Effect of mist cooling technique on exergy and energy analysis of steam injected gas turbine cycle

Abstract

The common cogeneration application is steam injected gas turbine. By using cogeneration, it can be obtained with the greatest benefit from fuel energy. In steam injected gas turbine the heat of exhaust gases is used to produce the steam, and this steam injects to combustion chamber. In the present work, the generated steam not only will be directed to the combustion chamber but also will be used to cool the blade turbine by using a closed loop. In this study, the effect of addition mist to steam as coolant fluid was investigated. The energy and exergy analyses for steam injected gas turbine cycle with a closed loop cooling technique by using steam and steam/mist were investigated. The investigation was made at varied values of steam coolant temperature, mist fraction, mist temperature, pressure ratio, turbine inlet temperature and blade temperature. These parameters affected network, plant efficiency, energy ratio, fuel conversion ratio and exergy efficiency. The results show that the efficiency can reach 47.2% at low coolant temperature with a mist fraction of 2%. The coolant heat gain is enhanced at lower mist temperature, so the blade surface temperature can be improved with mist addition to steam. At a mist fraction of 2% exergy efficiency is decreased by 0.03% than that for exergy efficiency of steam only. (C) 2015 Elsevier Ltd. All rights reserved.