Reaction mechanisms of alkyloxiranes for combustion modeling
Reaction mechanisms of alkyloxiranes for combustion modeling
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DOI：
10.1016/j.combustflame.2023.112753
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发表时间：
2023-04-04
影响因子：
4.4
通讯作者：
Rotavera, Brandon
中科院分区：
文献类型：
--
作者：
Dewey, Nicholas S.;Rotavera, Brandon
环醚是由碳中心氢过氧取代基（QOOH）的单分子反应形成的中间体，其是低温链支化的中心。由于环醚是QOOH的异构体特定代理，因此需要描述消耗机制的化学反应的详细处方以进行准确的燃烧建模。然而，在化学动力学机理的发展中最常见的方法是使用一组简化的基本步骤，其不包括环醚自由基的形成和随后的反应，这产生了机理截断误差的来源。因此，环醚的模型预测和实验物种分布之间的定量差异是普遍存在的，并且跨越一系列烃，如正丁烷、正戊烷、正己烷、环己烷、己烯异构体和己醛。为了明确环醚消耗机理对燃烧模型的影响程度，以正丁烷氧化生成的环醚为例，研究了环醚燃烧过程的化学动力学特征.详细的子机制开发使用反应机理发生器（RMG）的乙基环氧乙烷和2，3-二甲基环氧乙烷，形成从单分子分解的β-QOOH自由基在正丁烷燃烧。这些子机理描述了两种环醚的消耗反应，包括OH引发的H-提取、O2-加成、ROO异构化等反应，并与NUIGMech1.1机理相结合，考察了模型对物种分布和点火延迟时间的预测，结果表明，模型预测与实验物种分布的一致性更好，同时也影响了点火预测.敏感性分析表明，OH引发的H-提取率是决定环醚的物种分布的温度依赖性的关键，这可以作为在引发步骤OH +正丁烷-> H2O + 1-丁基/2-丁基的分支馏分的重要性的指标。此外，从正丁烷酮过氧化氢形成的通量增加后，添加的子机制，作为确定的生产率进行分析OH和点火延迟时间simulation.The结果进行了相关的影响，本文表明，详细的子机制和准确的H-提取率从环醚是必要的高保真度的化学动力学预测燃烧建模。需要继续细化详细的反应机制，以便产生准确的燃烧模型，作为应用于详细机制或子机制以进行后续整合的机制简化技术的起点。需要这种技术，使反应流的建模，在实际条件下，将计算流体动力学。(c)第2023章燃烧研究所爱思唯尔公司出版All rights reserved.
Cyclic ethers are intermediates formed from unimolecular reaction of carbon-centered hydroperoxy-substituted radicals (QOOH), which are central to low-temperature chain-branching. Because cyclic ethers are isomer-specific proxies for QOOH, detailed prescription of chemical reactions describing the consump-tion mechanisms is required for accurate combustion modeling. However, the most common approach in the development of chemical kinetics mechanisms is to use a simplified set of elementary steps that ne-glect the formation and subsequent reaction of cyclic ether radicals, which creates a source of mechanism truncation error. As a consequence, quantitative discrepancies between model predictions and experimen-tal species profiles of cyclic ethers are ubiquitous and span a range of hydrocarbons such as n-butane, n -pentane, n-hexane, cyclohexane, hexene isomers, and hexanal. Moreover, uncertainties in species profile predictions of cyclic ethers translate directly to uncertainty in ignition predictions.For the explicit purpose of determining the extent to which cyclic ether consumption mechanisms affect combustion modeling, the present work examines the chemical kinetics underpinning such dis-crepancies using, as a representative case, a subset of cyclic ethers produced from n-butane oxidation. Detailed sub-mechanisms are developed using Reaction Mechanism Generator (RMG) for ethyloxirane and 2,3-dimethyloxirane, which form from unimolecular decomposition of beta-QOOH radicals during n-butane combustion. The sub-mechanisms prescribe consumption reactions for both cyclic ethers, including OH-initiated H-abstraction, O 2-addition, ROO isomerization, among other reactions, and were integrated with the NUIGMech1.1 mechanism to examine model predictions of species profiles and ignition delay times.Inclusion of the sub-mechanisms led to closer consistency between model predictions and experi-mental species profiles and also affected ignition predictions. Sensitivity analysis shows that rates of OH-initiated H-abstraction are critical for determining temperature dependence of species profiles of cyclic ethers, which may serve as an indicator for the importance of branching fractions in the initiation step OH + n-butane -> H2O + 1-butyl/2-butyl. Moreover, flux towards ketohydroperoxide formation from n -butane increased upon addition of the sub-mechanisms, as determined by rate-of-production analyses conducted on OH and related impact on ignition delay time simulations.The results herein demonstrate that detailed sub-mechanisms and accurate H-abstraction rates from cyclic ethers are necessary for high-fidelity predictions of chemical kinetics for combustion modeling. Continued refinement of detailed reaction mechanisms is required in order to produce accurate mod-els for combustion that serve as a starting point for mechanism reduction techniques applied either to detailed mechanisms or to sub-mechanisms for consequent integration. Such techniques are required to enable modeling of reactive flows that incorporate computational fluid dynamics at practical conditions.(c) 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.