TITLE.PM5

GAS POWER CYCLES 677

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\M-therm\Th13-5.pm5

diagram as air heater. The air exhausted from the power turbine is cooled before readmission to
L.P. compressor. The various operations as indicated on T-s diagram (Fig. 13.51) are as follows :
Operation 1-2′ : Air is compressed from p 1 to px in the L.P. compressor.
Operation 2′-3 : Air is cooled in the intercooler at constant pressure px.

Work

Heat

exchanger

External

combustion

(Q ) 2

External

combustion

(Q ) 1

Q 4

10

1

Cooler

4 ′

L.P.

C

H.P.

C

H.P.

T

2 ′ 3

Intercooler

Q 3

5

6

7 ′

9 ′

8

L.P.

T

Fig. 13.50. Closed cycle gas turbine plant.

Operation 3-4′ : Air is compressed in the H.P. compressor from px to p 2.

Operation 4′-5 : High pressure air is heated at constant pressure by exhaust gases from

power turbine in the heat exchanger to T 5.

Operation 5-6 : High pressure air further heated at constant pressure to the maximum

temperature T 6 by an air heater (through external combustion).

Operation 6-7′ : The air is expanded in the H.P. turbine from p 2 to px producing work to

drive the compressor.

Operation 7′-8 : Exhaust air from the H.P. turbine is heated at constant pressure in the

air heater (through external combustion) to the maximum tempera-

ture T 8 (= T 6 ).

Operation 8-9′ : The air is expanded in the L.P. turbine from px to p 1 , producing energy

for a flow of work externally.

Operation 9′-10 : Air from L.P. turbine is passed to the heat exchanger where energy is

transferred to the air delivered from the H.P. compressor. The tem-

perature of air leaving the heat exchanger and entering the cooler is

T 10.