KINETIC MECHANISM, STRUCTURE AND PROPERTIES OF PREMIXED FLAMES IN HYDROGEN-OXYGEN-NITROGEN MIXTURES
KINETIC MECHANISM, STRUCTURE AND PROPERTIES OF PREMIXED FLAMES IN HYDROGEN-OXYGEN-NITROGEN MIXTURES
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DOI：
10.1098/rsta.1979.0045
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发表时间：
1979-01-01
期刊：
影响因子：
5
通讯作者：
DIXONLEWIS, G
中科院分区：
文献类型：
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作者：
DIXONLEWIS, G
Dixon-Lewis， Goldsworthy和Greenberg （1.975a）描述的用于计算合适火焰中详细温度和成分分布的复合通量方法已应用于模拟许多富燃料和贫燃料的氢-氧-氮火焰系统的特性。模拟中采用Day， Dixon-Lewis & Thompson（1972）提出的反应机理，并将其扩展为包括所有的逆反应，同时采用了假设的反应速率和输运参数集。然后将计算的剖面与已发表的火焰测量结果进行比较，涵盖了广泛的实验条件，以便迭代地达到最佳，自一致的速率参数集，该参数集还充分考虑了来自火焰以外来源的可用基本反应速率数据。在这部分研究中考虑的火焰性质是(a)富燃料和贫燃料火焰中的自由基复合曲线，以及(b)几种低温、慢燃、富燃料火焰的主要反应区的燃烧速度和性质。本文表4给出了满足所有约束条件的三组速率参数，它们只是在细节上有所不同，分别为集1、集2和集3。Kaskan （1958b）对贫氢体系中自由基重组的测量使用了羟基自由基的（0,0）波段紫外吸收来测量其浓度。测量结果的解释也与其他方法的剩余火焰测量结果一致，另外允许确定与过渡相关的振荡器强度。发现了一个波段振荡器强度为00 - 9.5 x 10-4。建立反应速率参数后，利用其中一组参数（表9）计算氢-空气预混火焰整个组成范围的期望性能。在这些情况下，以及在已经总结的计算中，必须结合复合通量法使用部分平衡或动力学准稳态假设。反应的部分平衡假设可用于计算H， OH， O和o2的浓度，其中只需要火焰复合区域的浓度分布。在完全火焰性质的计算中，必须使用准稳态假设来将O、OH和ho2的浓度与H（富火焰配方）的浓度或H、O和ho2的浓度与OH（贫火焰配方）的浓度联系起来。随后的研究表明，准稳态假设并不完全适用于火焰中的氧原子。然而，用完全不同的方法对几种火焰进行计算，即不涉及任何准稳态假设的隐式有限差分解，得到了与原计算基本一致的结果。因此，偏离准稳态对复合通量法计算的火焰特性没有显著影响。从完整的火焰计算中得出的火焰结构的一般模式是在火焰较热的区域由链支反应产生自由基，而主要的放热反应发生在较低的温度下。在热释放区之前，只有一个非常小的预热区，在那里加热纯粹通过热传导发生。这种行为不同于火焰的行为。
The composite flux method described by Dixon-Lewis, Goldsworthy & Greenberg (1.975a)for the computation of detailed temperature and composition profiles in suitable flames has been applied to the simulation of the properties of a number of fuel-rich and fuel-lean hydrogen-oxygen-nitrogen flame systems. The reaction mechanism proposed by Day, Dixon-Lewis & Thompson (1972), extended to include all the reverse reactions, has been used in the simulation, together with assumed sets of reaction rate and transport parameters. The computed profiles have then been compared with published measurements in flames, covering a wide range of experimental conditions, in order to arrive iteratively at an optimum, self-consistent set of rate parameters which also takes full account of the available elementary reaction rate data from sources other than flames. The flame properties considered in this part of the investigation were (a) radical recombination profiles in both fuel-rich and fuel-lean flames, and (b) the burning velocities and properties of the main reaction zones of several low temperature, slow burning, fuel-rich flames. Three sets of rate parameters which satisfy all the constraints, and which differ only in detail, are given as sets 1, 2 and 3 in table 4 of the paper. Measurements by Kaskan (1958b) of radical recombination in the hydrogen-lean systems have used the (0, 0) band ultraviolet absorption of the hydroxyl radical in order to measure its concentration. The interpretation of the measurements so as also to be consistent with the remaining flame measurements by other methods additionally allows a determination of the oscillator strength associated with the transition. A band oscillator strengthsf00— 9.5 x 10-4was found. Following the establishment of the reaction rate parameters, one set of these (table 9) was used to calculate the expected properties of the whole composition range of hydrogen-air premixed flames. In these cases, as well as in the calculations already summarized, either partial equilibrium or kinetic quasi-steady state assumptions must be used in conjunction with the composite flux method. Partial equilibrium assumptions on the reactionsmay be employed to relate the concentrations of H, OH, O and O2in calculations where only the concentration profiles in the recombination regions of the flames are required. In the calculation of complete flame properties, quasi-steady state assumptions must be used to relate the concentrations either of O, OH and HO2with that of H (rich flame formulation), or of H, O and HO2with that of OH (lean flame formulation). Subsequent investigation showed that the quasi-steady state assumptions were not completely valid for oxygen atoms everywhere in the flames. Nevertheless, further calculations on several flames by the completely different approach of implicit finite difference solution of the time-dependent flame equations, which does not involve any quasi-steady state assumptions, led to results essentially identical with the original computations. The departures from the quasi-steady state do not therefore significantly affect the flame properties computed by the composite flux method. The general pattern of flame structure which emerges from the complete flame calculations is one in which radicals are produced by chain branching reactions in the hotter regions of the flames, while the major heat releasing reactions occur at lower temperatures. Ahead of the heat release zone there is only a very small preheat zone where heating occurs purely by thermal conduction. This behaviour is different from that of flame …