湍流预混火焰熄灭特性的实验研究

摘要

Extinction of premixed turbulent methane/air flames was studied in a counterflow burner,and the effects of bulk and turbulent straining on the extinction limits were analysed. The experimental results show that the average jet velocity and bulk stretch rate at extinction increase as the equivalent ratio increases,indicating a significant influ-ence of the bulk straining on flame extinction. With the equivalent ratio increasing,the critical value of turbulent stretch rate and Karlovitz number,Ka,for flame extinction both increase. Although the observation is consistent with previous experiments,the present value ofKa is smaller than literature data for the same equivalent ratio due to the effect of bulk straining. Based on the experimental results,the mechanism of turbulent flame extinction was dis-cussed.%采用对冲火焰实验系统对贫燃料甲烷/空气湍流火焰发生熄灭的极限条件进行考察，分析了平均流场拉伸和湍流拉伸对火焰熄灭的影响。实验结果表明，随着甲烷/空气火焰当量比的增大，其熄灭时的射流平均速度以及平均拉伸率随之增大，说明平均拉伸对火焰熄灭极限有显著影响。当量比增大时，湍流极限拉伸率和Karlovitz拉伸参数Ka 均增大，这与前人的实验结果一致，但由于平均拉伸的影响，当量比一定时，Ka 的数值比文献数据偏小。根据实验数据，文中对湍流预混火焰熄灭的机制进行了探讨。