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What is the highest bypass ratio engine?
Modern engines in slower aircraft, such as airliners, have bypass ratios up to 12:1; in higher-speed aircraft, such as fighters, bypass ratios are much lower, around 1.5; and craft designed for speeds up to Mach 2 and somewhat above have bypass ratios below 0.5.
How fast can a turbojet engine go?
Turbojet aircraft work on the principle of accelerating a relatively small mass of air to a high speed. As optimum efficiency is achieved when the speed of the accelerated air approximates that of the aircraft, turbojet engines do not reach peak efficiency until speeds approaching mach 2.
What is a geared engine?
A geared turbofan engine is a variant of a conventional turbofan engine in which a reduction gearbox is installed between the fan and the low pressure (low speed) turbine. This lower speed means that additional compressor and turbine stages are required to maintain acceptable component efficiencies.
What is the maximum speed of all stages of a turbofan engine?
What is the maximum speed of all the stages of a geared bypass tubojet engine before they start losing efficiency. The maximum rotational speed of turbofan blades follows from compressibility effects, just like those for helicopter rotors and for propellers.
What is the benefit of a geared turbofan?
Benefit of the gearing can be seen from the shape of the engine: the low pressure turbine blades have a smaller radius than the fan blades, an un-geared engine would turn the LP turbine too slow. With a geared turbofan, the fan tip speed will stay at around the same tip speed, but the RPM of the LP turbine will be brought to a higher value.
Are there afterburners on a high bypass turbofan?
Afterburners are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or turbojet engines. Modern turbofans have either a large single-stage fan or a smaller fan with several stages. An early configuration combined a low-pressure turbine and fan in a single rear-mounted unit.
Which is more efficient a turbofan or a turbojet?
The overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft’s flight speed. In effect, a turbofan emits a large amount of air more slowly, whereas a turbojet emits a smaller amount of air quickly, which is a far less efficient way to generate the same thrust (see efficiency section below).