440
12 Thrust Gas Turbines
The p 01 /p 0 ratio is denominated aerodynamic compression ratio.
b. Compressor
c. Combustion chamber
Here, we simplify by the assumption of constant mass flow rate and constant specific heat.
d. Turbine
e. Jet generator
Thermodynamic efficiency is:
1
1
td
r
g
g
h
−
−
= −
, with r r r
a c
=
.
We obtain the same expression as with a stationary gas turbine, when the overall
pressure ratio is applied, being the product of aerodynamic (  r a ) and mechanical (  r c )
pressure ratios.
Due to the aerodynamic pressure ratio, the efficiency potential is very high. The
mechanical pressure ratio of a modern turbofan engine is around 40 [1, 3]. With this
pressure ratio, we obtain:
r
p
p
c = 02 01
/
,
1
02
02
01
01
01
01
(
)
(
1)
(
1).
c
p
p
p
c
T
W C T
T
C T
C T r
T
g
g
−
=
−
=
− =
−
∆Q C T
T
p
=
−
(
) .
03
02
W C T
T
W
t
p
c
=
−
=
(
)
.
03
04
1
03
03
0
4
,
( ) ,
a c
a c
e
p
T
r r
r r
p
T
g
g
−
=
=
2
0
03
4
03
4
02
0
(
)
(
)
(
) .
2
gas
p
e
c
p
e
p
v
W
C T
T
W
C T
T
C T
T
=
−
−
−
=
−
−
−
1
1
03
02
1 ( )
1 ( )
.
gas
p
a c
p
a c
W
C T
r r
C T
r r
g
g
g
g
−
−
−
−




=
−
−
−











