OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
r = 10, T0 = 25 0 C, R.H. = 60% , TIT = 1247 0 C
Generation efficiency (%)
40
30
20
10
0
29.93
Simple cycle
30.11
33.33
33.4
37.66
37.62
Simple cycle with Simple cycle with Simple cycle with Simple cycle with Simple cycle with
fog cooling STIG (0.1) fog cooling and STIG (0.2) fog cooling and
STIG (0.1)
STIG (0.2)
Cycles
Fig. 3- Comparison of Generation efficiency for different cycles
The trend of graphs shows that the combination of fogging and STIG with simple cycle gas turbine cycle is a
good approach to enhance the performance of the system on the basis of first law as well as second law. Fig.2 &
3 predict that power output is maximum in case of simple cycle with fogging and STIG and generation efficiency
is maximum for STIG only. The power output increases as the mass flow rate increases and generation efficiency
reduces minutely due to higher fuel-air-ratio.
Fig. 4- The effect of steam injection ratio on First-law efficiency, generation efficiency and process heat
The Fig.4 shows the effect of STIG (0-0.2% of mass flow rate of air) on generation efficiency, first law
efficiency and process heat for fixed inlet air conditions as the air gets saturated up to 100% R.H. The first law
efficiency falls with the increasing amount of steam injection ratio. The reason for decrease in First-law
efficiency is that the slope of process heat is sharper than the slope of generation efficiency. The generation
efficiency increases while the process heat falls with increasing amount of steam injection ratio along with the
fogging of air up to 100% R.H. The graph predicts that steam injection effects the generation ef ficiency, firstlaw
efficiency and process heat more than the fog cooling of inlet.
The exergy destruction rate (MW) for different system components with different amount of STIG has been
shown in Fig.5. The power output increases for large amount of STIG due to increasing mass flow rate of air.
While the exergy destruction rate increases into the Combustion chamber, turbine and HRSG. The exergy
destruction in combustion chamber is highest among all the system components due to highest temperature of
combustion chamber. The graph predicts that steam injection increases the exergy destruction in combustion
chamber due to mixing of high temperature superheated steam to the combustor highers the overall temperature.
The exergy destruction rate (MW) per MW of power output for different system components with different
amount of STIG has been shown in Fig.6. Due to significant increase in power output the rate of exergy
destruction (MW) per MW of power output reduces for combustion chamber, compressor, HRSG and Stack -
gases while increases for gas turbine due to increasing mass flow rate with steam of lower exergy.
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