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Why is a turboprop more efficient than an turbofan?
Compared to turbofans, turboprops are most efficient at flight speeds below 725 km/h (450 mph; 390 knots) because the jet velocity of the propeller (and exhaust) is relatively low. Modern turboprop airliners operate at nearly the same speed as small regional jet airliners but burn two-thirds of the fuel per passenger.
Why do we find high bypass fans and turboprops on cargo planes and airliners?
Because of the aerodynamic efficiency of propellers and fans, it is more fuel efficient to accelerate a large mass by a small amount. That is why we find high bypass fans and turboprops on cargo planes and airliners. For these airplanes, engine efficiency is not as important as very high thrust.
Why is high bypass ratio better?
As bypass ratio (BPR) increases the overall efficiency of the engine increase which is a primary factor that yields lower TSFC for the turbofan engine. Additionally this report shows that a high bypass ratio engine can produce a greater amount of thrust while consuming the same amount of fuel as a lower BPR engine.
How is turbofan engine different from turbojet engine?
Unlike a turbojet that sucks in all the air inside the engine, a turbofan engine sports a large fan at the front which sucks in most of the airflow around the outside of the engine. This makes the engine quieter and more thrust at low speeds. A majority of all the airliners are powered by this engine.
Are turboprops safer than turbofans?
Both turboprops and turbofans are extremely reliable and safe engines. The safety challenges associated with each result from their respective installation requirements. Propellers need space from the ground and from the fuselage, presenting unique aerodynamic challenges in the event of an engine failure.
What is a turboprop engine?
It can be useful to think of turboprops as unducted turbofans in some sense, where the propeller is the first fan in the compressor section, however it should be noted that there is no actual bypass air for a turboprop engine. This analogy breaks down in a mechanical sense but is useful aerodynamically and thermodynamically.
How do turbofan engines work?
A turbofan essentially uses a shrouded propeller of high solidity (or activity ratio) which helps to accelerate the flow through it as much as possible. It needs to produce the most thrust from the limited air volume captured by the shroud’s intake.
Why are turbofan engines more efficient at high altitudes?
Because turbofans continue to produce thrust at high speeds, the aircraft is able to balance reduced thrust output at altitude against lower atmospheric density. As a result of these factors, turbofan engines are most efficient relative to operating speeds at higher altitudes.