湿空气非预混火焰回流区速度特性的实验

为了寻找特性速度对火焰结构的规律性影响,使用粒子图像速度仪(PIV)测量圆盘形钝体后甲烷/湿空气非预混火焰的回流区速度场,得到火焰的平均速度场分布.结果表明,在中心燃料未穿透回流区时,中心轴线上存在2个滞止点;与普通的燃烧火焰相比,湿空气燃烧2个滞止点之间的距离变短,最小无量纲速度偏大,其位置曲线具有3个明显的变化阶段,分别代表不同的燃烧状态;在不同的空气速度下,中心轴线上的最小速度及其所处位置都具有大致相同的函数关系,表明燃空速度比是控制燃烧火焰结构的一个重要参数.

Experimental Study on Velocity Characteristics of Recirculation Zone in Humid Air Non-premixed Flame

In order to examine the effect of flow field within the recirculation zone on flame structure,the characteristic velocity fields of methane/humid air flame in non-premixed combustion behind a disc bluff-body burner were experimentally studied by particle image velocimetry(PIV).The results show that two stagnation points exist on the centerline in the state of recirculation zone flame.However,the interval of the two stagnation points in humid air case shortens,and the minimal dimensionless velocity increases compared with the conventional non-humid combustion.In addition,the positional curves of the minimal velocities can be partitioned into three phases,representing three different flame patterns respectively.The analysis to axial minimal velocities on the centerline and their positions under different co-flow air(velocities) condition reveals that fuel-to-air velocity ratio is the crucial parameter to govern the humid air(combustion) flame.