相干结构涡中NO_x的初生形态

Formation of initial stage NO_x in the coherent structure vortex

首次应用六线涡量探针测量了大型电站锅炉四角燃烧器射流形成的涡量场 ,发现了射流向火侧相干结构性质的涡 ,采用兰金复合涡 (RankineVortex)旋涡模型描述了该剪切大涡的尺度及其旋转速度 ,该剪切大涡的涡核半径r0 为 2 5mm ,流体微团作刚体式旋转的角速度为 - 1.5 6× 10 5r min ,应用粒子在相干结构中运动的研究成果以及燃料型NOx 的生成和破坏机理 ,分析了NOx 在相干结构涡中的初生形态 ,射流向火侧剪切大涡的结构里 ,在剪切大涡的边缘会形成富燃料区 ,当过量空气系数α <1时 ,燃料N会尽可能多地转化成挥发分N ,并且在还原性气氛条件下 ,燃料N转变为分子N2 ,由挥发分N生成的NOx 会大大减少 ;在剪切大涡的涡核内 ,是α>1的贫燃料区 ,设法降低过量空气系数α ,可以抑制NOx

The IFA300 constant temperature hot wire anemometer and the six-sensor hot-wire probe are used to measure the vorticity field in the burner zone of tangentially fired furnace. The coherent structure vortex is discovered on the fire-facing side of the jets. The big shear vortex on the fire-facing side of the four burner jets is described by Rankine vortex. The scale of vortex and the rotating velocity in the prototype furnace are calculated based on Rankine vortex model. The radius of vortex core (r_0) of the biggest shear vortex is 25 millimeter. The rotating velocity of tiny fluid element by means of rigid body rotation in the furnace is -1.56×10 5 rotations per minute. The formation of initial stage NO_x in the coherent structure vortex is analyzed by the research results of particle moving in the coherent structure and by the fuel NO_x mechanism of production and depression. The rich fuel zone is formed in the edge of shear vortex and fuel nitrogen will be transformed volatile nitrogen as soon as possible when the coefficient (α) of excessive air is less than one. And also in the condition of reducing air, fuel nitrogen will be transformed molecule nitrogen so that the formation of initial stage NO_x will greatly decrease. The poor fuel zone is formed in the core of the big shear vortex while the coefficient (α) of excessive air is more than one. If the coefficient (α) of excessive air is decreased, the formation of initial stage NO_x will be depressed.