Abstract A PIV-based system has been set-up for the simultaneous measurement of the local propagation velocity and the flame stretch of laminar jet premixed flames. The contributions of the flame front curvature and the strain rate of the fresh gas flow to the flame stretch are separately discussed. Laminar jet flames of methane-air lean mixtures have been studied with a secondary flame in a coflow configuration to avoid blow-off. In weakly curved flame tips (low inlet gas velocity), these measurements confirm the prediction of linear velocity-stretch dependence and allow the indirect determination of the Markstein length and planar flame propagation velocity, by extrapolating the experimental results to the zero-stretch condition. In moderately curved flame tips (large inlet gas velocity), experiments show a faster than linear increase of the flame velocity with the stretch. The transition between these two regimes occurs suddenly when a threshold value of the inlet gas velocity is exceeded.

中文翻译：

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Markstein 关系有效性的实验限制

摘要 建立了一个基于 PIV 的系统，用于同时测量层流射流预混火焰的局部传播速度和火焰拉伸。分别讨论了火焰锋曲率和新鲜气流的应变率对火焰拉伸的贡献。已经研究了甲烷-空气稀薄混合物的层流喷射火焰，并在协流配置中使用二次火焰来避免吹散。在弱弯曲的火焰尖端（低入口气体速度）中，这些测量证实了线性速度-拉伸依赖性的预测，并允许通过将实验结果外推到零拉伸条件来间接确定 Markstein 长度和平面火焰传播速度。在适度弯曲的火焰尖端（入口气体速度大），实验表明，随着拉伸，火焰速度比线性增加更快。当超过入口气体速度的阈值时，这两种状态之间的转变会突然发生。