propeller
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Historical image of an advanced propeller model in
NASA Lewis Research Center's 8 × 6 foot supersonic wind tunnel
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A mechanical device designed to impart forward motion to an airplane
or ship, operating on the screw principle. It generally consists of two
or more inclined blades (airfoils) radiating
from a hub, and the amount of thrust it produces
is proportional to the mass of the fluid it acts on and the rate at which
it accelerates the fluid. The inclination, or pitch, of the propeller blades
determines the theoretical distance moved forward with each revolution.
A variable-pitch propeller can be adjusted while in motion,
to maximize its efficiency under different operating conditions; it may
also be possible to reverse the propeller's pitch, or to "feather" it –
i.e., minimize its resistance when not rotating. John Fitch,
in 1796, developed the first marine screw propeller; John Ericsson
perfected the first bladed propeller (1836).
Related
entry
• cavitation
Related category
• TECHNOLOGY
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