机械通风冷却塔风筒内流场数值模拟研究

Numerical simulation of the flow field inside air duct of mechanical draft cooling tower

在机械通风冷却塔风机出口设置风筒可以降低出口动压,降低风机能耗。本文利用流体计算软件FLUENT进行数值模拟,研究了风筒内空气流动,发现风筒内空气呈旋转紊流射流流动;不同风筒高度与扩散角研究结果表明,随着风筒扩散角增大,风机风量和风筒动能回收率都呈现先增大后减小的变化规律;风筒高1/2D时,最佳扩散角为18°;风筒高1/3D时,最佳扩散角可以增大到20°;扩展了规范规定的最大扩散角不大于15°的限制。研究结果可供风机风筒设计改造时参考。

Setting up an air duct at the outlet of mechanical draft cooling tower can reduce air dynamic pressure and energy consumption of the fan. In this paper, CFD software FLUENT is used to simulate the air flow in duct, which proves that air flow in duct is a rotating turbulent jet. This study is made on the effects of different height and diffusion angle. Results show that, with the increase of diffusion angle, the air volume and kinetic energy recovery rate increase first and then decrease. The optimal diffusion angle is 18° when height of air duct is 1/2D, and the optimal diffusion angle is 20° when height of air duct is 1/3D. That extends the limits of the design specification where the diffusion angle is not more than 15°. The results of the study can be used for reference when designing and renovating the air duct.