Ideal Brayton Cycle Air Standard Example 1

1
Ideal Brayton Cycle (Air Standard) Example 1
An ideal air standard gas turbine engine has a
compressor inlet temperature of 288 K and a
turbine temperature of 1400 K. Assume variable
specific heats, calculate the compressor work,
heat added, thermal efficiency, net work
developed by the engine if the compressor
pressure ratio is 12. (example 5.2b in the text)
T
3
Combustion chamber
Power turbine
3
2
1
5
4
4
2
5
1
compressor
Gas generator turbine
s
2
Example (1-2)

• From table B.1, one can find the enthalpy and
  relative pressure for states 1 (entering
  compressor) and 3 (leaving combustion chamber).

3
Example (1-3)
However, all mechanical devices operate with
losses and can not be exactly isentropic. This
imperfection can be taken into consideration by
using isentropic efficiency, defined as
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Isentropic Efficiency Example 2
Following the previous example, but consider the
effect of isentropic efficiency for all devices
as follows compressor efficiency 87, gas
generator turbine efficiency 89, and power
turbine efficiency 89. (a) Determine power
delivered by the turbine, (b) Determine the
overall thermal efficiency.
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Isentropic Efficiency Example (2-2)
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Isentropic Efficiency Example (2-3)