不同当量比下氢气体积分数对甲烷-氢混合气预混火焰燃烧不稳定性的影响

在可调振幅的正弦波声场作用下，以甲烷-氢混合气预混钝体火焰为实验对象，通过火焰传递函数表征整个燃烧系统的燃烧不稳定性特征，借助CH基自发荧光图像描述火焰锋面运动及演化过程，研究了在声激励下不同当量比（0.8、1.0、1.2）下氢气体积分数的变化（0、10%、20%）对火焰燃烧不稳定的影响。结果表明: 对于当量比为0.8和1.0的预混火焰，氢气的加入使得火焰传递函数幅值增大，热释放波动变大，整体火焰的不稳定性增强；对于当量比为1.2的富燃预混火焰，随着氢气体积分数的增加，火焰传递函数幅值先减小后增加，火焰稳定性较强。 

Effect of hydrogen volume fraction on combustion instability of hydrogen/methane premixed flame under different equivalence rates

The combustion instability of premixed bluff-body flame under acoustic excitation at different equivalence rates (0.8, 1.0, 1.2) and hydrogen volume fraction (0, 10%, 20%) was analyzed. The combustion instability could be captured by the flame transfer functions and the flame front distribution could be shown by CH chemiluminescence measurement. Results showed that the combustion characteristics were very sensitive to the fraction of hydrogen in the fuel mixture. When equivalence rates were 0.8 and 1.0, the amplitude of flame transfer functions and heat release fluctuations increased with hydrogen concentration. And with the increase of hydrogen concentration, the combustion instability of premixed flame became stronger. When hydrogen volume fraction increased at equivalence rate of 1.2, the amplitude of flame transfer functions firstly reduced then increased.