turboprop engine
Many low speed transport aircraft
and small commuter aircraft use turboprop propulsion.
On this page we will discuss some of the fundamentals of
turboprop engines. 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!). In the turboprop, a gas turbine core is used. How
does a turboprop engine work?
There are two
main parts to a turboprop propulsion system, the core engine
and the propeller. The core is very similar to a basic
turbojet except that instead of expanding all the hot exhaust
through the nozzle to produce thrust, most of the energy of
the exhaust is used to turn the turbine. There may be an
additional turbine stage present which is connected to a drive
shaft. The drive shaft, also shown in green, is connected to a
gear box. The gear box is then connected to a propeller
that produces most of the thrust. The exhaust velocity of a
turboprop is low and contributes little thrust because most of
the energy of the core exhaust has gone into turning the drive
shaft.
Because
propellers become less efficient as the speed of the aircraft
increases, turboprops are used only for low speed aircraft
like cargo planes. High speed transports usually use
high bypass
turbofans because of the high fuel efficiency and high
speed capability of turbofans. A variation of the turboprop
engine is the turboshaft engine. In a turboshaft engine,
the gear box is not connected
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