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首页> 外文期刊>Combustion and Flame >Experimental assessment of various methods of determination of laminar flame speed in experiments with expanding spherical flames with positive Markstein lengths
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Experimental assessment of various methods of determination of laminar flame speed in experiments with expanding spherical flames with positive Markstein lengths

机译：在Markstein长度为正的膨胀球形火焰实验中，各种测定层流火焰速度的方法的实验评估

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Experimental data obtained from lean propane-air expanding spherical laminar flames at pressures of 1 and 0.5 atm, with all other things being equal, are analyzed using four different extrapolation equations available in the literature and a unified processing algorithm developed in the present work. For comparison, experimental data obtained recently by Zamashchikov et al. (2014) from a very rich hydrogen-air flame are also processed using the same algorithm. Dependencies of (i) rms differences between measured and calculated flame radii, (ii) laminar flame speeds, and (iii) Markstein lengths on the boundaries of the analyzed range of flame radii are studied in order to (i) investigate the sensitivity of processing results to these boundaries, (ii) determine the proper radius range for each extrapolation equation, and (iii) to find an equation that fits the measured data in the widest radius range. For the lean propane-air mixture under room conditions, which is associated with a relatively weak effect of flame stretching on the flame kernel growth, all four equations yield approximately equal flame speeds, but the associated Markstein lengths are different. Moreover, the flame speeds and Markstein lengths are sensitive to the processed range of flame radii and the same measured curve can be fitted with the same equation using substantially different pairs of Markstein length and flame speed. Due to these two sources of errors, choice of a proper processing method does not seem to be a critical issue when analyzing weakly non-linear dependencies of flame radius on time. To the contrary, for two other flames, which are associated with stronger stretch effects, the two aforementioned sources of errors play a minor role, i.e. flame speeds and Markstein lengths are weakly sensitive to the processed range of flame radii provided that it is properly selected, while the rms differences between measured and calculated flame radii are sufficiently sensitive to variations in Markstein length and flame speed. Accordingly, a proper choice of a processing method is of paramount importance when analyzing substantially non-linear dependencies of flame radius on time. Results of present work indicate that the phenomenological Markstein equation, which is linear with respect to flame curvature, fits the experimental data well in a wider range when compared to three other equations. Because, close results were also obtained using a non-linear equation derived theoretically by Kelley et al. (2012), the latter equation is worth being highlighted from the basic standpoint. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：在其他条件相同的情况下，从贫丙烷-空气膨胀的球状层流火焰在1和0.5 atm压力下获得的实验数据进行了分析，使用文献中提供的四个不同的外推方程和本工作中开发的统一处理算法进行了分析。为了比较，Zamashchikov等人最近获得的实验数据。 （2014年）也使用相同的算法处理了非常丰富的氢空气火焰。 （i）测量和计算的火焰半径之间的均方根差，（ii）层流火焰速度和（iii）在火焰半径分析范围边界上的马克斯坦长度的依赖性，以便（i）研究加工的敏感性得出这些边界的结果，（ii）为每个外推方程确定合适的半径范围，以及（iii）找到一个适合最宽半径范围内的测量数据的方程。对于在室温下稀薄的丙烷-空气混合物，这与火焰拉伸对火焰核生长的影响相对较弱有关，所有四个方程式得出的火焰速度近似相等，但相关的马克斯坦长度不同。而且，火焰速度和马克斯坦长度对火焰半径的处理范围很敏感，并且可以使用实质上不同的马克斯坦长度和火焰速度对来对相同的测量曲线拟合相同的方程。由于这两个误差源，在分析火焰半径与时间的弱非线性相关性时，选择合适的处理方法似乎不是关键问题。相反，对于另外两个与更强的拉伸效果相关的火焰，上述两个误差源起着较小的作用，即，只要适当选择，火焰速度和马克斯坦长度对火焰半径的加工范围就不太敏感。 ，而测量和计算的火焰半径之间的均方根差对Markstein长度和火焰速度的变化足够敏感。因此，当分析火焰半径与时间的基本非线性相关性时，正确选择处理方法至关重要。目前的工作结果表明，与其他三个方程相比，现象学上的马克斯坦方程与火焰曲率呈线性关系，在更宽的范围内很好地拟合了实验数据。因为，使用Kelley等人理论上推导的非线性方程也可以获得接近的结果。 （2012年），从基本观点出发，值得强调后者。 （C）2015年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

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