Performance Evaluation of Gas-Steam Combined Cycle Having Transpiration Cooled Gas Turbine

In recent years improved gas turbine performance through developments in high temperature materials and blade cooling methods has made a positive impact on the combined cycle performance. Transpiration cooling technique has emerged as the most promising technique to improve the gas turbine cycle performance by allowing higher turbine inlet temperatures. This paper concentrates on improving the combined cycle performance by allowing higher turbine inlet temperatures (TIT) using transpiration cooling of gas turbine blades. A four-stage advanced gas turbine coupled with the dual pressure steam bottoming cycle is considered for the performance of combined cycle. Realistic input parameters used in current industrial practice have been considered for this study. The effects of variation of TIT on the performances of topping, bottoming and combined cycle are presented and discussed. For the combined cycle with transpiration cooled gas turbine an increase in TIT from 1600 K to 1800 K exhibits the combined cycle efficiency increase by 2.37 percent and the combined specific work increases by 185.42 kJ/kg. The results indicate that at a TIT of 1800 K the achievable efficiency of combined cycle with transpiration cooled gas turbine is 59.97 percent.