低NO_x自激振荡射流燃烧器

Low NO_x Self-excited Oscillating-jet Burners

流体射入特定结构的突扩腔体会发生整体低频振荡，这类射流称为自激振荡射流。射流振荡对近场和远场的湍流混合过程都具有重要影响。自激振荡射流能增强宏观上的大尺度搅动，但同时却减弱了微观上的小尺度混合。以此为基础开发的自激振荡射流燃烧器能在不增加火焰长度的情况下增加火焰体积，显著提高火焰辐射换热，降低火焰温度，降低热力型氮氧化物（NOx）的生成。在工业水泥回转窑及其他窑炉的应用中，长期的实践证明，该燃烧器与以往的多喷嘴燃烧器相比，降低40％-60％的NOx排放，并降低了5％-10％的单位产量燃料消耗。该文综述了射流振荡对湍流混合及火焰特性的影响，亦对这种燃烧器的局限性做了分析讨论，最后给出利用白激振荡射流现象进一步发展工业燃烧器的建议。

A small flow ejecting into a relatively large specific chamber can produce large-scale low-frequency oscillations, this jet is termed as a self-excited oscillating jet. The self-excited oscillation imposes a profound influence on turbulent mixing process： i.e., it not only enhances large-scale engulfment or entrainment but also simultaneously decreases the molecular mixing rate. Previous combustion experiments reveal that the self-excited oscillating jet burners always produce relatively larger flames with more soot, thus increasing flame radiation, decreasing flame temperature and resulting in low NOx emissions. Many installations of these burners at cement kilns have consistently delivered a reduction of 40%,-60% of NOx emissions and also less fuel consumption by 5%-10%, relative to the conventional multi-jet burners. This paper reviewed the influence of jet oscillation on turbulent mixing and flame performance, then discussed the limitations of the burners, and finally gave suggestions to their further development.