氢气部分预混火焰瞬态响应及脉冲不稳定性研究

Transient Response and Pulsating Instability in H_2/Air Partially Premixed Flames

本文基于详细化学反应机理和输运性质,对氢气/空气部分预混火焰瞬态响应及脉冲不稳定性进行了数值分析.研究发现预混火焰区存在脉冲不稳定现象,振荡过程可形成极限环,此时火焰强度更依赖于O_2浓度,而对当地温度不敏感;扩散火焰区由于受到预混火焰区传热、传质影响,扩散火焰出现受迫振荡现象。研究结果表明增大拉伸率及当量比会抑制脉冲不稳定现象的发生,其原因是扩散火焰和预混火焰之间距离减小,具有更高温度的扩散火焰向预混火焰区导热增强,后者火焰强度增大,从而减小了Zeldovich数,抑制了不稳定现象的发生。

The transient response and pulsating instability in H_2/air partially premixed flames were computationally studied using detailed transport and chemical reactions.The pulsating flame and it's limit cycle were observed in premixed flame zone.The flame intensity of this oscillating flame depends on the concentration of O_2,and is not sensitive to local temperature.The nonpremixed flame undergoes forced oscillation,which is due to the influences of mass and heat transfer from premixed flame zone.The result shows that the increases of strain rate and equivalence ratio suppress the pulsating instability,which is attributed to the decrease of distance between premixed and nonpremixed flame zone.Due to this,the heat conduction from nonpremixed flame zone to premixed flame zone,and thereby the premixed flame intensity are strengthened.Therefore the Zeldovich number decreases,and the pulsating instability is suppressed.