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In marine propulsion, a variable-pitch propeller is a type of propeller with blades that can be rotated around their long axis to change the blade pitch. Reversible propellers—those where the pitch can be set to negative values—can also create reverse thrust for braking or going backwards without the need to change the direction of shaft revolution.
An alternative design is the controllable-pitch propeller (CPP, or CRP for controllable-reversible pitch), where the blades are rotated normally to the drive shaft by additional machinery – usually hydraulics – at the hub and control linkages running down the shaft. This allows the drive machinery to operate at a constant speed while the ...
It is less useful on ships with propellers that have variable-pitch propellers or no propellers (like sailing ships). A variation of this approach was used by submarines during World War II to determine the speed of targets. The sonar operator would listen to the sound of a target's propeller and would determine its rotation rate or “blade ...
A pitch motion is an up-or-down movement of the bow and stern of the ship. The longitudinal/X axis , or roll axis , is an imaginary line running horizontally through the length of the ship, through its centre of mass, and parallel to the waterline .
Diameter of the propeller. The propeller advance ratio or coefficient is a dimensionless number used in aeronautics and marine hydrodynamics to describe the relationship between the speed at which a vehicle (like an airplane or a boat) is moving forward and the speed at which its propeller is turning.
A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. [1]
Blade pitch acts much like the gearing of the final drive of a car. Low pitch yields good low speed acceleration (and climb rate in an aircraft) while high pitch optimizes high speed performance and fuel economy. It is quite common for an aircraft to be designed with a variable-pitch propeller, to give maximum thrust over a larger speed range ...
If an impeller has only a few blades (i.e a large pitch), it will result in less lift force and in a similar manner for more blades (i.e. very low pitch), there will be high drag force. Blade solidity should not be confused with rotor solidity , which is the ratio of the total area of the rotor blades to the swept area of the rotor.
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