Chemical reactions in high-temperature combustion are reversible and reaction reversibility might have a great impact on fundamental combustion processes such as ignition and flame propagation. In this study, ignition and propagation of spherical flames with a reversible reaction are analyzed using the large-activation-energy asymptotic method. Analytical correlations are derived to describe the change of spherical flame propagation speed and flame temperature with flame radius. The reversibility parameter, fuel Lewis number, and ignition power are included in these correlations. These correlations can predict different flame regimes and transitions among the ignition kernel, flame ball, propagating spherical flame, and planar flame. Therefore, based on these correlations spherical flame propagation and initiation are then investigated with the emphasis on assessing the impact of reaction reversibility. It is found that similar to heat loss, reaction reversibility can greatly affect spherical flame propagation speed, Markstein length, flame ball radius, minimum ignition power, and critical ignition radius. Moreover, it is demonstrated that the influence of reaction reversibility depends on fuel Lewis number.
Ignition Spherical flame propagation Reversible reaction Markstein length Lewis number
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This work was supported by National Natural Science Foundation of China (Nos. 51322602 and 51136005), Doctoral Fund of Ministry of Education of China (No. 20120001110080), and State Key Laboratory of Engines at Tianjin University (No. K2012-02).