Scaling of turbulent flame speed for expanding flames with Markstein diffusion considerations.
Scaling of turbulent flame speed for expanding flames with Markstein diffusion considerations.
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DOI：
10.1103/physreve.88.033005
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发表时间：
2012-03
期刊：
影响因子：
--
通讯作者：
Swetaprovo Chaudhuri;Fujia Wu;C. Law
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文献类型：
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作者：
Swetaprovo Chaudhuri;Fujia Wu;C. Law
本文通过对定压扩张湍流火焰的实验测量，阐明了平面层流火焰速度与Markstein长度的乘积Markstein扩散系数对湍流火焰速度及其标度的影响。给出了氢气、甲烷、乙烯、正丁烷和二甲醚与空气在近乎各向同性湍流中预混火焰在双室风扇搅拌容器中的湍流火焰传播数据。对于文中提出的每一种燃料-空气混合物和最近发表的利兹的异辛烷数据，归一化的燃料-空气混合物的湍流火焰速度数据近似遵循Re_(T，f){0.5}尺度，其平均半径是长度尺度，热扩散率是湍流雷诺数的输运性质。在给定的Re_(T，f)^}下，实验观察到归一化湍流火焰速度随Markstein数的增加而减小，这可以用Markstein扩散系数作为大波数火焰表面波动的主要耗散机制来解释。因此，通过用上述湍流雷诺数定义中的Markstein扩散系数代替热扩散系数，发现对于正Markstein数火焰，归一化湍流火焰速度可以用Re_(T，M){0.5}来刻度，而与燃料、当量比、压力和湍流强度无关。
In this paper we clarify the role of Markstein diffusivity, which is the product of the planar laminar flame speed and the Markstein length, on the turbulent flame speed and its scaling, based on experimental measurements on constant-pressure expanding turbulent flames. Turbulent flame propagation data are presented for premixed flames of mixtures of hydrogen, methane, ethylene, n-butane, and dimethyl ether with air, in near-isotropic turbulence in a dual-chamber, fan-stirred vessel. For each individual fuel-air mixture presented in this work and the recently published iso-octane data from Leeds, normalized turbulent flame speed data of individual fuel-air mixtures approximately follow a Re_{T,f}^{0.5} scaling, for which the average radius is the length scale and thermal diffusivity is the transport property of the turbulence Reynolds number. At a given Re_{T,f}^{}, it is experimentally observed that the normalized turbulent flame speed decreases with increasing Markstein number, which could be explained by considering Markstein diffusivity as the leading dissipation mechanism for the large wave number flame surface fluctuations. Consequently, by replacing thermal diffusivity with the Markstein diffusivity in the turbulence Reynolds number definition above, it is found that normalized turbulent flame speeds could be scaled by Re_{T,M}^{0.5} irrespective of the fuel, equivalence ratio, pressure, and turbulence intensity for positive Markstein number flames.