Propellere

Propellere are devices with rotating blades that generate thrust by accelerating a surrounding fluid, typically air or water. The action is based on aerodynamic or hydrokinetic lift: as the blades move, they act like wings at an angle to the flow, imparting momentum to the fluid and producing forward force on the vehicle.

The modern propeller system evolved in the 19th century for ships and aircraft. Early screw propellers replaced paddles, enabling longer-range propulsion and higher speeds. Over time, blade shapes were refined into airfoil profiles, blades were added or shortened, and hubs and spinners were developed to reduce drag and improve balance. This progress led to fixed-pitch and controllable-pitch designs, with increasing use of metal, and later composite materials, to raise strength and efficiency.

Key design features include the number of blades, blade twist (pitch), chord, and the overall diameter. Fixed-pitch propellers have a single blade angle set for a given regime, while controllable-pitch propellers allow the blade angle to be adjusted in operation to optimize thrust and efficiency under varying speeds and loads. Materials range from wood in early models to aluminum, steel, and advanced composites in modern applications. The hub, shaft, and sometimes a spinner contribute to aerodynamics and balance, while in marine settings cavitation and vibration are important considerations.

Applications span aviation, where propellers drive propeller airplanes and turboprops, to marine propulsion in ships and submarines, and in smaller formats for drones and unmanned systems. Ongoing development focuses on efficiency, noise reduction, and reliability through advanced airfoil designs and computational fluid dynamics.