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
to the reheat LM5000 and the reheat steam cycle. Rice (1986) also suggested a method for choosing
optimal values of combined-cycle parameters such as pinch point, gas pressure drop, single or dual pressure
and reheat, based on the economical internal rate of return.
Figure 2. Integrated gasification combined cycle.
Lugand and Parietti (1991) showed that a three-pressure level steam reheat cycle, featuring a 200 MW gas
turbine engine with a firing temperature of 1260°C, yields plant efficiencies in excess of 53%. A parametric
analysis was conducted by Cerri and Sciubba (1987) for a plant equipped with a gas generator and with
steam injection into an after-burner placed upstream of the power turbine. The steam was to be produced by
a waste-heat recovery section made up of a boiler and distillation plant fed by the gas turbine exhaust. The
results showed a 13% improvement in plant efficiency and a doubling of the specific work output when
compared with a standard gas turbine cycle with full reheat and optimal steam injection.
A novel heat-recovery process for improving the thermal efficiency of a gas turbine in electric power
generation was suggested by Higdon et al. (1990). The process uses an air saturation unit to evaporate
heated water (below its boiling point) into the combustion air. The resultant mass flow of water vapor
through the rest of the system reduces the power required to compress air and permits better utilization of
the otherwise wasted heat. The authors calculated the efficiency of the system to be 54.8%, as compared to
47.9% for an inter-cooled, steam-injected system.
Compressed air energy storage (CAES) emerged as an innovative method of meeting peak demand
requirements of electric utilities. Excess power produced during low-load periods is utilized to compress air
and store it; the stored energy is then returned to the system during peak-load periods (Lee 1991).
Gyarmathy (1989) studied the relative merits of various load control methods involving fixed and variablegeometry
gas turbine compressors. The results implied exceptional merits for compressor guide vane
adjustment, serving to maintain gas turbine exhaust temperature at high levels during part-load operation.
Conclusions
The combined-cycle generation system features high thermal efficiency, low installed cost, fuel flexibility
with a wide range of gas and liquid fuels, low operation and maintenance costs, operating flexibility at
base, mid-range and daily start, high reliability and availability, short installation times and high efficiency
in small capacity increments. In particular:
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