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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.
A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion.The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the additional fan stage.
Turboprop, turboshaft and turbofan engines have additional turbine stages to drive a propeller, bypass fan or helicopter rotor. In a free turbine the turbine driving the compressor rotates independently of that which powers the propeller or helicopter rotor. Cooling air, bled from the compressor, may be used to cool the turbine blades, vanes ...
There are two solutions to this problem: 1) Open up the cold nozzle area at low flight speeds, which moves the fan working line away from the surge. This has little effect on the position or slope of the surge line. OR 2) Make the effective surge line of the fan shallower by progressively reducing the pitch of the fan as the engine is throttled.
In a geared turbofan, a planetary reduction gearbox between the fan and the LP shaft allows the latter to run at a higher rotational speed thus enabling fewer stages to be used in both the LP turbine and the LP compressor, increasing efficiency and reducing weight. However, some energy will be lost as heat in the gear mechanism and weight saved ...
A fan from a Rolls-Royce RB211 turbofan engine, with its spinner visible at the centre of the fan blades.. The first spinners were fitted to aircraft in the early 1910s, originally to reduce drag caused by the large-diameter rotary engines of that era, and also were prominent on World War I-era aircraft, like the Morane-Saulnier N French monoplane fighter, and for the Central Powers, Robert ...
Jet propulsion is produced by some reaction engines or animals when thrust is generated by a fast moving jet of fluid in accordance with Newton's laws of motion.It is most effective when the Reynolds number is high—that is, the object being propelled is relatively large and passing through a low-viscosity medium.
The basic operation of the gas turbine is a Brayton cycle with air as the working fluid: atmospheric air flows through the compressor that brings it to higher pressure; energy is then added by spraying fuel into the air and igniting it so that the combustion generates a high-temperature flow; this high-temperature pressurized gas enters a ...