Parametric simulation of steam injected gas turbine combined cycle

Abstract

In the current work, thermodynamic analysis has been conducted for a steam injected gas turbine (STIG) in the combined cycle system with the dual pressure heat-recovery steam generator. Effect of operating variables such as low-pressure (LP) steam temperature ratio, steam reheat pressure ratio, steam turbine inlet pressure, gas cycle pressure ratio and combustion chamber temperature on the efficiency of the combined cycle has been investigated. Exergy efficiency of the cycle is compared with and without the steam injection with respect to the above-mentioned parameters. Maximum mass ratio of steam injection to fuel has been examined as 6 kg/kg fuel with the complete combustion of the fuel due to excess air supply in the combustion chamber and gas reheater. Results are plotted from the case of without steam injection to the maximum possible steam ratio. LP temperature ratio is identified as a dominant parameter having impact on the efficiency of the combined cycle as the steam is injected at this pressure. Component exergetic losses of the combined cycle as a fraction of exergy of fuel are compared with and without the steam injection. The results showed that the major exergetic loss in the combustion chamber decreased with the steam injection.