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A more serious problem with this type of propeller is a "frozen-on" spline bushing, which makes propeller removal impossible. In such cases the propeller must be heated in order to deliberately destroy the rubber insert. Once the propeller is removed, the splined tube can be cut away with a grinder and a new spline bushing is then required.
A propeller imparts momentum to a fluid which causes a force to act on the ship. [1] The ideal efficiency of any propulsor is that of an actuator disc in an ideal fluid. This is called the Froude efficiency and is a natural limit which cannot be exceeded by any device, no matter how good it is.
Contra-rotating propellers Contra-rotating propellers on the Rolls-Royce Griffon-powered P-51XR Mustang Precious Metal at the 2014 Reno Air Races. Aircraft equipped with contra-rotating propellers (CRP) [1] coaxial contra-rotating propellers, or high-speed propellers, apply the maximum power of usually a single piston engine or turboprop engine to drive a pair of coaxial propellers in contra ...
To explain aircraft and engine performance the same force is expressed slightly differently in terms of thrust and torque [29] since the required output of the propeller is thrust. Thrust and torque are the basis of the definition for the efficiency of the propeller as shown below.
Contra-rotating propellers should not be confused with counter-rotating propellers, a term which describes propellers rotating in opposite directions but sitting apart from each other on separate shafts instead of sharing a common axis. Tandem-rotor helicopters such as the CH-47 Chinook also use a counter-rotating arrangement.
The Voith Schneider propeller was originally a design for a hydro-electric turbine. [2] Its Austrian inventor, Ernst Schneider, had a chance meeting on a train with a manager at Voith's subsidiary St. Pölten works; this led to the turbine being investigated by Voith's engineers, who discovered that although it was no more efficient than other water turbines, Schneider's design worked well as ...
An actuator disk accelerating a fluid flow from right to left. In fluid dynamics, momentum theory or disk actuator theory is a theory describing a mathematical model of an ideal actuator disk, such as a propeller or helicopter rotor, by W.J.M. Rankine (1865), [1] Alfred George Greenhill (1888) and Robert Edmund Froude (1889).
A constant-speed propeller is a variable-pitch propeller that automatically changes its blade pitch in order to maintain a chosen rotational speed, regardless of the operational conditions of the aircraft. This is achieved by use of a constant-speed unit (CSU) or propeller governor, which automatically changes the propeller's blade pitch.