TITLE.PM5

672 ENGINEERING THERMODYNAMICS

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T(Temp.)

s (Entropy)

Limiting turbine inlet temperature

3 ¢¢ 3 ¢ 3

4

4 ¢

4 ¢¢

2 ¢¢

2 ¢

2

1

Fig. 13.43

123 4 5 6 7 8 9 10

4

8

12

16

20

24

28

Pressure ratio

Thermal efficiency (%)

t = 1095°C 3

980

870

760

650

540

t = 15.5°C 1

hhcomp.= turbine= 0.80

Fig. 13.44. Effect of pressure ratio and turbine inlet temperature.
Following particulars are worthnoting :
Gas temperatures Efficiency (gas turbine)
550 to 600°C 20 to 22%
900 to 1000°C 32 to 35%
Above 1300°C more than 50%
Effect of turbine and compressor efficiencies :
Refer Fig. 13.45. The thermal efficiency of the actual gas turbine cycle is very sensitive to
variations in the efficiencies of the compressor and turbine. There is a particular pressure ratio at
which maximum efficiencies occur. For lower efficiencies, the peak of the thermal efficiency occurs
at lower pressure ratios and vice versa.