直接空冷凝汽器干式吹扫系统的喷嘴流场特性

Characteristics of nozzle outflow field of dry air blowing system for direct air-cooled condenser

针对干式吹扫系统压缩空气从喷嘴射入到凝汽器翅片时,其速度减小影响吹扫效果的问题,运用射流动力学和计算流体力学理论对喷嘴外流场进行模拟,分析喷嘴结构和喷嘴到翅片的距离(靶距)对喷嘴射流能力的影响。研究结果表明:在相同靶距和工作压力下,与圆柱长度30 mm、直径为1.6 mm的喷嘴相比,圆柱长度为25 mm、直径为1.8 mm的喷嘴射程更长,速度更高,射流能力更强;在相同条件下,与单孔喷嘴相比,双孔喷嘴的射程更长,射流面积更大,喷嘴射流能力更强。靶距越大,翅片入口的空气速度越小,射流面积则先增大后减小;为满足较高的吹扫效果,当喷嘴入口压力为0.65 MPa时,选取收缩角为40?,圆柱长度为25 mm,圆柱直径为1.8 mm的喷嘴结构,采用双孔布置,最佳靶距为40 mm。

Considering that when compressed air injects into the condenser fin from nozzle, its speed is weakened, whichinfluences the effect of air blowing, the outflow field of nozzle was simulated by jet dynamics and computational fluiddynamics. The influences of the structure and distance from the nozzle to the fin （target distance） on jet ability wereanalyzed. The results show that when the target distance and work pressure are the same, the nozzle whose cylinderlength is 25 mm and cylinder diameter is 1.8 mm has a longer range, a higher speed and better jet ability than the onewhose cylinder length is 30 mm and cylinder diameter is 1.6 mm. Compared with the single hole nozzle, the double holenozzle has a longer range, a larger area and better jet ability under the same conditions. With the increase of the targetdistance, the air velocity at the fin entrance decreases, and the jet area increases firstly and then decreases. In order toachieve better blowing effect, the nozzle which has a contraction angel of 40？, a cylinder length of 25 mm, and a cylinderdiameter of 1.8 mm is selected and double holes layout is adopted, and the best target distance of the nozzle is 40 mmwhen the inlet absolute pressure of the nozzle is 0.65 MPa.