湍流预混对冲火焰结构及熄火特性试验研究

Experimental Studies on Structure and Extinction Characteristics of Turbulent Counterflowing Premixed Flame

利用激光层析技术和数字图像处理技术对对冲方式下湍流预混火焰的结构及熄火特性进行了试验研究。采用 PIV方法测量了冷态对冲面附近的速度场 ,获得了速度应变率作为衡量流场对锋面燃烧影响的参数。在不同射流工况配置下 (Reynolds数 ,全局应变率 ,燃料的化学混合当量 ,不对称动量 ) ,观察到随着湍流对冲强度的提高 ,在高度皱褶的火焰锋面上存在非连续突触和空洞 ,这是局部熄火的表现 ,这些局部熄火点影响的扩展会导致火焰的整体熄火。此观点通过局部火焰锋面曲率的概率统计分析得到支持。另外 ,获得的在火焰熄火的极限条件 ,对实际燃烧器的设计有指导意义。

By the laser tomography technology and the digital image processing technique,the experimental studies on the structure and extinction characteristics of turbulent counterflowing premixed flame were carried out.The velocity aspects near the counterflowing interface were measured by PIV technology in cold condition and the strain rates of tangent velocity were acquired to describe the influence of the gradient of velocity on combustion.Using the extracted boundaries of flame,some discontinuous cusps and holes on the wrinkled boundaries were found under various experimental conditions,such as Reynolds number bulk stretch,equivalence ratio and the ratio of counterflowing momentum,and this was thought to predict the extinction in local region.The expansion of this occurrence will result in the global extinction of flame.This viewpoint was supported by the statistic analysis of boundary curvature.Furthermore,the relation between different parameters in a critical state will give some directive significance to the design of practical burners.