Page 417 - Advanced thermodynamics for engineers

17.3 AIRCRAFT GAS TURBINES 407

1
2 3 4
Combustion
chambers 5
m m

FIGURE 17.21
Single spool turbojet.
Solution
From the international standard atmosphere table, at 5000 m

p a ¼ 0:5405 bar and T a ¼ 255:7K:
The stagnation conditions after the inlet may be obtained as follows:
V a 2 270 2
¼ ¼ 36:3K
2c p 2 1:005 1000
V 2 a
T 01 ¼ T a þ ¼ 255:7 þ 36:3 ¼ 292 K
2c p
k=ðk 1Þ
T 01
p 01 ¼ p a ¼ 0:8602 bar:
T a
At the outlet from the compressor

p 02
p 02 ¼ p 01 ¼ 8:0 0:8602 ¼ 6:88 bar
p 01
ðk 1Þ=k
!

T 01 p 02 292 0:286
T 02 T 01 ¼ 1 ¼ 8:0 1 ¼ 272:7K
h C p 01 0:87
T 02 ¼ 292 þ 272:5 ¼ 564:7K
w T ¼ w C =h m and hence

T 02 T 01 1:005 272:7
c p a
T 03 T 04 ¼ ¼ ¼ 241:4K
1:147 0:99
c p g
T 04 ¼ 1200 241:4 ¼ 958:6K
4
T 04
0 k=ðk 1Þ 931:8
p 04 ¼ p 03 ¼ 6:88 ¼ 2:501 bar:
T 03 1200
The nozzle pressure ratio is therefore
p 04 2:501
¼ ¼ 4:627
p a 0:5405