微尺度预混合火焰结构和熄火特性研究

STRUCTURE AND EXTINCTION CHARACTERISTICS OF PREMIXED MICRO FLAMES

本文以空气中的无约束甲烷预混合火焰为对象,用实验和数值解析的方法研究了微尺度预混合火焰的火焰结构和熄火特性。实验测得不同尺寸下混合气当量比和喷出速度与熄火关系图,在不到理论当量比(φ>1)时,火焰已经熄灭,管径越小,极限混合气当量比φu越大。数值解析研究了d=0．3 mm无约束甲烷预混合火焰,在混合气当量比大于 1的富燃料燃烧条件下,空气中形成的预混合火焰结构是内层预混合火焰和外层扩散火焰,极限当量比约为1,解析结果再现了实验现象。

Structure and extinction characteristic of circular jet methane-air premixed micro-flames in room-temperature air are investigated experimentally and numerically. When the characteristic size reduces, it is easy to extinct, and the minimal equivalence ratio Фu increases, moreover, all the equivalence ratio should be more than 1（Ф 〉 1） in order to obtain the stable flames. When the equivalence ratio is lager （Ф = 10）, Calculation results show that, the flame structure is composed of two parts, the inside part is premixed flame and the outside part is diffusion flame. These calculation results give the reason why the premixed flame is stable at high equivalence ratio with smaller characteristic size in the experiment.