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Boundary layer flashback of non-swirling premixed flames: Mechanisms, fundamental research, and recent advances
Progress in Energy and Combustion Science ( IF 29.5 ) Pub Date : 2017-07-01 , DOI: 10.1016/j.pecs.2017.03.001
Alireza Kalantari , Vincent McDonell

Abstract Boundary layer flashback in premixed jet flames has been the subject of detailed experimental and numerical investigation since the 1940′s. The traditional approach for characterizing flashback has involved the critical velocity gradient concept, with higher values indicating a higher flashback propensity for a given situation. Recent studies in confined configurations have illustrated that a key assumption underlying the critical velocity gradient concept, namely a lack of interaction between the flame and the approaching flow, is fundamentally incorrect. However, for unconfined configurations, where this interaction is much less important, the critical velocity gradient concept is able to partially capture flashback characteristics. Historically, the critical velocity gradient concept predicts trends of flashback behavior in laminar configurations for a wide range of temperatures, pressures, and fuel compositions more consistently than in turbulent configurations. This is due in part to the fact that many laminar studies establish well behaved velocity conditions in the tube conveying the premixed reactants to the reaction zone. Yet many important practical systems are in the turbulent regime and cannot be approximated by a simplified analysis. Studies to date in either regime, while numerous, generally do not provide a comprehensive methodology for accounting for all parameters. Recent work has attempted to capture the effect of a large number of these parameters in the turbulent regime, with some emphasis on providing design tools that can be used to estimate flashback propensity in more general terms. These approaches have demonstrated reasonable performance for the limited data available at elevated temperature and pressure which are representative of important practical system such as lean premixed combustors for gas turbines. While progress has been made in the last few years relative to predicting flashback for practical systems with high Reynolds numbers, only limited data are available for developing and validating correlations. Open questions remain in terms of using detailed numerical simulations and complex reaction chemistry to predict flashback for unconfined flames. In addition, flame-wall interaction in terms of heat transfer, sensitivity to turbulence levels, the role of general velocity gradients (vs idealized fully developed flow), and the role of high pressure must be further evaluated.

中文翻译:

非旋转预混火焰的边界层闪回:机理、基础研究和最新进展

摘要 自 1940 年代以来,预混喷射火焰中的边界层回火一直是详细的实验和数值研究的主题。表征闪回的传统方法涉及临界速度梯度概念,值越高表示给定情况下的闪回倾向越高。最近对受限配置的研究表明,临界速度梯度概念背后的一个关键假设,即火焰和接近的流动之间缺乏相互作用,从根本上是不正确的。然而,对于这种相互作用不那么重要的无约束配置,临界速度梯度概念能够部分捕获闪回特性。从历史上看,临界速度梯度概念比湍流配置更一致地预测层流配置中的回火行为趋势,适用于广泛的温度、压力和燃料成分。这部分是由于许多层流研究在将预混反应物输送到反应区的管中建立了良好的速度条件。然而,许多重要的实际系统都处于湍流状态,无法通过简化分析来近似。迄今为止在这两种制度中的研究虽然数量众多,但通常没有提供用于说明所有参数的综合方法。最近的工作试图捕捉大量这些参数在湍流状态中的影响,一些重点是提供可用于以更一般的术语估计闪回倾向的设计工具。这些方法已经证明了在升高的温度和压力下可用的有限数据的合理性能,这些数据代表了重要的实际系统,例如用于燃气轮机的贫预混燃烧器。虽然过去几年在预测具有高雷诺数的实际系统的闪回方面取得了进展,但可用于开发和验证相关性的数据有限。在使用详细的数值模拟和复杂的反应化学来预测无侧限火焰的回火方面仍然存在悬而未决的问题。此外,在热传递方面的火焰-壁相互作用、对湍流水平的敏感性、
更新日期:2017-07-01
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