Acetaldehyde reactivity at engine-relevant conditions: An experimental and kinetic modeling study

IF 5.2 2区 工程技术 Q2 ENERGY & FUELS
Jesus Caravaca-Vilchez, Malte Döntgen, Karl Alexander Heufer
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引用次数: 0

Abstract

Understanding the combustion chemistry of acetaldehyde, a carcinogenic by-product formed during the low-temperature oxidation of various hydrocarbons, is essential for reducing harmful emissions in engines. Previous acetaldehyde experimental works have largely focused on low-pressure conditions, with a few exceptions. Some studies report a clear negative temperature coefficient (NTC) behavior for acetaldehyde and highlight the need for further low-temperature, high-pressure experiments to fully characterize it. In this context, acetaldehyde ignition delay times were measured using a rapid compression machine and a shock tube over a wide range of conditions (580–1410 K, 10–40 bar, and equivalence ratios of 0.5–1.5), significantly extending the very limited IDT data available in the literature at 10 bar. At low temperatures, the most comprehensive kinetic models of acetaldehyde greatly underestimate its reactivity, even those that show reasonable performance for flow reactor species measurements from the literature in the same temperature regime. At high temperatures, model predictions were generally in better agreement with the measured data. To improve prediction accuracy, refinements were made within GalwayMech1.0 model, incorporating recently calculated thermochemistry from the literature and modified reaction rate parameters based on direct analogies and literature information. The resulting chemistry revealed that the acetyl peroxy radical is the primary driver of low-temperature reactivity at high pressures through a closed-loop fuel consumption pathway. Further adjustments in the peroxyl radicals chemistry, which is less relevant under low-pressure conditions, successfully separate first-stage and main ignition in the NTC region. At high temperatures, revised H-atom abstraction by Ḣ and O2 rates improved high-temperature predictions. Overall, the proposed model outperforms existing mechanisms over a wide range of conditions, but retains uncertainties in the formation of a few minor intermediates. This work highlights the importance of using high-pressure validation targets for comprehensive kinetic modeling and provides a solid foundation for future studies on acetaldehyde oxidation.
乙醛在发动机相关条件下的反应性:实验和动力学模型研究
乙醛是各种碳氢化合物在低温氧化过程中形成的一种致癌副产物,了解乙醛的燃烧化学性质对减少发动机的有害排放至关重要。以前的乙醛实验工作主要集中在低压条件下,只有少数例外。一些研究报告了乙醛明显的负温度系数(NTC)行为,并强调需要进一步的低温高压实验来充分表征它。在这种情况下,使用快速压缩机和激波管在广泛的条件下(580-1410 K, 10 - 40 bar, 0.5-1.5的等效比)测量乙醛点火延迟时间,显着扩展了文献中非常有限的IDT数据,可用于10 bar。在低温下,最全面的乙醛动力学模型大大低估了它的反应性,即使是那些在相同温度下从文献中显示出流动反应器物种测量的合理性能的模型。在高温下,模式预测通常更符合实测数据。为了提高预测精度,对GalwayMech1.0模型进行了改进,结合了最近从文献中计算的热化学和基于直接类比和文献信息的修正反应速率参数。结果表明,乙酰过氧自由基是通过闭环燃料消耗途径在高压下进行低温反应的主要驱动因素。在低压条件下不太相关的过氧基化学进一步调整,成功地分离了NTC区域的一级和主点火。在高温下,通过Ḣ和O2速率修正的h原子提取改进了高温预测。总的来说,提出的模型在广泛的条件下优于现有的机制,但在一些次要中间产物的形成中保留了不确定性。这项工作强调了使用高压验证目标进行综合动力学建模的重要性,并为乙醛氧化的未来研究提供了坚实的基础。
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来源期刊
Proceedings of the Combustion Institute
Proceedings of the Combustion Institute 工程技术-工程:化工
CiteScore
7.00
自引率
0.00%
发文量
420
审稿时长
3.0 months
期刊介绍: The Proceedings of the Combustion Institute contains forefront contributions in fundamentals and applications of combustion science. For more than 50 years, the Combustion Institute has served as the peak international society for dissemination of scientific and technical research in the combustion field. In addition to author submissions, the Proceedings of the Combustion Institute includes the Institute''s prestigious invited strategic and topical reviews that represent indispensable resources for emergent research in the field. All papers are subjected to rigorous peer review. Research papers and invited topical reviews; Reaction Kinetics; Soot, PAH, and other large molecules; Diagnostics; Laminar Flames; Turbulent Flames; Heterogeneous Combustion; Spray and Droplet Combustion; Detonations, Explosions & Supersonic Combustion; Fire Research; Stationary Combustion Systems; IC Engine and Gas Turbine Combustion; New Technology Concepts The electronic version of Proceedings of the Combustion Institute contains supplemental material such as reaction mechanisms, illustrating movies, and other data.
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