Journal of Engineering Sciences, Assiut University, Vol. 38, No. 5, pp.1181-1195, September 2010. 1181 SIMULATION OF GAS-STEAM TURBINE COMBINED CYCLE WITH WATER INJECTION AT COMPRESSOR INLET B. Saleh Mechanical Engineering Dept., Faculty of Engineering, Assiut University, Assiut, Egypt, bahaa_saleh69@yahoo.com (Received July 21, 2009 Accepted August 2, 2010) This investigation presents a computer simulation of gas-steam turbine combined cycle used in hot dry weather countries. Water is injected into compressor inlet air to alleviate the inlet air temperature and in turn improve the gas turbine output power and efficiency. The gas turbine simulation model is used following [1] and a standard Rankine steam cycle is employed in cascade with the gas turbine cycle. The turbine exhaust gases, instead of disposing to the ambient, are used in three heat exchangers arranged in series to provide all the required heat for steam cycle. The heat exchangers are simulated by the effectiveness-NTU method to obtain the off-design performance. The steam properties and the psychometric air properties are evaluated during the simulation by a linked computer code developed by the author. The results show that, the energy recovery in steam turbine produce power as much as one half of gas turbine output power. A combined efficiency in the range of 45% is reached at design points. KEYWORDS: Combined cycles, Power cycles, Gas turbine, Steam turbine, Heat recovery steam generator NOMENCLATURE Latin symbols A heat transfer area  m mass flow rate c specific heat 1 T  Inlet temperature difference C heat capacity rate 2 T  2 T  exit temperature difference q heat flux m T  Logarithmic mean temperature difference U overall heat transfer coefficient Acronyms CC combined cycle GT gas turbine CIT compressor inlet temperature ST steam turbine HRSG heat recovery steam generator TIT turbine inlet temperature -NTU effectiveness - number of transfer units