Keywords: gas turbines, partial oxidation cycle, reheat cycle, steam injection, gas turbine cycles, heat recovery, performance improvement
Comparative study of steam injection effects on operation of gas turbine cycles
In the present work, gas turbine cycles are modified with steam injection between the combustion chamber exit and the gas turbine inlet. Heat recovery steam generators, utilising the exhaust gases, provide these cycles with the injected steam at saturated vapour. The irreversibility of the different composing units of the cycles and the variation of gas properties owing to steam injection as well as changes in the interrelation of component performance parameters are taken into account. The isentropic temperature ratio and maximum to minimum cycle temperature ratio are varied over some ranges that slightly exceed their practically acceptable bounds in order to comprehensively investigate their effects on cycle characteristics. At the chosen values of the operating parameters, the enhancement achieved in the overall efficiency for the simple, reheat (with steam injection at high and low pressures) and partial oxidation (with steam injection at high and low pressures) gas turbine cycles are of about 20∼30%, 120∼200%, 10∼12%, 120∼260%, 20% respectively. The present modified cycles technique can be considered among the possible ways to improve the performance of gas turbine cycles-based power plants at feasible costs.