blade twist

blade twist

blade twistclick for a larger image
Propeller blades are designed with a twist with higher angle at the hub than at the tip. This is to equalize the lift distribution along the blade to the extent possible. During the rotation the tips of the blades move at a faster pace than those areas near the hub. If the blade did not have twist all along from hub to the tip, there would be dissymmetrical rotation speed and consequently lift. Hence, the necessity for blade twist.
i. The undesirable variation in pitch from root to tip caused by aerodynamic loading.
ii. The twist built into a propeller or rotor blade. In the case of a propeller, it is to ensure that the pitch angle at the root is greater than the tip. In the case of rotors, it is to compensate for unequal lift between inside and outside the rotor as well as to maintain RPM during autorotation.
References in periodicals archive ?
from which it is possible to determine geometric relations and constructional parameters of a propeller--the angle of a blade twist [phi], the blade depth b and the blade thickness t.
Wind flow analysis is done over each configuration of the rotor with the blade twist angles ranging from 5[degrees] to 60[degrees] in steps of 5[degrees].
The cooling capacity, cross sectional profile, blade arrangement, blade length, blade twist, tip width and tip clearances, are all configured for optimum performance.