments were designed to determine rate constants for the reactions of methyl radicals with HO2 and O2 and of formaldehyde with HO2. These experiments were performed in a variable pressure flow reactor and new rate constant values were determined. The local technique was used to examine the mechanistic dependence of the results. Rigorous error bounds were developed and the limitations of the local technique were examined using the Monte Carlo technique. The new determinations gave a considerable reduction in uncertainty over the previous literature values.; In addition, a system for in situ far-UV absorption spectrometry was developed to measure additional species and aid in rate measurements. This system was used in initial work toward rate constant determinations for the reaction of vinyl radicals with O2.
机译：实验性基本速率常数测定对于构建反应机理和验证理论速率预测至关重要。然而，通常很难获得直接的速率测量值，而最佳的确定通常来自将详细的反应机理与实验数据相匹配的结果。在这项工作中，开发了评估以此方式确定的速率常数的机械依赖性的技术。该技术用于设计和评估流动反应器实验，以确定对碳氢化合物燃烧很重要的速率常数。首先，针对速率常数开发了局部一阶灵敏度系数，该系数由与流动反应器数据的最小二乘拟合确定。这些系数使确定的速率常数对其余模型参数和实验数据具有敏感性。利用模型速率常数和实验数据的不确定性估计，可以估计提议的速率常数确定中的不确定性。这些估计用于实验设计，其中通过调整一系列模拟流动反应器实验中的实验条件，将这些不确定性降至最低。实验完成后，本地一阶技术也可以用于误差估计。但是，考虑到动力学机制中典型的参数不确定性大和强耦合的问题，需要一种全局有效的技术。开发了重要性抽样的蒙特卡洛技术，以确定拟合结果的整体概率分布和回归。设计流动反应器实验以确定甲基与HO 2 和O 2 的反应速率常数，以及甲醛与HO 2 的反应速率常数。这些实验在变压流动反应器中进行，并确定了新的速率常数值。使用本地技术检查结果的机械依赖性。开发了严格的误差范围，并使用蒙特卡洛技术检查了局部技术的局限性。新的测定结果使不确定性大大降低，低于先前的文献值。此外，开发了用于“原位” /“原位” 远紫外吸收光谱的系统，以测量其他物种并帮助进行速率测量。该系统最初用于速率常数测定，用于乙烯基自由基与O 2 的反应。

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