Propellerdrivning

Propellerdrivning, or propeller propulsion, is a method of generating thrust by rotating a propeller to push fluid (air or water) backward, thereby moving the vehicle forward. It is the dominant form of propulsion for most ships and many aircraft.

In marine contexts, the system comprises a prime mover (such as a diesel engine, gas turbine, or steam turbine), a reduction gearbox or direct drive, a propeller mounted on a shaft, and stern-tube bearings. The propeller converts rotational power into thrust. Variants include fixed-pitch propellers, which have blades with a fixed angle, and controllable-pitch propellers, whose blade pitch can be adjusted to optimize thrust and efficiency over a range of speeds. Efficient operation depends on hull form, speed, depth, cavitation control, and shaft alignment.

In aviation, propeller propulsion uses piston engines or gas-turbine engines (turboprops). Propellers may be driven directly or via reduction gears to operate at speeds where aerodynamic efficiency is high. Variable-pitch or constant-speed propellers are controlled by governors or electronic systems to maintain optimal efficiency and prevent engine overspeed. In engine-out scenarios, some aircraft propellers can be feathered to reduce drag.

Other topics related to propellerdrivning include contra-rotating propellers, which rotate two coaxial blades in opposite directions to recover swirl and improve efficiency; azimuth thrusters, which allow thrust direction to be changed; and considerations of cavitation, noise, and vibration.

History and significance: Propeller-driven propulsion emerged in the 19th century and became standard for ships and aircraft in the 20th century, accompanied by ongoing advances in blade design, materials, and control systems.