Propeller

Propeller

A Propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid (such as air or water) is accelerated behind the blade. Propeller dynamics, like those of aircraft wings, can be modelled by Bernoulli's principle and Newton's third law. Most marine propellers are screw propellers with fixed pitch blades rotating around a horizontal (or nearly horizontal) axis.

History

The principle employed in using a screw propeller is used in sculling. It was probably used first in this way. As screw propulsion became widespread, the word propeller replaced screw, although the former term is still used in some contexts.

Types of Propellers

There are several types of propellers, including:

• Fixed-pitch propeller: This is the simplest type of propeller. The blades' pitch is set at a fixed angle. It is efficient at one rotational speed and forward speed only.

• Controllable-pitch propeller: The pitch of the blades can be adjusted by a mechanism inside the hub. This allows for better performance at a range of speeds.

• Contra-rotating propellers: Two propellers are placed one behind the other, and they rotate in opposite directions.

• Modular propeller: The blades are separately produced and then assembled with the hub. This allows for easy replacement of damaged blades.

See Also

• Impeller
• Turbine
• Rotor (aeronautics)

References

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