带有前后导叶的新型可逆轴流风机数值研究

地铁、隧道和地下工程等众多领域都要求轴流风机可以实现完全反转反风。针对这种特殊的要求,提出一种可明显提高可逆风机正反风效率的新方法,该方法要求在完全可逆风机动叶上下游设置安装角度为90°的完全对称翼型的前后导叶。对带前后导叶和不带前后导叶的两种风机取完全相同的计算区域,通过详细的数值计算和分析对比发现,带前后导叶的可逆风机的前导叶对进口气流方向基本没有影响,但是,后导叶却可以大幅降低出口周向旋绕速度,使得出口气流基本沿轴向流动,从而大大降低扩散筒内的气流沿程损失,扩散度越大效果越明显,同时也回收部分周向旋绕动能,增加出口静压。以上两种机理使得带前后导叶的新型风机的效率和全压都比无导叶的单叶轮风机明显提高,同时,结构的上下游完全对称也保证了风机正反风性能的完全可逆性。

Numerical Investigation on a New Type of Fully Reversible Axial Fan with Two Blade Rows on Both Sides of the Rotor

The fully reversible axial flow fans, which can rotate reversibly to ventilate in the opposite direction with the same performance curves, are widely demanded in subways, tunnels, underground warehouses and many other fields. A new configuration method, which can obviously improve the efficiency of reversible axial flow fans, is proposed to meet this special requirement. The new approach is to install two rows of blade with reverse symmetrical airfoil section at stagger angle of 90° on both sides of the rotor of reversible axial fans. The same computational domain is used for reversible flow fans with and without the two-row guide vanes, and the detailed numerical studies reveal that the upstream blade row has little influence on the direction of the incoming flow while the downstream blade row working as a straightener reduces the circumferential velocity of the rotor-exit air remarkably and makes the outlet air flow in nearly axial direction in the diffuser. This leads to a greatly decreased friction loss, and the greater the rate of divergence in the diffuser is, the more obvious the effect will be. In addition, part of the swirl dynamic energy of the rotor-exit air is recovered and changed into static pressure rise. The above two mechanisms contribute to the evident increase in both total pressure rise and efficiency of the new type of reversible axial fans with additional blade rows than those without any stators. Furthermore, the installation of the blade rows on both sides of the fully reversible axial fan guarantees a symmetric configuration and consequently guarantees the fully reversible performance also.