Kinetics modeling of shock-induced ignition in low-dilution CH4/O2 mixtures at high pressures and intermediate temperatures
Kinetics modeling of shock-induced ignition in low-dilution CH4/O2 mixtures at high pressures and intermediate temperatures
复制标题
DOI：
10.1016/s0010-2180(98)00111-4
复制
发表时间：
1999-04
影响因子：
4.4
通讯作者：
E. Petersen;D. Davidson;R. Hanson
中科院分区：
文献类型：
--
作者：
E. Petersen;D. Davidson;R. Hanson
进行了一项分析研究，以补充最近的高压激波管测量的CH 4/O2点火在高压（40-260大气压），低稀释水平（燃料加氧化剂≥30%），中间温度（1040-1500 K），和当量比高达6。一个38种，190反应动力学模型，气体研究所的GRI-Mech 1.2机制的基础上，开发了使用额外的反应，甲烷氧化在较低的温度下是重要的。详细的模型计算同意与测量的点火延迟时间，并重现在较高的压力和较低的温度下的数据中看到的加速点火趋势。虽然扩展的机制提供了一个很大的改善，相对于原始模型在本研究的大部分条件下，进一步的改进仍然需要在最高的CH 4浓度和最低的温度。灵敏度和物种通量分析被用来确定的主要反应和动力学途径的条件下研究。在一般情况下，涉及HO 2，CH 3 O2，和H2 O2的反应在这项工作的条件下，相对于以前的研究，在较低的压力和较高的温度增加了重要性。在1400 K和100 atm的压力下，主要的点火促进剂是CH 3 + O 2 = O + CH 3 O和HO 2 + CH 3 = OH + CH 3 O。甲基重组乙烷是一个主要的终止反应，是CH 3自由基的主要汇。在1100 K，100 atm下，主要的支链反应为CH_3 O_2 + CH_3 = CH_3 O + CH_3 O和H_2 O_2 + M = OH + OH + M。这两个反应增强了H和OH自由基的形成，解释了在较低温度下的加速点火延迟时间特性（1100 K时的活化能为19.0 kcal/mol，1400 K时为32.7 kcal/mol）。文献综述表明，一些测量存在的许多最有影响力的速率系数，这表明需要在这一领域进行进一步的研究。本文代表了第一步，了解在激波管实验的极端条件下的甲烷点火和氧化动力学。
An analytical study was conducted to supplement recent high-pressure shock tube measurements of CH4/O2ignition at elevated pressures (40–260 atm), low dilution levels (fuel plus oxidizer ≥30%), intermediate temperatures (1040–1500 K), and equivalence ratios as high as 6. A 38-species, 190-reaction kinetics model, based on the Gas Research Institute’s GRI-Mech 1.2 mechanism, was developed using additional reactions that are important in methane oxidation at lower temperatures. The detailed-model calculations agree well with the measured ignition delay times and reproduce the accelerated ignition trends seen in the data at higher pressures and lower temperatures. Although the expanded mechanism provides a large improvement relative to the original model over most of the conditions of this study, further improvement is still required at the highest CH4concentrations and lowest temperatures. Sensitivity and species flux analyses were used to identify the primary reactions and kinetics pathways for the conditions studied. In general, reactions involving HO2, CH3O2, and H2O2have increased importance at the conditions of this work relative to previous studies at lower pressures and higher temperatures. At a temperature of 1400 K and pressure of 100 atm, the primary ignition promoters are CH3+ O2= O + CH3O and HO2+ CH3= OH + CH3O. Methyl recombination to ethane is a primary termination reaction and is the major sink for CH3radicals. At 1100 K, 100 atm, the dominant chain-branching reactions become CH3O2+ CH3= CH3O + CH3O and H2O2+ M = OH + OH + M. These two reactions enhance the formation of H and OH radicals, explaining the accelerated ignition delay time characteristics at lower temperatures (19.0 kcal/mol activation energy at 1100 K versus 32.7 kcal/mol at 1400 K). A literature review indicated few measurements exist for many of the most influential rate coefficients, suggesting the need for further study in this area. This paper represents a first step toward understanding the kinetics of CH4ignition and oxidation at the extreme conditions of the shock tube experiments.