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The advance ratio is critical for determining the efficiency of a propeller. At different advance ratios, the propeller may produce more or less thrust. Engineers use this ratio to optimize the design of the propeller and the engine, ensuring that the vehicle operates efficiently at its intended cruising speed, see propeller theory.
Propulsive efficiency comparison for various gas turbine engine configurations. The calculation is somewhat different for reciprocating and turboprop engines which rely on a propeller for propulsion since their output is typically expressed in terms of power rather than thrust. The equation for heat added per unit time, Q, can be adopted as ...
When a propeller is added to a ship its performance is altered; there is the mechanical losses in the transmission of power; a general increase in total resistance; and the hull also impedes and renders non-uniform the flow through the propeller. The ratio between a propeller's efficiency attached to a ship and in open water (′) is termed ...
Propeller-driven airliners had useful load fractions on the order of 25–35%. Modern jet airliners have considerably higher useful load fractions, on the order of 45–55%. For orbital rockets the payload fraction is between 1% and 5%, while the useful load fraction is perhaps 90%.
P R curve for the light aircraft with the drag curve above and weighing 2000 kg, with a wing area of 15 m² and a propeller efficiency of 0.8. W = (ρ/2).S.V 2.C L and P R = (ρ/2η).S.V 3.C D. The extra factor of V /η, with η the propeller efficiency, in the second equation enters because P R = (required thrust)× V /η. Power rather than ...
The propeller characteristics are commonly expressed as dimensionless ratios: [31] Pitch ratio PR = propeller pitch/propeller diameter, or P/D; Disk area A 0 = πD 2 /4; Expanded area ratio = A E /A 0, where expanded area A E = Expanded area of all blades outside of the hub.
The propellant mass fraction is the ratio of just the propellant to the entire mass of the vehicle at takeoff (propellant plus dry mass). In the cases of a single-stage-to-orbit (SSTO) vehicle or suborbital vehicle, the mass fraction equals the propellant mass fraction, which is simply the fuel mass divided by the mass of the full spaceship.
Rotor solidity is a dimensionless quantity used in design and analysis of rotorcraft, propellers and wind turbines.Rotor solidity is a function of the aspect ratio and number of blades in the rotor and is widely used as a parameter for ensuring geometric similarity in rotorcraft experiments.