Asymptotic Analysis of Flame Structure with Real Chemistry

真实化学火焰结构的渐近分析

• 批准号: 8918527
• 负责人: Forman Williams
• 金额: $ 22.67万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-11-01 至 1992-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8918527&HistoricalAwards=false
• 关键词: Asymptotic; Analysis; Flame; Structure; Real

This research applies asymptotic methods, involving expansions for large and small values of parameters appearing in differential equations, to the analysis of structures of flames in real combustible mixtures. Through nondimensionalization of the conservation equations, large and small parameters are identified. These parameters involve activation energies leading to activation-energy asymptotics, magnitudes of reaction rates leading to Damkohler-number asymptotics, and ratios of reaction rates leading to rate- ratio asymptotics. Rate parameters for elementary steps are taken from the literature on reaction rate experiments. The identification of limiting values of the parameters simplifies the conservation equations and enables solutions to be obtained largely analytically without resort to numerical integration of the full set of conservation equations. The research will address structural differences between premixed flames and diffusion flames for hydrocarbon-oxygen-nitrogen systems for systems involving carbon monoxide, hydrogen and oxygen, as well as the intrinsic stability and influences of strain for these flames. Special attention will be paid to the derivation and application of useful reduced schemes for hydrogen-oxygen systems, for systems containing halogens, for higher hydrocarbons, and possibly also for methanol. The methods typically lead to formulas for the quantities of interest, such as burning velocities, and the formulas usually contain parameters determined by numerical integrations of two-point boundary-value problems for ordinary differential equations. Since these differential equations are much simpler than the starting differential equations, full parametric solutions are obtained, rather than solutions restricted to specific conditions. As a consequence, a better understanding of flame structure ensues, the essential aspects of the combustion processes are identified, and inessential complications that play no significant role are eliminated.

本研究应用渐近方法（涉及微分方程中出现的大值和小值参数的展开）来分析实际可燃混合物中的火焰结构。 通过守恒方程的无量纲化，可以识别大参数和小参数。这些参数涉及导致活化能渐近的活化能、导致达姆科勒数渐近的反应速率的大小以及导致速率比渐近的反应速率的比率。 基本步骤的速率参数取自反应速率实验的文献。 参数极限值的确定简化了守恒方程，并且能够在很大程度上通过分析获得解，而无需求助于全套守恒方程的数值积分。 该研究将解决涉及一氧化碳、氢气和氧气的系统的碳氢化合物-氧-氮系统的预混合火焰和扩散火焰之间的结构差异，以及这些火焰的内在稳定性和应变的影响。 将特别关注氢氧系统、含卤素系统、高级烃以及可能还有甲醇的有用简化方案的推导和应用。 这些方法通常会得出感兴趣的量（例如燃烧速度）的公式，并且这些公式通常包含由常微分方程的两点边值问题的数值积分确定的参数。 由于这些微分方程比起始微分方程简单得多，因此可以获得完整的参数解，而不是仅限于特定条件的解。 因此，可以更好地理解火焰结构，识别燃烧过程的基本方面，并消除不重要的复杂情况。