外二次旋流风对旋流煤粉燃烧及NO生成的影响

对旋流煤粉火焰在两种分级进风的情况下用PIV（particle image velocimetry）测量了燃烧室内的速度分布，研究了湍流拟序结构对旋流火焰的燃烧特性及NO排放的影响。燃烧室进口附近，当外二次风率较大时，其拟序结构沿横向的扩散较早，大量小颗粒被裹入涡结构中参加反应，因此中心区域温度较高;外二次风率较小时，一次风外侧的涡结构使得更多的大颗粒在惯性离心力作用下运动到了近壁区域，因此近壁区温度更高。在本文的实验范围内，保持其他条件不变，增加外二次旋流风，有利于剪切层纵向涡结构的形成，也有利于横向涡的形成，促进了小颗粒煤粒燃烧和大颗粒煤粒挥发分析出，从而促进NO的提前生成以及燃烧中间产物对NO的还原，最终减少NO的生成。

Effect of outer secondary air on swirling pulverized-coal combustion and NO formation

PIV technique（particle image velocimetry）is utilized to measure the instantaneous velocity fields in swirling pulverized coal nonpremixed combustion under different staged air injections. The influence of turbulent coherent structure on combustion characteristics and NO formation is studied.Near the inlet of the combustor，larger secondary air ratio leads to early spread of coherent structures and entrainment of small pulverized coal particles into these structures，therefore，the central gas temperature is higher;smaller secondary air ratio makes more big particles move to the vicinity of the wall under the effect of inertial centrifugal forces，resulting in higher gas temperature near wall.In this experiment，larger secondary air ratio contributes to the formation of longitudinal vortices in shear layers and transverse vortices in the field，combustion of small particles and volatilization of big particles，and initially enhances the NO formation，but subsequently stimulates the reaction of NO reduction by intermediate products，and finally slightly decreases the NO concentration.