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Propeller design

Propellers are the basically a airfoil that unlike the fixed wing airfoil is forced to rotate around the hub. This rotation of the propeller produces acceleration of the air ie the air is sucked in with high acceleration. This results in the forward motion of an aircraft.

With increase in engine power and need, the design factors of any propeller play an important role. The design factor of a propeller are:
1. Blade tip speed.
2. Solidity of the blade.
3. Aspect Ratio.
4. No of blades.

As the increasing production of powerful engine, the propeller also need to absorb the high power of the engine. The increase in the power of the propeller means increase in the volume of air being sucked in. This can be achieved in different ways.

1. increase the diameter of the propeller


2. increase the solidity of the propeller


3. increase the number of the blades


The blade tip speed can be delayed by using scimitar- like the swept back wings used in aircrafts.

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Forces acting on a propeller are:
1. Thrust Bending force
2. Centrifugal Force
3. Torque Bending Force
4. Aerodynamic Twisting Forcing
5. Centrifugal Twisting Forcing


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Types of Propeller:
According to varying pitch:
1. Fixed Pitch Propeller
2. Variable Pitch Propeller
3. Ground Pitch Propeller
4. Constant Speed Propeller
According to blade rotation direction:
1. Counter rotating propeller
2. Contra rotating propeller

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Other important phenomenons related to propellers.
1. Feathering
2. Reverse pitch
3. Wind mill effect


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