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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 ...
The ratio between a propeller's efficiency attached to a ship and in open water (′) is termed relative rotative efficiency. The overall propulsive efficiency (an extension of effective power ()) is developed from the propulsive coefficient (), which is derived from the installed shaft power modified by the effective power for the hull with ...
The thermodynamic and propulsive efficiencies are independent. For the turbojet though, any improvement which raised the cycle pressure ratio or turbine inlet temperature also raised the jet pipe temperature and pressure giving a higher jet velocity relative to aircraft velocity. As the thermal efficiency went up the propulsive efficiency went ...
This article explains the application of the "Betz limit" to the efficiency of a ground-based wind turbine. Froude's blade element theory (1878) [3] is a mathematical process to determine the behavior of propellers, later refined by Glauert (1926).
Characteristic velocity or , or C-star is a measure of the combustion performance of a rocket engine independent of nozzle performance, and is used to compare different propellants and propulsion systems. c* should not be confused with c, which is the effective exhaust velocity related to the specific impulse by: =.
The following table gives the efficiency for several engines when running at 80% throttle, which is approximately what is used in cruising, giving a minimum SFC. The efficiency is the amount of power propelling the plane divided by the rate of energy consumption. Since the power equals thrust times speed, the efficiency is given by
The bypass ratio (BPR) of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. [1] A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core.
The number relates to propulsive efficiency, which peaks between 70%–80% when within the optimal Strouhal number range of 0.2 to 0.4. Through the use of factors such as the stroke frequency, the amplitude of each stroke, and velocity, the Strouhal number is able to analyze the efficiency and impact of an animal's propulsive forces through a ...