Which blade type allows for increased velocity of air while the fan is running?

The variable pitch blade type allows for increased velocity of air while the fan is running because it can adjust the angle of the blades in real-time based on the operational requirements. This flexibility enables the fan to optimize its performance by enhancing airflow and potentially improving efficiency, particularly under varying load conditions. By changing the pitch, the blades can create more lift and control the amount of air moved, leading to better performance when higher air velocity is needed.

In contrast, other types of blades, such as solid flat, forward curved, and airfoil, have fixed designs that do not allow for such adjustment during operation. While these blade types may also be effective in specific applications, they lack the adaptability of variable pitch blades to achieve increased air velocity dynamically.