Sensitivity analysis of STIG based combined cycle with dual pressure HRSG

Thermodynamic evaluation has been carried out for a combined cycle with STeam Injected Gas Turbine (STIG) having dual pressure heat recovery steam generator (HRSG). Steam from high-pressure steam turbine is injected into the combustion chamber at a pressure higher than the combustion pressure to improve the exergy efficiency of combined cycle. The effect of steam injection mass ratio, deaerator pressure (or temperature ratio), steam reheat pressure ratio, HP steam turbine pressure, compressor pressure ratio and combustion temperature on combined cycle exergy efficiency has been investigated. It has been found that advantage from steam injection to combined cycle is obtained at high steam reheat pressure and high steam turbine inlet pressure. At this condition, the increasing effect of gas cycle output exceeds the decreasing effect of steam cycle output. The major exergetic loss that occurs in combustion chamber decreases with introduction of steam injection in to the combustion.