The temperature of air entering the compressor of a gas turbine plant significantly affects the work availability from the plant. In order to have lesser compressor work requirement the temperature of air entering the compressor should be low. Gas turbine cycle efficiency can also be improved by reducing the heat addition in the combustion chamber for the same turbine inlet temperature. In this paper, a combined cycle arrangement employing compressor inlet air cooling and fuel heating prior to injection in the combustion chamber is considered for thermodynamic analysis. The variation in inlet air temperature at the inlet of the compressor and fuel preheating using a part of steam generated in Heat Recovery Steam Generator (HRSG) is considered. Closed loop cooling technique is used for maintaining the gas turbine blade temperature within metallurgical limits. Water bled after condenser and steam generated at three different pressures and temperatures is used to meet the coolant and fuel heating requirements. The results obtained have been plotted suitably for studying the influence of one parameter upon the other at varying cycle pressure ratio and turbine inlet temperatures.

Gas/steam combined cycle has synergetic operation of gas turbine cycle and steam turbine cycle also referred to as high temperature `topping cycle' and lower temperature `bottoming cycle', respectively. Performance improvement of gas turbine-based topping cycle can be had either by increasing the network availability or reducing the external heat addition in the combustion chamber through lesser fuel requirement or both. The work output of gas turbine can be enhanced either by increasing the Turbine Inlet Temperature (TIT) or by reducing work requirement in compressor through lower inlet air temperature or both. Effective cooling of gas turbine blades becomes imperative for encountering higher turbine inlet temperatures. For effective cooling air, steam, water, etc., can be used as the coolant in different cooling techniques such as open loop and closed loop cooling. These coolants get mixed with expanding gases in case of open loop cooling and they do not mix in case of closed loop cooling. Coolants for gas turbine blade cooling are available either from within the cycle or from outside depending upon the cooling employed. Air as coolant can be bled from the compressed air, steam as coolant can be extracted from the steam generated in Heat Recovery Steam Generator (HRSG) and water as coolant can be had from the bottoming cycle. Exhaust from gas turbine is utilized to generate steam at the required pressure and temperature in the HRSG at triple pressure for expansion in the steam turbine.

For lowering the compressor work requirement, air entering the compressor may be cooled before being compressed. Inlet air can be cooled by employing solar air refrigeration. Here, the study is limited to see the effect of inlet air cooling upon the combined cycle performance.

Mechanical Engineering Journal, Inlet Air Cooling, Heat Recovery Steam Generator, HRSG, Closed Loop Cooling Technique, Turbine Inlet Temperature, Thermodynamic Analysis, Cooling Temperatures, Steam Generating Temperatures, Gas Turbine Cycles, Blade Cooling, Fuel Heating Options.