How does a propfan work?
These fans are driven by a turbine engine through a reduction gear or a low-speed free turbine. High rpm is used to reach higher speeds and altitudes than conventional propellers. The contra-rotating fan arrangement is used to remove torque effect, and to enhance efficiency (note: some early versions had just one fan).
How do propfan engines work?
The turboprop uses a gas turbine core to turn a propeller. As mentioned on a previous page, propeller engines develop thrust by moving a large mass of air through a small change in velocity. Propellers are very efficient and can use nearly any kind of engine to turn the prop (including humans!).
What is a propfan engine?
The propfan is also known as the unducted fan (UDF) engine because the fan is not enclosed like that of a turbofan. The propulsive efficiency of a propfan engine is increased by the high bypass ratio achieved using external fan blades.
What are the advantages of turbofans over propellers?
Typical high bypass ratio turbofans can easily achieve propulsive efficiencies that can compete with propellers (> 80\%), but at higher cruise velocities than typical propellers can achieve. The lower jet exit velocities generated by turbofans also makes the engine quieter and reduces noise pollution near airports.
What is a turbofan fan?
A fan is basically a propeller with a lot of blades specially designed to spin very quickly. Its function is essentially identical to a propeller, namely, the blades accelerate the oncoming air flow to create thrust. In a turbofan, however, the fan is driven by turbines in the attached turbojet engine, rather than by an internal combustion engine.
What is a turboprop engine and how does it work?
A turboprop engine enjoys the high efficiency of a propeller, owing to the large bypass ratio it provides. In fact, nearly all of the thrust generated by a turboprop is from the propeller. A turboprop also enjoys the high power-to-weight ratio of turbojet engines, resulting in a powerful compact propulsion system.