High pressure axial fans

These are designed with hub diameters between 50% and 70% of the impeller diameter, compared with 30% to 40% for a gen­eral-purpose range of competitive cost. Aerodynamically this reduces the pressure limitation set by the slow-moving roots of the blades. Mechanically the short blades can be made far stiffer so that the impeller can be run at higher tip speeds with­out danger of flutter. The ratio of the annular flow area to the to­tal blade area decreases, making guide vanes or contra-rota — tion essential to recover the increased swirl energy. A typical fan is shown in Figure 1.89. Its performance is shown in Figure 1.90.

Posted in Fans Ventilation A Practical Guide