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Applications 11
Chapter 2
Applications
Gas turbines are used in diversified services from jet engines
and simple mechanical drives (on land, sea and air) to sophisticated
gas lasers and supersonic wind tunnels. For simplicity
the gas turbine will be considered for airborne applications and surface
(land and sea) based applications. In the airborne applications
these units are referred to as jets, turbojets, turbofans, and turboprops.
In land and sea based applications these units are referred to
as mechanical drive gas turbines. Each category will be discussed in
detail.
JET ENGINES
In the strict sense all gas turbines are gas generators. Their hot
gases are expanded either through a turbine to generate shaft power
or through a nozzle to create thrust. Some gas generators expand
their hot gases only through a nozzle to produce thrust—these units
are easily identified as jet engines (or turbojets). Other gas turbines
expand some of the hot gas through a nozzle to create thrust and the
rest of the gas is expanded through a turbine to drive a fan —these
units are called turbofans. When a unit expands virtually all of its hot
gases through the turbine driving the compressor and the attached
propeller and no thrust is created from the gas exiting the exhaust
nozzle—it is called a turboprop. All of the above describe flight engines.
However, turboprops have much in common with land and sea
based gas turbines. This should not be surprising as in many cases
the basic gas turbine is identical for both applications. The engines
used in aircraft applications may be either turbojets, turbofans, or
turboprops, but they are all commonly referred to as “jet engines.”
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