Humid air turbine cycle blade cooling exergetic analysis

Starting from the first steam injection cycles (GE-STIG; Cheng), the techni que of increasing gas turbine performances by injecting water/steam somewhe re before the combustion chamber, has shown very interesting results for po wer and efficiency increase and for NO, emissions. Very interesting perform ances are achieved by evaporative cycles, such as the HAT (Humid Air Turbin e), which is capable of achieving 50% conversion efficiency with lower inve stment costs compared to combined cycles. Other advantages of the steam inj ected cycle include the power modulation that is possible by varying the in jected steam flow rate, keeping the maximum temperature constant. In partic ular, for the HAT cycle, it is possible to choose different temperature, pr essure and compositions for the blade cooling fluid, depending on the bleed point. In this paper, a second law analysis of the HAT cycle and its compo nents, has been performed. In particular, the exergetic analysis of blade c ooling has been carefully analysed. Copyright (C) 1999 John Wiley & Sons, L td.