T-stages, sometimes called booster stages, are mounted on the low pressure (LP) shaft of some
turbofan
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which ac ...
engines directly behind the fan.
T-stages are used to increase overall pressure ratio and, for a given
core size
Core or cores may refer to:
Science and technology
* Core (anatomy), everything except the appendages
* Core (manufacturing), used in casting and molding
* Core (optical fiber), the signal-carrying portion of an optical fiber
* Core, the central ...
, the core mass flow. This is demonstrated by the following relationship:
:
:where:
:hp compressor entry mass flow =
:core size =
:hp compressor total head pressure ratio =
:lp compressor total head pressure ratio =
:lp compressor entry total pressure =
:lp compressor entry total temperature =
:hp compressor total head temperature ratio =
:lp compressor total head temperature ratio =
which varies more slowly than
So as
increases with the addition of T-stages,
also increases.
T-stages are a popular method for uprating the thrust of an engine (see, for example the
Pratt & Whitney Canada PW500
The Pratt & Whitney Canada PW500 is a series of medium thrust turbofan engines designed specifically for business jet applications.
Design and development
The PW530 has a single stage fan, driven by a 2-stage LP turbine, supercharging a 2A/1CF ...
).
The alternative is to place a
zero-stage
Jet engines and other gas turbine engines are often uprated by adding a zero-stage, sometimes written '0' stage, to the front of a compressor.Hooker, Sir Stanley (1984). ''Not much of an Engineer'', P. 153. Airlife Publishing Ltd, Shrewsbury, Eng ...
, mounted on the HP shaft, at the front of the HP compressor. This approach requires a significant change in the HP turbine, whereas a T-stage can, if necessary, be accommodated by simply adding another stage to the rear of the LP turbine.
Although T-stages usually only
supercharge the core stream, some engines do feature a deliberately oversized intermediate pressure (IP) compressor, which compresses both the core flow and a proportion of the bypass flow. This enhances the stability of the T-stages during throttling. Where necessary, the alternative is to employ blow-off valves.
References
{{Reflist
Jet engines