Smart control of hydrogen and methane lean combustion with environmental catalysis and high temperature air combustion

本文研究了甲烷-空气混合气在平面燃烧器上稀薄燃烧时的火焰形状和波动。在0.74<φ<1.00时形成平面火焰，在φ<0.74时形成蜂窝状火焰，其中φ是当量比。测量了预混火焰的亮度波动，得到了亮度波动的均方根值和功率谱密度。随着当量比的减小，亮度波动的RMS增加。这是因为热扩散效应在低当量比下具有不稳定的影响。功率谱密度具有尖峰，其频率对应于预混火焰的振荡频率，在低频区域出现1/f谱。我们得到的吸引子，关联维数和李雅普诺夫指数研究的预混火焰的波动特性。波动的特征强烈地依赖于当量比，即，预混火焰的内在不稳定性。结果表明，波动分析方法适用于火焰不稳定性的诊断，并通过改变混合气体流量，研究了波动的特征。流量对吸引子、关联维数和李雅普诺夫指数有很大的影响。因此，我们可以估计流量通过时间序列分析的混沌行为的预混火焰。

In this research we deal with the flame shape and fluctuation in the lean burn of methane-air mixtures on a flat burner. Planar flames are formed at 0.74<φ<1.00, and cellular flames are formed at φ<0.74, where φ is the equivalence ratio. The cell size becomes larger as the equivalence ratio becomes lower.We measure the fluctuation of brightness of premixed flames, and obtain the RMS and power spectrum density of the brightness fluctuation. With a decrease in the equivalence ratio, the RMS of the brightness fluctuation increases. This is because the diffusive-thermal effect has a destabilizing influence at low equivalence ratios. The power spectrum density has sharp peaks, whose frequency corresponds to the oscillation frequency of premixed flames, and the 1/f spectrum appears in low frequency range.In addition, we perform the time series analysis on the brightness fluctuation. We obtain the attractor, correlation dimension, and Lyapunov exponent to investigate the characteristics of the fluctuation of premixed flames. The characteristics of fluctuation depend strongly on the equivalence ratio, i.e., on the intrinsic instability of premixed flames. The results suggest that the fluctuation analysis is applicable to the diagnostics of flame instability.Moreover, the flow rate of gas mixtures is changed, and the characteristics of fluctuation are studied. The flow rate has a great influence on the attractor, correlation dimension, and Lyapunov exponent. Thus, we can estimate the flow rate through the time series analysis in chaotic behavior of premixed flames.