旋流燃烧器扩口角度对其气固两相流场的影响

Effects of Cone Angle on Gas-Solid Two-phase Flow in the Swirl Burner

采用激光多普勒测速仪(PDA)对某低氮旋流燃烧器模型的出口流场进行了详细测量,得到了气相和颗粒相的速度及颗粒体积流量分布.结果表明:当燃烧器扩口角度从30°增大到45°时,环形回流区的最大径向跨度从40mm增加到70mm,最大回流速度从1.97m/s增大到2.45m/s;回流区的变大有利于延缓二次风与一次风的混合,能够减少NOx的生成量;当燃烧器扩口角度为60°时,二次风出现了"飞边"现象,一次风与二次风之间形成一个较大的低速回流区,但是它无法卷吸足够多的高温烟气,导致燃烧不能正常进行.

Phase Doppler Anemometry （PDA） was used to measure the flow field around the exit of a low NOx swirl burner, during which both the gas/solid velocity and the solid concentration distribution were obtained. Results show that the maximum radial span of the recirculation zone would rise from 40 mm to 70 mm, and the maximum velocity of backflow would rise from 1.97 m/s to 2.45 m/s, when the cone an- gle of swirl burner is raised from 30° to 45°. The enlargement of recirculation zone helps to delay the mixing of secondary air with primary air, which is beneficial to the reduction of NO. emission. When the cone angle increases to 60°, the secondary air would flow along the wall, and a big low-velocity recirculation zone would occur in the area between primary and secondary air, which is unable to entrain enough hightemperature flue gas to heat the primary air, thus resulting in abnormal combustion of the burner.