View source for Lewy's example

'''T-stage'''s, sometimes called boost stages, are mounted on the low pressure (LP) shaft of some [[turbofan]] engines directly behind the fan.

T-stages are used to increase overall pressure ratio and, for a given core size, the core mass flow. This is demonstrated by the following relationship:

:'''<math>w_2 = (w_2 \sqrt{T_3}/P_3) * (P_2/\sqrt{T_2})* (P_3/P_2) / \sqrt{T_3/T_2}  \,</math>'''

:where:

:core mass flow = '''<math>w_2 \,</math>'''                   

:core size = '''<math>(w_2 \sqrt{T_3}/P_3) \,</math>''' 

:core entry total pressure = '''<math>P_2 \,</math>'''

:core entry total temperature = '''<math>T_2 \,</math>'''

:core total head pressure ratio = '''<math>P_3/P_2 \,</math>''' 
            
:core total head temperature ratio = '''<math>T_3/T_2 \,</math>''' which varies more slowly than '''<math>P_3/P_2 \,</math>''' 

:'''Note:'''
:in this case, the core refers to the whole of the gas generator compression, not just that of the high pressure (HP) compressor.

:The first two terms - before the second multiply - are constant. The value of the remainder of the expression increases as the core pressure ratio increases.

T-stages are a popular method for uprating the thrust of an engine (see, for example the [[Pratt & Whitney Canada PW500]]). 

The alternative is to place a [[zero-stage]], 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 an additional stage to the rear of the LP turbine.

Although T-stages usually only [[Supercharger|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.

[[Category:Jet engines]]