Page 48 - Advanced Gas Turbine Cycles

Chapter 2. Reversibility and availability 25

EP4

0 S
Fig. 2.8. Exergy fluxes in actual CBT gas turbine plant with combustion.
The rational efficiency may be defined as the ratio of the actual work output [ Wcv]i to
the maximum possible work output, approximately [-AGO],

(2.50)

Fig. 2.9 illustrates this approach of tracing exergy through a plant. The various terms
in Eq. (2.49) are shown for an irreversible open gas turbine plant based on the JB cycle.
The compressor pressure ratio is 12:1, the ratio of maximum to inlet temperature is 5:l
(T- = 1450 K with To = 290 K), the compressor and turbine polytropic efficiencies are

0.4

0.35
>
2 0.3 1. WORK OUTPUT
w
2. COMBUSTION LOSS
0.25 3. COMPRESSOR LOSS
W 4. TURBINE LOSS
2
0.2 5. EQOUT= 0
0 6. EXHAUST LOSS
z
E 0.15
0
2 0.1

0.05
n n
0
3 4 5
COMPONENT
Fig. 2.9. Work output and exergy losses in CBT gas turhine plant (all as fractions of fuel exergy).