6.107
A modern jet engine has a temperature after combustion of about 1500 K at 3200
kPa as it enters the turbine setion, see state 3 Fig. P.6.107. The compressor inlet is
80 kPa, 260 K state 1 and outlet state 2 is 3300 kPa, 780 K; the turbine outlet state
4 into the nozzle is 400 kPa, 900 K and nozzle exit state 5 at 80 kPa, 640 K.
Neglect any heat transfer and neglect kinetic energy except out of the nozzle. Find
the compressor and turbine specific work terms and the nozzle exit velocity.
Solution:
The compressor, turbine and nozzle are all steady state single flow devices
and they are adiabatic.
We will use air properties from table A.7.1:
h
1 = 260.32, h2 = 800.28, h3 = 1635.80, h4 = 933.15, h5 = 649.53 kJ/kgEnergy equation for the compressor gives
w
c in = h2 – h1 = 800.28 – 260.32 = 539.36 kJ/kgEnergy equation for the turbine gives
w
T= h
3 – h4 = 1635.80 – 933.15 = 702.65 kJ/kgEnergy equation for the nozzle gives
h
4= h
5 + ½ V2
5
½
V2
5
= h4 - h5 = 933.15 – 649.53 = 283.62 kJ/kgV
5
= [2( h4 – h5) ] 1/2 = ( 2 283.62 1000 ) 1/2 = 753 m/s